Oviposition and Hatching Time of the Winter Eggs of the Citrus Red Mite, Panonychus citri (MCGREGOR), on Pear in Tottori Prefecture (Acarina: Tetranychidae)

Abstract

The citrus red mite, Panonychus citri (MCGREGOR), is composed of two strains in Japan. One undergoes diapause, the other is a non-diapause strain. In this paper, the diapause citrus red mite was handled in pear orchards at Daiei and Akasaki, Tottori Prefecture. Winter eggs of this mite were deposited in groups on roughened bark areas at the base of buds, spurs, in wounds and training strings from late September to October. It was found that there is a high correlation between the number of female adults on leaves late in September and the amount of overwintering eggs. It was assumed that diapause in P. citri is completed by early March from the results of warming test through which winter eggs were collected from a pear orchard and incubated at 20°C. The hatching of overwintered eggs was observed from the middle of April to the beginning of May in the field. As a result of the examination of the relation between climatic conditions and the hatching date of winter eggs during the period 1965-1977, a high correlation was found between the initial time of hatching or the time when 50% of winter eggs were hatched and the maximum or the mean temperature during the period extending from early March to early April.