Prioritize Fields For Corn Rootworm Checks

DANIEL PHELPS

NORTH PLATTE, NEB.

   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 F. 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 low populations the following year.

   In Nebraska, farmers should consider a crop rotation program if possible. Crop rotation breaks the life cycle of insects that have limited mobility and limits host plants for feeding. If rotation is not possible in-furrow insecticides, seed treatments and proper corn technologies will need to be considered.

   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 Bt- 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 Seedsman to learn more.

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

   DANIEL PHELPS: Channel Technical Agronomist