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Refining IPM Procedures for Fresh-Market Tomatoes

Weather- and disease-forecasting models take on tomato diseases

IPM procedures for tomatoes used in frozen and canned products have been in place since the 1980s, but they need to be tailored to suit tomatoes that are sold fresh. One particular area of need is disease forecasting. A weather-based program called TOMCAST has been used to forecast early blight and powdery mildew, but it does not forecast late blight. For this, another program called BLITECAST is needed.

In the 1998 growing season Professors Bob Seem and Helene Dillard, plant pathologists at the Experiment Station in Geneva, evaluated late blight management using a form of BLITECAST that had been adapted to work with a weather- forecasting product called E-Weather. Demonstration sites were located on three farms in western New York and at the Experiment Station in Geneva.

Unfortunately, E-Weather did not prove to be reliable under the test conditions set up by Seem and Dillard. No late blight was observed at any of the locations being assessed, yet the forecast system made consistent warnings of infection for all four locations. Comparisons to monitored weather data showed that the E-Weather forecasts consistently overestimated periods of high humidity and leaf wetness. Additional work on the weather and the disease-forecasting models must be completed before this system can be considered for commercial implementation.

The same three farm fields used by Seem and Dillard for their late blight forecasting were used by IPM Extension Educator Abby Seaman to demonstrate TOMCAST as a tool for managing three other diseases: early blight, Septoria leaf spot, and anthracnose. IPM-managed plots were compared to grower-managed plots at all three farms.

Fruit quality at harvest was equally good in the IPM and the grower-managed plots at the Ontario County and Niagara County sites. It was unacceptable in both plots at the Chemung County site. The moist conditions at that site may have contributed to the steady development of an early blight infection that occurred in late July and August.

Seaman believes that TOMCAST has the potential to significantly decrease fungicide use in tomatoes, especially compared to a conventional weekly spray schedule. But there have been obstacles to proving this. Late blight and bacterial canker, diseases that are not managed by TOMCAST, have frequently prevented Seaman from demonstrating the full season savings in fungicide applications that is possible with TOMCAST. What to do? Knock down one of these obstacles. According to Seaman, "Late blight, once it appears, is beyond the growers’ control, but bacterial canker management is a frontier worth exploring. It will be the focus of next year’s demonstrations."

Cooperators on the Seem and Dillard project and on Seaman’s project were Extension Educators Brian Caldwell, Carol MacNeil, and Mike Orfanedes; Barbara Christ, of Penn State; Joseph Russo, of ZedX, Inc.; and Cornell faculty members Mike Hoffmann, Meg McGrath, and Tom Zitter.