Practical IPM for Tomato Diseases
Staking, mulching, and a weather-based forecasting system reduce reliance on pesticides
Fresh-market tomatoes are an important part of the livelihood of growers such as the 50-plus roadside marketers on Long Island. Recent disease problems in Long Island tomato fields spurred Margaret Tuttle McGrath, plant pathologist at the Cornell laboratory in Riverhead, and Dale Moyer, Cooperative Extension educator in Suffolk County, to evaluate the latest in applicable IPM techniques.
Several common diseases of tomato in New York State are caused by organisms that can survive in the soil, including early blight, Rhizoctonia fruit rot, and anthracnose. While long-term rotation is a proven IPM method for managing soilborne diseases, it is often impractical.
The approach taken by McGrath and Moyer was 1) to compare a
weather-based forecasting system that has become the standard for
disease control in processed tomatoes in the Midwest ("TOM-CAST") to the
standard weekly spray program, and 2) to evaluate staking and plastic
mulch as disease management tools.
TOM-CAST proved to be a great means of reducing pesticide use. The seven sprays called for by TOM-CAST in the 1997 season provided sufficient control of powdery mildew and early blight to get a tomato yield as good as that produced with the standard weekly spray program, in which twelve sprays were applied. Saving five sprays means cutting pesticide inputs by 12.5 pounds per acre. This obvious environmental benefit also saves $141.50 per acre for each grower.
Staking tomatoes to keep them off the ground and using raised beds with black plastic mulch were also found to be beneficial additions to a disease control regimen. These practices reduce the opportunities for disease-causing organisms in the soil to get to the fruit. Tomatoes grown using both of these methods produced significantly more marketable fruit than those grown on bare ground. Any concern about the cost of these methods was allayed by a look at the net gain. While the stakes, plastic, and attendant labor costs came to $800-1,000 per acre, the value of the yield gain attributable to them was $3,911 per acre.