Pacific Northwest Insect Management Handbook

Pasture and grass hay-Grass scale (mealybug)

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Eriococcus insignis

Pest description and crop damage On timothy hay or timothy-alfalfa mixed-stand hay crops only. This scale weakens stands. It can be a serious pest in western regions where it has become established. A serious pest in all of western Washington.

Management-chemical control

  • bifenthrin (Brigade WSB) at 0.05 to 0.1 lb ai/A. PHI 30 days for forage and hay. REI 12 hr. Retreatment interval 14 days. Do not exceed 0.2 lb ai/A per year .
  • chlorantraniliprole/lambda-cyhalothrin (Besiege, Voliam Xpress) at 0.0391 to 0.0652 lb ai/A for chlorantraniliprole and 0.0195 to 0.0325 lb ai/A for lambda-cyhalothrin . PHI 0 days for grazing or cut for forage; 7 days for cut grass to be dried and harvested for hay. Retreatment interval 7 days. REI 12 hr. Do not exceed 0.09 lb ai/A lambda-cyhalothrin or 0.2 lb ai/A chlorantraniliprole.
  • gamma-cyhalothrin (Declare) at 0.01 to 0.015 lb ai/A. PHI 0 days for grazing or cut for forage; 7 days for cut grass to be dried and harvested. REI 24 hr. Do not exceed 0.045 lb ai/A per season.
  • lambda-cyhalothrin (Warrior II) at 0.02 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.
  • zeta-cypermethrin (Mustang, Mustang Maxx) Mustang at 0.035 to 0.05 lb ai/A; Mustang Maxx at 0.0175 to 0.025 lb ai/A. PHI 3 days for cutting and grazing; 7 days for seed. REI 12 hr. Do not apply more than 0.05 lb ai per cutting or 0.15 lb ai per season of Mustang or 0.025 lb ai per cutting and 0.075 lb ai per season of Mustang Maxx. Retreatment interval 7 days.

Kaur, N. (Ed.). 2024 Pacific Northwest Insect Management Handbook.
© Oregon State University.

Use pesticides safely!

  • Wear protective clothing and safety devices as recommended on the label. Bathe or shower after each use.
  • Read the pesticide label—even if you’ve used the pesticide before. Follow closely the instructions on the label (and any other directions you have).
  • Be cautious when you apply pesticides. Know your legal responsibility as a pesticide applicator. You may be liable for injury or damage resulting from pesticide use.

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