Corn seed-Corn rootworm (adult)

Diabrotica spp.

Pest description and crop damage Adults feed on corn silks, causing loss of seed yield by interfering with pollination.

Management-chemical control

Warning: Apply only if corn rootworm adults are at two adults per ear during green to brown silk stage. All of the following foliar spray insecticides applied to silking corn are toxic to bees and other pollinators. Apply late in the day or in the evening, when bee activity is minimal. Do not make applications or allow applications to drift to blooming crops or weeds if bees or other pollinating insects are foraging in the treatment area. Products are also toxic to fish and aquatic invertebrates.

  • alpha-cypermethrin (Fastac EC) at 0.017 to 0.025 lb ai/a. PHI 30 days. REI 12 hr. If crop residue is to be fed to livestock, PHI 30 days grain & stover; 60 days forage. Retreatment interval 3 days. Do not exceed 0.075 lb ai/a per season. Not for use on sweet corn seed. (Group 3A)
  • beta-cyfluthrin (Baythroid XL) at 0.013 to 0.022 lb ai/a. REI 12 hr. If crop residues are to be used for fodder, there is a 21 PHI; PHI is 0 days if used for forage. REI 12 hr. Do not exceed 0.088 lb ai/a per season. Retreatment interval 7 days. (Group 3A)
  • bifenthrin (Bifenthrin 2EC; numerous other products) at 0.033 to 0.1 lb ai/a. PHI 30 days. REI 12 hr. Do not exceed 0.3 lb ai/a per season. Bifentrhin is highly toxic to bees exposed to direct treatment or residues on blooming crops or weeds. Do not apply bifenthrin or allow it to drift to blooming crops if bees are visiting the treatment area. (Group 3A)
  • bifenthrin/zeta-cypermethrin (Hero) at 0.04 to 0.1 lb ai/a. PHI 3 days for sweet corn seed. Do not graze livestock in treated areas or cut treated sweet corn seed crops for feed within 3 days of the last application. For non-sweet corn seed crops, there is a PHI of 30 days for crop residues harvested for stover; do not allow livestock to graze on crop residues for 30 days after treatment. REI 12 hr. Do not exceed 0.4 lb ai/a per season. R (Group 3A)
  • chlorpyrifos (Lorsban 4E; other formulations and products) at 0.05 to 1 lb ai/a. If crop residue is to be fed to livestock, PHI is 21 days for grain, ears, forage or fodder. REI 24 hr. Do not exceed 3 lb ai/a per season. (Group 1B)
  • chlorpyrifos/gamma cyhalothrin (Cobalt) at 0.26 to 0.52 lb ai/a. Do not apply within 21 days before harvest of grain, ears, forage or fodder. REI 24 hr. Do not exceed 3 applications nor 2.5 lb/a per season. (Groups 1B and 3A)
  • cyfluthrin (Tombstone) at 0.025 to 0.044 lb ai/a. PHI 21 days for grain or fodder. REI 12 hr. Do not exceed four applications or 0.175 lb ai/a per season. (Group 3A)
  • dimethoate (numerous products) at 0.33 to 0.5 lb ai/a. PHI 14 days forage; 28 days grain; 14 days for forage if crop residues are to be fed to livestock. REI 48 hr. Do not exceed 0.5 lb ai/a per season. Not for use on sweet corn seed. (Group 1B)
  • esfenvalerate (Asana XL; other products) at 0.03 to 0.05 lb ai/a. PHI 21 days. REI 12 hr. Do not exceed 0.25 lb ai/a per season. (Group 3A)
  • lambda-cyhalothrin (Warrior II; other products) at 0.02 to 0.03 lb ai/a. 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. (Group 3A)
  • methomyl (Lannate LV; other products) at 0.225 to 0.45 lb ai/a. PHI 21 days for ears or stover. REI 48 hr. Do not exceed 2.25 lb ai/a per season. (Group 1A)
  • permethrin (numerous products) at 0.1 to 0.2 lb ai/a. Do not exceed 0.45 lb ai/a per season If crop residues are to be used for livestock, do not apply less than 30 days prior to harvest of grain or fodder (stover). Forage may be harvested on the day of application. Not for use on sweet corn seed. (Group 3A)
  • zeta-cypermethrin (Mustang, Mustang Maxx) at 0.034 to 0.05 lb ai/a (Mustang) or 0.017 to 0.025 lb ai/a (Mustang Maxx). PHI 7 days. REI 12 hr. Do not exceed 0.2 lb ai/a per season (Mustang) or 0.1 lb ai/a per season (Mustang Maxx). Refer to product labels for application limits if multiple products containing zeta-cypermethrin are to be used in the same season. Degree of control will depend on the species present and plant-insect interactions. Mustang and Mustang Maxx are not for use on sweet corn seed. Zeta-cypermethrin 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)

For additional information

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