It is that time of year again to scout for thrip invasions. Many local growers are already reporting infestations and there are concerns in other states that they are building resistance to many chemicals. Thrips can be found primarily on herbaceous plants. They feed on rapidly growing tissue and buds and can sometimes be hard to see. Feeding by thrips typically causes tiny scars on leaves and fruit, called stippling, and can stunt growth. Be sure to thoroughly inspect all incoming plant shipments and monitor with blue pestraps to evade any major infestations.
There are several strategies to reduce thrip infestations. Thrips are poor fliers but can spread long distances by floating with the wind or being transported on infested plants. No-thrip insect screens or Anti-virus insect screens are recommended for all vents and doors on your greenhouse to minimize insect populations from entering. Try to avoid excessive applications of nitrogen fertilizer, which may promote higher populations of thrips due to the rapid increase of plant growth. It is also recommended to remove and dispose of old, spent flowers and prune the infected sections of the plant.
Another strategy for thrip control is the use of beneficial insects. This strategy is similar to chemical management in that multiple releases are necessary just as multiple applications are for chemicals. If you are attempting an organic approach, this strategy is highly suggested. Below are several options for beneficial insect control. Follow the links to read a detailed description about each insect.
The key to any of these strategies is scouting! Inspect your plant material on a regular basis and react as soon as you notice a problem. Populations can get out of control fast and become a persistent problem. Create a program that combines the different strategies to help you prevent and control any future or existing thrip infestations.