Aster-Yellows Virus Infection and Transmission by Macrosteles fascifrons (Stål) with Reference to Lettuce-Yellows Prevention

Abstract

Transmission studies with the eastern strain of the aster-yellows virus, Chlorogenus callistephi vulgaris Holmes, showed that after 18 days’ incubation of the virus in six-spotted leafhoppers, Macrosteles fascifrons (Stal), no differences were found in infectivity of viruliferous leathoppers with infection feeding periods of 3, 6, and 10 days on China aster, Callistephus chinensis . With 18 days virus incubation, two viruliferous insects per plant were as successful as larger numbers in inoculation of all healthy plants. Infective insects resting on plants for 10 minutes transmitted virus almost as readily as those caged on plants for 6 hours, but the percentage of infection was considerably higher for insects caged on plants for 24 hours. Most infective leafhoppers inoculated only one plant per 24-hour period of individual confinement to groups of plants. After becoming infective, 70 to 78% of viruliferous leafhoppers inoculated all plants on which they were confined individually for 12 to 48 hours in serial transfers. Such consistent infection was not obtained with 1-hour confinement periods. Five commonly grown varieties of lettuce and one variety of China aster were equally susceptible to aster-yellows virus infection under experimental conditions existing.