JAN 26 i1998
Uijn ity of Florida
Research Funded by the Gadsden County Tomato Growers Association
and conducted at the North Florida Research and Education Center
1997 Progress Report
NFREC Research Report 97-7
TABLE OF CONTENTS
Growing Tomatoes in Pasture Sod:
An Alternative Production System Without Methyl Bromide ..................... 1
UV-Reflective Mulch and Nitrogen Fertility Effects on Western Flower Thrips
and Tomato Spotted Wilt Virus in Tomato .................................. 2
Tomato Spacing and Pruning Trial 1997 ......................................... 5
Utility of MI Gene Resistance in Tomato to Manage
Javanese Root-Knot Nematodes in North Florida ............................. 7
Tomato Variety Trials 1997 ................................................. 10
Mechanisms of Host Plant Resistance to Bacterial Wilt .............................. 13
Portable Evapotranspiration Gauges for Scheduling Irrigation of Fresh Market Tomatoes .... 15
Sap-Test Nitrate-N of Fall Fresh Market Tomatoes ................................ 17
Plant Diagnostic Clinic .................................................. ..... 20
Growing Tomatoes in Pasture Sod:
An Alternative Production System Without Methyl Bromide
Fred Rhoads, Soil Scientist
Fresh market tomato production in North Florida contributes more than $30 million annually
to the state economy. The pesticide, methyl bromide, is used in the popular raised bed film mulch
tomato production system. The use of methyl bromide allows tomato growers to produce tomatoes
year after year without crop rotation necessary to minimize soil-borne diseases that occur when their
reproductive growth is not suppressed during the cropping season. However, this pesticide has been
implicated as a contributor to ozone depletion and its use as a fumigant will be discontinued in 2001.
A system that requires crop rotation increases the amount of land necessary to produce a
tomato crop of the current production capacity because tomatoes may be included in the rotation only
one year in four. Therefore, more erodible land on steeper slopes would have to be used in order to
maintain the current production level. Many acres of pasture in North Florida that could be included
in a tomato rotation are on steeper slopes than those on current crop land. Strip-till systems in
agronomic crops have been shown to reduce soil erosion by allowing crop residue to remain on the
soil surface. Since the film mulch system increases erosion hazards by concentrating runoff on about
half of the cropland area and pasture sod is more effective in reducing erosion than crop residue,
strip-tilling tomatoes in pastures should minimize soil loss. The objective of this project was to
explore alternative tomato production systems in North Florida that do not depend on methyl
MATERIALS AND METHODS
Research was conducted to determine which factors were most limiting on tomato growth
in pasture sod and how long it would take for the pasture to regain full forage production. Effects
of mowing the sod, killing a strip and tilling, suppressing sod growth with non-residual herbicides,
fertilizer rates, and fertilizer scheduling were studied.
Soil-borne diseases and nematodes were not a problem in bahiagrass sod during a three-year
test. Roots from pasture sod growing between rows invaded the tilled strips and offered strong
competition for fertilizer elements supplied for the tomato crop. Competition from live sod for
fertilizer appeared to be the factor most limiting tomato yield. Suppressing sod growth with non-
residual herbicides was most effective in eliminating competition for fertilizer. When sod growth was
adequately suppressed fertilizer rates recommended for the current production system were adequate
for strip-till tomato in pasture sod. Compared to the raised bed film mulch system, soil erosion was
negligible with tomato grown in pasture sod. Furthermore, pasture forage growth recovered within
three weeks after tomato stakes and residue were removed from plots.
BENEFITS TO INDUSTRY
The strip-till in sod production system allows the use of highly erodible soils for proper crop
rotation and provides an alternative production system for fresh market tomatoes in North Florida
without methyl bromide.
UV-Reflective Mulch and Nitrogen Fertility Effects
on Western Flower Thrips and Tomato Spotted Wilt Virus in Tomato
J. E. Funderburk, P. C. Andersen, and S. M. Olson
University of Florida, North Florida Research and Education Center, Quincy, Florida
Western flower thrips (WFT) and tomato spotted wilt virus (TSWV) have become severe pests
problems in tomatoes in north Florida and in other crops around the world. In a recent survey, tomato
producers in north Florida identified WFT and TSWV as the major impediments to greater adoption of
integrated pest management. There is data to indicate that UV reflective mulch may prevent thrips from
colonizing tomato flowers. Also, plant nutrition is known to affect thrips populations. Based on
considerable research at the University of Florida, the recommended rate of nitrogen fertilizer is 180 lb/acre,
but producers frequently over-fertilize.
The objectives of the study were to examine the effects of mulches and nitrogen fertility on
populations of thrips and on incidence of tomato spotted wilt virus, and to determine nitrogen fertility
influences on the nutritional status of tomato and the nutritional ecology of thrips.
Materials and Methods
A replicated field experiment was conducted in 1996 and 1997 to develop and implement cultural
tactics for management of flower thrips and tomato spotted wilt virus in tomato in north Florida. A raised
bed plastic mulch system with drip irrigation was used. Tomatoes (cultivar 'Equinox') was transplanted
in late March of 1996 and 1997 at a row spacing of 1.8m. Only pesticides not affecting thrips and natural
enemy populations were used as needed.
Experimental design was a randomized complete block with 4 treatments and six replication. A
split-plot treatment arrangement was used with black and silver plastic mulch treatments as whole plots,
and moderate (190 lb/a) and excess (275 lb/a) nitrogen treatments as subplots. Subplot size was four rows
Western flower thrips on tomato were sampled by collecting ten flowers from the upper half of the
canopy from each of the two inner rows, equaling twenty flowers per plot per sample date. Flowers were
placed in 70% alcohol and thrips and natural enemies were extracted and counted. In 1996, thrips samples
were taken on 29 April, 10, 17, and 24 May, and 2, 7, and 16 June. In 1997, thrips samples were taken on
30 April, 7, 14, 21, and 29 May, and 6 June. The number of flowers on the upper half and whole plant were
determined for one tomato plant per plot per week.
