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 Front Cover
 Title Page
 Table of Contents
 Introduction
 Literature from Florida
 Nature of the Javanese and other...
 Injury levels of the Javanese and...
 Comparative efficacy of a nonfumigant...
 Summary
 Reference






Group Title: Bulletin - University of Florida. Agricultural Experiment Stations ; No. 826
Title: Nature and extent of Javanese root-knot nematode damage to flue-cured tobacco in Florida
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Permanent Link: http://ufdc.ufl.edu/UF00027216/00001
 Material Information
Title: Nature and extent of Javanese root-knot nematode damage to flue-cured tobacco in Florida
Series Title: Bulletin Agricultural Experiment Stations, University of Florida
Alternate Title: Javanese root-knot nematode damage to flue-cured tobacco in Florida
Physical Description: 15 p. : ill. (some col.) ; 23 cm.
Language: English
Creator: Rich, J. R ( Jimmy Ray ), 1950-
Arens, Maria L., 1951-
Johnson, J. Troy
Publisher: Florida Agricultural Experiment Stations, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville
Publication Date: 1982
 Subjects
Subject: Tobacco -- Diseases and pests -- Florida   ( lcsh )
Root-knot   ( lcsh )
Nematode diseases of plants   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Bibliography: p. 15-16.
Statement of Responsibility: J.R. Rich, M.L. Arens, and J.T. Johnson.
General Note: "January 1982."
Funding: Bulletin (University of Florida. Agricultural Experiment Station)
 Record Information
Bibliographic ID: UF00027216
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000575269
oclc - 14268025
notis - ADA2674

Table of Contents
    Front Cover
        Front Cover
    Title Page
        Title Page
    Table of Contents
        Table of Contents
    Introduction
        Page 1
    Literature from Florida
        Page 1
    Nature of the Javanese and other root-knot nematode problems in Florida flue-cured tobacco
        Page 2
        Page 3
        Page 4
    Injury levels of the Javanese and southern root-knot nematode on 'McNair 944' tobacco
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
    Comparative efficacy of a nonfumigant and fumigant nematicide in Florida flue-cured tobacco
        Page 11
        Page 12
        Page 13
    Summary
        Page 14
    Reference
        Page 15
        Page 16
Full Text

January 1982


Nature and Extent of Javanese
Root-Knot Nematode Damage
to Flue- Cured Tobac aMi

J. R. Rich, M. L. Arens, and J. T. Johdso 4 i 1 IO

I.F.A.S. Univ. of Fiorida
Florida Agricultural Experiment lF onsv d
Institute of Food and Agricultural Sciences
University of Florida, Gainesville
F. A. Wood, Dean for Research


Bulletin 826













NATURE AND EXTENT OF JAVANESE
ROOT-KNOT NEMATODE DAMAGE
TO FLUE-CURED TOBACCO
IN FLORIDA


J.R. Rich, M.L. Arens, and J.T. Johnson

Dr. Rich is a faculty member of the IFAS Entomology and Nematology
Department at the Agricultural Research Center in Live Oak. Mr. Arens is a
graduate student in the Entomology and Nematology Department, Institute
of Food and Agricultural Sciences, University of Florida, Gainesville. Dr.
Johnson was formerly with the IFAS Agronomy Department at Agricultural
Research Center in Live Oak; he is currently with the University of Georgia
Cooperative Extension Service, Athens, Georgia.












CONTENTS

I. Introduction .................... ..................... 1
II. Literature from Florida ................................ 1
III. Nature of the Javanese and Other Root-Knot Nematode
Problems in Florida Flue-Cured Tobacco ................... 2
M materials and M ethods ................................. 3
Results ................... ..................... ...... 3
D discussion ......................... ..... .. ............ 4
IV. Injury Levels of the Javanese and Southern Root-Knot
Nematode on 'McNair 944' Tobacco ........................ 5
M materials and M ethods .......................... ....... 5
Results ................ .......................... 8
Discussion .............. ........................ 9
V. Comparative Efficacy of a Nonfumigant and Fumigant
Nematicide in Florida Flue-Cured Tobacco ................ 11
Materials and Methods .............................. 11
Results ............................ ..............12
D discussion ........................... ......... .. 13
VI. Summary ......................... ................. 14
References ............. ...... ....................... 15













Commercial names of products, where used, are for the purpose of providing
specific information. This does not imply any endorsement of named products
by IFAS, nor does it imply that named products are recommended to the
exclusion of other products of suitable composition.











