Channel Field Check Up Series: Prioritize fields for corn rootworm checks

Flashing fireflies in the grass around corn and soybean fields has historically signaled that conditions are right for corn rootworm egg hatch. Field evaluations for corn rootworm larvae should be done in late May through mid-June, around the time that growing degree days accumulate to 684 to 767 with a base temperature of 52 degrees. Your Channel Seedsman will check for corn rootworm during a Field Check Up Series visit.

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

In Illinois, farmers should consider managing for corn rootworm on all of their corn acres, especially corn-on-corn fields. Fields that were planted to corn in 2020 are at a higher risk to encounter corn rootworm feeding in 2021.

Practically speaking, it’s tough to control corn rootworm larvae after finding the pest in a cornfield. Proactive management plans, such as using Bt-traited corn products with multiple below-ground modes of action, are effective at protecting against yield loss from corn rootworm.

Next year, the first corn product with three modes of action for corn rootworm control will be introduced. The new combination has the proven benefits of available corn insect control technologies along with a novel RNAi-based mode of action, providing improved control of corn rootworm and other corn pests over a range of pressures. See your local Channel Seedsman to learn more.

University trials have shown that every root node damaged by corn rootworm larvae feeding decreases yields up to 20% and a modest infestation of the pest can lead to a potential yield loss of 15% to 45%.

Fields with a high potential of an infestation should be prioritized for field evaluations and include those planted without soil-applied insecticides, those without Bt corn rootworm protection and those with single modes of Bt protection.

Visit the Channel.com Agronomy Library for articles about managing corn rootworm. Also, InsectForecast.com is a great resource for information about corn and soybean insect migration patterns and activity.