Information Management to Maximize Your Yields

Black Cutworm Scouting Advisory 2011

Several peak flights of black cutworm moths have been reported by cooperators in various parts of Iowa this year. Our cutting date predictions (the date when black cutworm larvae are likely to be causing damage in corn) are based on the first peak flights which took place from April 6-9. The map (Figure 1) shows the predicted cutting date for each region.

Trap data shows that moths have continued to come into various parts of the state at peak flight levels during the middle and later parts of April. Because of this, black cutworm larval activity in Iowa may occur for an extended length of time and growers are urged to scout fields on a regular basis as scouting is the only way to tell if a field is infested by black cutworm larvae.

Figure 1. Estimated black cutworm cutting dates for each Iowa climate division based on the first recorded peak flights of moths occurring in 2011. Scouting should begin several days before the predicted cutting date.

The estimated cutting dates for the climate divisions in Iowa are as follows: May 15 in the southwest; May 17 in the south central and southeast; May 19 in the west central and east central; May 20 in the central; and May 22 in all three northern divisions. These predictions are based on actual and historical degree day data accumulated from the dates of the first peak flights. Scouts are encouraged to start looking a few days before the estimated cutting dates as development in some areas may be sped up (or slowed down) by localized climate conditions.

Preventative black cutworm insecticide treatments applied as a tank-mix with herbicides are of questionable worth. Black cutworm is a sporadic pest and therefore every field should be scouted to determine the presence of the insect prior to spraying insecticides.

Figure 2. The black cutworm (top) can be confused with the dingy cutworm (bottom). By Adam Sisson, Corn and Soybean Initiative; Laura Jesse, Plant and Insect Diagnostic Clinic; and Erin Hodgson, Department of Entomology

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