Incidence of TSWV was determined in 1997. Each tomato plant was visually inspected for
symptoms, and one trifoliate from 2 plants showing symptoms per plot was analyzed by ELISA to
S corroborate visual diagnosis. The position of diseased plants was recorded in order to track the spread of
TSWV. Disease incidence was recorded on 7 and 21 May, and 6 June 1997.
Relationships between abundance of thrips and fertilization treatments were investigated further
by examining effects of fertilization on; 1) total flower nitrogen (protein), 2) flower protein quality (amino
acid profiles) and 3) indirect effects via increases in plant size or flower number. Chemical analysis was
performed on flowers collected at weekly intervals during the main experiment in 1996 and 1997. In
addition, relationships between flower chemistry and a wider range of fertilization treatments (0, 60, 120,
180, and 240 lbs/acre) were examined in 1997.
Effects of treatments on tomato yield and quality were determined by harvesting tomatoes from 12
healthy plants in one the outer rows on 19 June and 1 July in 1997. Fruit was graded to USDA standards
and marketable and unmarketable yield were determined.
Main effects and interactions between mulch and fertility treatments on densities ofthrips, incidence
of tomato spotted wilt tospovirus, and yield were determined using analysis of variance procedures for a
split plot randomized complete block.
In general, total numbers of adult thrips were greatest in black plastic mulch treatments and in
excess nitrogen treatments in 1996. Numbers ofthrips over time in 1996 are shown in the following graph.
Total number of adult thrips 1996
-*-- silver excess N
-*- silver recommended N
- black excess N
- black recommended N
In 1996, populations of the WFT, a vector of TSWV, were generally higher in the plots with excess
nitrogen, while populations ofFrankliniella tritici, the eastern flower thrips, which is a non-vector, was
not affected by fertility level. Numbers of WFT are shown over time in 1996 in the following graph.
Total number of adult WFT 1996
-A- silver excess N
-*- silver recommended N
- black excess N
- -- black recommended N
Although thrips samples have not been processed for all sample dates in 1997, thrips numbers again were
lowest in silver plots at the thrips population peak.
Incidence ofTSWV was significantly reduced in silver reflective mulch plots. Further, more plants
in the excess nitrogen treatments showed symptoms of the disease. Percent incidence of the disease on 6
June 1997 is shown in the following table:
TOMATO SPOTTED WILT VIRUS INCIDENCE IN 1997
MULCH NITROGEN % TSWV INCIDENCE (+ SEM)
SILVER RECOMMENDED 23.6 + 5.4
EXCESS 30.0 + 5.3
BLACK RECOMMENDED 40.0 +4.2
EXCESS 46.9 + 4.6
Silver mulch decreased the percentages of marketable fruit harvested per acre from healthy plants,
and yields from healthy plants were greater in the recommended nitrogen plots in 1997. The data are
presented in the following table.
TOMATO YIELDS 1997
MULCH NITROGEN MARKETABLE YIELD MARKETABLE
(251b BOXES/ACRE) ( SEM) FRUIT (%)
SILVER RECOMMENDED 1859+ 75.5 69.0
EXCESS 1736 + 159.0 69.4
BLACK RECOMMENDED 2101 + 99.4 76.4
EXCESS 1694 + 37.1 73.2
When the greater disease incidence in the excess nitrogen plots and black mulch plots was taken into
consideration, yield differences were not significant (data not shown).
A wide range of fertilization treatments did not alter flower protein contents. However, protein
content of tissue immediately adjacent to flowers (sepals) and tomato foliage were both positively correlated
to fertilization amounts. Western flower thrips are commonly seen on tomato sepals and commonly ingest
foliage in other plant species. Thus, increased nutrient content of plant tissue exterior to the flowers may
merit further investigation. Flower tissue (petals and interior) had 10-25% lower nitrogen concentrations
than adjacent tissue, but also lacked the long-chained phenolics that often bind with plant proteins.
Preliminary analysis of differences in both total protein and protein composition between the two highest
fertilization rates (those used for main experiment in 1996 and 1997) are slight; significance can only be
established after analysis is complete (chemical analysis is currently 65% complete).
Indirect effects of fertilization by increase in flower number was evident in both experiments.
Flower numbers per plant were roughly 15% higher during the period of maximum thrips abundance in
1996. Similarly, flower number was significantly higher on the most heavily fertilized plants (240 lbs/acre)
than on plants receiving the recommended rates of fertilizer (180 lbs/acre) in the multiple treatment
experiment (1997). In this experiment, plants receiving low rates and excess fertilizer flowered more than
plants receiving the recommended rate.
Benefits to the Tomato Industry
The results of this work are of immediate benefit to producers. Silver reflective mulch will be a
useful tactic for reducing thrips numbers in tomatoes, and it is a practice which is feasible to implement in
some production situations in Florida. Also, using recommended instead of excessive levels of nitrogen
decreases thrips populations and virus incidence.
Tomato Spacing and Pruning Trial 1997
North Florida Research and Education Center, Quincy, Florida
Many of the new cultivars that have been introduced recently have not only the ability to
produce high yields but also very large fruit (mostly extra-large). Usually the extra-large fruit bring
the highest price except when there is very little medium and large fruit to put on the market and
prices for smaller fruit may be higher. There are ways to reduce fruit mainly through competition.
Competition can result between plants (closer spacing smaller fruit) and within a plant (no pruning
or pruning to decrease or increase flower buds). This study was conducted to evaluate the interaction
of in-row spacing and degree of pruning on yield of'Agriset 761' tomatoes.
Materials and Methods
Study was conducted at the NFREC, Quincy on an Orangeburg loamy fine sand soil.
