• TABLE OF CONTENTS
HIDE
 Front Cover
 Abstracts of papers presented at...
 Sporulation in vitro of cercosporidium...
 Influence of rates of fertilizer...
 Identification of sources of resistance...
 Field evaluation of different fungicides...
 Effects of nematicides on nematode...
 Screening of tomato accessions...
 Development of inoculation technique...
 On-farm research on chemical control...
 Evaluation of seven fungicides...
 Note: An isolation technique for...
 Information for contributors
 Back Matter
 Back Cover














Group Title: Journal of Tropical Plant Pathology
Title: Journal of tropical plant pathology
ALL VOLUMES CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00090520/00024
 Material Information
Title: Journal of tropical plant pathology
Series Title: Journal of tropical plant pathology.
Alternate Title: Journal of Philippine phytopathology
Philippine phytopathology
Physical Description: v. : ill. (some col.) ; 26 cm.
Language: English
Creator: Philippine Phytopathological Society
Publisher: Philippine Phytopathological Society
Place of Publication: Philippines
College Laguna
Publication Date: January-June 1981
Frequency: semiannual
regular
 Subjects
Subject: Plant diseases -- Periodicals -- Philippines   ( lcsh )
Plants, Protection of -- Periodicals -- Philippines   ( lcsh )
Genre: periodical   ( marcgt )
 Notes
Dates or Sequential Designation: v. 1, no. 1 (January 1965)-
General Note: Title from cover.
General Note: "Official publication of the Tropical Plant Pathology."
 Record Information
Bibliographic ID: UF00090520
Volume ID: VID00024
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 54382605
issn - 0115-0804

Table of Contents
    Front Cover
        Front Cover 1
        Front Cover 2
    Abstracts of papers presented at the eighteenth annual meeting of the Philippine phytopathological society, UP at Los Baños, College, Laguna, 13-16 May, 1981
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
    Sporulation in vitro of cercosporidium personatum (Berk. and Curt.) deightan and cercospora arachidicola hori from peanut
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
    Influence of rates of fertilizer and lime application on the incidence of maize bacterial stalk rot caused by Erwinia carotovora Var. chrysanthemi
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
    Identification of sources of resistance to some major diseases or sorghum in the Philippines
        Page 40
        Page 41
        Page 42
        Page 43
        Page 44
        Page 45
        Page 46
        Page 47
        Page 48
    Field evaluation of different fungicides as seed treatment for the control of seed rot and damping-off dieseas of cotton cv. deltapine 16
        Page 49
        Page 50
        Page 51
        Page 52
        Page 53
        Page 54
        Page 55
        Page 56
        Page 57
        Page 58
    Effects of nematicides on nematode population and yield of potato in Atok, Benguet
        Page 59
        Page 60
    Screening of tomato accessions for bacterial wilt resistance
        Page 61
        Page 62
        Page 63
        Page 64
        Page 65
        Page 66
    Development of inoculation technique and varietal reaction to sheath rot of rice
        Page 67
        Page 68
        Page 69
        Page 70
        Page 71
        Page 72
        Page 73
    On-farm research on chemical control of some diseases of dryland crops grown before and after rice
        Page 74
        Page 75
        Page 76
        Page 77
        Page 78
        Page 79
        Page 80
        Page 81
        Page 82
        Page 83
        Page 84
        Page 85
        Page 86
    Evaluation of seven fungicides in the control of coconut leaf spots in the nursery stage
        Page 87
        Page 88
        Page 89
        Page 90
        Page 91
        Page 92
    Note: An isolation technique for the citrus-scab fungus
        Page 93
        Page 94
    Information for contributors
        Page 95
    Back Matter
        Page 96
    Back Cover
        Page 97
        Page 98
Full Text





I I I 1J


'hytopi


VOLUME 17 JANUARY and

CON

Abstracts of Papers Presented at the Ei
Philippine Phytopathological Socie
Laguna, 13-16 May 1981 ........

Sporulation In Vitro of Cercosporidiui
Deightan and Cercospora arachidic
Paningbatan and L. L. Ilag .......

Influence of Rates of Fertilizer and Lime
Maize Bacterial Stalk Rot Caused by
them F. D. Laysa and 0. R. Excor

Identification of Sources of Resistance to S
the Philippines S. C. Dalmacio, M.

Field Evaluation of Different Fungicides i
of Seed Rot and Damping-Off Disei
R. G. Davide and E. B. Batino ...

Effects of Nematicides on Nematode Pc
Atok, Benguet R. G. Davide and R

Screening of Tomato Accessions for Bactel
and M. 0. San Juan ...........

Development of Inoculation Technique an
of Rice C. A. Raju and R. A. Singh

On-Farm Research on Chemical Control o
Grown Before and After Rice F. A

Evaluation of Seven Fungicides in the Cor
Nursery Stage R. G. Abad.....

NOTE: An Isolation Technique for the C
--A1 A klnai __


Ithology



UNE 1981 NUMBERS 1 and 2

ENTS

iteenth Annual Meeting of the
F, UP at Los Bafios, College,
...................... 1-20

personatum (Berk. and Curt.)
a Hori from Peanut R. A.
...................... 21-29

Application on the Incidence of
Frwinia carotovora Var. chrysan-
e ..................... 30-37

me Major Diseases of Sorghum in
Dayan and C. B. Pascual ..... 38-46

Seed Treatment for the Control
es of Cotton Cv. Deltapine 16 -
.............. ........ 47-56

elation and Yield of Potato in
%. Zorilla ............... 57-62

I Wilt Resistance R. G. Atabug
...................... 63-66

Varietal Reaction to Sheath Rot
...................... 67-73

Some Diseases of Dryland Crops
Elazegui and T. W. Mew ...... 74-86

rol of Coconut Leaf Spots in the
...................... 87-92

rus-Scab Fungus J. M. Dangan


I










PHILIPPINE PHYTOPATHOLOGY


BOARD OF DIRI

LINA L. ILAG 0 Pr4
FAUSTO L. NUQUE 0 Vi
LINAC. LAPITAN 0 Se
FRANCISCO A. ELAZEGUI @ Tr
JOSE M. BANDONG 0 As
CONSTANTINO F. LUCERO E Ex
CEFERINO A. BANIQUED 0 Bc
ROMULO G. DAVIDE e Be
OFELIO R. EXCONDE 0 Be
DELFIN B. LAPIS e Be
TRICITA H. QUIMIO 0 Be
TIBURCIO T. REYES Be

EDITOR]

SAMUEL C. DALMACIO 1 Ec
DANTE A. BENIGNO 0 As
SAMUEL C. DALMACIO 0 As
ROMULO G. DAVIDE 0 As
GILG. DIVINAGRACIA 0 As
PONCIANO M. HALOS As
LINA L. ILAG 0 As
AGUSTIN N. PORDESIMO 0 As
TRICITAH. QUIMIO 0 As
SEBASTIAN S. QUINIONES As
AVELINO D. RAYMUNDO 0 As
CEFERINO A. BANIGUED 0 Bu

SUSTAINING

American Cyanamid Compan
Bayer Philippines, Inc., 622 Shaw
Canlubang Sugar Esti
Hijo Plantation, Inc.,'
Schering AG/Berlin, West Germany (Agrochemica
Makati, M
Union Carbide Philippines, Inc., P.O
Vi-torias Milling Co., Inc.



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institutions. Advertisements: Rates may be secu
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DPhtrnMthnlaimal nmai4r- T-t


rORS 1981-1982

lent
'resident
tary
arer
or
fwcio
(Member
[Member
IMember
IMember
IMember
!Member

. BOARD

r-in-Chief
late Editor for Virology
iate Editor for Disease Resistance
iate Editor for Nematology
iate Editor for Pathogenesis
iate Editor for Bacteriology
iate Editor for Post-Harvest Pathology
iate Editor for Disease Control
iate Editor for Mycology
late Editor for ForestPathology
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ess Manager

ASSOCIATES

?rinceton, New Jersey, USA
vd., Mandaluyong, Metro Manila
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um, Davao del Ncrte
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o Manila
ox 56, CCPO, Makati, Metro Manila
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dressed to the Treasurer, P. P. S. c/o Department
Philippine Phytopathology, published annually,
gical Society, Inc. It is sent free to members in
it is p25.00 per copy (domestic) and $12.50 per
Membership in the Philippine Phytopathological
ill be supplied by the Secretary upon request.
a charge some authors a present amount for each
abilities of their research projects or supporting
from the Business Manager. No endorsement of
i assumed by this Journal or by the Philippine











ABSTRACTS OF PAPERS PRESENTED AT THE EIGHTEENTH
ANNUAL MEETING OF THE PHILIPPINE PHYTOPATHOLOGICAL
SOCIETY, UP AT LOS BAROS, COLLEGE, LAGUNA, 13-16 MAY, 1981


Epidemiology of bacterial crown rot Etiology, seed detection and control
of papaya in the Philippines. F. B. Obrero of bakanae disease of rice. D. B. Lapis, A.
and A. J. Quimio (UPLB). M. Sinohin and M. T. Ecang (UPLB).

In areas with distinct wet and long dry Fusarium moniliforme produced more
season bacterial crown rot of papaya micro-and proconidia at 30 C than 25 C.
(caused by Erwinia caricae (Quimio and Six and nine-day old cultures had more
Obrero) occurs during the rainy season microconidia under complete darkness
only. Infected plants usually recover and than those exposed under continuous
produce productive branches during the artificial daylight (ADL) from a 20-watt
dry season. Under continuous rainy Philips daylight fluorescent lamp. The
conditions, however, infection progresses lowest spore count was under alterna;lng
until the plant dies. In controlled inocula- cycles of 12-hr near ultraviolet (NUV)
tion experiments in the field, disease light and 12-hr darkness using a 40-watt
incidence was positively correlated with Philips black lamp. Incubating seeds in
rainfall (r = .97). Disease occurred in agar and blotter tests under continuous


were ueiaycu as comparcu at temperature unmiecreu seeuungs making evajuauon or
of 19 to 34 C. Infection did not occur infection difficult. The highest seed
above 35. C. Caicae was not recovered infection of 27% by F. moniliforme was
from field soils 15 days after infestation, on blotter test without pretreatment,









Philippine Phytopathology


failed to completely eradicate F. moni- signmcant aavatanges over me uuuon
liforme. Benlate, Homai, Vitavax + row system planted to either whole o0
Captan and Vitaxas + Thiram all at sliced tubers in relation to the incidence
. .- .- t1, ....A O ...A. *-.at*r .n nf P infp.tans The incidence of late


were tungitoxic to f. monuiorme m
bioassay plate. Under growing-on test at
7.5% inoculum level they protected
nients effectively from bakanae. At 30%


UIllIAL Ul UG pjILoL aWvy IWJ -- 5V
influenced by plant density and tl
amount of nitrogen fertilizer applie


UlIAUiUIII I WI R vnly .. *~ b W.= -w- --- ED


Ivariel
ti-1 w
inocul
action
ties w
nocuhl
70%
natur;
2750
ffectih
> sigr
obtain
omyl
g a.i,
id 24.
wise,
ed am


applied
er signifi,
I kilos p
lay interv

dentifical
najor disc
nes. S. C
1. Pascual

Artificial
is were i
ive majoi
rust, gra)
t and Rh
portions i
of lines


ntervals
Daconil
applied a


ces of re
hum in t
M. P. Da;


inoculat:
en for re
sorghum
tar spot
ieath blip
lines to t]
as follow


seeds in Benomyl and Fungitox suspen- 27 out of 2525 for gray leaf spot, 51 ou
sion of 0.125 g a.i./kg seed/liter water for of 2268 for tar spot, 198 out of 2484 fo
24 hr remained effective even after target leaf spot and none out of 88 fc
using the same suspension four times. Rhizoctonia sheath blight. Resistance t
target spot was expressed as hypersensitiv
Integrated control of Phytophthor reaction while resistance to tar spot wa
infestans on potato. C. A. Baniqued, V. expressed as fewer number of stromati
G. Balaoing, J. Mariano, D. Roettger Hypersensitive reaction and/or fe,
and E. Verzola (BPI). i...i.... .i .....m. ....... nm..... a


Vol 11









Abstracts of Papers


Kealcons ot sugarcane clones ano
varieties to rust in the Philippines. C. S
Atienza and A. J. Quimio (UPLB).

Reactions of commercially grown ano
parental varieties of sugarcane to rus
caused by Puccinia kuehnii (Krueg.
Butler were studied at the Philippini
Sugar Commission, La Granja Agricultu
ral Research Center, La Carlota City
Under natural conditions, the commercial
varieties Phil 5333, Phil 56226 and Phi
58260 and the parental varieties CAC 57
60, Co 475, H 57-6466, CP 44-155, B 43


On-farm research on chemical control
of some diseases of dryland crops grow
before and after rice. F. A. Elazegui anc
T. W. Mew (IRRI).

The use of fungicides to control some
diseases of dryland crops grown before
and after rice has been assessed in farmers
fields at the outreach sites of the Crop-
ping Systems Program to evaluate the
economic feasibility of such disease con.
trol method for immediate adoption by
the farmers with small landholdings. Seed
treatment with Ridomil 25 WP at the









4 Philippine Phytopathology Vo. 17


the disease control and still obtaining while CMV was the most prevalent in
higher net returns. With the confirma- Abra. Where TLCV was observed, it was
tion of the effectiveness of thiophanate generally found in very few numbers.
methyl on the diseases, the farmers may TMV, CMV, and PVY isolates reacted
have an alternate in the fungicide to be positively to their specific antiserum in
used. double immuno-diffusion test. Further
test of PVY by ELISA against PVY anti-
Survey and identification of viruses serum also gave positive reaction. No
naturally infecting tobacco (Nicotiana TLCV antiserum is available yet, hence,
tabacum L.) in the Philippines. L. A. Re- no serological test conducted. Rigid and
vellame and D. A. Benigno (UPLB). flexous rod particles were observed from

Four viruses, namely: potato virus Y TMV and PVY isolates respectively using
(PVY), cucumber mosaic virus (CMV), leaf dip method of electron microcopy.
tobacco mosaic virus (TMV) and tobacco This method however, was not suitable
leaf curl virus (TLCV), were found to be in CMV nor in TLCV isolates. The pre-
naturally infecting tobacco in 8 tobacco- sence of PVY and CMV in tobacco are
growing provinces of Luzon. These were new records in this country.
identified through mechanical transmis-
sion, host range, symptomatology, sero- Etiology and symptomatology of two
logy and electron microscopy. TMV and peanut leafspots in the Philippines. R. A.
CMV were detected more frequently Paningbatan and L. L. Iag (UPLB).
in combination than as single infection.
Single and double infection of PVY with Brown spot of peanut caused by Cer-
any of the two were.almost equal, while cospora arachidicola Hori is reported to
TLCV rarely occurred in mixed infection occur for the first time in the Philippines.
Say o ree e eneti The disease is different from the common
with any of the three. Per cent relative black spot of peanut caused by Cercospo-
incidence of each virus in the samples
were: PVY (25%), CMV (18%), TMV ridium personatum (Berk. and Curt.)
w% CDeighton. Conidia of C. arachidiocola
(13%) and TLCV (5%) single infection. Deghton ona of.
In double infections PVY +CMV has the are filiform and have a distinctly truncate
In double infections, PVY + CMV has the
highest incidence (18%) followed by base and a subacute tip whereas those of
TMV + CMV and TMV + PVY both with C. personatum have an obconically trun-
S e C and tw T w cate base and a rounded tip. The conidia
9% incidence. Only two TMV and one
PVY isolates were detected from TLCV of the former are markedly thinner and
infected plants. PVY, CMV and TMV longer than the latter. The lesions caused
were found from all the provinces by C. amchidicola were generally brownish
surveyed except in Mindoro Occidental on the abaxial leaflet surfaces whereas
surveyed except in Mindoro Occidental









Jan. & June 1981


Some observations on sheath rot of of the bunchy-top virus. The abaca stra
rice. R. A. Singh and C. A. Raju (IRRI). of the bunchy-top virus was isolated fro
abaca specimens collected from Ba,
The causal agent of the disease was Oshiro, Davao City, and the Banana stra
first reported from Taiwan as Acrocy- was isolated from "Giant Cavendisi
lindrium oryzae Sawada, Gams and banana collected from the Twin Rive
Hawksworth (1975) created a new genus Research Center, Tagum, Davao del Norn
Sarocladium oryzae to accommodate the The abaca strain of the bunchy-top vir
pathogen. They also described S. atte- infected only abaca while the banai
nuatum causing the same disease from strain infected not only abaca but al
Indian collections. The disease was first banana. The banana strain was mo
reported from Southern India in 1974 as lethal and more infective than the aba
a minor disease but in a very short time it strain. On the other hand, the abaca stra
became prevalent in Northern India was observed to protect the plants fro
causing significant loss in yield. A loss of severe infection by the banana stra
6 to 30% in grain yield was assessed due virus. These two strains were found to 1
to disease depending on the variety and both efficiently transmitted by 2 forr
severity. Maximum disease developed of Pentalonia nigronervosa Coq., viz.,
when the minimum temperature ranged typical and f. caladii. Both forms transn
between 17 and 20 C and minimum re- these two strains in a persistent circulati
lative humidity between 40 and 56% manner. Electron microscope studies i
at flowering period. The maximum tem- crude sap and ultra-thin sections ofpla
perature, maximum relative humidity, tissues of bunchy-top infected abaca ai
rainfall and sunshine could not be correla- banana did not reveal any form of vil
ted with the severity of the disease. Of particle. Round objects quite similar


IllJUtA~ilc LIIg m pUIV UIb) uIISIUHIIu a1U plaJt
rment of pathogen grown on pearl mille
inside the boot leaf sheath 4-7 day
before flowering gave maximum disease
under field conditions. Five varieties
namely: Bas 370, Chinsurah Boro I]
Hom Thong, Sigadis and TKM 6 wer
found to be resistant to the disease usin
artificial inoculation.

Bunchy-top viruses on abaca an
banana in the Philippines. L. V. Magnay
and D. A. Benigno (BPI & UPLB).

Two related strains of the bunch)
top virus were distinguished on the basic
of symptoms, differential hosts, viru!
vector relationships and cross protection
These strains were arbitrarily identified
as the Abaca strain and the Banana strai


JJ.j'jrf'Ul. U *fif1VlJ11 ..JUL UU LJfUL J1V 11 VJH
banana. Likewise, cell organelles showe(
only ultra structural alterations, princi
pally the chloroplasts which contained
several lipid droplets and large accumula
tions of starch as well as numerous tu
bules in few cells near the trachieds
These could not be regarded as exclusive
to viral infection.

Bacterial crown rot of papaya in the
Philippines. A. J. Quimio and F. R
Obrero (UPLB).

Survey of bacterial crown rot of pa
paya in the Philippines showed that the
disease is widespread, destructive and ,
threat to papaya production in the coun
try. The diagnostic symptoms of the
diweae include leaf blight netiole rot









0r = VV -J 'u~vb'


G|Uu Iv.i ULJ R uI u w U5 -w f-) -0 n
-^;-*A ---.l4.:-j ;-* jlja^n~i -k* ann *<" hmUnw


brown v


causing vascular discoloration o mte nrougn transnuneu ugm. aeveram sputs
stem, fruits and roots. The causal bac- may coalesce covering large areas of the
terium was named Erwinia caricae n. sp. leaf and severely affected leaves fall-off
based on morphological, cultural and prematurely. The morphological, cultural,
biochemical characters. It is most close- physiological and biochemical characters
ly related to E. herbicola var. ananas of of the mulberry leaf spot bacterium were
the "herbicola" group of Erwinia. The similar to X. campestris (Pammel) Dow-
papaya crown rot bacterium (PCRB) son. The mulberry leaf spot bacterium
infects young and soft plant parts above however, was specific to mulberry. Due
ground. Inoculation tests showed that to its hosts specificity and similarity
it penetrated through natural openings in morphological, cultural, physiological
and wounds; histological studies of in- and biochemical characters to X. campes-
fected vascular tissues revealed that it tris (Pammel) Dowson it is named Xan-
invaded the xylem vessels resulting in thomonas campestris pv. mori n. comb.
extensive breakdown of surrounding The following mulberry clones: Ruso,
tissues. In lignified tissues of matured Echinose, Var. B and Echinose Improved
stem the bacterium was restricted to the were found to be resistant to the disease.
xylem vessels. Inoculations of injured
roots of papaya seedlings caused wilting Etiology of sugarcane rust in the
and the bacterium was isolated from the Philippines. C. S. Atienza and A. J.
toD portions of stems. Among 21 Phil- Quimio (UPLB)


cultivars, Philpack "Solo" 300, 316,
324, 295, 317 and 208, and canning
cultivars Philpack 1071 x 1061, 112 x
1096 and 1142 x 1122 were found re-
sistant in field screening test. Florida
lines 240 and 266, and Philpack "Solo"
302 were highly susceptible.

Bacterial leaf spot of mulberry (Mo-
rus alba L.). A. J. Quimio and R. T.
Lino (UPLB).

Bacterial leaf spot of mulberry (Morus
alba L.), a disease hitherto unreported
from the Philippines, was observed at the
Experimental Mulberry Plantation of the
Department of Horticulture UPLB, Col-
lege, Laguna. It causes pre-mature yel-
lowing and consequent defoliation of the
.affected trees. It is characterized by cir-


A survey U1 suga uanl ll u iU u
Philippines showed that it is a widely
distributed disease in the country. Two
species of Puccinia, namely, P. kuehnii
(Krueg). Butler and P. melanocephala
H. and P. Syd. were found causing the
disease. P. kuehnii was associated with
specimens collected from several Phil
varieties of sugarcane obtained from
Pampanga, Tarlac, Cebu, Leyte, Iloilo,
Capiz and Negros provinces and was
apparently the predominant species caus-
ing sugarcane rust in the Philippines.
P. melanocephala, on the other hand, was
found only on two Phil varieties from
Bukidnon province. Disease symptoms on
artificially-inoculated three-month old
commercial Phil varieties were formed
from the fourth leaf to the oldest
functional leaf. Dusting leaves, previously


0


- *---












wiped with dampened cotton, with ure
diospores was the most consistent and ef
fective method in reproducing the disease

Virulence of different morphovars ol
biovar III of Pseudomonas solanacearurr
to three solanaceous crops. A. J. Quimic
and Angela R. de la Cruz (UPLB).

Five morphovars of Biovar III of P.
solanacearum Race I had different viru.
lence patterns on eggplant cv. Black
Beauty, tomato cv. Yellow Plum, and
pepper cv. California Wonder. The most
virulent morphovar on pepper and toma-
to ranked only third on eggplant while
the most virulent to the latter ranked
third on tomato and second to pepper.
One morphovar was not virulent tc
pepper while it ranked fourth both or
eggplant and tomato. Infectivity titra
tion using one-week-old tomato seedling,
of wilt resistant cv. Marikit and wilt sus
ceptible cv. Yellow Plum showed that the
most virulent morphovar required signifi.
cantly lower concentration of inoculurr
to cause 50% (ED50) mortality on inocu.
lated seedlings, compared with those
of the less virulent morphovars. The
pattern of virulence of the morphoval
were consistent in both susceptible and
resistant plants. However, lower con
centration of inoculum of less virulent
morphovars capable of causing wiltin
of the susceptible plants did not initiate
the disease on resistant plants. The data
indicated significant variations of patho
genic potentials of morphovars of Biovai
III ofP. solanacearum Race 1.

Subspecific classification of Pseudo
monas solanacearum in the Philippine!
C. K. Alagad, Jr. and A. J. Quimic
(UPLB).

An electronic computer technique


utilizing the principle of numerical taxo
nomy, that every feature should have
equal weight, was applied in an effort tc
derive a classification of subspecific
level of P. solanacearum in the Philip
pines. Sixty-eight isolates from eleven
host plants and thirty provinces, be
longing to four biovars according tc
Hayward's classification were charac
terized using colony, nutritional, and
biochemical traits. Grouping of the iso
lates by centroid sorting of cluster analy.
sis of 73 features from studies of colony
morphology, resistance to streptomycin
and oleandomycin, nutritional and bio
chemical characters showed that five pa
rent clusters could be recognized frorr
the fusion level where the similarity
coefficient was equal to 0.476. The data
indicated that Biovars I and III could be
divided into two different groups each
Biovar II was a distinct and separate
group, and Biovar IV could be fused witt
one of the two groups of Biovar III.

Phenotypic variation of Pseudomonas
solanacearum in the Philippines. C. K
Alagad, Jr. and A. J. Quimio (UPLB).

