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Integrated Management of Potato and Tomato Late Blight in New York State 1997

Project Leaders: Abby Seaman, John Mishanec, C. Albers, B. Caldwell, A. Gabriel, T. Gallagher, C. MacNeil, D. Moyer, M. Orfanedes, C. Tillinghast, J. van der Heide

Objectives:

1. Reduce the amount of overwintering inoculum from fields and cull piles.

2. Educate growers about the importance of using certified seed and of careful evaluation of seed quality.

3. Alert growers as to the proper time to begin protective fungicide sprays and provide information to help determine appropriate spray intervals based on weather favorability and inoculum levels.

4. Quickly alert the industry if late blight is detected in New York or surrounding states.

5. Evaluate the effectiveness of the communication network and the usefulness of recommendations on sanitation and spray schedules.

6. Compare three forecasting models on Long Island.

Results:

Growers subscribing to the Weekly Vegetable Update and the Pestminder were surveyed about how they used the disease forecasting and late blight incidence updates included in these publications. Forty-seven potato and/or tomato growers returned surveys, representing 1,670 acres of potatoes and 505 acres of tomatoes. Most growers reported using each type of information for more than one decision. Suggestions for improving the late blight network included a request for more weather monitoring locations, the need for more specificity about the location of late blight outbreaks, and a request for information about the history of fields with late blight outbreaks.

The comparison of forecasting models revealed that WISDOM is the most conservative of the three, recommending 13 fungicide applications over the season, while the Ullrich-Schrodter and Winstel programs recommended 10 and 7 sprays, respectively. The inability to account for untreated foliage during periods of rapid growth is a drawback of all the models.