The 2017 Illinois Cooperative Agricultural Pest Survey Program has started and cooperators are reporting high captures of Black Cutworm moths and True Armyworm moths in their pheromone traps. Recent articles in the Purdue University Pest & Crop Newsletter have highlighted the same findings in Indiana as well.
Black Cutworm moths are attracted to fields with green growing plants to lay their eggs, and this year we have many fields that are still green with growing winter annuals. It is estimated that the first Black Cutworm larval feeding may be expected close to the time of May 11.
On the other hand, True Armyworm moths are attracted to fields with grassy plants for their egg laying, such as pastures, small grains and grass cover crops. If we continue to collect growing degree days at the current rate, and if you have planted corn into a small grains cover crop which was not controlled two weeks prior to planting, then these fields are possible candidates for True Armyworm larval leaf feeding and should be scouted.
The reasons for my concern are the high trap count numbers and mild winter weather have led to a large number of fields being attractive sites for moth egg laying. With the advent of Bt traited corn hybrids, it is easy to think that we are safe for caterpillar feeding, since Bt (Bacillus thuringiensis) kills all caterpillars. Is not that correct? WRONG, while the Bt traits containing the proteins Cry 1F and Vip3a will provide control for light to moderate infestations of Black Cutworms. If you experience moderate to high infestation then damage will be noticed. The only Bt protein effective against the True Armyworm is the Vip3a protein.
If you planted corn into a field that had a heavy cover of winter annuals, this is the year to spend a little time to monitor that field to make sure the corn is emerging and not being attacked one of these pests. If you have questions, you can contact me at 217.877.6042, firstname.lastname@example.org, visit go.illinois.edu/dmp, or on Twitter @SoilWaterDoug.