Front Cover
 Front Matter
 Abstracts of papers presented at...
 Thiabendazole as seed treatment...
 Mineral oil sprays on wheat seedlings...
 Control of diplodia rot of mango...
 An improved mass screening method...
 A cage method for studying experimental...
 The capacity of nephotettix virescens...
 Effects of Rotylenchulus reniformis...
 Plant parasitic nematodes associated...
 Bacterial leaf spot, a new disease...
 Phytopathological notes: Notes...
 Indexes to volumes 1-8, 1968-1...
 Back Cover

Group Title: Journal of Tropical Plant Pathology
Title: Journal of tropical plant pathology
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00090520/00017
 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 1974
Frequency: semiannual
Subject: Plant diseases -- Periodicals -- Philippines   ( lcsh )
Plants, Protection of -- Periodicals -- Philippines   ( lcsh )
Genre: periodical   ( marcgt )
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: VID00017
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
    Front Matter
        Front Matter 1
        Front Matter 2
    Abstracts of papers presented at the eleventh annual meeting of the Philippines phytopathological society, Davao City, 8-10 May 1974
        Page 1
        Page 2
        Page 3
        Page 4
    Thiabendazole as seed treatment to control infection by aspergillus flavus link exfries and aflatoxin contamination in corn
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
    Mineral oil sprays on wheat seedlings affect the incidence of stem rust, leaft rust and septoria nodorum lesions
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
    Control of diplodia rot of mango by hot water treatment
        Page 16
        Page 17
        Page 18
    An improved mass screening method for testing the resistance of rice varieties to tungro disease in the greenhouse
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
    A cage method for studying experimental epidemiology of rice tungro disease
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
        Page 40
        Page 41
    The capacity of nephotettix virescens to infect rice seedlings with tungro
        Page 42
        Page 43
        Page 44
        Page 45
        Page 46
        Page 47
        Page 48
        Page 49
    Effects of Rotylenchulus reniformis inoculations on mung bean, soybean and peanut
        Page 50
        Page 51
        Page 52
        Page 53
        Page 54
        Page 55
    Plant parasitic nematodes associated with sweet potato and cassava in the Philippines
        Page 56
        Page 57
        Page 58
        Page 59
        Page 60
        Page 61
        Page 62
        Page 63
        Page 64
        Page 65
        Page 66
        Page 67
        Page 68
        Page 69
        Page 70
    Bacterial leaf spot, a new disease of Poinsettia
        Page 71
        Page 72
        Page 73
        Page 74
        Page 75
        Page 76
        Page 77
        Page 78
    Phytopathological notes: Notes on anthracnose diseases of ornamentals
        Page 79
        Page 80
        Page 81
        Page 82
        Page 83
        Page 84
    Indexes to volumes 1-8, 1968-1972
        Page 85
        Page 86
        Page 87
        Page 88
        Page 89
        Page 90
        Page 91
        Page 92
        Page 93
        Page 94
        Page 95
        Page 96
        Page 97
        Page 98
        Page 99
        Page 100
    Back Cover
        Page 101
        Page 102
Full Text


U;na L. Ilag ia S. P. Madamba, Else M. Luis, Luzviminds P. Celino and
Avelins H. Malapitn

Mineral Oil Sprays on Wheat Seedlings Affect the Incidenceof Stem Rust, Leaf Rust
and Setorianodoium Lesions
Delfin B. Lapis

r.njnrml nt flininAin Ant af LUanan hi .int Watne Tran*man* .

A Cage Method for Studying Experimental Epidemiology of Rice Tungro Disease
K. C. Ling

The Capacity ofNephoteftix vkescensto Infect Rice Seedlings With Tungro
K. C. Ling

Effects of Rotylnchuilus reniformis inoculations on Mung Bean, Soybean and Peanut
N. B. Bajetand M. B. Castilla

Plant Parasitic Nemantodes Associated With Sweet Potato and Cassava in the
M. B. Castillo and L. R. Marana

Bacterial Leaf Spot, a New Disease of Poinsettia (EuphorblopulcherrimaWilld.)
A. J. Oulmie

Notes on Anthracnose Diseases of Ornamentals
Tricks H. ulmilo

Note: A Now Fruit Rot of Mango in the Philippines
Tricita H. Quimlo and A. J. Quimio

INDEXES TO VOLUMES 1 8,1965 1972
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:j: sS Ov iu e~i- ,i O -a 2 ***.: .*;~r *..*i''. .**., -. ; i w

Irounlea -lu


President: : D. B. LAPIS,
Vice-President' A. J. QUIMIi
Secretary: D. A. BENIC
Treasurer: L L ILAG,
Auditor: F. L NUQU
Board Members: K. C LING,


American Cyanamid Company. PI

Bayer Philippines, Inc. 622 Shaw

Canlubang Sugar Estate, Canlubai

Ciba-Geigy, Ltd., Basle, Switzerla

Dole Philippines, Inc., Madrigal B

FMC Corporation, Niagara Chemi

Hijo Plantation, Inc., Tagum, Dav

Hoechst Philippines, Inc., Corner

M.rnr..a.. r-,. I-n Filininca

:tober lbUZ


PLB, College, Laguna
UPLB, College, Laguna
), UPLB, College, Laguna
'LB, College, Laguna
IRRI, College, Laguna
RI, College, Laguna
IMO, UPLB, College, Laguna

:eton, New Jersey, U.S.A.

rd., Mandaluyong, Rizal

Calamba, Laguna

I., Makati, Rizal

Division, Middleport, New York, U S.A.

del Norte

neverr & Reliance Sts., Mandaluyong, Rizal

fe Bldg., Ayala Avenue, Makati, Rizal I

Merck Sharp & Dohme (Phil.), Inc., 113 United Nations Ave., Manila

Pfizer, Inc., Commercial Center P.O. Box 721, Makati, Rizal

Philippine Packing Corporation, P.O. Box 1833, Manila

Philippine Sugar Institute, West Ave., Diliman, Quezon City

Shell Chemical Company (Philippines), Inc., Shell House, 1330 Roxas Blvd., Mi

Tarlac Development Corporation, Hacienda Luisita, San Miguel, Tarlac

Union Carbide (Philippines), Inc., P.O. Box 56, Commercial Center Post Office,

Victories Milling Co., Inc. Victorias, Occidental Negros

-'-lbuI 1 a


Official Organ of the Philippine Phytopathological Society, Inc.


UPLB, College,

A. J. QUIMIO, Associate Editoi

R. B. VALDEZ, Associate Edit4


D. A. BENIGNO, Business Man


'LB, College, Laguna

IPLB, College, Laguna


UPLB, College, Laguna

apartment of Plant Pathology, UPCA, College, Laguna 3720. Philippine Phytopathology
)lished semi-annually (January and June) is the official organ of the Philippine
rtopathological Society. It is sent free to members in good standing and to Sustaining
ociates. For others, it ist 25 per year orP12.50 per copy I domestic 1 and $25 per
r or $12.50 per copy elsewhere, postage free and payable in advance. Membership in
Philippine Phytopathological Society: Information regarding membership will be
plied by the Secretary upon request Advertisements: Rates may be secured from the
:inans Mnnaar No endorsement nf any statement of claims made in advertisements is

. I

A new technique for extracting the In the laboratory, the virus was not
ice white-tip nematode, Aphelenchides transmitted by mechanical means, or
esseyi, utilizing the vertical migratory through the seed. The corn aphid,
behaviorr of the nematode, J. A. Rhopalosiphum maydis Fitch. transmnt-
Ldamo, C. P. Madamba and T. A. Chen. ted the virus after 24-48 hour acquisition
JPLB. feeding on Napier seedlings. Numerous
The literature related to the vertical flecks similar to those observed in the
migratory behavior of Aphelenchoides field occurred on the inoculated plants 2
to 3 weeks after the virus transfer.
esseyi and recent work conducted at the to 3 weeks after the virus transfer.
hematology Research Laboratory, UPLB, Unreported virus diseases of upland
re briefly reviewed. Experiments de- and root crops in the Philippines. D. A.
signed to test the efficiency of match- Benigno, F. C. Quebral, D. R. Pua and J.
ticks as structures for vertical migration A. Soria. UPLB.
nd nematode recovery are described. Peanut mottle, peanut rosette, mung
'he efficiency of recovery with match- bean yellow mosaic, cassava mosaic, cas-
ticks is compared with that of standard sava witches' broom, sweet potato mosaic
xtraction methods 1. e. funnel, sugar- and sweet potato green dwarf are the
rotation and sieves. The results indicated seven unreported virus diseases of upland
hat match sticks supplied continuously and root crops in the Philippines. Their
vith moisture over an 18-hour incuba- symptoms, modes of transmission, physi-
ion period were as efficient as the cal properties and host ranges are discussed.
standard procedures. This work presents a discussed.
Lew extraction technique utilizing the ver- Survey and identification of plant
ical migratory behavior of the nematode. parasitic nematodes associated with
banana R. B. Davide and F. T Gar-
Napier leaf fleck, a hitherto unreport- gantiel. UPLB.
!d virus disease. D. A. Benigno and E.
A nematode survey covering thousands
v. Imperio. UPLB. of hectares of 'Giant Cavendish' banana
The leaf fleck virus is a killer of Napier in Davao was conducted last August and
;rass (Pennisetum purpureum) It was September, 1973. In addition, a similar
irst observed at the experimental plots of survey was made on other banana varie-
he Dairy Training and Research Insti- ties in Samar, Leyte, Cebu, Negros Occi-
ute, U. P. Los Bafos last January 14, dental and also in Davao. Since this is
1974. supposed to be a nation wide under-
Under field conditions, the symptoms taking, more surveys will be conducted
observedd were the presence of numerous this year to cover banana areas in Luzon
minute, circular, yellowish dots on the and some provinces in Visayas and
eaves of the plant, the burnt-like appear- Mindanao.
unce of tips and margins of affected The findings indicate that the 'Giant
eaves, and the eventual death of the Cavendish' banana which is commercially
nlant na if Allin tn drlnm ht ..M-nmn in Minrlqann iQ hAina affaIctAd hv

nematodes. The following genera were some fields in July and November, 19
identified: Meloidogyne, Radopholus The "Isabela" strain was isolated fi
Helicot lenchus, Rotylenchulus, Tylen- about half of the fields surveyed al
chorhynchus, Hoplolaimus, Pratylenchus the road between Cauayan, Alicia,.
and Xiphinema Two species of these Mateo and Cabanatuan. In a field wl
nematodes, namely: Meloidogyne in- the "Isabela" strain was first detected,
cognita Chitwood and Radopholus similis isolates were collected from differ
Cobb are now causing serious damage on leaves and all except two were virulent
some banana varieties. M incognita IR20. This indicates that the "Isabi
causes the root knot disease while R. strain was the predominant strain.
simfis causes the black-head disease. Periodic surveys are being made in
Severe tip-over of 'Giant Cavendish' area to see if the strain is spreading.
banana plants due to R. similis infection
was observed in some old plantations in Tests of new fungicides against
Davao. R. similis had high population blast. F. L. Nuque and S. H. Ou. I[
density in roots of 'Giant Cavendish' Eleven new fungicides with Ben
showing the tip-over symptoms. In cases and Topsin M as standard chemicals v
where R. similis infection were severe, M tested against leaf blast in the I
incognita infection became less serious nursery. Three methods of applying
indicating the antagonistic effect of R. chemicals, namely, soil treatment, i
similis on the reproduction ofM. incognita. treatment and foliar spray were used.

Moraao ana omers were associated w
different genera of plant parasitic ner
todes particularly Meloidogyne, Rao
pholus, Helicotylenchus, Hoplolaim
Pratylenchus, Rotylenchus, Rotyl
chulus, Paratylenchus, Xiphinema a
others. The prevalence of these nematoi
on these varieties varied consideral

Evidence was obtained suggesting tl
the population densities of M. incogA
and R. similis was influenced by 1
banana varieties, age of plantations,
pH and plant conditions. R. similis I
high population density in roots of 1
over plants; and M incognita, in roots
non-tip-over plants.

Distribution of the "Isabela" strain
Xanthomonas oryzae. S. D. Merca,
de la Rosa and H. E. Kauffman, IRRI.

A survey of southern Isabela indici
that the "Isabela" strain ofXanthomo
oryzae is fairly widespread in the a
where the resistant variety, IR20,
ehnwin moderately severe infection

of Benlate and Topsin M. The ot
chemicals did not exhibit system
activities for leaf blast control afte
weeks under heavy infective condition
the blast nursery. In seed treatni
experiments using two rates, the res
indicated that the above chemicals
MKS 103 afforded good protect
against leaf blast. In the foliar sl
experiments, plants sprayed with F1, ]
17411, Homai, Hoe 22845, Hoe 25S
Hoe 22843, LS 54.255, Benlate, Tol
M, MKS 103 and Saprol had fewer lesi
than the control plants one week a
spraying. Two weeks after spraying, h
ever, the number of lesions on spra
plants increased considerably. The res
suggest that a weekly spray is require
protect the seedlings from leaf blast

Interactions between sheath bl
fungus isolates and rice varieties. S
Ou and J. M. Bandong. IRRI

Thirteen varieties varying in re:
ance or susceptibility to sheath bl
woep innclted at the flnwerina sl

varying in virulence. One week-old
grain cultures were inoculated on the
and 3rd leafsheaths. Infections were I
sed 8 days after inoculation by measu-
the length of lesions on the leafsheaths.

he fungus isolates showed great varia-
in virulence as regards isolate-variety
binations. However, variation was not
i when comparisons were based on
Average length of lesions produced by
isolate on the 13 varieties. The 13
ties differed considerably in resist-
or susceptibility to the 24 isolates.
mneral, resistant varieties had shorter
ns than the susceptible ones. Some
ses of variation existed but the inter-
ins were not distinctly differential
quantitative and qualitative resistance N
ce blast. S. H. Ou, F. L. Nuque and 9
Bandong. IRRI.
severe outbreak of rice blast oc-
0d in the upland rice varietal trial at
I in 1973. All varieties were infected
tatively, therefore, all were suscept- f
Quantitatively, however, they dif-
I greatly; some had only a few lesions
e others had many and the leaves
blighted. Two hundred lesions
ted at random were isolated and each
inoculated to the race differentials
three breeding lines which had very
intermediate and many lesions,
loculations with the 46 isolates
filed the existence of 11 Philippine
; of the pathogen. The hybrid line I
h had very few lesions was resistant I
) of the 11 races and to 45 of the 46 f
tes. The line with intermediate c
ber of lesions was resistant to 6 of a
1 races and to 37 of the isolates. The
with very many lesions was resistant t
aly 2 of the 11 races and to 8 of the r
isolates. Quantitative resistance is s
:fore the reflection of the spectrum of i
tance of each variety; the broader the t
trum, the higher the resistance a
ktitatively. Varieties with very broad r

national blast nurseries such as
!p, Carreon, etc. are expected to
ntain their resistance.

effect of period of wetness on in-
on rate of Pyricularia oryzae. S. H.
F. L. Nuque and T. T. Ebron. IRRI.
lice seedlings inoculated with spore
ension of P. oryzae were kept under
iture saturation (dew chamber) for
rent lengths of time from 4 to 36
rs. Infection rate was determined by
citing the number of lesions formed
he leaves 6 days after inoculation.
o lesion was formed in the 4 to 9
*s of wetness. A few lesions were
ked with 10 hours of wetness. Many
ns were observed on plants with 12
s of wetness. The number of lesions
further increased slightly with 24
36 hours of wetness.
ew period measurements in upland
lowland rice fields showed that dew
)d was often 2 to 6 hours shorter in
aud than in upland fields. It was also
d that dew causes the release of
lia and that high concentrations of
dia in the air occurs from midnight to
.M. These epidemiological observa-
; explain why blast is more severe in
ad than in lowland rice fields.

actionn tests of different accessions
rung bean against powdery mildew. -
Quebral, D. A. Benigno, J. A. Soria
D. R. Pua. UPLB.
hirteen different accessions and a
nnial mung bean obtained from the
A-SEARCA Gene Bank were tested
their reactions against powdery mil-
At the first disease assessment, i. e.,
lowering stage, 7 out of 13 accessions
perennial mung exhibited resistance
he disease, 4 were resistant-inter-
ate and 3 were susceptible. On the
id assessment, that is, at early pod
Ltion, only 5 out of the 7 accessions
showed resistance during the first
sment and the perennial mung bean
ined resistant. Of the remaining 8

accessions one was resistant-miermetual
one was intermediate-susceptible and
were susceptible.

Host influence on lytic pattern a\
plaque morphology in Xanthomonas o0
zae phages O. R. Reddy and S. H. C

The influence on the pattern of ly.
was studied with 10 distinct phages, v
Zoph, 6, 7m, 8, 15, 22, 27, 31, 41 aj
48. The host range pattern is affected I
one step growth cycle on certain hos
This is more evident when the indicate
strains used were not the original groin
of hosts of the phages. Host range
much altered when restricted hosts su
as BU3, C16, Ind 7-3, N4, Kx04, Kxi
and Pxo25 were used as indicators but
is not affected with B20-6, B14 and P,
40 which allow the multiplication of;
phages. The modification is not due
mutation of phage but is attributed
host-controlled modification of phag(
Plaque size was also observed
change drastically with different susceF
bible hosts. The plaque size of XoPh :
ranged from 2.0 2.5 mm on Pxo 46
to very minute (0.1 1 mm) plaques
C16. This change in plaque size is not di
to phage mutation but it is due to tl
restriction imposed by the host.

Yield loss estimates. I. Smut of sug
can. T. C. San Pedro and A. S. Lati.
Four Philippine commercial variety
of sugarcane were studied to determii
the loss in yield due to smut. Among tl
four varieties tested, Phil 5333 record
the least reduction in yield (34.27 p
cent). Phil 58260 with 71.80 per ce
suffered the highest yield loss. Reductic
in yield of Phil 56226 and 6019 due 1
smut were 66.70 and 59.59 per cer

"Isabela" strain of Xanthomonas oi
zae. T. Win and H. E. Kauffman. IR

When 100 isolates of Xanthomonr
oryzae, causal bacterium of bacteria
blight of rice were collected from
islands of the Philippines, one isolal
from Cauayan, Isabela overcame the resi
tance of IR20 and IR22. Addition
isolates collected from the area also hi
high virulence on IR20, IR22 and othi
varieties with a dominant gene for resi
tance. The isolates also had a distini
lysotype pattern when tested again:
eight bacteriophage isolates from Isabel
and Laguna. The strain is being called th
"Isabela" strain as it appears to t
distinctly different in virulence froi
other isolates in the Philippines.


(Department of Plant Pathology and D
Philippines at Los Bafios, College, Laguna.)

This study was supported in part by the


The mycelial growth and conidial germins
inhibited in Czapeks' agar infused with 1, 10,
inhibition progressed with increasing amounts of I
Corn grains treated with 0.1% thiabendazol
grains treated 1 or 2 days before inoculation
contamination after 2 weeks of incubation.
The fungicide had no adverse effect on the 1

Thiabendazole [2-(4-thiazoly)ben-
nidazole] is a broad-spectrum, systemic
ngicide. It is commonly used as an
thelmintic in animals including
mans. It is effective against many plant
eases such as black rot and foot rot of
eet potato (Martin, 1972), root rot of
an and tobacco caused by Thielaviopsis
sicola (Papavizas, et al., 1972), mush-
om disease caused by Mycogone
miciosa (Snel and Fletcher, 1971)
d certain turfgrass diseases (Goldberg
al., 1970). It has been effective against
rious postharvest diseases of fruits and
getables (Eckert and Sommer, 1967) in-
iding mango anthracnose (Spalding and
eder, 1972) and fungal rots of banana
ailey at al., 1970). It also reduced the
try of larvae of Heterodera tabacum in-
tomato, tobacco and eggplant roots
miller, 1969). Thiabendazole has a low
el of toxicity in plants and hence can

- A -Trl )~ I -


tment of Chemistry, University of the

od and Agriculture Research Program of


of Aspergillus flavus Link ex Fries were
100 ppm thiabendazole. The degree of
the time of inoculation with A. flavus and
ere all free of infection and aflatoxin

inability of treated corn seed.

- used against a wide variety of plant
Lthogens affecting different crops.
This study was conducted to deter-
ne the effect of thiabendazole on the
awth and sporulation of Aspergillus
vus Link ex Fries in vitro, and as seed
matment for the possible control of the
ngus and subsequent aflatoxin conta-
nation in corn. Aflatoxin is a potent
er toxin and corn is one of the most
ihly favored substrates for aflatoxin
nation. A. flavus can produce toxic
els of the toxin in less than 72 hours
er inoculation (Ilag et al, 1974). Infec-
In with A. flavus generally occurs after
- crop has been harvested, either while
.s drying or in storage.
Effect of thiabendazole on the growth,
orulation and spore germination of A.
!vus in vitro. Five A. flavus isolates
>m neanut corn cnnrna rniih rir.p

(palay) and soybean were inoculated on infection, aflatoxin content, and see
Czapek's agar infused with 0, 1, 10, and germinability. The test for infection wi
100 ppm thiabendazole. The Petri dishes done by planting surface-sterilized grair
containing the cultures were incubated at in malt salt agar medium in Petri dishe
room temperature (20-31 C). The growth Surface sterilization was carried out b
and sporulation of the fungus at various soaking the grains for 5 min in undilute
concentrations of the fungicide were Chlorox (5.5% NaOC1) after which ti
noted 7 days after inoculation. The iso- grains were rinsed in sterile water an
lates were also grown in Czapek's solution blotted dry prior to planting in dishe
with the fungicide (0, 1, 10, 100 ppm) The percentages of infection were note
and the dry weights determined after 7 5.7 days after planting. The aflatoxi
days in a shaker. To test the effect of the contents of the variously treated grai
fungicide on spore germination, spores of samples were determined following ti
A flavus from seven-day-old cultures extraction method and thin layer chrom,
were spread on thin agar blocks infused tographic analysis of Pons and Goldblai
with 0, 10, 100, and 100 ppm thiaben- (1965).
dazole. Each agar block was mounted on
a glass slide and incubated in a covered To determine if the fungicide had an
Petri dish lined with moist filter paper. adverse effect on the germinabiity oftl
The percentage spore germination in each treated corn seed, representative grai
treatment was determined after 24 hours. from each treatment were sown in so
contained in plastic trays. The germin;
Effect of thiabendazole on A. flavus tion rates were noted 4 days after sowinj
infection and aflataoin formation in corn.
Mature corn (DMR-2) grains that were RESULTS AND DISCUSSION
previously tested and found negative for
fungal infection and aflatoxin content Effect of thiabendazole on the growth
were used in this study. The grains were sporulation and conidial germination
aseptically placed in sterile 250-ml Erlen- A. flavus All the isolates of A. flav
meyer flasks (50g/flask). The amounts of exhibited no apparent growth in Czapek
thiabendazole powder were computed to agar infused with 10 ppm or 100 pp
deliver concentrations of 0.001, 0.01, and thiabendazole. The isolates grew in 1 ppl
0.1 per cent in 50-gram corn samples. The thiabendazole but the colonies wel
correct amount of thiabendazole was smaller than those that appeared in tl
added to each flask and the contents untreated medium (Table 1). The di
mixed thoroughly by vigorous shaking of weight measurements, however, indicate
the flask. To test the protective as well as that some growth occurred in Czapek
the eradicative property of the fungicide, solution with 10 and 100 ppm thiabend
some grains were treated with thiabenda- zole although growth at these two coj
zole one or two days before inoculation centrations was minimal (Table 1). T
with dry spores of A. flvus; others were observed difference regarding the pr
treated with the fungicide one or two
days after inoculation. In still another a
infused with 10 ppm and 100 ppl
treatment, the fungicide was added at the t a t a
thiabendazole and the absence of a]
time of inoculation. Controls consisted of p g
parent growth in Czapek's agar with tt
(a) inoculated grains with no fungicidal o i
treatment, and (b) uninoculated same amounts of fungicide may be illi
treatment, and (b) uninoculated grains
trea ad () n gins sionary rather than actual because growl
also with no fungicide. Duplicate flasks
... . could have occurred, but was impossib.

it they all responded in the same
inner. All were progressively inhibited
r increasing amounts of thiabendazole.

