# Fungus on Mint Leaves
Mint is a hardy, potentially invasive perennial herb that can grow up to 3 feet tall. According to Utah State University, mint tolerates temperatures as low as minus 20 degrees Fahrenheit. Although mints prefer full sun and moist soil, excess moisture can promote fungal disease.
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Types
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Powdery mildew develops in warm, humid conditions, and leaf rust occurs on cool, wet mint leaves. Rhizoctonia web blight develops in dry soil in crowded, humid environments. According to the U.S. Department of Agriculture Integrated Pest Management Centers, peppermint plants are especially susceptible to verticillium wilt.
Effects
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Powdery mildew causes a powdery white growth on the upper and lower sides of mint leaves, while leaf rust causes leaf loss and reddish brown spots on the undersides of leaves. The weblike rhizoctonia fungus causes rapid leaf collapse. Verticillium wilt symptoms include stunted, twisted leaves and plant yellowing from the inside out.
Solutions
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To prevent the spread of fungal disease, destroy infested plants, disinfect gardening tools and pots and avoid overwatering and crowding. Although no chemical control exists for verticillium wilt, you can grow wilt-resistant mint varieties, such as Murray Mitcham peppermint. In early spring, apply clorothalanil to prevent rust infestation.
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