Thrips are the vector of Impatiens Necrotic Spot Virus (INSV) in the greenhouse. The following is more information.
INSV is a Topsovirus vectored exclusively by thrips. There is no cure or treatment for INSV. When INSV is diagnosed it is recommended that the plants be discarded and to begin a rigorous program for controlling the thrips population. Thrips should be prevented from entering greenhouses by monitoring new shipments of plants. Do not grow ornamental plants and vegetable plants in the same greenhouse. Also, remove all plant debris on benches and floors.
Remember the soil under greenhouse benches is where thrips work through their developmental stages. In empty greenhouses, close vents and keep the house heated and empty for a week or more between crops to stimulate development of thrips pupae in the soil and eliminate emerging adults. Use an insecticide to knock down emerging adults. Weeds serve as a reservoir of both INSV and Tomato spotted wilt virus (TSWV): eliminate weeds in and around the greenhouse.
Biological controls for thrips include predacious mites (Hypoaspis species, Amblyseius cucumeris), beneficial nematodes (Thripinema nicklewoodii, Steinernema feltiae), entomopathogenic fungi (Beauveria bassiana), or predacious bugs (Orius insidiosus). Biological control should not be used when either INSV or Tomato spotted wilt virus (TSWV) is already present in the greenhouse and should be part of an IPM program. Recommendations for insecticides are available in the New England Floriculture Management Guide.
Information from the current edition of the New England Greenhouse Update