Status Update on the Cornbelt's Most Wanted

Status Update on the Cornbelt's Most Wanted

Mike Gray notes farmers need to be sure they are scouting for European corn borers.

In last week's issue of The Bulletin, University of Illinois entomologist Mike Gray put together a summary of pest observations across the state. Here they are, in his own words.

Japanese Beetle

On June 10 Robert Bellm, crop systems extension educator, reported his first captures of Japanese beetles for the season. The beetles were caught in Madison County in southwestern Illinois.

It's too early to predict with certainty the densities of this perennial insect pest this year across the state, but recall that last year's numbers were low compared with 2009. You can find more information on the biology and management of Japanese beetles on the IPM web site.

European Corn Borer

Many producers undoubtedly have forgotten about the European corn borer; densities have been historically low in recent years as a result of the widespread use of highly effective Bt hybrids against this pest. Consequently, most commercial cornfields are not scouted for this insect.

During June 11 and 12, Mike Roegge, crop systems extension educator in Adams and Brown counties, scouted a non-Bt cornfield. I think his observations confirm the need to treat the European corn borer with some respect if Bt corn has not been planted.

Mike examined 20 plants in each of four locations in the field and found 3, 5, 6, and 7 second-instar larvae. Scouting and traditional management strategies for European corn borers probably need to be reviewed if you are growing non-Bt corn. For more information about european corn borer, please refer to the IPM web site.

Corn Rootworm

Corn rootworm larvae have hatched. For many years, Purdue University entomologists have invested time to pinpoint just when this process begins. Recently the group reported the first observation of larvae on June 9 in central Indiana. They speculated that the initial hatch was most likely on June 6.

Hatch will continue over the next several weeks, with the first adults likely to emerge sometime in late June through early July. Entomologists throughout the Corn Belt are eager to learn what the densities of this pest will look like this summer. Without a doubt, producers the past few seasons have witnessed very low numbers of western corn rootworms.

It will be interesting to see if this trend persists into next year, when even more of the landscape will be planted with Bt hybrids deployed as seed mixtures (Bt and non-Bt seeds). If you see unusual levels of root damage to Bt corn this season, I would be interested in learning about your observations.

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