Tomato spotted wilt virus (TSWV) is estimated to cause more than $1 billion in damage to crops throughout the world annually.

As its name implies, TSWV was originally observed in tomatoes. But in recent years, there have been reports of a sharp increase in TSWV attacking not only tomatoes, but also peppers and peanuts, particularly in Florida, Georgia and North Carolina. Last year Virginia saw a tremendous increase in TSWV problems in potatoes.

In May 2002, Agricultural Research Service plant pathologist Scott T. Adkins, in conjunction with the University of Florida (UF), began to study crop damage caused by this virus in the tomato production areas of northwest Florida, just west of Tallahassee. He and his team observed, in adjacent tomato and pepper fields, a high percentage of infected tomato plants, but a low percentage of infected pepper plants.

Adkins took TSWV samplings from tomato and pepper plants back for analysis by scientists in ARS' Subtropical Plant Pathology Research Unit at Ft. Pierce, Fla. He is trying to see if one host (tomato) is affecting the ability of TSWV to infect the other host (pepper) and vice versa.

The virus can turn leaves brown, purple or bronze and frequently kills the plants' stem tips. It can also cause brown or yellow spots and rings on tomatoes and other produce, making them unappealing to consumers and therefore unmarketable.

TSWV is transmitted from plant to plant almost exclusively by several species of thrips. The western flower thrips (Frankliniella occidentalis) and the tobacco thrips (F. fusca) are major vector species in Florida, although F. bispinosa may also be a locally important vector.

Adkins is working closely with UF plant pathologist Tim Momol, who is located at the North Florida Research and Education Center in Quincy. Southeastern produce growers are showing great interest in their work.

Adkins hopes to characterize the diversity of the virus across the wide range of host plants TSWV infects, not only in the region, but also throughout the United States. Once this is determined, he can use the information to develop improved virus management strategies and crop cultivars that will resist infection.

ARS is the U.S. Department of Agriculture's principal scientific research agency.