Verticillium disease is a wilt is a soil-borne fungus caused by six species of the Verticillium genus: Verticillium albo-atrum, V. dahliae, V. longisporum, V. nubilum, V. theobromae, and V. tricorpus. Over 350 host plants are susceptible to Verticillium wilt including members of the Solanaceous family (tomatoes, potatoes, peppers, and eggplant), the Brassica family (Brussel sprouts, cabbage, and cauliflower), Cucurbitae (cucumber and pumpkin), Fragaria (strawberry), and many fruit and ornamental trees.
The Verticillium fungus lives from year to year in the soil and occurs throughout the Northeast. The basic life cycle is similar across all species of Verticillium although V. albo-atrum forms mycelium, V. dahliae forms microsclerotia, V. nubilum forms chlamydospores, V. tricorpus forms all three. These resting structures can survive in the soil anywhere from 4-15 years depending on conditions such as temperature, hydration, and non-host crops.
Life Cycle When the roots of a host crop come near the resting structures the root exudate (chemically diverse secretions) triggers the germination of the threadlike fungal structures and they grow toward the plant. Verticillium is a vascular disease and generally requires an opening in the root system to access the vascular structure of the plant. Verticillium produce conidia that are released into the plant xylem tissue and colonize the plant in as little as 24 hours. Verticillium is a cool-weather disease than grows best in the 70-85°F range.
Symptoms of the disease include wilting, mottling or chlorosis of the leaves, and discoloration of the vascular tissue in the roots and lower stems. Wilting may occur on only one side of a plant.
Heavily infected plants can succumb quickly and if not removed can release the survival structures into the nearby environment where they will wait for the next host to repeat the cycle. The disease can spread from root to root and through infected seed (up to 13 months). It is rarely spread aboveground to healthy plants. Insects that feed by cutting into a plant such as leaf hoppers and aphids can vector the disease from plant to plant.
Control Once plants are infected there is no control. Plant disease resistant plants when available or avoid planting susceptible species in an area where the disease is known to have existed. Remove and bag or destroy any infected plant tissue, do not compost as most home garden compost piles do not get hot enough to kill the structures.
Despite good cultural practices, pests and diseases at times may appear. Chemical control should be used only after all other methods have failed.
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UConn Home and Garden Education Center, 2017
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