Tospovirus is a genus that includes Impatiens Necrotic Spot Virus (INSV) and Tomato Spotted Wilt Virus (TSWV). Western flower thrips is the predominant insect vector. Thrips acquire the disease as a first instar larvae as they feed on virus-infected plants (including infected weeds showing few, if any symptoms). Once mature, the winged adult thrips are primarily responsible for viral spread. An infected thrips is able to transmit tospoviruses to at least one plant per day until its death. Adults do not transmit the virus to their young. Sources of infection include infected plants, or weeds, or infected thrips. INSV/TSWV is not seedborne.
Tospoviruses have a large host range and most greenhouse crops are susceptible. Symptoms may resemble those caused by fungi, bacteria, or chemical spray injury. Infected plants may also show a wide range of symptoms depending upon the species or cultivar infected as you can see in our photo library or other resources listed below. On tomatoes plants, INSV symptoms showed as dark, concentric rings on the foliage. However symptoms on lobelia appeared as leaf distortion without ringspots. Some of the more common symptoms of TSWV/INSV include target leaf spots, necrotic areas, mottling and ringspots. Young plants are especially vulnerable to infection.
To confirm that plants are infected with tospoviruses, plants can be submitted to a diagnostic laboratory or growers can purchase easy to use immunostrips that are available from Agdia. (www.agdia.com). Separate immunostrips are available for TSWV and INSV.
There is no cure for plants infected with tospovirues. Infected plants should be rogued from the greenhouse by placing them in a plastic bag and removing them. Eradicate weeds and practice strict thrips management to prevent serious losses.
Photos
INSV on Coleus, TSWV on Tomato and positive test strip, INSV on Tomato
Photos of INSV and TSWV on various crops
A Pictorial Guide to Common Symptoms of INSV in Greenhouse Crops by Margery Daughtery and Nora Catlin, Cornell University
Resources
Diagnostic Test Kits, UMass Extension
Impatiens Necrotic Spot Virus and Tomato Spotted Wilt Virus, UMass Extension
INSV on Coleus by Nora Catlin, Cornell University
Western Flower Thrips Management and Tospoviruses, UMass Extension
Managing Western Flower Thrips on Greenhouse Crops, UConn Extension
Using Indicator Plants to Test for Tospovirus, UConn Extension
New England Greenhouse Floriculture Guide, A Management Guide for Insects, Diseases, Weeds and Growth Regulators.
Tina Smith, UMass Extension and Leanne Pundt, UConn Extension
