Potential of Panonychus osmanthi（Acari: Tetranychidae）-Infested Sweet Osmanthus Windbreak Trees As Protection and Breeding Sites for Natural Enemies of the Citrus Red Mite, Panonychus citri（Acari: Tetranychidae）, in Citrus Orchards

Panonychus osmanthi Ehara et Gotoh—a species closely related to the citrus red mite, Panonychus citri—occurs on sweet osmanthus. Satsuma mandarins are poor hosts for P. osmanthi in terms of the development status and egg production, and P. citri cannot develop on sweet osmanthus. Therefore, P. osmanthi-infested sweet osmanthus plants are likely to serve as sites for the preservation of the natural enemies of P. citri in citrus orchards. We investigated the growth status of sweet osmanthus as a windbreak hedge and the occurrence of P. osmanthi and its natural enemies. The young sweet osmanthus trees grew into a windbreak hedge 5 years after being planted. Panonychus osmanthi was found to be widely distributed on sweet osmanthus in parks and on roadsides. Common natural enemies of P. citri and P. osmanthi—predaceous insects and phytoseiid mites—occurred on the sweet osmanthus. When citrus and sweet osmanthus were planted close to each other, the mite occurrence patterns on both types of trees were nearly identical, but the peak period of P. osmanthi density on sweet osmanthus sometimes occurred slightly earlier than that of P. citri on citrus trees. These results suggest that sweet osmanthus windbreak trees function as sites for the preservation of native natural enemies in citrus orchards.