Problem Identifier Unit Screen//v.w/ RR Template

Problem Identifier Unit Screen//v.w/ RR Template Gray Mold

Problem
New shoots wilt and die. The bases of the wilted stems are brownish black and rotted. Young flower buds turn black and wither. Older buds and open flowers turn soft and brown, and develop a gray or brown fuzzy covering in wet weather. This fuzzy growth, which may develop on all infected plant parts, is very distinctive. Its presence can be used to help distinguish this disease from Phytophthora (see Phytophthora Blight) with which it is often confused. Irregular brown lesions or patches form on the leaves. In severe cases, the plant base and roots may decay.

Analysis
This common disease of peonies is caused by a fungus (Botrytis paeoniae or B. cinerea). Gray mold is most serious in the wet, cool conditions of early spring. Fungal growth on the stems, leaves, and flowers causes spotting, blackening, and decay. The fuzzy growth that forms on infected tissue is composed of millions of tiny spores. This fungus is spread by wind, splashing rain or water, or contaminated plants, soil, and tools. The fungus forms small black pellets that survive in plant debris and in the soil for many years.

Solution
Remove and destroy all decayed or wilting plant parts. Clean up plant debris during the growing season and again in the fall. In the spring, spray emerging shoots with a fungicide containing mancozeb or zineb. Repeat the spray 2 more times at intervals of 5 to 10 days. Respray if the weather continues favorable for disease.

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