Tomato Spotted Wilt Virus and Impatiens Necrotic Spot Virus: Two Serious Threats to Greenhouse Plantings

Gail Ruhl, Sr. Plant Disease Diagnostician

Two closely related viruses, Tomato spotted wilt virus (TSWV) and Impatiens necrotic spot virus (INSV), have an extremely wide host range and are spread by thrips insects. Greenhouses provide an excellent opportunity for thrips survival and population growth and thus the presence of these viruses in greenhouse plantings pose a serious threat to the greenhouse industry.

Symptoms of TSWV/INSV vary depending on the host, the environmental conditions, and the individual virus infecting the plant.

TSWV can cause very heavy losses for growers producing greenhouse tomatoes. Symptoms of TSWV on tomatoes include dark, brown necrotic spots on leaves, dark streaks on stems, stunted growth and discolored fruit. Other vegetable plants affected by TSWV include tomato, pepper, potato, eggplant, lettuce, spinach and cucumber. Several ornamental plants are also affected by TSWV and many weeds may serve as hosts. Thus, greenhouse growers should avoid planting ornamentals in the same greenhouse as vegetables since ornamentals can be provide a reservoir for TSWV and the areas beneath the benches should be kept clear of weeds that may serve as virus hosts.

INSV has been confirmed on over 300 ornamental hosts and can produce a wide variety of symptoms including etching, sunken spots, mosaic patterns or ringspots on leaves; streaking and death of stems, wilting, stunting, and poor flowering.

Diagnosis often is difficult when it is based on symptoms alone since symptoms caused by INSV and TSWV may resemble symptoms caused by fungal and bacterial diseases or environmental stresses. Positive diagnosis using specialized serological testing is necessary for confirmation of the presence of these viruses in plant tissue. Plants with suspect virus symptoms may be submitted to the Purdue Plant and Pest Diagnostic Lab for serological testing to determine if a virus is present in the plant sap.

Management of TSWV and INSV requires scouting for symptoms, accurate diagnosis, destruction of infected plants and controlling the thrips vector using a combination of insecticides and yellow sticky trap monitors.

Related publications:

Cornell e-Gro Alert: A Pictorial Guide to Common Symptoms of INSV in Greenhouse Crops

E - 110-W Western Flower Thrips