Pest description and crop damage Tiny, elongated, yellowish to brown eriophyid mites that feed on the undersides of leaves, causing yellow blotching and reduced leaf size in some varieties. Feeding on young developing fruit causes them to become brown shortly after petal fall. Loganberries are particularly susceptible. Mite feeding may cause red raspberry fruit to appear sun scalded, with whitish to tan areas of dead drupelets, especially at the stem end of the fruit. Early fruits are often the most affected, while later fruit often escapes injury. Note: the symptom of "dryberry" may have other causes, such as poor pollination or fungal disease.
Biology and life history Dryberry mites overwinter in colonies, partly concealed by the buds. Colonies often contain 50 to 60 mites. These mites live and feed on the outside of developing fruits.
Predator mites are effective natural controls.
Management-chemical control: COMMERCIAL USE
- calcium polysulfide (lime sulfur, Sulforix, and other brands)-Consult label for rate and use directions. Apply at least 200 gal/a spray solution at bud swell and again as buds begin to break and show silver. Note: Calcium polysulfide is used at bud break to suppress spur blight, which should help control dryberry mite. Some formulations are OMRI-listed for organic use.
- diazinon (several brands) at 1 to 2 lb ai/a. PHI 7 days. Apply as a dormant spray in early spring and when buds are closed. Apply in sufficient water to achieve good coverage. One application per season allowed; as such, consider other pests that may need to be managed with diazinon. Restricted use pesticide.