Corn Rootworm Beetles

Jul 20, 2021

Corn rootworm beetles are beginning to show up in corn fields and are causing damage by clipping silks on the corn. The fields to be most concerned with are fields with corn on corn history because these pests lay eggs in corn fields in the fall, and if you plant corn on those fields the following year these eggs hatch and the larvae begin to feed on the roots of corn. Eventually they turn into beetles and emerge from the soil to cause more damage by clipping the silk on the corn plant.

Though corn on corn fields are of utmost concern, if you have a field that has been corn on corn in the past but you put it into beans this year, it should still be considered a high importance field. This is due to extended diapause. Extended diapause is where the eggs of the rootworm beetle do not hatch the year after they were laid and instead sit in the field over the summer only to hatch the following year when you put corn back into that field. Long story short, if you have a history of corn on corn at all, you should be checking all of your corn for these beetles. They can be found on the silks of the corn, and sometimes tucked in the collar of the leaf. You may also see them flying around and mating if populations are very high.

A plane can be lined up to spray these pests off, and should be done as soon as you find the problem, if the field is 2/3’s tasseled out. A fungicide is recommended to lay in with the insecticide to help against other environmental stresses like lack of moisture, although is not necessary to kill the beetles.

Talk to one of your agronomists today if you’d like help looking at fields or if you need to line up a plane.

Jackson Gregory, Belgrade Co-op Agronomist

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