Corn seed-Corn rootworm (larvae)

Diabrotica spp.

Pest description and crop damage Larvae feed on corn roots. They cause stunting and lodging and occasionally kill plants. Larvae are 0.5 inch long and pale yellow with yellow-brown heads.

Management-chemical control

  • abamectin + thiamethoxam (Avicta Duo, other formulations of Avicta that also contain fungicides)-Only for use in certified seed treatment facilities. Applied as a slurry to corn seed. Consult label. (Groups 6 and 4A*)
  • bifenthrin (Bifenthrin 2EC, numerous other products) at 0.0046 lb ai/1,000 linear ft at plant or 0.047 to 0.062 lb ai/a preplant. PHI 30 days. REI 12 hr. Bifenthrin is highly toxic to bees and other pollinators exposed to direct treatment or residues on blooming crops or weeds. Do not apply bifenthrin or allow it to drift to blooming crops or weeds if bees or other pollinating insects are foraging in the treatment area. Extremely toxic to fish and aquatic invertebrates. Do not exceed 0.1 lb ai/a at plant. (Group 3A)
  • bifenthrin/chlorethoxyfos (Smart Choice 5G) at 4.5 to 5 oz/1,000 ft row. REI 48 hr; 72 hours where annual rainfall is less than 25 inches. (Groups 4A and 1B)
  • bifenthrin + indole-3-butyric acid (Empower II) at 0.005 to 0.006 lb ai/1,000 linear row ft. PHI 30 days. REI 24 hr. Do not exceed 0.1 lb ai/a at planting. Not for use on sweet corn seed. This product is highly toxic to bees and other pollinators exposed to direct treatment or residues on blooming crops or weeds. Do not apply this product or allow it to drift to blooming crops or weeds if bees or other pollinating insects are foraging in the treatment area. (Group 3A)
  • chlorpyrifos (numerous granular products and formulations) at 0.075 lb ai/1,000 row ft. PHI 21 days grain or ears. REI 24 hr. Do not exceed 0.15 lb ai/1,000 row ft or 3 lb chlorpyrifos ai/a per season. Apply at planting as a band or at cultivation as a band or side dress. Chlorpyrifos is highly toxic to bees and other pollinators exposed to direct treatment or residues on blooming crops or weeds. Do not apply this product or allow it to drift to blooming crops or weeds if bees or other pollinating insects are foraging in the treatment area. (Group 1B)
  • gamma-cyhalothrin (Declare) at 0.0025 lb ai/1,000 row ft at plant. PHI 21 days. Do not allow livestock to graze in treated areas or harvest treated corn forage as food for meat or dairy animals within 1 day after last treatment. Do not feed treated corn fodder or silage to meat or dairy animals within 21 days after the last treatment. REI 24 hr. Do not exceed 0.06 lb ai/a per 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. This product is highly toxic to bees and other pollinators exposed to direct treatment or residues on blooming crops or weeds. Do not apply this product or allow it to drift to blooming crops or weeds if bees or other pollinating insects are foraging in the treatment area. Extremely toxic to fish and aquatic organisms and toxic to wildlife. (Group 3A)
  • lambda-cyhalothrin (Warrior II; other products) at 0.005 lb ai/1,000 row ft (planting). PHI 21 days. If crop residues are to be used for livestock, PHI is 1 day for grazing, 21 days for fodder or silage. REI 24 hr. Apply no more than 0.12 lb ai/a per 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. Highly toxic to bees and other pollinators exposed to direct treatment or residues on blooming crops or weeds. Do not apply lambda-cyhalothrin or allow it to drift to blooming crops or weeds if bees or other pollinating insects are foraging in the treatment area. Lambda-cyhalothrin is extremely toxic to fish and aquatic organisms and toxic to wildlife. (Group 3A)
  • tefluthrin (Force 3G and other formulations) at 0.0075 to 0.0094 lb ai/1,000 row ft, T-banded or in-furrow at planting. Do not exceed one application per season. REI 48 hr. This product is highly toxic to fish and aquatic invertebrates. (Group 3A)
  • terbufos (Counter 20G) at 0.056 to 0.075 lb ai/1,000 row ft. If crop residues are to be fed to livestock, PHI is 30 days for forage or grazing. REI 48 hr or 72 hr where average rainfall is less than 25 inches per year. Do not exceed 1.3 lb ai/a per season. Do not apply an ALS herbicide if Counter 20G has been applied at planting. Not for use on sweet corn seed. This product is highly toxic to bees and other pollinators exposed to direct treatment or residues on blooming crops or weeds. Do not apply this product or allow it to drift to blooming crops or weeds if bees or other pollinating insects are foraging in the treatment area. (Group 1B)

For additional information

Western Corn Rootworm in Eastern Oregon, Idaho, and Eastern Washington, PNW 622, https://catalog.extension.oregonstate.edu/pnw662