Sixty-eight isolates from eleven host
plants and thirty provinces, belonging tc
four biovars according to Haywards's
classification were characterized using co-
lony, nutritional, and biochemical traits.
The replica plating technique was used
to test the organisms for growth on 27
carbon sources. Based on the nutritional
spectrum, Biovar IV was the most homo
generous showing consistency in reaction
for 25 out of 27 tests. Biovar III was nol
homogenous as Biovar IV but less hetero
generous than Biovar II. Biovar I was the
most heterogeneous exhibiting consistent
cy in reaction for only 14 out of 27 nutri
tional parameters. Biovar III was most
related to Biovar IV, having ten nutri









Philippine Phytopathology


tional characters in common; these traits
were the ability to grow on mannitol,
sorbitol, dulcitol, inositol, galactose,
trehalose, ribose, ketogluconate, phyeny-
lalanine and failure to utilize malonate.
Biovar I had affinity with Biovar II
through its inability to grow on manni-
tol, sorbitol, dulcitol, m-tartrate, glycol-
late, valerate and sarcosine. Variable
reactions were obtained for nearly all the
biochemical tests except for the consis-
tent negative reactions exhibited by Bio-
var I on denitrification and 2-ketogluco-
nate tests, positive reaction by Biovar II
and IV on lipase test and tolerance of
Biovar II on 1.7 percent NaCl. All iso-
lates grew at 1.0 and 1.4 percent NaC1
medium. Denitrification, lipase, 2-keto-
gluconate formation and phosphates
tests were found useful in dividing the
biovars into several subtypes.

Homogeneity and heterogeneity of
Xanthomonas campestris pv. oryzae
strains virulent to rice differing in resis-
tance. C. M. Vera Cruz and T. W. Mew
(IRRI).

A study was undertaken to analyze the
variation on lesson caused by isolates of
different races ofX campestris pv. oryzae
on IR8, IR20 and IR1545. Variance of
isolates originating from lesions of IR22
and IET4832 indicated significant differ-
ences. The lesion length that each indi-
vidual isolate caused on IR8, however,
was not significant. Variance of sub-
cultures either from PX061 and PX080
or from PX079 on susceptible varieties
IR8 and IR20, respectively, showed si-
milar variation. The lesions caused by
each subculture on the respective suscep-
tible varieties were more variable than the
sub-cultures of each strain. There was
a significant difference in lesion length
incited by isolates on IR8, IR20 and


IR1545, indicating interaction between
varies and isolates. A very high co-
efficient of variation (398.2%) on cul-
tivars was noted as they differed in
resistance to the bacterium. Further
analysis of the three varieties revealed
that majority of the isolates were homo-
geneous on IR8, a cultivar with no
functional gene known for resistance to
bacterial blight in the Philippines and
some of them appeared more variable
in virulence. On IR20 and IR1545, there
seemed to be unrelated groups of pv.
oryzae isolates variable in virulence to
the two varieties. On the other hand,
the isolates were heterogeneous on
IR20. The group of isolates which were
less virulent to IR20 were more homo-
geneous than those which were virulent.
However, those which were more virulent
to IR20 were heterogeneous and more
variable. Whether or not the variability
of the different isolates was related to the
nature of the resistance of IR20 or the
virulence of the isolates themselves to
cause such variation in. lesions is under
study.

Physiologic race study of Cercospora
oryzae. B. A. Estrada, L. M. Sanchez, F.
L. Nuque and J. P. Crill (IRRI).

Eight rice cultivars (IR8, Zenith,
IR20, Delitus, IR26, Southern Red Rice,
IR9129-159-3-2-3-3 and MI 273) which
were selected out of a few hundred varie-
ties and lines in earlier studies were used
as differential varieties to differentiate
physiologic races of Cercospora oryzae.
Sixty isolates (from monosporial culture)
were inoculated individually to the set
of differential varieties 21 days after
seeding with evaluation of disease reac-
tions done three weeks after inocula-
tion. Out of the 60 test isolates, 19 races
distributed in six race groups were differ-


Vol. 17









ADtm cts or rapers


entiated. The most important physiolo- FI-1 includes 31 isolates. Race FA-1 in-
gical races belonged predominantly to fected all the 20 varieties except IR45 and
newly designated C. oryzae race groups IR9763-11-2-2 which are resistant and
CA and CC, with 43.3 and 40.0% res- moderately resistant, respectively. The vi-
pectively. Within these two physiologic rulence index (VI) of the isolates be-
race groups, 20.0 and 18.0% of the iso- longing to race FA-I indicated that the
lates exhibited pathogenicity patterns on isolates had a mean VI of 6.9. All the va-
the rice differentials typical of races CA- rieties were resistant to race FI-1 which
95 and CC-31, respectively. The remain- had a VI of 1 suggesting that race FI-1
ing isolates belonged to other less pre- is non pathogenic.
dominant races, such as CA-21, CA-31,
CA-85, CA-87, CA-88, CA-127, CA-128, Inheritance of resistance to target leaf
CC-21, CC-22, CC-24, CC-29, CE-5, CE-7, spot in sorghum. C. B. Pascual and S. C.
CG-1, CH-1, and CI-1. Identification by Dalmacio (UPLB).
letter and numbering of races were based
on Ling and Ou's "Standardization of the A male-sterile sorghum line (Cosor 1A)
International Race Numbers ofPyricula- which is susceptible to target leaf spot,
ria oryzae", using pre-designated patho- caused by Helminthosporium sorghicola,
genicity patterns of all races and a dicho- was crossed to a number of resistance
tomous arrangement of susceptible and sources. F-, and F2 populations were de-


MaL & June I .1









'u


isolates of the fungus even 4 weeks after Where successful invasion occurred, gian
seeding. The rest of the varieties showed cells were formed, however, necrosi
susceptibility to the isolates. Wilting was always observed.
symptom was common in susceptible
varieties under high inoculum of the Influence of nitrogen and silicon oi
fungus, while node elongation symp- the development of Helminthosporiun
tom was commonly found on susceptible brown spot of rice. J. P. Jones, F. L. Nu
varieties under low inoculum density of que and J. P. Crill (IRRI).
the fungus and resistant varieties under
high inoculum density. Formation of Solution culture techniques were use,
adventitious roots and stunting were ob- to determined the effects of nitrogen
served occasionally during the experiment. (N) source (80% NH4:20% NO3, 20
NH4 80% NO3), N rate (20, 60, 12
Responses of resistant and susceptible ppm), and silicon (Si) rate (0, 10, 20 ppnr
sweet potato cultivars to Meloidogyne on the incidence and severity of brow
incognita. R. M. Gapasin (VISCA). spot of rice incited by Helminthosporiur
oryzae Breda de Haan. The basal solution
The responses of "Jewel" and "Cen- consisted of 16 ppm P, 60 ppm K, 3
tennial" sweet potato varieties were inves- ppm Ca, 16 ppm Mg, and micronutrient:
tigated under greenhouse condition. Root- N was derived primarily from (NH4)2SO
gall and egg-mass indices and numbers of or NaNO3 and Si from NaSi025H20. S
eggs per root system were low in resistant rates of 30 and 60 ppm were used th
"Jewel". However, root growth suppres- first week of growth, no Si was used th


ces (P = 0.5) in root weight over the con
trol. Fresh root and top weight of suscep
tible "Centennial" increased with decrease
ing nematode population 36 days afte
inoculation Nematode population in
creased with increasing population. Gal
and egg mass indices were significantly
different (P = .01) over the susceptible
control. Histopathological studies showed
the formation of multinucleated, thick
walled and granulated giant cells in sus
ceptible "Centennial". Nematodes wer
observed in the cortex and abnorma
xylem cells were found around gian
cells. Hyperplasia and hypertrophy wer
also observed around the cells of the ne
matode and giant cells. The formation o
periderm and lignification of adjacent
cells around the nematode were founi
in resistant "Jewel". Necrotic cells anw
"t-k ..a,'" n-n-- ^ ll --- ,a n ,I- '1 ..rl


were applied the following week and the
increased to 10 and 20 ppm. Solutior
composed of 80% NO3 and sodium sil
cate were adjusted to pH 6.5 with 1 1
HCL. All solutions were changed twic
weekly. IR 4568 seed were germinate
in Petri dishes and after 5 days placed o
screens floating on nutrient solutions i
23x30x15 cm plastic trays. Five week
after seeding, plants were inoculate
with 1,800 spores per cm2 leaf tissue
incubated 24 hours in dew chamber
then placed in a shaped greenhouse wit
humidifiers for 4 days until symptoms di
veloped. The number of lesions increase
as the N rate increased (6.3, 23.1, 27.
lesions/plant for 20, 60, 120 ppm-N, re
pectively). In general, Si decreased d
sease occurrence (30, 13, 14 lesions/plar
for 0, 10, 20 ppm-Si, respectively). Hov
ever, Si, if combined with 60 ppm NHA-1








A 1UcuaU or rap=e


did not reduce disease incidence. In the
absence of Si, N03-N encouraged lesion
development more than NH4-N.

Studies on the comparative effects of
nitrogen and potassium nutrition on
sheath blight disease development. S.
Kannaiyan and H. E. Kauffman (IRRI).

The effect of nitrogen and potas-
sium on the development of sheath
blight was investigated in pot culture
experiments during the wet season
'June-September) with ADT-31 as the
susceptible rice variety. Two separate
pot experiments were conducted to study
the influence of nitrogen and potassium
it different levels. The nitrogen levels of
), 49, 99, 148, 198 and 247 kg N/ha
iere calculated and applied with Urea.
At all N levels 62 kg P/ha as superphos-
,hate and 62 kg K/ha as muriate of po-
l. ,-_ .-I.:- U-1ir _r *U- 1T -.-- --


increase in yield. Investigation reveals
that potash nutrition gives rice some
resistance to sheath blight.

Effects of temperature on bacterial
blight development. 0. Horino, R. C. Re-
yes and T. W. Mew (IRRI).

In controlled environmental condi-
tions where the relative humidity was set
at 70%, bacterial blight lesion develop-
ment increased when the temperatures in-
creased. IR8, which has no functional
gene for resistance to bacterial blight in
the Philippines, showed increased lesion
size from 10 cm to 45 cm at a diurnal/
nocturnal temperatures of 20/17 to
35/27C in response to two virulent
strains of Xanthomonas campestris pv.
oryzae, PX061 and PX071. Kinmaze,
Kogyoku and Cas 209, the rice varieties
susceptible to the two strains, showed a


the disease incidence significantly. As the
potash levels increased the disease inci-
lence decreased with a corresponding


IlL & JUMe iysI









--I, - -, -u.---


AUn LACUUIUAJ7 D UWID uavj JU.kA -
Thanatephorus cucumeris in relation t(
its saprophytic survival. A. M. Rosale;
and T. W. Mew (IRRI).

Cellulolysis adequacy index (CAI) i
the ratio of the speed of filter pape:
cellulose decomposition to the daily li
near growth rate of a fungus. It is a mea
sure of the saprophytic survival ability
of the fungus in the absence of supple
mentary nitrogen. Initially, CAI of Tri
choderma sp. was compared with 7
cucumeris. The CAI for three isolate
of T. cucumeris was less than 1, indicate
ing that exogenous nitrogen was essential
to attain better saprophytic survival
Trichoderma sp. had the highest CA
both with cellulose (3.01) and rice stray
(3.40) as substrates. In the present study
CAI was employed to compare rice strav
decomposition in soil to the saprophyti
survival of T. cucumeris, the rice sheat]
blight pathogen, either in the presence o
absence of a Trichoderma sp., isolated
from field of upland rice. Both T. cucu
meris and Trichoderma sp. decomposed
rice straw. The rate was the highest whei
the rice straw was infested with Tricho
derma sp. When the rice straw was in
fested by a mixture of T. cucumeris an,
the Trichoderma sp., the survival of th
former was affected. Two weeks after ir
cubation, recovery of T. cucumeris fror
the buried rice straw in soil was 18.79
and became undetectable in 14 weeks i
the presence of Trichoderma. In the at
sence of Trichoderma recovery of 7
cucumeris from rice straw was 96% in 1
weeks and 75% 16 weeks after incubi
tion.


- ----r -- -- -- - -
on the growth and yield of sweet potato.
C. de la Cruz, R. L. Loreto and M. K.
Palomar (VISCA).

Sweet potato leaves inoculated at dif
ferent ages with Cercospora batatae
showed varying responses to infection
with significant differences in the number
of lesions, size of lesions and percentages
of defoliation. Leaves inoculated at 15 tc
21 days old were found most susceptibk
to the disease. Initial symptom of th(
disease was first observed as light greer
lesions approximately 0.5 mm in diame
ter two weeks after inoculation. The le
sions increased gradually until the)
reached 3 to 4.22 mm diameter 32 day:
after inoculation. Coalescence of lesion:
was observed at this stage followed b3
subsequent defoliation. Inoculated plant:
showed decrease in yield and yield com
ponents. The two trials revealed 9.57%
5.05% and 26.23% reduction in weigh
of tubers, roots and tops, respectively
The number of tubers decreased also ii
inoculated plants. Analysis of variance o
weight of tops showed significant differ
ence from the uninoculated ones whill
the other parameters were not significant


Yield loss in soybean infected by Xan
thomonas campestris pv. phaseoli at dif
ferent stages of growth. A. J. Quimio an(
S. Vichitrananda (UPLB).

Yield losses of soybean cultivars, TK-5
CES-434, L-114, and Clark-63, inocula
ted with Xanthomonas campestris pv
phaseoli at different stages of growth
were studied. Results showed that in al
varieties, seed weight, volume, protein
content and fat content, and per cen
seed germination were reduced at all sta
ges of inoculation, namely at 15 day


~--~-









Abstracts of Paper


trore nowering, flowering, pod torma- seed weight loss ranged from 35.7 to
on, and mature pod stages. The highest 49.6 per cent; reduction in seed fat
:duction in the parameters mentioned content from 2.9 to 8.1 per cent; and re-
ere observed in plants inoculated at the duction in per cent germination from 4.2
lowering stage. However, no significant to 12.5 per cent. Differences in these
fferences in the parameters were ob- parameters between disease intensities
rved between and among the first varied with the cultivars. It was noted
tree stages of inoculation regardless of that TK-5, CES-434 and L-114, and
te variety. Compared to the control, for Clark 63 which have been classified bac-
1 varieties, per cent reduction in seed trial pustule susceptible, moderately
eight, ranged from 30.7 to 38.4; seed resistant, and resistant cultivars, res-
)lume, 29.2 to 40.8; seed protein con- pectively, generally suffered the same le-
nt, 9.3 to 11.0; seed fat content, 6.1 to vel of quantitative and qualitative losses
4; seed germination, 6.7 to 10.4%. at different bacterial pustule intensities.
here were no significant differences in It was also concluded that quantitative
Lese parameters between varieties at the and qualitative yield losses of soybean
me stages of inoculation. The number would increase with increasing bacterial
Spods and seeds per plant varied within pustule intensity.
ie variety but mostly reduced in plants
oculated at the flowering stage. It was Study on the yield loss in rice due to
)ted that TK-5. CES-434 and L-114. bakanae disease. F. L. Nuque. J. M.


, any 00 a fUa LbIJ1W J Uta UI-;Ua, LIU b,
moderately resistant, and-resistant culti-
ars respectively, had the same degree of
isceptibility to bacterial pustule. It was
[so concluded that soybean would suffer
severe quantitative and qualitative losses
hen affected by bacterial pustule.

The relation of bacterial pustule
itensity to soybean yield loss. A. J.
i_ J_ J d r k .... -- /0inT W,\


Pot experiment was conducted in the
eenhouse to obtain information on
sath of infected seedlings, recovery of
edlings from the disease and yield loss
'rice due to bakanae disease at different
sease incidence ranging from 10 to
)0%. Percentage death of seedlings in-
eased from 10 to 80% infection but de-
eased at 90 to 100% infection. How-
Ar nMt ll hal[-na, infotr*Pfl eafllinat


The reduction in seed weight, of TK- from the disease and produced apparent-
,CES-434, L-114 and Clark 63 soybean ly normal grains. Seedling recovery in-
iltivars increased with increasing bacte- creased from 10 to 100% disease inci-
al pustule (caused by Xanthomonas dence. Losses in grain weight were from
impestris pv. phaseoli) intensity (no. of 2.3 to 9.1, 5.1 to 11.8 and 2;7 to 9.5%
)ots/leaf). The linear regression of seed based on yield of plants grown from Ben-
,eight on disease intensity were statis- late-treated seeds only, on yield of plants
cally significant with the average reduc- grown from Benlate-treated seeds and
on in seed weight for each unit increase sprayed with Benlate weekly up to matu-
i disease intensity ranging from .018 to rity and on yield of plants grown from
)66. Compared to the control, of all Benlate-treated seeds and sprayed with
iltivars and at all disease intensities, Homai weekly up to maturity, respective-


m. a June 1981








ninuppme rnytopauoiog.


ly. Actual losses in yield varied from 2.8
to 32.9 18.4 to 43.7 and 18.4 to 43.6
per cent in the above-mentioned treat-
ments. The correlation coefficients (Y)
between disease incidence and percentage
actual yield loss were 0.9681, 0.9597,
and .9606, respectively. Results also sug-
gested that although infected plants re-
cover from bakanae and produce grains
the weight of the harvested grains are
lighter than grains from healthy plants.

Effect of nitrogen and temperature on
leaf scald (Rhynchosporium oryzae) dev
elopment. E. Andrade, J. P. Jones and
J. P. Crill (IRRI).

The effect of nitrogen and tempera
ture on the development of the leaf scalc
disease of rice (Rhynchosporium oryaze'
was studied in IR36 (Susceptible) an(
Melot (Resistant) varieties grown in cul
ture solution. Four nitrogen concentra
tions (20, 60, 100, 140 ppm) and there<
temperatures (20, 25, 30C) were used
This study was conducted using 3SL cabi
net of the Phytotron (IRRI). Leaf scalc
lesions were well developed in higher ni
trogen level (140 ppm) and at lowe
temperature (20C) in both the suscep
tible and resistant varieties. However, the
resistant (Melot) variety developed short
er lesions than the susceptible one.

Detection of bakanae-infested seed
and the effect of benomyl sprays on ai
tificially infested seeds in the field. J. M
Bandong, T. Vergel de Dios, M. C. Rusl
and J. P. Crill (IRRI).

IR42 seeds obtained from bakanae
infected field and soaked in water for 11
hr before seeding gave more bakanae
infected seedlings with abnormal elonga
tion symptoms than the unsoaked direct
seeded seeds. Using Komada's medium


for detecting seed infestation, seeds
harvested from bakanae-infected IR42
field plots and artificially-inoculated 3
times at flowering stage showed 18.0%
infestations compared with only 2.6% in.
festation of seeds harvested from similar
but uninoculated field plots. Seeds har-
vested from Benomyl-sprayed (2 weekly
sprays before inoculation) plants before
3 artificial inoculations at flowering stage
had 11.8% infested seeds compared with
similarly inoculated plants but without
Benomyl sprays which had 16.3% infes-
ted seeds. Highest percentage of seed in
festation of 19.8% was obtained front
plots inoculated 3 times followed by '
weekly Benomyl sprays after inoculation

Soaking treatments of bakanae-infested
seeds with systemic fungicides for baka
nae control. J. M. Bandong and J. P
Crill (IRRI).

Benomyl-thiram (40% W.P.), Thiopha
nate-methyl-thiram (80% W.P.) and Thio
phanate-methyl each tested at two con
centrations of 2.0 and 1.0 g formulatior
per liter suspension as pre-sproutinj
treatments for 24 hrs. gave effective baka
nae control on naturally-infested IR4C
seeds. This confirmed earlier reports ol
their effectiveness for bakanae control
Results also showed that higher con
centration (2.0 g/1) of each fungicide
resulted in better and more effective
bakanae control than lower concentra
tions (1.0 and 0.5 g/l).
Furthermore, chemical suspension
used a week later, remained as effective
as when it was first used.


VO. i









Abstracts of Papers


Pre-sprouting treatment of IR44-2-58
seeds with systemic fungicide suspen,
sions for leaf blast control. J. M. Ban
dong and J. P. Crill (IRRI).

Soaking the seeds of a blast-susceptible
variety for 24 hrs. in CGA49104 (509M
WP) at concentrations of 1.0, 2.0 and
4.0 g formulation per liter suspension:
gave excellent control of leaf blast or
dapog-raised seedlings grown from the
treated seeds until 19 days after seeding
The dapog seedlings grown from the
treated seeds with 2.0- and 1.0 g con
centrations exhibited initial infection
26 days after seeding, while those treated
with 4.0-g concentration showed very
slight infection at 47 until 54 days aftei
seeding. Seedlings grown from the 1.0-g
concentration treatment and transplanted
6 days after seeding started showing very
slight infection at 19 days after seeding
while those from the 2.0 and 4.0-g con.
centrations exhibited initial infection 26
days after seeding. Leaf blast control with
CGA49104 was more effective on dapoE
seedlings than on transplanted seedlings
although the effects of the chemical treat-
ments were still apparent until 54 days
after seeding in both dapog and trans-
planted seedlings.

Pre-sprouting treatment of naturally-
infested seeds and foliar sprays with be-
nomyl 50 WP for bakanae control. J.
M. Bandong, M. C. Rush, T. Vergel de
Dios, F. L. Nuque and J. P. Crill (IRRI).

A study was conducted to determine
the effect of Benomyl on Bakanae in-
fection, yield of dapog raised, trans-
planted rice and seed infestation in the
field using IR40 and IR42. Seeds were
soaked in Benomyl suspension (2 g for-
mulation per liter of water) and pre-
sprouted for 48 hrs. before seeding in


dapog beds. Seedling were then trans-
planted in the field where some plots re-
ceived Benomyl sprays (1 kg formulation
per ha) twice. Infected tillers from Beno-
myl-treated seeds was less than 1% for
both IR40 and IR42 as compared to
12-18% and 21-29% for untreated seeds
of IR40 and IR42, respectively. Infected
hills ranged from .01-.02% and .02-.13%
for treated seeds as compared to .47-.63%
and .87-1.05% for untreated seeds of
IR40 and IR42, respectively. Seed treat-
ment plus Benomyl sprays increased yield
of IR40 and IR42 by .62 and .89 T/ha.
respectively, when compared to untreated
seeds but sprayed plots while seed treat-
ment alone increased yield of IR40 and
IR42 by .85 and .82 T/ha, respectively,
when compared to untreated and un-
sprayed plots. Seed infestations from har-
vested seeds of IR40 were 2-3% from
treated seeds and more than 12% for un-
treated seeds, sprayed or unsprayed.
Seed infestations on IR42 were 8-9% for
treated seeds, whether sprayed or un-
sprayed, 13% for untreated seeds but
sprayed plots and 16% for untreated
and unsprayed plots. It was also de-
monstrated that Benomyl suspension
previously used for seed treatment re-
mained effective in controlling Bakanae
when used again a week later.

Disease of main crop of rice in rela-
tion to ratoon rice Effect of chemical
control. N. G. Fabellar and T. W. Mew
(IRRI).

During the wet season of 1980, two
separate experiments were conducted on
the effect of fungicide application on the
main crop in relation to diseases of ra-
toon rice. In the first experiment using
IR32, benomyl-thiram was applied as
seed treatment at 1 g/kg seed and sprayed
during the maximum and filling stage at 1


I1









SFilipphin Phytopa~iaol g


liter. Eight treatments were made and
plicated 5 times in a randomized com-
lete block design with 4 m x 3 m plot
er treatment. IR50 was used in the
their experiment where benomyl-thiram
t 1 gm/liter was sprayed at booting and
lling stage. Two treatments were made
id replicated 4 times in RCB design.
disease was rated at maturity of 20 hills
er treatment for stem rot and 72 hills
er treatment for sheath blight using 1-5
nd 0-9 scale, respectively. Rice stubbles
'ere cut approximately at 15 cm from
te base as the recommended cutting
right. Disease rating on ratoon was done
5 days after ratooning based on 4 spots
ith 3 hills per spot per treatment. Yield
ata for both the main and ratoon crops
as taken from an area of 5 m2. Treated
plants showed lower disease incidence
id severity than untreated plants. The
itooning ability was improved on treat-
I over untreated and the mean number
f tiller per hill was also higher than the
treated. The lodging of ratoon tillers and
em rot incidence was high on untreated
iain crop thus contributing to a lower
field than the treated. Yellow dwarf was
observed on the ratoon crop but not on
ie main crop. Although the incidence
F sheath blight was lower than that of
em rot, the trend of the disease on the
lain and ratoon crop was comparable
r increased. Other major diseases to
which IR32 was resistant were not noted
1 the ratoon rice.

Studies on the chemical control of
leath blight diseases of rice. S. Kannai-
an and H. E. Kauffman (IRRI).

The rice variety ADT-31, which is
isceptible to sheath blight caused by
hizoctonia solani (Kuhn was grown in
,ncrete pots during wet season (June-
eptember). At maximum tillering stage


ie plants were inoculated with the patho-
mn by strawbit method. The test fungi-
des Bavistin, Kitazin, Hinosan, Benlate,
emosan, Thiabendazole, Vitavax, Daco-
il, Brassicol and Wettable Ceresan were
sed at 0.05, 0.1 and 0.2% levels. They
ere sprayed once at 12 hours after ino-
ilation. The disease intensity was assessed
sing the 1976 Standard Evaluation Sys-
!m for Rice scale. Compared with the
treated control, all the fungicides effec-
vely controlled the disease. Bavistin,
itazin, Hinosan, Banlate, Demosan and
hiabendazole gave significant disease
control. An increase in spray concentra-
n of all fungicides lowered the disease
Idex.

