Pasture and grass hay-Clover and winter grain mite

Clover mite (Bryobia praetiosa)
Winter grain mite (Penthaleus major)

Pest description and crop damage Clover mite is light brown; winter grain mite is blue with red legs. These cool-season mites have caused serious damage in central Oregon pastures since 1999. Populations build in October; most damage to grass pastures is from late February through May. Grass pastures do not green up in the spring. Large populations have killed orchardgrass pastures.

Management-chemical control

Effective insecticides that control clover mite have not been identified. The three synthetic pyrethroids listed below are not labeled for winter grain mite control, but research in OR has shown them to be effective on this particular pest when used at mid-range label rates for other pests. These are recommended in Washington and Oregon only.

  • beta-cyfluthrin (Baythroid XL) at 0.013 to 0.015 lb ai/a. PHI 0 days for grazing or hay. REI 12 hr. Do not exceed 0.089 lb ai/a per season Retreatment interval 5 days.
  • lambda-cyhalothrin (Warrior II) at 0.015 to 0.03 lb ai/a. PHI 0 days for grazing and forage; 7 days to be dried for hay. REI 24 hr. Do not exceed 0.03 lb ai/a per cutting or 0.09 lb ai/a per season.