While in westcentral Iowa yesterday setting up some small plot experiments, I got distracted by a long stretch of grass alongside a cornfield. I noticed some “deadheads” among the green plants and decided to dig a little deeper.
I pulled up some of the dead head plants and noted holes about half-way down the plant.
I used a knife to spilt the stalk just above the hole and a very unhappy caterpillar was inside.
The caterpillar, known as common stalk borer, was about an inch in length and had a purple “saddle” on the thorax and an obvious orange head. Yes, I am taking donations for a moisturizing hand cream!
The caterpillar pretty much filled up the inside of the stem and had created copious amounts of sawdust-like frass.
Based on accumulating degree days estimated by a recent ICM News article, I would expect stalk borers to move to corn and soybean in central Iowa next week. The only time to act is when the caterpillars are exposed, moving from grass to crops. Take a look at field edges now, especially in areas with previous stalk borer infestations.
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- Extension Entomologist Specialist
- ANR Crops Team Leader