Leaf blast control with granular sys-
mic fungicides. J. M. Bandong, C. Q.


ulics ilU J. I. r. u111 ir

Granular systemic fui
:d for leaf blast cont
ient either just before
:eding time. The soil t
laced either in plastic
prepared for planting i
,ry plots.
The results showed
wrmulation of CGA491
Sites of 60 and 30 kg
ictare was effective. L
nged from 95 to 100W
3 to 100% control (3
ate (8% G), Kitazin (
ied at the rates of 60
aji-One (12% G) at 4(
lowed slight to highly
f leaf blast control. TI
application of these fu
nerally better leaf bl
te lower ones. Very ef
mntrols were also obta
)0- and 50-kg formula
tes of (Gr A4QIaln a


I LreaL-
r after
ed was
ays or
it nur-

ranular
at the
on per


(60 kg/ha) and
i kg/ha). Oryze-
7% G) each ap-
id 30 kg/ha and
and 20-kg rates
effective degrees
higher rates of
gicides showed
it control than
-ctive leaf blast
led from 600-,
ion per hectare
liffoarAnt nitrm


6








A 1L- E


gen fertilizer levels ranging from 120 to followed by Temik 15G, Furadan 3G,
480 kg N/ha. Blast infection increased and the other 3 rates of Mocap 5G, res-
with increasing nitrogen levels and was pectively.
highest at the highest N-level.
Field evaluation of different fungicides
Evaluation of three nematicides for as seed treatment for the control of seed
the control of nematodes affecting po- rot and damping-off diseases of cotton cv.
tato in Atok, Benguet. R. G. Davide and Deltapine 16. R. G. Davide and E. B.
R. A. Zorilla (UPLB). Batino (UPLB).

Two experiments using a randomized Seven fungicides were evaluated as
block design with four replications were seed treatment for the control of seed
conducted in the potato farm of Mr. rot and damping-off diseases of cotton
Romy Ong, during the 1980-1981 crop- cv. Deltapine 16. All treated and non-
ping seasons. The nematicides tested treated seeds were subjected to "flood
were Mocap SG at 4, 6, 8 and 10 kg a.iJ test" by submerging them in water for
ha, Temik 15G at 7.5 and Furadan 3G at 5 days in plastic tumblers before planting
4.5 kg a.i./ha. Each treatment replicate in the field. All the fungicides tested
utilized a I x 4 meter plot. Each chemical showed significant increase in grmi-
was separately applied into a 3-inch-deep nation, stand and yield of cotton plants.
furrow between rows of newly planted Percentage increase in stand at harvest
potato using varieties Jaerlan and Fina ranges from 4.5 to 683% while the yield
for the first and second experiments, res- increase ranges from 20.9 to 68.9% as
pectively. A non-treated plot was provided compared with the control. In terms of
in each block to serve as control. There- yield, the best treatments were Vitavax-
after, the farmer-cooperator applied the Thiram and Zincofol which gave 68.9 and
usual cultural practices for the produce. 68.0% yield increase. These were
tion of potato in the area which includes followed by treatments of Vitavax-
adequate fertilization and control of pests Captan, Homai, Captan, Brassicol and
and diseases. To monitor the nematode Difolatan.
population build up, soil samples (400
cc) were taken from each replicate plot Gulf orchard spray al-70 for the
before and after treatments and subse- control of Sigatoka, black leaf streak
quent samplings were made monthly and banan freckle diseases. M. O. San
until harvest time. Nematodes such as Juan (TRRC).
Pratylenchu sp., 7ichodorus sp., Tyle-
nchorhynchus sp. and Rotylenchulzu Gulf Orchard Spray-Ofl-70 was ox-
sp were found associated with potato perimentally tested side by side with
in the area. All nematicide treatments Shell Banana Spray Oil to find out their
significantly reduced the nematode popu- efficacies in the control of sigatoka, black
lation. The treatments resulted in signi- leaf streak and freckles. Equal quantities
ficant increase in yield ranging from of Dithane M-45, Benlate 50 WP, Triton
11.6% to 33% in the first trial and 22.69% X-45 and water were each mixed with the
to 67.69% in the second trial. The highest spray oils. Both the experimental and
increase in yield (67.69%) was obtained control treatments were aerially applied
I u r, .4 i-- 1UL**. -1t4a -4f r M-*













Cavendish bananas at 10 to 14 days in- differ in providing control of the foliage
terval during the 12-month experiment diseases when compared to the control
period, given by the Dithane-Banlate treatment.
Results obtained from plants treated
with the Gulf Orchard Spray Oil were Effect on Polyoxin AL S.P. alternated
slightly, but not significantly better than or mixed with Dithane M-45 with banana
the control. Leaf spot development was spray oil and Triton X-45 in Sigatoka and
slower on the experimental plants, con- black leaf streak control.
sequently there were more functional M. 0. San Juan (TRRC).
leaves than those on the control. No sta-
tistical differences were also noted be- Polyoxin AL S.P. was used as the
tween the oil treatments on the incidence experimental fungicide in a field exper-
levels of the banana freckle disease. iment on Giant Cavendish banana to
control sigatoka and black leaf streak
Effects of two concentrations of low diseases. The Polyoxin-oil-Triton water
volume sprays of Topsin M ULV on mixture alternated with another mix-
the control of Sigatoka and black leaf ture of Dithane-oil-Triton-water as one
streak diseases. M. O. San Juan (TRRC). treatment was comparable in effect to
the other treatment of Polyoxin-Dithane-
Two spray cycles of 200 ml Topsin oil-Triton-water spray mixture. Both treat-
M ULV with spray oil, Triton X-45 and ments were applied aerially every 14 days
water to make a total volume of 15 liters for one year. Each treatment plot consis-


and water with a total volume of 29 liters
per hectare on a 27.5 hectare plot of Giant
Cavendish Banana. Another treatment
on a separate plot involved spraying with
300 ml Topsin M ULV for two consecutive
times alternated with one spray cycle of
the Dithane M-45 spray mixture as above.
There were 20 spray cycles for each of
the Topsin M ULV mixtures and 9 spray
cycles for the alternate Dithane M-45
mixture applied during the year. For
control, a separate area of 27.5 hectares
was sprayed with a mixture of Dithane
M-45, spray oil and Triton X-45 to make
a total volume of 29 1 per hectare for 13
spray cycles. A 9 spray cycles consti-
tuted a mixture of Benlate 50 WP, spray
oil, Triton and water. Another 7 cycles
used mixtures of Dithane M-45, Benlate
50 WP spray oil, Triton and water. Based
on all the parameters used, both Topsin


... ... . .. .- "-- -... .. ...-
Benlate, Topsin M either singly or in
combination with oil and Triton at 29 1
per hectare. A total of 31 spray cycles
were applied on the control plot during
the duration of the experiment against
the 26 cycles for the Polyoxin treatments.
Control of sigatoka and black leaf streak
diseases for both Polyoxin treatments did
not statistically differ from that afforded
by the plantation practice of spraying
several combinations of fungicides at
closer spray intervals. Spraying costs
which include cost of the fungicides,
mixing, flagging and airplane spraying
however, were very much less for the
Polyoxin treatments which amounted to
a savings of P1,392.64 per hectare per
year over the control.









Abstracts of Papers


around spray applications of fungi-
cides to control Sigatoka and black leaf
streak diseases of banana. M. O. San Juan
and I. S. Labad (TRRC).

Ground spray experiments using easily-
mixed fungicides were conducted on two-
hectare lots each of Giant Cavendish
bananas. Power sprayers were used to
spray the fungicide mixtures at 14-day
intervals for one year. Daconil 2787
W-75 at 800 gm plus 90 ml Topsin
M ULV in 100 1 water per hectare gave
the best control for sigatoka and black
leaf streak. The second best spray mix-
ture was Daconil 2787 W-75 at 1.8 kg
in 100 1 water per hectare. Results from
the above treatments did not differ
significantly from each other. The third
best fungicide spray mixture was 51 gm
Polyoxin AL (98%) with 25 ml Hoestick.
emulsifierr) in 100 1 water per hectare.
This treatment was better than the fourth
spray mixture consisting 600 gm Daconil
2787 W-75 plus 12.2 gm Polyoxin AL
(98%) in 1001 water.
Ground spray applications using
power sprayers are adaptable for small
banana areas where aerial spray facilities-
are unavailable. However, ground applica-
tions of the fungicides are more expensive
than aerial applications per unit area.

Comparative effects of Dithane M-45
and Dithane 35-F on the control of
Sigatoka and black leaf streak. M. O.
San Juan (TRRC).

Comparable results were obtained in
the control of sigatoka and black leaf
streak diseases on Giant Cavendish
bananas using Dithane M-45 mixed with
Triton AE in 29 1 water as one treatment
and the other, Dithane 35-F in 29 1 water.
These mixtures were applied aerially on
areas of 27.5 hectares each for a total of


zo cycles during tne experimental penoa
of one year. The check plots with the
same area as the other treatments were
sprayed with a fungicide "cocktail"
consisting of Benlate 50 WP, Dithane
M-45, oil, Triton X-45 and water, also
a mixture of Daconil 2787 W-75 and
Topsin M 70 WP in water at a spray
internal of 12 days or a total of 31 spray
cycles during the year.

Baycor 200 EC with or without bana-
na spray oil for the control of three fol-
age diseases of Giant Cavendish bananas.
M. O. San Juan (TRRC).

Baycor 200 EC, a non-systemic foliar
fungicide and found to penetrate into the
leaf tissues, was tried both with and with-
out banana spray oil on separate 11.5
hectare plots. Dithane M-45 and Benlate
50 WP with spray oil and Triton, were
also used as control for comparison. All
experimental spray mixtures were applied
aerially with 26 cycles, while there were
31 cycles for the controls during the
twelve month period. Results obtained
from the.field experiment showed highly
significant control of sigatoka and black
leaf streak with the spray mixture of Bay-
cor 200 EC with banana oil and Triton
X-45 over both the Baycor 200 EC with-
out spray oil and the control. All treat-
ments, however, were equally effective
on the banana freckle disease.

Severity of cassava bacterial blight
using four methods of inoculation. S. J.
Fernandez, C. M. Napiere and M. K. Palo-
mar (VISCA).

The most effective means of introdu-
cing the pathogen in the plant tissues
were through stem puncture and conta-
minated planting materials. Plants ino-
culated using these methods had 100%


[an. & June 1981









20 Philippine Phytopathology Vol. 17


infection, short incubation period, and
early manifestation of symptoms. None
of the plants recovered. There was only
23% infection using soil inoculation al-
though there was no recovery from in-
fected plants. The disease was not as se-
vere using the other methods of inocula-
tion. In contrast, foliar spray inoculation
gave high percent recovery of infected
plants. Generally, the pathogen moved
in an upward direction within the plant.
Downward movement of the pathogen
was occasionally observed when develop-
ping shoots were infected. Early die-back
was noted when inoculation by stem
puncture was made in the apical meris-


__









Phlipp. PhytopathoL 17: 21-29
Sporulation of Cercosporidium personatum and Cercospora arachidicola

SPORULATION IN VITRO OF CERCOSPORIDIUM PERSONA TUM
(BERK. AND CURT.) DEIGHTON AND CERCOSPORA ARACHIDICOLA
HORI FROM PEANUT


R. A. PANINGBATAN and L. L. ILAG

Respectively, Research Associate, Institute of Plant Breeding and Associate Pro-
fessor, Department of Plant Pathology, College of Agriculture, University of the Philip-
pines, College, Laguna.

ABSTRACT

The most abundant sporulation in vitro by both fungi was observed in onion
agar. The peak of conidial production for Cercospora arachidicola Hori and Cercospo-
ridium personatum (Berk. and Curt.) Deighton was observed 20-25 and 25-30 days,
respectively, after seeding the culture slants.









































uL V alUu I l &L1 k7Juf. Au Lau u~AuuIV cUDoaion penous wnen peal oI0 Guumua
gar, Czapek's agar, oatmeal agar, V-8 yields were noted in various culture
juice agar and corn meal agar were pre- media.
>mrAl fnllnwina the methods described Snorulation as affected by temDerature.









Ition of Cercosporidium personatum and C


light on sporulation. Seeding the slants
and sampling procedures were the same
as those done in temperature study. Six
varying light periods were evaluated as
follows: continuous light, continuous
darkness, 15-hr. light with 9-hr darkness
and vice-versa, 10-day light with 10-day
darkness and vice-versa. Culture slants
were incubated at 28 C and at 140 foot-
candles for 20 days for both fungi.


days after. Furthermore, C, personatum
produced its second and third greatest
spore yields in CTA and in OM, respective-
ly, whereas C. arachidicola produced its
second and third most abundant conidia
in PLEOA and MA, respectively. This
shows that each fungus has different
nutritional requirements for asexual spo-
rogenesis.
C. personatum sporulated best at pH
7.00 but C. arachidicola sporulated best


alter seeding on UnA slants whereas C. is shown in Table 3. Exposure to conts
arachidicola showed maximum yield 20 nuous light (140 foot-candles) induce


Jan. & June 1981








Table 1. Sporulation (conidia/ml x 1000) of C. personatum on various agar media8


Culture
MEDIUM

OnA
PLEOA
PDA
OM
V-8
PLEA
PSDA
GlyA
CmA
MA
CTA
CzA


INCUBATION PERIOD (DAYS)c
15 20 25


18.0
2.0
3.5
20.0
3.0
2.0
3.0
7.0
0.0
5.0
16.2
0.0


88.0
7.0
5.5
16.0
3.8
5.5
3.2
2.8
0.0
1.8
47.0
0.0


136.0
7.2
3.2
16.0
6.0
2.0
6.8
3.2
0.0
6.2
12.5
0.0


31.8
10.0
3.0
21.0
3.5
1.2
5.8
1.0
0.0
5.5
42.2
0.0


39.9 a
4.3 d
2.4 ef
11.0 c
2.7 ef
1.6 f
2.7 ef
2.9 ef
0.0 g
3.6 de
20.9 b
0.0 g


Meand Of 1.3 e 3.6 d 6.6 c 15.0 a 16.6 a 10.4 b


aEach slant was filled with 2-ml water to suspend conidia, means of 8 replications.
bOnA (onion agar), PLEOA (peanut leaf extract oatmeal agar), PDA (potato dextrose agar), OM (oateal agar), V-8 (V-8 juice agar),
PLEA (peanut leaf extract agar), PSDA (peanut seed decoction agar), GlyA (glycerine agar), CmA (corn meal agar), MA (malt
agar), CTA (carrot tuber agar), CzA (Czapek's agar).
cCulture slants incubated at 25 C and at 140 foot-candles.
dMeans with common letter are not significantly different at 5% level using Duncan's multiple range test.









Table 2. Sporulation (conidia/ml x 1000) of C. arachidicola on various agar mediaa


CULTURE INCUBATION PERIOD (DAYS) MEANb
MEDIUM 5 10 15 20 25 30 35


OnA 0 15.8 222.2 225.5 214.5 127.5 122.8 132.6 a
PLEOA 02.5 2.5 62.5 160.5 149.8 110,8 69.5 79.4 b
PDA 0 21.0 62.5 32.0 37.8 29.5 19.0 28.8 f
OA 0 20.5 20.0 54.5 37.8 44.5 57.5 33.4 e
V-8 0 18.0 30.8 22.2 27.5 16.5 24.5 19.9 g
PLEA 0 4.2 2.8 6.2 4.2 3.5 6.0 3.8 i
PSDA 0 3.0 25.2 66.5 77.0 92.0 41.2 43.6 d
GlyA 0 6.2 11.0 21.0 10,8 8.2 5.8 9.8 h
CmA 0 0.0 0.0 2.0 0.8 0.5 1.0 0.6 j
MA 0 55.5 68.5 61.2 71.8 66.0 18.8 48.8 c
CTA 0 2.8 8.5 11.2 12.2 19.0 11.2 9.3 h
CzA 0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 j









6


Philippine Phytopathology


'able 3. Sporulation of C personatum and
various hydrogen ion concentration



[YDROGEN ION CONCENTRATION (pKH

Before After
terilization Sterilization


5.0 5.15

5.5 5.54


"Incubated at 25-C and at 140 foot-candles.
U









Jan. & June 1981 Sporulation of Cercosporidium personatum and Cercospora arachidicola 27


Table 4. Effect of varying temperatures on sporulation (conidia/ml x 1000) of C
personatum and C arachidicolaa

TEMPERATURE (C) C personatum b C arachidicola c

15 0.0 c 0.0 c
20 0.7 c 0.5 bc
25 2.8 a 1.5 b
30 1.8 b 11.2 a
35 0.0 c 0.0 c

aCulture slants were incubated in continuous darkness.

b25-day old CTA, means of 8 replications.

c20-day old OnA, means of 8 replications. Means with common letter are signifi-
cantly different at 5% level using Duncan's multiple range test.



Table 5. Effect of different light periods on sporulation of C personatum and C
arachidicola 20 days after incubation at 280C and at 140 foot-candles.


LIGHT PERIODa


SPORULATION (CONIDIA/ml x 1000)b
C personatum C arachidicola


CL 45.8 a 116.5 a

CD 4.8 d 17.0 e

15-hr L 9-hr D 40.8 ab 73.0 b

9-hrD 15-hr L 38.8 b 57.5 c
10-day L 10-day D 44.2 ab 59.2 c
10-day D 10-day L 31.5 c 35.5 d

aCL stands for continuous light, CD for continuous darkness, 15-hr L 9-hr D for
15-hr light and 9-hr darkness daily and vice-versa, 10-day L 10-day D for day light fol-
lowed by 10 days darkness and vice-versa.
bC personatum grown in CTA., C arachidicola n OnA, means of 8 replications.
Means with common letter are not significantly different at 5% level using Duncan's
multiple range test.









Philippine Phytopathology


conidial production of both fungi by
about 7 to 9 times those produced when
exposed to continuous darkness. C. per-
sonatum, however, had the greatest
spore yield when exposed to continuous
light (140 foot-candles), 15-hr light with
9-hr darkness daily and 10-day light with
10-day darkness but gave the least when
incubated in continuous darkness. More-
over, the first exposure of cultures to
10-day light of the 20-day incubation
period had significantly enhanced spore
production compared to that when first
exposed to 10-day darkness.


C. arachidicola, in general, responded
similarly to light exposure in that light
enhanced more conidial production than
in darkness. Continuous light triggered
the most abundant sporulation for C.
arachidicola. It was further observed that
longer daily light exposure (15-hr L + 9-
hr D daily) brought about significant
increase in spore production compared
to shorter daily light exposure (9-hr L +
15-hr D). Other studies confirm that light
is required for conidial production by
the two fungi (Smith, 1971; Bhama and
Swamy, 1976; Swamy and Mani, 1978).


Vol. 17








Jan. & June 1981 Spanlation of Cercosporidium personatum and Cercospora arachidicola 29


LITERATURE CITED



ALABI, R. O., S. H. Z. NAQVI and J. A. EKUNDAYO. 1976. Growth and sporulation
of Cercospora arachidicola Hori in pure culture. Rev. Plant Pathol. 58: 206.

BHAMA, K. S. 1971. Suitability of different types of glassware in sporulation studies on
Cercospora personata. Current Sci. 40: 45-46.

BHAMA, K. S. and R. S. SWAMY. 1976. Sporulation of Cercospora personata in culture.
IV. Effect of riboflavin in the medium. Rev. Plant Pathol. 57: 2667.

GARREN, K. H. and C. R. JACKSON. 1973. Peanut diseases. In Peanuts: Culture and
Uses. Am. Peanut Res. Educ. Assoc., Inc. Oklahoma State University, Oklahoma,
Chapter 13, p. 429-494.

JENKINS, W. A. 1938. Two fungi causing leafspots on peauts. J. Agr. Res. 56: 317-332.

PURKAYASTHA, R. P. 1963. Factors associated with conidial production and growth of
Cercospora personata (Berk. and Curt.) Ell. & Ev. causing tikka disease of ground-
nut (Arachis hypogea L.). Indian J. Mycol. Res. 6: 69-77.

RIKER, A. J. and R. S. RIKER. 1936. Introduction to Research on Plant Diseases. N. Y.,
USA. 44 p.

ROLDAN, E. F. and A. F. QUERIJERO. 1939. Black spot of peanut. Phil. Agr. 27: 669-
682.

SHANTA, P. 1956. Isolation of Cercospor personata, its sporulation and growth in
pure culture. Indian Acad. Sci. B44: 271-275.

SMITH, D. H. 1971. A simple method of producing Cercospora arachidicola conidial
inoculum. Phytopathology 61: 1414.

SWAMY, R. N. and K. MANI. 1978. Photosporogenesis of Cercospora personata as in-
fluenced by glycine, riboflavin and malonic acid. Current Sci. 47: 32-33.

WINSTON, J. R. 1923. Citrus scab: its cause and control. USDA Bull. 1118: 39 p.









mupp. mRytopatmoL 17: su-17


INFLUENCE OF RATES OF FERTILIZER AND LIME APPLICATION
ON THE INCIDENCE OF MAIZE BACTERIAL STALK ROT CAUSED
BY ER WINIA CAROTOVORA VAR. CHRYSANTHEMI

FE DIVINAGRACIA-LAYSA and O. R. EXCONDE

Respectively, Senior Plant Pathologist, Bureau of Plant Industry, Pili, Camarines
lur, and Professor of Plant Pathology, Department of Plant Pathology, College of Agri-
ulture, University of the Philippines at Los Bafios, College, Laguna.
Portion of a Ph. D. Thesis of the senior author.
This study was supported in part by the Philippine Council for Agriculture and
resources Research (PCARR).
ABSTRACT

Plants which had been fertilized with 120 kg N/ha and inoculated with the
causal bacterium produced shorter lesions and minimal stalk toppling compared
with those fertilized with 90 and 60 kg N/ha.
In both pot and field experiments, corn plants which had been fertilized
alone with high rate of NPK (120-90-90 kg/ha) or in combination with 5 T lime/ha
after having been inoculated with the causal bacterium produced restricted lesion
and decreased stalk toppling compared with lower rates (90-60-60 kg NPK/ha and
60-30-30 kg NPK/ha) with or without a combination of lime at 3 and 1 T/ha,
respectively. Plants, fertilized alone with phosphorous, potassium and lime after
having been inoculated with the causal bacterium produced severely macerated
-- -. .... - - -a,-- _- -- ft St----A









Tan L. Tnla 10 I M


Table 1. Rates of fertilizer and lime used in the study

Treatment No. Description


1 60 kg N/ha
2 90 kg N/ha
3 120 kg N/ha
4 30 kg P205/ha
5 60 kg P205/ha
6 90 kg P205/ha
7 30 kg K20/ha
8 60 kg K20/ha
9 90 kg K20/ha
10 90-30-30 NPK kg/ha
11 90-60-60 NPK kg/ha
12 120-90-90 NPK kg/ha
13 1 T lime/ha
14 3 T lime/ha
15 5 T lime/ha
16 1 T lime / 60-30-30 kg NPK/ha
17 3 T lime / 90-60-60 kg NPK/ha
10 C / i FI An A ^^ r\ 1.^ vMT /I -


isolate C116. The bacterial suspension
was standardized at 107 cells/ml. Data
on disease development from among
the treatments were compared 120 hr
after inoculation. These involved count-
ing of the plants that toppled over within
the period, and measurement of upward
lesion spread (in cm) from the point of
inoculation.
A second field trial of the same treat-
ments was conducted in September 1979
using another susceptible variety, Pacific
9, and another isolate, P9. The same me-
thodology in conducting the study was
followed.
Pot experiment. Confirmatory pot
experiments were conducted after the
field experiments using variety Pacific 9
and two isolates, C116 and P9. The same
trantmat+e anr mrthndninm, wprp fnl.


PA11A, A1f11,1U1,A I.JjVA l Al1vx fJ11ttV a.nI.^.'.JJ


lowed. Nine kilograms of baked soil were
placed in 30-cm dia pots. Two plants
per pot were maintained for inoculation
6 weeks after sowing. Each treatment
was replicated three times.
Analysis of data. Logarithmic trans-
formation of data on lesion length and
percentage toppling was employed to
minimize the variance. Analysis of data
from pot and field experiments were con-
ducted separately and the results com-
pared later.

