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Cox Program: Tree and Small Fruit Extension Resource Blog

School of Integrative Plant Sciences | Plant Pathology and Plant-Microbe Biology Section

Weekly Apple Scab Disease Forecasting. Week of 5-24-23

Capitol District Recommendation: With the coming rain event this week, there is a 25% ascospore event predicted on May 24, make sure you make a single site fungicide application. Some good options include Aprovia, Tesaris, Merivon or Cevya (if you also have rust). This last spore ejection event most likely will discharge the remaining spores.

Champlain Recommendation: With the coming rain event this week, there is a 50% ascospore event predicted on May 24, make sure you make a single site fungicide application covered. Some good options include Aprovia, Tesaris, Merivon or Cevya (if you also have rust). Since only 84% of ascospores should be discharged by this event, there will likely be another infection event with the next rain event.

Hudson Valley, Long Island and Finger Lakes Recommendation: All ascospores have essentially been released, so primary apple scab season is over. Maintained desired fungicide coverage in 14-21 day intervals. Monitor for any upcoming long leaf wetness events predicted. Make sure to make a single sire application before they occur, otherwise, maintain desired fungicide coverage.

Niagara County: No risk for fire blight or apple scab this week. Maintain desired fungicide coverage. If you are considering making a cover application, some good options include Thea, Howler, or Double Nickel.

Wayne County Recommendation: There is a current low risk of infection with 7% of ascospores being released. This might be a good week to apply a cover spray application. To reduce risk of phytotoxicity, maybe avoid captan with regulaid, instead consider Howler, Thea, or Double Nickel LC. As for fire blight, there is a low no risk of infection for the week with the highest EIP and TRV values being 17 and 43.

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