HPIPM:Potato Botrytis Vine Rot, Gray Mold

Taxonomy

Domain	Eukarya
Kingdom	Fungi
Phylum	Ascomycota
Subphylum	Pezizomycotina
Class	Leotiomycetes
Subclass	Leotiomycetidae
Order	Helotiales
Family	Sclerotiniaceae
Genus	Botrytis

Scientific Name

Botrytis cinerea

Scientific Name Synonyms

Botryotinia fuckeliana

Botrytis vulgaris

Sclerotinia fuckeliana

Common Name

gray mold

Author: Howard F. Schwartz and David H. Gent

Identification and Life Cycle

Gray mold is a disease of potato foliage and tubers caused by the fungus Botrytis cinerea. The fungus has a very broad host range that includes many other vegetables, including tomato, pepper, dry bean, and onion. The disease cycle begins when wind or water deposits spores (ascospores or conidia) onto a leaf, where the fungus directly penetrates host tissue and infects the plant. Cool, wet weather and lush crop canopies greatly increase infection, especially on senescing or previously diseased plant parts. Heavy dew, fog, and frequent rain or irrigation increase gray mold severity. The pathogen may survive between potato crops in crop debris and soil as spores (conidia) or dormant resting structures (sclerotia), pathogenically on other plants, or saprophytically on organic matter.

Plant Response and Damage

Gray mold is most severe when temperatures are mild to moderate and moisture is abundant; warm, dry weather suppresses disease development. Disease symptoms are generally first observed on flowers as gray, fuzzy growth. As flowers drop into the foliage, lesion may develop on leaves, appearing as tan, wedge-shaped lesions largely confined by plant veins. Stems often develop a brown, slimy rot when leaf infections progress through petioles. Tuber infections are rare, but can occur when tubers are wounded during harvest and handling operations. Affected tubers have a wrinkled skin with a soft, wet rot that can extend deep into tubers. A dry rot can develop with tuber infections, but other tuber rotting fungi and bacteria can also invade gray mold lesions and cause a soft rot. The disease is generally not economically important in the High Plains, but can mask other diseases and make accurate disease diagnosis difficult.

Biological Control

No biological control practices have been developed for gray mold of potato, but biological control of the gray mold pathogen on other crops has been successful with various bacteria, yeast, and beneficial fungi.

Cultural Control

Avoid excessive irrigation and fertilization that can lead to dense, lush canopies favorable for gray mold development. Avoid irrigation during rainy weather that can prolong periods of leaf wetness.

Chemical Control

Due to constantly changing labels, laws and regulations, the sponsors of this web site assume no liability for the suggested use of any chemicals noted in the management section. Contact your local pest management personnel for current information on labeled pesticides that can be used for the intended plant disease, insect pest or weed.