RESULTS

Low incidence of stalk rot as shown
by very limited lesion spread from the
point of inoculation and absence of top-
pling, were noted in both pot and field
nintf nn which 1fl0 kI N/ha (Fi 11 and












20-90-90 kg NPK/ha alone or in com- kinds and rates of fertilizer and lime as
nation with 5 T lime/ha were applied they affected lesion spread. Table 4
Fig. 2 and 3). At 120-90-90 kg NPK/ha showed that longer lesions occurred
nd 90-60-60 kg NPK/ha applied alone or when isolate P9 was inoculated on plants
vith 1 and 3 T lime/ha, respectively, deficient in nutrients or where only
shorter lesions and low or no incidence of phosphorous, potassium and lime were
opplingin both pot and field experiments applied, as compared with C116. The
vere observed. Similarly, shorter lesions longest lesions in both pot and field trials
nd low or no incidence of toppling in were observed on plants fertilized with 30
oth field and pot experiments were kg P/ha and inoculated with isolate P9.
obtained from plants fertilized with 60 The shortest lesions were noted on plants
nd 90 kg N/ha. fertilized with 120 kg N/ha in both pot
Phosphorous and potassium fertilizers and field experiments inoculated with iso-
Fig. 1) either at 90 or 30 kg/ha and lime late C116. With regard to stalk toppling
either at 1 and 5 T/ha (Fig. 4), applied the interaction between isolate and treat-
.-.- .... : i--- .. A.. .. ments in both pot and field trials was not


rates of phosphorous, potassium and lime
ppled on corn plants induced longer
.sions and high percentage of toppling.
however, in pot experiments, plants sup-
fed with at 60 kg P/ha, and potassium
nd lime 90 kg/ha and 5 T/ha, respective-
f, showed shorter lesions (Table 2).
a pot experiments, high percentage of
talk toppling occurred at 90 kg P/ha,
0 kg K/ha and 1 and 3 T lime/ha (Table
I). Plants receiving no fertilizer and lime
a both field and pot experiments,
bowed longer lesion and high per-
entage of toppling.
Notwithstanding the significant differ-
nces among indivdul treatments partic-
lar in both periments, results
bowed that less stalk rot developed on
sants fertil4ed with N fertilizer and also
rith NK fertilizer applied alone or in
combination with lime. Severe incidence
curmed when plants were not fertilized,
Grown on nutrient-deficient soils, or
a cases where phosphorous, potassium
nd lime were used alone.
Statistical analysis showed significant
* ,t*im I. *- *" ionlat, 1 na tti


Pot and field experiments revealed
hat plants fertilized with increasing rates
>f nitrogen and inoculated with the causal
bacterium produced shorter lesions simi-
ar to a resistant action. The causal bac-
erium apparently failed to spread as
hown by the restricted lesion in plants
ertilized at 120 kg N/ha as compared
vith those fertilized at 90 kg and 60 kg
4/ha, respectively. The reaction was more
obviouss on plants inoculated with isolate
:116 than those inoculated with P9,
which produced longer lesions. However,
he same trend of lesion development,
. e., decreasing lesion length with increas-
ing N fertilier rates was observed. Stalk
toppling was either minimal or did not
mccurat al
High rates of NPK (120-90-90 kg/ha)
applied alone or in combination with 5
Slime/ha also restricted lesion spread as
comparedd with the lower rates (904060
kg NPK/ha and 60-30-30 kg NPK/ha)
without or with lime at 3 and 1 T/ha,
respectively. Plants also had either none
-- -r ..k.. ,f 11 *.. T1,q








~-)-- - ~1-1 --11~-----1


Jan. A IIun I R


Fig. 3. Stalks inoculated with isolate C116
S1. Stalks inoculated with isolate showing various degrees of rotting.
Cl16 showing various degrees of T 16 plants fertilized with 60-30-
rotting. T3 fertilized with 120 kg 30 kg NPK + 1 T lime; T17 fer-
N/ha; 7 fertilied with 90 kg tilized with 90-60-60 kg NPK 4 3
P/ha; 79 fertilized with 90 kg T lime/ha; 718 fertilized with
K/ha; and T19 no fertilizer nor 120-90-90 kg NPK/ha; T19 -
lime. no fertilizer nor lime.


















Fig. 2. Stalks inoculated with C116 show-
ing various degrees of rotting. T10 Fig. 4. Stalks inoculated with isolate P9,
fertilized with 60-30-30 kg NPK/ showing severe stalk rotting. T13 -
ha; T11 90-60-60 kg NPK/ha; 1 T lime/ha; T14 3 T lime/ha;
T7 -- 120-l.-On k, NPKIha- T15 5 T limel/ha- and TO -









Phlippine Phytopathology


VoL 17


observation was true in both pot and field ing to Van Lamen, Riker and Baldwin
experiments. (1952), various amino acids were ob-
Applying phosphorus, potassium and served to weaken the virulence of a pa-
lime alone, predisposed the plants to thogen.
stalk rot. Tissues were severely macerated The various kinds and rates of fertiliza-
and lesion spread was unrestricted. Stalk tion and liming on the host plant could
toppling was also rampant. Likewise, have affected the ability of the stalk rot
plants not fertilized or limed were organism to synthesize pectolytic en-
severely infected. zymes at the infection site. According
The seemingly resistant reactions ob- to Zucker, Hankin and Sands (1972),
served on plants given with high rates of pectate lyase synthesis could be regula-
nitrogenous fertilizers could be explained ted, and the nutritive quality in the me-
by the increase in the total nitrogen sup- dium could be one factor. Therefore,
ply and soluble amino acids which might the nature and amount of nutrients
also be injurious to the pathogen. Accord- and plant metabolic products available


Table 2. Influence of fertilizer and lime application on lesion length and incidence of
stalk toppling (Field experiment)

MEANSa
TREATMENTS Lesion Percentage
Length Toppling

60 kg N/ha 2.19 c 0.00 c
90 kg N/ha 2.15 cd 0.00 c
120 kg N/ha 1.96 c 0.00 c
30 kg P/ha 3.20 a 3.73 a
60 kg P/ha 3.13 a 3.93 a
90 kg P/ha 3..11 a 4.04 a
30 kg K/ha 3.10 a 3.86 a
60 kg/K/ha 314. a 3.73 a
90 kg K/ha 3.15 a 3.91 a
60-30-30 kg NPK/ha 2.49 b 0.47 b
90-60-60 kg NPK/ha 2.20 c 0.00 c
120-90-90 kg NPK/ha 2.07 d 0.00 c
1 T lime/ha 3.08 a 4.07 a
3 T lime/ha 3.09 a 4.04 a
5 T lime/ha 3.09 a 4.14 a
60-30-30 kg NPK / 1 T lime/ha 2.20 c 0.00 a
on n' rn 1- iX DV I l T Yi.m/kn 9 n7 n n a









Rates of fe.dAlhw d Hmne application


to the soft rot bacterium must have a
significant effect on pectolytic enzyme
production. Consequently its availability
has a direct relationship to the degree of
tissue maceration. This may also partly
explain the apparent resistance of PH 801
at high rates of nitrogen and NPK fertil-
ization, and the high susceptibility of
plants supplied with phosphorous, potas-
sium and lime as well as plants grown in
soils of low fertility level.
Nutrients made available to the host
plant do not only affect the pathogen at
the infection site and during pathogene-


sis, but likewise affect the physical struc-
tures and physiological processes of the
plant and its ability to counteract the
effects of pathogen attack (Agrios, 1969).
This also shows why in some situations
the disease is aggravated and in others, it
is minimized by fertilizer application.
The results of this study point to the
favorable effects of high rates of N and
NPK fertilization in minimizing stalk rot
damage, and the apparent aggravating ef-
fects of phosphorus, potassium and lime
application as well as low soil fertility.


Table 3. Influence of fertilizer and lime application on lesion length and toppling (Pot
experiment)

MEANSa
TREATMENTS Lesion Percentage
Length Toppling

60 kg N/ha 2.1 ij 0.80 e
90 kg N/ha 1.97 k 0.70 c
120 kg N/ha 1.92 k 0.70 c
30 kg P/ha 3.22 a 4.55 bc
60 kg P/ha 2.97 e 3.28 d
90 kg P/ha 3.00 e 4.97 ab
30 kg K/ha 3.05 cd 5.71 a
60 kg K/ha 3.06 bc 5.71 a
90 kg K/ha 3.01 cde 4.97 abc
60-30-30 kg NPK/ha 2.41 g 0.70 e
90-60-60 kg NPK/ha 2.08 ij 0.70 e
120-90-90 kg NPK/ha 2.06 j 0.70 e
1 T lime/ha 3.05 cd 0.70 e
3 T lime/ha 2.86 f 4.95 abc
5 T lime/ha 2.90 f 4.13 cd
60-30-30 kg NPK / 1 T lime/ha 2.13 i 0.70 e
90-60-60 ng NPK / 3 T lime/ha 2.24 h 0.70 e
120-90-90 kg NPK / 5 T lime/ha 2.08 ij 0.70 e
Control 3.11 b 5.38 ab

aLogarithmic transformation of data.Means with the same letter are not significantly
different at the 5% probability (DMRT).


Jan. & June 1981









Phlippine Phytopathology


Table 4. Effect of isolate and treatment interaction on lesion length

LESION LENGTHa

ISOLATE TREATMENT (Field) (Pot
Experiment Experiment


I-P9 60 kg N/ha 2.23 fg 2.17o
90 kg N/ha 2.25 fg 2.10 o
120 kg N/ha 2.33 cf 2.45 Im
30 kg P/ha 3.24 a 3.23 a
60kg P/ha 3.15 ab 3.05 ed
90 kg P/ha 3.12 ab 3.02 ed
30 kg K/ha 3.12 ab 3.03 ed
60 kg K/ha 3.20 ab 3.20 eb
90 kg K/ha 3.20 ab 3.14 ab
60-30-30 kg NPK/ha 2.69 c 2.84 hi
9040-60 kg NPK/ha 2.46 ed 2.32 n
120-90-90 kg NPK/ha 2.46 ed 2.42 m
1 T lime/ha 3.07 ab 3.02 ed
3 T lime/ha 3.13 ab 3.01 ed
5 T lime/ha 3.12 ab 3.01 ed
60-30-30 kg NPK / 1 T lime/ha 2.51 d 2.45 1
906060 kg NPK/ 3 T lime/ha 2.60 cd 2.63 k
120-90-90 kg NPK/ 5 T lime/ha 2.56 cd 2.511
Control No fertilizer and lime applied 3.15 ab 3.19 ab

I-C116 60 kg N/ha 2.16 gh 2.05 pg
90 kg N/ha 2.05 gh 1.83 r
120 kg N/ha 1.60 m 1.39 t
30 kg K/ha 3.15 ab 3.21 ab
60 kg K/ha 3.12 ab 2.90 gh
90 kg K/ha 3.09 ab 2.98 ef
30 kg P/ha 3.08 ab 3.07 d
60 kg P/ha 3.09 ab 2.92 fg
90 kg P/ha 3.09 ab 2.88 gh

C-116 60-30-30 kg NPK/ha 2.29 fg 1.98 q
90-60-60 kg NPK/ha 1.95 gi 1.84 r
120-90-90 kg NPK/ha 1.68 lm 1.70 s
1 T lime/ha 3.09 ab 3.09 cd
2 T lime/ha 3.06 ab 2.71 j
5 T lime/ha 3.05 b 2.80 i
60-30-30 kg NPK / 1 T lime/ha 1.89 ijk 1.81 r
90-60-60 kg NPK / 3 T lime/ha 1.85 jk 1.84 r


VoL 17









Jin A June 1QR1


120-90-90 kg NPK / 5 T lime/ha 1.76 kl 1.65 a
Control No fertilizer 3.14 ab 3.02 ed


aLogarithmic transformation of data. Means with the same letter are not significant-
ly different at the 5% level (DMRT).



LITERATURE CITED

AGRIOS, G. M. 1969. Effects of environment on development of infectious plant di
seases. p. 169-170. In Plant Pathology, 1st. ed. Academic Press. New York and Lon
don, 628 p.

VAN LAMEN, T., M. RIKER and A. J. BALDWIN. 1952. Virulent attenuating agents
J. Bacteriol. 63:715-721.













IDENTIFICATION OF SOURCES (
DISEASES OF SORGIH

S. C. DALMACIO, M. P. D

Assistant Professor and former Rest
Plant Pathology; and Research Assistant, Ii
College, Laguna.

ABS'

Artificial and natural inoculation r
five major diseases of sorghum, namely:
Rhizoctonia sheath blght. The proportic
tested are as follows: 201 resistant out a
gray leaf spot, 51 out of 2268 for tar q


RESISTANCE TO SOME MAJOR
IN THE PHILIPPINES

(AN and C. B. PASCUAL

:h Assistant, respectively, Department of
tute of Plant Breeding, U. P. at Los Bafios,


kCT

Lods were used to screen for resistance to
r, tar and target leaf spots, leaf rust, and
of resistant lines to the number of lines
5 lines tested for rust, 27 out of 2525 for
198 out of 2484 for target leaf spot and


resistance to tar spot was expressed as few number of stromata. Hypersensitive reaction
and/or few lesion/pustule number wre observed in sorghum germplasm resistant to
rust and grey leaf spot.
Field screening was complicated by interference among follar diseases,
plant height and maturity.
Possible implications of these results in breeding for disease resistance
are discussed.


Diseases are significant natural hazards farming of this newly introduced feed-
to sorghum production throughout the grain crop are used.
world. In the United States, estimated di- The most logical approach to control-
sease losses on sorghum was between 9 ling sorghum diseases is the use of resistant
and 10 percent (Le Clerg, 1964). Based varieties. This would require extesnive
on the scanty information available, Cra- screening of germplasm using the most
mer (1967) estimated 12 percent loss for effective screening technique available to
Asia (excluding mainland China). Al- identify good sources of resistance. This
though no information on losses due to study was conducted in the Department
sorghum diseases is available in the Philip- of Plant Pathology and Institute of Plant
pines there is good evidence that diseases Breeding, UPLB, from 1978 to 1980 to
take their annual toll. Of the 13 diseases lay the groundwork in the screening for
of sorghum presently occurring in the resistance to sorghum diseases and to
Philippines, 5 were considered important identify genuine sources of resistance to
based on disease surveys conducted since the major sorghum diseases.
1969 (Karganilla & Elazegui, 1970;


unent in
)pment i
problem
*P inft.n!


'w* u.-aw.w naw Jtrfl. &l.J.JU.LJ U ,&t 11
he Philippines is
disease epiphy- Sorghum germplasm in
will likely in- cally developed lines and
re methods of trials were Dlanted in sin








I of Disease Resistance in S


the field and evaluated for resistance to
sorghum diseases. Diseases considered in
the study were rust (Puccinia purpurea
Cooke), gray leaf spot (Cercospom sorghi
Ell. & Everh.), tar spot fPhyllachora
sorghi Fckl.), target leaf spot (Helmin-
thosporium sorghicola Lefebre & Sher-
win), and Rhizoctonia sheath blight
(Rhizoctonia solani Kuhn).
Various methods of screening were
employed depending upon the disease
and season. Artificial inoculation by
whorl inoculation method was used to
screen for resistance to gray leaf spot
(GLS) and target leaf spot (TLS). This
method consists of placing 10-20 sor-
ghum grains, previously infested with a
pure culture of the appropriate organism,
into the whorl of 1-month old plants.
Evaluation for resistance was made 10
days (TLS) or 3 weeks (GLS) later, based
nr thA o e ft- lAf I ne n-rk4.j.bal /r;. 1\


The efficiency of three methods ol
inoculation for Rhizoctonia sheath blight
(RSB) were compared. These methods
consist of placing the inoculum in the
furrows at planting time (soil inoculation),
placing the inoculum at the base of 1-
month old plants (basal inoculation), and
inserting inoculum between the stem and
leaf sheath about 2 nodes above the
ground (leafsheath inoculation). In all
methods, inoculum consists of pure cul-
ture of R. solani grown asceptically on
pieces of sorghum stems and leaves for 1
week. Disease rating was made at six dif-
ferent stages of plant growth.
The leafsheath inoculation method, as
described above, was used to screen for
resistance to RSB. Resistance was evalua-
ted on the basis of percentage infected
leaves at flowering and 10 days before
harvest.


Figure 1. Lesion types induced by H. sorghicola on different sorghum lines representing
the disease rating scales of 1-5. Similar types of lesions are induced by C. sorghi, al-
though scale 1 has not been observed.


Jan. & June 1981









40 Philippine Phytopathology VoL 1


to screen for resistance to rust, viz., the 3 medium-sized pustules occasional
whorl inoculation and natural infection. ly producing spores
The whorl inoculation consists of placing 4 slightly bigger pustules frequently
spore suspension, previously prepared producing spores
by scraping rust pustules off the diseased 5 large pustules with abundan
leaves, into the whorl of 1-month or older spore production
plants. Natural infection consists of plant- 3. Rhizoctonia sheath blight
ing the test materials between or adjacent 1 up to 20% leaves infected












Table 1. The effect of inoculation methods on the development of Rhizoctonia sheath
blight (percentage infection) at various sampling stages.

Sampling Methods of Inoculationa
Stages M1 M2 M3

S1 31.0 24.0 30.0
S2 43.0 51.0 48.0
S3 46.0 46.0 58.0
S4 60.3 56.0 81.0
S5 66.6 65.4 87.0
S6 69.0 73.0 95.1

Mean 52.6 52.6 66.5

aM1 M3 denote soil inoculation, inoculation around the base of the plant and leaf
sheath inoculation, respectively.
b S S6 denote one month after planting, early booting stage, flowering stage, 1 week
after flowering, 2 weeks after flowering and 1 week before harvest, respect-
ively.


nates the effects of antagonistic soil to the disease. However, 9 entries, name-
microorganisms, 3) the organism is assured ly: UPL Sg-5, Cosor 3, CS-251, CS-252,


Results on the screening for resistance
to the five major sorghum diseases are
summarized in table 2. Percentage infec-
tion on the 88 lines and varieties evalua-
ted for RSB resistance ranged from 65.9-
100, indicating the absence of resistance

Table 2. Summary of results on the scree

Diseases


Gray Leaf Spot
Rhizoctonia Sheath Blight
Rust
Tar Spot
Target Leaf Spot


Percentage infection appeared to be asso-
ciated with plant height since plants show-
ing lower infection were relatively taller
than those with higher infection.
Although it is still premature to con-
clude, based on the results of 88 lines

ag for resistance to five sorghum diseases.

No. of Lines/Varieties:
Tested Resistant

2525 27
88 0
555 201
2268 51a
2484 198


_ __









Philippine PhytoptholVt


screened, resistance to RSB may be diffi-
cult to obtain. The fungus, R. solani, has
a very wide host range that morpoholo-
gical or biochemical differences among
sorghum varieties would unlikely affect
the rate of development of the fungus.
Experience with other crops against R
solani and other less specialized parasites
(Nelson, 1973), supports this contention.
However, based on the observation that
taller varieties are less affected by the di-
sease at a given time compared to shorter
varieties, one possible means of minimiz-
ing losses due to the disease would be to
avoid very short and late maturing varie-
ties.

Tar Spot
Of the 2268 local and introduced germ-
plasm evaluated for resistance to tar spot,
51 showed resistance. However, only
two, namely: Ace. 988 and Ace. 2059
showed a disease rating of 1. No line,
variety or hybrid was found to be com-
pletely free of tar spots and no evidence
of hypersensitive reaction was observed.
Resistant plants tend to have relatively
fewer stromata than susceptible plants.
Appearance of stromata also tends to be
delayed.
The rare occurrence of resistance to
tar spot is quite surprising, considering
the obligate parasitic nature of the fun-
gus. Experience with other obligate para-
sites like rusts and mildews showed com-
mon occurrence of resistance within the
host species. On the other hand, the tar
spot fungus, P. soghi, behaves quite dif-
ferently from the rusts and mildews. P.
sorghi attacks its hosts with its sexual
stage. Hence, one possible explanation
for the apparent absence of resistance
sources would be the assumed high patho-
genic variability of the fungus. Through
sexual reproduction, genetic recombina-
A- *_ _ .. __ -__ A r -l A ^ .


fungus population consists of numerous
pathogenic races capable of attacking
diverse sorghum genotypes. The impor-
tance of the sexual stage as a means of
increasing pathogenic variability has been
well demonstrated nPhytophthora infes-
tans in potato in Mexico (Niederhauser,
1961). If such is the case, it might be im-
possible to identify lines with the vertical
type of resistance (sensu van der Plank,
1963) without the use of specific isolates
of the pathogen. On the other hand, the
use of specific isolates of the fungus may
be precluded in the absence of the asexual
stage and the obligate parasitic nature of
the fungus.
The manifestation of resistance to tar
spot in the forms of delayed appearance
and number of stromata (Fig. 2) imply
that resistance is of the horizontal type
(sensu van der Plank, 1963). Evaluation
of such type of resistance is quite diffi-
cult because of its quantitative nature
which is easily influenced by environmen-
tal changes as well as inoculum potential.
One possible approach would be to screen
germplasm in replicated disease nursery
plots to avoid the effect of uneven dis-
tribution of inoculum. The components
of nonspecific resistance such as disease
efficiency, latent period, infectious pe-
riod and sporulation capacity may also
be investigated using artificial inoculation.

Gray Leaf Spot
During the 1979 wet season, a total of
2349 entries were screened for resistance
to GLS using either artificial inoculation
of natural infection or both. Based on the
respective criteria for evaluating resistance
to the disease, 14 out of 319 artificially
inoculated and 6 out of 2030 naturally
infected plants showed resistance. Of 233
entries that were both artificially inocula-
ted and naturally infected, 35 entries
k- -. A All __


Vni 17








Soues of Disee Resstance in Sorghum


Figure 2. Leaf sections of sorhum lines resistant (left) and susceptible (right) to tar spot.


35 entries showed lower infection rating
of 2 based on the number of lesions but
higher infection rating of 4-5 based on
lesion type. In 1980 dry season, 330 en-
tries were screened for resistance to-GLS
including 154 that were already screened
previously. Eight entries showed resis-


tance, one of which (Acc. 771) was alrea-
dy found resistant during the previous
screening.
Results on the screening for resistance
to GLS indicate that resistance is expressed
in the form of hypersensitive response
(Fig. 3) as well as lesion number. This


',. i ".




Figure 3. Leaf sections of sorghum lines susceptible (left) and resistant (right) to gray
leaf spot.


