Once a Purdue University Extension weed control specialist based on the Purdue campus, Dan Childs is now in private industry. But he's still chasing pests, this time it just happens to be an insect. Childs has been studying the western bean cutworm carefully. Childs, with Heritage Seeds, passed along some of his observations for use in the most recent edition of the Purdue Pest & Corp Newsletter, Issue 16, distributed by email and posted on the Web weekly by the Purdue University Entomology Department staff.
Childs notes that when moths first were caught this year, they were in the more typical, sandy areas of northwest Indiana. However, later they branched out into 'good dirt areas,' considered fringe areas for the insect.
The insects prefer shoulder high corn. Childs finds them most often in the whorl. He hasn't found many egg masses in fields that were actually pollinating. Entomologists suspect that's because the moths don't like to lay eggs in corn once tassels emerge. Their strong preference is pre-tassel corn.
Egg masses will be of different colors, including cram, purple and white, all in the same field. At the same time, some egg masses in the field may have already hatched. All belong to the same insect- the western bean cutworm. You will almost always find them on the upper surface of leaves, unlike some other insects, that lay eggs on the underneath side of leaves of various plants. However, you may find them on the sheath beneath an upper leaf, Childs observes.
Form where eggs are found, it appears female moths not only prefer young plants without tassels, but also young leaves. Egg masses are most often found on leaves that stick upward, or that are not fully out of the whorl yet. Thee leaves aren't usually considered mature at that point.
This isn't an insect where you can scout and find egg masses on every plant, Childs adds. That's what makes scouting extra tough and frustrating. From what he's seen so far this season, you may find three to four egg masses in a cluster of 10 to 15 plants, then not find anymore for a long section of that row.
Weirder yet, he often doesn't find any egg masses in fields where the trap was located indicating a high catch of moths. Instead, he may find the egg masses in a field down the road. In fact, the egg masses may be so prevalent in that field down the road that it is over the threshold for treatment. The threshold is based on economics- expected yield loss vs. cost of product and application cost.
Continuous corn tens to have more egg masses and higher trap counts this year, Childs adds. If a field is already pollinating, be it after corn or soybeans, egg masses are likely to be on end rows where corn is shorter and under more stress in many situations.
There are predators that eat these insects. However, they haven't yet been found in large numbers this season, Childs concludes.