The western flower thrips (Frankliniella occidentalis) and onion thrips (Thrips tabaci) are the two most common vectors of tomato spotted wilt virus (TSWV) in solanaceous crops. See TSWV disease description below. In addition to virus transmission, thrips will feed on leaves, developing buds, flowers, and fruits; and if populations are high, can cause economic loss. Typical symptoms are “rasping” and stippling injury on leaves, and stunted buds, flowers, and fruits. Thrips feeding on the surface of well-developed fruits can cause scarring. An abundance of dark tarspots of thrips frass can contaminate fruits.
Damage occurs as young and adult thrips feed on flower and shoot tips during the early growth stages, and if populations are high, they may feed on immature fruit. Feeding damage results in a silvering on leaves and sometimes deformed leaves that curl downward.
Use yellow or blue sticky traps in susceptible fields from seedling through flowering to determine the magnitude of the thrips population.
- Disk in weeds before they flower. This can lessen the attraction of thrips to the field. However, disking weeds after they have flowered (once thrips are present) can cause thrips to move into crop plants
Before deciding to treat for thrips, be sure to verify that the damage is thrips-related. Unnecessary treatments can cause spider mite buildup, so it is important to only consider treatment if the thrips population is causing serious damage to shoot tips, flowers, or fruit.