Working Toward Implementation of a Disease Forecasting System for Fresh Market Tomatoes in Northern New Jersey

Working Toward Implementation of a Disease Forecasting System for Fresh Market Tomatoes in Northern New Jersey

Summary

Overview
This project validated a disease forecasting system for Northern New Jersey that allows tomato growers to apply fungicides when they are most-needed, thereby maintaining yields while reducing pesticide applications and costs. The results from the 1999 season comparison reconfirmed those from the two previous years. Even under relatively heavy disease pressure, the TOM-CAST system provided information that allows growers to reduce sprays by about 50 percent compared to a conventional schedule.
Objectives
1.Continue evaluations of tomato disease forecasting as an alternative approach to disease control for fresh market tomato production in northern New Jersey by: conducting field research to specify thresholds for using the TOM-CAST system in northern New Jersey under different seasonal weather conditions; evaluating the impact of reduced fungicide applications with TOM-CAST on post-harvest fruit quality; and expanding the data base for evaluating the economic impact on tomato production of using disease forecasting (TOM-CAST) as an alternative approach to disease control.
2.Continue developing the software required for weather data collection and forecast generation, evaluating weather monitoring equipment, and standardizing equipment use procedures.
3. Continue investigating an electronic meteorological service as an alternative to on-site weather monitoring.
4. Continue grower research demonstrations and explore means for delivery of disease forecasts.
5.Generate the information, including economic data, needed to determine how disease forecasting might best be implemented by individual growers, or provided by organizations such a grower cooperatives or by programs such as Rutgers Vegetable IPM program.
Summary
The use of forecasting for tomato disease control in northern New Jersey has been under evaluation since 1991. The basic premise behind disease forecasting in crop production is that control materials can be applied “as needed” when disease development is likely, rather than by conventional calendar-based scheduling. This approach allows for potential reductions of chemical inputs while maintaining crop quality and yields. The benefit to growers is lower production costs per acre. The environment potentially benefits from reduced pesticide applications during crop production.
Through research trials conducted at the Rutgers Cooperative Extension Snyder Research Farm, 1991-1998, we have validated the TOM-CAST forecast system for use in northern New Jersey. Because weather data is essential for generating the forecasts, weather data from two sources was compared as an adjunct to the disease forecasting research. Our focus was evaluating the feasibility of substituting weather service data for on-site data in the TOM-CAST system. Beginning in 1997, we compared data from an electronic meteorological service with data from on-site weather monitoring equipment used in the research trials and grower demonstrations. The use of a weather service could avoid several problems inherent in on-site monitoring: high cost; failures; maintenance and calibration; accessing and analyzing data.
In 1997 and 1998, Field Monitors™ (portable weather stations from Sensor Instruments, Concord, NH) were set up at six farm sites in a 400 square mile area. The same sites were subscribed to SkyBit, Inc. E-weather Service. Temperature and leaf wetness, the parameters needed for TOM-CAST, were compared for all sites. SkyBit temperature data agreed closely with Field Monitor data at all sites, the average seasonal difference ranging from 0 to 2 degrees F. Differences between SkyBit and Field Monitor leaf wetness were larger and more variable. However, the TOM-CAST model’s daily disease severity values generated from the temperature and leaf wetness data obtained from SkyBit were the same as or greater than those based on Field Monitor data. This resulted in SkyBit weather providing somewhat more conservative forecasts than Field Monitor weather when there was a difference between the forecasts. The more conservative forecasts would have resulted in one to four additional sprays being applied depending on site and year. In no case did SkyBit based forecasts call for fewer sprays than Field Monitor based forecasts.
Because TOM-CAST was not particularly sensitive to the observed differences in weather inputs and because SkyBit forecasts were always more conservative when different from Field Monitor forecasts, SkyBit E-weather was judged to be an adequate alternative to on-site weather monitoring for using TOM-CAST.
In 1999, TOM-CAST forecasts were provided to growers in the Rutgers Tomato IPM Program who subscribed to SkyBit. As a final check on SkyBit data, the comparison with Field Monitor data was repeated at three of the six sites included in the 1997 and 1998 comparison. The sites were those farms that planned to use the TOM-CAST forecast based on SkyBit data during 1999. Rutgers Cooperative Extension set up and maintained the on-site Field Monitor weather stations for purposes of data comparison only.
The results from the 1999 season comparison reconfirmed those from 1997 and 1998: there was close correspondence in temperature data; leaf wetness was variable; SkyBit-based TOM-CAST forecasts resulted in one or two additional sprays for the season. Although SkyBit based forecasts have generally called for more sprays than Field Monitor based forecasts, the total number of sprays applied were less than if a conventional schedule had been followed. In the dry years 1997 and 1999, the number of sprays would have typically been reduced by about 50 percent compared to a conventional schedule. A grower would have made five or six instead of 10 to 13 applications for a crop in the field for 100 days. Each spray eliminated saved time and expense for growers and reduced pesticide inputs to the environment. Assuming use of chlorothalonil, a widely used fungicide, at the highest label rate, 2.25 lb a.i. per acre per spray was eliminated from crop production.
In 1999, TOM-CAST was incorporated into the Rutgers Tomato IPM Program. Information on TOM-CAST and SkyBit and the IPM Program was presented at the North Jersey Vegetable Growers Meeting February 18, 1999. Printed information was also distributed. Research results from the 1998 field trials and weather data comparison project were presented as posters at the 1999 ASHS International Conference in Minneapolis, MN.
Date of Report: 1/03/00