By Ric Bessin, Extension entomologist
University of Kentucky

Corn prices and soybean prices remain volatile, and soybean rust is now a concern in our state. Many are considering having more corn follow corn than they have in the past.

But a question that growers should ask themselves is, how will this impact insect pest management for 2007? As always, crop rotations and planting dates will, in part, be a major determining factor for certain insect pest problems this year.

Corn growers that have been growing corn continually on the same ground should watch for western or northern corn rootworms. Throughout the state, the spotted western corn rootworm is much more common than the spotless northern.

Typically, crop rotation is the most effective means of controlling these pests. Eggs laid in last summer's corn fields will hatch in late spring and the larvae will feed on the root systems of corn plants.

Generally, keeping a field in corn a second year only increases the potential for rootworms slightly. This is not a reason to switch to higher-priced seed and other inputs without assessing rootworm risk in each field. But each year that a given field is kept in continuous corn, the risk of economic losses to corn rootworms slowly increases.

So how do you decide if you need to control corn rootworms in your corn this year?

You are advised to use a rootworm seed treatment (Cruiser Extreme Pak Rootworm, Poncho 1250, or Prescribe), a soil insecticide at planting, or plant Bt-rootworm corn (YieldGard Rootworm, Herculex RW) if you are growing continuous corn and you noticed an average at least of one beetle per plant last summer. In fields where something other than corn was grown last year, no control is needed for rootworms. When experimenting with new technologies or input, it is always good to leave a test strip through the field to compare the value of the new input against.

If a soil treatment will be used, planters will need to be calibrated next spring. During calibration, the equipment should be examined and repaired as necessary. There are liquid and dry insecticide alternatives that are very effective against corn rootworms.

Bt-corn hybrids that protect against corn borers only will not provide any control of corn rootworms, be sure to use the proper type of Bt corn to match the protection needed.

Seed treatments can be convenient in that no calibration is need and several pests can be managed.

SOURCE: Kentucky Pest News newsletter.