University of Illinois Extension

 


Jim Schuster
,
Extension Educator, Horticulture
Countryside Extension Center

Past Issues

Want to know when a new issue comes out? Sign up for eNews

Botrytis (Gray Mold): A Disease for Many Plants

Botrytis is a fungus. This fungus can attack a wide range of plant parts. It can attack buds, flowers, and leaves, stems and fruit. However, botrytis can be confused with other diseases that cause similar damage. There are more than one species of botrytis and many different strains of each.

Botrytis may attack the foliage of nursery stock stored over winter in damp conditions. Botrytis may attack greenhouse crops where humidity is kept on the high side and then condensation forms at night as temperatures cool off. Free moisture allows botrytis to grow even better. Cool temperatures may slow the disease down but as long as it is moist the disease continues to infect and spread. Botrytis is active from 32 degrees Fahrenheit to about 80 degrees. Hot dry weather shuts the disease down.

Botrytis often lives on dead plant material and from there, spreads into weakened living plant material. It can also infect through wounds or healthy tissue without going though dead or dying tissue. This fungus disease can cause twig blights on stems, buds, flowers, fruit and leaves. It can cause gummosis, fruit rot and damping off. Spores spread from infected tissue to none infected tissue via wind and water. Spores are released with rapidly decreasing or rising humidity levels as well as rain drops hitting the spore structures. Under the right conditions, any disturbance of the air around the spore structures can cause hundreds of thousands of spores to be released. When humidity is high, a thin to thick web of mycelium develops on diseased tissue. This mycelium is grayish in color, hence the name gray mold.

Botrytis produces conidia for adverse conditions such as low moisture and a resting body for the winter. On dead plant material, the disease can over winter as mycelium (fungal growth). Botrytis does not need to attack living plant material since it can live on dead plant material very well as a saprophytic fungus.

There are no known resistant plants. Control of this disease is to control the environment. Keep plants healthy avoiding any stresses such as too wet, too dry, chemical or mechanical injury, and too little or too much fertilizer. Improve air circulation and sunlight. Avoid over head watering. Especially keep open flowers with many petals dry. There are some fungicides to help prevent or reduce leaf, fruit and stem infections.

 

December 2000 - January 2001: Winter Gardening Tips | Plants and Light | Botrytis (Gray Mold): A Disease for Many Plants | Choosng a Christmas Tree Variety | Key Questions for Garden Catalogs

 

Past Issues

Want to know when a new issue comes out? Sign up for eNews