Production was on fumigated beds covered with black polyethylene mulch. Total fertilizer applied
was 195-60-195 lbs/a of N-P20O-KO2. Planting date was 24 March 1997. Plants were staked and
tied four times. Weeds, insects and diseases were controlled with timely applications of registered
pesticides. A factorial experiment was set up with three in-row spacing ( 18, 24 and 30 inches) and
three pruning methods (None; Light, half of suckers removed from ground to first fork and Heavy,
all suckers removed from ground to first fork). Plots were 30 feet long and replicated four times.
Plots were harvested three times and graded according to size and marketability.
Results and Discussion
Highest total yield and yield of all size categories occurred with the 18 inch in-row spacing
and no pruning (Table 1). In general the heavy pruning at each in-row spacing resulted in lower total
yields than the no pruning. There was no effect of spacing or pruning on percent marketable fruit.
Fruit size was affected more by pruning than by spacing. No pruning resulted in smaller fruit and fruit
size increased as degree of pruning increased. Results of this trial show that maximum yields were
realized with 18 inch in-row spacing and no pruning. One problem though with close spacing and
no pruning is the very dense bush that results and possible lack of good spray penetration to the
center of the bush.
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Utility of Mi Gene Resistance in Tomato
to Manage Javanese Root-knot Nematodes
in North Florida
J. R. Rich, S. M. Olson, and S. K. Barber
North Florida Research and Education Center
Use of plant resistance is an effective and efficient integrated nematode management
technique. Resistance to one or more root-knot nematodes is currently available in crops such as
soybean, tobacco, and bell pepper. In tomato,'Mi gene' resistance to major root-knot nematode pests
has been available for over 35 years. The gene has been incorporated into many commercially
available tomato varieties and used extensively as a root-knot nematode management technique in
home gardens and processing tomato production. While this resistance has some limitations, it is
generally effective in combination with other management techniques such as rotation. Until recently,
however, root-knot nematode resistance has not been incorporated nor tested in stake tomato
production systems in Florida. Reasonably, the extensive use of methyl bromide over the past 30
years precluded the need for varieties with this resistance. With potential loss of methyl bromide,
however, this resistance could become an important nematode management technique in Florida stake
The present tests were conducted to determine potential effectiveness of Mi gene resistance
in stake tomatoes to manage the Javanese root-knot nematode (Meloidogyne iavanica) in north
Materials and Methods
A small plot test site was located at the University of Florida North Florida Research and
Education Center, Quincy, FL. Soil was an Orangeburg loamy fine sand and was moldboard plowed
and double-disced in early March, 1997. Fertilizer was applied modified broadcast at the rate of 175-
54-175 of N-P2Os-KO2/A and disc-incorporated. Prior to experiment initiation, methyl bromide
(98%) was applied at a broadcast equivalent rate of 400 lbs./A. Application was made with a single
row bed press through 3 chisels spaced 12 inches apart on a 3 ft. wide raised bed and injected to 8
inches deep. Black polyethylene mulch (1.25-mil) and drip tubing were laid concurrently with methyl
bromide application. On 12 April, 0 or 500 Javanese root-knot nematode eggs or juveniles/100 cm3
soil were applied through the drip tube to 18 main plots each. Quantity of inoculum was calculated
to represent a soil volume equal to plots 10' long, 1 ft. wide and 6 inches deep. Two days later, two
transplants of the resistant Peto PSR 8991994 (Sanibel sister line) tomato breeding line and two of
the susceptible variety Colonial were planted into each main plot. Tomato was irrigated and sprayed
as needed to promote good plant growth. Fruit was harvested twice on 20 June and 8 July. Root gall
ratings were conducted on the two resistant and two susceptible plants in each plot on 11 July. Root
galling was estimated on a 0-10 scale where 0 = no root galling and 10 = 100% of the root system
galled. Additionally, five soil cores to 8 inches deep were collected separately around roots of
resistant and susceptible plants in each plot. Soil was processed with the modified centrifugation-
flotation technique and root-knot nematode juveniles counted.
A second test for Fall tomato production was conducted on the site of the Spring test. The
previously placed drip tubing and plastic mulch were removed. Fertilizer (117-36-117 of N-P20-
K,0/A) was then manually applied over the beds. Fertilizer incorporation by rototilling to 8 inches
deep, bed pressing and shaping were conducted in the same operation. White on black polyethylene
mulch and drip tubing was placed over the formed beds. The tomato varieties, Agriset (susceptible)
and Sanibel (resistant), were alternately planted on 22 August in main plots of the Spring trial. Total
tomato fruit, regardless of size, were harvested and weighed on 14 November. On 17 November, root
galling was estimated.
In addition to the above experiment station tests, an observational planting of PSR 8991994
was made on the Murray Brothers Farm in Decatur County, GA. Tomato was transplanted into a
strip-tilled bahiagrass site that had not been treated with nematicidal materials. A small area infested
with root-knot nematodes was located in the three acre site by soil sampling, and the PSR 8991994
was transplanted to approximately 100 feet of row. Rows on either side were transplanted to Florida
47 tomato on the same day, 1 April 1997. Plants were grown and harvested according to standard
grower practices. On 23 July, 12 randomly selected plants of the PSR 8991994 and 12 in an adjacent
row of Florida 47 were rated for root galling. Gall ratings were made on a 0-10 scale as described
In the Spring trial, no differences in tomato fruit weight, number of fruit or weight/fruit were
found between the noninoculated PSR 8991994 or Colonial tomato varieties (Table 1). In spite of
methyl bromide treatment, however, small residual populations of the Javanese root-knot nematodes
were present in this uninoculated control treatment. The resistant PSR 8991994 showed significantly
less root galling and nematode numbers as compared to the Colonial. In plots where nematodes were
added, the resistant PSR 8991994 significantly increased fruit weight, number of fruit and
weight/fruit, and reduced root galling and nematode populations over Colonial. In the Fall test,
significant differences in total fruit weight were found between the Sanibel and Agriset ( Table 2).