Jan & June 1981









Ph41~in.I Diwvna~athnina


uld explain the apparent inconsistency emphasis may be placed more on the pus-
disease rating using artificial and natu- tule number type of resistance (i. e., hori-
I inoculation. Lines classified resistant zontal resistance, sensu van der Plank,
sed on lesion numbers were classified 1963), so as not to put high selection
sceptible based on lesion type. It is pressure on the pathogen population.
erefore, recommended that sources of Rust fungi are notorious fox their high
distance should be identified using both pathogenic variability which enable them
methods. In the development of varieties to overcome race-specific or the hyper-
sistant to GLS, the hypersensitive type sensitive type of resistance.
resistance may be dealt with initially
Cause of its ease in incorporation. Later, Target Leaf Spot
e two types of resistance may be comr- Of 2484 germplasm materials screened
for resistance to TLS since 1978, 198
ned inttoone genotype to ensure stabil- for resistance to TS since 1978198
Sit were found resistant. Of these resistant
I of resistance.
lines, the resistance of 31 has been con-
ast firmed at least 3 times. A number of
A total of 355 sorghum germplasm these lines are now being utilized as do-
J. ^ -__.._ ___ ___A Al> _1-_ L- J __-


w method. One hundred forty eight
48), 18 and 189 entries showed resis-
nt, intermediate and susceptible reac-
mas respectively. Of the 99 locally
veloped lines tested, 17 showed resis-
nce. In 1980 dry season, 200 lines com-
ising mostly introduced materials were
reened for rust resistance using the
hor inoculation method. A total of 53
sistant lines were found.
Resistance to rust was expressed in the
nrm of hypersensitive reaction and/or
w number of pustules. Some resistant
nes showed very small necrotic spot or
Istule with no sporulation as in CS-143.
others showed very few pustules but ty-
cally the same size as those produced
n susceptible plants. Lesion number
distance may be due to longer latent
period and/or lower sporulation capacity
I has been found in CS-137 and CS-174
:oncibido, 1979). Slow rusting was also
-monstrated in TAM 428 and Tx 623
;rederiksen and Rosenow, 1979).
Resistance to rust appears to be more
nmmon among sorghum cultivars. In
-Am- 4r- *_ -r U -,brnv~


Resistance to TLS was expressed in
e form of hypersensitive reaction, cha-
cterized by small, chlorotic or necrotic
sions (scales 1 and 2 of Figure 1). Resis-
nce in the form of fewer number of le-
)ns may also occur but could not be de-
cted by whorl inoculation.
Table 3 enumerates the germplasm
tes identified as resistant to the various
rghum diseases. Based on the above
suits, resistance to TLS and rust may be
immonly encountered among sorghum
rmplasm as compared to GLS and tar
ot and RSB.

feet of Plant Stature and Maturity
Two factors might be considered in
entifying sources of resistance, namely:
ant stature and maturity. In a trial
inducted in 1979 wet season to deter-
ine the effect of plant height and ma-
Arity of resistance to tar spot, significant
>rrelation values of 0.42 and 0.44
ere obtained, respectively. The influ-
ice of maturity on resistance to a num-
-r nf *rnmtlm li a- a aaesee&l tnaPthlr









Jan. & June 1981 Soces of Disease Resistance in Sorghum 41


son. The average correlation value was Philippine conditions, a number of sor
- 0.65 which was highly significant. This ghum diseases occur simultaneously it
means that the later the plant matures or the field. Early and high incidence of
the taller the plant the lower is the di- foliar disease, for instance, would retard
sease rating. Similar results have also been if not preclude the development of othe:
reported (Scott, 1973; Frederiksen and foliar diseases. Hence, it was frequently
Rosenow, 1979). On the other hand, observed that a line heavily attacked b3
not all late maturing plants were resistant tar spot is relatively free of rust or vicA
and vice versa. Likewise, taller plants versa. Likewise, there is the difficult
were not always esistant. of distinguishing TLS from GLS without
The effect of plant height on disease examining closely the individual lesions
development may be explained in terms This would make evaluation of these tw<
of differences in the micronvironment diseases quite tedious under field condi
of tall and short plants when planted in tions using natural inoculum.
adjacent rows. Taller plants usually have Results of this study undoubtedly
widely-spaced leaves, with some leaves would facilitate subsequent identification
exposed above the canopy of neighboring of additional sources of disease resistance
dwarf plants, hence, permitting faster air as well as the development of high-yield
circulation and retarding disease develop- ing sorghum varieties and hybrids wit!
ment. The effect of maturity, on the broad spectrum of resistance to a number
other hand, may be due to some physio- of sorghum diseases.
logical factors related to the stage of dev-
elopment of the plant. Another possible
explanation for the association of matur- A. Target Leaf Spot 23. Acc. 581
ity with resistance is the tendency of late 1. Wheatland B 24. Acc. 59:
maturing varieties to grow taller. Signifi. 2. IS 8211 25. Ace. 59:
cant correlation coefficient of 0.34 was 3. IS 10316 B 26. Acc. 59!
found between plant height and maturity. 4. 2077 B 27. Acc. 60:
Scott (1973) also showed that plant 5. CS-133 28. Acc. 624
stature and stage of maturity influence 6. Acc. 288 29. Ace. 73'
susceptibility of wheat to Septoria 7. Acc. 297 30. Acc. 74!
nodorum. 8. Acc. 301 31. Acc. 771
The possible implication of this ob- 9. Acc. 305
servation is that, disease assessment with- 10. Acc. 332 B. Rust
out considering maturity and plant height 11. Acc. 342 1. CS-137
would discriminate early maturing and 12. Acc. 343 2. CS-143
dwarf varieties which tend to be suscep- 13. Acc. 353 3. CS-174
tible. It seems that the best approach in 14. Acc. 384 4. Acc. 54:
assessing the true level of resistance in 15. Acc. 412 5. Acc. 68:
sorghum is to compare reactions of lines 16. Acc. 420 6. Ace. 74(
within a given group of plant height and 17. Ace. 429 7. Acc. 74:
maturity in cases where field screening is 18. Acc. 503 8. Acc. 74:
dependent on natural inoculum. 19. Acc. 543 9. Acc. 74,
Screening for disease resistance using 20. Acc. 546 10. Acc. 745
natural inoculum is also complicated by 21. Acc. 568 11. Acc. 76!
,.L- *_--.--- TT-.. . . ,, .r -- ')' A -- CQ2 1I' A *- '71








6 Philippine Pytopathdo Vol. 17


C. Gray Leaf Spot D. Tar Spot
1. Ace. 771 5. CS-348 1. Ace. 988
2. IS 10288 B 6. Tx-2720 2. Ace. 2059
3. CS-269 7. Tx 2733
4. CS-290








n&It. ~ L- .at^ I.. AM -


FIELD EVALUATION OF DIFFERENT FUNGICIDES AS SEED
TREATMENT FOR THE CONTROL OF SEED ROT AND DAMPING-
OFF DISEASES OF COTTON CV. DELTAPINE 16

R. G. DAVIDE and E. B. BATINO

Associate Professor and Research Assistant, respectively, Department of Plan
Pathology, College of Agriculture, University of the Philippines at Los Bafios, College
Laguna.
This study was supported by the National Crop Protection Center and Cotto
Research and Development Institute.

ABSTRACT

Seven fungicides were evaluated as seed treatment for the control of seed rot
and damping-off diseases of cotton cv. Deltapine 16. All treated and non-treated seeds
were subjected to "flood test" by submerging them in water for 5 days in plastic tum-
blers before planting in the field.
All the fungicides tested significantly increased germination, stand and yield of
cotton plants. Percentage increase in stand at harvest ranged from 4.5 to 68.3% while
the yield increase ranged from 20.9 to 68.9% as compared with the controL In terms
of yield, the best treatments were Vitavax-Thiram and Zincofol which gave 68.9 and
68.0% yield increase, respectively. These were followed by treatments of Vitaxax-
Captan, Homai, Captan, Brassicol and Difolatan.


Cotton growers in this country have gave 18% increase in stand and 5.7% ii
been experiencing poor germination of crease in yield. On the other hand, Ibrn


ul* Jllu vlJ LbV flUll J Sow l. flUb I11SI I,
due to the attack of fungi causing seei
rot and damping off diseases. Since mos
of these fungi are water-loving, the plant
ing of cotton seeds during this period
could make the seeds and seedlings mor
vulnerable to the attack. It is, therefore
necessary that cotton seeds should b
protected against these diseases before
planting.
Studies abroad revealed that treating
cotton seeds with fungicides prior tb
planting in the field could prevent seec
rot and damping-off resulting in a signi
ficant increase in stand and yield (Ran
ney & Burchfield, 1967; Pulido & Bolton
1974). Arndt (1935) reported that treat


nificantly reduced seed rot and result
in an increase of 22.6 percent in yiek
Blackman (1977) also observed that Bi
san 30EC, Vitavax-Thiram and Vitavaw
Captan significantly improved cotto
seed germination.
This study was conducted primarily t
evaluate the effectiveness of a number c
fungicides, which passed the greenhouse
"flood test", in protecting cotton seed
against seed rot and damping-off under
field conditions and to determine th
effect of fungicide seed treatment o
stand and yield of Deltapine 16 cottor

MATERIALS AND METHODS
,rl-- ..--.---- ..... --a-..-A.-A 4- J.









?Itippdam P4ytpad"olo


College Central Experiment Station loca-
ted near the Institute of Plant Breeding.
The area was thoroughly prepared and
divided into 5 blocks at 2 m apart and
each block was subdivided into 8 furrows
at 1 m apart and 20 m long. The exper-
imental design used was a randomized
complete block with 5 replication and
8 treatments including the control.
Seven fungicides, viz., Zincofol, Vita-
vax-Thiram, Vitavax-Captan, Captan,


Homai, Brassicol and Difolatan 4F were
tested. They passed the greenhouse screen-
ing using "flood test" (Davide & Batino,
1979). Five hundred grams of undelinted
cotton seeds Deltapine 16 were used for
each chemical treatment and the control.
The manufacturer's recommended rate
for each chemical was used and applied
employing the dust method except for
Difolatan 4F, a liquid, which was applied
as slurry (Table 1). The seeds for treat-


Table 1. List of fungicides used, rate of application and manufacturers.

Rate
FUNGICIDES g/kg ACTIVE INGREDIENT MANUFACTURER
seeds


Zincofol


Vitavax-Thiram


Captan


Homai


Difolatan 4F



Brassicol


1.9 [50% cis-N- (1,1,2,2-tetra-
chloroethyl) thio-4-cyclohe-
xene-1,2-dicarboximide] +
[12% copper] + [6% zinc]

5.0 [37.5% 2,3-dihydro-6-methyl-
5-phenyl carbamoyl 1-1, 1,4-6
oxathiin] + [37.5% N] (Tri-
chloromethyl) thio-4-cyclo-
hexane

2.8 [50% N [Trichloromethyl)
thio] -4-cychlohexane-1,2-
dicarboximide]

1.3 [50% (1,2-Bis (3-methoxy
carbamoyl-2-thioureido) ben-
zene] + [30% Bis (dimethyl
thiocarbamoyl) disulfide]

3.0 cc [39% Cis-N-(1,1,2,2-tetra-
chloroethyl)-thio-4-cyclo-
hexene-1, a dicarboximide]

4.0 [75% Pentachloronitro ben-
zene]


Chevron Chem.
International
Inc.


Uniroyal Agricul-
tural Chem., Div.
of Uniroyal, Inc.
Elmira, Ontario


Chevron Chem.
International
Inc.

Nippon Soda Comp.
Ltd. Tokyo,
Japan


Chevron Chem.
International
Inc.

Hoechst Phil.


VoL 17









Seed Treatment Aginst Cotton Diseses


ment were placed in bell jars and tho-
roughly mixed with the chemical by
shaking the jars until the seeds were
fully coated. Treated seeds were separate-
ly placed in plastic bags and kept for 3
weeks in the laboratory at 20-25 C. These
treated seeds were not planted directly to
the field. Instead they were subjected
to the "flood test" in the laboratory.
Two hundred fifty seeds were counted
for each of the five replications per
treatment, wrapped in a gauze cloth and
were separately placed in plastic tumblers,
filled with tap water, and supported with
a wire screen to prevent floating of the
wrapped seeds. The seeds of both the
treated and non-treated (control) were
kept under this submerged condition for
5 days prior to planting them in the field.
Planting in the field was done by sow-
ing the "flood" treated and non-treated
seeds into the assigned furrows. Five
seeds were sown per hill at 2.5 cm deep
and 40 cm apart. Each row had 50 hills.
Two weeks after germination, the
plants were fertilized with ammonium
sulfate (21-0-0) at 90 kg/ha and com-
plete fertilizer (14-14-14) at 210 kg/ha
was applied before balling stage. After
60 days, it was sidedressed with ammo-
nium sulfate. Other cultural practices
such as cultivation, weeding and water-
ing were done whenever necessary.
Insects (thrips, bollworms, aphids,
leafhoppers, etc.) were controlled by
spraying either with Sevin 80S, Thiodan,
Azodrin or Vydate. They were sprayed
at the recommended rate. For control-
ling Ascochyta blight and Alternaria
leaf spot, Difolatan 4F at 188 ml/100
1 was used.
Stand count was recorded every 5-
day interval up to 90 days. The final
stand count was done after harvest of
seed cotton. The first priming was done


when about 50% of the balls had bursted
and the second was made when the re-
maining balls had all bursted. The har-
vested seed-cotton from each replicate
was placed in plastic bags and weighed.
Later the weights of the 5 replicates for
each treatment were summed up to
obtain the total yield per treatment. The
data on stand and yield were statistical-
ly analyzed for significant difference of
treatment means.

RESULTS AND DISCUSSION

Effect on germination and stand.
The results are summarized in Tables
2 & 3. Data on stand counts taken 30
days after planting showed that the
different fungicides had invariably and
significantly improved the stand of cot-
ton plants (Fig. 1). Seeds treated with
Zincofol gave the highest percentage
increase in stand (73.7%) followed by
Vitavax-Thiram (60.6%) Vitavax-Captan
(58.9%), Captan (43.9%), Homai (60.9%),
Difolatan (40.2%) and Brassicol (6.7%)
Table 2). The data clearly indicate that
the chemical treatments have significantly
protected the seeds against decay, thus
improving the percentage germination of
the seeds.
Stand counts at the end of the exper-
iment revealed that in most treatments
there was a slight reduction in percent-
age stand as compared with the 30-day
stand counts. For instance, in Zincofol
treatment, a 5.4% stand reduction was
observed; in Difolatan treatment there
was a decrease of 9.1%, Vitavax-Thiram
13.5%, Captan 1.6% and Brassicol 1.5%
whereas there was only 1% increase in
stand in Vitavax-Captan. Some of these
plants may have died due to insect or
disease damage. However, the effect
of the treatment on the stand at harvest
time was still statistically significant.


Jan. & June 1981








Table 2. Stand counts 30 days after sowing undelinted Deltapine 16 cotton-seeds treated with different fungicides and submerged in
water (flood test) for 5 days before planting in the field.


REPLICATION a PERCENTAGE
TREATMENT I I III IV V TOTAL MEAN INCREASE


Zincofol 132 129 138 115 108 622 124.40 73.74
Vitavax-Thiram 96 109 141 114 115 575 115.00 60.61
Vitavax-Captan 81 132 132 130 94 569 113.80 58.94
Captan 84 97 132 128 74 515 103.00 43.85
Homai 87 138 138 90 123 576 115.20 60.89
Difolatan 100 107 69 99 127 502 100.40 40.22
Brassicol 77 70 76 69 90 382 76.40 6.70
Control 65 56 86 78 73 358 71.60

L. S. D. .05 24.92
.01 32.27


a 250 seeds were used per replication of a treatment.








Table 3. Stand counts at harvest time (165 days after sowing) of Deltapine 16 cotton emds treated with different fungicides and sub-
merged in water (flood test for 5 days) before planting in the field.


REPLICATION PERCENTAGE
TREATMENT II III IV V MEAN INCREASE


Zincofol 122 120 115 103 97 111.4 68.3
Homai 78 131 141 69 113 106.4 60.7
Vitavax-Thiram 80 110 126 89 82 97.4 47.1
Vitavax-Captan 68 96 130 121 69 96.8 46.2
Captan 79 91 110 126 65 94.2 42.3
Difolatan 84 90 61 98 101 86.8 31.1
Brassicol 73 60 68 61 84 69.20 4.5
Control 57 51 83 73 67 66.20

L. S. D. 0.05 25.75
0.01 34.74














VIT3X [HIRAM
























Figure 1. Plant population density of Delt
through "flood test" prior to pi
onv fungicides.


ie cotton from seeds treated with Vitavax-
ing in the field. Note the low stand in the









mmd Trnmhnm* Awmhi. (n,*


Zincofol treatment still gave the high
percentage increase in stand (68.3%
followed by treatments ofHomai (60.79
Vitavax-Thiram (47.1%), Vitavax-Capti
(46.2%) (42.3%), Difolatan (31.1%), ar
Brassicol (4.5%) (Table 3).
Effect on cottonseed yield. TI
yield data summarized in Table 4 clearly
showed that the increase in stand resulted
in a highly significantly increase in cotton
seed yield (Fig. 2). Vitavax-Thiram as




































Fig. 2. Effects of the different seed 1
vionl7 nf 7ftlnins 7j ,nfnn n.n


Zincofol treatments gave the high
yield increase of 68.9 and 68%, respe
tively, over the control treatment. Th4
were followed by treatments of Vitava
Captan with a yield increase of 57
Homai 46.3%, Captan 35.7%, Brassic
25.4%, and Difolatan 20.9%. The da
however, indicated that some treatment
with high stand counts did not corre
pondingly gave high yield. For instance
Homai treatment had a 60.7% increase




































rtment fungicides under "flood test" on th,









'Table 4. xrlea i


RATE
TREATMENT (oz/100 lbs.
seeds)


Vitavax-Thiram 8
Zincofol 3
Vitavax-Captan 8
Homai 2
Captan 4.5
Brassicol 6.4
Difolatan 4.5
Control

L. S.D. 0.05
0.01


aMean yield in 1 x 20-meter area.


REPLICATION AND WEIGHT (KG) OF S

I II III IV


3.23 5.58 4.78 4.0
4.38 4.61 4.23 3.9
4.19 4.10 5.05 3.0
2.33 4.61 4.60 2.6
3.54 3.43 4.10 3.2
3.19 3.77 3.04 2.8
2.75 3.60 2.36 2.6
2.40 2.16 2.43 2.4


: 10 cUnuon reslu









Treatment Aainst I


final stand and gave only 46.3% yie
increase while Vitavax-Captan had 47.1
stand increase but gave a yield increase
57.0%. The same situation exists wi
treatments of Brassicol and Difolata
This would mean that there are oth
factors, which we do not know exact
yet, that could influence the plants
yield more even though at relatively lo
stand count or the chemical may ha
some subchronic or slight toxicity effe
enough to affect flowering. This merit
an investigation.


Fig. 3. Field view of the Deltapine 16 cotton fungicide seed treatment experiment at
the College of Agriculture Central Experiment Station, College, Laguna


Jan. & June 1H












LITERATURE CITED

RNDT, C. H. 1935. A resume of cotton seed treatment in South Carolina. Phytopatho-
logy 25: 970.

LACKMAN, C. W. 1977. Results of regional cotton seed treatment test in South Caro-
lina, 1969. Fungicide and Nematicide Test 32: 170.

AVIDE, R. G. and E. BATINO. 1979. Laboratory screening of fungicides for cotton
seed treatment against seed rot and damping off diseases. Progress report Cotton
Research & Development Institute. p. 1-9.

IRAGINOV, S.H.I. 1965. Use of chemical preparation against rotting of cotton seeds.
In RPP 46 (3): 130.

EUKEL, R. W. 1953. Treating seeds to prevent diseases. In Plant Diseases. USDA
Yrbk. [Agr.] 1953: 134-135.

JLIDO, M. L. and R. A. BOLTON. 1974. A non-mercurial treatment for cotton seed.
PANS 20 (2): 251-254.

ANNEY, C.D. and E. G. BURCHFIELD. 1967. Evaluation of seed treatment with 1,4-
dichloro-2,5-dimethoxy-benzene as a cotton seedling disease control measure. Plant
Dis. Reptr. 51: 558-568.


lu__t-_ L~IIL___~









tfushyy. 5j1 tu9


EtY ECTIS OF NEMATICIDES ON NEMATODE POPULATION
AND YIELD OF POTATO IN ATOK, BENGUET

R. G. DAVIDE and R. A. ZORILLA

Respectively, Associate Professor and Research Assistant, Department of Plai
Pathology College of Agriculture, University of the Philippines at Los Bafios, Colleg
Laguna, Philippines.
Supported by NCPC Vegetables Pests Management Program research fund. TI
assistance of Mr. R. Ong in providing the experimental area is gratefully acknowledges

ABSTRACT

Results of two experiments conducted in a potato farm in Atok, Benguet,
showed that nematodes such as Pratylenchus sp., Trichodorus sp., Tylenchorhynchus
sp., Rotylenchulus sp., and Helicotylenchus sp. were effectively controlled by nemati-
cide treatments applied in furrows at planting time. Consequently, yields of potato vars.
Jaerlan and Fina were significantly increased by the treatments. The highest yield in-
crease (21-68%) was obtained in Mocap 5G at 6 kg a.L/ ha treatment followed by
Temik 15G (19-45%) and Furadan 3G (12-35%). The data also showed that the effects
of four different rates of application of Mocap 5 G vary with the nematode counts and
yield. Although there was a corresponding reduction of nematodes as the rate of
application was increased, the yield tended to decrease when the rate of application
was increased beyond 6 kg a.i./ha indicating phytotoxicity.

Potato is grown widely in Benguet and (Dickerson et al., 1964; Boparai an


of Eastern Visayas and Mindanao, partic
ularly in the provinces of Bukidnor
Davao del Sur and South Cotabatc
According to the 1977 report of th
Bureau of Agricultural Economics, there
were over 3,490 ha planted to potato a
over the Philippines. Total production
in 1977 alone was reported to be 20,37
T with an average yield of 5.84 T/hi
However, there were considerable losses
in yield during the cropping season
which could be attributed to a number c
factors and among which were pests an
diseases. One of these pests was the nems
tode. It has been demonstrated abroa
that nematodes such as Globodera rostc
chiensis, Pratylenchus spp., Meloidogyn
spp., Tylenchorhynchus spp., Trichodc
rus spp. and others could attack potat
resulting in significant yield reduction


Bolander and Santo, 1977: Brown an
Riedel, 1978; Hoestra and Harshagei
1978; O'Brien, 1978; Santo et al., 198
and Weingarthur et al., 1980). In a nern
ticide test conducted by Bolander an
Santo, evidence was obtained that tt
most effective chemical against Melo
dogyne were Nemacur and Vydate resul
ing in high yield increase of potato tuber
The same result was obtained by O'Brie
(1978) who found Temik and Furada
to reduce Globodera infection consider
ably resulting in increased yield.
In the Philippines, preliminary studio
had been conducted on the control
nematodes attacking vegetables such
tomato, cabbage and potato and the fin'
ings indicated that some nematicides ca
effectively control the nematodes (Mi
damba et al.. 1967: Davide and Comedi









B Philippine Phytopathology Vol. 17


972). The chemical treatments usually Thereafter, the farmer-cooperator applied
:sulted in a 20-50% increase in yield of the usual cultural practices for the potato
iese crops. production in the area which include
Results of preliminary trial in 1973 by adequate fertilization and control of
ie senior author indicated that nemati- potato blight and other diseases as well as
ide treatment of potato farms in Atok, weeds and insect pests.
enguet could increase the yield of the To monitor the nematode population,
rop. However, there was no thorough soil samples (400 cc) were taken from
valuation on the effect of the chemical each plot before and after treatments and
against the nematodes. This study, there- subsequent samplings were made at least
ore, was primarily conducted to evaluate two times before harvest. In each plot,
le effectiveness of three nematicides, soil samples were taken 3-6 in deep at 3
iz., Temik 15G, Furadan 3G and Mocap sampling sites. The soil samples from each
G at four different rates of application plot were placed in a plastic bag and were
against nematodes affecting potato in brought to the nematology laboratory
.tok, Benguet. of the Department of Plant Pathology,
College of Agriculture, U. P. at Los Bafios
MATERIALS AND METHODS for nematode analysis using the sieving-
funnel method of extraction. Yield data
Two experiments using a randomized were taken at harvest time by weighing
lock design with four replications, were separately the first, second and third class
inducted in the potato farm of Mr. potato tubers harvested from each
,omy Ong of Paoay in Atok, Benguet plot. The third class tubers were relative-
uring the two cropping seasons of 1980- ly small and considered non-marketable.
981. The following nematicides were All classes of potato were included in
ssted: Temik 15G (15% 2-methyl-2 the data for total yield.
nethylthio) propionaldehyde 0- (methyl








Nematode Control on Potato


Table 1. Mean nematode counts and percentage control due to nematicide treatments.

NEMATODEa COUNTS PER 400 SOIL SAMPLE
TREATMENT RATE Pre- 1st % 3rd %
(kg a.i./ha) treatment Month Control Month Control

MOCAP G 4 418.9 139.9 67.6 159.6 61.9
MOCAP G 6 479.7 98.2 79.5 115.1 76.0
MOCAP 5G 8 495.8 59.5 80.1 87.3 82.7
MOCAP 5G 10 384.6 44.8 88.4 63.0 83.6
FURADAN 3G 4.5 505.5 163.3 67.7 209.6 58.5
TEMIK 15G 7.5 516.1 35.4 93.1 51.2 90.1
CONTROL 518.4 931.4 998.8 -

aThe predominant genera were Pratylenchus, Trichodorus, Tylenchorhynchus,
Rotylenchulus and Helicotylenchus.


the reduction of nematode population
in the soil may be due to starvation and
subtoxicity of the chemical.
Effect of the treatment on yield.
The data summarized in Table 2 generally
showed highly significant yield increase
in the nematicide-treated plants as com-
pared with the non-treated or control
plants in both Jaerlan and Fina varieties.
In the first trial, the highest yield increase
in the first class tubers was in Mocap 5G
at 6 kg ai./hawhichis only 33.5%, where-
as in the second trial the highest yield in-
crease of the same treatment was 90.29%.
Temik-treated plants had a yield increase
of 30.20-75.37%, Furadan 3G gave
27.15-57-91% yield increase of the first
class tubers while Mocap 5G at 4 kg a.i./
ha gave 20.92-46.72%, Mocap 5G at 8
kg ai./ha showed 2.38-27.07% increase
and at the rate of 10 kg ai./ha, it had
13.90-29.03% yield increase. The same
trend of results could be observed for
yield increase in the second class tubers
except that of Furadan-treated plants
which gave the lowest increase of only
17.31% in the second trial.


Data in Table 3 showed that the treat-
ments resulted in significant increase in
yield ranging from 13.6%-21.6% in the
first trial using var. Jaerlan and 22.7 to
67.7% on Fina var. in the second trial.
The highest increase in yield in the first
trial was obtained in Mocap 5G at 6 kg
a.i./ha. This was followed by Temik 15G,
then the other three rates of Mocap 5G
and Furadan 3G having the least yield
which is still higher than the control.
In the second trial, the same trend of
results was obtained except that of Fura-
dan 3G-treated plants which yielded
more than those of Mocap 5G at 4, 8
and 10 kg a.i./ha. Based on nematode
control, Temik 15G was the most effect-
ive followed by Mocap 5G at four rates
and Furadan 3G, the least effective.
There was no significant difference
among Mocap 5G treatments at 4,8 and
10 kg a.i./ha and that of Furadan 3G and
between Temik 15G at 4.5 kg a.i./ha and
Mocap 5G at 6 kg a.i./ha. However, pota-
to yield from treatment of Mocap 5G at
6 kg a.i./ha differed significantly from
that of Furadan 3G and the other three


Jan. & June 1981









Philippine Phytopathology


Table 2. Mean class yield (kg) and percentage increase of potato vars. Jaeran and Fina
during two cropping seasons, 1980-1981 in Atok, Benguet.