I. INTRODUCTION
Over 10,000 acres (4,800 hectares) of flue-cured tobacco (Nicotiana
tabacum L.) are grown annually in 22 northern Florida counties, and
root-knot nematodes (Meloidogyne spp.) are recognized as the major
disease problem on this crop. Approximately 40% of the total annual
disease loss in Florida tobacco is caused by three root-knot nematode
species: southern (M. incognita), peanut (M. arenaria), and Javanese
(M.javanica) (17, 18). Root-knot nematode damage is more prevalent
and severe in Florida than in most other tobacco producing states.
Two factors are thought to be responsible for this: (i) the long growing
season and mild winters that allow for high population increase of
the three root-knot nematode species and (ii) the greater prevalence
of the Javanese and peanut root-knot nematode in Florida tobacco
fields as compared to some other states (20).

II. LITERATURE FROM FLORIDA
The first report of plant-parasitic nematode problems in Florida
flue-cured tobacco was that of Tisdale (21) in 1927, three years after
widespread introduction of flue-cured tobacco in the state (22). Tis-
dale indicated that considerable losses were due to root-knot nema-
todes, especially on sandy soils and during periods of dry weather. In
heavily infested fields, he found that plants were stunted and their
leaves were 'fired' early in the season. With lighter infestations,
tobacco growth was fair until flowering, when 'fired' leaf symptoms
appeared. Two of Tisdale's recommendations for root-knot control
[from vegetable work of Professor J.R. Watson, (24)] are still widely
recommended: late summer and fall fallow, and planting resistant or
immune cover crops.
Although numerous reports on root-knot nematode species in Flor-
ida tobacco were made, it was not until 1961 that a report of the
Javanese root-knot nematode appeared in literature. In that year,
Graham (8) found it in a tobacco breeding nursery at the University
of Florida, Gainesville. He indicated both the peanut and Javanese
root-knot nematodes were rarely found in Georgia, North Carolina,
and South Carolina, implying that they occurred more frequently in
Florida. Loh and Miller (13), and Miller (15) found that the Javanese
root-knot nematode predisposed black shank resistant cultivars to
this disease, and the black shank fungus, Phytophthora parasitica
var. nicotianae, had an apparent affinity for galled root tissue. More











I. INTRODUCTION
Over 10,000 acres (4,800 hectares) of flue-cured tobacco (Nicotiana
tabacum L.) are grown annually in 22 northern Florida counties, and
root-knot nematodes (Meloidogyne spp.) are recognized as the major
disease problem on this crop. Approximately 40% of the total annual
disease loss in Florida tobacco is caused by three root-knot nematode
species: southern (M. incognita), peanut (M. arenaria), and Javanese
(M.javanica) (17, 18). Root-knot nematode damage is more prevalent
and severe in Florida than in most other tobacco producing states.
Two factors are thought to be responsible for this: (i) the long growing
season and mild winters that allow for high population increase of
the three root-knot nematode species and (ii) the greater prevalence
of the Javanese and peanut root-knot nematode in Florida tobacco
fields as compared to some other states (20).

II. LITERATURE FROM FLORIDA
The first report of plant-parasitic nematode problems in Florida
flue-cured tobacco was that of Tisdale (21) in 1927, three years after
widespread introduction of flue-cured tobacco in the state (22). Tis-
dale indicated that considerable losses were due to root-knot nema-
todes, especially on sandy soils and during periods of dry weather. In
heavily infested fields, he found that plants were stunted and their
leaves were 'fired' early in the season. With lighter infestations,
tobacco growth was fair until flowering, when 'fired' leaf symptoms
appeared. Two of Tisdale's recommendations for root-knot control
[from vegetable work of Professor J.R. Watson, (24)] are still widely
recommended: late summer and fall fallow, and planting resistant or
immune cover crops.
Although numerous reports on root-knot nematode species in Flor-
ida tobacco were made, it was not until 1961 that a report of the
Javanese root-knot nematode appeared in literature. In that year,
Graham (8) found it in a tobacco breeding nursery at the University
of Florida, Gainesville. He indicated both the peanut and Javanese
root-knot nematodes were rarely found in Georgia, North Carolina,
and South Carolina, implying that they occurred more frequently in
Florida. Loh and Miller (13), and Miller (15) found that the Javanese
root-knot nematode predisposed black shank resistant cultivars to
this disease, and the black shank fungus, Phytophthora parasitica
var. nicotianae, had an apparent affinity for galled root tissue. More





