BIOTYPE-J, A UNIQUE GREENBUG (HOMOPTERA, APHIDIDAE) DISTINGUISHED BY PLANT-DAMAGE CHARACTERISTICS

Eight greenbug, Schizaphis graminum (Rondani), (Homoptera: Aphididae) biotypes B, C, E, F, G, H and I, plus proposed biotype J (collected in Idaho) were tested for two damage characteristics on seedlings of sev en wheat and two barley entries. The two forms of damage recorded were : feeding lesions (necrotic lesions, chlorotic spots or no spots at al l) on leaves, which appeared during the first week after infestation, and the killing of plants by the 18th day after infestation. Combinati ons of both types of characters for the wheat and barley entries provi ded a unique damage pattern for each biotype. Wheat plants were killed only in those cases where greenbugs made necrotic lesions on leaves. The Idaho collected greenbugs (J) appeared to be a new unique biotype because they did not produce necrotic lesions in any wheat and barley entries tested, however they were the only greenbugs in these tests wh ich killed resistant POST barley in the time specified.