Agriset, even when showing high root galling, generally yielded better than Sanibel. Root galling,
however, was significantly reduced in the Sanibel where either low or very high populations of
nematodes were present. Similarly, at the on-farm observational site, large differences in root-galling
were recorded between the PSR 8991994 and Florida 47. The twelve randomly selected plants of
Florida 47 averaged a root gall rating of 7.4 while the PSR 8991994 average a rating of 0.25.
The PSR 8991994 and Sanibel exhibited excellent resistance to the Javanese root-knot
nematode in both the Spring and Fall trials as well as the on-farm site. While preliminary, these data
suggest that theMi gene may be useful as a nematode management technique in north Florida stake
tomato production. Experience from other tomato production systems indicate Mi gene resistance
is useful in reducing nematode damage in tomato, but it must be utilized in an IPM context to
maintain effectiveness. Continuous use has resulted in resistance breaking biotypes of root-knot
nematodes. Thus, alternating susceptible and resistance cultivars in field production or utilizing good
rotation systems has proven important to maintain usefulness of this resistance. Additionally, the
resistance tends to lose effectiveness as the soil temperatures increase above 80-85 OF. Further tests
are needed since this may limit use of the resistance at higher soil temperatures inherent in the Fall
tomato crop in north Florida. Also, other work is necessary to determine the stability of this resistance
to native populations of the three root-knot nematodes, southern, peanut, and Javanese, present in
Table 1. Yield, root galling and nematode numbers in a Spring field trial comparing the response of
a resistant and a susceptible stake tomato to the Javanese root-knot nematode. 1997.
Fruit No. Weight/ Root Nematodes/
Cultivar/line Nematodes1 weight2 fruit fruit galling' 100 cm3 soil
PSR 8991994 17.5 44 0.40 0.0 5
Colonial 18.7 49 0.39 0.8 163
LSD (P s 0.05) 4.3 11.5 0.02 0.5 111
PSR 8991994 + 23.1 56 0.42 0.1 132
Colonial + 15.6 40 0.39 7.0 4523
LSD (P 0.05) 4.0 9.3 0.02 0.8 2810
'Javanese root-knot nematode eggs and juveniles were applied at the rate of 0 (-) or 500 (+)/100 cm3
'Fruit was harvested twice and graded to eliminate culls.
'Root galling was based on a 0-10 scale where 0 = no galling and 10 = 100% of the root system
Table 2. Total fruit yield and root galling on root-knot nematode resistant Sanibel and susceptible
Agriset stake tomato, Fall 1997.
Cultivar Nematodes' Fruit weight2 Root galling3
Agriset -10.9 4.2
Sanibel -9.3 0.4
LSD (P s 0.05) 3.8 1.8
Agriset + 15.9 7.1
Sanibel + 9.7 0.7
LSD (P 0.05) 2.6 1.0
'Following a spring crop inoculated with Javanese root-knot nematode.
2Transplanted on 22 August, all fruit harvested on 14 November.
'Root galling was based on a 0 10 scale where 0 = no galling and 10 = 100% of the root system
Tomato Variety Trials 1997
S.M. Olson And J.M. Snell
Tomatoes are the most important vegetable crop in Florida. The 1995-96 crop was worth
about $440 million produced on 45,500 acres. Production in Northwest Florida has remained
somewhat constant at about 4,000 acres split between spring and fall crops. These seasons are quite
different from each other, especially the night temperatures. Tomato variety trials were conducted
in spring of 1997 with 24 entries and fall of 1997 with 17 entries to look at adaptability of new
hybrids to our production seasons.
Materials and Methods
Spring: Trial was conducted at the NFREC, Quincy on an Orangeburg loamy fine sand soil. Entries
were seeded into 1.5 inch cell trays on 10 Feb 1997. Transplants were placed in the field on 24
March 1997. Production was on fumigated beds covered with black polyethylene mulch. Plants were
pruned (light, ground suckers plus two), staked and tied four times. Total fertilizer applied was 195-
60-195 lbs/a of N-P2O,-K2O. Plant spacing was 20 inches in-row and 6 feet between rows (7,260
linear feet/a). Plots were 20 feet long (12 plants) and were arranged in a randomized complete block
design with four replications. Weed, insects and diseases were controlled with timely applications
of registered pesticides. Plots were harvested three times from 11 June to 2 July 1997 and graded
according to size and marketability.
fall Trial was conducted at the NFREC, Quincy on an Orangeburg loamy fine sand soil. Entries
were seeded into 2.0 inch cell trays on 30 June 1997. Transplants were placed in the field on 4 Aug
1997. Production was on fumigated beds covered with white on black polyethylene mulch. Plants
were pruned (light, ground suckers plus two), staked and tied four times. Total fertilizer applied was
195-60-195 lbs/a of N-P20s-K20. Plant spacing was 20 inches in-row and 6 feet between rows
(7,260 linear feet/a). Plots were 20 feet long (12 plants) and were arranged in a randomized complete
block design with four replications. Weed, insects and diseases were controlled with timely
applications of registered pesticides. Plots were harvested three times from 23 Oct to 17 Nov 1997
and graded according to size and marketability.
Results and Discussion
Spring: Yield information is presented in Table 1. At present the most widely used variety for spring
production is 'Agriset 761'. None of the entries produced yields higher than 'Agriset 761'. 'FT 4012'
produced the highest yields of extra-large fruit and was number 2 overall for total yield. 'XPH
10069', an Asgrow hybrid produced the highest total yield. 'Captiva' a new race 3 Fusarium wilt
resistant hybrid produced total yields equal to 'Agriset 761' but fruit were smaller. Percent
marketable fruit ranged from a high of 86.8 for 'XPH 10069' to a low of 43.9 for 'SRT 6657'. 'SRT
6657' had the largest fruit weight at 9.8 oz and 'FL 7658' had the smallest at 6.9 oz.
