There’s a new corn pest that is moving toward Kentucky. It’s called the Western bean cutworm and its moving quickly toward the state from the northwest.

Although it’s called the western bean cutworm, it doesn’t act like a cutworm and it’s a serious pest of corn. In some ways it is like the corn earworm in that it attacks the developing ear and kernels. Since this is the part of the plant we market, we consider this a direct pest, one that attacks the part of the plant we sell.

In 2005, the western bean cutworm had spread across Iowa and had entered northwest Illinois. By the end of 2006, it had spread across much of Illinois and the first moths may reach Kentucky by this summer. Trapping for this new pest will begin this summer in Kentucky.

In terms of the life cycle, it overwinters as a larva in the soil and pupates in the spring. The moths begin to emerge in June through early July. Larvae emerge from the eggs laid on the upperside of the leaves and feed on the upper leaves and tassel before moving to the silks and the ear. In the ear, they feed on the developing kernels. Although they are closely related to other cutworms, they don’t act like other cutworms in corn. When feeding is complete, the larvae drop to the soil. Fortunately, there is only one generation per year.

With corn earworm, only one larva completes development per ear as the larvae are canabalistic. But this is not the case with the western bean cutworm. There can be one or more feeding on the ear, there are examples of ten in a single ear. Unlike the corn earworm that attacks only the tip of the ear, the western bean cutworm can attack the tip, the side or the butt end of the ear.

One important question is will BT corn control this pest. The answer is that there are differences in performance of the BT corn events for corn borer control. But this is one option for western bean cutworm control.

We do not expect to see any problems from this new pest in 2007 in Kentucky, even if it arrives. It will take a year or more to build in numbers before problems in the field are noticed.

For information about corn pests, visit Insect Management Recommendations.

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