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What Corn Rootworm Can Mean For Your Crop

August 19, 2021
Corn Rootworm on a Corn Stalk

Corn rootworm beetle found on corn stalk

Imagine you’re scouting your corn crops and you identify an insect as a corn rootworm beetle. You know the damage this pest can cause, but now that you’ve spotted one, what does this mean for your crops?

Diabrotica virgifera, otherwise known as corn rootworm (CRW), is a common, economically damaging pest for corn growers, especially in corn-on-corn fields. As larvae, CRW can cause damage to the root tissues and hairs, and when the larvae turn into beetles, they will burrow further into the roots to find their food source.

When this occurs, by the time the symptomology can be seen above ground, crop injury is high. Even when CRW doesn’t cause any visual symptomology in the field it can cost growers around 20 bushels.

Scouting for Corn Rootworm

In the Midwest, the average lifecycle for CRW ranges from mid-May to early September. Scouting for CRW larvae and CRW beetles should happen throughout the entire season. If you see adult beetles when scouting this summer, you should take action to protect both your current crop and next season’s crop. Those adults will lay eggs that will hatch in the 2022 season. Soon after, larvae will start feeding on your young corn crop.

Here are some helpful tips on how to scout for CRW:

  • In the V7 to V10 stage of the corn growth, you can dig roots and put them in a pail of water to float CRW larvae to the surface and see what kind of feeding you have on those roots.
  • If you’re looking for corn rootworm beetles, generally the, R1 to R3 stage right after pollination is a very good time to scout for corn rootworm beetles. As corn silking begins, setting up yellow sticky traps can help get an idea of how severely your crop is infested.
  • If you notice beetles flying around an existing corn crop, that is a clear sign of corn rootworm. It is important to keep in mind that these beetles are laying eggs.
  • One visual symptomology is goose-necking. From this you will see nodal roots eaten off at the ground level.
  • Corn rootworm is a highly adaptable pest, so getting ahead of the game and treating it year-round can help eliminate pest pressures for the next growing season.

The York, NE, Grow More™ Experience site is currently studying CRW control methods. Agronomists are trialing hybrids with the Agrisure Duracade® corn rootworm trait that features novel, alternate modes of action to help preserve trait durability and delay insect adaptation. The Grow More Experience site is also comparing Force® brand insecticides in their trial to see what additional control they offer.

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All photos are either the property of Syngenta or are used with permission.

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