The degree of sporulation by the five
plates in Czapek's agar with 1 ppm
iabendazole and that in the untreated
medium were similarly profuse. There
is no growth and thus no spores formed
the higher concentrations tested.

Conidial germination of A. flavus was
pressed by 1, 10, and 100 ppm thia-
ndazole. The degree of inhibition was
-ectly proportional to the concentra-
in of the fungicide. The average per-
ntage germination after 24 hours was
% in medium infused with 1 ppm
abendazole, 24% in 10 ppm, 5.5% in
0 ppm, and 94% in the untreated
4dium. The hyphae in treated cultures

gus was able to form a minute amount
aflatoxin before it was killed by the
icide. Application of the fungicide
days after inoculation resulted in
' infection and the formation of 100.0
aflatoxin which is considered a toxic
iunt. Thus it is important that the
gicide be applied before inoculation.
is significant to note that natural
action of corn by A. flavus generally
irs soon after the crop is harvested;
illy while the grains are being dried
Y, 1973).

hiabendazole added to corn at 0.01%
Ited in only partial suppression of
;al infection and aflatoxin formation.
fungicide was more effective when
ied before inoculation than when
ied at the time of inoculation or after
ulation (Table 2). Nevertheless, this

e treated with 0.1% thiabendazole at grains.
time of inoculation with A. flavus and
se treated one or two days before Effect of thiabendazole on the germ-
culation were all free of infection and nation of corn seed. Corn seeds that
toxin contamination (Table 2). A were treated with .01 or 0.01 percent
eligible amount of aflatoxin (22.0 ppb) thiabendazole regardless of the time of
s found in grains that were treated fungicidal application, had a germination
h the fungicide one day after inocula- rate of 90-100% which was the same as
i although the fungus could not be the untreated seed. The fungicide there-
wered from the grains 7 days after fore showed no adverse effect on the
culation. This indicates that the germinability of the seed.

TABLE 1.Growth of 5 isolates of A. flavus after 7 days in Czapek's agar infused with
various concentrations of thiabendazole.

Thiabendazole Colony diameter* Dry weight*
A. flavus concentration in Czapek's agar in Czapek's
isolate (ppm) I (cm) solution (mg)

Peanut isolate

Corn isolate

Copra isolate

Rough rice isolate

Soybean isolate












Average of 4 determinations.
No apparent growth was observed.

'able 2. A. flavus infection and aflataxin c
grains that were variously treated w


Treatments 0.(

I. Fungicide was applied
one day after inoculation 8

II. Fungicide was applied
two days after inoculation 7

III. Fungicide was applied
at the time of inoculation 1 C

IV. Fungicide was applied
one day before inoculation 1

V. Fungicide was applied
two days before inoculation 2

VI. No fungicide was applied
on inoculated grains 1C

VII. No fungicide applied;
grains were not inoculated

Average of two trials with 2 replica

ent after two weeks' incubation of corn
2. 01 and 0.1 per cent thiabendazole

at Infection* Aflatoxin content*
(ppb BI)
0.1% 0.01% 0.1%
bendazole thiabendazole

0.0 2812.0 22.0

10.0 5625.0 100.0

0.0 3625.0 0.0

0.0 157.0 0.0

0.0 739.0 0.0

100.0 7500.0 7429.0

0.0 0.0 0.0

per trial.


1970. Use of thiabendazole for the postharvest treatment of bananas. J. Food
Technol. 5(1); 89-99.

ECKERT, J. W. and N. F. SOMMER. 1967. Control of diseases of fruits and vegetables by
postharvest treatment. Annu. Rev. Phytopathol. 5: 391-432.

GOLDBERG, C. W., H. COLE and J. DUICH. 1970. Comparison of systemic activity of
thiabendazole and benomyl soil amendments against Sclerotinia homoecarpa and
Rhizoctonia solani in the greenhouse. Plant Dis. Reptr. 54(11): 981-985.

ILAG, LINA L 1973. Aspergillus flavus infection of pre-harvest corn, drying corn, and
stored corn in the Philippines. Phi. Phytopathol. 9: 37-41.

MALAPITAN. 1974. Comparative aflatoxin contents of pre-harvest and post-
harvest corn. Kalikasan, Philipp. J. Biol. 3: 131-132 (Abstract).

MARTIN, W. J. 1972. Further evaluation of thiabendazole as a sweet potato seed
treatment fungicide. Plant Dis. Reptr. 56(3): 219-213.

MILLER, P. M. 1969. Suppression by benomyl and thiabendazole of root invasion by
Heterodera tabacum. Plant Dis. Reptr. 53(12): 963-966.

PAPAVIZAS, G. C., J. A. LEWIS and H. RUSSELL. 1972. Chemical control of black
root rot of bean and tobacco caused by Thielaviopsis basicola, Plant Dis. Reptr.
56(1): 15-19.

PONS, W. A., JR. and L A. GOLDBLATT. 1965. The determination of aflatoxins in
cottonseed products. J. American Oil Chemists Soc. 42: 471475.

SNEL, M. and J. T. FLETCHER. 1971. Benomyl [methyl 1-(butylcarbamoyl) -2-benzimi-
dazole carbamate] and thiabendazole [2(4-thiazolyl) benzimidazole] for the control
of mushroom diseases. Plant. Dis. Reptr. 55(2): 120-121.

by fungicides ar

d W. Fi REEDER. 1972. Post-harvest disorders of mango as affected

inoculation, with either Puccinia
of stem rust and 52-75% control
. lesser, but still significant degree
oil applied either before or after

:ible to the three pathogenic fungi:
ia graminis Pers. f. sp. tritici Briks
56), Puccinia recondita Rob. ex.
(Race UN2-64A), and Lepto-
ia nodorum (-Septoria nodorum
Uredospores of each Puccinia sp.

Wheat yields can be reduced by stem suscept
rust, leaf rust and Septoria nodorum. The Puccini
main control has been the development (race
of resistant varieties. Chemical control, Desm.
however, may be combined with or sub- sphaer
stituted for disease resistance in the Berk.).





ol of wheat foliar diseases, were collected from infected wheat plants
well (1968) pointed out that toxic in the greenhouse and until used were
ies offer a substantial obstacle to the stored at 5 C and 20% relative humidity.
stance of many protectant and Conidiospores of S. nodorum were
mic fungicides for chemical use. One obtained from cultures of two pathogenic
ability of avoiding this obstacle may single-spore isolates. The petri dishes with
o use a highly refined agricultural the sporulating cultures were flooded
-..'.;* <;ala Arl.+:11A a.t4 r n. rl than

then returned to the greenhouse bench.
The water suspension of s nodorum
conidia was also applied uniformly with
an atomizer to the seedlings, then kept in
a moist chamber for 24 hours and
returned to the greenhouse bench.
Two nonvolatile oils were tested for
their effects against the three pathogens
(Table 1). Oils were sprayed with a
Paasche artist's airbrush having a No. 3
nozzle and being attached by rubber
tubing to an electric pump. The oil to be
sprayed was in a 1-ml pipette calibrated
in 0.01 units. The pipette was held in
place in the fluid intake of the airbrush
by a brass fitting as shown by Calpouzos,
et. al. (1960).

The spray rate needed to produce a
desired oil deposit on the leaf surface was
determined by placing on the leaves
weighed pieces of aluminum foil 5 cm2.
The pieces of aluminum foil were re-
weighed after the plants were sprayed.
Repeated trials demonstrated that the oil

deposit could be controlled to an ac-
curacy strated that the oil deposit could
be controlled to an accuracy of 0.1 mg
oil/cm2 of leaf surface. The spray
deposits used in the experiment were 0.2,
0.4, 0.7, 1.1, 1.5 and 1.9 mg oil/cm2 of
leaf surface. Both leaf surfaces received
equal amounts of oil.
Treatments consisted of one oil spray
application either before or after the
seedlings were inoculated. When tested
against stem or leaf rust, the oil was
applied either 1 day before or 1-6 days
after inoculation. In the Septoria trial the
oil was applied 1 day before or 1-2 days
after inoculation. There were two spray
trials for each disease; in the first trial
Texaco 796 Spraytex C was used, and in
the second Esso Orchex 796 E was used.
The number of rust uredia or Septoria
lesions per primary of leaf each of the eight
seedlings in the pot was ascertained 12-14
days after the oil application. The average
uredial or lesion count for 10 replicate
pots was determined.

Table 1. Characteristics of oils used.'

Spraytex C Spray Oil

Viscosity at 1000F (SUS) 86.2 74.5
Unsulfonated Residue (UR) 95.0 96.2
Type Paraffinic Naphthenic
Distillation (ASTM D-1160
at 10 mm Hg)
10-90% distilled (OF) 405-504 409-463

* Both oils were straightt cut" not blended
ASTM American Society for Testing Materials
SData obtained from Texaco Co. Beacon, N.Y. or from Esso Research and Engineering.
Co., Baytown, Texas.

IcmL % % % % % % %

99 a 65 a 37 a 78 a 80 a 67 a 37
99 a 64 a 39 a 78 a 77 a 60 a 32
98 a 67 a 39 a 72 a 54 b 38 b 25
98 a 67 a 39 a 64 b 67 ab 23 c 21
96 ab 64 a 33 a 52 c 60 ab 9 d 13
94 b 77 a 28 b 57 c 20 c 3 de** 3

Mg of oil/cm2 of leaf surface
Average of two experiments observed 12-14 days after being sprayed. The check
equal 0 % or zero per cent. The average of number of uredia/check plant was: 76, 57,
118, 30, 149 and 137, respectively, for the data columns from left to right.

Within a vertical column, figures with no letter in common are significantly different
'0.05) according to Duncan's Multiple Range Test.
Not significantly different from the unsprayed check.

In stem rust, oil sprayed 1 day before
culation controlled 94-99% of the
dia as compared to the unsprayed
ck (Table 2). Oil sprayed 1-6 days
er inoculation reduced uredia less
rkedly, from 64-77% on the first day
3-37% on the sixth day. The influence
deposit rate became more pronounced
the time increased between inoculation
I subsequent spray. Although the seed-
gs sprayed on the sixth day were
sady showing flecks, the oil (at higher
es) prevented an appreciable number
flecks from developing into mature
In leaf rust, oil sprayed 1 day before
)culation controlled 52-75% of the
:dia, a lesser degree of control than in

able 2. Reduction in stem rust on wheat see

sm rust, but still significant when com-
red to the unsprayed checks. When oil
is sprayed 1-6 days after inoculation
nificant disease control was obtained
specially at the higher spray rates. How-
er the over-all degree of control from
rays after inoculation was noticeably
s than the control obtained from
raying 1 day before inoculation (com-
re the horizontal rows in Table 3). The
rcentage disease reduction from oil
rays 3-6 days after inoculation, at the
;her spray rates, was better than that
im sprays 1-2 days after inoculation.
e reason for this phenomenon is not
own. As in stem rust, good disease
ntrol (up to 37%) was obtained when
: oil was applied on the 6th day after
aculation when rust flecks were present.

i* i--- .n*. _;1it^ < / hF-O ^ o nrftor

wheat seedlings sprave

Spray* Disease reduction-'
rate Sprayed 1 day Day sprayed after inoculation
before inoc. 1 2 3 4 5
ag/cm2 % % % % % %

..9 75 a 28 a 32 a 56 a 56 a 54 a
1.5 72 a 29 a 28 b 51 b 49 b 53 b
I.1 64 b 17 b 22 c 42 c 43 c 33 c
).7 '62 bc 16 b 17 d 36 d 33 d 27 d
).4 57 cd 15 bc 13 e 23 e 19 e 11 e
).2 52 d 12 c 8 f 4 f** 0 f** 6 f

Mg of oil/cm2 of leaf surface.
x Average of 80 seedlings from two experiments observed 12-14 days after being
sprayed. The check equal 0 % or zero per cent. The average number of uredia/check
seedling was: 99, 196, 177, 170, 185 and 181, respectively, for the data columns
from left to right.
Y Within a vertical column, figures with no letter in common are significantly different
(0.05) according to Duncan's Multiple Range Test.
Not significantly different from the unsprayed check.

Table 4. The number of Septoria lesions on inoculated wheat seedlings sprayed with
mineral oil

Soray Septoria lesionsx

For Septoria nodorum, when the ino-
culated seedlings were sprayed 1 day
before or 1-2 days after inoculation, the
higher rates of oil significantly increased
the number of lesions (Table 4). These
results are in sharp contrast to those
obtained with the two rust diseases. The
effect of oil on the development of
Septoria lesions in general became less
favorable when the later the oil was applied.
In these experiments, the only sign of
phytotoxicity was stunting of the seed-
lings, ranging 16-62% of the unsprayed
check. Phytotoxicity increased as oil
deposit increased.

The data suggest that oil exert against
leaf and stem rust two modes of action,
therapeutic and protective. Therapeutic
action is indicated by the significant
control of disease when oil was sprayed
several days after inoculation because
penetration of the host by the fungus must
have occurred prior to oil treatment.
Protective action is indicated by the
enhanced disease control when the plants
were sprayed 1 day before inoculation.
Rowell (1964) has shown that when P.
graminis f. sp. tritici spores were placed
on oil-sprayed wheat leaves most of the
resulting germ tubes did not penetrate
stomata, but formed appressoria over

epidermal cells and developed no further.
Apparently it is possible to stop the
normal development of some leaf or stem
rust infections even at a stage as late as
flecking. It is not known whether the oil
is preventing rust disease by acting direct-
ly on the fungus or by increasing host
The enhancement of Septoria by oil
may be due to several possibilities. Sep-
toria spores may be sticking more firmly
to the oil-sprayed leaf during the misting
period, hence a larger number of spores
could be expected to result in more
infections and lesions. Oil may be lower-
ing the host's resistance to Septoria.
Further studies are needed to determine
which one of these or other explanation
is correct.
The results of this greenhouse study (i)
support earlier evidence that mineral oil
may control plant diseases by several
modes of action.[Calpouzos (1966, 1969)]
and (ii) Suggest that mineral oil may
control stem and leaf rust of wheat.
However, our experience with several
wheat varieties suggest that this crop will
be damaged by oil perhaps to the extent
of nullifying the beneficial effects of
disease control. Nevertheless, the use of
mineral oil to control rust disease on
oil-resistant plants other than wheat,
remains a possibility for further study.


CALPOUZOS, L. 1966. Action of oil on the control of plant diseases. Annu. Rev.
Phytopathol. 4:369-390.

.1969. Oils. D. C. Torgeson (ed) Fungicides, Volume II. Academic Press,
New York, p. 367-393.

W. A. BRUN, T. THESIS and C. COLBERG. 1960. A precision spray tech-
nique for evaluating oils for Sigatoka disease control on individual banana leaves
in the field. Phytopathol. 50:69-72.

ROWELL, J. B. 1964. Evaluation of oil as a carrier for nickel sulfate hexahydrate plus
maneb for control of wheat rust. Plant Disease Reptr. 48:154-158.

.1968. Chemical control of cereal rust. Annu. Rev. Phytopathol.


Assistant Professors, Department of
Plant Pathology, UPLB-CA Supported by FAR 019-74.


Hot-water treatment at 53 C for 10 min. effectively inhibited Diplodia rot develop
fruits of carabao mango cultivar artificially inoculated with Diplodia natalensis up to 3 day
Percentage of fruit rots due to the disease was also reduced in naturally infected fruits treated(

Recently, we demonstrated that hot- ones we described earlier (Quin
water treatment of fruits of carabao Quimio op. cit) except for the fol
mango at 53 C for 10 min. would control (1) six isolates ofD. natalensis (I
fruit decay due to anthracnose caused by were used in the thermal deatt
Colletotrichum gloeosporioides Penz (TDP) determination: (2) the sv

caused by D. natalensis P. Evans i
dered second to antracnose in impor
as a post harvest disease of Phili
mango fruits, was significantly reduce
hot-water treated, naturally-inf
fruits. This paper reports on addii
evidence supporting this observation

The methods used were similar ti

Table 1. Isolates of Diplodia n

Isolate Origin
A Laguni
B Bulaca
D Cebu
E Zamba
G La Uni
I Albay

S ures; tk) me moculum vL-teou is(
S used in the study on the effect oi
S water treatment at 53 C. for 10 mi
S artificially inoculated carabao m
1 fruits, consisted of spore and my
1 suspension with a concentration equiv
to 20 times 0.3 O.D. on a Bed
Spectronic 20. The inoculum was i
duced into 2 inoculation points on
test fruit.

mis from carabao mango used in TDP c

Date Isolated


The TDP of spore and mycelium ofD.
talensis was between 54-55 C and
-56 C respectively (Table 2). The
sults showed that the spore was a little
:re sensitive to hot water than the
turally infected fruits and showed signi-
-ant reductions of fruit decay (Table 3),
it did not completely control the

In succeeding experiments, hot-water
eatment at 53 C for 10 min of fruits
tificially inoculated with the fungus up
S3 days earlier completely prevented
sease development (Fig. 1). Since our
preliminary works on pathogenicity of
ie fungus had shown that infection by
lore and mycelial inocula would be
established in 2 to 3 days after inocula-
on, these results suggest that latent
ifections, which could possibly occur on
green fruits (Halos, 1970), may be elimi-
ated by hot-water treatment The results
f hot-water treatment of non-inoculated
iycelium and that the TDP of D. nata-
nsis overlaps the injury point of Cara-

iits at which hot-water treatment could
used for controlling the major fruit rot
thogens of Philippine commercial
ingo varieties.

Diplodia natalensis is primarily a stor-
: problem of mango fruits. It invades
: fruits primarily through the stem-end
ich could probably occur while the
lits are still green (Halos, 1970) or
cassionally, through injuries on the
lit skin. Our observations of fruits
ened in bamboo baskets ("kaings")
th capacities up to 100 pieces each
awed that it spreads primarily by con-
:t of mycelial growth from infected
lits. This would indicate that the initial
>culum prior to storage would deter-
ne the extent of fruit damage and that
mage due to secondary disease cycles
sing from conidia of initial infections is
n-existent because sporulation of the
igus would occur at a time when fruits
ve reached maximum ripening and are
idy for disposal.
Hot-water treatment at a temperature
ich would not injure the fruits, al-
)ugh would not completely eliminate
tial inocula perhaps due to deep-seated


Fig 1. Carabao mango fruits artifice
bers represent 24, 48, 72, hrs
53 C water. Control and cc
control inoculated fruits, resp

Table 3. Effect of hot-water treatnr
with Diplodia natalensis.


Treatments Trial I

Control 44
Hot-waterb 6

a Two trials with 2 replicates each, 50
incubation in "kaings" at room t
b Fruits soaked at 53 C for 10 min.


anthracnose by hot-water treatme
HALOS, P.M. 1970. Sporulation by I
logy of infected mango fruits. MS

inoculated with Diplodia natalensis. Num-
ter inoculation before soaking for 10 min. in
ol-INOC are the control uninoculated and
ively. Picture taken 10 days after treatment.

t of carabao mango fruits naturally infected

eased Fruitsa

Trial II Mean

76 60
12 9

tits per replicate. Data recorded 14 days aft
erature. All diseased fruits were due to I


1973. Postharvest control of Philippine man
Phil. Agric. 58: 138-146.
odia natalensis Pole-Evans and the histopatt
sis, UPCA, College, Laguna. 64 p.


K. C.
Plant Pat
(The International Rice Researc

Grateful acknowledgement is made for td
M.P. Carbonell, and A. V. Villegas.