EalL Yields ranged from 2814 boxes/a for 'Equinox', a new UF release to 2127 boxes/a for 'Merced'
(Table 2). 'Equinox' also produced the greatest amount of fruit that were marketable. Fruit size
ranged from 7.7 oz for 'Merced' to 6.2 oz for 'Leading Lady'. 'FL 7763', an experimental hybrid
from the UF breeding program produced the highest yield of extra-large fruit.
Table 1. Tomato variety trial results Spring 1997. NFREC, Quincy.
Marketable Yield (25 lb boxes/A) Marketable Average
Entry Source Medium Large Extra Large Total (%) (oz)
XPH 10069 Asgrow 131 ae 548 a 1997 b-h 2677 a 86.8 a 7.2 i-k
FT 4012 Rogers 11 g 206 h-j 2448 a 2665 a 80.2 be 9.0 b
XPH 10091 Asgrow 26 d-g 260 f-j 2369 ab 2656 ab 81.0 b 8.2 d-g
SRT 6633 Sunseeds 98 a-c 435 a-d 2111 a-f 2644 a-c 77.0 b-f 7.4 h-k
*Agriset 761 Agrisales 38 d-g 355 b-g 2213 a-c 2606 a-d 73.8 c-h 7.9 f-i
Sun Leaper Rogers 92 bc 400 b-e 2040 b-g 2532 a-e 75.0 b-g 7.5 g-k
XPH 10072 Asgrow 22 e-g 275 e-j 2158 a-e 2455 a-f 71.5 f-j 8.0 e-h
PSR 842694 Petoseed 35 d-g 209 h-j 2151 a-f 2395 a-f 74.3 b-g 8.6 b-e
STM 5206 Sakata 23 e-g 180 j 2186 a-d 2389 a-f 67.4 h-k 8.7 b-d
SRT 6629 Sunseeds 30 d-g 262 f-j 2052 b-g 2344 a-f 72.3 e-i 8.3 c-f
Captiva Petoseed 104 ab 456 a-c 1764 f-i 2324 a-f 76.5 b-g 7.0 jk
FT 3260 Rogers 13 fg 184 ij 2115 a-f 2311 a-f 74.6 b-g 8.9 bc
Sunpride Asgrow 36 d-g 312 d-j 1929 c-i 2278 a-f 75.8 b-g 7.6 f-k
NC 9547 NCSU 51 d-f 377 b-f 1804 d-i 2232 b-f 76.5 b-g 7.7 f-j
FL 47 Asgrow 26 d-g 233 g-j 1963 c-h 2222 c-f 79.0 b-e 8.1 d-h
Equinox Agrisales 29 d-g 317 d-i 1858 c-i 2205 d-f 67.1 j-k 7.5 g-k
SRT 6631 Sunseeds 45 d-g 275 e-j 1882 c-i 2201 d-f 73.0 d-i 7.9 f-i
Solimar Asgrow 57 de 330 c-h 1812 d-i 2199 d-f 65.6 jk 7.5 g-k
FL 7699 GCREC 65 cd 482 ab 1629 h-j 2175 d-f 75.0 b-g 7.0 jk
Suncrest Rogers 55 de 356 b-g 1716 g-i 2128 ef 61.7 k 7.6 f-k
FL 7658 GCREC 102 ab 456 a-c 1565 ij 2125 ef 79.5 b-d 6.9 k
FL 7578 GCREC 38 d-g 281 e-j 1791 e-i 2110 ef 67.0 i-k 7.4 h-k
Sanibel Petoseed 34 d-g 279 e-j 1773 e-i 2085 f 70.2 g-j 7.5 g-k
SRT 6657 Sunseeds 5 g 52 k 1329 j 1386 g 43.9 1 9.8 a
ZMean separation by Duncan's Multiple Range Test, 5% level.
Table 2. Tomato variety results Fall 1997. NFREC, Quincy.
Marketable Yield (25 lb boxes/A) Marketable Average
Entry Source Medium Large Extra Large Total (%) (oz)
Equinox Agrisales 173.5 bce 463 ab 2207 a 2844 a 85.0 a 6.7 c-g
FL 7696 GCREC 152.3 b-e 473 ab 2176 ab 2801 ab 82.3 a-c 6.6 d-g
FL 7763 GCREC 132.9 c-f 377 b-e 2279 a 2789 ab 81.4 a-c 6.9 b-f
XPH 10091 Asgrow 95.5 d-f 347 b-f 2258 a 2701 ab 83.9 ab 7.4 ab
Sanibel Peto 127.6 c-f 372 b-e 2195 ab 2695 ab 78.9 cd 7.1 b-e
XPH 10059 Asgrow 248.9 a 549 a 1897 b-e 2695 ab 84.0 a 6.4 e-g
Captiva Peto 239.5 a 449 a-c 1847 c-e 2535 a-c 79.5 b-d 6.3 fg
P 3260 Rogers 70.7 f 262 ef 2147 a-c 2480 b-d 78.4 cd 7.2 a-d
XPH 10035 Asgrow 90.8 ef 255 ef 2130 a-d 2476 b-d 81.0 c-d 7.3 a-c
NC 9547 NCS 205.6 ab 429 a-d 1822 de 2457 b-d 81.4 a-c 6.5 e-g
Agriset 761 Agrisales 162.7 b-d 394 b-e 1898 b-e 2455 b-d 73.7 e 6.5 e-g
SRT 6629 Sunseeds 116.9 c-f 329 b-f 1849 c-e 2295 cd 73.6 e 7.1 b-e
Suncrest Rogers 120.5 c-f 316 c-f 1843 c-e 2279 cd 76.2 de 7.0 b-e
*SolarSet Asgrow 113.4 c-f 283 ef 1815 de 2212 cd 73.7 e 7.0 b-e
Leading Lady Sunseeds 241.5 a 558 a 1366 f 2165 d 72.0 e 6.2 g
XPH 10047 Asgrow 86.9 ef 292 d-f 1767 e 2146 d 78.8 cd 7.3 a-c
Merced Rogers 70.2 f 214 f 1843 c-e 2127 d 72.0 e 7.7 a
'Mean separation by Duncan's Multiple Range Test, 5% level.
