Prioritize Fields For Corn Rootworm Checks

MIKE MULLINS

 ST. LOUIS, MISSOURI

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 are suggested 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 F.  

 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 Missouri, farmers should consider conducting root digs as well as using sticky traps to determine the average number of beetles they might have in their respective area. This in turn will help determine what the egg-laying population might be the following year.

 Practically speaking, it’s tough to control corn rootworm larvae after finding the pest in a cornfield. Proactive management plans are the most effective against yield loss from corn rootworm with B.t.-traited corn products with multiple modes of action. 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 SeedPro 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 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, no B.t. corn rootworm protection or those with single modes of B.t. 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.

 Legal:

ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS.

Performance may vary, from location to location and from year to year, as local growing, soil and environmental conditions may vary. Growers should evaluate data from multiple locations and years whenever possible and should consider the impacts of these conditions on their growing environment.

The recommendations in this material are based upon trial observations and feedback received from a limited number of growers and growing environments. These recommendations should be considered as one reference point and should not be substituted for the professional opinion of agronomists, entomologists or other relevant experts evaluating specific conditions.

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MIKE MULLINS: Channel Agronomist