LABORATORY TRANSMISSION OF THE CITRUS STUBBORN DISEASE AGENT BY A LEAFHOPPER FROM THE CIRCULIFER-TENELLUS COMPLEX FROM THE JORDAN VALLEY

Citrus stubborn disease (=little leaf disease) is known to affect the size of citrus trees, and to reduce the quality and quantity of the fr uit. The disease agent, Spiroplasma citri, was isolated and cultured i n vitro from Oroblanco, orange and grapefruit orchards throughout the year from different regions in Israel. The agent was transmitted by a leafhopper from the Circulifer tenellus complex collected on Atriplex halimus plants in the southern Jordan Valley. The latent period of the agent in this vector was at least 10 days following a 3-day acquisiti on feeding on Matthiola incana plants. It was similar to that found fo r a primary isolation in culture medium (LP50=21 days). The limitation s of visual inspection for recording disease incidence in citrus grove s were determined and this method was compared with other methods for detection of the disease agent (immunoassay and cultivation in a cultu re medium). Plants from various botanical families were tested for the ir ability to serve as hosts for the Israeli biotype of the beet leafh opper and for the stubborn disease agent S. citri. The possible role o f Israeli C. tenellus in the disease epidemiology is discussed.