Originally created 05/19/00

Tomato plant virus is carried by insects



There seems to be an increase in a virus affecting tomato plants.

Tomato spotted wilt virus appears to be worsening each year. This virus is affecting tomato plants across the state but is at its worst in south Georgia.

Symptoms include leaves curling along the midvein; yellowing with coarse brown or black spots on leaves; water soaking into the stem; and purpling of the veins on the undersides of the leaves. The upper third of the plant is usually affected most.

The virus is carried by tiny insects called thrips. Thrips use their mouths to file away at leaves, stems and flowers to suck up sap flowing into the wound. They carry the virus and transfer it to the plant as they feed.

Unfortunately, available insecticidal controls have had no effect in reducing incidence of the disease, according to researchers.

Entomologist David Adams of the University of Georgia Extension Service has had some success with restricted-use insecticides on a very tight spray schedule, but none of the chemicals are available in the home market.

Covering plants with a netting material is a control possibility. This material is apparently available only in large quantities and in garden centers farther south.

The key is to cover plants started from seed rather than purchased transplants, which may already have the virus but are not displaying symptoms. Plants could be covered at least until a good crop has been set.

Starting plants indoors from seed may allow for production of virus-free plants before they are planted outside or covered with netting material. Because thrips are so small, they could travel indoors through open windows, gaps in screens and on clothing.

Researchers in Florida have developed a tomato variety with good resistance to the virus. It was planted to a limited extent in commercial fields last year. It is a Roma-shape tomato that has shown much promise.

However, the agronomic qualities of this variety may not be suitable for the home market. It is encouraging that a variety with resistance exists. It might lead to one for homeowners to use in the next three to four years.

The best thing a gardener can do for now is pull up the infected plants and plant healthy ones.

Sid Mullis is director of the University of Georgia Extension Service office for Richmond County. Call him at 821-2349, or send e-mail to smullis@uga.edu.