Key Features
- Small, gray, dead spots
- Blight of leaves and petals
- Gray/tan tufts of spores
Symptoms
Botrytis blight (Gray mold), caused by Botrytis species, often occur in heavily irrigated landscapes. Botrytis is capable of causing leaf, stem, flower and fruit blights on a wide range of hosts. Leaf and stem spots begin as small, wet-looking spots that enlarge and cause wilting and blighting. Gray-brown tufts of spores can often be found on flowers or near the base of infected plants.
Biology
Spores are splash and wind-dispersed to host plants, though infection and disease development can only occur in the presence of standing water or greater than 80% relative humidity. Infection commonly begins on flowers or fallen petals and spread into leaves, stems, and crowns of plants. Successful infection followed by dry conditions in the canopy may result in spots or specks but is not likely to progress to wilting or blighting. Spores and infected tissue that drops from the plant are capable of spreading the disease to healthy tissues and nearby plants, as well as increasing the amount of disease surviving in the soil.
Management Recommendations
Water landscapes in the late morning so plants have ample time to dry. Drip irrigation will limit spore dispersal and prevent standing water on plant surfaces. Choosing a proper planting site and plant spacing will increase the plant's natural defense against the Botrytis. Collect and destroy all plant debris that may harbor the pathogen. Do not compost Botrytis infected plants or plant material. Several fungicides are labeled for homeowner use against Botrytis. Always read and follow the product label. Products may damage plants not included on the label.
Effective Pesticides
Active Ingredients include: Captan, Chlorothalonil, Copper salts, Myclobutanil, Thiophanate-methyl
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