To enlarge its testing capacity, the mal
testing rice seedlings for resistance to the tui
seedlings with viruliferous Nephotettix virescen
in the previous method. Therefore, the testing
the previous method. To keep the insects in
between inoculations for reacquisition feeding.
the rice seedlings in the newly styled inoculate
lighting in the cage.


institute, Los Bafios, Laguna)

:hnical assistance of Messrs V. M. Aguiero,


preening method, developed previously for
disease, was improved by inoculating rice
ce a day instead of once a day as was done
Aity of the new procedure is twice that of
re, they are confined on diseased plants
distribution of the viruliferous insects on
cage is managed through regulation of the

nt has been exposed to the virus seedlings per insect. The present paper
section. Since a plant can be infected reports on efforts to seek ways to
h the virus by the insect vector under increase the number of seedlings inocu-
her natural or artificial conditions in a lated by one insect
Id or in a greenhouse, the varietal
actionn to a virus disease transmitted by MATERIALS AND METHODS
leafhopper vector can be tested by
her of these two methods, although the Transmission study. The colony of
ificial method is generally preferred green leafhopper, Nephotettix virescens
:ause it is easier to control. (Distant), used in this study was reared
A disadvantage of the artificial method on Taichung Native 1 (TN1) rice plants in
the greenhouse, however, is its limited screen cages. The adult insects became
ting capacity, which is determined viruliferous when confined on tungro-
inly by the quantity of viruliferous diseased TN1 plants for an acquisition
ects available for inoculating test seed- access time (Federation of British Plant
gs. With the mass screening method for Pathologists, 1973) of 3 to 4 days before
ting rice varieties for their resistance to the transmission test Then they were
Igro disease, developed in 1965 (Ling, confined either on diseased plants in
59), 928 seedlings can be inoculated in cages or on diseased leaves in tubes for
pots a day. This method was satis- reacquisition feeding.
tory for several years, but recently, the One-week-old TN1 seedlings were
reased demand for testing has made it placed individually in test tubes to which
:essarv to increase the canacitv of the viruliferous insects were transferred indi-

diately afterwards the tubes were cover
with polypropylene culture tube caps
prevent the insects from escaping. Afte:
given inoculation access time (Federati
of British Plant Pathologists, 1973), t
insects were either released or transfer
to other test seedlings or to a virus sour
for reacquisition feeding. The seedlir
were transplanted into pots and kept
the greenhouse for symptoms of t
disease to develop. The infected seedlir
served as indicators of the infectivity
the insects. Because the seedlings we
inoculated by individual insects, the pi
centage of infected seedlings was equal
the percentage of infective insects.
To determine the inoculation acc<
time for the mass screening method, f
each trial viruliferous N. virescens of t
same colony were transferred individual
into test tubes. Each tube contained
test seedling, where the insects we
confined for periods between 1 and
U V -+., -4. .-_ --A t-- __ar

and 4.5 hours for reacquisition between
the two inoculations. The other combine
tion was 2.5 hours for each inoculatic
and 3.5 hours for reacquisition.
In the mass screening, the insects ai
used repeatedly for inoculation to dete
mine the ability of the adult insect 1
transmit the virus twice a day for the re
of its life, serial transfers were used in tl
study of the infectivity of the insec
with reacquisition feeding before eac
Inoculation cage. In mass screenin
the key factor determining the ur
formity of inoculation is the distributic
of viruliferous insects on test seedlings
the inoculation cage. The characterist
tendency of the insect to move towa:
light was used to facilitate the ev4
distribution of the insects on test see
lings in the inoculation cage. A new sty
of inoculation cage was fabricated. TI
four sides and the top of the cage consi
-,r- _41 -1k --A .A~~trl lk~

in order that the same insects could be of the four sides. Thus, the distributic
used to perform two or three inoculations of the insects in the cage could t
during the working hours in a day. controlled by regulating the opening (
the sliding doors. Once the insects a
The length of time for two inocula- evenly distributed on the test seedling
tions with a reacquisition feeding be- the sliding doors are closed to prevel
tween them in a day is limited by the light from entering the cage there
number of regular working hours in the minimizing the movement of the insec
day. In a 9-hour working day, the total in the cage during inoculation.
time for inoculation and reacquisition
cannot exceed 8.5 hours because the Testing infectivity of insects in i
remainder of the work time is needed for inoculation cage. In testing rice vari
handling test seedlings, diseased plants, ties or lines for their reaction to tung
and insects. The number of hours for disease by the mass screening method
reacquisition is, therefore, the time both resistant and susceptible chec
remaining from 8.5 hours after the should be included in every inoculatio
number of hours for two inoculations has This reduces the screening capacity I
been substracted. Two combinations of one-eight (13 percent) because each in
-a'r^- __ I _1__ -I- ---lsn n -anr n!_ ,! _- ^ +n-n+ --k1., 14 L M-

240 insects from six replica

a es. une com- in

11 Uli Ui LVL V4iiDi Ul IIIIU jA
susceptible to tungro disease and can
erve as a susceptible check. However, a
susceptible variety may not always be
)resent among the test varieties or lines in
sach inoculation. Thus, a test was devel-
>ped for checking the infectivity of the
nsects in each inoculation cage for every
noculation. Immediately before each ino-
:ulation, 40 insects are sampled from
each cage and tested individually in test
ubes for their infectivity, and these
results serve as the control of the
Insect damage A seedling infected
by tungro virus sustains damage not only
from the virus but also from the insect

A 1U flltfAOo -n1ut 5 a-Ltt-tSu -1aL vUv
ised to determine both the resistance and
olerance of a rice variety to the tungro
disease. However, the screening test
should emphasize the percentage of in-
ection because the characteristic of
resistance to infection by a rice variety is
)referred to mere tolerance of the
When measuring the tolerance of a rice
variety to tungro disease, considerable
ime is required to ascertain the severity
f the disease and to allow the infected
plants to mature to measure the effect on
rain yield. During such a lengthy period
4-5 months), the plants must be main-
lined in the greenhouse where space is a

UmUanaua S U o. ..-** ...... house as soon as the percentage of infec-
loculated seedlings, it can be reduced by tion of the varieties are determined. This
sing fewer insects per seedling or short- shortens the time the plants are in the
ning the duration of the insect feeding, greenhouse and thus, there is not ade-
o evaluate the damage to the seedling quate time for the plants to develop to a
caused by the insect vector, five virus-free sufficient extent to allow any measure-
nsects were confined on each seedling for ment of the severity of the disease on the
2.5 or 8 hours. The seedling height was rice varieties.
measured at the start of the experiment
nd during the subsequent few weeks. When severity readings are desired,
after taking the reading of the percentage
Severity reading The level of reduc- of infection, seedlings of the rice varieties
ion in the grain yield can serve as a being tested can be transplanted in the
riterion by which to assess the degree of field. The reading of the severity of the
resistance of a rice variety to a virus disease on the rice varieties can be made
disease following inoculation with the at any time after transplanting.
'irus. The yield reduction in this case
:onsists of both the percentage of infect- Evaluation of the improved method -
d plants (indicating resistance to the The improved mass screening method was
infection) and severity of disease of the evaluated by using a blank test and by
infected plants (indicating tolerance of actual-testing the rice varieties and lines
:he disease). Theoretically, the yield of for their resistance to tungro disease. For
ion-infected plants should not be the blank test, 160 pots each containing


Inoculation access time and traj
mission. The length of the inoculati
access time influences the success
inoculating a seedling using a viruliferc
insect If the time is shorter than t
inoculation threshold period (Federati
of British Plant Pathologists, 197:
obviously the seedling cannot becoi
infected, and the percentage of infect
seedlings is zero. On the other hand, ev
with an excessively long inoculati
access time, the percentage of infect
seedlings cannot be greater than t
percentage of active transmitters (Li
1972) of the insect when the seedlings
inoculated by individual insects. Hen,
within these two extremes of time, pi
longing the inoculation access ti
should increase the percentage of seedli
infection, but beyond the maximum
range, further prolonging the inoculati
access time will probably not affect t
transmission of tungro virus.
In studying the effect of inoculati
access time on the transmission of tung
and similar diseases, several investigate
(John, 1968; Singh, 1969; Gglvez et
1971) reported a gradual increase in t.
positive transmission when the inocul
tion access time was lengthened. A d
crepancy that might be due to samr;
size occurred in these results.
The number of seedlings inoculat
per insect daily can be increased only 1
shortening the inoculation access tin
To ascertain the minimum time for t
inoculation access time, 3,104 of a tol
of 4,551 seedlings (excluding test see
lings that died before the disea
symptoms developed) inoculated becar
infected. The percentage of infected see
lings increased gradually as the inocul
tion access time lengthened from 1 to
hours (Table 1). The increase was stat
tically significant when the time w
lengthened from 1 or 2 to 3 hours (10
14 percent), while only a 4 perce:
increase was identified when the time w
'1-,^1- C f.-' lt

For mass screening, if the previous
used inoculation access time of 7.5 hou
was shortened to about 3 hours, tl
infection percentage would probably n
be significantly reduced.
Number of inoculations per day. -
study of whether an insect could perform
two or three inoculations in a da
revealed that the percentages of infect
seedlings in the second and third inocul
tions were lower than the percental
from the first inoculation on the san
day even when the second inoculatic
access time was longer than the fir
(Table 2). The infection may have bee
low in the second inoculation because tt
tungro virus does not persist in the insec
Thus, the infectivity of the inset
decreases gradually with time after th
acquisition feeding (Ling, 1966). Fc
mass screening, it is not desirable to hav
significant difference in seedling infection
of a variety between two inoculations.
Maintaining infection level If tt
infectivity of the insects could be mai
tained for the second inoculation, tl
difference in percentage infection b
tween the first and the second inocul
tions on the same day might be les
Although the percentage of infection i
the second inoculation would not I
increased by prolonging the inoculatic
access time, there are two alterna
approaches: 1) increase the ratio i
insects to rice seedlings in the secor
inoculation by reducing the number i
seedlings to be inoculated while co
comitantly retaining the same number ,
insects in the second inoculation as th
of the first inoculation, and 2) provii
the insects with a reacquisition feeding <
a virus source before the second inocul
tion. The first approach might cau
differences in insect damage to the see
ling and less seedlings would be inoc
lated. Therefore, the present stui
focused on the second approach where
the infection level of the second inocul
tion is maintained through reacquisitii

Inoculation Inoculation Inoculated Infected
iculations time access time seedlings seedlings1
o./day) (hours) (hr) (no.) (%)

2 0800 to 1030 2.5 2094 63 a
1030 to 1530 5.0 2096 54 b

Averages of 23 and 50 trials for two and th
followed by a common letter in each numi
:antly different at the 5% level

noculations a day, respectively. Means
)f inoculations per day are not signifi-

Lengthening the acquisition acce
time within 24 hours is known to gradus
ly increase the percentage ofN. virescel
which become infective with tungro ar
similar diseases (Rivera and Ou, 196
John, 1968; Lim, 1969; Singh, 196
Gilvez, et. al., 1971). Hence, the lengi
of the reacquisition access time may all
affect the infectivity of the insect. With
2-hour inoculation access time for tv
inoculations in a day, using a 4.5-hour r
acquisition access time between the tv
inoculations, 61 and 71 percent of tl
seedlings were infected during the fir
and the second inoculations, respectively
When 2.5 hours were used for each inoc
lation wth a 3.5-hour reacquisitic
period, the results were similar; 64.3 ai
64.2 percent of the seedling were infect
for the first and second inoculation

Table 3. Percentage of tungro-infectec
tettix virescens at different

Inoculation I:
Inoculations time a
(no./day) (hours)

1 0800 to 1600

Another experiment involving
trials, an 8-hour inoculation access t
as a check confirmed the above find
The infection level of the first and
second inoculations of 2.5 hours eact
the same day with a 3.5-hour reacqi
tion access time between the two inoc
tions was similar 499 and 50.0
1 ,"t "

at the 5% level.

OT insects

8-hour inoculation
Once a day 08






|i n 2.5-hour inoculation
(, n twice a day 0800 to 103

access time
to 1620

ess time
ind 1400 to 1630

Consecutive days

itly, two sets an in,

the same insects in one day. were generally lower than the calculat
Serial transmission. A test to deter- figures when the calculation was based
mine whether an insect maintained its the preceding formula and using t
ability to transmit the virus twice a day percentage of infective insects at a 2
for the rest of its life showed that some hour oculation access time. To achie
insects remained infective almost until about 98 percent infected seedlings fo
they died regardless of one or two ino- susceptible variety, five to six viruliferc
culations per day (Fig. 1). Furthermore, insects per seedling were used in mr
nowmarked difference in the percentage of screening trials. Such an infection le
infected plants appeared between inocu- would require 2,320 to 2,784 viruliferc
lating once and twice a day, nor between insects in each inoculation cage contain
the first and the second inoculations. 16 pots of 29 seedlings each.
Number of insects per seedling The Insect damage. Using the criteria
infection level or percentage of infected of reduction in the amount of growth
seedlings of a rice variety susceptible to assess insect damage, seedling growth v
tungro can be raised by increasing the found to be retarded even when 1
ratio of viruliferous insects to rice seed- seedlings were infested by five virus-f
ling because first, not every viruliferous N. virescens adults for 2.5 hours. He
insect is infective. Second, N. virescens ever, the degree of growth retardati
.... ....... ... ...... : +; wao ra.diinm d when the infestation acc

Table 4. Percentages of tungro-infected Taichung Native 1 seedlings inoculated by one to
five viruliferous Nephotettix virescens for an inoculation access time of 2.5 hours.

Viruliferous Inoculated Actual infected Calculated infected
insects seedlings seedlingsI seedlings2
(no./seedling) (no.) (%) (%)

1 458 73.6 73.6
2 449 88.2 93.0
3 451 95.5 98.2
4 448 96.0 99.5
5 427 97.8 99.9

1 Average of 12 trials.
2 From 1 (1 0.736)n, where n is the number of insects per seedling. The difference
between calculated and actual percentages of infected seedlings is not statistically sig-

ible 5. Average height of 35 Taichung Natii
ed by given green leajhoppers (Nep

cross time Seedling hei
(hr) 0 wk 1 wk

0 (check) 21.0 a 34.3 a
5 20.6a 323b
0 20.8 a 29.6 c 4

Means followed by a common letter in e
the 5% level.

finedd with the diseased plants from
i30 to 0800 hours the following morning.

3) Increase the number ofviruliferous
sects to five or six per seedling used for
oculation. This ratio achieves a prob-

seedlings 0 to 4 weeks after being infest-
ttix virescens) per seedling for 2.5 and 8

k 2 wk 4wk

a 73.9 a 77.7 a
b 70.1b 78.4 a
c 67.7 c 79.7 a

:olumn are not significantly different at

iility of about 98 per cent seedling
fection of a susceptible variety of rice.
4) Distribute the insects evenly on the
it seedlings by using a newly styled
aculation cage.
5) Determine the infectivity of the

insects in each inoculation cage for e
inoculation by sampling the insects
mediately before inoculation and tes
them individually in test tubes. The
centage of infective insects determ
from these tests serve as the control
the respective inoculations.

Seeds of a e varieties

(Soaked in water)
Feeding Transplanting *

Smae2 weeks

Fig 2 Diagram of the improves
to tungro diseaswater)
Reading of percentage of infected seedlings

Fig. 2 Diagram of the improved
to tungro disease-

Y 6) Transplant the test seedlings
r field after the percentage of infection
g been determined from observations o
- inoculated seedlings grown in the g
I houses (for symptom development;
f further observation of severity or
infected plants if desired.

Rep. 1 Rep. 2
2- to 3. insects
leaf stage
11 days old
(16 pots per cage)
1. Five to six insects/seedling.
2. Seedlings are exposed to viru-
Irferous insects 0800 to 1030
and 1400 to 1630 for inocu-
3 After inoculation, pots are
removed and diseased plants
E are placed for maintaining in
fectivity of the insects in the
cage for next inoculation.

ass screening method for testing varietal rest

flank test To evaluate the im-
ved method, TNI seedlings were
:ed for 5 consecutive days. Each of 1
160 pots had 70 to 100 percent
ected seedlings for the first inocula-
i and 60 to 100 percent for the 1
and inoculation on the same day. The
fficients of variation were 10.2, 4.4, ]
, 9.0, and 6.0 percent for the first I
culation on 5 consecutive days, and
,5.0, 5.3, 7.1, and 11.6 percent for
second inoculation. The overall a
ins of the infected seedlings of the
inoculations did not suffer apprecia- 1
(93.4% versus 93.9%). No consistent
Id was observed for each of the 5 days
er. Statistically speaking, five pots are
d to keep the standard error of the
in under 10 percent unless the ex-
nie cases can be avoided.
lata from screening test. Using the
-oved screening method, 2,706 entries
ut 540 entries per month) were
d for tungro resistance from August
)ecember, 1972. Inoculations were
Le only 5 days a week, because rice

s of some entries did not germinate,
he rate was lower than the theoretical
imum which is about 700 entries per
ith. Among the test entries, 135,174
lings survived after the symptoms of
o7 disease developed. This number
about 14 percent less than the ex-
ed number, either because the seed-
; failed to develop before inoculation
because the seedlings died after inocu-
*n. Of the inoculated and surviving
lings, 87,374 seedlings were infected.
mean percentages of infected seed-
in two replicates which varied from
to 1.1 percent, did not differ appre-
.y regardless of the month.
large variations in the percentage of
cted seedlings between two duplicates
in entry were observed on certain
i (Table 6). On the average, dupli-
s of about only 9 percent of the test
ies differ in percentage of infected
lings by more than 20 percent.
lies designed to reduce the variation
inder way.

percentage of infected seedlings between two duplicates of an entry tested by
the improved mass screening method for tungro resistance (August to December

ange of Entries (no.)
(%) Aug. Sept Oct. Nov. Dec. Total Percent

0 29 109 23 49 26 236 8.7
to 10 252 381 294 408 243 1578 58.3
1 to 20 145 120 125 144 144 648 24.0
1 to 30 56 25 27 25 44 177 6.5
1 to 40 22 7 8 3 8 48 1.8
1 to 50 6 3 3 1 4 17 0.6
1 to 60 2 0 0 0 0 2 0.1
Total 512 645 480 630 439 2706 100.0


terms in plant pathology. Phytopath.

microscopy of a rice tungro virus stra

Los Baflos, Philippines. 266 p.

JOHN, V. T. 1968, Identification and char
India. Plant Dis. Reptr. 52:871-875.

LIM, GUAN SOON. 1969. The bionom
Ishihara and transmission studies on i
Min. Agr. Coop. Bull. 121, 62 p.

LING, K. C. 1966. Nonpersistency of th
tettix impicticeps. Phytopathology 5
.1969. Testing rice varieties fc
Proceedings of a symposium on th
1967, Los Bafios, Philippines. Johns I

.1972. Rice virus diseases. Intc
Philippines. 142 p.

RIVERA, C. T. and S. H.OU. 1965. Leafh
Plant Dis. Rept. 49:127-131.

SINGH, K. G. 1969. Virus vector relations
Soc. Japan 35:322-324.


THOLOGISTS. 1973. A guide to the usi
pap. no. 17, 55 p.

. A. MIAH. 1971. Transmission and eleci
in. Phytopath. Z. 70:53-61

.CH INSTITUTE). 1970. Annual report 15

acterization of tungro, a virus.disease of ric

lics and control of Nephotettbi impicti
its associated viruses in West Malaysia. Mala

e tungro virus in its leafhopper vector, Me
>r resistance to tungro diseases, p. 277-291
Le virus diseases of the rice plant, 25-28 A
FJ-1-_ D-ao D.l; _


Plant Pathologist
The International Rice Research Institute
Los Bafios, Laguna

The author is deeply indebted to Dr. Kwanchai A. Gomez for statistical
and M. P. Carbonell for technical assistance.


A cage method was developed to simulate and substitute for a field. The method can be
used for studying the experimental epidemiology of rice tungro disease, particularly for
determining the effect of various factors of insect vector, virus source, host, and environmental
conditions on the incidence of tungro disease in terms of percentage of infected seedlings. The
method was evaluated by studying each of the steps of transmission cycle of tungro virus in the
cage. The effect of number and duration of caged viruliferous insects on the percentage of
infected seedlings was demonstrated by the cage method. However, the method may not be a
suitable vehicle for the study of all factors affecting the disease incidence because of the wide
range of the factors.

The epidemiological studies of rice
tungro should cover all aspects of the
disease in population especially those
factors which affect the outbreak and
spread of the disease. The goal of epide-
miological studies of the rice tungro
disease is to find an economically feasible
way to control the disease. The epidemio-
logical results can be used to formulate
methods to forecast the disease, to pre-
dict yield losses, and to develop recom-
mendations for control measures.
Two approaches to investigate the
epidemiology of the rice tungro disease
are statistical and experimental or ana-
lytic and synthetic. The statistical ap-
proach includes collecting, collating, and
analyzing observations about the inci-
dence of the disease and information of
existing factors related to the disease in
the field under natural conditions. The
analysis of the data helps to identify the
relative importance of the various factors
that affect the outbreak of this disease. In
the experimental approach, the effect of
factors, individual or combined, on the

incidence of the disease in the greenhouse
or in the field under controlled condi-
tions are studied. Careful interpretation
of the experimental results, observations,
data, and their statistical analysis lead to
the synthesis of factors that reveal a
logical pattern or mathematic model of
the disease.
The major difficulties of studying ex-
perimentally the epidemiology of a
leafhopper-transmitted virus disease in-
clude the limited number of available me-
thods of study, the complexity of the fac-
tors, the interaction of the factors, the in-
stability of the factors, and other un-
known items.

A cage can be used to simulate and
substitute for a field for studying the
experimental epidemiology of rice tungro
disease because the cage can contain all
essential factors, such as insect vector,
virus cource, and test seedlings, for
spreading the disease. These factors, indi-
vidual or combined, can be varied, as an
investigator's desire, among the cages in

oraer to aetermne mte enect or these
factors on the disease incidence, in terms
of percentage of infection of the test
seedlings. Furthermore, the cages can be
kept under various environmental condi-
tions for investigating the effect of the
conditions on the disease incidence.
A fundamental step in evaluating the
cage method as a suitable vehicle for
studying the experimental epidemiology
of rice tungro disease is to ascertain
whether the insects could transmit the
virus while caged.
When virus-free green leafhoppers are
considered as the initial point of the
cycle, the transmission cycle of the rice
tungro virus (Ling, 1972) can be divided
into four steps: 1) the virus-free insects
move to diseased plants; 2) the insects
acquire the tungro virus by feeding on the
diseased plants; 3) the viruliferous insects
move to healthy plants and inoculate the
plants by feeding; and 4) the plants are
infected as revealed by the disease
symptoms. The first three steps involve
the insects. Each of these three steps can
be evaluated when the insects are in the
cages. For the fourth step, the test
seedlings can be transferred to a green-

Fig. 1. Cages for studying experimental ep

house to allow the symptoms ot tme
disease to develop.
This paper reports the results of eval-
uation of the cage method and the effect
of number and duration of caged virulife-
rous insects on the disease incidence as
determined by the cage method.


Metal cages used in this study were 52
x 52 x 71 cm and were covered by a
metal screen of 28 mesh (Fig. 1). The
cage accommodated sixteen 12-cm pots
in which rice seedlings were transplanted.
The colonies of green leafhopper, Ne-
photettix virescens (Distant) were reared
on Taichung Native 1 (TN1) rice plants in
screen cages under Los Bafios, Philippines
conditions. They were confined on
tungro-diseased plants for 4 days to make
them viruliferous before being used in
Test plants of rice variety TN1 were
grown in pots in the greenhouse. The
diseased plants were infected by arti-
ficial inoculation using viruliferous in-
sects. Plants that were exhibiting tungro
symptoms were used in the experiments.

biology of rice tungro disease.

Movement of insects to rice plants. Movement of insects from rice plants
To examine whether movement of insects to rice plants. To investigate whether
to diseased plants occurs in a cage, insects move from diseased or healthy
healthy and tungro-diseased plants which rice plants to other diseased or healthy
were similar in height and in number of rice plants in a cage, virus-free insects
tillers, one pot each, were placed in a cage were introduced into a cage containing
at a distance of about 25 cm between the either a pot of healthy plants or a pot of
two centers of the pots. The healthy and diseased plants. After the insects had
diseased plants were arranged alternately settled on the plants and after the insects
on the left and right side of the cage in which had not settled on plants had been
the replicates, removed from the cage, one pot each of
Sc w 1) healthy and diseased plants were placed
The cages were: 1) without any cover
for daylight; 2) with cover of black cloth the cage. The centers of the three pots
were at a distance of about 25 cm to each
for darkness; and 3) with cover of either were at a distance of about 25 cm to each
So g c r other. For the next 3 days the number of
yellow or green cellophane for colors.
insects on the plants in each pot were
The virus-free N. virescens adults were counted daily. The number of insects on
introduced into the cages by releasing the plants indicates the movement of the

rhem trom an aspirator on the tloor ot
he cage at a distance of about 25 cm. to
ach of the centers of the pots.
The tests were conducted either during
he daytime or from 1600 to 0800 the
allowing morning. After the insects had
een confined in the cage for 2, 8, or 16
ours, both pots were carefully removed
rom the cage and transferred to two
separate empty cages. The number of
sects on the healthy and diseased
lants, and at other places in the cage
tere counted. The number of insects on
he plants indicates the movement of the
sects to the plants.

