Comparing the efficacy of fungicide application technologies for disease control in
tomatoes
Principal Investigators:
Erdal Ozkan, Food Ag. & Bio. Engineering (FABE)
Sally Miller, Plant Pathology
Richard Derksen, Agricultural Engineer, USDA-ARS
Mac Reidel, Plant Pathology
Abstract:
Tomato producers rely heavily on fungicides for effective control and management of various diseases.
Proper selection, calibration, operation and use of application equipment has a significant influence on
pesticide performance and on the quality and quantity of crop produced. Limited data is available on
how some of the application variables such as type of spray equipment, type and size of nozzles, travel
speed, spray pressure, nozzle spacing and boom height influence efficacy level of a fungicide. Surveys
of the application practices of growers are hard pressed to find a consensus on the optimum application
practices. Generally, growers will use a combination of spray volume, small droplets, and higher
pressures to provide the good effective coverage with little or no guidance available on the chemical
labels. These approaches, however, may lead to the increase in spray drift, and the effectiveness of
these practices are not necessarily backed up by research data and experiences. Besides a variety of
new technologies available to increase coverage such as air-assist, and electrostatic sprayers, growers
now have a variety of new "low-drift" nozzles (such as Turbo TeeJet, AI Air Induction) choices available
to them. Unfortunately, not much information is available on effectiveness of these new nozzles. such
as ceramic tipped flat fan and hollow cone nozzles.
Objective
The intent of this project was to evaluate disease protection and measure spray deposition provided by
several application techniques that will provide different levels of spray coverage, canopy penetration,
and spray drift and that can be easily adapted to existing vegetable sprayers.
Materials and Methods:
Following is a brief description of materials and procedures that were used in this study:
Crop to be treated: Tomato
Diseases to control: Naturally occurring foliar blights (early blight, Septoria) and fruit rot
(anthracnose)
Fungicide used and rate: Bravo Ultrex; 2 pints/acre, in 25 gal water/acre
Application interval: Fungicides were applied according to accumulation of Disease Severity Values
(DSVs) using the TOMCAST disease forecasting model.
Spray equipment set up:
The six sprayer treatments included application techniques similar to those currently in practice
(traditional broadcast applications using hydraulic nozzles mounted 20 inches apart on the boom), and
treatments using an air-assist sprayer. The sprayer treatments included in the experiment were:
1) Conventional 80 degree flat fan nozzle (XR8002), broadcast configuration, 43 psi.
2) Conventional 80 degree flat fan nozzle (XR8002), broadcast configuration, 79 psi.
3) Ceramic disc-core hollow cone nozzle (D6-23), broadcast configuration, 37 psi.
4) Ceramic disc-core hollow cone nozzle (D2-23), broadcast configuration, 240 psi.
5) TurboTeeJet 110 degree flat fan drift reduction nozzle (TT110015), broadcast configuration., 71
psi.
6) Myers air-assist row crop sprayer (40 mph air stream), equipped with XR11005 flat fan nozzles
in broadcast configuration (12 in. nozzle spacing), 28 psi.
Procedure:
This study was conducted at the Snyder Farm, OARDC in Wooster, in a replicated, randomized
complete block design with four replications. In addition to the plots associated with the treatments listed
above, there were four check plots receiving no fungicides (total of 28 plots). Each plot consisted of
three rows of tomatoes, each 20 ft long, with 1 ft between plants. Rows were placed 5 ft on center, and
each set of three treatment rows was alternated with a single untreated border row.
Fungal foliar diseases (early blight, Septoria) and fruit rot (anthracnose) moved into the plot naturally.
Approximately mid-season, Bravo Ultrex fungicide was applied on a 7-10 day schedule according to the
accumulation of DSVs (Disease Severity Values) in the TOMCAST model. Six spray applications were
made between 2 July and 20 August 1998. Check plots did not receive the fungicides or copper
treatments.
A fluorescent tracer (Tinopal) was added in the spray mixture to evaluate foliar spray deposits. Each
sprayer treated four, 3-row plots. Four leaves at top and four leaves at middle elevations were taken
from each of the 3 plants in center row. The spray coverages both on upper and under side surfaces of
leaf samples were evaluated using an image analysis system. With a separate set of spraying
treatments on the same plots, effectiveness of adding surfactants which improve spreading
characteristics of the spray was investigated. For this, X-77 a spreader surfactant, was added to the
spray mixture at a concentration of 0.1%.
Tomatoes were evaluated for disease control relative to the untreated check plots three times
throughout the growing season based on foliar disease. Foliage was rated for lesions and defoliation
according to the Horsfall-Baratt rating scheme (a rating of 1 indicating the least amount of disease
observed, while a rating of 12 indicating the highest amount of disease observed). Fruit at ripe stage
was harvested from the center 5-feet section of the center row of each plot. Samples were evaluated for
anthracnose, and yield was determined. Insects and weeds in the plots were managed by using
standard management practices.
Summary of Results:
- It is more difficult to treat undersides of leaves than upper sides of leaves
- The air-assisted sprayer provided significantly better coverage on underside of leaves than other
sprayers and nozzles.
- Regardless of the nozzle type used, coverage on leaves lower in the canopy was significantly less
with conventional sprayer setup than with the air-assisted sprayer.
- Although there were differences in spray coverage from different treatments, this did not correlate
with the control of all foliar diseases.
- Small differences were observed in disease control provided by different nozzles.
- The experiment summarized in this report will be repeated in 1999.
Extension Program Implementation:
Results of this study was presented to Tomato growers at several county-based meetings and at a field
day held in OARDC Vegetable Crops Branch in Freemont, and to OSUE Extension Agents at the
1999 Pesticide Update In service. A handout was prepared and distributed to the agents at this In
service. The data will be distributed to interested Extension Specialists in other states via e-mail.
For further information contact Erdal Oskan, Professor, Food, Agriculture and Biological Engineering or the Ohio IPM Office.
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