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Issue No. 6, Article 2/May 1, 2009

Late Planting of Corn and Potential for Insect Problems

With only 4% of the corn acres in Illinois planted as of April 26 and with more rain in the forecast, the effect of planting date on the potential for insect injury will be a question asked shortly after considerable acreage of corn is planted. Because we got off to a similar start in 2008, we addressed this issue in an article in issue No. 7 (May 9, 2008) of the Bulletin, "Late Corn Planting--How Will Some Key Insects Respond?" We see no reason to recreate the wheel in 2009, so I refer you to last year's article. The relationship between insects and time of corn planting has not changed, so the generalities discussed last year suffice again now. Besides, corn producers have far more important concerns on their minds at the moment.

It is important to note, however, that among the insects listed in last year's article, black cutworm is the one that causes the most imminent concern when corn is planted late. There will be expectations that the chloronicotinyl seed treatments (Cruiser, Poncho) and transgenic Bt corn with traits for control of caterpillars will prevent injury caused by black cutworms. But when infestations of black cutworm larvae are heavy, at least some injury can be expected regardless of preventive control measures, and some injury may be severe. So don't trust your preventive tactic so much that you don't return to the field to check on crop status when black cutworms are in the area. If lots of larvae survive on weeds in a given field and then move to seedling corn after the weeds are killed, the amount of injury can advance from noticeable to significant in a short period. As you know, black cutworm males have been captured fairly continuously over the past 3 weeks in several pheromone traps being monitored in Illinois, and continuous captures of male moths have been reported in neighboring states, too. So, the stage is being set for black cutworm problems this spring, and a lack of vigilance could result in discovering the problem too late.

A final note about black cutworms: Christian Krupke and John Obermeyer, Purdue University entomologists, wrote a really nice "anatomy of a black cutworm infestation" (Adobe PDF) in issue No. 4 (April 24, 2009) of their Pest & Crop Newsletter. The information in their article pertains very well to Illinois conditions.--Kevin Steffey

Kevin Steffey

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