Acquisition of the tungro virus by
sects. To determine whether insects
an acquire the virus in a cage containing
different proportions of diseased and
healthy plants, virus-free insects were
onfined in cages with 1, 2, 3, and 4 pots
f tungro-diseased plants and 3,2, 1, and
pots of healthy plants to make a total
if four pots in each cage. After confine-
ient of the insects in the cages for 1, 2,
7, and 14 days, the insects were
impled from each cage and tested indivi-
ually in test tubes with healthy TN1
eedlings for an inoculation access time
Federation of British Plant Pathologists,
973) of 1 day. The infection of seedlings
idicates the insects acquired the virus.

insects rrom me ongnai nost plants to
theirr plants.
Viruliferous insects and seedling infec-
ion. To study whether the cage me-
thod can demonstrate the effect of num-
ber of viruliferous insects and duration of
confinementt of the viruliferous insects on
he disease incidence, 50, 100, and 400
iiruliferous insects were introduced into
:ages containing 400 12-day old TN1
healthy seedlings in 16 pots each cage.
The insects were released either at the
:enter or at a comer of the cage and were
confinedd in the cage for 1, 4, or 7 days.
After the period of confinement, the
nsects were released, and the seedlings
were transferred to a greenhouse to allow
he symptoms of the disease to develop.
Three weeks later, infected and non-
nfected seedlings in each pot were count-
ed. The percentage of infected seedlings
indicate the incidence of the disease.


Movement of insects to rice plants. -
Vhen virus-free N. virescens adults were
itroduced into the cage with healthy and
iseased rice plants, some insects moved
3 rice plants in the cages; others either
loved to other places in the cage or did
ot move. Within 2 hours after the insects

were introduced into the cage, 40 to 60
percent of the insects moved to plants.
While the percentage increased with time,
it rarely reached 100 (Table 1).

Among the insects which moved to the
plants in the cage, some moved to the
healthy plants and others to the diseased
plants. The portion of the insects that
moved to the healthy and diseased plants
varied under different light conditions.
When the tests were made in the daytime
or from the afternoon to the following
morning, the insects appeared to prefer to
move to the diseased plants because
significantly more insects were consistent-
ly found on diseased plants than were
found on healthy plants regardless of the
length of testing time. However, this
differences became smaller as the testing
time lengthened.

When the tests were conducted in
darkness (the cages were covered with a

Table 1. Effect of test conditions on the
and tungro-diseased TaichungNai

Light Duration Trials Inse
(hr) (no.) (n,

Daylight 2 8 3
Daylight 8 12 4
Daylight and dark2/ 16 12 4
Dark 2 11 4
Dark 16 4 1
Green 2 8 2
Yellow 2 8 2

1/The rest of the insects were in the cage bi
2/From 1600 to 0800 hours the following
= significant; ns = not significant.

black cloth in the daytime), the number
of insects on diseased and healthy plants
was almost the same regardless of the
length of the testing time (Table 1). The
main reason why different results were
obtained under conditions of light and
darkness may have been that the insects
were attracted to the yellow color of the
diseased plants, but were unable to dis-
tinguish between the yellow diseased
plants and the healthy green plants in the

When the cages were covered with
green cellophane, there were 8 percent
more insects on the diseased plants than
on the healthy plants, indicating that
more insects moved to the diseased
plants. When the cages were covered with
yellow cellophane, there were 14 percent
more insects on the healthy plants than
on the diseased plants. Hence, N. vires-
cens adults appeared to exhibit a sensiti-
vity to the colors of green and yellow.

wvement of Nephotettix virescens to health)
1 rice plants in cages.

X2 test
Insects Insects (%) on
on Homo.
s plants1/ Healthy Diseased 1.1 genityo
(0/() plants plants ratio trials

!8 60 38 62 ** **
3 98 41 59 ** **
4 96 42 58 ns **
5 49 52 48 ns **
4 92 50 50 ns ns
'8 43 46 54 ** ns
:7 39 57 43 ** **

not on plants.

The sensitivity of insects to light of
different wavelengths may not be iden-
tical. Sasamoto, Kobayashi, and Shiraishi
(1968) demonstrated a difference in the
attraction of N. cincticeps to 13 lamps of
different wavelengths ranging from 300
to 700 nm. Koyama (1973) reported that
Inazuma dorsalis was attracted more to a
diet of 5% sucrose solution colored with a
yellow light than to the same diet colored
with green light.
Variation in the results among the
trials of most of the tests (Table 1) sug-
gested that some factors, such as light
intensity, were not properly controlled.
Nevertheless, the results indicated that
caged insects can move to the diseased
plants and thus can carry out the initial
step of tungro virus transmission in a
Acquisition of tungro virus by insects.
The percentage of infective insects
varied among the different proportions of

diseased and healthy plants in a cage,
with the percentage increasing as the ratio
of diseased plants to healthy plants in-
creased (Table 2). Based on the percen-
tage of infective insects, it appeared that
either because of an uneven distribution
of the insects on diseased and healthy
plants or because of a sampling error,
more insects could have been on the
diseased plants when the confinement
period was 1, 7, or 14 days. In contrast,
more insects could have been on the
healthy plants when the confinement
period was 2 or 4 days. Consequently, the
percentage of infective insects did not
increase linearly as the confinement per-
iod increased from 1 to 4 days except
when the cage contained no healthy
plants. The percentage of infective insects
gradually increases with an increasing
length of acquisition access time (Federa-
tion of British Plant Pathologists, 1973)
from 2 hours to 4 days, after which it
decreases slightly (Ling. 1966).

Table 2. Percentage of infective insects of Nephotettix virescens I to 14 days after being
introduced into a cage with different proportions of healthy and tungro-diseased
rice plants.

Pots in cage (no.)
Infective Insects1/

Healthy Diseased
plants plants 1 day 2 days 4 days 7 days 14 days Av.

3 1 21 18 16 26 40 24
2 2 36 33 39 58 60 45
1 3 56 39 44 51 51 48
0 4 63 70 75 68 71 69

Average 44 40 44 51 56 47

i/Average of two trials with a

total of 3,161 insects.

13 to 324 1080 1 82.9 7.6 8.7
i8 to 342 1256 2 54.7 27.5 17.4
23 to 395 1406 3 31.5 38.1 29.9

Four trials.
The sum is not 100 percent because some insects were not on plants.


Not all the insects that moved from
either the healthy or the diseased plants
reached another plant (Table 3). About
6.0 percent of the test insects were not
on the plants at the time they were
counted, while the remainder were either
on their original host plants or on other
plants. Whether the insects were on
healthy or on diseased plants, more
moved to the healthy plants; among the
insects on healthy plants, 26 percent
moved to healthy plants and 18 percent
moved to diseased plants, and the respec-
tive values for movement of insects from
diseased plants were 24 and 19 percent.
These findings differ from those obtained
when the insects were moving to diseased
plants (Table 1) and this may be due to
the difference in the place from where the
insects started their move. The greater
number of insects moving to healthy
plants might help explain the low percent-
age of infective insects when the insects
were confined in cages with various
proportions of healthy and diseased plants
for 2 or 4 days (Table 2).
The fact that the insects moved from
diseased to healthy plants illustrates that
the tungro virus could be spread by
insects in cages.
Viruliferous insects and seedling infec-
tion. When the various numbers of
viruliferous insects were introduced into
cages containing seedlings for different
numbers of days, 35 percent of a total of
31,274 test seedlings became infected.
This excluded the seedlings that died
before the symptoms developed.

The percentage of infected seedlings
increased gradually with an increasing
number of viruliferous insects in the cage
or number of viruliferous insects per
seedling regardless of the duration of
their confinement (Fig. 2). About 19, 31,
and 66 percent of the seedlings became
infected when 50, 100, and 400 virulife-
rous insects were put in a cage 0.125,
0.25, and 1.0 viruliferous insect/seedling,

The percentage of infected seedlings
per insect was affected by the density of
the insect population. The rate for the
first 50 viruliferous insects was 0.38
percent infected seedlings/insect, for the
second 50 insects, 0.12 percent/insect,
and for 101 to 400 insects, 012. percent/
insect. The rate decreased gradually with
an increasing number of viruliferous in-
sects in the cage or the number of insects
per seedling. Thus, it appears possible to
study the population effect of virulife-
rous N. virescens on the incidence of
tungro disease by the cage method.

The percentage of infected seedlings
increased with an increased length of
confinement of the viruliferous insects in
the cage (Fig. 2) with the averages of
infected seedlings being 28, 39, and 48
percent for 1, 4, and 7 days of confine-
ment, respectively. The average rates of
infected seedlings with prolonged dura-
tion of confinement of the insects in the
cage were similar except when the dura-
tion was lengthened from 0 to 1 day. The
rate from zero to the first day was 2.8
percent/day, from the second to the
fourth day, 3.4 percent/day, and from
the fifth to the seventh day, 3.2 percent/
day, illustrating the effect of the duration
of confinement of viruliferous insects on
the percentage of infected seedlings, as
tested by the cage method.

Both the number of viruliferous in-
sects and the duration of confinement of
the insects affected the incidence of the
tungro disease, although the magnitude of
the effects of those two variables differed.
It is difficult to conclude which of these
two factors is more important in increas-
ing the percentage of infected seedlings.
The increase in the percentage of the
infected seedlings brought about by pro-
longing the duration of confinement for 1
day was mathematically equivalent to
that of increasing the number of virulife-
rous insects in a cage by 25.5 or by
increasing the ratio of viruliferous insects
per seedling to 0.06 insect/seedling.


Vr ~rC CY)I YY-



80- /60


60- V

40 -/ 32 ,


O1 13
0 I 2
Distance (no. of pot,

3. Percentage of tungro-infected rice
from where viruliferous Nephotet
113.607 TNI seedlings

nt of release.
While the alignment of the cage to the
action of sunlight at time of introduc-
ri of the viruliferous insects into the
e did not affect the percentage of
scted seedlings to any major extent, it
affect the distribution of the infected
clings per pot in the cage, probably





21 0


lings of each pot at different distances
virescens were introduced and caged

the insects to a vi

evenly distributed throughout the cage effect of amount of virus source oi
when the insects were released at the side incidence of the disease, then the 1
of the cage facing the sun than when they mum amount cannot be less than one
were released at the opposite side of the or less than one-sixteenth of the po
cage (Fig. 4). tion, there being a total of 16 pots
cage. Furthermore, because the siz
Limitation of the cage method. The the cage is fixed, the distance bet,
major limitation of the cage method is seedlings determines the number of
the size of the cage although the cage can lings that can be accommodated ir
be tailored to the specifications of the cage. It is not possible to have the
investigator. However, the larger the size number of seedlings at different dists
of the cage, the bigger will be the space between two seedlings in the cage u
needed to accommodate the cage, and the the required space is smaller than the
greater the amount of materials that will of the cage.
be required for each test.
The cage method fundamentally
Due to the limitation of the size of the not duplicate all conditions occu
cage, the distance of dispersal of the naturally in the field. However, it pei
viruliferous insects would reflect the dis- some factors, such as insect vector,
tance of spread of the disease under source, rice variety, and others, t,
natural conditions but it cannot be deter- quantitatively or qualitatively varied
mined by the cage method unless the size studying their effect on the incident
of the cage is larger than the distance that the tungro disease.

86 60 46 31 82 52 33 22

57 45 29 20 52 37 29 23

38 27 5 6 30 29 24 25

21 9 8 10 29 17 17 22

TION OF BRITISH PLANT PATHOLOGISTS. 1973. A guide to the use of
ms in plant pathology. Phytopath. pap. no. 17, 55 p.
A, K. 1973. Preference on color of the diets in Inazuma.dorsalis (Hemiptera:
Itocephalidae) (in Japanese, English summary). Jap. J. Appl. Entomol. Zool.

1. C. 1966. Nonpersistence of the tungro virus of rice in its leafhopper vector,
photettix impicticeps. Phytopathology 56: 1252-1256.

1972. Rice virus diseases. International Rice Research Institute, Los Bafios,
ilippines. 142 p.
IITA, K., Y. ITO, S. YASUO, A. YAMAGUCHI, and M. ISHI. 1964. Studies of
Sdispersal of plant and leafhoppers. II. Dispersal of Delphacodes striatella Fallen,
photettix cincticeps Uhler, and Deltocephalus dorsalis Motschulsky in nursery
I paddy field. Jap. J. Ecol. 14:233-241.
)TO, K., M. KOBAYASHI, and M. SHIRAISHI. 1968. Insect control by light
p 1. Attracting effectiveness of various lamps of different wave lengths against
green rice leafhopper, Nephotettix cincticeps Uhler (Hemiptera: Jassidae) (in
panese, English summary). Jap. J. Appl. Entomol. Zool. 12:164-170.1


The International Rice I

The writer is grateful to V. M. A4
N. A. Pefiamora, C. T. Rivera, F. F. Sal:
ring insects and to M. P. Carbonell for hi!

A term "infective capacity" is pri
infective insect can infect in 1 day or
Nephotettix virescens in transmitting
viruliferous adults individually and conse
10 hours.
The insect transmitted the tungro
of 5 minutes. However, as the inoculatid
seedlings increased but the number of see
decreased. The maximum infective capacity
It is suspected that a more capable ins

Studies on the transmission of r
viruses by insect vectors generally emp]
size the species of insect vectors and 1
virus-vector interaction. Studies on 1
virus-vector interaction include del
mination of the percentage of act
transmitters; the length of the period
acquisition feeding, incubation, inocm
tion feeding, and retention; and 1
occurrence of transstadial and tra
ovarial passages (see Ling, 1972 a
Federation of British Plant Pathologii
1973 for definitions of these terms).
compare two species of insect vectors:
their ability to transmit a virus dises
Ling (1970) used "number of disea
transmitting days" the number ofd
within a given length of time dur
which an infective insect actually tr
smits the disease. None of these stud
emphasizes the quantitative aspect of
infective insect to infect seedlings.
The epidemiology of plant diseases 1
recently received attention. The spread
a rice virus disease that is transmitted
an insect vector is part of the epidefr
logy of the disease. One of the fun
mental questions regarding the spread


arch Institute, Los Bafios, Laguna

ro, M. P. Carbonell, E. M. Juinio, M. E. Mundin,
, and A. V. Villegas for their assistance in transfer-
ip in taking readings of infected seedlings.

sed for the number of seedlings or plants that an
I given period of time. The infective capacity of
! tungro virus was determined by transferring
ively to rice seedlings at various time intervals for

; to rice seedlings within an inoculation access time
access time lengthened, the percentage of infected
gs inoculated by an insect in a given period of time
>tained was about 30 infected seedlings/insect/day.
may infect more seedlings under more favorable

the disease is how many rice seedlings
plants can an infective insect infect ix
day a quantitative aspect of the ca]
city of an infective insect to infi
To elucidate the quantitative aspect
an insect to infect seedlings, a te!
"infective capacity" is proposed here 1
the number of seedlings or plants that
infective insect can infect in 1 day or ii
given period of time. The infective ca]
city of an insect in a day is apparent
related to the length of the inoculati
access time that refers to the length
time a vector is allowed to spend on a t
host in transmission experiments (Fede
tion of British Plant Pathologists, 197
It is also associated with the number
disease-transmitting days, as mention
above. To determine the number
disease-transmitting days of an insect, 1
insect is allowed to inoculate only (
seedling in 1 day, and thus, it cannot h1
more than one infected seedling in 1 d
This differs from the infective capacity
an insect that is determined by allow
an insect to inoculate as many seedli
as possible but with the objective

obtaining the largest number of infected
seedlings in 1 day or in a given period of
time. Theoretically, the infective capacity
of an insect in 1 day can be calculated by
dividing 24 hours by the number of hours
used for each inoculation access time of
positive transmission. However, the insect
may not infect a seedling during each
inoculation access time in a day. Conse-
quently, infective capacity of an insect
would be less than, or at the most equal
to, the calculated number.
The infective capacity of an insect in 1
day is the product of the percentage of
infected seedlings multiplied by the
number of seedlings visited by an infec-
tive insect in 1 day in the field, or
multiplied by the number of seedlings
exposed to an infective insect in 1 day in
the laboratory. Both the duration of an
infective insect's visit on a seedling in the
field and the length of time a seedling is
exposed to an infective insect in the
laboratory are equivalent to the inocula-
tion access time of the insect on the
seedling as far as the transmission of the
virus is concerned. The length of the
inoculation access time affects the per-
centage of infected seedlings. Generally,
before the maximum percentage of
infected seedlings is reached, the longer
the inoculation access time is, the higher
is the percentage of infected seedlings. On
the contrary, the longer the inoculation
access time, the lower is the possible
number of seedlings that can be ino-
culated by an infective insect in a unit of
time. Consequently, the infective capa-
city of an insect is determined by both
the percentage of infected seedlings and
the number of seedlings inoculated by the
insect in a given period of time.
This paper reports on the infective
capacity of Nephotettix virescens (Dis-
tant) in transmitting the rice tungro virus.

The colony ofN. virescens used in this
study was reared on rice plants of variety

Taichung Native I (TNI) in screen cages
under Los Bafios, Philippines conditions.
To make the insects viruliferous, they
were confined on tungro-diseased plants
of TNI for 3 to 4 days prior to the test.
TNI seedlings (1-week old) were
placed individually in 18 x 150 mm test
tubes. A viruliferous insect was transfer-
red into each tube with an aspirator.
Immediately after the transfer, the tubes
were covered with polypropylene culture
tube caps to prevent the insects from
escaping. The insects were then transfer-
red successively to new seedlings at inter-
vals of 5, 10, 15, 30, and 60 minutes
from 0800 to 1800 hours. The insects
were released at the end of the test and
the seedlings were transplanted into pots
and kept in the greenhouse to allow the
symptoms of the disease to develop. Ten
insects were used for each treatment. The
test was carried out four times from
August to October, 1973. Thus, a total of
10,000 seedlings were exposed to 200
viruliferous adults ofN. virescens, exclud-
ing the insects used for replacements.
Since some insects either died before
the test ended or did not infect any
seedlings, only the data from those
infective insects that lasted throughout
the entire period of testing were used in
calculating the infective capacity of the
N. virescens. All insects were included in
the calculations pertaining to the infected
seedlings from the 5-minute transfer
intervals. The percentages of infected
seedlings were calculated according to the
total number of surviving seedlings be-
cause some seedlings died before the
disease symptoms developed.


Percentage of infected seedlings. Of
the 200 tested insects, only 118 were
infective and the number of infective
insects per treatment varied from 17 to
31 (Table 1). Because the length of
transfer intervals differed, the number of
seedlings exposed to each infective insect

period. Nevertheless, the number of seed-
lings exposed to each infective insect was
the quotient of 600 minutes divided by
the length of transfer interval in minutes.
Of a total of 5,350 seedlings exposed to
the infective insects, 5,114 seedlings
survived after the disease symptoms
developed. Among the treatments be-
tween 3.5 and 7.1 percent of the seed-
lings died, with an average of 4.4 percent.
Only 460 of the surviving seedlings, con-
sisting of 47 to 118 seedlings per treat-
ment, became infected; overall, 9.0 per-
cent of the seedlings in the test were
The percentage of infected seedling
varied among individual insects regardless,
of the length of the transfer intervals
However, the minimum, average, anc
maximum percentages of infected seed.
lings increased as the transfer interval was
lengthened from 5 to 60 minutes (Table
1). The difference between the maxi
mum and the minimum percentage
varied from 4.5 to 80.0 percent among
treatments, and this difference increase
as the transfer interval was lengthened.

Table 1. Percentages of seedlings infect
serially transferred at different ti


rj~' kjUf .%UOwkfUf 0V l11 1-
ed working hours in a day, the infective
insects were transferred only for a period
of 10 hours. Although the tungro virus
does not persist in N. virescens and the
infectivity of the insect gradually
decreases with time after an acquisition
feeding (Ling, 1966), the infective capa-
city of the insect in 1 day can be
calculated on the basis of the obtained
percentage of infected seedlings as-
suming that the infectivity of the insects
in the first 10-hour period remains un-
changed for the remainder of the day.
The minimum infective capacity varied
from 2.4 to 2.6 infected seedlings/infec-
tive insect/day among treatments (Fig.
1). The theoretical minimum should be
2.4 regardless of the length of transfer
intervals because the insect should infect
at least one seedling in the 10-hour
period; otherwise, the insect is not infeo-
tive. The mortality of the seedlings and
the error from mathematical rounding
off caused the slight deviation from the
theoretical minimum.
On the average, each infective insect
infected 5.8 seedlings/day at a transfer

interval of 5 minutes, 10.5 at 10
minutes, 11.3 at 15 minutes, 11.6 at 30
minutes, and 9.7 at 60 minutes. Conse-
quently, except when the transfer inter-
val was 5 minutes, an infective insect in
this test could infect only 10 to 12
seedlings on the average with the tungro
virus in 1 day.
The maximum infective capacity of
the insect was 15.6, 27.4, 30.1, 30.0,
and 21.6 infected seedlings/infective
insect/day for the respective transfer
intervals of 5, 10, 15, 30, and 60
minutes. Apparently, one infective insect
of the present test sample could only
infect, at the most, about 30 seedlings
with tungro in 1 day. Additionally, the
transfer interval of 30 minutes gave the
largest number of infected seedlings but
the number was only numerically higher
than that from the transfer interval of 15
minutes. The transfer intervals of 5 and
60 minutes resulted in less infected

Infected seedlings ( no.* insect-I day-

30 Maximum



0 I I I I
0 30 60
Transfer inter

seedlings than when the transfer interval
was 30 minutes. However, the number of
infected seedlings per infective insect per
day for the 10-minute transfer time was
about 10 percent lower than that for the
30minute transfer period.
Prolonging the transfer interval would
have increased the percentage of infected
seedlings but would have also reduced
the number of seedlings that can be
inoculated by an insect in 1 day. Even
assuming 100 percent infection, when
the transfer interval is 61 to 66 minutes,
the calculated number of infected seed-
lings per infective insect per day is
slightly greater than that obtained from
the transfer interval of 60 minutes in this
study. When the transfer interval is 67
minutes or longer, the calculated number
of infected seedlings per day is not only
smaller than that obtained from the
transfer interval of 60 minutes but also
decreases gradually as the time between

90 120 150
val (minutes)

Fig. 1. Calculated number of TNI seedlings infected with tungro by an infective
Nephotettix virescens during different transfer intervals in a 24-hour day
assuming that the infectivity of the insect during the first 10-hour period
remains constant for the rest of the day.

transfers increases because
reduced number of seedlings tl
inoculated by an infective insec
(ig 1).

