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Joseph F. Boggs, Ohio State University Extension, Hamilton County/Southwest District; Curtis E. Young, David J. Shetlar, James A. Chatfield, Erik A. Draper, Pamela J. Bennett, Gary Y. Gao, |
Mites
Overwintered eggs of the spruce spider mite (Oligonychus ununguis) hatched in southwestern Ohio in early April and in the northeast part of the state by the middle of April. Adults of this cool-season mite appear in the spring and fall. The summer and winter months are spent in the egg stage. Mite populations expanded rapidly during the dry weather experienced during March and April in the southern part of the state. By the end of April, some areas of southern Ohio were eight inches below average in rainfall. However, the rainfall deficit was eliminated by heavy rains in May, June, and July. Consequently, spruce spider mite populations plummeted with adult mites being washed from the trees in May. Populations did not recover in that part of the state throughout the spring and early summer.
Fall populations fared much better. Dry periods in September and October allowed populations to build to damaging levels in both southern and central Ohio. For example, severe damage and heavy webbing were observed on Colorado blue spruce in late September in the Dayton, Ohio, area.
Warm-season mite populations were also adversely affected by the weather this past season. The two-spotted spider mite (Tetranychus urticae) failed to repeat the high numbers observed during the 2000 season (8). High populations of other warm season mites were also rarely observed during the 2001 season. These included oak spider mite (O. bicolor), maple spider mite (O. aceris), and the honeylocust spider mite (Eotetranychus multidigituli).