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Tomato Spotted Wilt Virus

Riley France and Peng Tian
Plant Diagnostic Clinic

Originally discovered in Australia in 1915 and found on U.S. soil in the 1970’s, tomato spotted wilt virus (TSWV) is a highly impactful plant disease that can result in both aesthetic damage and significant loss in crop revenue. This Tospovirus has one of the widest known host ranges, with over 1000 susceptible species in 85 families. As it is unable to move on its own, TSWV is primarily transmitted by thrips. Due to the easy spread, broad host range, and economical loss caused by TSWV, it is important to understand how to identify and manage infected crops.

Symptoms

The symptoms of TSWV may vary from different host species or different cultivars within a single host species. The plants frequently appear as stunted, wilting, bronzing with cupping of younger leaves, and chlorotic and necrotic spots with or without a bulls-eye pattern. Symptoms can also manifest on fruit, frequently as ring-shaped chlorotic blotches.

Left, lesions on tomato leaves. Right, yellowing on tomato fruits.
Figure 1: Bronzed lesions on tomato leaves (left) and yellow ringspots on tomato fruits (right). Photo: MU-PDC.

Causal/vector organism

TSWV is transmitted by at least 10 species of thrips which allow the virus to replicate inside their bodies. The adult thrips move the virus from one plant to another while feeding. TSWV infection makes a plant more susceptible to thrips infestation, so the adult thrips will choose to lay their eggs on an infected host. When the eggs hatch and the nymph feeds on virus-infected tissue, it becomes a vector for TSWV and will transmit it for the rest of its life.

Adult and nymph thrips
Figure 2: Adult and nymph thrips with 12-point font for scale. Photo: Sophia Conzemius, Clemson University.

Notable host species

The host range for TSWV is extremely broad. It includes specialty crops such as most Solanaceae plants, which include tomatoes, peppers, and eggplants. It can also cause significant damage to peanut and tobacco crops, and economic damage to ornamentals such as chrysanthemums and ornamental peppers.

Control practices

TSWV is a viral disease and there is no known cure for infected plants. However, good cultural practices can help reduce the damage caused by this disease. First, attempts should be made to resist infection in the first place. This involves planting TSWV-resistant varieties of crops, timing planting to avoid thrips migrations, and treating plants with insecticides that deter feeding. If a plant is confirmed positive for this virus, it’s vital to immediately eradicate it. Weed control is also very important, as they may harbor thrips and allow their population to increase and infect nearby crops. By keeping an eye out for symptoms and practicing appropriate management techniques, growers and gardeners can reduce or prevent TSWV infection of their plants.

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