*


importantly, the authors suggested that Javanese root-knot nema-
tode problems might be unique to Florida and extreme southern
Georgia. Miller et al. (16) further substantiated that the nematode
constituted a threat to tobacco production in Florida. They reported
that the Javanese root-knot nematode was found parasitizing roots of
southern root-knot nematode resistant cultivars in many locations.
Two additional reports concerning Javanese root-knot nematodes
dealt with variations in the pathogenic potential of Meloidogyne
species and their populations. Kirby et al. (11) showed differences in
the ability of the southern, peanut, and Javanese root-knot nema-
todes to cause gall formation on roots of the resistant 'NC 95' tobacco
cultivar. Five of six populations of the peanut root-knot nematode,
three of fourteen populations of the southern root-knot nematode,
and two of two populations of the Javanese root-knot nematode
caused gall formation on roots of this cultivar. Along similar lines,
Lopez et al. (14) evaluated the effect of several populations of the
southern and Javanese root-knot nematodes on growth of NC 95 and
'Hicks Broadleaf' tobacco. They found no differences between popula-
tions, and only the Javanese root-knot nematode caused root galls on
NC 95 tobacco.
This bulletin is designed to present further information on the
Javanese root-knot nematode, M. javanica, in Florida tobacco. The
information was generated at the Agricultural Research Center,
Live Oak, from 1977 to 1979.


III. NATURE OF THE JAVANESE AND OTHER ROOT-KNOT
NEMATODE PROBLEMS IN FLORIDA
FLUE-CURED TOBACCO
In the spring of 1977, 10 tobacco fields damaged by root-knot
nematodes were examined. Losses of up to 50% were found in these
fields. Laboratory analysis indicated that the Javanese root-knot
nematode was responsible for losses in six of these fields. A literature
search revealed several authors had indicated the presence of this
nematode species in Florida tobacco. The reports, however, did not
indicate the nature and extent of the problems caused by the
Javanese root-knot nematode. In addition, no records were found of
any systematic study of root-knot nematode problems in Florida
tobacco. Thus, a survey was initiated to determine: (i) tobacco loss
caused by the root-knot disease, (ii) the prevalence of the Javanese
root-knot nematode in tobacco fields, and (iii) control procedures used
by growers.





*


Materials and Methods
The survey was initiated in the summer of 1977 (July 15 to August
15) and included 10 tobacco fields in each of the three counties
(Columbia, Hamilton, and Suwannee) that produce approximately
50% of the tobacco grown in Florida. Each field was observed for
root-knot nematode damage, and a percentile loss assessment was
made at that time. The loss estimates were calculated as the percen-
tage reduction in yield and quality of the tobacco caused by the
root-knot disease. A survey form indicating acreage and nematode
control practices was completed for each field by the growers. If
root-knot foliar or root symptoms were detected, three root systems
were collected from each field. In addition, 10 subsamples of soil from
the root zone of the tobacco plants were collected to a depth of 12
inches (30 cm) in a random, circular pattern for each field. Soil
samples from individual fields were composite, mixed, and a 250 cm3
(0.5 pint) subsample was processed by a modified centrifugation-
sugar-flotation technique (9). After counting, nematode numbers
were converted to those found in 100 cm3 (0.2 pint) of soil. Galled roots
were dissected, and mature females of root-knot nematode species
were collected. From the females, 6 to 12 perineal patterns were
obtained and observed for identification of the nematode by the "two
characteristically well-defined lateral lines forming a definite break
in the striae" (25). When few root-galls were found in a field, soil was
placed in greenhouse pots, and 'Rutgers' tomato seedlings were
planted into the soil. If galls developed, perineal patterns were made
from mature females in the roots.

