Longevity of noninfective and infective leafhoppers on a plant nonsusceptible to a virus

Abstract

does not appear. First page follows. Introduction In a recent paper (Severin, 1946),3 evidence was presented that nine species of leafhopper vectors tested, completed the nymphal stages on celery or asters infected with the California aster-yellows virus, but died when transferred to healthy celery or asters. Conceivably, this might be either (1) because the virus itself is beneficial to the vector, or (2) because the host plant is modified by virus infection to become a more favorable food and breeding plant for the vector. This paper deals with the first possibility, through a comparative study of the longevity of noninfective and infective leafhoppers on a host plant non-susceptible to the virus. If the virus is beneficial to the vectors, it is reasonable to assume that the adult life of infective leafhoppers reared during the nymphal stages on infected host plants would be longer on a host plant nonsusceptible to the virus, than that of noninfective adults kept on the same species of non-susceptible host plant. On the other hand, if the virus is injurious to the vectors, then the longevity of infective leafhoppers would be shorter than that of noninfective adults kept on the same species of nonsusceptible host plant. It is not the purpose of this paper to enter into a discussion as to whether the plant has been modified by virus infection to become a more favorable host plant for the vector. Methods Short-winged and long-winged aster leafhoppers were used. The latter is a biological race of the same species, Macroeieles divisus Uhl. The noninfective insects were reared on mildew-resistant Sacramento barley, which is nonsusceptible to the virus. Infective leafhoppers were reared on diseased China asters (Callistephus chinensis) and plantain, or ribgrass (Plantago major). In January, soon after the last molt, lots of 50 or 100 noninfective and infective male or female leafhoppers were confined in cages enclosing Sacramento barley. Each month the leafhoppers were transferred to thrifty growing barley plants, and a record was taken of the mortality.