Fungi Pests That Affect Plants

Botrytis Blight

• Botrytis cinerea fungus causes Botrytis blight, which affects a wide range of annual and perennial herbaceous plants and vegetable crops. The spores spread rapidly during the cool and wet, rainy weather in spring and early summer. The disease is characterized by the appearance of brown spots on all above-ground areas of the plant. With progression, the spots gradually start to decay live plant tissues. Black fungal spores are visible in the decaying areas of plant.

Verticillium Wilt

• Soilborne Verticillium albo-atrum and Verticillium dahlieae fungi cause verticillum wilt in plants. The latter commonly infects a wide range of woody ornamental plants. The serious plant disease commonly infects plant roots during July and August. Symptoms include stunted and yellowing foliage, browning leaves and gradual dieback of branches. Only certain sections -- not the entire plant -- usually are affected. Though plants die gradually, a severe infection can cause sudden death.

Armillaria Root Rot

• Armillaria root rot is also referred to as the shoestring fungal disease. Hundreds of plant species host this fungus. Armillaria mellea, which enters the plant through the roots, causes the disease. The fungus is more likely to infect plants that are weak or are already suffering from stress or other diseases. Symptoms of disease include discoloration and yellowing of foliage. Overall plant growth is stunted and there is branch dieback followed by total death.

Alternaria Leaf Spot

• Alternaria leaf spot leads to the appearance of small lesions on the upper sides of the foliage of infected plants. The spots begin as very small, yellow spots with dark colored margins. As disease progresses, the spots increase in diameter, growing as large as 2 inches, spreading to petioles and stems. Alternaria leaf spot is caused by the Alternaria brassicae and Alternaria brassicicola fungi.