Hourly seedling infection. -
insects did not infect seedling
transfer interval nor did th
seedlings at the same rate du
hour of the test period. There
50, 54, 41, 32, 32, 17, 21, 1
percent infective insects and 1:
12, 9, 8, 5, 6, 4, and 3 percent
seedlings, respectively, at hou
vals from the first to the tent
the test period. Hence, both th
.... I__1 .- -


*ansIer nterval

ired foi

t- t

t to the third hour; they decreased lings decreases as the inoculation access
dually thereafter time becomes shorter. If the inoculated
The number of seedlings infected in 1 seedlings do not become infected, there
ur depended on the number of seed- would be no other direct evidence of
gs exposed to an infective insect and positive transmission. In this study, of a
i capacity of the insect to infect the total of 4,800 seedlings that were
dlings. For instance, with a 60-minute exposed to 71 viruliferous insects for the
nsfer interval, only one seedling could inoculation access time of 5 minutes,

interval of 10 minutes. The frequency
distribution of infected seedlings accord-
ing to the number of infected seedlings
in 1 hour revealed that 81, 15, 3, and 1
percent of the total infected seedlings
were infected by an infected insect at a
rate of 1, 2, 3, and 4 seedlings/hour,
respectively. Hence, most of the infec-
tive insects infected only one seedling in
1 hour regardless of the number of
seedlings to which they had access in 1
The pattern by which N. virescens
transmits the tungro virus depends upon
the time interval between transfers. If
the interval is 1 hour, the pattern is
intermittent. If it is I day, the pattern is
consecutive except in a few cases (Ling.
1969). In this study the transmission
pattern was intermittent not only when
the transfer interval was 60 minutes, but
also when it was 5, 10, 15 or 30 minutes.

became nmectea Trom 41 intective
insects, giving 2.1 percent infected seed-
lings for a total of 71 viruliferous insects
and 3.1 percent of the 41 infective
insects since 1,493 seedlings were
exposed to 30 noninfective insects. The
number of seedlings infected by the
infective insects ranged between one and
seven seedlings, with an average of 2.3
seedlings/infective insect (Table 2).

Tungro-infective N. virescens infected
different numbers of rice seedlings in a
given period of time. Therefore, the
percentage of infected seedlings varied
not only among individual insects but
also among different durations of the
transfer intervals. However, the percent-
age of infected seedlings, regardless of
the minimum, average, or maximum,
increased gradually as the interval be-
tween two transfp.r in~ari.a. frrnm < tn

e ror

nt to

13TITIn riant FAMAnnlitte ILJI-4 h,--


Infected Insects Seedlings Infected
seedlings exposed to seedlings
(no./insect) (no.) insects (no.) (no.)

0 30 1493 0
1 16 1264 16
2 12 942 24
3 5 369 15
4 4 234 16
5 1 83 5
6 2 179 12
7 1 39 7
Total 71 4603 95

60 minutes. The transfer interval in this transfer interval (or the inoculation
study is practically equivalent to the access time) of 30 minutes. Since the
inoculation access time, also known as transfer intervals of a few minutes
the inoculation feding period (Ling, shorter and a few minutes longer than 30
1972). The effect of inoculation access minutes were not included in this study,
time on seedling infection has been and no appreciable difference between
known. For instance, the percentage of intervals of 30 and 15 minutes was
infected seedlings increases gradually as found, the real maximum infective capa-
inoculation access time lengthens from 1 city of N. virescens might be resulted
to 9 hours (IRRI, 1973). This effect from a transfer interval of between 15and
seems to illustrate that the ability of N. 30 minutes.
virescens to infect rice seedlings with Extrapolation of the estimated infec-
tungro is limited by the length of time tive capacity of an insect based on a test
an infective insect is exposed to rice period shorter than aday(24hours)to a
plants. 24-hour day is biologically inaccurate
The longer the inoculation access even assuming that the infectivity of the
time of an infective insect, the higher is insect for the test period remains con-
the percentage of infected seedlings, but stant for the rest of the day. To project
the lower is thelpossible number of seed- the infective capacity by extrapolating
lings that can be inoculated by an the results obtained in a short testing
infective insect in a given unit of time. period (i.e., extrapolation of results from
The infective capacity of an insect is a one hour test period to 24 hours) is
determined, by both the percentage of always overestimated. For instance, the
infected seedlings and the number of minimum infective capacity of an insect
inoculated seedlings. Therefore, neither should theoretically be 1 infected seed
the shortest inoculation access time that ling/infective insect regardless of the length
gives the largest number of inoculated of the test period, inasmuch as zero infect-

IJULC. Af jurM rrU4dM4 4- j XT-_I.-4i~rapj.A~ *jif- ff* ntf jjijff/ytf-ini

fective capacity projected from the re-
ilts obtained in this study was 2.4 infect-
i seedling/infective insect/day (10 hours
st period extrapolated to 24 hours: 1
er 10 hours = 2.4 per 25 hours) that is
At only overestimated but also theoreti-
Uy incorrect. On the other hand, the
sumption that the infectivity ot the
sect for the test period remains un-
ianged for the rest of the day is
ntradictory to the fact that infectivity
tungro-viruliferous N. virescens
creases gradually with increases in
me after acquisition feeding (Ling,
)66). Hence, the infective capacity
calculated based on this assumption is
- A- U4- All., rro; 9~ nrp

re, a new recuru iui uiL aiiULLva
oculation access time of tungro-infective
virescens for positive transmission.

Based on the shortest inoculation
cess time of 5 minutes for positive
insmission, the theoretical maximum
Fective capacity of N. virescens could
288 (24 hours x 60 minutes/5
nutes) infected seedlings/infective
sect/day. The tungro virus does not
rsist in N. virescens and, in general,
)re than 50 percent of the insects
come noninfective in the following
y (Ling, 1966) Assuming that the 50
recent represents also the rate of reduc-
in of the infectivity of the insect, the
R infp~tp~+d cPllina/infP4tivU inert/

The maximum infective capacity of UUCM "ut "I4V 41 UIpp'LLUIULy
- -- o nirpl +tha thlnorn ilnl Thle than

>pmnes was / minutes as reported by study is much lower than the theoretical
(1968). He stated that "7 minutes maximum.
lot necessarily the minimum dura-
of positive transmission but it was The maximum infective capacity of

another every 30 minutes. Ling and
Carbonell (1975) noted that, at the
most, four seedlings were infected by
one infective insect confined in a cage
with rice seedlings for 9 hours, denoting
that the infective insect can infect only
11 seedlings in 1 day or 21 seedlings for
the rest of its life without reacquiring
the tungro virus. The difference between
61 and 21 or between 30 and 11
illustrates that the infective capacity of
N. virescens obtained from artificial
transfers is much greater than that
obtained under conditions where the
insect is not forced to move from a


seedling to another.
The present data reveal that:there is a
limitation of the ability of N. virescens
to infect rice seedlings with tungro.
Since tungro-infective adults ofN. vires-
cens differed in their ability to infect
rice seedlings, it is possible that the
infective capacity of the insect may vary
among samples of insects as well as
among different test conditions. Hence,
an insect with a greater infective capa-
city and under more favorable condi-
tions may infect a moderately larger
number of seedlings than that obtained
in this study.

r fT i'rT1

LING, K. C. 1966. Nonpersistence of the tungro virus of rice in its leafhopper vector,
Nephotettix impicticeps. Phytopathology 56:1252-1256.

1968. Mechanism of tungro-resistance in rice variety Pankhari 203. Phil.
Phytopathol. 01. 4:21-38.

S1969. Nonpropagative leafhopper-borne viruses, p. 255-277. In K. Marai
(ed.), Virues, vectors, and vegetation. Interscience Publishers, New York.

1970. Ability of Nephottix apicalis to transmit the rice tungro virus. J. ]
Entomol, 63:582-586.

1972. Rice virus diseases. International Rice Research Institute, Los Bafios, I
pines. 142 p

and M. P. CARBONELL. 1975. Movement of individual viruliferousNephe
virescens in cages and tungro infection of rice seedlings. Phil. Phytopathol. (In Press


Former Undergraduate Student and Assistant Professor, respectively, Department of
Plant Pathology, U.P.C.A.

A portion of an undergraduate thesis submitted by the senior author to the U.P.C.A.
This study was supported by UP-NSDB Cooperative Research Project No. 74-CHS-A.3.6.1

In simultaneous pot experiments, inoculations with field populations of the reniform
nematode, Rotylenchulus reniformis, at approximately 20,000 larvae per plant, resulted in
yield reductions of 41.5% 21.3% and 27.7% in mung bean, soybean and peanut, respectively.
In mung bean, the reduction was statistically significant at P =0.05; yield reductions in soy-
bean and peanut were significant only at P 0.10. Weights of tops and toots of mung bean were
also reduced by 30.5% (significant at P =0.10) and 48.9% (significant at P =0.01) respectively.
Reductions in weights of tops and roots of soybean and peanut were not significant. Other than
these gross effects, no other symptoms of nematode damage, including root necrosis, were
apparent on inoculated plants.

-hulus reniformis, has been recognized as
me of the most commonly associated
>lant parasitic nematodes with roots of
najor agricultural crops in the Tropics
ad warmer parts of the Temperate Zone.
t is widely distributed in India (Dasgupta
ad Seshadri, 1971), and also in Puerto
tico, Africa, Hawaii, and some parts of
outhem United States (Ayala and Rami-
ez, 1964). Ayala and Ramirez (1964)
isted 201 host plants of Rotylenchulus
pp. from 15 different countries. In the
'hilippines, Valdez (1968) observed that
:offee seedlings inoculated with R. reni-
ormis larvae developed stubby roots.
Soybean and peanut were among the
losts of R. reniformis in the Gold Coast,
Africa (Peacock, 1956) and in Louisiana,
J.S.A. (Birchfield and Brister 1962).
rimm (1965) reported the association of
lotylenchulus spp. with soybean in Los
Bafios, Laguna. At the UPCA Central
Experiment Station, the abundance of
hese nematodes in soils and roots of
nung bean and soybean and their less

sanut were also reported (Castillo,
971). In a subsequent preliminary in-
estigation that we conducted, however,
er plant inoculation with approximately
,000 larvae of these Rotylenchulus spp.
tiled to cause pathologic reactions of the
ops. A recent survey (Castillo, 1974)
inducted in 26 provinces situated in as
tr north as Abra down to Cotabato
svealed that Rotylenchulus spp. were the
lost frequently occurring plant parasitic
ematodes in soils of stunted mung bean,
)ybean and peanut. Based on the
umber of provinces, municipalities and
impling areas where they were collected,
iese nematodes were also found to be
ie most prevalent on mung bean and
)ybean, and second only to Helicoty-
'nchus spp. on peanut. Gravid females in
ceding positions on roots of the three
rops were commonly observed.
This study was conducted to ascertain
ie involvement of R. reniformis in
diseases of mung bean, soybean and

Soil samples from soybean fields, heav-
ily infested with nematodes of the genus
Rotylenchulus were collected from the
UPCA Central Experiment Station. The
nematodes were extracted from the soil
using the combination of sieving and
Baermann funnel methods described by
Christie and Perry (1951). Following
extraction, nematode samples in the
larval forms were randomly picked from
different suspensions and incubated in
water for 18 days. Based on measure-
ments of the morphological characters
used by Dasgupta, Raski and Sher (1968)
of 20 juvenile females and following the
keys of Loof and Oostenbrink (1962) and
Hussain and Khan (1965), the nematode
isolate was identified asR. reniformis.

Mung bean (MG 50-10AI soybean
(I1- 14) and peanut (CES 101) were used
as test plants in the pot experiments.
Seeds were sown in seed-boxes containing
baked soil. Seven days after sowing, the
seedlings were transplanted singly to 15-
cm clay pots. Five days later, they were

inoculated seedlings were provided as
checks. The experimental plants of each
crop were separated from those of the
others and randomly arranged on top of a
wooden bench placed outdoors. The re-
actions of the test plants to nematode
inoculations were evaluated, based on the
following: degree of root necrosis, root
and top weights and yield. These data
were obtained 60, 85 and 110 days after
transplanting of mung bean, soybean and
peanut, respectively.
Table 1 shows the effects of nematode
inoculations on root and top weights and
yields of the test plants. Yield reductions
of 41.5% 21.3% and 27.7% in mung bean,
soybean and peanut, respectively, were
noted. In mung bean, the yield reduction
was statistically significant at P = .05; in
soybean and peanut it was significant
only at P =. 10. Root and top weights of'
mung bean were also reduced by 30.5%
(significant at P = .10) and 48.9% signifyf
icant at P =.01), respectively. Reduction:

imately 20,000 R. reniformis larvae Figures 1 and 2 show the top growths
extracted from field soils. Other nema- and root systems of uninoculated and
todes contained in the suspensions were inoculated mung bean and soybean,
removed by handpicking prior to inocula- respectively. Figure 3 shows the root
tion. Six seedlings of each crop were systems and pods of uninoculated and
inoculated. Similar number of un- inoculated peanut.

fects of inoculations with approximately 20,000 larvae of R. reniformis per
ant on mung bean, soybean and peanut.a

Root weight (g) Top weight (g) Yield (g)
Control Inoc. Per cent Control Inoc. Per cent Control Inoc.
reduction reduction

4.5 2.3*** 48.9 14.1 9.8* 30.5 6.5 3.8***
16.1 13.6 15.5 22.6 18.0 20.5 22.5 17.7*
17.0 15.8 7.0 48.5 38.5 20.8 17.3 12.5*

means of six replicates.
- Sinnificantlv different from the control at P =0.10, P =0.05 and P =0.01, respectively.



Fig 2. Top growths and root system
inoculated with 20,000 larvae


of soybean. A and C, control; B and D,

Our experiment has shown that the formation on the nematode's g
reniform nematode, R. reniformis, was graphical distribution and prevalence,
involved in a disease of mung bean, important in determining the econor
soybean and peanut. There is only very importance of the nematode on
little doubt that the nematode was the crops.



.YALA, A. and C. T. RAMIREZ. 1964. Hc
reniform nematode, Rotylenchulus r
Rico. J. Agric. Univ. Puerto Rico 48: 1

nematodes. Plant Dis. Reptr. 46: 683-C

ASTILLO, M. B. 1971. Reniform nematode
peanut soils at the UPCA Central E)

1974. Survey of plant
soybean and peanut in the Philippines.
Research Project No. 74-CHS-A.3.6.1.

HRISTIE, J. and V. G. PERRY. 195
Helminthol. Soc, Wash. 18: 106-108.

ASGUPTA, D. R., D. J. RASKI and S.
Rotylenchulus Linford, and Oliveir
Helminthol. Soc. Wash. 35: 169-192.

Rotylenchulus reniformis Linford and

USSAIN, S. I. and A. M. KHAN. 1965. On
the species of the genus (Nematoda: T

OOF, P. A. and M. OOSTENBRINK. 1962
the species of Rotylenchulus Nematolo

EACOCK, F. C. 1956. The reniform nem

[MM, R. W. 1965. A preliminary survey c
and the Philippines. Bangkok: South-I

ALDEZ, R. B. 1968. Stubby roots of
reniformis. Phil. Agric. 51: 672-679.


inge, distribution and bibliography of the
)rmis, with special reference to Puerto

. New hosts and non-hosts of reniform

itylenchulus, sp., in mungo, soybean and
ment Station. Phil. Phytopathology. 7:

sitic nematodes associated with stunted
i. Report, UP-NSDB Cooperative

removing nematodes from soil. Proc.

SHER. 1968. A revision of the genus
940 (Nematoda: (Tylenchidae). Proc.

971. Races of the reniform nematode,
reira, 1950. Indian J. Nematol. 1: 7-20.

ylenchulus stakmani n. sp. with a key to
chida). Proc. Helminthol. Soc. Wash. 32:

tylenchulus borealis n. sp., with a key to
7: 83-90.

le in the Gold Coast. Nematological 1:

e plant parasitic nematodes of Thailand
Asia Treaty Org. Secretariat General. '7

'ee seedlings caused by Rotylenchulus


Assistant Professor and Research. Assists
College of Agriculture, U.P. at Los Bafios, Coll
This study was supported by UP-NSDB C
The assistance of N. B. Bajet, R. C. M
during the survey phase of the study is hig
V. C. Bicomong for typing the manuscript.


Survey conducted in 25 provinces
Tortylenchulus, Meloidogyne, Helicotylencht
Pratylenchus, Ditylenchus, Criconemoides, a
Hemicycliophora, which was replaced by Scs
were associated with cassava. Feeding and
Meloidogyne and Rotylenchulus, but galling
damage. Rbtylenchulus, Helicotylenchus, an
most prevalent and most frequently occurring
in a few sampling areas, the population den
In pot experiments, per plant inoculal
with 50 and. 100 egg masses ofM. arenaria re
weights of sweet potato and significantly hi
Inoculations of cassava with up to 175 egg r
200 egg masses ofM. incognita acrita did not
containing egg masses formed on roots.

Sweet potato and cassava are perhal
the most important and productive ro
crops in the world. Production, however
is believed to be limited by pests ai
diseases. In the United States, Mart
(1967) reported several species of pla
parasitic nematodes commonly associate
with sweet potato roots. Among their
the root-knot nematodes, Meloidogyj
incognita, MA hapla, andM. javanica, cau
distinct damage to the crop. Several oth
workers (Krusberg and Nielsen, 195
Nielsen and Sasser, 1959; Elmer, 195
reported the incidence of root knot c
sweet potato. The reniform, sting, bi
rowing, and stem and bulb nematode
are also believed to cause appreciable <
mage on sweet potato (Martin, 196'
The association of Meloidogyne sp. w
cassava was also reported (Anonymol


respectively, Department of Plant Pathology,
, Laguna.
perative Project No. 2.275-28 B.
;alig and B. B. Alvaran and S. P. Milagrosa,
appreciated. Acknowledgement is also due


the Philippines revealed the association of
Hoplolaimus, Tylenchorhynchus, Aphelenchus,
Hemicycliophora, with sweet potato. Except
lonema and Aphelenchoides, these same genera
reduction on both crops were manifested by
ue to the former was the only apparent root
feloidogyne were the most widely distributed,
ant parasitic nematodes on both crops. Except
es of plant parasitic nematodes were generally
is with about 7,000 larvae of R. renfformis and
Led in significantly higher (P .01) root and top
-r (P = .05) top weight of cassava, respectively.
ies of M. arenaria and sweet potato with up to
se significant growth reductions, although galls

In the Philippines, the lists of pla
parasitic nematodes found associated wil
sweet potato and cassava were alreai
compiled (Castillo et al. 1974). Th
geographical distribution, prevalence ai
economic importance of these nematode
however, have not yet been ascertain


I. Survey

A survey to determine the plant par
sitic nematodes associated with swe,
potato and cassava in the Philippines w
conducted in February, 1973 to Januar
1974 in 25 provinces, viz., Albay, Bataa
Batangas, Benguet, Cagayan, Camarin

Norte, Camarines Sur, Cavite, Isabela,
Laguna, Nueva Ecija, Nueva Vizcaya,
Occidental Mindoro, Oriental Mindoro,
Palawan, Pangasinan, Quezon, Rizal, Sor-
sogon, and Zambales in Luzon; Cebu and
Iloilo in the Visayas; and Cotabato and
Zamboanga del Norte in Mindanao. In
areas where sweet potato or cassava was
grown during the survey, 300 cc soil
samples containing pieces of roots were
collected from the root zones of stunted
plants. The number of samples collected
from each sampling area varied with the
size of the area planted to sweet potato
or cassava. Three, five and ten samples
were collected from areas less than one-
fourth hectare, one-fourth to one-half
hectare, and more than one-half hectare
in size, respectively. These samples were
placed in plastic bags, brought to the
laboratory and processed for nematodes
within the week they were collected.
Nematodes were extracted from the soil
by the combination of sieving and Baer-
man funnel techniques described by
Thorne (1961). The presence of nematodes
in or on the roots was determined by
staining one-half to one gram pieces in
lactophenol-acid fuchsin and examining
under a dissecting microscope after
clearing. All the plant parasitic nematode
genera encountered were identified with
the use of HP microscope and quantified.
Evaluation of nematode population den-
sities was based on the number of nema-
todes extracted from 300 cc soil samples
containing pieces of roots using the fol-
lowing scale: trace, 1-30; light, 31-120;
moderate, 121-240; heavy, 241-450; and
very heavy, over 450.

II. Inoculation experiments

Batangas isolates ofR. reniformis from
sweet potato in Darasa, Tanauan, of M.
incognita acrita from sweet potato in
Banay-banay, San Jose and ofM. arenar-
ia from cassava in Talisay were increased
and maintained on tomato in the green-
house. R. reniformis was started from a
field population, whereas M. incognita

acrita and M. arenaria were each started
from a single egg mass culture. Species
identification of the two root-knot nema-
todes was based on examination of 25
perinneal patterns of egg laying females
Separate inoculation experiments to
determine the pathologic reactions of
sweet potato (Ipomoea batatas Poir, var.
"Bnas") to R. reniformis and to M.
incognita acrita and of cassava (Manihot
esculenta Crantz, var. Golden) to M.
arenaria were set-up. The experimental
plants used were two-week-old .:rooted
cuttings grown singly in 30-cm diameter
clay pots containing baked soil. In the
test for R. reniformis, a. suspension con-
taining approximately 7000 larvae was
poured onto the exposed roots of each of
five sweet potato plants and then covered
with soil. Five plants, whose exposed
roots received no nematode inoculation
but only an equal amount of the super-
natant from the nematode suspension,
were provided as check plants. In the two
other tests, egg masses of M. incognita
acrita and M. arenaria were introduced
onto the exposed roots of sweet potato
and cassava, respectively, with the use of
pointed forceps and then covered. The
source of egg mass inocula were tomato
plants that had been infected by the
root-knot nematodes for about two
months. The number of egg masses intro-
duced per plant were 25, 50 and 200 for
sweet potato and 25, 50, 100 and 175 for
cassava. Each level of both tests was
replicated four times, with one check
plant receiving no egg masses being pro-
vided in each replicate. The experimental
plants in each test were randomly ar-
ranged on top of a cement floor. In the
test involving R. reniformis, the plants
were placed inside the greenhouse; in
those involving M. incognita acrita and M.
arenaria, the plants were placed outdoor.
Throughout the experiment, none of the
sweet potato runners were in contact
with the soil. The reactions of sweet
potato to R. reniformis inoculation were
determined two and one-half months

after inoculation, whereas the reaction:
of sweet potato to M. incognita acriti
inoculation and of cassava to M. arenaria
inoculation were determined only afte:
two months. This was done by obtaining
the weights of roots (feeder roots anc
tubers in the case of sweet potato) ant
tops. In addition, the number of R
reniformis in both soil and roots of swee
potato were determined from aliquo
samples. Nematode recovery was base
from 400 cc soil sample and 4 g roo
sample which were randomly obtain(
from the thoroughly mixed soil in each po
and thoroughly mixed root pieces (cho;
ped to about 2-3 cm long) of each plant
,,--*^A:..*1. Tl.^ .^w4-A^an J*^- 4la.r

Population densities of plant
parasitic nematodess:

A. Plrnt parasitic nematodes found
associated with sweet potato. The
association of 10 genera of plant parasitic
nematodes with stunted sweet potato
was observed. These were Rotylen
chulus, Meloidogyne, Helicotylenchus
Hoplolaimus, Tylenchorhynchus, Aphe
lenchus, Pratylenchus, Ditylenchus, Cr
conemoides, and Hemicycliophora. Rot3
lenchus, and Meloidogyne in different
ferent developmental stages, including
egg-laying individuals, were observed ii
feeding positions in stained roots. N,

ation of root and top weights. Sur, and in Caduanan, Borbon, Cebu
heavy in Tabi, Lubang, Occidental Min
RESULTS doro; and very heavy in Darasa, Tanauan
Batangas and in Tagaytay City. Soil infes.
The localities where sweet potato and stations by Aphelenchus in Insay, Davac
cassava were grown during the survey City and Tylenchorhynchus in Darasa, Ta.
from which soil samples were collected nauan, Batangas were very heavy and
are shown in Table 1. These consisted of light, respectively. The maximum popu.
16 provinces, 38 municipalities (towns lation density of each of the other genera
and cities) and 42 sampling areas for encountered was only light.
sweet potato and 19 provinces, 46 muni-
cipalities and 59 sampling areas for cas-
sava. A total of 114 and 230 samples
where obtained for sweet potato and
cassava, respectively.

