DISEASES

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Impatiens Necrotic Spot Virus (INSV) Most susceptible plants: begonia, chrysanthemum, exacum, gloxinia, impatiens, vinca This is one of the most serious diseases of greenhouse crops. INSV has a very large host range, numbering more than 648 different plant species. It is the number one disease of gloxinia and impatiens. INSV is transmitted by the thrips insect; it is not known to be routinely transmitted by any other means. One of the most frustrating features of INSV is that infection can result in a number of different symptoms. Symptoms: Symptoms of INSV infection may include black ring spots (impatiens), black foliar lesions (impatiens, vinca, cineraria), chlorotic ringspots (exacum, gloxinia, cyclamen), veinal necrosis (gloxinia, Aphelandra, impatiens), stem lesions (chrysanthemum, exacum), distortion of young growth, stunting and plant wilt. These symptoms can vary with the stage of growth of the host and with a variety of cultural conditions. Plants infected with INSV are systemically infected for the life of the plant. Although the plants are systemically infected, INSV can "compartmentalize" within its host, causing symptoms to occur only in a portion of the plant. Control: INSV plants must be rapidly and thoroughly rogued from the production area to reduce infection to other susceptible plants. Monitor thrips activity routinely throughout the production area by the use of yellow or blue "sticky cards." Destroy all weeds, both inside and outside the greenhouse, as weeds can serve as both a reservoir of the INSV virus as well as a habitat for the thrips vector. Control thrips activity by appropriate management strategies, including insecticides when needed.