Results
Damage due to root-knot nematodes was found in 16 of the 30
tobacco fields and in 38% of the 184 hectares (455 acres) of tobacco
surveyed. These losses ranged from 50% in one field to the more
typical 1% to 3% damage levels. Total estimated losses attributable
to root-knot nematodes over the tobacco acreage surveyed were 6.3%.
The average number of larvae of all root-knot nematodes per 100
cm3 of soil was 851, and the highest number found in any one sample
was 7,232. In six of the 30 fields, larvae of root-knot nematodes were
not found. Analysis of perineal patterns indicated the presence of the
Javanese root-knot nematode in at least 14 fields and in 38% of the
tobacco acreage. Other plant-parasitic nematodes recovered were
lesion (Pratylenchus spp.), dagger (Xiphinema spp.), and ring (Macro-
posthonia spp). They were present in most of the tobacco fields, but
their numbers were quite low.








Table 1. Nematode control techniques used by tobacco growers in three
North Florida counties in 1977*.
Type of Nematicide Resis- 2 year*
Fumi- Non- Combi- tant Rota- Irri-
gant Fumigant nation Total Cultivar tion gation
% Growers 36 54 3 87 87 65 70
% Acres 48 36 16 95 91 72 83
(Hectares)
*Results of a random survey taken in a total of 30 tobacco fields and on 184
ha (455 A); approximately 10% of the acreage of the three counties was
surveyed.
*Data represents at least a two year rotation with corn, small grains or
pasture grasses.

Nematode control methods employed by tobacco growers, in gen-
eral, were similar to University of Florida nematode control recom-
mendations. Nematicides, resistant cultivars, and rotations were
used by the majority of the growers on a large proportion of the
acreage (Table 1). The nematicides included D-D (Shell D-D),
ethylene dibromide (Dowfume and Soilbrom), ethoprop (Mocap),
carbofuran (Furadan), and fensulfothion (Dasanit). The tobacco
cultivar 'Speight G-28' was grown on 65% of the acreage by 20
growers. Other cultivars grown in limited amounts were 'NC 2512',
'Hicks', and 'White Gold'. Timing of tobacco root plow-out, if any, was
quite variable among growers, and use of this control practice could
not be determined with any precision. Crop rotation was utilized by
most growers, although recommended rotation crops were not always
planted.
Discussion
Although nematode control practices were in wide use, losses due
to root-knot nematodes were prevalent and severe. This was due, but
only in part, to greater symptom expression and subsequent damage
brought about by an unusually dry season. Larvae of root-knot nema-
todes were present in high numbers in most tobacco fields despite use
of various control procedures by growers. Other plant-parasitic
nematodes were not found in high numbers or suspected to cause
damage to the tobacco surveyed. Miller et al. (16), however, indicated
that the lesion nematodes, P. brachyurus, and P. penetrans, have
been observed to cause damage to Florida tobacco.
Although the Javanese root-knot nematode was reported previ-
ously in Florida tobacco, the survey indicated that this species oc-
curred in 38% of the tobacco acreage surveyed. Recognition of the







presence of this nematode helps to explain many nematode control
failures, and this information adds a new dimension to future control
recommendations. Southern root-knot nematode resistant cultivars
and nematicide treatments were usually sufficient to reduce most
populations of this nematode below economic injury levels. Research
has shown this is not the case where moderate to high populations of
the Javanese root-knot nematode are present (1,3 and Section V). In
order to develop reliable nematode management programs, the root-
knot nematode species present, and population levels in the field soil
need to be determined. This identification would include the peanut
root-knot nematode as well as the Javanese root-knot nematode (13).
Furthermore, resistance-breaking biotypes of the southern root-knot
nematode have been reported in Florida (11). With the continued use
of resistant cultivars and the shortening of rotation intervals, prob-
lems caused by the Javanese root-knot nematode and those of other
resistance-breaking biotypes are expected to increase, not only in
Florida, but in other tobacco-producing areas in the Southeastern
United States. These problems must be met with shifts in nematode
management programs.