Table 1. Lfstnroution ana pyputarton aenslry oj piant parasuic nemrruaue urn swecr
potato and cassavaa/

No. of
colcted Rot. Mel. Hel. Hop. Tylen. Othen
I. Luzon
1. Albay
a. Salugan, 3 20(67)+ 2(33) 17(33)
Camalig Prat.
b. Pefiafrancia, 5 140(100)+ 2(40)
2. Batangas
a. Banay-banay,
San Jose 2 194(100)+ 4(50)* 4(100)
b. Darasa, Tan- 6,997-
auan 5 100+ 14(60) 4(80) 34(100)
3. Benguet
a. Pico I, La Tri-
nidad 3 3(33)
b. Pico II, La Tri-
nidad 5 3(20) 1(20)
4. Camarines Norte 6(
a.Bagasbas,Daet 7 5(14)+ 6(14) 14)

5. Camarines Sur
a. San Isidro, Baa) 3 180(100)+ 2(33)
b. Bolo Sur,
Sipocot 5 1(20)* 1(20)
6. Cavite
a. Palapala, Das-
marinas 3 10(100)
b. Buho, Silang 3 1(33)+ 1(33)* 1(33) 6(100) 18(100
c. Tagaytay City 10 448(100) 1(20) 11(90) 6(100)
7. Isabela
a. Magsaysay,
Naguillan 3 No plapt arasitic aematod s were observed
b. Villa, Magat,
San Mateo 3 6(100 5(100 3(33)
8. Occ. Mindoro
a. Lilia, Lubang 3 14(100) 1(33) 1(33)
b. Tabi, Lubang 4 283(100)+ 4(75)* 6(25) 27(75)
S_ _ Aphel.

c. Igsusu, Paluan
d. Buenavista,

e. Labangan,
San Jose

9. Or. Mindoro
a. Nacoco, Cala-

10. Palawan
a. Mantible Sub-
Colony, Iwa-
b. Puerto Prin-
cesa City
c. Sta. Lourdes,
Puerto Prin-
cesa City
11. Quezon
a. San Isidro,
b. Ibanga, Sariay
c. Lalu, Tayabas
12. Zambales
a. Zambales
Breeding Sta-
tion, San Mar
b. Maloma, San
II. Visayas
1. Cebu
a. Caduananr, Boi
b. Insay, Danao
c. Libjo, Tabugol
2. Iloilo
a. San Matias,
b. Hamungaya,
c. Zarraga

3. Leyte
a. Damulanan,
b. Maybog, Baybi





























3(40)* 2(80)













c. Vac, Baybay
d. Montebello,
e. Cogon, Ormoc
f. Sumanga, Or-
moc City
III. Mindanao
1. Zamboanga del
a. San Ramon
Penal Colony
b. Sta. Maria, Zam
I. Luzon
1. Albay
a. Anislag, Daraga
b. Pefllafrancia,
2. Batangas
a. Don Luis, San
b. Taysan, San
c. Aya, Talisay

d. Diling, Talisay

3. Benguet
a. Pico I, La Tri-
b. Pico II, La
4. Camarines Norte
a. Bagasbas 1, Daet
b. Bagasbas II, Daet
c. Bagasbas III,
d. Basud, Daet

5. Camarines Sur
a. Sta. Cruz, Naga
b. Bolo Norte
c. Bolo Sur,
6. Cavite
a. Buho, Silang
7. Isabela
















No plant-parasitic nematode

No plant-p4rasitic n













a 1


s were observed

were observed.






a. Magsaysay,

b. Raniag, Ramon
c. Sinamar Norte,
San Mateo

d. San Andres,
8. Laguna
a. Looc, Calamba
b. Balay-hangin

c. Sta. Elena, San
Pablo City

9. Occ. Mindoro
a. Lubang

b. Mamburao

c. Igsusu, Palauan
10. Palawan
a. San Juan,
b. Mantible Sub-
Colony, Iwahig
c. Malinao, Narra

d. Bancao-bancao,
Puerto Princesa
City 3
e. Sta. Lourdes,
Puerto Princesa
City I 3
f. Sta. Monica, Puerto
Princesa City 3
11. Quezon
a. San Isidro, Lucban3
b. Ibanga, Sariaya 5
c. Lalu,Tiaong 2

d. Bulakan, Tiaong

- I- .













! 2




1(28)* 3(56)

1(40)* 112(100)

31(100) 2(67)





1(33)* 10(67)





















12. Rizal
a. San Guillermo,

b. Cuyambay, Tanay

13. Sorsogon
a. Del Rosario, Pilar
b. Lunoy, Putiao

14. Zambales
a. Alamat, Butulan
b. Maloma$an Felipe

c. Zambales Breeding,
Station, San Marce-

II. Visayas

1. Cebu
a. Gakit, Bogo
b. Fuente, Carmen

c. Magay, Compostela,
Cebu City

d. Insay, Danao City
e. Maslog, Danao City

2. Iloilo
a. Cabilawan, Barotoc
b. Dais, Dingle
c. San Matias, Dingle
d. Hamungaya, Jaro

3. Leyte
a. Lutao, Albuera











20(100) 2(100)*


























b. Maybog, Baybay
c. Montebello, Kananga
d. Can-adieng, Ormoc

e. Cogon, Ormoc City

III. Mindanao

1. Cotabato
a. Salimbao, Sultan

2. Zamboanga del Norte
a. San Ramon, Penal

- I._



L(20)* 3(40)

17(100) *






Key to symbols; + nematodes with egg masses were found in feeding position in
stained roots; *, nematode with egg masses were found in feeding position in stained
galled roots; (), percentages of soil samples where the nematodes were collected.

Key to abbreviations: Rot., Rotylenchulus; MeL, Meloidogyne; Hel., Helicotylenchus;
Hop., Hoplolaimus; Tylen., Tylenchorhynchus; Prat., Pratylenchus; Aphel., Aphelen-
chus; Cric., Criconemoides; Hem.,Hemicycliophora;Dit., Ditylenchus;Aphelen., Aphe-
lenchoides; Scut., Scutellonema.

B. Plant parasitic nematodes of cas-
sava. The most widely distributed
genus on cassava was likewise Rotylen-
chulus, followed by Helicotylenchus, and
Meloidogyne, in this order. Rotylen-
chulus was found in Isabela down to
Zambales, Rizal, Laguna, Batangas,
Quezon, Camarines Norte, Camarines Sur,
Occidental Mindoro, Albay, Sorsogon,
Palawan, Iloilo, Leyte, Cebu, Zamboanga
del Norte, and Cotabato; Helicoty-
lenchus, in all these provinces, except
Zamboanga del Norte; and Meloidogyne,
in Zambales, Laguna, Batangas, Quezon,
Camarines Norte, Occidental Mindoro,
Palawan, Iloilo, Leyte and Cebu.

Prevalence and frequency of occur-
rence i of plant parasitic nematodes.-Based
on the number of provinces, municipal-
ities and sampling areas where each of the
genera was collected; the prevalence of the

plant parasitic nematodes on sweet
potato and cassava was determined. This
information, together with the percentage
frequency of occurrence in the samples
are shown in Table 2.
A. Plant parasitic nematodes of sweet
potato. In descending order, Rotylen-
chulus, Helicotylenchulus and Meloido-
gyne were the most prevalent genera on
sweet potato. Out of 16 provinces, 38
municipalities and 42 sampling areas where
114 soil samples were collected, Rotylen-
chulus was found in 15 provinces, 32
municipalities and 34 sampling areas;
lHelicotylenchus, in 14 provinces, 27'
municipalities and 29 sampling areas; and
Meloidogyne, in 14 provinces, 21 muni-
cipalities and 21 sampling areas. In the
same order, these nematodes were also
the most frequently occurring, having
been found in 78.1, 49.1 and 47.3 per
cent of the samples, respectively.


B. Plant parasitic nematodes o
sava On cassava, the most prevalel
the most frequently occurring 1
were likewise Rotylenchulus, He,
lenchus and Meloidogyne, in this
Out of the 19 provinces, 46 mun
ities and 59 sampling areas from
230 soil samples were collected. Ro
chulus was found in 17 province
municipalities and 43 sampling
Helicotylenchus, in 16 province!
municipalities and 41 sampling area
Meloidogyne in 10 provinces, 18 Ir
palities and 19 sampling areas. TI
quencies of occurrence of these
todes in the soil samples were 50.8:
and 16.1 per cent, respectively.

is- II. Inoculation experiments
nd A. R. reniformis on sweet pot
Tra No apparent symptoms of damage
'y- observed both in roots and tops of
er two and one-half months after af
al- mately 7000 larvae were introduce(
re to plant roots. Table 3 shows th<
n- weight, top weight and number of
14 todes recovered. The average wei]
as; roots (consisting of feeder root
15 tuber) of inoculated plants, which
id significantly different from the ch
ci- P = 0.01, was 139.3 per cent hight
re- that of nematode-free plants (149.
la- 62.4 g). An increase of 22.9 per c
.9 top weight of nematode-inoculate
significant at P=0.05. Based on nenr

7000 149.3** 204.4* 474 17,983 18,457
(139.3) (22.9)

a/Data are means of five replicates.
b/Numbers in parentheses denote per cent increases compared to the check.
* and **Significantly different from the check at P = .05 and P = .01, respect

iquot samples (

matodes were recovered per pot. This
Timber was about 2.64 times the initial
oculum level of 7000 and equivalent to
increase of 163.7 per cent. Most of the
matodes were recovered from the
ots, 27.5 per cent of which were egg-
'ing female.

B. M. incognita acrita on sweet potato-
ble 4 shows the reactions of sweet
tato to different levels of egg mass
iculation. Only trace galling or very
v small galls formed on roots ofinocu-
,d plants. Some egg masses protruded
the surface of the root. No significant
=0.05) reductions or increases in
ights of either feeder roots, tubers or
th and of the tops were observed in

ble 4. Reactions of sweet potato to different

ants inoculated with 25, 50 and 200 egg
asses per plant.
C. M. arenaria on cassava.- The
actions of cassava to different levels of
g mass inoculation are shown in Table
Inoculation with 25, 50, 100 and 175
g masses per plant caused trace to
moderate galling of roots. No significant
S=0.05) reduction in weights of feeder
ots and tops were observed. On the
intrary, inoculation with 50 and 100
g masses per plant resulted in signific-
.t increases in top weight of 60.8 and
1.0 per cent, respectively. The top
sight of plants inoculated with 25 and
75 egg masses each were not significant-
different from that of the check.

The survey had revealed the widespread

'els of Meloidogyne incognita acrita ino-

Root weight (g) Top
No. of egg masses Gall rating Weight
per plant Feeder root Tuber Total (%)

0 (check 1.0 64.6 112.0 176.6 398.0
25 1.5 52.3 144.0 196.3 436.5
50 2.0 80.0 163.3 163.0 266.3
200 2.5 63.0 90.5 153.5 360.8

)ata are means of four replicates. No significant difference between the check mean and
ny of the treatment means was obtained at P =0.05.

ictons oi cassava to aijrerent levels of Meloiaogyne arenara inocul

ggmates per Weight in grams
lAnt Gall rating b
Feeder root Top'
,I / i i fA


a/Data are means of four replicates.
b/Numbers in parentheses denote per cent
*Significantly different from the check at

association of plant parasitic nematode
with stunted sweet potato and cassava i
the Philippines. The root-knot nematode
Meloidogyne spp., several species o
which have been known to cause appre
cable damage to sweet potato abroad
(Krusberg and Nielsen, 1958; Elmei
1959; Nielsen and Sasser, 1959; Martin
1967), was among those encountered
The other genera observed, which are alsi
probablepests of the crop (Martin, 1967)
included Rotylenchulus and Ditylenchu,
Root knot on cassava, caused by Meloidc
gyne sp.., which was previously report,
(Anonymous, 1960), was likewise ot

Amona the Wlant parasitic nematode

1 I

eases compared to the check.
3.05 with Duncan's multiple range test.

with no obvious above-ground signs o
symptoms of other pests and diseases) ii
each sampling area was determined. The
information obtained, however, was to n(
avail since in many instances, none o
only few plant parasitic nematodes wen
collected from soil and roots of these
plants. This suggested that the abnorma
conditions noted were due to othe
factors and not to nematodes. Determin
ation of plant age-nematode population
density relationship was also attempted
but also to no benefit, partly because in
secured. These and the probable effect
of seasonal variations had masked th
estimate of economic importance of the
nematode pests in the field. Nevertheless
the survey had also shown that Rotvlen

is and with M arenaria, respective- plant vathoeens observed should


MADAMBA, C.P., J.N. SASSER and L.A.NELSON.1965. Some characteristic
effects of Meloidogyne spp. on unsuitable host crops. N.C. Agr. Exp.
Bull. 169.34p.

MARTIN, W.S. 1967. Sweet potato diseases and their control. In A. Tai Eg
Proceedings of the international symposium on tropical root crops, Uni
Indies, St. Augustine, Trinidad.

ITPT RM NI W Indl IN SA.SERR 1959. Control of root-knot nematode affe(


A. J. Quimio
Assistant Professor, Department of Plant Pathology, UPLBCA.
Project supported by NRCP I.E. 42

The author wishes to acknowledge the technical assistance of R. D. Daquioag.

Bacterial leaf spot affects the leaves of both the red- and white-bract poinsettiasEuphorbia
pulcherrima Wild). It is characterized by circular to angular or irregular 1-2 mm diameter spots
with brown to reddish-brown centers. When viewed from the upper surface., the spots have
light yellow halos. But viewed from the lower surface of the leaf, the spots have wide dark
green to greasy-like margins. The spots, however, are distinctly brown with yellow halos when
focused through transmitted light. Several spots may coalesce, and kill large areas of the leaf.
The causal bacterium was named Xanthomonas pulcherrimae n.sp. based on patho-genecity
tests, and cultural, physiological, and biochemical studies.

Bacterial spot of poinsettia (Euphorbia
pulcherrima Wild.) was first observed by
the author in 1966 in the campus of the
College of Agriculture. University of the
Philippines at Los Bafios, College,
Laguna. If is destructive to both the red-
and white-bract poinsettia. At Los Bailos,
the disease is prevalent from July to
January which incidentally coincides with
the rainy season and also the blooming
season of poinsettia. It causes premature
defoliation of affected plants and is per-
haps, the most destructive disease of
poinsettia in the Philippines.


The disease affects only the leaves and
is commonly seen attacking the middle
age and young leaves. The first sign of
infection is the appearance of minute,
circular to irregular water-soaked, dark
green spots usually between the veins.
The spots enlarge to 1 to 2 mm in
diameter becoming angular or circular to
irregular in shape. When viewed from the
upper surface, the spots appear brown to

reddish brown in color with a very light
yellow halo; the brown necrotic centers
and yellow halos become very distinct
when the spots are viewed through tran-
smitted light. On the lower surface of the
leaf; the spots have brown to reddish
brown centers with wide dark green to
greasy-like margins (Fig. 1). When the
humidity is high, bacterial ooze could be
seen on the lower surface of the spots;
the ooze becomes small dirty white to
yellowish in color resinous granules when
dried. In advanced stage of the disease,
several spots coalesce covering large areas
of the leaf and the affected tissues turn
brown and die. Severely affected leaves
fall off prematurely.


The causal bacterium was isolated
from diseased poinsettia leaves collected
from the campus of the University of the
Philippines at Los Baflos, College,
Laguna, by plate streaking technique
using nutrient agar (NA). The isolates

. 1 Poinsettia leaf showing symptoms of b,
over flourescent light.

rial leaf spot. Specimen photographed

were purified by repeated streaking an
isolating of single colony isolates on NA.
Studies of the morphological, cultural
physiological and bio-chemical character
of the bacterium were made according t
the methods outlined by the Society c
American Bacteriologists (1957), unless
otherwise indicated. Six isolates selected
from several single colony isolates which
had been proven highly virulent to poir
settia in pathogenicity studies were used
All cultures were maintained in sterile
distilled water in screw-capped tubes a
20 C (Kelman, 1956.) Fresh culture
whenever needed were prepared on NA
Duplicate to triplicate cultures were use
in each test. Cultures for observation wer
incubated at 28 to 30 C unless otherwise
indicated. The following tests and studio
were conducted:
Cell morphology and Gram stain rn
actions.-Cell shape, size and arrangement
were studied in hanging drop preparation
and methylene blue stained smears fror
24 hr. old NA slant cultures. The Grar
reaction of cells from 16-hr old to 4-da'
old NA slant cultures was studied usin
Hueker's modification of Gram stain.

Colony type andgrowth on agar slant.
These were studied on nutrient aga
(Difco nutrient broth plus 1.5% Difc
Nutrient broth. Difco nutrient brot
was used.
Litmus milk. -Difco litmus cream-fre
milk was used.
Gelatin utilization. Liquefaction b
stab cultures of 12% gelatin at 20C wa:
Motility.- Motility was stuided in hanj
ing drop slides and ascertained by flagell
staining according to the method c
Rhodes (1958).
Sodium chloride tolerance.-Growt
was determined in Difco nutrient brot
containing 1 to 10% sodium chlorid(
Cultures were observed for 2 weeks.
Hydrogen sulfide production.- Hydr(
gen sulfide production from l%tryptor
broth was tested using the lead acetati

impregnated filter paper method. Th
isolates were also tested for hydrogen
sulfide production from lead acetate aga
(Difco manual. 1953).
Pectolytic activity.-Sutton's method <
testing for lipolytic enzymes was usei
(Sierra, 1957).
Utilization of amino acid as source o
carbon and nitrogen.- Utilization of aspi
ragne was tested according to the metho
of Starr and Weiss (1943).
Indole production.- Indole production
from tryptone broth was tested usir
vanilla as a test reagent according to tl
method of Roessler and McClung (194;
Krumwiedes triple sugar agar.- Difco
krumwiedes triple sugar agar was used.
Production of pigment.-Clara's mec
ium (Clara, 1934) and Medium B of Kinj
Ward and Raney (King, etal. 1954
were used in this test.
Nitrate reduction. Reduction c
nitrates was tested in both Difco nutrier
broth and nutrient agar plus 0.1%sodiur
nitrate. Sulfanilic and a-naphthylinine rn
agents were used in the test for nitrites.

Catalase production. -Each 48-hr-ol(
nutrient agar slant cultures was flooded
with 2 ml of 10- -L ol (30%) hydrogen per
oxide and observed for catalase activity.
Starch hydrolysis.- Two to 3 days o]
streak cultures on nutrient agar wil
0.2% starch were flooded with Gram
iodine solution to test for starch hydr
Methyl red Voges Proskauer test.
The methods outlined by Dye (1961
were used.
Optimum temperature.-This test wa
carried out in Difco nutrient broth
temperatures of 9, 21, 23, 30, 32, and:
C. Optimum temperature. This test w
carried out in Difco nutrient broth
temperatures of 9, 21, 23, 30, 32, and 36
Optimum temperature for growth %
determined by observing turbidity 16 1
32 hr, and 2 days after inoculating tl
Utilization of carbon compound
The synthetic basal salts medium

Ayres, et al., (1919) was used to test the
utilization of different materials as osurces
of carbon. The carbon sources were steri-
lized with a Millipore filtration apparatus
and added aseptically to the previously
autoclaved basal medium with Brom
thymol blue in Smith fermentation tubes.
The carbon sources were a 1% concentra-
tion of the basal medium. The cultures
were observed for 3 weeks at room tempe-
rature (28 to 32 C).
(28 to 32 C).
Koser's citrate medium.-Difco Koser's
citrate medium was used.
Fermentative and axidative metabol-
ism of carbohydrates.-The fermentative
and oxidative metabolism of glucose was
tested according to the method of Hugh
and Leifson (1953).
Inoculations in pathogenicity and host
range studies were made as follows: Ino-
culations were done with the use of an
inoculator made up of six number 2
insect pins held together in a rubber
surface. The inoculator was simply
dipped into a turbid, 48-hr old NA
llltlire ml naneinnn then nri lepd nntn tha

plants. Inoculated leaves or
immediately bagged with d
bag which were then removed
Pricked and non-pricked co,

)f an atomizer the bacterial suspension
Mn the uninjured leaves.
Results of studies on morphological,
cultural physiological and biochemical
characterss of the bacterium are sum-
narized below:
Rods: 0.6 x 1.4/u on the average, with
wounded ends, occurring singly or in pairs,
notile by means of a single polar flagel-
um. Aerobic. Gram negative.
Gelatin: Strong stratiform liquefac-
Nutrient agar slant: Growth light yel-
ow, abundant, filiform, glistening, non-
luorescent odorless, brittle to viscid, no
changee in the color of the medium.
Nutrient agar colonies: Light yellow,
ircular, convex, entire, smooth, glisten-
Nutrient broth: Growth odorless,
moderate clouding viscid sediment.
Titmnii milk- TI avpntr in nru wUpp

onization or digestion.

