October 8, 2003
From: Southeast Farm Press, Sept 12, 2003 [edited]

During the past 2 decades, TSWV has spread around the world by thrips [small insects that feed on plants], causing very high losses to a variety of vegetable, ornamental, and agronomic crops.

According to Steve Olson, a professor at University of Florida's North Florida Research & Education in Quincy, TSWV epidemics have been troublesome throughout the southern United States, cutting yields by 20-30 percent on tomatoes. Tomato and pepper crops in Florida and Georgia, valued at about $1 billion annually, have been hit hard, as have peanut crops.

Leaves of TSWV-infected plants turn brown, purple, or bronze and stem tips are frequently killed. Infected tomato fruits show spots and rings, and are unmarketable.

The virus 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 species in Florida.

Until recently, growers sprayed toxic, broad-spectrum insecticides in an attempt to control thrips, but the chemicals do not prevent virus transmission. The solution, according to researchers at the Quincy center, is to use a variety of new, environmentally friendly strategies known as integrated pest management (IPM).

IPM includes new cultural practices, natural insecticides, bio- control agents or natural predators, and a new treatment that boosts the plant's resistance system against viral and bacterial pathogens.

According to Tim Momol, an assistant professor of plant pathology at the Quincy center, incidence of TSWV infection in tomato has been reduced by as much as 75 percent, using a new plastic bed cover that reflects UV light and repels thrips.

He said that many producers have switched to the UV-reflective mulch, boosting tomato yields by as much as 600 (25-pound) boxes/acre and increasing profits by as much as $4000/acre.

Although the reflective mulch costs an extra $200/acre, yield increases and higher returns justify its use.

According to Joe Funderburk, a professor of entomology at the Quincy center, a recent survey showed that about 30 percent of the growers in north Florida and Georgia are using the UV- reflective mulch, and its use is expanding to other production areas in the Southeast in 2003.

He says a natural insecticide called spinosad, which poses little threat to field workers or the environment, also is helping growers control thrips on tomatoes. And, a new resistance-boosting treatment, which is marketed under the Actigard (R)* trademark, is now being used by about 45 percent of all tomato growers in the region. [*Reference to this product does not constitute an endorsement by ProMED-mail. - CopyEd.PG]

Olson, Momol, and Funderburk developed and promoted the new IPM control measures, and the researchers are collaborating internationally so that the program is adopted in other countries.

[Byline:Chuck Woods]