In the last month we have had several samples come into the Plant Disease and Insect Clinic with impatiens necrotic spot virus (INSV). These have primarily been greenhouse crops like impatiens and mums but the virus can infect over 200 plant species. It is a lethal virus spread by thrips feeding. Managing INSV is critical because it can easily over run your crop and cause you long-term problems. Thrips become infected with the virus while feeding as larvae. After they pupate thrips spread the virus to new plants when they feed as adults.
Thus, INSV management starts with thrips management. You can read more about thrips management in a Insect Note and recent article in GrowerTalks. The essence though is to start with sanitation. Thrips can feed on hundreds of plants so any weeds growing in or near your greenhouse can support thrips feeding and egg laying. Get rid of pet plants and mother plants. Maybe you or you grandmother want to overwinter last years peppers or begonias but don’t. Its not worth it. These can serve as reservoirs for thrips and virus and keep your house constantly infected.
If you have INSV in the greenhouse get rid of all plants that show symptoms and consider get rid of all plants that thrips have fed on. Plants do not immediately show symptoms but they can still infect thrips. So even if you get rid of plants with visible spots thrips may continue to get infected and spread the virus. Get rid of thrips with insecticide applications or ramp up an existing biological control program to get thrips under control. Now is not the time to start a biological control program.
Keep an eye out for tell tale rings and spots on leaves so you can keep ahead of this virus and of course monitor for thrips with sticky cards to keep ahead of them.