INFO-BUG

Crop Selected: Field Corn
Crop Development: Tassel or silk stage.

Biology

Pests Selected:

Northern corn rootworm (NCR), Diabrotica longicornis
Western corn rootworm (WCR), Diabrotica virgifera

Adult corn rootworm beetles emerge in July and early August and after feeding on foliage and pollinating silks proceed to lay their eggs at the base of corn plants. Eggs overwinter in the soil until they hatch into larvae the following spring.

If corn is planted again the following season, the larvae feed on the corn root system causing corn to lodge and reducing grain yield. Thus, rootworm is only a problem on continuous planted corn. An exception is the NCR strain in the north central states, where eggs remain dormant for more than a year. This strain has become a problem in the Dakotas, Minnesota and other states.

Click to see

Roots damaged by rootworm larva Rootworm larvae

Assessment

Corn following corn may or may not have potential for economic rootworm injury. In general, 2nd year corn will have a low potential for rootworm injury if the prior corn crop matured early and was isolated from continuous corn. In contrast, corn following continuous corn is likely to have a significant rootworm injury if no preventive treatment is applied.

The potential for rootworm injury can be predicted by periodic monitoring of adult activity during July and August of the previous season. Peak counts greater than 1 adult beetle per plant in continuous corn or 0.7 beetle per plant in 1st year corn indicate potential levels of economic rootworm activity if corn is planted again in the field being monitored.

Control

Rotation of corn with alternative crops will disrupt rootworm cycle and eliminate the need for soil treatments to prevent rootworm injury.

Soil insecticides available for preventing rootworm injury in continuous corn include the following.

Aztec* 2.1G
Aztec* 4.67 G
Capture* 4EC
Counter* 20CR
Force* 3G
Fortress* 5G
Furadan* 4F
Lorsban 15G
Mocap* 15G
Regent* 4 SC
Thimet* 20G (also called Phorate)

* Use is restricted to certified applicators.

Commercially applied seed treatments labeled for rootworm larval control:

Prescribe
ProShield

| Return to Ohio IPM Home Page. |