T R I A L Sa
TREATMENT AND RATE I II
CLASS YIELD (kg a.i./ha) Jaerlan Percent Fina Percent
1980 Increase 1981 Increase


MOCAP5G
1st
2nd

MOCAP5G
1st
2nd

MOCAP5G
1st
2nd


9.13
5.73


7.73
6.88


20.92
0


2.38
16.61


8.43 11.66
6.72 13.90


FURADAN 3G
1st
2nd

TEMIK 15G
1st
2nd

CONTROL
1st
2nd


9.60
5.90


9.83
5.90


27.15
0


30.20
0


9.83
7.63


838
5.55


928
5.20


10.58
6.60


11.75
6.60


46.72
89.33


27.07
37.72


38.51
29.03


57.91
63.77


75.37
63.77


- 6.70
- 4.03


aData of each trial are means (kg) of 4 plot replicates.


rates of the same nematicide. All nemati-
cides tested were effective against the
nematodes and significantly increased the
yield, although Mocap 5G at 8 and 10 kg
a.i./ha yielded less potato tubers than at
lower concentration of the same treat-


ment. This might be due to some degree
of phytotoxicity of Mocap at higher
rates. Mocap, Furadan and Temik have
been shown abroad to be also effective
against root-knot nematode, M. incognita
Chitwood, G. rostochiensis and P. pene-


Vol. 17








Nematode Control on Potato


trans on potato resulting in a significant
increase in yield (Cetas, 1971;Radewald,
et al., 1975;and Brodie, 1980), respective-
ly.
The present study shows that it is
economical or profitable for potato
growers, particularly those who are en-


gaged in large scale production to use
nematicides for the control of plant
parasitic nematodes resulting in increased
crop yield and improved quality of tubers
which could command a relatively higher
market price.


Table 3. Effects of nematicide treatments on the mean (kg) and percentage yield increase
of potato vars. Jaerlan and Fina during the two cropping seasons, 1980-1981 in
Atok, Benguet.


T R I A L Sa
TREATMENT RATE I II
(kg a.i./ha) (Jaerlan) Percent (Fina) Percent
1980 Increase 1981 Increase


MOCAP 5G 4 16.5 (121)b 18,7 16.6 27.7

MOCAP 5G 6 16.9 (1.23) 21.6 21.8 67.7

MOCAP5G 8 16.2 (1.20) 16.5 15.9 22.7

MOCAP5G 10 16.1 (1.20) 15.8 16.0 23.3

FURADAN 3G 4.5 15.8 (1.19) 13.6 17.5 34.6

TEMIK 15G 7.5 16.6 (1.22) 19.4 18.9 45.4

CONTROL 13.9 (1.14) 13.0

LSD

.05 (0.04) 2.67

.01 (0.08) 3.25



aData of each trial are means (Kg) of 4 replications of 1 x 4-meter plot.
bNumber in parentheses are transformed log of raw data used in statistical analysis.


Jan. & June 1981









62


LITERATURE CITED

BOLANDER, E. J. and G. S. SANTO. 1977. Elimination ofMeloidogyne hapla in pot!
seed-pieces with phenamiphos dip treatment. Plant Dis. Reptr. 61: 743-465.

BOPARAI, J. S. and N. M. HAGUE. 1974. The response of potato cyst nematode,He
rodera rostochiensis and root-knot nematode Meloidogyne incognita to Dov
275. J. Nematol. 6: 136.

BRODIE, B. B. 1980. Control of Globodera rostochiensis in relation to the method a
time of application of nematicides. J. Nematol. 12: 215-216 (Abstr.).

BROWN, M. J. and R. M. RIEDEL. 1978. Patylenchus spp. associated with Solani
tuberosum cv. 'Superior' in Ohio. J. Nematol. 10: 282 (Abstr.).

CETAS, R. C. 1971. Evaluation of granular formulation of systemic nematicides
the control of Pratylenchus on potatoes. Phytopathology 61: 887 (Abstr.).

DAVIDE, R. G. and A. COMEDIS. 1972. Chemical control of nematodes on cabbage
Atok, Benguet. Philipp. Agr. 55: 282-288.


population trends of Pratylenchu
322.

DI SANZO, C. P. 1973. Nematode respo

O'BRIEN, P. C. 1978. Effect of carb
ment of Globodera rostochiensis ii

RADEWALD, J. D., O. A. HARVEY, ]
report on control of root-knot i
nematicides. Calif. Agr. 29: 8-9.

SANTO, G. S., S. H. BANNON and H.
parasitizing potatoes in the Pacif

WEINGARTHUR, D. P., G. C. SMART,
of trichodorids nematode in Flori
Nematol. 12: 241 (Abstr.).


n potato and corn. Phytopathology 54: 31


to carbofuran. J. Nematol. 5: 22-27.

ran, aldicarb and resistant host on devel
itato. J. Nematol. 10: 296 (Abstr.).

1HIBUYA and S. NELSON. 1975. A progn
iatodes on white rose potato with granul


SFINLEY. 1980. A new root-knot nemato
Northwest. J. Nematol. 12: 236-237 (Abstr

I R. SHUMAKER. 1980. Population dynamic
Irish Potato soils following soil fumigation.





SCREENING OF T1
FOR BACTERIAL

R. G. ATABUG a

Assistant Plant Pathologist and Sen
Research Center, Madaum, Tagum, Davao

ABI

Sixteen tomato accessions of T'
from the Asian Vegetable Research and
for resistance to Pseudomonas solanacea
tested, six accessions were rated resistan
susceptible and six, susceptible. The resi
(4-9 days) than the susceptible accession
took more days to produce 10% wilted
ions (5-6 days). The resistant accession
of medium size and red in color when
green-shouldered fruits.

Bacterial wilt caused by Pseudomonas
solanacearum E. F. Smith, is one of the
most destructive diseases of tomato and
many other economic crops in the world.
Various measures to control the disease
have been reported (Madramootoo, 1957;
Sequiera, 1958); however, none can equal
the use of resistant varieties against the
disease. Tomato varieties with resistance
to the wilt pathogen have been reported
by several workers (Acosta et. al., 1964;
Gilbert et al., 1974; Henderson and Jen-
kins, 1972). Unfortunately, tomato varie-
ties and lines resistant toP. solanacearum
in one area have been reported as suscep-
tible to strains of the pathogen in other
areas with high ambient temperature
(Rao et al., 1975; Sonoda and Augustine,
1978). Hence, tomato accessions, with
some desired agronomic characteristics
and observed to possess tolerance to P.
solanacearum in the seed multiplication
field plots, were evaluated for resistance
to local strains of the pathogen under
local climatic conditions inside a screen
AnoA


IATO ACCESSIONS
MILT RESISTANCE

1 M. O. SAN JUAN

Plant Pathologist, respectively, Twin Rivers
1Norte.

PACT

Rivers Research Center mostly obtained
development Center (AVRDC), were screened
i inside a screenhouse. Of the 16 accessions
three, moderately resistant; one, moderately
nt accessions had longer incubation period
3-4 days). Likewise, the resistant accessions
nts (8-19 days) than the susceptible access-
:oduced locally acceptable fruits that were
e; however, accessions 77 and 145 yielded


The study was conducted at the Eden
Research Laboratory, Toril, Davao City
from October, 1978 to February, 1980.

MATERIALS AND METHODS

Sixteen tomato accessions, mostly ob-
tained from the Asian Vegetable Research
and Development Center (AVRDC), were
evaluated for resistance to P. solanacea-
rum inside a screen house where ambient
temperature fluctuated between 26-34C.
Tomato seeds were sown in plastic trays
(2 x 2 x 0.5 ft) containing heat-sterilized
manure-topsoil medium. Two-week old
seedlings of each accessions were trans-
planted at the rate of 16 seedlings per
tray, replicated four times, and repeated
twice.
Isolates of P. solanacearum were col-
lected from diseased tomato, eggplant,
and potato plants at different locations in
Eden. Virulent colonies were selected on
Kelman's (1954) TTC medium (10 g.
dextrose, 10 g peptone, 1 g casein hydro-
lieat. 1in m 4 trinhanvltAtrzan.









Phlippine Phytopathology


lium chloride (0.5% solution), 18 g agar,
1000 ml distilled water). No attempt,
however, was made to identify the differ-
ent bacterial strains. Stock cultures
were maintained in sterile distilled water.
Inoculum was prepared from 48-hour-old
colonies of 5 isolates on TTC medium.
Inoculum density was approximately
1 x 107 bacterial cells/ml. Three inocula-
tions using the scalpeled-petiole tech-
nique (Quimio, 1976) were made at in-
tervals of 3-5 days on four-week-old to-
mato plants.
After the last inoculations, wilted
plants were counted weekly for three
consecutive weeks. The incubation period


and the LT10 (no. of days required to
produce 10% wilted plants) of each ac-
cession were also recorded.

RESULTS AND DISCUSSION

The incubation period, the LT10,
the percent mortality and the reaction
of the tomato accessions are given in
Table 1. Of the 16 accessions tested, 6
accessions were resistant; 3 moderately
resistant; 1 moderately susceptible; and 6
susceptible. Varying reaction was ob-
served in some accessions. However,
among the resistant accessions only ac-
cession 77 (VC-9-1-2-9B/Venus/Kewalo)


Table 1. The different tomato accessions and their resistance ratings to bacterial wilt.


TRRC Acc Varietal Incubation LT10 % Mortality Reactiona
Number Name period (days) (days)

01 Campbell 28 (F) 3 5 72.13 S
13 Tamu Chico III 4 5 93.10 S
14 VC-11-1-2-1B 3 5 91.76 S
19 VF Roma 3 5 95.45 S
29 Sub-Arctic plenty 3 5 73.40 S
48 502-F5-60 3 8 22.98 MR
77 502 F5-89 4 8 17.98 R
90 502 F5-52 4 6 70.82 S
142 122-0-1-1-0-0 9 17 13.26 R
145 8d-0-7-1-0-0 7 14 7.88 R
148 143-0-4B-1-0-0 6 15 11.35 R
156 143-0-4B-1-0-0 6 19 10.47 R
163 1 d-0-2-4-0 3 6 48.46 MS
166 Pope 4 11 12.09 R
170 Apple 4 8 33.02 MR
349 Lycopersicon 3 10 30.15 MR
pimpine'lfolium


R =
MR =
MS =
S =


Resistant, < 20% plants wilted
Moderately Resistant, 20-40% plants wilted
Moderately Susceptible, 41-60% plants wilted
Susceptible, > 60% plants wilted


Vol. 17


























The resistant accessions had longer Twin Rivers Research Center tomato
incubation periods (4-9 days) than the accessions, which bear locally acceptable
susceptible accessions (3-4 days). Simi- fruits, have high levels of resistance. Fur-
larly, the resistant accessions took more their tests are needed to determine the
days to produce 10% wilted plants than fruit-setting rate and the reaction of the
the susceptible accessions. The LTI0 of resistant accessions to P. solanacearum
the resistant accessions ranged from 8-19 under lowland conditions not only in
days while that of the susceptible acces- Mindanao but also in the Visayas and
sions ranged from 5-6 days. Differences, Luzon.



LITERATURE CITED

ACOSTA, J. C., J. C. GILBERT, and V. L. QUIRON. 1974. Heritability of bacterial will
resistance in tomato. Proc. Am. Soc. Hort. Sci. 84: 455-462.

GILBERT, J. C., J. S. TANAKA, and K. Y. TAKEDA. 1974. 'Kewalo' Tomato, Hort
Sci. 9: 481-482.

HENDERSON, W. R. and S. F. JENKINS, JR. 1972. Venus and Saturn, N. C. Agric
Expt. Sta. Bull, 444. 13 pp.

KELMAN, A. 1954. The relationship of pathogenicity in Pseudomonas solanacearum t(
colony appearance on a tetrazolium medium. Phytopathology 44: 693-695.


Tn & T.n. 10 1


Il~kkrl Wilt Pddaru


changed from moderately resistant in the
first trial to resistant in the succeeding
two trials. The disease reaction of access-
ion 77 was apparently altered by high
ambient temperature during the first trial.
Loss of resistance by Venus and VC-9-1
under hot, humid conditions was report.
ed by Mew and Ho (1976). In addition,
Sonoda and Augustine (1978) reported
that BWN 21 (Kewalo/Venus) was suscep-
tible in one test; however, it produced


among the resistant accessions, in incuba-
tion period (4-9 days) and LTI0 (8-19
days) indicate that resistance could either
delay the initial infection of the disease
or slow down the rate of wilting once the
initial infection is established (Mew and
Ho, 1976).
The resistant tomato accessions yielded
locally acceptable fruits which were of
medium size and red in color when ripe;
however, accessions 77 and 145 produced


%W &v WV9Q9. -V*. Zrb^RWV A -^ -'^ I^w

isistance to bacterial wilt in tomato. Pit. Dis


rapid inoculation technique for tomato bac
12:8 (Absts.)


MEW, T. W. and W. C. HO. 1976.Variet
Reptr. 60: 264-268.

QUIMIO, A. J. and F. R. PRADO. 1976
trial wilt screening. Phil. Phytopatt









Philivpine Phytopathology


AO, M. V. B., H. S. SOHI, and S. K. TIKOO. 1975. Reaction of wilt-resistant tomato
varieties and lines to Pseudomonas solanacearum in India. Pit. Dis. Reptr. 59:
734-736.

EQUIERA, L. 1958. Bacterial wilt of bananas: dissemination and control of the disease.
Phytopathology 48: 64-69.

3NODA, R. M. 1978. Effect of differences in tolerance of tomato to bacterial wilt. Pit.
Dis. Reptr. 62: 1059-1062.












DEVELOPMENT OF INOCULATION TECHNIQUE AND VARIETAL
REACTION TO SHEATH ROT OF RICE

C. A. RAJU and R. A. SINGH

Formerly Ph.D. student and Associate Professor, respectively, Department ol
Plant Patholoy, G. B. Pant University of Agric. and Technology. Pantnagar 263145,
India.
Present address: Scientist 1, Central Plantation Crop Research Institute, Kerala,
India and Senior Post-Doc. Fellow, Dept. of Plant Pathology, IRRI, P.O. Box 933, Ma-
nila, Philippines, respectively.

Financial support in the form of Junior and Senior Research Fellowships awarded
to the senior author from the Council of Scientific and Industrial Research, New Delhi
is gratefully acknowledged.

ABSTRACT

Injecting the spore suspension and placing two infested pearl millet grains in the
flag leaf sheath resulted in maximum development of sheath rot of rice caused by
Sarocladium oryzae (Sawada) Gams and Hawks. The best stage for inoculation was
7-9 days before panicle emergence. Forty-six cultivars including few donors of bacterial
leaf blight resistance were screened against the disease during Kharif 1976 and 1977 by
artificial inoculation under field conditions. Five entries, namely: Bas 370, Chinsurah
Boro II, Homthong, Sigadis and TKM 6 were found to be resistant, 28 moderately
resistant, 8 moderately susceptible and 5 susceptible.


Sheath rot of rice caused by Sarocla- grey centre which gradually enlarge and
dium oryzae (Sawada) Gams and Hawks cover the entire leaf sheath. The panicle
was first reported from Taiwan (Sawada, may exsert partially, bearing chaffy and
1922). In India, it was first reported from distorted grains or may be completely
Southern States in 1974 as a minor di- choked (Ou, 1972; Chakravarty and Bis-
sease (Amin et al., 1974) but in a very was, 1978). Few reports on varietal re-
short period, it became widespread in action under natural conditions have ap-
Andhra Pradesh (Aminetal., 1974;Reddy peared in the literature, but not much
et al., 1974), Kerala (Nair and Rajan, work has been done on the standardiza.
1976), Orissa (Naik and Roy, 1975), Ta- tion of inoculation technique and varietal
mil Nadu (Ahamed et al., 1975; Subra- reaction after inoculation. In this paper,
manian & Ramakrishnan, 1975), Bihar the standardization of inoculation me-
and West Bengal (Amin et al., 1974; and thods and the varietal reactions are re-
Pal, 1975) and Uttar Pradesh (personal ported.
observation), causing significant losses in MATERIALS AND METHODS
yield.
The disease appears late in the season Method of inoculation
mainly on flag leaf sheath as oblong to Five inoculation methods, namely; in-
irregular lesions with brown margin and serting a) diseased leaf sheath pieces (0.25









8


mi); b) agar culture blocks; and c) 2 disease was scored after 2U days. During
rains of pearl millet culture in the flag Kharif 1976, three methods of scoring
eaf sheath; d) injecting 0.5 ml spore were used, namely: the IRRI scale
suspension in the flag leaf sheath and e) (IRRI, 1975), Amin's scale (Amin, 1976)
praying the spore suspension (500-600) and the scale described below:
pLss/ml) on the plants were done to
est their efficacy on the development of Score Description


Anupama, lET 3359, IR20, Jayanti and
Vijaya. One hundred tillers of a test varie-
ty were inoculated by each method. The
disease was scored 20-25 days after inocu-
lation.

Stage of inoculation
Two hundred tillers of each test varie-
:y were inoculated in the flag leaf sheath
approximately 6-7 days, 4-5 days and 2-3
lays before panicle emergence and at
flowering stage to determine the best
itage for inoculation and development
)f the disease. Scoring was done 20-25
lays after inoculation which were con-
rerted to disease index by summing all
the numerical ratings x 100 divided by
:he number of panicles scored x maxi-
num disease rating.

Varietal screening
Forty-six cultivars with resistance to
bacterial leaf blight were screened against
the disease by artificial inoculation under
field conditions during Kharif 1976 and
1977. Staggered planting of early-mid,
md late maturing varieties were done so
:hat all the entries come to flowering
simultaneously. Twenty-five day old seed-
ings of each variety were transplanted in
1 rows of 3 m length at a distance o' 20
mn x 15 cm in puddled field. All the
standard agronomical practices were fol-
owed in growing the crop. Inoculation
was done by placing two infested pearl
nillet grain in flag leaf sheath 4-7 days
beforee panicle emergence. One hundred
killerss of each entry were inoculated. The


2 1 or 2 small lesions on flag
leaf sheath
3 Less than 10% area of flag
leaf sheath infected
4 11 to 25% area of flag leaf
seat infected
5 26 to 50% area of flag leaf
sheath infected
6 51 to 75% area of flag leaf
seat infected
7 More than 76% of flag leaf
sheath infected
8 Partial choking of the panicle
in addition to 7
9 Complete choking of the pa-
nicle
Touring Kharif 1977, only the latter scale
ras used.

RESULTS AND DISCUSSION

method and stage of inoculation
Maximum and significantly higher di-
ease index was observed in plants in
,cted with spore suspension than those
loculated with the pearl millet culture.
'he disease index in the latter was sig-
ificantly higher than the disease index
i the remaining treatments. Disease
idices observed in the remaining me-
hods of inoculation were non-significant
among themselves (Table 1). Maximum
disease developed in plants inoculated
t 4-5 days followed by those at 6-7
ays before panicle emergence which
'ere non-significant with each other.
disease indices in the remaining treat-
ients were significantly less than the













vars.

Inoculation by
Infected Pearl Spore suspension
Varieties leaf sheath Agar millet
pieces culture culture injection spraying

Anupama 42.65 26.37 48.40 58.78 27.78
IET 3359 28.05 31.35 40.15 50.78 22.77
IR 20 38.61 28.00 42.63 55.67 23.81
Jayanti 30.36 24.53 43.11 47.71 18,02
Vijaya 29.67 25.11 40.89 56.00 16.78

Mean 33.87 27.07 43.04 53.79 21.83

LSD (.05) between methods of inoculation: 4.96

former treatments and were at par with to varying degrees by inoculating the
each other (Table 2). Though, the ma- pearl millet culture depending on the de-
ximum disease developed by injecting gree of inherent resistance of the variety.
the spore suspension, inoculation by Spraying of spore suspension on injured/
pearl millet culture was preferred over uninjured plants (Amin et al., 1974;
injection method. With the injection Reddy et al., 1974; Tasugi & Ikeda,
method, symptoms developed through- 1956) and stem-tape method in addi-
out the sheath, making the resistance tion to spraying (Amin et al., 1974) have
evaluation difficult. On the other hand, been used under glasshouse conditions,
discrete and typical lesions developed but these are not suitable for inoculation

Table 2. Sheath rot disease index using pearl millet culture inoculation at differed
growth stages on 5 rice cultivars.

Before panicle emergence
(days)
C Vars Boot leaf Panicle
stage 6-7 4-7 2-3 emergence

Anupama 34.48 60.70 74.64 46.08 28.04
IET 3359 24.31 45.01 55.35 30.25 20.56
IR 20 23.28 62.16 58.64 34.52 27.22
Jayanti 23.85 54.50 63.18 38.06 26.46
Vijaya 23.85 53.09 57.78 39.53 27.78

Mean 25.95 55.09 61.92 37.69 26.01

LSD (0.05) between inoculation at different stages: 12.51


~___ _____ I~rr____l __LL_~









70 Philippine Phytopathology Vol. 17


under field conditions. Estrada et al. Method of scoring and varietal reaction
(1979) found that insertion of a grain The disease ratings for all the entries
culture between leaf sheath and culm are given in Table 3. The data showed
produced severe and typical symptoms that disease reaction varied with the
while injection of the spore suspension methods of scoring (e. g. Chinsurah
prcaced atypical symptoms of Boro II was scored as susceptible on the
the disease, hence, confirms the present basis of percent tillers infected but re-
observation. sistant on the basis of lesions type). None


Table 3. Varietal reaction to sheath rot of rice using three different scales.

Disease Score
Cultivar IRRI Amin's scale Scale followed at Pantnagar
scale Percent Lesion
basis size 1976 1977

Anupama 9 9 5 7.3 6.8
Bala 7 8 3 4.1 4.9
Bas 370 7 7 3 3.0 2.9
Benilbhog 5 6 3 4.0 3.2
BJ 1 5 6 3 4.9 4.5
BJ 1 (Dwarf) 7 6 3 4.9 4.6
Cauvery 7 8 3 4.2 4.7
Ch 3 5 5 3 3.5 4.1
Ch 45 7 7 3 3.9 4.4
Chinsurah Boro II 7 7 2 2.6 2.8
Hansraj 9 8 3 5.2 5.7
Homthong 3 4 2 2.3 2.1
IET 3359 9 8 4 5.4 6.2
IR 8 7 7 3 4.5 4.3
IR 20 9 9 5 7.5 6.8
IR 22 7 7 3 4.6 4.2
IR 24 7 7 3 6.1 6.5
IR 26 7 7 3 4.8 4.3
IR 28 7 7 3 3.1 3.7
IR 30 7 7 3 4.5 4.8
IR 1514-A-E-597 7 7 3 4.5 4.3
Jaya 9 8 4 5.0 4.6
Jayanti 9 9 5 7.8 8.1
LZN 9 9 5 6.7 6.7
Nagakayat 7 7 3 4.8 4.3
Pusa 2-21 7 8 3 4.0 4.3
Ratna 5 6 3 5.0 4.7
RP 291-7 7 8 4 5.5 5.2
RP 633-1 7 7 4 4.9 4.6








Development of Inoculation Technique


RP 633 (C) 7 7- 2 4.6 4.7
Sabarmati 7 6 3 4.3 4.5
Saket 4 7 8 3 43 4.2
Surya 7 7 3 5.8 5.1
Satya 7 8 4 5.0 4.7
Semora Mangga 7 8 4 5.5 5.4
Sigadis 5 5 2 2.9 2.6
Sona 7 7 4 5.0 4.7
Suhashini 7 7 4 4.3 4.8
Tainan-3-Mutant 5 5 3 3.8 4.3
Tilak Chandan 7 6 2 3.3 3.7
TKM 6 5 5 3 3.0 2.8
T (N)1 7 8 3 4.0 4.3
Type 3 9 7 3 5.5 5.2
UPRI 71-12 5 6 3 3.4 3.8
Vijaya 9 9 5 8.0 7.6
Zenith 9 9 5 7.2 6.6


of the entries gave resistant reaction
except Homthong using the IRRI scale
which is based on percentage of tillers
infected. While the IRRI scale may be
appropriate for diseases in which the
infected plants are killed and/or do not
produce the economic product like
damping-off, smuts, etc. it may not be
suited for scoring sheath rot of rice.
-Disease incidence in traces on most of
the plants of a variety may indicate
resistance but on percentage basis it
will be grouped erroneously as suscep-
tible. In Amin's scale where both per-
cent infected tillers and the lesion size
were considered, scores obtained likewise
did not follow the same trend (Table 3).
In a disease like sheath rot, emphasis
should be given on the severity and lesion
types in determining the resistance/sus-
ceptibility in a variety. By adopting the
third method of scoring, five entries,
namely: Bas 370, Chinsurah Boro II,
Homthong, Sigadis and TKM 6 were
resistant; 28 moderately resistant; 8 mode-
ratelyl susceptible and 5 were susceptible
(Table 3).


