TSWV can survive the winter in hundreds of plant species, including scores of common bedding plants and weeds. Thrips can pick up the virus from an infected plant and spread it repeatedly, every time it feeds on a new plant. Because there is usually a time lag of several weeks between TSWV infection and symptom development, growers can unsuspectingly transplant infected plants. Thrips can continue to spread the virus in the field. If infected plants are present early in the season, the extent of the problem can continue to snowball.
Thrips tend to hide in crevices in flowers and young foliage, where spray penetration is often poor.
Clean up all weeds in and surrounding the houses. Remove any symptomatic plants. Do not accept any shipments of transplants with thrips populations or symptoms. Monitor thrips in the greenhouse, using yellow or blue sticky cards placed near vents and slightly above crop level. Thrips become stuck in the sticky material on the cards and should be counted at least once per week.