No. 4 Article 3/April 17, 2009

A Rather Steady Flow of Black Cutworm Moths

Since our first report of captures of black cutworm moths in pheromone traps (issue no. 1 of the Bulletin, March 19), we have received a rather steady flow of capture reports. This is not surprising given the storm fronts that have passed through Illinois over the past couple of weeks. Black cutworm moths take advantage of these weather systems to migrate into the state. When the females "drop out" into Illinois (and elsewhere in the Midwest, for that matter), they seek sites for oviposition, often fields with winter annual weeds.

We have received reports of intense captures of black cutworm moths (9 or more moths in a 1- to 2-night trapping period) from four locations on the following dates: April 4 (Piatt County), April 10 (Brown and Lee counties), and April 14 (Marion County). These intense captures can be used to trigger projections for the first signs of larval cutting activity in prescribed locations. For example, if you visit the "Degree-Day Calculator" page at the at the Water and Atmospheric Resources Monitoring Program (WARM) website, you can choose black cutworm and the Perry weather station to determine when cutting likely will occur based on the intense capture in Brown County (April 10). On April 15, I entered the date of the intense capture (April 10) and learned that the projected date of 300 degree-days (above a base temperature of 50°F) was May 17. (First cutting by larvae usually is observed when approximately 300 degree-days have accumulated.) Similar information submitted for the intense capture in Marion County (April 14) suggested that the projected date of 300 degree-days in the Fairfield area was May 12.

So mid-May is currently our target for ramping up scouting efforts for black cutworms. However, it's not a bad idea to plan for scouting even earlier. Before cutting occurs, early signs of black cutworm activity--pinhole feeding injury on seedling leaves--can prepare you for something more serious. For more detailed information about black cutworms, go to the "Black Cutworm" fact sheet at our IPM website.

All of this speculation about black cutworms, however, also depends on dates of corn planting. If the weather cooperates soon and the percentage of acres of corn planted increases dramatically over the next couple of weeks, we'll soon be in the thick of black cutworm larval activity. We'll talk more about management of black cutworms in future issues of the Bulletin.--Kevin Steffey

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