Transmission of California aster-yellows virus by the first reported leafhopper vector in Gyponinae

Abstract does not appear. First page follows.

Introduction

Severin reported evidence that 10 leafhopper species and a biological race of one species (1940) transmit the California aster-yellows virus (1929), (1934), (1945).3 The present paper deals with the transmission of the virus by Gyponoma hasta DeLong. The characters, distribution, and food plants of this leafhopper have been discussed by (DeLong and Severin (1946)) in a companion paper.

An investigation was undertaken on the transmission of the virus to healthy celery and asters by single males and females and by varying numbers of adults. Experiments were conducted to determine the latent period and the retention of the virus in the adults, and whether this leafhopper could transmit the viruses of curly top and of Pierce’s disease of grapevines. Life history studies were undertaken on the egg periods, egg-laying capacity, and duration of the nymphal stages. Measurements of various parts of the body were taken of each nymphal instar and of the adults.

Methods

To determine the latent period of the virus in the adults, high populations of noninfective leafhoppers were reared on California common, or Chilean alfalfa, Medicago sativa, which is nonsusceptible to the disease. Infective leafhoppers were reared on celery infected with the virus. Life history studies were undertaken with nymphs which hatched from eggs deposited in the petioles of diseased celery. After determining the egg periods, the petioles in which oviposition occurred were cut into pieces a day or two before hatching and placed in stender dishes, the bottoms of which were covered with moist filter paper. Each nymph which hatched was transferred to an infected celery plant, and daily observations were made to determine each molt.

Transmission of Virus to Celery

By Single Males and Females.—The efficiency of the vector in the transmission of the virus to healthy celery was determined with 50 males and 50 females. (The nymphal stages on diseased celery required an average of 84.5 and 81.0 days, respectively, during January and February, as shown in table 6.) Each leafhopper was kept on a healthy celery plant until symptoms of the disease developed, or during adult life if no symptoms appeared. Table 1 indicates that 18 per cent of the males and 12 per cent of the females caused infections.