Mechanisms of Host Plant Resistance to Bacterial Wilt
D. O. Chellemi (relocated to USDA-Ft Pierce), P. C. Andersen and F. M. Rhoads
Historically, bacterial wilt has been the most important pest impacting tomato production in
the Gadsden County tomato production region. There is no acceptable cure for bacterial wilt and no
satisfactory disease management strategies and, as a result, numerous farms have been abandoned
over the last 10-15 years due to epidemics of this disease.
Several tomato genotypes have been identified with resistance to bacterial wilt; however, they
have proven to be only suitable to very limited tomato production regions. Similarly, calcium
nutrition has also been shown to affect the expression of bacterial wilt in tomato. The strongest
interaction between calcium nutrition and tomato genotypes appears to be with genotypes with an
intermediate level of resistance to bacterial wilt. Thus, adjustments in soil calcium or soil fertility
regimes may expand the range of acceptable tomato genotypes with a suitable level of resistance.
Expression of resistance to bacterial wilt has been linked to a restriction of bacterial
colonization in xylem tissues within the stem region. The chemical basis for increases or decreases
in the population of bacterial wilt and by which bacterial populations are restricted to the stem regions
are not known. Owing to the dilute nature and chemical simplicity of xylem fluid we feel that xylem
fluid chemistry may play a role in determine resistance. Specifically, amino acids and organic acids
are the major organic constituents of xylem fluid and may play a role in determining titers of bacteria.
The objectives of this study are to: 1) assess the bacterial wilt resistance of a low (Bonny
Best), intermediate (Neptune) and high (Hawaii 7997) tomato cultivars in relation to a soil calcium
and magnesium, and 2) determine if xylem fluid chemistry (or components of xylem fluid chemistry)
are correlated with resistance to bacterial wilt.
Materials and Methods
Experiments were conducted using the cultivars Bonny Best (no resistance), Neptune
(intermediate resistance), and Hawaii 7997 (high resistance). The soil was collected from a tomato
farm in north Florida known to have a history of severe epidemics of bacterial wilt. The soil was heat
pasteurized at 75C, air dried and stored in polyethylene containers prior to use. The three soil
treatments were amended per 1 kg soil as follows: Trt l=control (ammonium phosphate 3.0g, sodium
phosphate 0.5g, potassium sulfate 0.5g); Trt 2=high calcium (components of Trt 1 plus calcium oxide
2.1g); Trt 3=high magnesium (components of Trt 1 plus magnesium oxide 1.5g). Each pot contained
3.8 liters of soil. Lastly, the soil of 50% of the plants of each cultivar/soil combination was inoculated
with Ralstonia solanacearum, the causal agent of bacterial wilt. The experiment was conducted in
The experimental design is a 3x3x2 factorial with tomato cultivar, soil fertility regime and
inoculation/no inoculation as the main factors. Each experimental treatment was replicated 10 times.
Dependent variables include plant height, extent of disease expression (percentage of leaves showing
bacterial wilt symptoms), leaf calcium and magnesium, xylem water potential, titers of R.
solanacearum at the stem base and xylem fluid chemistry. The chemical analysis of xylem fluid
included the quantification of amino acids, organic acids and sugars in xylem fluid.
The pH, calcium and magnesium levels of soils were altered as a function of soil treatment.
The incidence of bacterial wilt was highest on Bonny Best, although it was reduced with the
application of calcium and magnesium. The effects of soil fertility on xylem fluid chemistry exceeded
that of cultivar. Total amino acids and many individual amino acids were influenced by soil
fertilization, with the concentrations of amino acids being reduced in the high calcium and magnesium
treatments Organic acids and sugars were not significantly influenced by soil fertilization regime
or cultivar. Although some preliminary correlations did occur, further work is required to define the
relationship of tomato xylem fluid chemistry and resistance to bacterial wilt.
Benefits to the Industry
There has been little progress in the area of biological or chemical control of bacterial wilt
disease. Economic losses have been incurred in many tomato fields as a result of bacterial wilt
infestation and many tomato production sites had to be abandoned and will be out of production for
the foreseeable future. We have confirmed that there are soil chemistry and plant genotype
components to resistance. Although we found some preliminary differences in xylem fluid chemistry
between genotype/soil fertility regime, additional work is required to make progress concerning the
mechanisms) of resistance.
Portable Evapotranspiration Gauges for Scheduling
Irrigation of Fresh Market Tomatoes
Fred Rhoads, Soil Scientist
There are several procedures available for scheduling irrigation. Among them are
tensiometers, electrical resistance blocks, pan evaporation, and computer models. Tensiometers and
electrical resistance blocks measure soil water at a single point where it can be influenced by clogged
emitters and drip line punctures by pests. If a tensiometer or electrical resistance block is located near
a clogged emitter, over watering may result, whereas measuring soil water near a punctured drip line
could lead to deficit watering. Evaporation from a free water surface integrates many climatic
factors, such as solar radiation, temperature, wind and humidity, that influence evapotranspiration by
crops. A standard evaporation pan is large and inconvenient to install and maintain. Portable
evapotranspiration gauges (PET gauges) are commercially available, inexpensive (- $15), and
convenient to install and maintain ( require less than a pint of water for filling).
