Iowa State University Extension and Outreach

East-Central and Southeast Iowa Crop Information


May 12, 2004

The Time to Scout for Black Cutworms is Near

Black cutworms do not over winter in Iowa. Rather, if black cutworm moths fly in from the south and if they stay around long enough to lay eggs, young corn plants may be injured. Significant flights occur very regularly, but damage at a treatable level generally occurs less than once per decade. If eggs are laid, the hatch date can be fairly closely predicted by monitoring temperatures. A series of black cutworm moth traps is set up around Iowa and Illinois to monitor moth flights. There was a moth capture event that was one moth short of being significant on April 19 and then many significant captures on April 21 and 22. Working off of the April 19 date (which is very conservative), considering the temperatures we have experienced since then, and projecting normal temperatures ahead for the next few days, cutting should begin in areas near and south of Highway 92 (Burlington, Mount Pleasant, Wapello, etc.) on May 15. North of Highway 92 (including Cedar Rapids, Clinton, Iowa City, Maquoketa, Muscatine, Quad Cities, Tipton, etc.), cutting should begin on May 18. Working off of the April 21 captures would back the dates off to May 17 along and south of Highway 92 and May 20 north of Highway 92. It is best to start scouting corn fields a couple of days before the projected cutting date. Because there have been several moth flights since the first ones, continue scouting corn fields until they reach the five-leaf stage (V5). For information on scouting procedures and thresholds, see pages 61 - 63 of the May 8, 2000 Iowa State University Integrated Crop Management Newsletter.


If you have any questions, please feel free to contact the Iowa State University Extension Office.

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Last Update: May 12, 2004
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