Botrytis blight outbreaks expected due to weather

Clouds and rain favor Botrytis blight, but cultural practices and correct fungicides will help until the sun shines.

By Tom Dudek, Michigan State University Extension

The forecast for the next five days indicates cloudy, cool and rainy weather conditions. These low light, humid conditions combined with many of our greenhouse floral crops being at or near full flower in area greenhouses can lead to Botrytis blight outbreaks. Crops like geraniums, Gerbera daisy, petunias, fuschia and calibrachoa, to name a few, can be especially vulnerable to this disease now since they have a full flower canopy and most greenhouses are soon to be filled to the maximum allowable space.
 
Remember that Botrytis is a fungal disease that can cause leaf spots, petiole blighting and stem cankers on many different annuals and perennials. It will produce large masses of “fuzzy looking” spores that are most often called “gray mold.” These spores or conidia will be spread on wind currents and can readily travel from infected to uninfected plants in that manner. The spores can survive for upwards of 21 to 24 days before they germinate on a plant.
 
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