Corn, sweet-Corn rootworm (larvae)

Western spotted cucumber beetle (Diabrotica undecimpunctata)

Pest description and crop damage The western spotted cucumber beetle is the primary species of corn rootworm in the Pacific Northwest. It is yellowish green, 0.25 inch long, and has 11 black spots on its wing covers. Mature larvae are white except for the head and last abdominal segment, which are brown. They are about 0.62 inch long. The larvae appear to have two heads.

Corn rootworm larvae feed on roots and bore into the base of stems, killing corn seedlings and reducing root mass in mature corn plants. Significant corn rootworm pressure can reduce plant establishment, reduce plant growth (due to root damage), and contribute to lodging of corn plants prior to harvest.

Pest Monitoring No action threshold has been established in Oregon. If significant numbers of adult beetles are observed feeding and laying eggs in unprotected sweet corn plantings at emergence, this may justify a postemergence insecticide treatment.

Management-chemical control: HOME USE

  • bifenthrin
  • carbaryl
  • cyfluthrin
  • cyhalothrin
  • deltamethrin
  • esfenvalerate
  • gamma-cyhalothrin
  • lambda-cyhalothrin
  • malathion
  • permethrin
  • pyrethrins
  • zeta-cypermethrin

Management-chemical control: COMMERCIAL USE

  • bifenthrin (Capture LFR) at 0.08 to 0.2 lb ai/a banded or over furrow. REI 12 hr. Do not exceed 0.2 lb ai/a per season. Prohibited in coastal counties.
  • bifenthrin + IBA (Empower 2) at 0.002 to 0.006 lb ai/1,000 linear row ft at plant. PHI 30 days. REI 24 hr. Do not exceed 0.1 lb ai/a at plant application.
  • chlorethoxyfos (Fortress) at 0.15 to 0.225 oz ai/1,000 row ft. REI 48 hr or 72 hr if annual rainfall is less than 25 inches.
  • chlorpyrifos (Lorsban 4E, Lorsban 15G)-REI 24 hr. Consult label for application details. Toxic to fish.
  • clothianidin (Poncho 600) at 0.25 to 0.5 mg ai/kernel seed treatment. Not for use in hopper-box, slurry-box, or similar applications. Use in liquid or slurry treaters.
  • ethoprop (Mocap 15G) at 1.2 oz ai per 1,000 row ft. Mocap 15G rate depends on row spacing; see label. REI 48 hr or 72 hr if annual rainfall is less than 25 inches. Applied as a band on row or closed seed furrow, or as side-dress from planting to lay-by. Do not contact seed.
  • gamma-cyhalothrin (Declare) at 0.0025 lb ai/1,000 row ft. PHI 21 days. REI 24 hr. Do not exceed 0.024 lb ai/a.
  • phorate (Thimet 20G) at 0.056 to 0.075 lb ai/1,000 row ft. PHI (see label). REI (see label). Apply at planting time or cultivation. Do not exceed 1.3 lb ai/a per year. Limit 1 treatment per year.
  • tefluthrin (Force 3G) at 0.008 to 0.009 lb ai/1,000 ft row (0.12 to 0.15 oz ai/1,000 ft row). REI 0 hr. Use either at planting or lay-by. Only one application per year.
  • terbufos (Counter 15G) at 0.056 to 0.075 lb ai/1,000 row ft. PHI 60 days for ears, 30 days for grazing or forage. REI 48 hr, or 72 hr if annual rainfall is less than 25 inches. Use either at planting or postemergence. Do not exceed 1.3 lb ai/a. Toxic to fish and wildlife.