February 24, 2005 | By: Laura Skillman

Market conditions and possible damage from soybean rust have producers looking away from traditional crop rotation patterns and toward continual corn production within fields. As farmers look to this production plan, they need to consider how this practice will impact insect pest management this year.

“It seems that more of our producers are getting away from rotating crops and are favoring – or the economics, to them, seem to favor – growing more corn, meaning two or three years of corn rather than rotating corn and soybeans or corn, wheat and soybeans,” said James Herbek, UK grains specialist. “Most of our farmers were doing some kind of rotation but now are growing more second and third year corn.”

It is well established that rotating crops provides a yield increase, he said, while continuous corn results in yield decreases. This is probably due to less disease, insect and weed pressure in rotated crops because the cycle is being broken and they aren’t allowed to build up.

“As always, crop rotations and planting dates will be a major determining factor for insect problems this year,” said Ric Bessin, an entomologist with the University of Kentucky College of Agriculture. 

Corn producers who have been growing continuously on the same ground should watch for Western and Northern corn rootworms, he said.

“It is a very destructive pest that is almost completely controlled through crop rotation,” Bessin said.

Throughout the state, the stripped Western corn rootworm is more common than the spotless Northern. The Southern is spotted but rarely found in corn in economic numbers. Rootworm eggs laid in last summer’s cornfields will hatch in late spring and the larvae will feed on the root systems of young corn plants. 

Generally, the second consecutive year a field is planted in corn increases the potential for rootworms slightly, but each subsequent year the field remains in corn the risk of economic loss due to rootworm increases, Bessin said.

Farmers are advised to use a corn rootworm seed treatment or a soil insecticide at planting or use a Bt rootworm corn if you are growing continuous corn and you noticed an average of at least one beetle per plant last summer. In fields where something other than corn was grown last year, no control is needed for corn rootworm.

If a soil insecticide will be used, planters will need to be calibrated this spring. During calibration, equipment should be examined and repaired if necessary. There are liquid and dry insecticide alternatives that are very effective against corn rootworm. If producers decides to plant a Bt corn hybrid, they should be sure to use the proper hybrid for the protection needed.

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

For more information on corn production, contact a county office of the UK Cooperative Extension Service.


Writer: Laura Skillman 270-365-7541 ext. 278

Contacts: James Herbek, 270-365-7541 ext. 205
Ric Bessin, 859-257-7456