Western bean cutworm can be a nasty pest

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Some pests may not affect an entire condition, or they may not show up every year. But just like there is no minor surgery if you are the patient, there is no small pest if you are the one whose field is eaten away. If the western bean cutworm once invades your cornfield, you will never forget it.

Why? Because the pest gnaws several holes, not just one, in the ears of corn, moving through the pods. Food opens the ears to other pathogens. In the right weather conditions, it can also lead to germination and rot directly on the ear. Western bean cutworm can transform an attractive cornfield into what looks like a war zone in no time. Feeding sequelae – including disease, sprouting, and general rot – may be the best reason to mark an infested field for an early harvest.

Prevention and control

For several years, the farmers where the western bean cutworm occurs most often kept it at bay with Bt features that protect against damage from aerial feeding by insects. However, Purdue University entomologists John Obermeyer and Christian Krupke, reporting in the July 28 edition of the Purdue Pest & Crop newsletter, let’s say that not all traits are as effective against western bean cutworm as they once were.

“Control of this pest with Bt Characteristics of corn is difficult because it has developed resistance to one of the toxins found in most treated corn, Cry1F, the endotoxin for caterpillars that feed on the surface, ”they write. “This includes SmartStax varieties and Optimum AcreMax hybrids, among others. In terms of Bt hybrids, only those expressing the VIP The protein will provide control of this pest – something to keep in mind when ordering seeds for 2022. ”

If field scouting and timely insecticide applications are your only options for managing western bean cutworm, those options work well, entomologists note. However, you must research and make timely insecticide applications before the insects are in a position where they are difficult to control.

The Purdue University Corn & Soybean Field Guide suggests examining 20 plants in five areas of the field and looking for egg masses on the upper surface of the upper leaves, or larvae feeding in the whorl or on the pollen at the armpit of leaves. Eggs can be unevenly distributed across a field, so you need to check different areas, entomologists note. If 5% of the plants have an egg mass or larva in the whorl, treatment is recommended. The larva you are looking for has two distinct dark rectangles immediately behind an orange colored head. Once the larvae are inside the ears, they are protected from an insecticide.

At this point, you probably need to plan the field for an early harvest and check with your seed rep for hybrids with a GMO trait that is still effective against the pest.

You can follow more information on trapping reports and suggestions on western bean cutworm and other insects in the Purdue Pest & Crop Newsletter.


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