IV. INJURY LEVELS OF THE JAVANESE AND SOUTHERN
ROOT-KNOT NEMATODE ON 'MCNAIR 944' TOBACCO
In microplot tests conducted in North Carolina, Barker (3) found
that four root-knot nematode species differ in their ability to reduce
tobacco yield. Yield losses for each 10-fold increase in initial nema-
tode density on a susceptible tobacco cultivar were: Javanese 19.9%,
peanut 16.5%, southern 8.8%, and northern 3.7%. Studies have
shown the importance of at least two of these root-knot nematodes,
the southern and Javanese, in Florida tobacco production (16, 17, 18,
19). Although the southern root-knot nematode is the most wide-
spread root-knot nematode parasite in Florida tobacco, the Javanese
root-knot nematode causes the most damage in the field. In order to
improve predictive root-knot nematode management in Florida
tobacco and determine the reason for the greater Javanese root-knot
nematode damage, a study was conducted to: (i) establish the injury
levels of the southern and Javanese root-knot nematodes on this crop,
and (ii) to determine if one species was more aggressive (damaging)
than the other under Florida conditions.
Materials and Methods
In the fall of 1977, an area of Lakeland fine sand was treated with
881 pounds per acre (988 kg/ha) of methyl bromide, and two months
later, 64 fiberglass cylinders, 30 inches (76 cm) in diameter, were




























Figure 1. Fiberglass microplots in place at the Agricultural Research Cen-
ter, Live Oak.

installed into the soil (Figure 1). The microplot area was fallowed
over winter until planting. Microplots were sampled for nematodes
prior to planting, and no plant-parasitic nematodes were found.
In early April of 1978 and 1979, Javanese and southern root-knot
nematodes were added singly to microplots at three levels: 4, 16, and
64 nematode eggs and/or second-stage larvae per 100 cm3 (0.2 pints)
of soil. Soil was infested by adding a nematode suspension at the
appropriate concentration in water to each of 55 evenly spaced holes
3, 6, and 9 inches (8, 15, and 23 cm) deep within each microplot. One
day later, two plants of the tobacco cultivar 'McNair 944' were
planted 10 inches (25 cm) apart in each microplot. Eight replicates
per treatment were arranged in a randomized complete block design.
The microplots were kept weed free, fertilized, irrigated, and sprayed
for insects as needed to promote good plant growth and development.
Early-season, mid-season, and post-harvest soil samples were
taken 12 inches (30 cm) deep in the root zone of plants in each
microplot. The soil samples were each mixed, and 250 cm3 of soil was
processed by a modified centrifugation-sugar-flotation technique.
Tobacco roots taken from each sample were weighed, and nematodes
were extracted in Baermann funnels for three days (2). After the
last harvest, the tobacco root systems were rated for galling on a 0-4
scale (12).
























































Figure 2. Tobacco stunting and rimfire symptoms associated with heavy
infestations of root-knot nematodes,





0*

Tobacco leaves were harvested when mature. The leaves were
placed in paper bags, dried in an oven at 490C (120'F) and weighed.
The average soil temperatures at a depth of 4 inches (10 cm) during
April, May, June and July, respectively, were 260C, 29C, 34C, and
340C (790F, 840F, 930F, and 930F) in 1978, and 270C, 30C, 32C, and
330C (800F, 860F, 90F, and 910F) in 1979.
Results
In 1978, foliar symptoms caused by the Javanese root-knot nema-
tode were observed early in the season (ca 5 weeks) at the medium (16
nematodes per 100 cm3 of soil), and high (64 nematodes per 100 cm3 of
soil) initial inoculum levels (Pi's). Foliar stunting and necrosis of the
lower leaf margins, 'rimfiring', was obvious in many plants (Figure
2). Before the first harvest, these symptoms were found on several
plants inoculated with the low Pi (4 nematodes per 100 cm3 of soil) of
the Javanese root-knot nematode. By seasons' end, two plants from
the medium Pi of the Javanese root-knot nematode and five plants
from the high Pi had died. Roots of those plants were heavily galled
and deteriorated. Only plants inoculated with the high Pi of the
southern root-knot nematode showed widespread symptoms of nema-
tode damage including stunting and rimfiring. Occasionally, some
plants were found to be stunted at the low and medium Pi's of the
southern root-knot nematode. Similar results were obtained in 1979
except that plant symptoms and damage was more severe.
In both years, plants inoculated with Javanese root-knot nema-
todes yielded significantly less as compared to the control or tobacco

Table 2. Effect of the southern and Javanese root-knot nematode on the
tobacco cultivar 'McNair 944' leaf yield at three initial inoculum
levels (Pi).

