Greenhouse - Botrytis

Botrytis gray mold is the most common disease that greenhouse growers face. The following is a short article on the subject.

Botrytis cinerea (gray mold) can be very troublesome this time of year during periods of cool, overcast weather, especially in humid propagating areas. Fungal spores in the greenhouse germinate under conditions of high humidity when there is a film of water on the leaves for several hours. Good sanitation practices, increasing air circulation, and reducing humidity are crucial in preventing this disease.

Cultural Controls: Water plants early in the day, avoid overhead watering, remove plant debris from the greenhouse, use horizontal air flow (HAF) fans, and space plants properly. The vent and heat method can help to remove nighttime humidity. Vent at sunset to remove warm, moist air and bring in cool, dry air. The outside air will absorb moisture as it is heated.

Chemical Controls: Decree, Cleary’s 3336, Chipco 26019, Cleary’s Protect TO, Medallion, Phyton 27, Triact 70 and Spectro 90

From the February 17, 2006 edition of the Greenhouse TPM/IPM Weekly Report by the University of Maryland Cooperative Extension.