![]() Away from the coast, gray mold generally is a problem only during the late fall through early spring rainy season. In greenhouses or outdoors in coastal areas Botrytis and Botryotinia diseases can be a problem almost any time of year. Spores germinate and produce new infections only after plants have been continuously wet for 6 or more consecutive hours or when relative humidity has been higher than about 90% for 6 or more hours. Landscape hosts include azalea, bird of paradise, cacti, coast redwood, fuchsia, giant sequoia, hydrangea, rhododendron, and rose. Succulent tissue of most plants is susceptible to Botrytis blight. Infected fruit, leaves, petals, and succulent stems become dark, soft, and wilted and die. These infected spots turn brown and appear water soaked. Identificationĭisease often presents initially as tiny, almost translucent spots. Various Botrytis and Botryotinia species cause gray mold, most commonly Botrytis cinerea. ![]() The tiny, stalked spore-forming structures give rotted tissues a fuzzy appearance when viewed with the naked eye. Gray mold is named for the brown, gray, or tan fungal spores that develop on infected tissue when conditions are humid or moist. How to Manage Pests Pests in Gardens and Landscapesīotrytis blight, or gray mold- Botrytis and Botryotinia spp. Be sure to read and follow all label instructions of the fungicide that you select to insure that you use the fungicide in the safest and most effective manner possible.UC IPM Home > Homes, Gardens, Landscapes, and Turf > Diseases However, Botrytis may develop resistance to these products (particularly iprodione). Fungicides such as chlorothalonil, iprodione and mancozeb can be used to prevent infections. Reduce humidity around plants and germinate seedlings under warm, relatively dry conditions. Avoid wounding plants mechanically, or chemically by overfertilization or misuse of pesticide sprays. How do I avoid problems with gray mold in the future? Remove dead or dying tissue from plants and the soil surface. Disinfest pruning tools between cuts by dipping them for at least 30 seconds in a 10% bleach solution or alcohol (spray disinfectants that contain at least 70% alcohol can also be used). Prune diseased branches four to six inches below the infection leaving a clean cut. How do I save a plant with gray mold? Promptly remove diseased leaves and flowers. In order to infect tough tissues such as healthy leaves, Botrytis spores require an external food source such as nutrients leaking from wounds or dying tissues such as old flower petals. Botrytis spores rapidly die when dried, and most readily infect delicate tissues such as petals. Botrytis produces large numbers of dusty, gray reproductive spores that are spread by wind or splashing water. Where does gray mold come from? Gray mold is caused by the fungus Botrytis cinerea, which survives on dead plant tissue as dark brown to black, multi-celled structures called sclerotia, and as thick, dark-walled, single-celled spores called chlamydospores. ![]() Botrytis can also cause stem cankers (localized sunken areas) that may eventually enlarge to girdle the stem. On leaves, Botrytis causes irregularly-shaped necrotic (dead) areas that may have a bull’s-eye pattern. ![]() On plants such as tulips, crocus, and daffodils, gray mold may spread from flowers into the bulbs leading to bulb decay. Early infections may prevent flowers from opening. What does gray mold look like? Gray mold causes brown spots on petals that enlarge, killing the petals, and eventually the rest of the flower. Gray mold is a particularly serious problem on flowering plants and those plants grown in greenhouses. What is gray mold? Gray mold (or Botrytis blight) is a common and often serious fungal disease that can affect plants of all kinds. Jeffory Schraufnagel*, Milwaukee Area Technical College, Brian Hudelson, UW-Madison Plant Pathology Severe gray mold can prevent rose blossoms from developing properly. ![]()
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