Dry Beans XIII-4

Western Corn Rootworm

Gary L. Hein & Frank B. Peairs

Western corn rootworm larva, left; adult, right.

The western corn rootworm is only associated with dry beans when they move from adjoining corn to feed on bean leaves.  Control measures are seldom warranted for this insect in dry beans.

Identification (and life cycle/seasonal history)

The western corn rootworm is about ¼ inch in length and has a light yellow to green wing cover with three longitudinal black stripes.  They only survive in continuous corn where corn is planted back to corn the following year.  Eggs overwinter in the soil and hatch the following summer.  Larvae are able to survive only on corn roots.

Plant Response and Damage

The beetles move into beans from adjacent corn and strip the epidermis of leaves, leaving only the lacy appearing cuticle.  This damage resembles Mexican bean beetle damage. 

Management Approaches

Western corn rootworm beetles can become a problem on dry beans when heavy populations of rootworms develop in adjacent fields of continuous corn, and beetles move to the beans to feed on leaves.  Populations of this insect will rarely become significant in beans, and most often are confined to the borders immediately next to the corn.

Products for Corn Rootworm Adults:
Insecticide	Product per Acre	Preharvest Interval , remarks
Asana XL^R1	5.8-9.6 oz./A	PHI 21 days; REI 12 hrs.
Mustang MAX^R1	2.72-4.0 oz./A	PHI 21 days; REI 12 hrs.
lambda-cyhalothrin^R1 (Warrior, generics)	2.56-3.84 oz/A	PHI 21 days; REI 24 hrs.
The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.

Categories: Dry Beans, Western corn rootworm

Date: 04/24/2006