Botrytis on plants and in trash cans?
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
Cool, dark, wet weather when plants are in full flower can lead to a massive Botrytis attack. However, there are things you can do to reduce the severity of the problem. The most effective way to prevent Botrytis is to keep the foliage and flowers dry. Make sure you have plenty of air movement, water only when absolutely necessary and then only early in the day. Heat and vent morning and evening for at least one-half hour or more.
Botrytis is not a strong pathogen; it attacks petals and senescing or damaged plant tissue so sanitation is critical. However, too often growers do a good job of cleaning plants and then put the debris in a trash can and leave it in the house. Botrytis continues to develop and produce spores even in trash cans so have your employees put plant debris in plastic bags, seal them right at the bench and then take them out of the house. Don’t put this material on top of your compost pile – the spores can be moved by the wind or your fans right back into the range.
Dr. Mary Hausbeck, MSU greenhouse plant pathologist, suggests using chlorothalonil (Daconil), fenhexamid (Decree) or iprodione (Chipco 26019) for heavy attacks. For less disease pressure: trifloxystrobin (Compass), azoxystrobin (Heritage) or mancozeb (Dithane).