The crop coefficient is the ratio of potential evapotranspiration to pan evaporation and
depends upon crop species, growth stage, and available soil moisture. It is difficult to determine the
crop coefficient for tomatoes under field conditions. Since the crop coefficient is proportional to per
cent of ground covered by the crop, we can assume a coefficient of 1.0 when tomato plants are 3 ft
tall because exposed leaf surface on two sides of plant rows would cover the six ft of ground between
rows. Plants taller than 3 ft should be considered to have a crop coefficient of 1.0, whereas, those
less than 3ft tall should be assigned a coefficient equal to plant height in inches divided by 36 inches
(3 ft). Since plant size and water evaporation rate integrate the effects of all variables influencing
plant water use, irrigation scheduling using measurements of these two variables should apply to both
spring and fall grown tomatoes.
The objective of this research was to develop criteria for scheduling irrigation of both spring
and fall tomatoes with measurement of water loss from a portable evapotranspiration gauge and plant
height as independent variables.
MATERIALS AND METHODS
Staked tomatoes ('Agriset 761' for the spring crop and 'Equinox' for the fall crop) were
grown with drip-irrigation under plastic mulch in rows six feet apart to simulate commercial
production practices. Transplanting dates were March 25 and July 31, 1997. Daily irrigation was
applied through drip tubes placed under the mulch. Amount of irrigation for each treatment was
controlled by a time clock. Irrigation treatments were 0, 0.25, 0.50, 0.75, 1.00, 1.25, and 1.50 times
water loss from PET gauges times crop coefficient. Four PET gauges were each placed at row ends
on the mulch film, two at each end of the field, they were not shaded. The crop coefficient was
determined each week from plant height in inches divided by 36, a crop coefficient of 1.0 was used
at all times after plants reached 3 ft tall. Tomatoes were hand harvested and divided into medium,
large, and extra large market grades at each harvest date and total marketable yield was determined.
The experimental design was randomized complete block with four replications.
High rainfall during the spring growing season prevented yield response to irrigation beyond
the 0.25 times PET gauge water loss treatment (Fig. 1.). However, dryer weather in the fall crop
resulted in a significant response between the 0.25 and 0.50 times PET gauge water loss treatments.
The highest yield both seasons was produced with the 0.75 times PET gauge water loss treatment.
Irrigation in excess of that required to produce maximum yield did not reduce yield either season.
Using a crop coefficient in proportion to plant size reduced the potential for fertilizer loss due to
leaching during the early stages of growth each season. This is a more important consideration for
the fall crop because of the higher evaporation demand during the early growth stages in comparison
to the spring crop.
Fig. 1 Tomato Yield Response To
Irrigation Spring and Fall, 1997
0 1/2-ET 1.0-ET 1-1/2-ET
BENEFITS TO INDUSTRY
The data suggest that an inexpensive portable evapotranspiration gauge is adequate for
scheduling irrigation of both spring and fall fresh market tomatoes in north Florida. The cost is much
less than other scheduling devices, tensiometers cost more than $50 each and are needed in greater
number per field than the PET gauges. The main advantage of the PET gauges is that they are not
influenced by local soil water conditions like tensiometers and resistance blocks. Taking the average
of 4 PET gauges per field will reflect plant water use much more accurately than any soil-water
Sap-test Nitrate-N of Fall Fresh Market Tomatoes
Fred Rhoads, Soil Scientist
Nitrogen fertilizer cost for fresh market tomatoes is not very large compared to other
production costs and gross income from a crop. However, excessive N fertilization of commercial
tomato crops is none-the-less wasteful and poses a threat to local water supplies. Water quality
concerns may soon be a major consideration for N fertilization of all crops in Florida. Growers may
one day be penalized for excessive N fertilization of tomatoes. Amounts of N applied beyond the
requirement for maximum yield will no doubt be considered excessive. Over fertilization of tomatoes
with N can be avoided by applying slightly less than plant N requirements and monitoring tissue N
levels during the growing season so that additional N can be applied if a deficiency develops. Plant
tissue analysis has long been used as a tool to manage N fertilization of crops because of the
difficulties encountered in assessing soil N availability. Conventional lab tests are time consuming
and require several days for results to be returned. The recent development of a small battery-
operated nitrate ion meter (Cardy ion meters) makes it possible to quantitatively determine the N
concentration of plant sap on the same day samples are taken.
Recommended ranges for nitrate-N concentration in petiole sap of tomato have been
published based on data from south Florida. The south Florida ranges agree with data from spring
crops of tomato in north Florida. The objective of this project is to determine sufficiency ranges of
petiole-sap nitrate-N of fall grown tomatoes in north Florida.
Materials and Methods
This report is based on data from fall grown tomatoes in 1995 and 1997. The 1996 crop was
destroyed by a seedling disease. Two cultivars were grown, 'Solar Set' in 1995 and 'Equinox' in
1997. Nitrogen rates in four replicates were 0, 60, 120, 180 and 240 lb/acre, all applied preplant as
ammonium nitrate. The fourth leaf from the top of four plants per plot was sampled biweekly in 1995
and weekly in 1997. Samples from individual plots were placed in zip-lock bags in an ice chest and
carried to the lab where the petiole-sap was expressed and placed on nitrate meter electrodes for
nitrate-N determination. Yield and grade were determined from each plot by hand harvesting 3 times
Yields varied between years, with maximum market yield of about 1300 boxes/acre in 1995
and about 2100 boxes/acre in 1997 (Table 1.) The yield difference is attributed to temperature
variation between years, temperature during fruit set was higher in 1995 than in 1997.Yield response
to N was similar between years, because a significant response occurred only between 0 and 60
lb/acre ofN each year. Highest yield in 1995 occurred with 60 lb ofN/acre and in 1997 with 120 lb
of N/acre. Therefore, it appears that 120 lb of N/acre is adequate for fall grown tomatoes. High
temperature could have limited response to N in 1995, while a high rate of mineralization of soil N
could have influenced response to fertilizer N in 1997.