Yield* (g)/
microplot
Root-Knot Pi
nematode species (nematodes/100 cm3 soil) 1978 1979
Control 0 380 at 355 a
southern 4 392 a 340 a
Javanese 4 272 b 273 b
southern 16 317 b 288 b
Javanese 16 270 c 180 c
southern 64 292 b 250 b
Javanese 64 174 c 112 c
*Average dry weight of two plants/microplot/treatment.
tMeans within an inoculation group followed by a common letter are not
significantly different (P< 0.05) according to Duncan's Multiple Range Test.





*

1978







C.Mi
------1979
800 ,000M0



2 6 0 0 03









1 4 16 64
Initial Inoculum Level / 100 cm Soil

Figure 3. Regression analysis of percentage yield reduction with three
initial inoculum levels of the southern and Javanese root-knot nematodes in
1978 and 1979 in the tobacco cultivar 'McNair 944'.


plants inoculated with southern root-knot nematodes (Table 2). In
1978, the Javanese root-knot nematode caused a 13%, 25%, and 58%
yield reduction at the low, medium, and high Pi's, respectively (Fig-
ure 3). At the low Pi, yield of tobacco plants inoculated with the
southern root-knot nematode was 3% greater than the control. At the
medium and high Pi's of the southern root-knot nematode, reduction
of tobacco leaf yield was 4% and 35%, respectively. In 1979, the
Javanese root-knot nematode caused a 19%, 31%, and 70% yield
reduction whereas, the southern root-knot nematode caused a 9%,
13%, and 31% yield reduction at the low, medium, and high Pi's
respectively.
Discussion
Microplot test results provided useful information on the effects of
initial inoculum densities of the southern and Javanese root-knot
nematodes on yield of tobacco in Florida. For purposes of discussion,
initial injury levels were arbitrarily set at the Pi which caused 7%
plant yield reduction. When using these criteria, initial injury levels
of less than 1 egg or second-stage larvae per 100 cm3 of soil were
calculated for the Javanese root-knot nematode in both years. Higher
initial injury levels of the southern root-knot nematode, 8 and 1, were








found in both 1978 and 1979. These low Pi's reflect the highly aggres-
sive nature of both nematode species on flue-cured tobacco as com-
pared to other crop plants (4). Data presented do not include effects on
tobacco leaf quality which would probably lower all injury levels
further.
Because of the low number of nematodes necessary to cause tobacco
damage, problems arise in correctly determining populations in the
field. It is suspected that these populations are at or below detection
limits of currently available sampling and extracting procedures. As
reported by several researchers, late summer or early fall sampling
would be more useful than spring nematode counts (23). In addition,
injury levels differed considerably between the 1978 and 1979 grow-
ing seasons, further indicating the need to assign ranges in initial
injury level determinations. It is thought that in these tests, plant
response to environmental variables was responsible for most of the
yield differences between years. For example, in 1979 soil tempera-
tures early in the season were higher than in 1978.
Results of the tests are in agreement with those of Barker (3) who
found that Javanese root-knot nematode was more aggressive than
the southern root-knot nematode on a susceptible flue-cured tobacco
cultivar. Nematode population data indicate that a greater early
season population development of M.javanica may be responsible for
differences in aggressiveness between these two species. Early in the
two tests (30 to 60 days), numbers of the Javanese root-knot nema-
tode were usually greater than those of the southern root-knot nema-
todes. As the season progressed, numbers of the Javanese root-knot
nematodes either declined or did not increase in proportion to those of
the southern root-knot nematodes. As evidenced from comparative
yield data and foliar symptoms, greater invasion and reproduction of
the Javanese root-knot nematode early in the season apparently did
not allow the tobacco root system to develop. Brodie and Dukes (5)
similarly found this nematode caused the most damage early in the
tobacco growing season. Conversely, invasion and reproduction of the
southern root-knot nematode occurred at a lower rate early in the
season and allowed the plants to develop more normally. Differences
in reproduction of these two nematodes have been found in growth
chamber experiments, but reasons for these differences are unclear
(1). Preliminary data, however, indicate the Javanese root-knot
nematode larvae locate and more readily invade tobacco roots than
those of the southern root-knot nematodes.
Microplots combine the advantages of (i) ease of handling; (ii) close
approximation to field condition; (iii) the possibility of incorporating
several nematode densities; and (iv) the establishment of fairly uni-








form densities within a treatment. It is a useful method for assessing
injury levels of a crop exposed to several preplant densities of plant-
parasitic nematodes. Microplot data, however, are only an approx-
imation of minimal damage densities (4). Homogeneity in nematode
populations does not occur in the field and calculated damaging
densities under field conditions can only be approximated. These
data, however, suggest growers should be aware that the presence of
even a very low Pi of the Javanese root-knot nematodes in a tobacco
field will cause reduction in yield. Since no resistant cultivars are
available, the other control measures must be optimally integrated to
prevent Javanese root-knot nematode induced losses in tobacco
fields.