Bas 370, Chinsurah Boro II and Hom-
thong are new sources of resistance while
the resistance of TKM 6 and Sigadis has
been reported (Amin, 196; Subramanian
and Ramakrishnan, 1975a). Jayanti, Vi-
jaya and Zenith have been reported as
resistant/moderately resistant (Amin,
1976; Naik and Roy, 1975; and Subra-
manian and Ramakrishnan,, 1975a) but
gave susceptible reaction in the present
screening which may be due to the pre-
sence of different races of the pathogen.
Zenith has been reported as suscrptible
(Chung, 1975; Harahap et al., 1975).
Semi-dwarf varieties were observed to be
more susceptible than the local tall varie-
ties (Amin et al., 1974). The same trend
was also observed in the present study.
Considering the potentiality of the
disease and its wide-spread distribution,
it is advocated that breeding programme
should be initiated for developing re-
sistant varieties and lines like Chinsurah
Boro II, Sigadis and TKM 6 which have
resistance to other pests and diseases
should be used as parents.


Jan. & June 1981












LITERATURE CITED

AHAMED, N. J., S. KANNAIYAN, and A. VENKATA RAO. 1975. First record of
Acrocylindrium sheath rot disease of rice in India. Sci. and Cult. 41: 544-545.

AMN, K. S. 1976. Sources of resistance to Acrocylindrium sheath rot of rice. Plant Dis.
Reptr. 60:72-73.

AMIN, K. S., B. D. SHARMA andC. R. DAS. 1974. Occurrence in India of sheath rot of
rice caused by Acrocylindrium. Plant Dis. Reptr. 58:358-360.

CHAKRAVARTY, D. K., and S. BISWAS. 1978. Estimation of yield loss in rice affected
by sheath rot. Plant Dis. Reptr. 62:226-227.

CHUNG, H. S. 1975. Studies on sheath rot of rice caused by Acrocylindrium oryzae
Sawada. Testing varietal reaction and culture filtrates of the causal fungus. Korean
J. Pl. Prot. 14:23-27.

ESTRADA, B. A., L. M. SANCHEZ and P. CRILL. 1979. Evaluation of screening
methods for sheath rot resistance of rice. Plant Dis. Reptr. 63:908-911.

HARAHAP, Z., A. K. M. SHAHJAHAN and M. C. RUSH. 1975. Research reports on rice.
Rice J. 78 (Oct.): 24.

INTERNATIONAL RICE RESEARCH INSTITUTE. 1975. Standard Evaluation System
for Rice. 56 pp.

NAIK, R. and J. K. ROY. 1975. Occurrence of sheath rot of rice in Sambalpur. Rice
Pathology Newsl. 1975 (Feb.): 8-9.

NAIR, M. C., and P. K. S. RAJAN. 1976. Sheath rot of rice. Agric. Res. J. Kerala 13:
105-106.

OU, S. H. 1972. Rice diseases. Commonw. Mycol. Inst. Kew, Surrey, England. 368 pp.

PAL, A. 1975. Response of some rice varieties towards sheath rot Acrocylindrium oryzae.
Saw infection. Rice Pathology Newsl. 1975 (Feb.): 18-19.

REDDY, T. C. V., K. S. REDDY. A. \. Rao, and D. K. RAO. 1973-74. A note on sheath
rot of rice from India. J. Res. Andhra Pradesh Agric. Univ. 2 & 3: 136-138.

SAWADA, K. 1922. Descriptive catalogue of Formosan Fungi II. Rep. Govt. Res. Inst.,
Dept. Agric., Formosa 2: 1-135.

SUBRAMANIAN, C. L., and G. RAMAKRISHNAN. 1975. Sheath rot of rice. F. A. O.
P1. Prot. Bull. 23:49.











Philipp. PhytopathoL 17: 74-86


ON-FARM RESEARCH ON CHEMICAL CONTROL OF SOME DISEASES
OF DRYLAND CROPS GROWN BEFORE AND AFTER RICE

F. A. ELAZEGUI and T. W. MEW

Senior Research Assistant and Plant Pathologist, Department of Plant Pathology,
The International Rice Research Institute, Los Bafios, Laguna, respectively.

ABSTRACT

The use of fungicides to control some diseases of dryland crops grown before
and after rice was assessed in farmers' fields at the outreach sites of the Cropping Sys-
tems Program to evaluate the economic feasibility of such disease control method for
immediate adoption by the farmers with small lar'holdings.
Seed treatment with Ridomil at the rates c 0.5 to 0.125 g ai/kg seed controlled
downy mildew of corn planted before rice in Pangasinan. The disease incidence was
lower in Macapuno variety and in early planting. The control in sweet corn was re-
flected statistically on yield. The cost of control by Ridomil comprised only < 1% of
the gross income, the highest of which was P5053.38 compared to that of untreated,
P498.22, for sweet corn in April 25 planting. The farmers in Pangasinan may, therefore,
use Ridomil even at low rate (0.125 g ai/kg seed) in treating their seeds especially
sweet corn variety to gain more profit, may continue planting Macapuno
variety which is moderately susceptible to the disease, or may plant early to escape
infection. For powdery mildew of mungbean planted after rice in Pangasinan and
Iloilo, the 0.15- and 0.30-g benomyl/1 H 0-rates were equally effective statistically.
Thiophanate methyl incurred expenses which comprised only approximately 10% of
the gross income in Pangasinan. Although benomyl is an expensive fungicide, the
farmers may still afford it using lower rates, without sacrificing the disease control and
still obtaining higher net returns. With the confirmation of the effectiveness of thio-
phanate methyl on the disease, the farmers may have an alternate in the fungicide to be
used.

The Plant Pathology Component of and are economically important. Con-
Cropping Systems Program is aimed at cerning the effect of paddy on diseases,
analyzing the impact of natural interac- flooding has some apparent effect on the
tions existing between the component elimination of soil-borne pathogens. For
crops, with rice crop as the base, in the disease management and control which is
cropping system and diseases. In carrying aimed at reducing or eliminating the ino-
out this objective, researches have been culum from the field, the approach is
focused on the following aspects: disease through either any of the following: cul-
survey, effect of paddy on diseases of tural practices, the use of resistant varie-
dryland crops before and after rice,, ad ties, chemical control, or their combina-
disease management. Surveys of plant tions. Researches on this particular as-
diseases have been carried out in order to pect are being undertaken as a means
identify the diseases present at the Crop- of carrying out the component technolo-
ping Systems Program outreach sites gy development and evaluation which is
which are actually the farmers' fields in one of the major areas of the program.
Pangasinan and Iloilo and to determine The cultural method of control such as
which of these diseases are most prevalent tillage levels or methods of crop estab-









Fune 1981 On-farm Research


nt and cropping sequence is unlike- have been conducted right at the fi


r such control may still be
:er one or two years. Yet,
ners are interested in the in
trol of the disease. The us
varieties may be applicable.
ever, resistant varieties are
Mble nor acceptable to the f
)il-borne diseases, there may
it varieties while for some


with aitterent virulence
:ity (Mew and Elazegui, 1S
control has been considered
it report since this metho
uld be immediately availab
s.
iployment of chemical coi
the Cropping Systems Prol
imed at intensifying crop r
rice farmers with small I


UIVUIVU
tem for
e station o
a flow c
if ratories
y stations
i- finally t
i- The pr(
it flow of
:- to the f,


or J..L.... VXt. UV5V-V JV. -U U.
). cropping pattern in Manaoag, Pai
in Late plantings of corn, howev
Af from downy mildew caused by tl
:o Peronosclerospora philippinensis I
Shaw. Planting earlier, from A
ol April aids to escape infection b
m hardly practised by farmers du
d- sence of rain during those mon
d- sidering that their fields are


the farmers to adopt such control mea- been Known tor years out still te farmers
sure. The control recommendations, there- in Manaoag, Pangasinan continue planting
fore, have to be very practical in terms of Macapuno variety which appeared to be
the farmers' ability to execute them. moderately susceptible to the disease.
Since the program considers the farmers Therefore, the alternative is to protect
of small landholdings, effectiveness of the the crops from the disease by the use of
fungicides, their cost, availability, and fungicides.
methods of application should be of im- Seed treatment using Ridomil 25 WP
portant considerations. Certain chemicals (25% acylalanine) was found to provide
have been known to be effective against excellent control of downy mildew. Gar-
particular diseases, and one of the activ- cia and Haws (1978) did not observe
ities of the Plant Pathology-Cropping any infection using rate as low as 0.31 g
Systems has been to test such fungicides, ai/kg seed compared to control which
using different rates and timing of applica- had 48.2% infection at 48 days after
tion as the variables, and to carry out planting. Likewise, Exconde and Molina
cost and return analysis for the inputs (1978), using eight rates ranging from
applied to arrive at economically feasible 0.5 to 4.0 g ai/kg seed observed complete
chemical control recommendations for protection of the plants from the disease
disease management in cropping systems, at all rates except at 0.5 which showed
Another consideration is that the trials 2.0 and 3.1% infection at 28 and 42 days


J~~C~III~
*.. Rire












'ter emergence, respectively. The disease MATERIALS AND METHODS
cidence in the control was 99.5%.
The study was designed to determine Downy Mildew of Corn Planted Before


co:. with consideration on yield. Redu-
cing the rate of application without
sacrificing the disease control apparently
entails less input.

Powdery Mildew of Mungbean Planted
After Rice
Powdery mildew caused by the fungus
Erysiphe polygoni D. C. is one of the
foliage diseases of mungbean which is al-
most always present in the legume plant-
ings at the outreach sites. Yield losses due
to the disease recorded at UP College of
Agriculture reached as much as 21% when
all of the leaves are covered with mildew
colonies at flowering time (Quebral and
Lantican, 1969). Quebral (1977) reported
that timely spraying of benomyl (Ben-
late) at the rate of 1/4 lb/100 gal. H20
(=0.30 g/1 H20) fc. at least twice
throughout the growing season at 10- to
14-day interval effectively controlled
powdery mildew. In determining th ef-
fect of interaction of foliar fungicides,
against powderry mildew, and insecticides
on mungbean yield after rice, the Ento-
mology-Cropping Systems (IRRI Annual
Report for 1977) observed that thiopha-
nate methyl applied at recommended rate
was the least costly. The performance of
the fungicide on the disease, however
was not mentioned.
The experiment was conducted to de-
termine the effectiveness of thiophal.dte
methyl (Fungitox) and of lower rates of
benomyl in the control of powdery
mildew. As in corn downy mildew exper-
iment, using lower rates of benomyl
entails less input which is of great advan-
tage to the farmers with only small land-
holdings.


naoag, Pangasinan. Two varieties of corn
were used, namely: Macapuno and Hawaii
Supersweet f6, the local and susceptible
varieties, respectively. The treatments
used were 1.0, 0.5 and 0.25 and 0.125 g
ai of Ridomil/kg seed. The seeds were
treated by slurry method using a glass
jar with tight cover. The treated seeds
wt e air-dried and sown in field 24 hr.
after tivatment. The incidence of the di-
sease, expressed as % infection was de-
termined by taking the ratio of infected
plants to the total population on a plot
basis multiplied by 100. The experiment
was conducted in two trials, each with
four replications. In the first trial, ran-
domized complete block design was used
with 28-sq m-plot size and the data were
taken at 20, 30 and 40 days after emer-
gence; while in the second, split-plot de-
sign was used with 23- to 28-sq. m.-plot
size and observations were done daily for
5 days starting at 5 days after emergence
and subsequently, at two- and three-day
intervals until five readings on each in-
terval were completed. The last data on
trial II were taken at harvest.

Powdery Mildew of Mungbean Planted
After Rice
Two trials were conducted in Manaoag,
Pangasinan. The first trial was carried out
in three barrios during the crop year
1978-79. The treatments consisted of
0.30- and 0 15-g benomyl/1 H20 rates
applied as spray at 35 DAE. Unsprayed
plots served as check. Data which were
taken at 10, 21 and 31 DAS (days after
spraying) were recorded based on infec-
tion on 5 lower leaves/plant using 9 plants
randomly sampled/plot. Each leaf was









un-iann Kesearen


iawu as IOIows: u = no mrecuon, I =
1 to 5% leaf area affected, 3 = 6 to 25%
5 = 26 to 50%, 7 = 51 to 75%, and 9 =
>75% infection. Data on grain yield in
each plot were also taken. In the second
trial, the efficacy of lower rates of beno-
myl against the disease was compared to
thiophanate methyl, a cheaper fungicide.
The trial was conducted in two barrios,
with two spray applications done at 22
and 36 DAE. Data were taken 14 days
after each treatment application.
Only one trial was conducted in Iloilo
with experimental details similar to the
second trial in Pangasinan except that
two varieties of mungbean were used.

RESULTS AND DISCUSSION

Downy Mildew of Corn Planted Before
Rice

Data on the first trial, presented in
Table 1, shows a significant control of
the disease at all rates used for both
varieties. In Macapuno, the control
offered by the fungicide at all rates did
not vary significantly at all observation
dates. In sweet corn, the one-gram rate
was significantly more effective than the
0.25- and 0.125-g-rates at 30 and 40
DAE (days after emergence). The one-
gram rate was not included in the Maca-
puno variety since the fungicide was in-
sufficient when the trial was set. The first
trial was destroyed by typhoon, hence,
there were no data on yield.
For the second trial, the results are
presented in Table 2. For both planting
plates, significant control of the disease
was observed at all rates used. The rates
if fungicidal application were significant-
ly correlated with infection percentage in
sweet corn. Therefore, the discovery of
Ridomil for the control of downy mildew
will be of great value to the farmers, and


its ease of application by seed treatment
will render its usage very feasible.
For both planting dates in Macapuno,
the effect of treatments was not reflected
statistically on yield in contrast to sweet
corn where significant differences were
obtained between the treated and untrea-
ted plots (Table 3). The control in sweet
corn brought about a tremendous yield
increase over the untreated ranging from
276.09 to 313.04% and from 794.43 to
914.29% for April 8 and 25 plantings,
respectively. The gross income in Maca-
puno was higher than in sweet corn as
expected since Macapuno yielded more.
In sweet corn in the April 8 planting, the
gross return in treated plots was approxi-
mately P4000 compared to P1000 in the
untreated; while in the April 25 planting,
it was approximately P5000 compared to
P500 in the untreated. The expenses in-
curred with Ridomil ranged from P11.50
to P34.00/ha which comprised only <1%
of the gross return. Although Ridomil
may be costly, the low rates of applica-
tion renders the cost of the disease
controll cheaper. Hence, the cost of the
Fungicides may no longer pose a problem
For the target farmers. Moreover, the ef-
fects of lower rates of Ridomil on yield
md on returns to the farmer is a convin-
cing proof for them to adopt this techno-
logy.
The data on the second trial also
showed that the April 8 planting showed
anly a maximum of 13.7 and 87.2% in-
Fection as compared to that of April 25
with 47.4 and 96.3% for Macapuno and
sweet corn, respectively. Therefore, plant-
ng early as a positive way of downy
mildew disease management was ascer-
tained. The build-up of inoculum from
diseased plants in early planting caused
the higher disease incidence in later plant-
-- i-, a.- 3 t, m t ...a .1 t


77.









Table 1. Effect of treatments on the incidence of downy mildew on two corn varieties at various observation dates. (Pangasinan,
1978).


%Infection1

Rate (gm ai/kg Macapuno Sweet corn
Chemical seed) 20 DAE2 30 DAE 40 DAE 20 DAE 30 DAE 40 DAE


Ridomif 25 WP
"


0.5
0.25
0.125


Check


0 a
0 a
0.76 a
51.12 b


1.98 a
0.80 a
0.42 a
54.84 b


2.34 a
2.57 a
1.67 a
57.24 b


0 a
0.77 a
3.26 a
8.71 a
71.79 b


0.81 a
4.11 a
18.46 1
28.48 1
87.37


5.78 a
18.23 ab
31.95 b
34.72 b
89.99 c


1 Based on the ratio of infected plants
replications.
2DAE days after emergence.


to the total population on


five middle rows/plot; each


figure represents mean of 4


Analysis based on values transformed to arcsin; means followed by a common letter are not significantly different at 5% level by
DMRT.









n. & June 1981


ty of downy mildew infection in both
moderately resistant and suscrptible corn
varieties. The rains that come during the
iter months, therefore, favor the sub-
equent development of the disease in
ate plantings after natural inoculation,
rith the inoculum originating from early
plantings.
Planting early, however, may hardly
ie adopted by farmers because they are
mited by the absence of rain since their
fields are either strictly rainfed or just
artially irrigated. In such case, another
ecourse is the use of resistant varieties.
'he local variety Macapuno appeared to


'able 2. Effect of treatments on tie incident
dates (Pangasinan, 1979).



Rate of
variety Ridomil 25 WP April
(g ai/kg seed) 34 DAE2

lacapuno 0.50 0 a

0.25 0.23 a

0.125 0.33 a

0 13.41 b

Iweet corn 0.50 0.50 a

0.25 1.32 a

0.125 4.91 b

0 71.04 c


Based on the ratio of infected plants to
analysis based on values transformed to arc:


ave a certain degree of resistance to
owny mildew as compared to sweet corn.
Iso in contrast to sweet corn, the disease
control in Macapuno effected by Ridomil
'as not reflected statistically on yield for
oth planting dates. The highest disease
icidence in Macapuno was only 47.4%
ad it did not reduce significantly the
umber of marketable ears. This partic-
lar study, therefore, revealed various
Iternatives for the farmer in the manage-
ient of downy mildew. Each of the alter-
atives presented could be executed by
ie farmers depending upon the situation
i which they are confronted with.


*f downy mildew of corn at two planting



Incidencel
1979 April 25, 1979
At harvest 34 DAE At harvest

0 a 0 a 0 a

0.46 ab 1.66 a 2.03 a

1.33 b 1.66 a 3.56 b

13.65 c 40.62 b 47.43 c

0.50 a 0 a 2.68 a

3.14 b 2.87 b 7.09 b

9.01 c 11.04 c 21.90 c

87.25 d 71.49 d 96.27 d


e total population on middle rows/plot;



significantly different at 5% probability


n-fann Research














Ratel of No. of max
Variety Ridomil 25 WP ears2/ha.
(g ai/kg seed) thousand

April 8,
Macapuno 0.50 27.46 a
0.25 27.46 a
0.125 25.96 a
0 25.53 a

Sweet corn 0.50 18.48 a
0.25 20.30 a
0.125 19.76 a
0 4.91

April 25,
Macapuno 0.50 28.91 a
0.25 27.67 a
0.125 28.91 a
0 23.58 a

Sweet corn 0.50 22.18 a
0.25 25.27 a
0.125 22.60 a
0 2.45

1At the rate of 15 kg seeds/ha, 30 gm Rid<
seed-rate, 15 for 0.25-gm rate, and 7.5 fo
2 hours.
2Analysis based on values transformed to I
3Green corn at PO.20/ear.
4Ridomil: P1000/kg; cost of labor in treal


Powdery Mildew of Mungbean Planied
After Rice
The first trial revealed that in the three
barrios, at 56 and 66 DAE, the disease
was significantly controlled by the two
rates of benomyl tested (Table 4). The
infection was nil in barrios Lipit and
Caaringayan Lakay at 45 DAE, hence, the


t % increase Gross Variable cost4
over check return3 P/h % of gross
(P/ha) return

79 Planting
7.53 5491.45 34.00 0.62
7.53 5491.45 19.00 0.35
1.67 5192.31 11.50 0.22
0 5106.84 0 0

276.09 3696.58 34.00 2.92
313.04 4059.83 19.00 0.47
302.17 3952.99 11.50 0.29
0 982.91 0 0

179 Planting
22.64 5782.92 34.00 0.59
17.36 5533.81 19.00 0.34
22.64 5782.92 11.50 0.20
0 4715.30 0 0

790.43 4436.30 34.00 0.77
914.29 5053.38 19.00 0.38
807.14 4519.57 11.50 0.25
0 498.22 0 0

il 25 WP will be used up/ha for 0.5 gm ai/kg
.125-rate; time spent in treating 15 kg seeds


10(X+ 1).

Sthe seeds: P2.00/hr.




effect of treatment was not observed.
Generally, there was a correlation, al-
though insignificant, between the degree
of control and rate of chemical used.
clloh rAilft .I mIaeWP.+a t*ht +u. n 1 I1


__ _









Da-fam Research


fable 4. Effect of benomyl on the severity
bean planted after rice'. (Pangasi


barrio Treatment2

'ao Benomyl at 0.30 g/1 H20
Benomyl at 0.15 g/l H20
Check

Lipit Benomyl at 0.30 g/1 H20
Benomyl at 0.15 g/1 H20
Check

'aaringayan Benomyl at 0.30 g/1 H120
akay Benomyl at 0.15 g/1 H120
Check

1Means followed by the same letter are not
(LSD).
1Applied at 35 DAE (days after emergence)
3Based on 5 lower leaves/plant with 9 plain
) no infection, 1 1 to 50% leaf area a
:o 75%,9 > 75% infection.

-ate against the disease. The effect of
treatments, however, was not reflected
statistically on yield due perhaps to late
occurrence of infection. Although the
powdery mildew rating reached as high
as 6.62, in untreated plot in Pao at 21
DAS, there was no significant reduction
in yield since the crop was already at seed
stage. Therefore, it appeared that if infec-
tion appears as late as the early seed stage,
no matter how severe it is, control may
no longer be necessary as far as yield is
concerned. No cost and return analysis
was carried out in the first trial since the
yield obtained among the treatments did
not differ significantly.
In the second trial, for the two barrios
and the two observation dates, the con-
trol offered by thiopanate methyl did not
vary significantly with those by benomyl


powdery mildew and on yield of mung-
1978-79).

Disease ratin3/leaf Yield
5 DAE 56 DAE 66 DAE4 (t/ha.)

1.16 b 0.23 b 0.66 b 0.55 a
1.21 b 0.41 b 1.79 b 0.66 a
.94 a 6.62 a 6.10 a 0.47 a

).05a 0.02 b 0.08 b 1.48 a
).05 a 0.02 b 0.19 b 1.31 a
1.02 a 1.63 a 2.73 a 1.26 a

).10a 0.05 b 0.59 b 2.57 a
) a 0.11 b 1.13 b 2.37 a
1.01 a 1.54 a 4.38 a 2.42 a

lificantly different at 5% probability level



sampled/plot; each leaf rated as follows:
-ted, 3 6 to 25%, 5 26 to 50%, 7 51


it both rates used (Table 5). Moreover,
he control offered by the two fungicides
was reflected statistically on yield. Al-
though there were no significant differen-
es on yield obtained among the treated
plots, the % yield increase over the un-
treated was apparent. The yield was in-
creased by 70% over untreated plots for
thiophanate methyl and by 75 and 66%
For benomyl at the two rates of applica-
tion, respectively in Pao. In Lipit, the
application of thiophanate methyl caused
a greater yield increase of 57% than either
of the two rates of benomyl. The disease
symptoms appeared as early as 22 DAE,
(late vegetative to bud stage), hence, the
yield was adversely affected. Considering
the cost and return analysis, the untreated
gave a gross income of only P6800
and P4650 compared to 0.30-g rate beno-


an.,. June 1981








n me seventy or powaer3


L
Fungicide 37
Barrio (g/1 H20)


Pao Thiophanate methyl
0.31 2.2
Benomyl
0.30 2.1
0.15 2.2
Check 6.8

Lipit Thiophanate methyl
0.31 3.2
Benomyl
0.30 2.9
0.15 3.2
Check 7.8

2 Applied as foliar spray at 22 and 36 DAI
benomyl at 0.30-rate; with 125 hr. of sp.
respectively; with 97 hr./ha. of spraying.
Based on 6 leaves/plant with 9 plants sar
6 to 25%, 5 26 to 50%, 7 51 to 75%,
4 Mungbean at P 5.00/kg.
5Includes cost of fungicides (Fungitox, thi
the fungicides (P 1.75/hr. of spraying).


:ase ratingf/leaf
AE 51 DAE t/ha. % increase
over check



i 2.02 a 2.32 a 70.5S

1 1.74 a 2.38 a 75.0(
1 1.76 a 2.26 a 66.1E
b 7.75 b 1.36 b 0


1 2.24 a 1.46 a 56.95

1 2.39 a 1.35 a 45.1(
1 2.23 a 1.21 ab 30.11
b 7.78 b 0.93 b 0

days after emergence). For Pao, 0.83 kg thio
ring/ha. For Lipit, 0.67 and 0.65 kg/ha for tl

led/plot; each leaf rated as follows: 0 no ii
- > 75% infection.

ohanate methyl, at P 25/120 gm; Benlate, ber


mungmi









r*.n TIn 1001


myl and thiophanate methyl which
gave a gross return of P11900 and
P7300 in Pao and Lipit, respectively.
The highest gross returns from the two
treatments were expected since they
had the highest yield. Spraying
thiophanate methyl as a control mea-
sure for powdery mildew incurred expen-
ses amounting to P781.94 and P620.14/

Table 6. Effect of treatments on the several
after rice (loilo, 1979-80).


