P&PDL Picture of the Week for
May 2, 2011

Tomato Spotted Wilt Virus

Tom Creswell, P&PDL Director, Plant Disease Diagnostician;
Gail Ruhl, Sr. Plant Disease Diagnostician
;
Dan Egel, Vegetable Pathologist, Department of Botany & Plant Pathology; and
Ricky Foster, Professor, Pest Management Vegetable and Fruit Crops, Department of Entomology, Purdue University

Tomato Spotted Wilt Virus (TSWV) can cause very heavy losses for growers producing greenhouse tomatoes. 

Symptoms of TSWV on tomatoes include dark, brown necrotic spots on leaves, dark streaks on stems, stunted growth and discolored fruit.  Symptoms vary according to host.  Other vegetable plants affected by TSWV include tomato, pepper, potato, eggplant, lettuce, spinach and cucumber.  Several ornamental plants are also affected by TSWV and many weeds may serve as hosts.

TSWV is spread from plant to plant by thrips, which are insects less than 1/20th of an inch long. TSWV has usually been a more serious disease of vegetables in tropical and subtropical climates than areas of the Midwest such as Indiana.  This is because the thrips vectors do not overwinter well here.  Greenhouses provide an excellent opportunity for thrips survival and population growth. TSWV can move from a greenhouse to a nearby field of susceptible crops, such as tomato.  If you have TSWV and thrips in a greenhouse near where you plan to grow field tomatoes, you should make every effort to eliminate the virus and thrips before you plant in the field.

Management of TSWV centers on clearing out infected plants and using resistant varieties; and by controlling the thrips vector using a combination of insecticides and yellow sticky trap monitors. Growers should avoid planting ornamentals in the same greenhouse as vegetables since ornamentals can be provide a reservoir for the virus. They should also keep the area clear of weeds that may serve as hosts for TSWV. 

Click image to enlarge

Affected plants in greenhouse

Infected plants may show collapse of entire stems

Severely affected leaves

Stem lesions often develop on infected plants

TSWV often causes distinctive ring patterns in affected leaves

 

Photos courtesy of Liz Maynard

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service