Abstract
The Seasonal population trends of the Japanese pear rust mite, Eriophyes chibaensis KADONO, were studied in a pear orchard in Chiba during the period 1979-1980. Emergence of the overwintered mites from hibernation sites started in late March and reached a peak in early April precisely when buds started opening. When the succulent shoots began to expand in late April, a few mites infested the leaves. In mid and late May, the number of mites infesting leaves at the upper part of succulent shoots increased rapidly and reached a peak from late June to early July. Thereafter the number decreased sharply till late July. On the other hand, mites on leaves at the lower part of succulent shoots and on clusters showed a low density throughout the growing season. When young leaves emerged after early August, mites continued to stay on these leaves till December. Mites, which were trapped on glass slides coated with silicon grease, included both adults and nymphs. Seasonal changes in the number of mites trapped on these slides corresponded well to those of mites on leaves. In early July, a considerable number of deutogynes were already observed at the base of bud scales as well as in scar crevices of succulent shoots, especially at the lower part of shoots, and thereafter the number of deutogynes declined drastically.