Lau inanJVy k 1 7JTy.
Sodium chloride tolerai
growthh in 3% salt, no growth

- i-ter pal

On poinsettia the initial water-soaked
spots were visible on inoculated leaves 48
ir after inoculation. The spots enlarged,
became angular to irregular in shape with
reddish brown to brown centers and wide
dark green to greasy-like margins when
viewed from the lower surface after 5 to
7 days. The bacterium was readily re-
isolated from the spots. The disease was
also reproduced by spraying with the use

Acla out no gas irom Ayres, iupp anu
[ohnson's (1919) solution plus the fol-
owing glucose, mannose, xylose, sucrose,
actose, raffinose, and glycerine. Manitol
and dulcitol not utilized.
Starch strongly hydrolyzed.
Sodium pectate medium not liquefied
Methyl red test, negative.
Acetylmethylcarbinol not produced.
Nitrites not produced.

-- ..-... 1-1

Sodium tartrate not utilized.
Koser's citrate medium, growth.
Synthetic asparagine medium,
to growth.
Glucose metabolized oxidatively in
-lugh and Leifson's medium.
Catalase activity, positive.
Optimum temperature, 28-32 C.

The morphological, cultural, physiologi-
al, and biochemical characters of the
scterium under study are typical of the
mnus Xanthomonas as described in
ergey's Manual of Determinative Bacter-
logy (1957). Its important characters
include the ability to liquefy strongly
latin, to hydrolyze strongly starch, to
produce indole and inability to liquefy a
ectate medium, to produce nitrates, and
Utilize dulcitol and mannitol. Admit-
idly, however, the bacterium is difficult
Separate from other Xanthomonas
iecies whose characters had not been com-
etely described for one reason or ano-
ler or when differences between it and
ime species are narrowed down to one
r two characters (see Burkholder, 1957).
his problem of inadequacy of the usual
eterminative tests for the identification
F Xanthomonas species has been pointed
it by Dye (1962).
Results of inoculation studies, how-
'er, showed that the bacterium is spe-
fic to poinsettia. None of the following
ants artificially inoculated with the
icterium was infected at the end of the
weeks observation period: Euphorbia
rta, Hevea brasiliensis, Manihot escu-
nta, and Ricinus communis all mem-
ers of the family Euphorbiaceae to
which poinsettia belongs. Glycine max,
ryza sativa, Otrus grandis, Desmodium
ffusum, Dieffenbachia picta, Begonia
L, Datura sp., and Codiaeum sp. which
e some of the known hosts of other
ecies of Xanthomonas whose characters
rerlap the characters of the bacterium
ider study (See Burkholder, 1957).
Specification in the genus Xanthomonas
to a large extent, based on host speci-

:ity (Burkholder, 1957), a character
which does not indicate natural relation-
ips between species but has surely
rved the plant pathologists well over the
ears. And it appears that despite the
problems associated with such basis for
,eciation as underscored by Stolp et al.,
)65) and new methods and sophisti-
ited techniques, the value of host speci-
:ity in speciation of the Xanthomonas
anot simply be ignored, as pointed out
i Wernham (1948).

Speciation in the genusXanthomonas is
to a large extent, based on host
ecificity (Burkholder, 1957). a charac-
r which does not indicate natural rela-
mnships between species but has surely
rved the plant pathologists well over the
ars. And it appears that despite the
oblems associated with such basis for
eciation as underscored by Stolp et al

Goto and Starr (1972), for instance,
owed that temperate phages of X citri
sogenized X. phaseoli and X. begoniae
dicating the non-specificity of the
Lage-host technique; there are in fact
.merous references to this type of rela-
onship in other phytopathogenic bac-
*ia. El-Sharkawry and Huisingh (1971)
-re able to differentiate a few Xantho-
mnas species using polyacryiamide gel
ictrophoresis of soluble proteins. How-
ar, the value of this technique has yet
be evaluated using not only a large
mber of species but also several isolates
the same species. The value of nume-
al taxonomy (Colwell and Liston
61) and analysis of DNA bases compo-
ion and DNA hybridization as taxo-
mic tools at the species level (De Ley,
63) have been reported and admit-
lly, these new techniques could bring
out the reduction in the number of
ecies not only in Xanthomonas but also
wudomonas (see also de Ley and Muy-
im, 1963: De Ley et al. 1966; Mandel
66; Rhodes, 1961) The problem, how-
er, arises when it appears that with
,se techniques and extensive nutritional

studies (Stanier, et. al., 1966). there is
very little justification for separating the
genera Xanthomonas and Pseudomonas.
Moreover, high natural similarity between
known species of Xanthomonas and Pseu-
domonas has been shown with these
It seems that natural relationships at
the species level in the genus Xantho-
monas would be difficult to establish as
yet. And until such techniques that would
show clear cut differentiation between
species have been standardized and such
time that sophisticated equipment be-
come available to most phytobacteriolo-
gical laboratories, plant pathologists have


ANONYMOUS, 1953. Difco manual (9th
350 pp.

AYRES, S. H., P. RUPP, and W.T. Johnsc
in milk. U.S. Dept. Agric. Bul. 782.

BREED, R. S., E. D. G. MURRAY ai
determinative bacteriology. 7th ed. 1

BURKHOLDER, W.H. 1957. Genus II. Xa
Breed. E. D. G. Murray and N. R.
bacteriology. 7th ed. The Williams an

CLARA, F. M. 1934. A comparative si
pathogens. New York (Cornell) Agric

COLWELL, R. R. and J. LISTEN. 19
computer of some Xanthomonas and

DE LEY, J. 1968. DNA base compos
phytopathogenic bacteria. Annu. Rev

__ J. VAN MUYLEM. 1963.

to rely on the classical approach of using
cultural, physiological, and biochemical
characters in conjunction with pathogenic
behavior as main parameters in identify-
ing unknown plant pathogenic Xantho-
The bacterium causing leaf spot of
poinsettia described in this paper, there-
fore, is named Xanthomonas pulcher-
rimae on n sp.The specific epithet is
derived from the species name of its host,
poinsettia. Type cultures of the bac-
terium are deposited in the author's
culture collection at the Department of
Plant Pathology, UPLB-CA, College,
Laguna, Philippines.


on) Difco Laboratories, Detroit, Michigan,

919. A study of the alkali-forming bacteria

1. R. SMITH. 1957. Bergey's manual of
Villiams and Wilkins Co., Baltimore, 1094 p

monas Dowson. 1939, p. 152-183.In R. S.
h (Eds.) Berge's manual of determinative
[kins Co., Baltimore.

of the green fluorescent bacterial plant
)t. Sta. Mem. 159. 34 p.

Taxonomic analysis with the electronic
domonas species. J. Bact. 82: 913-919.

and hybridization in the taxonomy of
ytopathol. 6: 63-90.

: applications of deoxyribonuclei acid base

-- I.W. PARK, R. TIJTGAT and J. V. ERMENGEM. 1966. DNA homology
and taxonomy of Pseudomonas and Xanthomonas. J. Gen. Microbiol. 42: 43-56.

DYE, D. W. 1962. The inadequacy of the usual determinative tests for the identification
of Xanthomonas sp. New Zealand J. Sci. 5: 393-416.

1968. A taxonomic study of the Genus Erwinia. I. The "Amylovora
group. New Zealand J. Sci. 11: 590-607.

EL-SHARKAWY, T. A. and D. HUISINGH. 1971. Electrophoretic analysis of esterases
and other soluble proteins from representatives of phytopathogenic bacterial genera.
J. Gen. Microbiol. 68: 149-154.

GOTO, M. and M. P. STARR. 1972. Lysogenization of Xanthomonas phaseoli and X.
begoniae by temperate X. citri bacteriophages. Ann. Phytopathol. Soc. Japan 38:

HUGH, R. and E. LEIFSON. 1953. The taxonomic significance of fermentative versus
oxidative metabolism of carbohydrates by various Gram negative bacteria. J. Bact.
66: 24-26.

KELMAN, A. 1956. Factors influencing viability and variation in cultures of Pseudo-
monas solanacearum. Phytopathology 46: 16-17 (Abstr.).

KING, E. O., W. K. WARD and D. E. RANEY. 1954. Two simple media for the
demonstration of pyocyanin aad fluorescin. J. Bact. 66: 24-26.

MANDEL, M. 1966. Deoxyribonucleic acid base composition in the genus Pseudomonas,
J. Gen. Microbiol. 43: 273-292.

RHODES, MURIEL E. 1958. The cytology of Pseudomonas spp. as revealed by a
silver-plating staining method. J. Gen. Microbiol. 18: 639-648.

- .1961. The characterization of Pseudomonas fluorescens with the aid of an
electronic computer. J. Gen. Microbiol. 25: 33-345.

ROESSLER, W. G. and L. S. McCLUNG. 1943. Suggested method for use of vanilla as a
test reagent for indole and skatole production by bacteria. J. Bact. 45: 413. (Abstr.).

SIERRA, G. 1957. A simple method for the detection of lipolytic activity of
micro-organisms and some observations on the influence of the contact between
cells and fatty substrates. Antonie van Leewenhoek 23: 15-22.

SOCIETY OF AMERICAN BACTERIOLOGISTS, 1957. Manual of microbiological
methods. Mc Graw Hill Book Co. Inc., N. Y. 315 p.

Pseudomonas: a taxonomic study. J.

STARR, M. P. and J. E. WEISS. 1943. Gi
asparagine medium. Phytopathology

STOLP, J., M. P. STARR and N. L.
phytopathogenic Pseudomonas an<

WERNHAM, C. C. 1948. The species val
Phytopathology 38: 283-291.

Id M. DOUDOROFF. 1966. The aerobic
1. Microbiol. 43: 159-271.

h of phytopathogenic bacteria in a synthetic

JGENT. 1965. Problems in speciation ol
inthomonas. Annu. Rev. Phytopathol. 3:

if pathogenicity in the genus Xanthomonas


Assistant Professor, Dce
Project supported by Natural S,


The anthracnose organisms from six fol
were isolated and studied in pure culture.
symptoms on the leaves of the plants. Flowers
plants except for anthurium where the organic,
and cultural characteristics, as well as ho!
identified as Colletotrichum gloeosporioides P

In the course of an over-all investiga-
tion of the anthracnose organisms attack-
ifg Philippine crops, the author was
directed to collect ornamental plants
showing anthracnose symptoms. At-
tempts were made to identify the causal
organism based on cultural and morpho-
logical studies as well as host range.
Presented herein are the results of the
studies on the anthracnose organisms
attacking six leafy ornamentals (Co-
diaeum variegatum Blume, Philodendron
axycardium Schott., Diffenbachia picta
(Lodd.) Schott., Chlorophytum elatum
R. Br., Episcia cupreata (Hook.) Hanst.,
Dracaena fragrans (L.) ker. Gawl. and
four flowering ornamentals (Anthurium
hortulanum Birds., Phalaenopsis amabilis
(L.) Blume, Gerbera jamesonii Bolus,
Begonia sp.).


The disease usually starts as small
watersoaked spots on the leaf blade. The
spots increase in size, become brown and


Plant Pathology, UPLB.

e Research Center, U.P. Diliman


ornamentals and four flowering ornamentals
Organisms produced practically the same
Seldom affected in the case of the flowering
so causes spadix rot. Based on morphological
age studies, the causal organisms were all
the causal organism of most Philippine fruit

circular. Spore bodies of the organism can
be seen beginning at the center of the
spots usually arranged concentrically. (Fig.
IA) The diseased tissues later drop out
leaving a shot hole appearance on the
On slightly fleshy leaf blades like those
Phalaenopsis and Begonia, the lesions
show rotting starting from the center
(Fig. 1B). There is usually a marked
margin and advancing yellow halo sur-
rounding the lesion. In Anthurium, the
spadix is also infected where the rot
appears as tiny, angular, water brown
spots on the petals and sepals of the true
flowers on the spadix. These turn black as
the infected tissues ages.

Causal Organism

Isolation and growth. The causal
organisms were isolated from diseased
tissues using tissue planting technique. At
least one to three isolates were collected
from each host plants (Table I).

Fig. 1A. Symptom of anthracnose disease
spots with spore bodies of the ors

FigB.Rot. symptom on Phalaen

Fig. lB. Rotting symptom on Phalaeno

Diffenbachia picta showing watersoaked
m arranged concentrically.

amabilis leaves by the anthracnose

Table 1. Sources of isolates of anthracnose organism used in the present study.

Isolate Locality Date
Code Collected

Codiaeum variegatum Blume

Philodendrom oxycardium Schott
Diffenbachia picta (Lodd.)

Gilorophyton elatum R. Br.
Episcia cupreata (Hook,) Hanst.
Dracaena fragrans (L.) Ker. Gawl.
Anthurium hortulanum Birds

Phalaenopsis amabilis (L.)

Gerbera jamesonii Bolus

Begonia sp.


EC 1
TP 1

College, Laguna
Cebu City
Tanauan, Batangas
College, Laguna

College, Laguna
Bacolod, Negros
Quezon City
College, Laguna
College, Laguna
College, Laguna
College, Laguna

H 2 Calamba, Laguna

PS 1 College, Laguna
PS 2 Cebu City

GJ 2
BS 2

Tagaytay City
College, Laguna
College, Laguna
Lingayen, Pangasinan

Pure cultures were obtained for use in the
morphological and cultural studies and
for cross-inoculation experiments. All cul-
tures are deposited at the Fungal Culture
Collection of the Department of Plant
Pathology, University of the Philippines
at Los Bafios.

Growth characteristics The growth
characteristics of the isolates were ob-
served on four different culture media,
namely, yeast extract agar (YEA), Cook's
medium (CM), Sabouraud's ugar (SA)
and potato dextrose agar (PDA). Re-
sults show that all the isolates grew
fairly well on the four media (Fig. 2). In
most cases, orange spore masses appeared
on the surface arranged concentrically

around the colony surface. As the cul-
tures aged, the spore masses turned black
due to the development of stromatic
masses around each spore group resulting
in acervuli formation. Dashes of black
color on the colony surface were also due
to setae formation. In another pattern of
growth, the orange pustules appeared
here and there without forming con-
centric rings along the surface. These also
turned black as the cultures aged. In still
another pattern of growth, concentric
rings appeared by the formation of a
homogenous black coloration which are
the spores, along the surface of the agar
Morphology. Conidiophores are
thin-walled, hyaline, septated, arising






Fig; 2 Some isolates of anthracnose organisms growing on different agar media. (H 1
& H 2: Anthurium; DF 1 and DF 2: Diffenbachia, BS 1 & BS 2: Begonia TP
1 and TP 2 Dracaena (CM Cook's medium; PDA potato dextrose agar; SA
Saboraud's Agar: YEA yeast extract agar). Taken after 7 days incubation
at 30 "C without light.

from well-developed stroma-like tissues.
Each produces a conidium at its tip.
Conidia are ellipsoidal, hyaline and one-
celled. The length ranges from 10.2 to
20.251/m while the width from 3.4 to 6.8
/um Average size of the conidia is 15.12 x
5.28 pum Figure 3 shows the photomicro-
graphs of the conidia of some of the
anthracnose isolates from ornamentals.
The fungus produces numerous acer-
vuli on agar as well as on the host lesion
surface. They are either superficial or
sub-epidermal in the host tissues, orang-
ish. at first turning black due to the
production of setae as well as change in
color of the hyphae. Measurements of
100 acervuli from agar showed that the
diameter ranged from 100 to 320 pnm.

Setae are variable in number, dark
colored, 2-5 septate and thick-walled.
Length varies from 95 to 500/um
Hostrange. Infection tests on a
number of crops known to be hosts of
anthracnose organisms showed that all
the isolates from ornamentals infected
Carica papaya L, Citrus sp., Phaseolus
vulgaris L, Averrhoa bilimbi L, Cap-
sicum annuum L.,Raphanus sativus L,
Mangifera indica L, and Psidium guajava
L, No infection occurred on Musa sapien-
tum L., Lagenaria leucantha Rusby, Bras-
sica chinensis L, Solanum melongena L,
Daucus carota L, Sechium edula Sw.,
Cbcumis sativus L, and Lycopersicum
esculentum Mill. The host ornamentals
served as control.

Fig 3. Photomicrographs of conidia of some anthracnose organisms from orna-
mentals. a Gerbera jamesonii, b. Codiaem variegatum, c. Begonia sp. d
Anthurium hortulanum (x 800)

Colletotrichum and Gloeosporium a
the two fungal genera causing seriol
disease of plants called anthracnose. TI
organisms are semi-tropical and world
wide in distribution. They are known
attack fruits and vegetables as well
field crops.
The Index of Plant Diseases in tl
United States (1960) records the anthrax
nose causal agents of a number of t]
present experimental ornamental plar
as either Colletotrichum sp. or Gloeosp
rium sp. Only those of Philodendron ai
Episcia were Identified up to species,
philodendri P. Henn. & C. gloeosp
rioides Penz, respectively. This indicate!
need for establishing and identifying t
species attacking other ornamentals. Su.
is important as basis for controlling the
destructive pathogens occurring in oth
major crops.
An intensive isolation of organism
causing the typical anthracnose sym
toms on both foliage and flower
ornamentals reveals the occurrence
only Colletotrichum species. This A
based on morphological and cultural dal


ALEXOPOLOUS, C. M. 1962. Introdi
and London. 613 p.
BURGER, O. F. 1921. Variations in C
20: 723-736.
ELA, L M. & T. H. QUIMIO. 197
Colletotrichum gloeosporioides
165; USDA 531 p.
QUIMIO, T. H. 1975. Anthracnose orga
Science Research Center. Tech. R
VON ARX, J. A. 1957. Die Arten der

Sne presence or absence or setae s
rates Colletotrichum from Gloeospon
although, as Alexopoulous (1962) cla
this characteristic is so variable tha
validity in separating these two gene
questionable. All the isolates in the
sent study showed setae either in cul
or in host or both.
Laboratory studies indicate that
Colletotrichum species attacking P1
pine ornamentals is species gloeo
rioides, a widely distributed sp4
known to attack a number of Philip
fruits (Quimio, 1975). Von Arx (1!
divided the genus Colletotrichum
species mainly by their spore shapes,
and host. C. gloeosporioides has ellip
spores and a size range of 12-19 x 4-6
While the spore size range of the c
mental isolates is 10-20 x 3-6 urn,
minor difference cannot count it
from Von Aix's range due to the
variability common to the species
and Quimio, 1974; Burger 1921).
fairly uniform spore shape of the pre
isolates as well as their ability to inf
number of fruit hosts, does not pre
any problem to the identity of C gk
porioides Penz.


ry Mycology. John Wiley and Sons, Inc. I

totrichum gloeosporioides. Jour. of Agr.

culturall variability of Philippine isolate:
. from fruits. Phil. Phytopathol. 9:27
TED STATES. 1960. Agricultural Handb

is and diseases of Philippine crops. UP Na
rt No. 30. 48 p.
tung Colletotrichum Cda. Phytopath. Z.


Assistant Professors, Department of Plant Pathology, UPLB-CA

Project supported by FAR-019-73

During our studies on the control of Microscopic examination revealed that
mango anthracnose by postharvest treat- the organism is an Aspergillus species
ment, our attention was drawn towards exhibiting typically black and globose
an apparently new kind of rot on ripe conidial heads. The conidia measure 4.86
mangoes. The disease seems common in /um on the average, typically globose,
mangoes harvested in Batangas and Zam- appearing brown with walls irregularly
bales, and may necessitate further studies echinulated and rough. Conidiophore
on control, walls are smooth and thick, variable in
The first external symptom is water- length, usually 2/um in length by 20/um
soaking of the infected portion followed in thickness. The vehicles are almost
by slight depression of the developing globose, 45 to 65,um in diameter. The
circular lesion. Usually, the basal part of sterigmata are of 2 series, the primary
the fruit is affected but lesion can also sterigmata averaging 1.7 x 5/um while the
start from any part of the fruit. If the secondary sterigmata, more typically
lesion starts at the base, it spreads out phialide, averaging 9.5 x 3.Oum (Fig. 2).
fast and may rot the whole fruit. In
advanced cases, the lesion shows the The morphological characters of the
ence o wte celiu followed solate showed that it is Aspergillus niger
presence of white mycelium followed V. Tiegh (Raper and Fennel' (1965). Das
closely by abundant black pustule of Gupta and Bhatt (1946) have reported
spores (Fig. 1). Further incubation pro- latent infection of mango946) have Asper-
duced numerous sclerotia which are at laent infection of mangoes by Asper-
duced numerous scerotia which are at gillus spp. including A. niger causing rots
first white, turning light brown and may during storage. Verma and Kamal3
during storage. Verma and Kamal
cover the entire rotted fruit.
(1950) also reported mango rot caused by
Inoculation studies showed that leaves A. niger. As far as the authors know, this
were not susceptible to infection of the is the first record of the disease on mango
organism. Mode of penetration has not in the Philippines. Cultures of the fungus
been studied yet but it appears from ob- are deposited in the Department of Plant
servations that it enters through wounds, Pathology College of Agriculture, UPLB,
particularly through the pedicelscar. College, Laguna.


figure 1. Carabao mango fruits showing symptoms and signs of Aspergillus rot.

400 x

Figure 2 Camera lucida drawing of conidiophore and conidia of Aspergillus niger from

AND D. I. FENNEL. 1965. The genus Aspergillus. Williams and Wilkins
875 p.

PTA & R. S. BHATT. 1964. Studies in the diseases ofMangifera indica
it infection in the mango fruit. J. Indian Bot. Soc. 25: 187-203.

L & M. KAMAL. 1950. Rot of Mangifera indica Linn. caused byAsper-
20: 68-69.



