Alfalfa hay-Pea leaf weevil

Sitona lineata

Pest description and crop damage Adults are grayish brown weevils about 0.16 inch long with three faint stripes on the thorax. They appear in large numbers in spring and sometimes late summer.

Adult feeding occasionally can cause substantial defoliation, which is of most concern on seedling stands. Pea leaf weevil adults migrate in large numbers when other crops they are infesting are harvested. Their presence in fields is usually spotty, and targeted treatments at field margins can be very effective.

Management-chemical control

  • alpha-cypermethrin (Fastac EC) at 0.014 to 0.025 lb ai/a. PHI 3 days of cutting or grazing. REI 12 hr. Retreatment interval 7 days. Do not exceed 0.075 lb ai/a per season.
  • beta-cyfluthrin (Baythroid XL) at 0.0065 to 0.0125 lb ai/a. PHI 7 days for grazing or cutting. REI 12 hr. Retreatment interval 5 days. Do not exceed 0.044 lb ai/a per cutting or 0.175 lb ai/a total per season. (Group 3A)
  • chlorantraniliprole/lambda-cyhalothrin (Besiege) at 0.059 to 0.088 lb ai/a. PHI 1 day for forage and 7 days for hay. REI 24 hr. Minimum of 5 days between applications. Do not exceed 0.12 lb ai of products containing lambda-cyhalothrin or 0.2 lb ai of chlorantraniliprole-containing foliar products per acre per growing season. Refer to product labels for application limits if products containing gamma-cyhalothrin and products containing lambda-cyhalothrin are to be used in the same season. (Group 28 and 3A)
  • chlorpyrifos (numerous products) at 0.5 to 1 lb ai/a. PHI for grazing or cutting is 7 days at 0.25 lb ai/a or 14 days at 0.5 lb ai/a or 21 days for rates above 0.5 lb ai/a. REI 24 hr. Do not apply any chlorpyrifos products more than four times per season or more than once per cutting. Do not reapply within 10 days of the first application. Certain products can be chemigated by sprinkler irrigation. Minor phytotoxicity is possible on new growth. (Group 1B) RESTRICTED USE IN OREGON.