POPULATION-DYNAMICS OF THE CITRUS RED MITE, PANONYCHUS-CITRI (MCGREGOR) (ACARI, TETRANYCHIDAE) IN JAPANESE PEAR ORCHARDS

In spring a population of the citrus red mite (Panonychus citri), a no n-diapausing species, migrated to a Japanese pear orchard, mainly from nearby Japanese holly trees, but in autumn most of the mites starved to death while the rest returned to the holly trees. In the Japanese h olly trees, the population of mites reached their maximum density in l ate May 1993 and in mid-June 1994 on overwintered leaves and moved to newly opened leaves in mid-June 1993 and late June 1994. The mites ten ded to disperse abruptly in early June or mid-June and again towards t he end of June. The mites inhabiting the holly trees appeared to migra te to the Japanese pear trees in June but their densities on pear leav es remained low until mid-August. In the pear orchard, the mites initi ally tended to increase on pear leaves near the holly trees and then g radually spread to other leaves farther away from the holly trees. The ir highest density in the pear orchard occurred in mid-October. When p ear leaves were inoculated with two or five female adults at different times from May to September, the leaves inoculated before mid-August showed no increase in the number of mites. A possible cause for the su ppression of the population increase on pear leaves from June to mid-A ugust is discussed.