V. COMPARATIVE EFFICACY OF A NONFUMIGANT AND
FUMIGANT NEMATICIDE IN FLORIDA
FLUE-CURED TOBACCO.
The effectiveness of nematicides for control of Meloidogyne species
in tobacco have been studied quite extensively in Florida (6, 7, 19).
Variable results have been obtained due to various environmental
and edaphic factors, nematode species, and nematode population
densities. Failure of some nematicides to provide sufficient control of
root-knot nematodes in Florida have been observed, particularly in
relation to infestations of the Javanese root-knot nematode. Sections
II and III provided partial answers to nematode control failures in
Florida tobacco. These data also suggested a need to provide more
specific information on nematicides of choice in situations where
moderate-high populations of the Javanese root-knot nematode ex-
ists and to a lesser degree, high populations of other root-knot nema-
tode species. Todd (23) has developed such a system in North Caro-
lina based on root-knot nematode population densities. This study
was conducted to determine the relative efficacy of two widely used
nematicides, a nonfumigant and a fumigant, for control of moderate-
high population levels of the Javanese root-knot nematode.
Materials and Methods
Field Test-1978. The fumigant nematicide, D-D (Shell D-D),
was chiesel-injected 8 to 10 inches (20 to 25 cm) deep in a broadcast
application three weeks prior to transplanting. Two rates of a 10%
granular ethoprop (Mocap) formulation were broadcast with elec-
tric Gandy applicators two weeks prior to transplanting and in-
corporated 3 to 5 inches (8 to 13 cm) deep by discing twice. All plots
were bedded at this time. On March 29, 1978, the tobacco cultivar








'McNair 944' was transplanted and plants were spaced 18 inches (46
cm) in the row. Plots were four rows wide and 27 feet (8.23 m) long,
and the six replicates per treatment were arranged in a randomized
complete block design. All data except root-gall indices were taken
from the two center rows. Cultural practices were based on recom-
mended practices in Florida and designed to promote good tobacco
growth.
Tobacco leaves were harvested when mature, and cured weights
were recorded. Nematode samples were taken preplant and 83 days
after transplanting. Eight soil cores from each plot were randomly
taken 5 inches (13 cm) from the base of the plants to a depth of 12
inches (30 cm). The soil was mixed and 250 cm3 of soil processed by a
modified centrifugation sugar-flotation technique. Root-gall indices
were taken 97 days after transplanting by randomly selecting two
root systems from each plot and rating these on a 0-4 scale.
Field Test-1979. Procedures in the 1979 test were similar to
those of 1978 except as indicated below. On March 22, 1979, an
ethoprop 4EC (Mocap) formulation was broadcast in 20 gallons of
water per acre (187 L/ha) one day prior to transplanting. Spray
application was made with a CO2 sprayer with Teejet 8004 flat fan
spray nozzles. Tobacco seedlings were spaced 20 inches (51 cm).
Nematode eggs were extracted from roots by using 1% sodium
hypochlorite solution (10), and these data were combined with num-
bers of nematodes recovered from the soil. Root-gall ratings were
taken 83 days after planting.
Results
In 1978, D-D significantly increased tobacco yield over ethoprop
treatments and the control (Table 3). The high rate of ethoprop (3 x )
produced significantly higher tobacco yield than the lower ethoprop
rate (1 x) or the control plots. No differences in tobacco yield were
found in the latter two treatments. The 3 x ethoprop rate produced
the lowest gall-index rating, and along with D-D resulted in the
lowest numbers of Javanese root-knot nematode larvae recovered
from the soil. During the growing season, it was noted that tobacco in
the control and 1 x ethoprop treatment exhibited leaf rimfiring and
other symptoms of root-knot nematode injury. No phytotoxicity was
observed in any of the tobacco plants, although an apparent phyto-
toxicity was found with the 3 x ethoprop rate after data analysis.
Data in 1979 were similar to those of 1978 and only minor differ-
ences were found. The D-D treatment produced the highest yield,
lowest nematode numbers, and lowest root-gall indices on the tobacco
root systems. Results of this treatment, however, did not differ sig-








Table 3. Use of D-D (Shell D-D) and ethoprop (Mocap) to control the
Javanese root-knot nematode in Florida flue-cured tobacco.