Table 1. Yield response of fall grown tomatoes to N fertilizer rates in 1995 and 1997.
Fertilizer N Rate lb/A
0 756 1706
60 1260 1996
120 1188 2082
180 1332 1940
240 1332 1985
Petiole-sap nitrate-N data shows that N nutrition did not limit yield either year (Fig. 1 and 2),
because petiole-sap nitrate-N content was highest at maximum N fertilization levels each year. A
sufficiency range for fall grown tomatoes (Fig. 3.) was developed from data in Figures 1 and 2 by
averaging values between years for 60 lb ofN/Acre to give the lower sufficiency levels and values
for 120 lb ofN/Acre to give the higher sufficiency levels.
Fig 1. TEmtoes- PiolesiapNtte: 1995
Fig 2 Tiatoes-Pideio-sapNtrat 1997
6 8 10
Sa*ple Dae-\&s AfterTramsuatiit
4 5 6 7 8 9 10
Fig. 3. Tomatoes Petiole-sap Nitrate -
Sufficiency Range For Fall Crop
5 6 7 8 9
Sample Date Weeks After Transplanting
Benefits to Industry
Data from this project suggest that 120 lb of N/Acre is adequate for production of fall grown
tomatoes. A suggested fertilizer management option for fall tomatoes in north Florida is to apply 60
lb of N/Acre preplant, inject 15 lb of N/Acre per week at 5, 6, 7, and 8 weeks after transplanting
while monitoring petiole-sap nitrate-N from 4 to 10 weeks after transplanting, and if petiole-sap
nitrate-N drops below the sufficiency range at 9 and 10 weeks add 15 lb ofN/acre per week for these
two weeks. There was no correlation between yield and petiole-sap nitrate-N after 10 weeks.
Plant Diagnostic Clinic
1997 Interim Report
During the 1997 Season, as of November 20, the North Florida Research and Education
Center- Plant Diagnostic Clinic (NFREC-PDC) processed 607 samples. This will be the fourth
consecutive yearly total increase since the institution of a $15.00 sample fee four years ago. Total
yearly samples for 1996 and 1997 are back up to the pre-sample fee levels. By the end of the year the
total sample count should be an increase of about 4-6% over 1996. Commercial growers,
Homeowners, and Research accounted for 60.0%, 19.9%, and 20.1%, respectively, of the total
number of samples processed. Commercial samples increased by 3% over last year, homeowner
samples decreased 10% over last year and research samples increased 7 % over last year.
Breakdown of Samples by Commodities
Ornamentals and vegetables comprised the bulk of the sample load, 62.6% of the total.
Ornamentals 32.9% (200) and Vegetable 29.7% (180). Agronomic crops 18.8% (114), turf 8.9%
(54), and fruit crops 2.3% (14) comprise the rest of the plant disease samples. Forty-five insect
samples (7.4%) were also processed through the PDC by Dr. R. K. Sprenkel.
Of the 180 vegetable samples received by the clinic, 101 were tomato samples, 81 of those
came from Commercial tomato growers and the remaining 20 from research plots. There were 157
ornamental samples (78.5%) from Commercial Nurseries and 43 ornamental samples (21.5%) from
homeowners. Seventy-six percent of all turf samples came from homeowners while research
accounted for 75% and commercial growers 25% of the agronomic crops.
County No. of Percent of Paid Not Paid Not Charged
Gadsden 249 41.0 91 27 131
NFREC 74 12.2 0 0 74
Escambia 65 10.7 20 0 36
Georgia 37 6.0 15 0 22
Bay 27 4.4 15 6 6
Santa Rosa 26 4.3 13 6 7
Okaloosa 20 3.3 4 10 6
Washington 18 3.0 0 15 3
Arkansas 17 2.8 16 0 1
Leon 16 2.6 7 7 2
Jackson 16 2.6 0 10 6
Madison 13 2.1 1 5 7
Holmes 8 1.3 6 2 0
Alachua 4 0.7 2 0 2
Alabama 4 0.7 0 4 0
Franklin 3 0.5 0 3 0
Calhoun 3 0.5 0 2 1
Gulf 3 0.5 0 1 2
Wakulla 2 0.3 1 1 0
Columbia 1 0.2 0 1 0
St. Lucie 1 0.2 0 1 0
Payment of Samples
Of the 607 samples received by the PDC so far this year, 200 have either been paid for or are
in the process of being billed by the PDC. 100 samples were received and processed without payment.
307 samples were run through the Clinic with no charge. 101 were research samples, 45 insect
samples and 81 commercial tomato grower samples (we receive operating money from the Gadsden
Tomato Growers Association that covers the sample cost). The remaining no-charge samples are
resubmitted samples and samples done as a courtesy.
Use of Microbial Identification System (MIDI)
32 bacterial samples comprising about 95 isolates were run through the MIDI system for
bacterial identification in Dr. Pete Anderson's lab by Kristen Hill. Identification of unknown bacterial
has become more reliable in a much shorter time. We were able to identify an outbreak of a soft
rotting bacterial disease of tomato in the Ft. Pierce area as being caused by Erwinia chrysanthemi,
which apparently is a new report for tomato in Florida.
Vegetable cultural problems encountered were diagnosed by Dr. Steve Olson, ornamental
cultural problems were diagnosed by Dr. Gary Knox, and agronomic problems were diagnosed by
Dr. David Wright. As always, we received complete cooperation from Dr. Gary Simone, Richard
Cullen and Mark Gooch from the PDC in Gainesville with any problem sample we needed help with.
Funds Collected so far this year, Jan 97 to Nov 97, totals 2,890.00 $
Gadsden County Tomato Growers, Account # 727706012