The Bug Box: Gray mold

University of Florida

University of Maryland

This bug is creeping around your property. He may be friend or foe.

Name: Botrytis cinerea

Alias: Gray mold. This is one of the most common fruit rots of strawberries. The disease is caused by a fungus. If you look closely at strawberries in most grocery stores, you can usually spot this fungus in at least one of the packages. It has a gray appearance and when it starts to grow in size it begins to resemble mouse fur. This phase can occur rapidly under humid conditions. In the field, it can cause serious yield reductions. The disease can start early in the season as a blossom blight. As it continues to grow, it attacks buds and other blossoms as well as green and ripe strawberries. It may progress down the stem, killing stems and leaves. The fungus can survive as a saprophyte in dead organic matter. When conditions are right, the fungus grows and sporulates. The fungal spores, which occur when the gray mold is visible, are carried by wind or splashing water and are deposited on susceptible tissue. These spores are able to germinate in water within a few hours and enter directly into the fruit or flower. Once the tissue is infected, the fungus usually produces secondary infection spores and the cycle can be continuous throughout the growing season under the proper conditions. The fungus overwinters in dead plant tissue as dormant mycelium or sclerotia (hardened mats of mycelium).

Crimes: This disease is difficult to control under humid conditions. There have been reports of 50 percent losses under favorable conditions for fungal growth.

Redeeming Qualities: None known.

Sentence: This fungus loves high humidity and cool temperatures. Any cultural practice that minimizes these parameters will help reduce the occurrence of gray mold. There are fungicides available that will help control the spread of the disease.

For more information on dangerous and beneficial bugs, call agent Wayne Jones at the Bonneville County Extension Office at 208-529-1390.