Advincula, B.A., 2:1;3:1 Chinte, P.T., 1:31
Agrawal. K.C. 7:9, 8:1 Clemente, E.C., 2:18
Aguiero, V.M., 3:6; 4:8; 5:8 17; 6:5;7:1, Cortado, R.V., 4:3, 4; 6:1;8:2
6; 8:1, 2, 5, 10 Cortez, R.E., 2:3, 5, 19;6:1, 3
Alaban, C.A., 4:1; 6:1 Crisostomo, LC., 6:3
Alicbusan, R.V., 2:38; 3:5, 55
Alqueza, E.N., 5:18; 6:9 Dalmacio, S.C., 3:2; 7:11, 53; 8:72
Aragones, A., 3:14 Davide, R.G., 2:6; 3:3, 4:3, 4, 9,
Arena, C.V., 2:15 5:18, 29, 45, 55; 6:11; 8:2, 78
Armedilla, A.L, 5:9; 7:5 Deanon, J.R., Jr., 2:7; 12; 3:4
Amy, D.C., 3:18; 7:44 Dela Cruz, A.A., 7:8; 8:6, 21
Avelino, E., 4:17 De la Rosa, A.G., 5:29
Ayad, M.R., 3:10 Del Rosario. M.S., 1:17, 19, 30, 38,
2:9, 18: 3:17, 20, 35; 4:16, 17,
Bagoyo, P.D., 3:7 5:10
Bagoyo, P.L, 5:8, 39 Dimasuay, D., 7:4
Ballon, F.B., 3:1;4:2 Dimasuay, D.F., 8:1, 10
Banatin, C.C., 1:32 Divinagracia, F., 2:16
Bandong, J.M., 1:15, 29; 4:12, 13; 5:10; Divinagracia, G.G., 4:4; 5:2; 6:4, 16;
7:9:8:7 Dogma, I.J., Jr., 1:31, 41: 3:5
Baniqued, C.A., 129,32 4:2; 5: Domingo, V.L, 4:2
Baniqued, N.C., 5:1;6:9
Bantoc, G.B., Jr., 2:12 Eamchit, S., 5:2, 3
Barile, R.L, 1:34 Ebron, S.P., 4:13; 6:8
Barredo, F.C., 5:14; 6:55 Ebron, T.T., Jr., 3:11; 4:11, 13; 5:10,
Batoon, C.R., 1:15; 2:1;3:1 6:7 8: 7:8, 9, 8:7
Begonia, D.T., 4:42 Ela, V.M., 1::5; 5:15
Benigno, D.A., 1:17, 19, 30; 3:35 Elazegui, F.A., 6:83
Benoit, A., 5:18 Eloja, A.L., 1:31, 33, 35; 2:8, 9, 22,
Bergonia, H.T., 6:9 4:10
Blancaver, R.C., 1:31, 41 Espada, E.A., 5:18
Borromeo, J.D., 2:49 Estiolco, R.V., 5:4
Buddenhagen, I.W., 8:5 Eugenio, T.S., 4:5
Bustrillos, A.D., 5:10 Eusebio, MA., 1:32 5:4, 20
Exconde, O.R., 1:16, 32, 37; 2:6; 3:4:
Cagampang, I.C., 6:10
Caica, C.A, 1:29; 6:9 13; 3:19, 42; 4:39; 5:3, 4; 6:3,
Calica, C.A, 1:29; 6:9
Calinga, R.H., 1:17; 2:2; 3:15 16; 4:13; 7:2,3,35, 3;8:4
5:1, 13
5:, I13 Franck, G., 5:4, 5
Cal, R.P., 3:2
Cao, I.., 2:1, 5 Fuentes, F.D., 1:16, 32, 37; 2:6; 3
Cano, I.B., 2:18, 53 6
Caramancion, MJ., 8:9 6:4
Funtanilla, E.Q., 7:3
Carbonnell, M.P., 7:1, 4: 8:2
Castillo, B.S., 1:35; 2:3
Castillo, M.B., 7:15, 61 Garcia, 0., 7:9
Celebrar, F.R., 1:33 Gavarra, M.R., 1:31, 33
Celino, C.S., 1:30; 2:3;6:1, 3 Goseco, C.G., 2:12 3:7; 4:9; 58:39

Halos, P.M., 4'5. 6:4, 16; 7:2;8:8 Mendoza, D.E., 5:10
Hernaez, A.V., Jr., 3:1 Mendoza, E.M., 2:15
Hsieh, S.P.Y., 2:10 Merca, S., 7:9
Hsu, H.T., 2:10 Merca, S.D., 5:5; 6:7; 8:4-7
Hsu, S.T., 3:11,14 Mercado, V.M., 4:11, 75
Husmillo, F.R., 2:19 Molino, U.V., 1:30; 2:3
Morrison, LS., 7:15

Ignacio, LC., 3:5, 55 Napiere, C.M., 3:42
Ilag, LL, 8:30 Natural, M.P., 8:15, 6
Imperio, E.N., 8:8 Navarro, A.P., 3:7
International Rice Research Institute, 4:6 Necessario, R.S., 1:39
Isidro, D.S., 4:2 Nora, D.M, 12:4, 3:8, 9; 5, 9, 10: 7:5
Novero, E., 3:18
Jackson, C.R., 8:12 Nuque, Fi L. 1:36, 38; 2:15, 16, 8:10 -12
Jaquias, F.C., 5:9 4:11-13; 5:5. 10, 12:6:7, 8;7:6, 8, 9;
Jose, A.V.A., 5:1 8:5-7
Josue, A.R., 6:5 Nwigwe, J.C., 7:6

Karganilla, A., 6:83 Obrero, F.P, 7:7
Karganilla, A.D., 7:3; 8:4, 5 Ocfemia, G.O. (Biog.), 1:5
Kauffman, H.E., 8:4 Olivares, F.M., Jr., 1:37; 4:5; 5:1; 7:8;
8:6, 21
Lacdao, P.D., 5:9, 10 Opefla, M.T., 1:31; 2:8, 31
Lantican, R.M., 1:20 Opina, O.S., 7:2,35
Lapis, D.B., 1:15, 34; 8:4, 66 Ou, S.H., 1:29, 31, 36, 38; 2:10, 15, 16;
Lawas, O.M., 2:13 3:10-14, 19; 4:11-13, 15; 5:2-5,
Lee, S.H., 5:8 10-12, 16, 17; 6:7, 8, 12; 7:3, 6, 8, 9,
Legaspi, B.M., 4:2 12; 8:1, 5-7, 10, 52
Lekagul, T., 3:20
Libed, L, 1:19
Librojo, M.T., 4:13 Pableo, G.O., 7:9, 29
""*o, M., 4:13 Paguio, O.R., 1:17, 38; 2:18; 3:35
Ling, K.C., 2:17; 3:6; 4:6-8, 11, 14, 16, Paguio, O.R., 1:17, 38; 2:18; 3:35
21; 5:6-8, 10, 16, 17; 6:5, 7:1, 3, 4 Palis .., 1:15
10; 8:2, 9, 10 Palis, R.K., 3:7; 4:9
Lopez, G.M.,4:39 .Palo, A.V., 1:15, 17; 2:2; 3:14-16, 18;
Lopez, M.E., 1:34 4:13;5:13
Palomar, M.K., 1:39; 2:17; 3:16, 27;

Madamba, C.P., 2:11, 12, 20; 3:7; 4:9, 4:14;5:6,12
17; 5:8, 39, 6:5, 6, 13; 7:13, 40; 8:35 Iama-Pacumbaba, E., 6:10
Madiac, V.M., 1:16 Panaligan, D.R., 1:30
Magda, T.R., 6:75 Pangramuyen, C.S., 3:17
Magnaye, L.V., 6:35; 2:22; 4:10 Paris, M., 7:3
Malimban, S.B., 6:3 Pascua, H., 5:8
Mangabat, N. 4:16 Pedrosa, A.M., Jr., 5:14; 6:8
Manglicmot, J.M., 2:13 Phanomsawam, K., 5:4
Manimtim, B.B., 6:12 Pizarro, A.C., 3:18; 4:91; 5:14, 18; 6:3,
Manzanilla, A.S., Jr., 2:13 9; 7:44; 8:12
Martinez, A.L., 1:35, 36; 2:14, 3:7-9; Pordesimo, A.N., 1:18; 3:60; 4:11, 15,
5:9, 10; 6:6, 62; 7:5; 8:49 75; 5:14, 15; 6:55; 7:13; 8:8
Mathur, S.B., 5:18 Price, W.C., 6:10; 7:9, 29; 8:9
Melgar, J., 1:39 Protacio, D.B., 6:10


izzaman, Ma., 4: 13; 3:1 azantamana, r..., .;lc
F.C., 4:16; 5:15, 52; 6:10, 75; Santos, L.G., 6:12
8:9 Sasser, J.M., 2:11
A.J., 1:18; 3:22 Schultz, O.E., 6:12; 7:
T.H., 3:22; 8:41 Sebastian, N.M., 1:36;
Silva, J.P., 1:36; 2:15

Reddy, A.P.K., 8:4
Reyes, T.T., 5:4, 15; 6:11
Retuerma, M.L, 6:10; 7:9, 29
Reynolds, D.R., 2:1, 17, 49; 3:19
Rillo, E.P., 8:9
Rivera, C.T., 3:16, 19, 27; 4:16,
6:11; 7:10; 8:1, 2, 9, 10
Rivera, J.R., 2:18, 53
Rodriguez, B.P., 2:7
Roldan, E.F., 1:16
Roperos, N.I., 5:17
Rosete, V.B., 5:15
Rubia, L, 2:1
Rubia, L.G., 3:1
Rubio, P., 2:38; 4:17
Russell, C.C., 7:15

Salibe, A.A., 2:3, 5, 19
Salisi, L.B., 7:8; 8:21
San Juan, M.O., 1:37; 4:5
Sanchez, P.C., 3:13, 14; 4:8


bunchy top of, 1:35
susceptibility of, to Pseudomonasi
nacearum, 3:20
by roguing methods, 2:31
spraying insecticides & cover
ping, 1:33
seasonal occurrencepf alate af
1\^tA +- 1- I1

Subido, P.S., 5:18

Tamayo, B.B., 5:15
Teru, D.T., 7:13
Toledo, R.T., 7:45
Triantaphyllou, A.C., 2:6
Trinidad, A., 5:18
Tunac, J.B., 4:88

Valdez, R.B., 1:19; 2:20
Valmayor, R.V., 8:8
Ventura, P.F., 1:29
Villareal, R.L, 1:20; 4:16
Von Chong, C., 3:11

Walawala, JJ., 4:17; 6:6, 13; 7:13,

Zapanta, R., 2:20
Zehr, EI., 3:20; 5:55; 6:29
Zentmyer, G.A., 1:53


antiserum against, preparation, 2:2
host range & symptomatology, 2:'
in relation to Echinochloa, 2:9
initial movement among the st
physical properties & host range,
physical properties & suscept rang
purification & electron microscop;

plant viruses, 2:3
transmission, 1:30
iCHLYA SPP., 3:5
LEGINETIA INDICA, control, with
herbicides, 1:34
AFLATOXIN, in agricultural crops, 8:12
kFRICAN OIL PALM, nematodes on,
AGARICUS BISPORUS, spawn produc-
tion of, synthetic compost for, 2:38
LLCOHOL, fermentation, by yeast iso-
lates, 3:5, 55
LMPALAYA, resistance to Meloidogyne
incognita, 3:4
ANTHRACNOSE, mango, control with
fungicides, 8:8
control of greening virus on citrus, 7:5
resistance of Xanthomonas oryzae to,
reproduction of, 4:3
APHIDS, alate, abaca mosaic related to,
cultivation of, 2:1, 49
physiological responses & character-
istics, 3:2
coconut, 4:88
rice, 1:36
chemical control, 7:9
effect of N & temperature, 3:11
effect on grain yield, 4:12
influence of nitrogen level on, 4:5
inoculation, 8:4
resistance to, 2:15, 3:10; 8:6
yield losses due to, 5:5; 7:2; 8:7

resistance to, 5:5
yield losses due to, 7:35
BACTERIAL SOFT ROT, papaya, 1:18
corn, 8:4
sorghum, 8:4

control, 7:7
influence of root-knot nematodes
on, 8:78
resistance to, 2:7
BACTERICIDES, systematic, for bac-
terial blight of rice, 7:9
BUD UNION CREASE, calamondin, 6:62
BUSH SITAO, Rotylenchus reniformis in,
population dynamics of, 2:2
BUTT ROT, pineapple, 4:1
bunchy top of, 1:35
cooking, "tapurok" disease of, 5:55
fruit rot of, control, 6:9
nematodes on, 6:6
control, 8:2
spotting of, 7:13
BANANA MOSAIC, field incidence of,
Cryptomela acutispora on, 7:44
spot blotch, etiology, 1:32
yelloe dwarf virus on, 3:18
3LASTOCLADIA SPP., fruit-trapping of,
BLIGHTING, coconut, 6:3

anatomical effects of, 3:18; 8:9
effects on carbohydrates of fruit,
CALAMONDIN Citrus madurinensis
Loureira), bud-union crease of, 6:62
host range & symptoms, 1:38
mosaic virus on, isolated from cadang-
cadang, 3:20
CEDAR CONES, England, nematodes
associated with, 5:14

. .- .. .laluul tv iJWIlUbpUd
control, effect on yield, 6:10 philippinensis, 8:72
CHEMICALS nematodes on, 6:13; 7:13, 40
Celdion S pathogenicity, 7:13
for bacterial blight, 8:.5 pathogenicity tests, 8:35
for Xanthomonas oryzae, 8:1 seed treatment, fungicides, effects
Demosan, for damping-off in crucifers, germination, 1:16
5:15 Tylenchorhynchus martini on, 7:
CHLOROSIS, zonate, of citrus, 2:3 8:35
3:60 phology & pathogenicity, 6: 12
CHLOROTIC STREAK, sugarcane, 2:18, phology & pathogenicity, 6:12
53 COTTON, seedling radicles, Phytl
CITRUS infection on 8:41
exocortis virus on, 2:5, 14 CRICONEMOIDES SPP., 3:18
inoculation method, 3:8 CROTALARIA MOSAIC VIRUS
inoculation method, 3:8
greening virus on, 5:10 7:5; 8:49 abaca, 2:7
transmission, 5:9
leaf-mottle-yellows virus on, reaction & symptoms, 1:38
to, 3:7 CRUCIIfERS, damping-off, control,
leaf mottling, 6:1, 3
nematodes on, 5:18 on barley 3:18; 7:44
psorosis virus on, 3:8 on oa,
seedling yellows virus on, 1:36; 3:9; CUC
8:49 downy mildew, chemical control
-. nowderv mildew. chemical coe

factors on, 6:4
bacterial leaf blight, 4:88
blighting, 6:3
cadang-cadang, 4:91; 5:10
anatomical effects, 3:18; 8:9
nematodes on, 4:91
root rot; 1:29
host response to root-knot
nematodes, 2:11
ring spot, 2:20
rust, control, 4:1
COMPOST, for spawn production
Agaricus bisporus, 2:38
bacterial stalk rot, 8:4
bacterial stripe, 7:3
disease, 6:89
downy mildew
control, 1:37; 6:12; 7:53
chemical, 7:11

ulmtlr t1ui -jr r
crucifers, control, 5:15
vegetable, control, 5:1

DEXTRAN, from Leuconostoc mesi
teroides isolates, 4:5
soils, 1:4
on mango, 6:4, 16
pycnidial and pycnidiospore prodi
tion by, 7:2
DISEASES (see also specific names
cor, 6:89
foliage, grapes, control, 8:8
mango, 8:8
sorghum, 6:83

nation to abaca mosaic virus, 2:9

GPLANT, histopathology of plants in-
fected by Phomopsis vexans, 4:4
saic virus, 1:39

WZYMES, produced by Pyricularia
oryzae, 8:52
HYLENE, production by Penicillium
expansum Link, 8:30
inoculation method, 3:8
in citrus, 2:5, 14

Aspergllus flavus, 8:12
Associated with deterioration of wood
products, 5:20
nucorales, in the UPCA campus, 3:1
iematode-trapping, 4:4
iematophagous, from animal manure,
rice straw compost & cultivated
soils, 6:11
Sclerospora philippinensis, on corn,
Sclerotium rolfsii, on vegetables, 4:75
wood rotting, identification, 2:15

4GICIDES (general)
'or blast, for corn seed treatment, 1:16
or rice seed treatment, 1:15
for blast, 7:9
for downy mildew of corn, 6:12
for Nephotettix virescens and Nila-
parvata lugens, 8:5
:est of, for downy mildew of corn,

NGICIDES (specific) (see also Fungi-
-ides, general)
Intracol, for soybean rust, 3:1
Arasan, for rice seed treatment, 1:15
Arasan 75, tolerance of P. oryzae to,
for powdery mildew of mung bean,
for rice blast, 6:7
for anthracnose & rots of mango,

for foliage diseases in grapes,
Blasticidin S. tolerance of P. oryzae to,
Captan 75, effects on germination of
corn, 1:16
Captan-Dieldrin, effects on germina-
tion of corn, 1:16
Ceresan M. effects on germination of
corn, 1:16
Chemical 1763, for rice seed treat-
ment, 1:15
Copper Curit, for potato late blight,
Copper Curit, for potato late blight,
Copper fungicide, for coffee rust, 4:1
Copper Lonacol, for soybean rust,
1:15; 2:1; 3:1
Copper oxychloride
for anthracnose & rots of mango,
for foliage diseases in grapes, 8:8
Cuproxol, for potato late blight, 3:2
Dithane M-22 and M-45, for potato
late blight, 3:2
Dithane X, for soybean rust, 1:15
Dithane Z-78, for soybean rust, 1:15
Dupont Fungicide 1991, for powdery
mildew & downy mildew, 4:2
Flit 406, foi potato late blight, 3:2
3-1143, for rice seed treatment, 1:15
3ranosan, for rice seed treatment,
linosan, for rice blast, 8:6
Carathane, for powdery mildew and
lowny mildew, 4:2
Casumin, for rice blast, 8:6
Citazin, for rice blast, 6:7
for anthracnose & rots of mango,
for foliage diseases in grapes, 8:8
daneb, for potato late blight, 3:2
4anzate D, for powdery mildew &
downy mildew, 4:2
lilcurb, for rice blast, 6:7
effects on germination of corn,
for rice seed treatment, 1:15
)rthocide 75. tolerance of P nrvuma

to, 2:13
Ortho-Cop, effects on germinatio
corn, 1:16
Panogen 15, tolerance of P. oryza
Polyoxin, for rice blast, 6:7
PRB-32, for rice seed treatment,
Semesan, effects on germination
corn, 1:16
Shell Copper Fungicide, for soyl
rust, 1:15; 2:1;3:1
Sulbar, for soybean rust, 1:15
Terraclor, for rice seed treaty
Tersan-Thiram, effects on germina
of corn, 1:16
for anthracnose & rots of ma
for foliage diseases in grapes, 8:
for rice blast, 6:7
Vancide Z-65, effects on germina
of corn, 1:16
FUSARIUM SPP., suscept range of,
FUSARIUM WILT, tomato, influence
root-knot nematodes on, 8:78

GARLIC, tangle top, control, 6:9
GERMINATION, corn, effects of ft
cides for seed treatment on, 1:16
GLOEOSPORIUM SPP., suscept ran
of, 6:9
GRAPES, foliage disease of, control,
causal agent-vector interaction, 5:8
rpaltinn tn 7-1

maydis, inheritance of susceptib
to, 1:20
sativum, on barley, 1:32
sigmoideum, mode of infection,:
HERBICIDES, Gesaprim, Karmex,
Telvar, for Aeginetia indica, 1:34
and sugarcane, 1:17
HOST INDEX, Philippines, proposal
compilation of, 2:59
banana to Fusarium & Gleospor
citrus to exocortis virus, 2:5
citrus to leaf-mottle-yellows virus,
coffee to root-knot nematodes,
rice to grassy stunt, 7:1
trifoliate orange to greening pathc
vegetables to Meloidogyne javal

of rice resistance to blast, 2:16
of rice resistance to grassy stunt,
for abaca mosaic disease, 1:33
for mungo mosaic, 8:2

KERNEL SMUT, rice, culture & artif
inoculation, 8:6
LEAF BLIGHT, sugarcane, 2:18, 53
LEAF MOLD, tomato, control, 4:15
distribution and vector, 6:1

on coffee, 2:11 Basudin, for nematodes on tobacco,
pathologic reactions of crops to, 4:9
4:52 Lannate, for nematodes on tobacco,
post-infection development, 2:20 4:9
resistance of tomato and ampalaya Mocap 10G, for nematodes on banana,
to, 3:4 8:2
susceptible hosts of, 3:3 Nemagon 20G, for nematodes on
javanica banana, 8:2
on coffee, 2:11 S Nemaphos 2E
reactions of vegetable and field effects on tomato, 3:16
crops to, 5:45 for Meloidogyne8 incognita, 3:15,
on palms, 3:18 16
4ETEOROLOGICAL FACTORS, effects Salvirex, for nematodes on tobacco,
on onset of citrus scab, 6:4 4:9
UILDEW Temik 10G, for nematodes on banana,
downy 8:2
chemical control, cucumber, 4:2 Zinophos, for root-knot nematodes,
corn, 8:72 4:13
corn, control, 1:37; 6:12; 7:11, 53
powdery NEMATODES (see also under genera of)
cucumber, chemical control, 4:2 abaca, 1:18
mung bean, control, 5:15, 52 associated with Saccharum sponta-
mungo neum, 6:6
forecasting outbreak of, 7:12 banana, 1:18; 6:6
resistance to, 6:1 cedar cones, England, 5:14
citrus, 1:18, 5:18
dITES, red spider, role on infection of coconut, 4:91
soybean with Pseudomonas glycinea, corn, 1:17, 6:13, 7:13, 40
8:66 pathogenicity tests, 8:35
4UNG BEAN in General Santos & Davao, 4:1
Cercospora. leaf spot on, control, 6:10 palms, 3:18
disease resistant varieties of, 6:1 ramie, 3:14, 4:9


as vector of rice tungro virus, 4:16; nematodes on, 7:61
5:6 resistance to Meoloidogyne hapla
as vector of rice yellow dwarf, 3:27 7:15
lity to insect resistant rice varieties, produced by, virulence, 8:30
adaptability to rice varieties, 7:10 PHENOLIC COMPOUNDS, in relation tc
as vector of rice tungro virus, 4:6 rice blast, 7:12; 8:57
loss of tungro infectivity by, 7:4 SOCITY
resistance to, 5:7 annual meeting abstracts of papers,
solution-feeding method for, 7:3 1:15; 2:1; 3:1; 4:1; 5:1; 6:1; 7:1
transmission of tungro by, 7:1, 4 8:1
NEPHOTETTIX PARVUS, as vector of charter member, 1:22
tungro yellow dwarf, 8:10 constitution, 1:16
NEPHOTETTIX VIRESCENS, effects of group picture of organizational meet-
systemic fungicides on, 8:5 ing, 1:2
adaptability to insect-resistant rice PHOMOPSIS VEXANS
varieties, 6:11 in eggplants, 4:4
breeding, for artificial inoculation, 3:6 pycnidial production, in agar culture,
effects of systemic fungicides on, 8:5 5:2
PHYLLACHORA SPP., in Los Bafios &
OATS, Cryptomela sp. on, 3:18 other parts of the Philippines, 3:2
ORANGE, trifoliate, response to greening Schizophyllum commune, 1:31
pathogen, 6:6 PHYTHIUM SPP., on cotton seedling ra-
ORYZA NIVARA, reaction to rice grassy dicles, 8:41
potato, chemical control, 3:2
PALMS butt rot, 4:1
cadang-cadang affected, virus isolate heart rot, 4:1
from, 4:17 Thielaviopsis paradoxa on, 6:1
nematodes on, 3:18 PIRICULARIA ORYZAE (see Pyricularia

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