Black cutworm finding Hoosier hospitality
• Black cutworm moth arrival has never been higher.
• Moths are seeking weedy fields to lay their eggs, plenty to choose from.
• Seed insecticides and traited-corn may be little help if cool, wet conditions persist after planting
Look at this week’s “Black Cutworm Adult Pheromone Trap Report.” Our dutiful cooperators have captured an inordinate number of moths these last couple weeks. As of April 15, we’ve begun tracking heat unit accumulations to predict future cutting by this pest, developmental map published in future issues of the Pest&Crop.
The key question is: will egg-laden black cutworm moths arriving in our fair Hoosier state find your fields attractive to lay eggs in? There are some clues that help give us an answer: Barren fields are not appealing. Moths are particularly attracted to winter annuals, such as chickweed and mustards. But the black cutworm has a broad host range, and fields that are showing plenty of green, yellow, and purple (henbit) are at highest risk for cutworm damage. Remember, corn is one of the black cutworms least favorite foods, it just so happens it is the only plant remaining by the time larvae have emerged and weeds have been killed. Cutworm larvae starve if weeds are treated with tillage or herbicide 2-3 weeks before corn emergence. It is obviously too late for that this year.
We don’t want producers to have a false sense of security with seed-applied insecticides and some varieties of Bt-traited corn, where the label provides only “suppression” and not “control”. Check the fine print on the trait you are using! Suppression is fine under ideal environmental conditions and moderate infestation levels. The systemic activity of the seed-applied insecticide, and/or the protein production of the Bt-corn are optimal when the corn seedling is actively growing. However, under environmental stress (i.e., yellow corn, cold and wet soil) the efficacy of these control products are greatly reduced, leaving the struggling seedling vulnerable to attack by above and below ground insect pests. We will continue to update in coming weeks and include scouting and treatment guidelines in future articles. For now, we will wait and see – with only 2-5% of the corn planted in the state, it will be some time before we see damage.