Spotted wilt is caused by the tomato spotted wilt virus (TSWV), and causes a reduction in the amount and quality of fruit. It was first described in 1915 in Southern Australia, and is now found worldwide. It is found everywhere in the United States where tomatoes are grown. It is a very destructive disease. One hundred sixty-three plant species are affected by TSWV, including tomato, tobacco, potato, lettuce, pepper, eggplant, cauliflower, celery, endive, spinach, pea, dahlia, sweet pea, zinnia, nasturtium, poppy, lily, petunia, orchid, chrysanthemum, aster, salpiglossis, cineraria, gloxinia, bindweed, nettle, mallow, and chickweed. It is an especially bad problem on greenhouse ornamentals.

Symptoms. Spots are seen during the flowering or fruiting stage. Small orange-colored flecks appear on middle or lower leaves or on other green parts of the plant. As leaves become more covered with flecks, they turn brown, droop, and die. One half of the plant may be more affected than the other half. The plant may look as if it has a vascular wilt. The entire plant is usually dwarfed. Growing tips of the branches may die; the branches may be streaked.

On green fruit, slightly raised yellow spots develop. These spots are up to 1/2″ in diameter. The spots usually have a distinct target appearance, with rings of yellow or light brown, alternating with green, then later pink or red. The target-like appearance becomes more prominent as the fruit ripens. Fruit spots are very distinctive and are usually enough to identify this disease. The fruit spots may be anywhere on the fruit.

Similar diseases. Similar diseases exhibit somewhat different symptoms. Early blight fruit spots are generally at the stem end of the fruit. They are large and brown. These spots often crack. The leaf symptoms for early blight are very different. Vascular wilts do not have the orange flecks on the leaves or the target-like spots on the fruits.

Thrips transmit TSWV. However, thrips control is no always considered useful. This virus is spread in a persistent manner by nine species of thrips. They acquire TSWV as larvae and transmit it as adults. See the current recommendations for the control of the thrips. Reflective mulches may reduce, but not eliminate, losses.

Be aware of nearby plants than can serve as hosts for the virus. It is important to control weeds, especially chickweed and bindweed, as these may serve as a place for the virus to overwinter. In the spring, these weeds become a source of the virus. Do not grow tomatoes near lilies or dahlias. There are no resistant cultivars. In the greenhouse, do not plant tomatoes in the same greenhouse as ornamentals.

References.

• Sherf, A.F. and A. A. MacNab. 1986. Vegetable Disease and Their Control. John Wiley and Sons, New York
• Zitter, T.A. 1991. Tomato Spotted Wilt in Compendium of Tomato Diseases. APS Press. St. Paul, MN. p.40. J.B.Jones, J. P. Jones, R.E. Stall, T. A. Zitter, eds.

By: Pam Mercure, IPM Program Assistant, University of Connecticut, 1998

Reviewed by: T. Jude Boucher, IPM, University of Connecticut. 2012

This information was developed for conditions in the Northeast. Use in other geographical areas may be inappropriate.

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