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Less Pesticide, More Weather Data Spell Control of Apple Disease

Weather-based model enables growers to reduce treatments for flyspeck

photo of flyspeck on an apple
Apple disfigured by flyspeck. Photo by D. Rosenberger

Two seasons of work by Cornell plant pathologist David Rosenberger have given apple growers assurance that the disease called flyspeck may be controlled with one fewer fungicide spray per orchard per season than has previously been applied. Flyspeck is a common summer disease of apples in the Northeast. Its name is a good descriptor of the damage it causes. Though the damage doesn’t go beyond the skin of the fruit, the disfigurement can be enough to make affected apples unmarketable as fresh fruit. Other IPM methods for managing flyspeck include pruning tree branches, thinning fruit, and removing brambles and other host plants, when practical.

Rosenberger worked with fruit extension educators Warren Smith and Mike Fargione (Ulster County) and Kevin Iungerman (Saratoga County). They tested a New York Flyspeck Timing Model in nine orchards scattered across the Hudson Valley, Champlain Valley, and Saratoga production regions.

The model uses weather data such as hours of leaf wetness to determine when infection conditions are present and when fungicide treatments are needed. Even though 1998 was an exceptionally wet year and thus conducive to the development of fungal diseases like flyspeck, the model provided adequate information for disease control in seven of eight test plots. A more conservative spray program may still be needed in areas where disease levels are exceptionally high.