Channel Field Check Up Series: Corn rootworm management requires vigilance

It’s tough to control corn rootworm larvae after finding the pest in a cornfield. Proactive management plans are the most effective protection against yield loss from CRW, and vigilance is key to controlling the pest that has been estimated to cost our nation’s farmers $1 billion in crop damage and insect control tools annually.

An annual evaluation of CRW infestations in corn and soybean fields is important because populations can build rapidly and are influenced by environmental conditions like soil moisture, crop rotation and soil properties. Finding a low population one year does not mean there will be a low population the following year.

Field evaluations for CRW larvae should begin in late May through mid-June, around the time growing degree days accumulate to 684 to 767 with a base temperature of 52 degrees.

During this time, it’s advised to conduct root digs to evaluate the CRW larval population. A second root dig in July or August allows for reassessment of the CRW larval population in addition to providing an opportunity to evaluate the amount of root damage that has occurred up to that point from larval root feeding.

This information is useful for harvest planning as root damage often leads to decreased standability and quicker drydown due to waning plant health from the reduction in water and nutrients being taken up by the plant. Fields with extensive CRW damage should be at the top of the list when planning harvest order.

As the growing season progresses in Illinois, farmers should be aware that this spring’s cool temperatures and wet weather may affect the timing of CRW egg hatch. There’s the possibility of starting field evaluations for CRW larvae too early.

If your early June field checks result in few or no discoveries of CRW larvae, reevaluate fields again in a week to 10 days.

A study detailed in the Channel 2021 Field Research Book demonstrated that CRW beetle numbers in a current growing season could be used to assess the potential risk of CRW larval infestations during the following season.

Another trial comparing corn rootworm traits concluded that a pyramided trait corn product can be effective in protecting yield potential from CRW infestations. If CRW is in your field or your neighbors’ this season, next year’s corn planting plan should probably include a Bt-traited product.

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