Rate in kg* Yield in No. of Javanese Gall indextt
Treatment active/ha kg/ha** after 83 dayst ratings
1978
D-D 187 (20) 3489 a 101 b 2.4 a
Ethoprop (3 x) 27(24) 3019 b 177 b 1.2 b
Ethoprop ( x) 9(8) 2535 c 683 a 3.2 a
Control 2451 c 509 a 3.3 a

1979
D-D 187 (20) 3202 a 460 b 0.6 c
Ethoprop (2 x) 18 (16) 2975 ab 690 b 0.8 be
Ethoprop (1 x) 9 (8) 2891 b 773 b 1.5 b
Control 2306 c 1858 a 3.9 a
*D-D rates are given in L/ha (gal/A) rather than active ingredients/ha,
parentheses indicate equivalents in lb a.i./A.
**Yield in lb/A may be found by multiplying yield by 0.89.
tInitial nematode populations were 101 and 412 larvae/100 cm3 of soil in
1978 and 1979, respectively.
ttAverage of two plants/plot at 97 and 83 days after transplanting in 1978
and 1979, respectively.
Means within tests followed by the same letter are not significantly
different (P<0.05) according to Duncan's Multiple Range Test.


nificantly from data obtained with the 2 x ethoprop rate. Differences
in tobacco yield, number of Javanese root-knot nematodes, or root-
gall indices were not found between the two ethoprop treatments.
The 1 x rate of ethoprop, unlike in 1978, significantly improved
tobacco yield and nematode control as compared to plots receiving no
nematicide. Phytotoxicity was not observed during the growing sea-
son in any treatment, and no apparent phytotoxicity was found after
analysis of the test data.
Discussion
Data from these tests indicated that a broadcast D-D application is
superior to the labeled rate of ethoprop (1 x) for increasing tobacco
yield and controlling high populations of the Javanese root-knot
nematode. Higher rates of ethoprop (2-3 x) provided adequate con-
trol. Problems of plant stunting as indicated from yield data in 1978,
however, may preclude high treatment rates and these rates are not
registered for use. Also, grower situations may be more extreme than
those in these tests. In the present experiments, tobacco was well
maintained and irrigated as needed to promote good plant growth.








Soil in the field was highly fertile and more heavily textured than
most tobacco producing soils in Florida. Thus, it is suspected that in
many grower fields, yield losses would have been higher than in this
particular situation. Lighter textured soils and variable manage-
ment conditions would require the most effective chemical available,
and these test data indicated D-D or similar fumigants as a broadcast
treatment would be the materials of choice. These data substantiated
findings of Todd (23). He suggested that D-D and other fumigants be
used where populations of root-knot nematodes are moderate to high,
whereas, ethoprop and other nonfumigants should only be used in
less severe nematode infestations.

VI. SUMMARY
Observations of the authors and data from these tests indicated
that the Javanese root-knot nematode is the most damaging nema-
tode pest in Florida tobacco. It is widespread on tobacco and has
caused several heretofore unexplained control failures. Reasons for
this include: (i) the more aggressive (damaging) nature of this nema-
tode as compared to the southern root-knot nematode; (ii) the inabil-
ity of nonfumigant nematicides to prevent damage by high popula-
tions of this nematode; and (iii) the absence of resistant tobacco
cultivars. It is suggested that growers with problems caused by
Javanese root-knot nematodes must optimally integrate control pro-
cedures to minimize losses from this nematode species. These prac-
tices would include rotation with grass crops, destruction of tobacco
roots, and use of fumigant nematicides.












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This publication was promulgated at a cost of $1513.80, or 50
cents per copy, to provide information on the nature and extent
of Javanese root-knot nematode damage to Florida tobacco.


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