Be on the Lookout for these Corn Insect Pests

Adult Corn Rootworm (CRW) Beetles

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Figure 1 and 2

Figure 1. (Left) Adult CRW beetle. Figure 2. (Right) CRW beetles feeding on corn silks.

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Beetles prefer to feed on corn silks, but can also damage leaves, pollen, and tassels. High levels of CRW during silking can result in decreased pollination and ear fill. Foliar insecticides should be considered when beetle counts of 5 or more per plant are found, fewer than 75% of the plants have emerged silks, and clipped silks are present. Insecticide application can also help reduce the number of eggs laid in a field. Synthetic pyrethroids are not recommended as they can kill beneficial insects that help control spider mites. Crop rotation should also be considered as a measure to help control CRW.

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Corn Earworm

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Figure 3

Figure 3. Corn earworm feeding on a corn ear tip.

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Moths fly in and deposit eggs on leaves and silks shortly after tasseling and on developing silks prior to pollination. Larvae tend to emerge after pollination has occurred. They will feed on kernels at the tips of ears, typically not causing economic damage. Control is challenging, as insecticides would need to be applied repeatedly during silking. Control is not recommended due to inconsistent results and the high costs of insecticide application.