Fungicide2
Barrio (g/1 H20) 49-50]

Rizal Thiophanate methyl
0.31 3.52 2
Benomyl
0.30 3.26
0.15 3.58 1
Check 5.44

Napnapan Thiophanate methyl
0.31 4.44
Benomyl
0.30 5.29 a
0.15 6.12
Check 8.23

Cordova Thiophanate methyl
0.31 6.03 a
Benomyl
0.30 6.47 a
0.15 6.14
Check 8.00

IMeans in a column/barrio followed by the
5% level (DMRT).
Applied as foliar spray: first spraying at 3(
Napnapan, Cordova, and Rizal, respective]
and Rizal and at 51 DAE for Cordova.
3Based on 3-5 leaves/plant with 9 plants sal
infection, 1 = 1 to 5% leaf area affected,:
9 = > 75%. infection.


ha. which comprised only 6.74 and 8.50%
of the gross income for Pao and Lipit,
respectively. Such variable costs ap-
proached those of benomyl applied at
0.15-g rate.
In Iloilo, the efficacy of thiophanate
methyl and of the two rates of benomyl
in controlling powdery mildew was con-
firmed (Table 6). The resistance of CES

f powdery mildew of mungbean planted


Disease severity 3
r 50-10A CES X-10
E 61-63 DAE 49-50 DAE 61-63 DAE


2.00 a 2.29 a 1.44 a

1.89 a 2.35 a 1.33 a
2.22 a 3.36 a 1.56 a
3.00 b 3.49 b 2.67 b


3.31 a 2.01 ab 0.85 a

3.47 a 1.57 b 1.07 a
3.11a 3.13 a 0.97 a
4.39 b 5.04 c 2.29 b


4.04 a 7.02 ab 2.46 a

3.10 ab 5.97 a 2.73 ab
2.74 b 5.97 a 2.78 ab
5.75 c 7.57 b 3.86 b

ne letter are not significantly different at

3, and 34 DAE (days after emergence) for
second spraying at 50 DAE for Napnapan

ed/plot; each leaf rated as follows: 0 = no
6 to 25%, 5 = 26 to 50%, 7 = 51 to 75%,


na.firm Repfrwh









Phblippin Phytopathlogy


Vol. 17


X-10 to the foliage disease as compared
to MG 50-10A was also confirmed as
shown by the lower disease rating in the
former. Concerning yield, however, the
general performance of the crop was not
as impressive as that in Pangasinan since
the plants in Iloilo suffered from drought
(Tables 7a and b). Despite the very low
yields obtained, the % yield increase
among the treated plots generally, was
still evident. Low yields also caused the
% of gross income attributed to the cost


Table 7a. Effect of treatments on yield of
rice. (Iloilo, 1979-80).


Fungicide t/ha.
Barrio (g/l H20)


Rizal Thiophanate methyl
0.31 0.35
Benomyl
0.30 0.28
0.15 0.26
Check 0.14

Napnapan Thiophanate methyl
0.31 0.55
Benomyl
0.30 0.44
0.15 0.44
Check 0.31

Cordova Thiophanate methyl
0.31 0.57
Benomyl
0.30 0.54
0.15 0.51
Check 0.45

1Mungbean at P5.00/kg.
2Includes cost of fungicides (Fungitox, thick
nomyl, at P48/100 gm) and cost in applyin


of disease control by the fungicides to
become higher. As in Pangasinan, the ex-
penses incurred in the control of the di-
sease by the use of thiophanate methyl
and 0.15-g rate benomyl were lower than
using the 0.30-g rate. There were more
inputs applied in barrio Cordova since the
plants had slightly better stand than those
in the other two barrios.
This particular study revealed that be-
nomyl at 0.15 g/l H20 and thiophanate
methyl at 0.31-g rate may be used by the


lungbean variety MG 50-10A planted after


Yield
. increase Gross Variable cost2
rer check return' P/ha. % of gross
(P/ha) return


150.00 1750 501.98 28.68

100.00 1400 752.10 53.72
85.71 1300 525.24 40.41
0 700 0 0


77.42 2750 667.28 24.26

41.94 2200 1015.72 46.17
41.94 2200 699.82 31.81
0 1550 0 0


26.67 2850 695.82 24.40

20.00 2700 1059.16 39.23
13.33 2550 729.76 28.62
0 2250 0 0


lanate methyl, at P25/120 gm; Benlate, be-
:he fungicides (P 1.75/hr. of spraying).









On-faum Reseach


farmers to control powdery mildew of
mungbean planted after rice. This recom-
mendation was justified by the cost and


return analysis which indicated the profit-
ability in the use of such fungicides at
such rates.


Table 7b. Effect of treatments on yield of mungbean variety CES X-10 planted after rice.
lloio, 1979-80.


t/ha. % increase
over check


Yield

Gross
return
(P/ha)


Variable cost2
P/ha. % of gross
return


Rizal Thiophanate methyl
0.31
Benomyl
0.30
0.15
Check

Napnapan Thiophanate methyl
0.31
Benomyl
0.30
0.15
Check

Cordova Thiophanate methyl
0.31
Benomyl
0.30
0.15
Check


0.39 11.43 1950 501.98 25.74

0.47 34.29 2350 752.10 32.00
0.45 28.57 2250 525.24 23.35
0.35 0 1750 0 0


0.63 21.15 3150 667.28 21.18

0.77 48.08 3850 1015.72 26.38
0.70 34.62 3500 699.82 19.99
0.52 0 2600 0 0


0.65 0 3250


0.71 9.23
0.74 13.85
0.65 0


3550
3700
3250


695.82 21.41


1059.16
729.76
0


29.84
19.72
0


Barrio


Fungicide
(g/1 H20)


1Mungbean at P5.00/kg.
2Includes cost of fungicides (Fungitox, thiophanate methyl, at P25/120 gm; Benlate, be-
nomyl, at P48/100 gm) and cost in applying the fungicides (P1.75/hr. of spraying).


Jan. & June 1981








Phlippine Phytopathology


LITERATURE CITED

EXCONDE, O. R., J. Q. ADVERSARIO, and B. A. ADVINCULA. 1968. Incidence of
corn downy mildew in relation to planting date and meteorological factors. Philipp.
Agr. 52: 189-199.

EXCONDE, O. R. and A. B. MOLINA, JR. 1978. Dosage rates of Ridomil 25 WP (Ciba
Geigy) as seed treatment fungicide against Philippine corn downy mildew. Paper
presented at the 9th Annual Convention of the Pest Control Council of the Philip-
pines, Manila, 3-6 May 1978.

GARCIA, O. A. and L. D. HAWS. 1978. Promising fungicide for the control of downy
mildew of corn. Paper presented at the IRRI Cropping Systems Program Seminar,
2 February 1978. 2 p.

LITSINGER, J. A. 1976. Pest management research methodology on farmers' fields in
a Cropping Systems Program. Paper presented at the Symposium on Cropping
Systems Research and Development for the Asian Rice Farmer. IRRI, Los Baflos,
Philippines 21-24 Sept. 1976. 12 p.

MEW, T. W. and F. A. ELAZEGUI. 1980. The disease problems and management of dry-
land crops grown before and after rice. Paper presented at the Cropping Systems
Conference, IRRI, 5-7 March 1980. 31 p.

QUEBRAL, F. C. 1977. Powdery mildew and Cercospora leaf spot of mungbean in the
Philippines. Paper presented at the 1st International Symposium on Mungbean, Los
Bafios, Philippines, 16-19 August 1977. 5 p.

QUEBRAL, F. C. and R. M. LANTICAN. 1969. Effect of Benlate on powdery mildew
and yield of mungo. Agr. Los Bafios 9: 13-14.


Vol. 17












EVALUATION U'y SEVEN iUNGI(
COCONUT LEAF SPOTS IN 1

REYNALDO

Chief and Science Research Supervisor, I
nter, PCA-Agricultural Research Branch, Bal

ACKNOWLE

ABSTIL

Seven fungicides applied at their high
two batches for efficacy against leaf spot <
In one batch, leaf spots were signifi
captafol-sprayed seedlings than the unspraye
lonil effectively controlled the disease. Capt
control of spots at higher rates.
Benomyl- and phenazin-sprayed palms
unsprayed palms.
Copper oxychloride, captain, maneb, cl
recommended in nursery-raising.

Leaf spots are the most common
eases of coconut, both in the nursery
I on adult palms. These diseases are
lespread, being found wherever coco-
ts are grown. They reduce the photo-
Lthetic activity of palms and, in very
ere cases, make seedlings unfit for
d-planting.
Many types of leaf spots affect the
;onut palm, but spots caused by the
igus Pestalozzia palmarum Cke. & I
-v. are the most predominant, followed
those caused by Helminthosporium 1
(Crop Protection Division, 1977).
ed on the description by del Rosario
'68), leaf spots caused by P. palmarum i
)ear first as small, yellowish brown,
,ular spots and later turn brown with
en-gray centers (hence the name gray
F spot) surrounded by a dark brown
id. In the advanced stage of infection,
tips and margins of the whole leaf
up giving the foliage a blighted 4
Pearance. On the upper surface of the (


DES IN THE CONTROL UY
[E NURSERY STAGE

SABAD

op Protection Division, Davao Research
-Oshiro, Davao City.

CEMENT

T

recommended rates were evaluated in
ease of coconut in the nursery stage.
itly lower in copper oxychloride-and
checks. In the other batch, chlorotha-
and maneb also provided satisfactory

id comparable foliage infection as the

rothalonil and captafol are, therefore,


if, dark, ovoid fruiting bodies of the
agus may be visible. Helminthosporium
if spots are, on the other hand, charac-
ized by small sunken necrotic spots
young leaves. These lesions gradually
large and in advanced cases may result
the drying up of the leaf. The presence
two or more kinds of leaf spots in the
iage, however, is not uncommon.
This co-existence of pathogens in the
ves oftentimes makes spots hardly
tinguisable from one another on the
sis of symptoms, especially at the
:ipient stages of infection. Leafspot
patrol, however, -should be all en-
rnpassing regardless of symtomato-
gical expression.
In previous studies at the Davao Re-
irch Center of the Philippine Coconut
ithority (PCA) it was shown that
e-bearing and bearing palms applied
th potassium chloride (KC1) develop
nsiderable resistance against leafspots
bad, et al., 1975; Abad and Magat,









ppme rnytopamoolo


1977). In the nursery, similar ooserva-
tions were noted by researchers of the
Agronomy-Soils Division. In addition,
common salt (NaCI) gave similar effects
(Magat,etal, 1977).
'lere are situations, however, where
leafspot control cannot be left alone to
KCI or NaCI fertilization. These are
when sources of inoculum are very
abundant, favorable environment con-
dition-, such as when foliage of seedlings
are starting to crowd, and other pre-
disposing factors are present.
This study was conducted at the
Davao Research Center to: a) evaluate
the performance of different fungicides
against coconut leaf spots, and b) to have
a good working knowledge on a further
exploration of techniques by which these
fungicides can be effectively applied.

MATERIALS AND METHODS

The study was set up in a Randomized
Complete Block Design at 12 seedlings
per plot replicated four times and
provided with guard seedlings.
Seedlings of two coconut populations
namely, 'Laguna' (variety Typica') and
'Tacunan' (variety 'Javanica') were used
in the study. The seedlings of 'Laguna'
were grown in ordinary nursery distanced
at 60 cm apart in a quincunx system.
Blanket application of 45 g ammonium
sulfate [(NH4) SO4] plus 60 g potas-
sium chloride KC1) was given to each
palms in split. On the 2nd month from
sowing 20 g of (NH4)2S04 plus 23 of
KCI were applied, the remainders were in
like manner, given on the 5th month. On
the 4th month from sowing, experimental
seedlings were already tagged and uni-
form minimal infection was assured per
palm before fungicidal treatments were
carried out.


Kates ana lime o0 Appncaion
The highest dosage recommended for
each fungicide under evaluation, namely:
benomyl .014%; captain .06%;
captafol 0.3%; copper oxychloride -
0.1%; chlorothalonil 0.36%; maneb -
0.08%; and phenazin 0.012% were
used.
The fungicides were applied every
15 days for a period of 5 months. The
experiment was split into two parts, in
view of the shortage of experimental
materials having homogeneous infection
a the time of first fungicidal application.
Thus, the first part involved captain,
chlorothalonil, maneb and phenazin,
while the second part involved the rest of
the chemicals. Unsprayed seedlings served
as checks in both parts. Randomly distri-
buted infected seedlings served as the
natural sources of inoculum.
All the other necessary nursery
management practices, such as weeding
and insect pest control were carried out
uniformly.
The test on the 'polybagged'-raised
'Tacunan' population only involved
captain and maneb at the higher rates of
0.19 and 0.29% respectively, to further
explore the potential of these relatively
cheaper fungicides.

Gathering of Data
Visual observations were done month-
ly. The following leaf infection rating was
adopted: 0 no infection; 1 minimal
infection; 2 moderate infection and
3 heavy infection. The ratings were
made on the three youngest leaves that
opened during the month.

RESULTS AND DISCUSSION

No significant effects of the chemical
treatments were manifested during the


88












because leafspots were already present on
the three youngest leaves that were con-
sidered for the infection rating and the
youngest one or two of which were also
included in the rating in the following
month.
Among the first batch of chemicals
used, however, the highly significant
effect of chlorothalonil was shown at the
3rd month (Table 1). Captan gave signi-


Table 1. Leaf spot ratings of seedlings spray

MONTE

TREATMENT 1 2
I
Control 2.14 2.52

Captan 2.11ns 2.21ns

Chlorothalonfl 1.96ns 2.12ns

Maneb 1.97"n 2.37ns

Phenazin 1.98ns 2.41ns

average of four replicates with 12 se
transformed values (log x + 1) usin
(DMRT)

based on the rating: 0 no infect
moderate infection; and 3 heavy i
were all minimal in all plots.

ns not significant
significant at 5% level
** significant at 1% level

ficant effect, while maneb and phenazin
did not. Starting from the 3rd month,
chlorothalonil was consistently effective
while effect of captain was erratic. Maneb
showed significant effects only at the 6th
month, while phenazin did not provide


*ifljutl wV ltul ulfufiftutl uvlr ul0u&ulJ*i
of the study. It is not surprising to note
that chlorothalonil exhibited these effects
because its highest recommended dosage
of 3.6 tbsp of the commercial product
per gallon was the highest compared to
the other chemicals.
In the 2nd part of the experiment, the
positive effects of copper oxychloride
and captafol were significantly evident
at the 3rd month after the first spraying


with five chemicals (1st part)a

Y INFECTION RATING b

3 4 5 6

.96 2.97 2.95 2.81

35* 2.22ns 2.12ns 1.73*

.23** 1.83** 1.66** 1.38**

45ns 2.33ns 2.21ns 1.92*
.64ns 2.54ns 2.48ns 2.31ns


lings per plot, analysis based on
Duncan's Multiple Range Test


i; 1 minimal infection; 2 -
wction. Pre-treatment infections






and adequate protection was provided
thereafter until the 5th month (Table 2).
Benomyl was found ineffective.
Based on the results, it is evident that
chlorothalonil, copper oxychloride and
captafol can be effectively used against


ill~UY~ Ill ~CUYI L~U


oW








Philippine Phytopathology


Table 2. Leaf spot rating of seedlings sprayed with four chemicals (2nd part)a

MONTHLY INFECTION RATING b

TREATMENT Pre-
treatment 1 2 3 4 5


2.41ns 2.37m
2.35ns 2.16ns


1.96ns 2.08ns 2.00ns 1.75* 1.62* 1.33**


Copper oxychloride 1.92ns


2.00" 2.00ns 1.66* 1.58* 1.25**


average of four replicates with 12 seedlings per plot; Analysis based on
transformed values (log x + 1) using Duncan's Multiple Range Test
(DMRT)

based on the rating: 0 no infection; 1 minimal infection; 2 -
moderate infection and 3 heavy infection.

ns not significant
* significant at 5% level
** significant at 1% level


leaf spots of coconut when applied before
infection becomes noticeable or when the
seedlings are about 5 months old.
Benomyl and phenazin, both systemic
fungicides, failed to show any promise
even at their highest recommended
dosages. This suggests that systemic
action on coconut can be a very slow
process or that the chemicals were in-
herently ineffective against the leaf
spots.
Somehow, the significant effects of
captain and maneb in some months led tj
the opinion that increased dosages of
the two fungicides can perhaps make
these chemicals more effective. Consider-
ing too, that the cost of these two che-
micals are among the lowest of the fun-
gicides tested, the necessity of an
exploratory trial on this regard was felt;


this time on the population 'Tacunan',
which was previously observed to be
highly susceptible to leaf spots.
The results obtained in "Tacunan' are
encouraging (Table 3). The seedlings
treated with the increased rates of captain
and maneb were very significantly less
infected than the untreated palms. No
significant difference was noted between
the two fungicies. The success of the
treatments, aside from increased dosages,
may have been brought about by the
early application which provided good
protection against the diseases. In all
these tests, no phytotoxicity was noted.


Economic Implications
Copper oxychloride, captain and
maneb are still more economical to use


Control
Benomyl

Captafol


VoL 17


1.92ns
1.96ns


2.14ns
2.22ns


2.39"n
2.35ns









Cholm l Control of Coconut Lea Spots


Table 3. Leaf spot rating of Tacunan' seedlings treated with inceaed rates of the
chemical captain and maneb a


MONTHLY INFECTION RATING b

TREATMENT Pre-
treatment 1 2 3 4

Control 0.30 0.36 0.97 1.92 2.92

Captan 0.30ns 0.47ns 0.55ns 0.7** 1.02**

Maneb 0.28ns 0.44ns 0.61ns 0.75** 1.02**


average of three replicates at 12 seedlings per plot. Analysis based on
transformed values (log x + 1) using Duncan's Multiple Range Test
(DMRT)

based on on the rating: 0 no infection; 1 minimal infection; 2-
moderate infection; and 3 heavy infection.

ns not significant
* significant at 5%
** significant at 1% level


than chlorothalonil or captafol, and still
give satisfactory results (Table 4). As
earlier stressed, chemical control should
start when infection becomes noticeable.
This should be regularly carried out at
15-day cycles until infection subsides or
even up to the field-planting since it is
very difficult to control leafspots when


infections are already quite established
or in outbreak proportions.
It is also advised that few seedlings
which exhibit advanced symptoms at a
nursery age but are not yet expected to
succumb to infection, should be isolated
as they can serve as sources of inoculum.


Jm. & June 1981








ine Phytopathology


fable 4. Economics on the use of the varioi

RECOMMENDED
DOSSAGE OF THE
FUNGICIDE PRODUCT
(tbsp/gal.)

,aptafol (Difolatan) 3
Aaptan (Captex W50;
Captan 50) 3
Copper oxychloride
(Vitigran Blue) 3
Chlorothalonil
(Daconil 2787) 3.6
Maneb (Maneb 80) 3


LITERATI

ABAD, R. G., R. L. PRUDENT and S.
coconut fertilized with various comb
sium chloride. Phil. J. Coco. Studies 3(

ABAD. R. G., and S. S. MAGAT. 1977. El
diseases and yield. Phil. Phytopatholol

ABAD, R. G., N. C. SAN JUAN and R. C. I
Palm. Paper presented at the Symp
1977). Dept. of Plant Pathol. UPLB. 1

DROP PROTECTION DIVISION. 1977. Gu
Res. Branch, PCA. 1st ed. p. 66-69.

MAGAT, S.S., RZ. MARGATE and R.L. P1
(sodium chloride) as a fertilizer and
lings. Phil. Jour. of Coco. Studio 2(3

ROSARIO, M.S.E. del. 1968. Coconut Disea


/ The author is indebted to Mr. Leoi
metrician, PCA-ARB for the design and st
wise, to our co-employees at PCA's Davao R


effectivee fungicides.

COST PER TBSP COST OF RECOM-
F THE PRODUCT MENDED DOSAGE
(peso) (peso)


0.61 1.83


0.21 0.63


0.19 0.57

0.43 1.55
0.29 0.87


E CITED

MAGAT. 1978. Incidence of leaf spot in
Itions of nitrogen, phosphorus and potas-
:37-44.

:t of KC1 fertilization on coconut leafspot
12 (1 & 2): 74-77.

ANCAVER. 1977. Diseases of the Coconut
um on Philippine Phytopathology (1971-
.5 Dec. 1977.

:book on Coconut Pests and Diseases. Agr.


DENTE. 1977. Utilization of common salt
patrol of leaf spot disease of coconut seed-
19-45.

i. Tech. Bull. 20. UPCA.


9)





FOR THE CITRUS-SCAB FUNGUS

A. N. PORDESIMO

Center (NCPC) and Associate Professor of
at Los Bafios, College, Laguna, respective-


flamed scalpel, to another set of plates.
Glycerin agar cooled at 45 C containing
2 drops of 25% lactic acid was poured
over the tissues while gently shaking
the plates in order to have a uniform
distribution of excised lesions. After 48
hr of incubation under room conditions,
cultures were examined under the ordina-
ry light microscope. Those showing
growth characteristic of Sphaceloma
were immediately transferred to glycerin
agar slants as stock cultures.
All cultures were properly identified
and grouped by place of collection. These
served as sources of inocula for subse-
quent experiments.
The fungus was successfully isolated
using excised young lesions on calamon-
din fruits when grown on glycerin agar by
poured plate technique. Two days after
isolation, reddish to pinkish or yellowish
to orange growth developed along the
margins of scabby tissues (Fig. 1). There
was first a tortuous growth of minute
colorless hyphae which soon combined
into a kind of stroma. In 34 days, the
mycelia became visible to the unaided
eye. In 12 days, the mycelia were 2-4
mm in diameter, hemispherical and flesh
colored, with a yellowish to reddish-
brown tinge. The central mass became
raised, conical, firm and gummy. The
central part was made up of close-septate
hyphae in a fairly gelatinous mass, from
the edges of which extended chains of
oval cells; many of them were apparently
formed by budding. The fungus did not
usually spread out much over the surface


Note: AN ISOLATION TECHNIQUE

J. M. DANGAN AN

Researcher I, National Crop Protecti
Plant Pathology, College of Agriculture, U
ly.

Isolation, as the second rule of proof
of pathogenicity, is an essential procedure
prior to the study of morphology, physio-
logy, and cultural characteristic of a sus-
pected pathogenic microorganism. Often-
times, however, techniques used in isolat-
ing such a microorganism appear effective
only after a series of consummated fail-
ures on the part of the researcher. Work-
ing with fungi, for instance, requires my-
riads of isolation techniques depending
on their growth kinetics on either natural
or artificial medium. For slow-growing
fungi like the citrus-scab fungus, failure
to isolate it in vitro may be principally
due to ineffective technique and a speci-
fic substrate.
In the Philippines, reproducible me-
thods of isolating and culturing the citrus-
scab fungus are still wanting, hence this
study.
Calamondin (Citrus madurensis Lour.)
fruits from various localities bearing scab
lesions were collected and incubated for
24 hr or more inside a refrigerator.
Diseased fruits were rinsed in sterile
distilled water and scab lesions of ca.
1 mm diameter were individually excised
with a sharp scalpel under the dissecting
microscope. Excised infected tissues were
then placed in petri plates containing
enough amount of sterile distilled water
just to saturate the lesions to prevent
It ~. 4r- T : r ..- . . :









Phiippine Phytopatholog


rIe!


Fig 1. Two-day-okl growth of Sphaceloma fawcetti Jenkins among margins of a scab
lesion on glycerin agar (70x).


of the medium, but became raised in time
fprming tough masses. The purplish
color reaction of the citrus-scab fungus
and its felty nature on glycerin agar are
the distinctive features of Sphaceloma
fawcetti Jenkins on this medium.
The citrus-scab fungus was isolated
with a certain degree of difficulty. This,
however, confirmed similar results ob-
tained in the isolation of Sphaceloma
fawcetti Jenkins by early workers (Faw-
cett, 1907;Winston, 1923; Jenkins, 1925;
Whiteside, 1975). This difficulty in the
isolation of S. fawcetti appeared to be
partly due to tissue plantings from old
scab lesions, time interval of disinfection,
kind of agar medium used, and above all,
the typically slow growth of the fungus


in artificial culture. When scrapings
were made from relatively young lesions
very few contaminants developed using
the poured plate technique. This finding
is in agreement with the work of Winston
(1923). Isolations from old scabby lesions
which have been outgrown by saprophy-
tic fungi were invariably more difficult.
In general, the citrus-scab fungus
grows slowly, requiring from 5 to 8 days
at ordinary room conditions for its colo-
nies to become unmistakably visible.
On glycerin agar, the fungus produced a
distinct purplish color reaction which
often became plainly visible even before
growth characters were advanced enough
to be distinctive.


LITERATURE CITED

FAWCETT, H. S. 1907. Citrus scab. Florida Agr. Expt. Sta. Annu. Rept. 1906-1907:
45-56.

JENKINS, ANNA E. 1925. The citrus-scab fungus. Phytopathology 15: 99-104.

WHITESIDE, J. O. 1975. Biological characteristics of Elsinoe fawcetti pertaining to the
epidemiology of sour orange scab. Phytopathology 65: 1170-1175.

WINSTON, J. R. 1923. Citrus scab: its cause and control. USDA Bull. 1118, 38 p.


Vol. 17














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