Title: Comparison of foliar fungicide spray combinations for management of diseases of tomato, Fall 1998
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Title: Comparison of foliar fungicide spray combinations for management of diseases of tomato, Fall 1998
Series Title: Comparison of foliar fungicide spray combinations for management of diseases of tomato, Fall 1998
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Creator: Pohronezny, Ken,
Publisher: Everglades Research and Education Center, IFAS, University of Florida
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Bibliographic ID: UF00080910
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Source Institution: University of Florida
Holding Location: University of Florida
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Resource Identifier: oclc - 173682866

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EV-1998-3 b,

Comparison of Foliar Fungicide Spray Combinations for
Management of Diseases of Tomato Fall 1998

Ken Pernezny, Everglades Research and Education Center, IFAS, University of Florida
and Peter J. Stoffella, Indian River Research and Education Center, IFAS, University of
Florida, Ft. Pierce, FL

The major intent of this study was to evaluate selected fungicides for efficacy as
foliar sprays for management of major foliar diseases of fresh-market tomato in Florida.

Materials and Methods

This study took place on the campus of the Indian River Research and Education
Center, Ft Pierce, FL. Tomato plants, cv. Agriset 760, were transplanted to the field on 2
September 1998. Transplants were grown from seeds placed in Styrofoam trays on 12
August Transplants were set into plastic-mulched, non-fumigated, raised beds. Beds
were spaced seven feet apart center to center with the seedlings spaced two feet apart
within the row. Soil was Oldsmar Fine Sand. The air temperature the day of transplanting
ranged from a low of 710 F to a high of 91 F. Seedlings were watered in with Admire
(imidacloprid) (24 fluid ounces per acre) primarily for the control of whiteflies. Plants
used in the guard rows were transplanted at the same time. Methomyl, endosulfan and
oxamyl were sprayed on an as-needed basis for management of foliar and fruit-eating
insects.

An application of 4N-16P-4K fertilizer was broadcast preplant at 685 lbs/A and
incorporated into the bed. Additional 8N-12P-20K fertilizer at a rate of 1369 lbs/A was
split into two bands near shoulders of each bed before covering with plastic mulch.

The experimental design was a randomized complete block with 4 replications of
each of 4 treatments:

1. Quadris, 1.81 ml/gal and Kocide, 9.1 g/gal twice; then Bravo Ultrex, 5.9
g/gal and Kocide, 9.1 g/gal throughout season
2. Quadris, 1.81 ml/gal and Kocide, 9.1 g/gal alternated weekly with Bravo
Ultrex, 5.9 g/gal and Kocide, 9.1 g/gal throughout season
3. Quadris, 1.81 ml/ gal and Kocide, 9.1 g/gal alternated weekly with Dithane,
9.1 g/gal and Kocide, 9.1 g/gal
4. Untreated control

Applications of treatments were made with a hand-held three-gallon garden sprayer with
thorough wetting of foliage to run-off. A particular effort was made to penetrate the plant
canopy and to ensure that fruit surfaces were sufficiently covered. Weekly sprays were
initiated on 17 September and were continued through 3 December.







Plots were rated for disease weekly beginning 29 September using the method of
Pernezny et al (1996). An estimate of the percentage of foliage covered by disease and
foliage lost due to disease were combined into one rating. The proportion of plants with
any visible foliar disease was determined based on a count of the number of plants in a
plot This proportion was multiplied by another representing an estimate of the average
amount of foliar damage per infected plant in order to arrive at a final proportion of
diseased plant material per plot Standard iterative procedures were used to calculate
Area Under the Disease Progress Curve (AUDPC).

Eight plants from the interior of each plot were harvested and graded on 23 and 30
November and 7 December. Fruit were counted, weighed and sorted into several defect
categories, including bacterial spot, target spot, and sunscald.

Data were analyzed by analysis of variance using the Statistical Analysis System
(Cary, NC). Where F-tests indicated a significant difference among an array of three or
more means, means were separated by Duncan's procedure. A series of pre-planned,
single degree-of-freedom orthogonal contrasts were also used for specific comparisons.

Results and Discussion

Bacterial spot, caused by Xanthomonas campestris pv. vesicatoria, was the only
foliar disease of note throughout this experiment. Levels of bacterial spot became
extremely high, especially after tropical storm Mitch passed through in mid-October. In
contrast to most fall crops, target spot, caused by Corynespora cassiicola, did not appear
in this tomato crop.

All fungicides reduced the amount of foliar disease compared to the control, as
measured by season-long AUDPCs (Tables 1 & 2). Quadris plus Kocide treatments
alternated with Bravo plus Kocide were at least the equivalent of maneb plus Kocide
rotated with Quadris and Kocide based on assessments of foliar disease. Quadris plus
Kocide appears to be a viable alternative to the current standard, even in those seasons
when bacterial spot is the major foliar disease threatening Florida's crops.

Using Quadris in two weekly sprays followed the next week with a spray of Bravo
plus Kocide was associated with a statistically improved yield in both number and weight
of marketable fruit (Tables 1 & 2). Direct damage to fruit by X c. pv. vesicatoria, along
with other pathogens, was too low to have any measurable impact on yields. It is likely
that spot reduced the number of fruit set in highly damaged plots.

Literature Cited

Pernezny, K, Datnoff, L. E., Mueller, T., and Collins, J. 1996. Losses in fresh-market
tomato production in Florida due to target spot and bacterial spot and the benefits
of protectant fungicides. Plant Disease 80:559-563.









Table 1. Number, weight and area under the disease progress curve (AUDPC) of marketable fruit,
tomato foliar disease experiment, fall 1998, Ft. Pierce.


Treatment '


Number/plot


Marketable yield b

Weight (lb)/plot


176 a

166 ab

166 ab
142 b


65.5 a
59.2 ab

61.0 ab

51.4 b


1755.1 a


2165.0 bc

2101.9 b

2443.4 c


STreatments were as follows: 1 Quadris (0.1 lb/ai)+ Kocide (2.0 Ib/a) twice alternating with Bravo
(1.1 lb/ai)+ Kocide (2.0 lb/a) once, throughout season; 2 Quadris (0.1 lb/ai)+ Kocide (2.0 lb/a)
alternating weekly with Bravo (1. I lb/ai)+ Kocide (2.0 lb/a); 3 Quadris (0.1 lb/ai)+ Kocide (2.0 lb/a)
alternating weekly with Dithane (2.0 lb/a)+ Kocide (2.0 lb/a); 4 untreated control.

bNumbers are means of 4 replications and represent combined yields from 3 weekly harvests.

Means in columns followed by the same letter are not significantly different by Waller-Duncan's
mean separation test; (P = 0.05).


AUDPC









Table 2. Selected single-degree-of-freedom orthogonal contrasts for fruit number, fruit weight, and
AUDPC for tomato foliar disease experiment, Ft. Pierce, FL, fall 1998"




F-test"

Contrast Marketable no. Marketable weight (lb) AUDPC
Control vs. treated 7.83 8.25 351.49**

Alt. Kocide+Bravo vs. maneb+Kocide 0.203 0.134 1.56

2 Quadris+Kocide vs.1 Quadris +Kocide 0.677 1.95 9.77 *

denotes significant differences) at P = 0.05.
** denotes significant differences) at P = 0.01.

8 Contrast F-tests show that fungicide treatments were associated with larger numbers of fruit and total
marketable weight harvested. Alternating Quadris + Kocide with Bravo + Kocide or maneb + Kocide was
equivalent. Two schedules of Quadris + Kocide alternating with Bravo + Kocide were also equivalent.




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