Diseases caused by the tospoviruses impatiens necrotic spot virus and tomato spotted wilt virus are among the most serious affecting greenhouse ornamental crops. Both are vectored by several species of thrips, although the western flower thrips, Frankliniella occidentalis, is generally considered the most important vector in ornamental crop systems.

First instar thrips larvae acquire the virus by feeding on an infected plant. Thrips typically do not leave the plant on which they developed until adulthood. The virus replicates within the thrips and is persistently transmitted by the mobile adult. Thus factors that influence adult thrips movement will clearly affect virus epidemics.

This study will examine the effect of two common production practices on thrips movement in the greenhouse. First, we will look at how the application of herbicides to weeds (chickweed, Stellaria media, and groundsel, Senecio vulgaris) that commonly grow on the greenhouse floor affects thrips mortality and movement onto the crop. Second, we will look at how the application of pesticides registered for thrips control to a commonly infected crop (impatiens, Impatiens wallerana) affects movement within and from the crop. Implications for virus management will be discussed.