Look at this week’s “Black Cutworm Adult Pheromone Trap Report.” Do it now. Our dutiful cooperators have captured an inordinate number of moths these last couple weeks. We suspect many of those moths were carried here on a large and powerful weather pattern from the southwest that came to Indiana on March 23. Normally we discount these early arriving moths, because they freeze out…not this year. Indiana is the new Georgia and BCW moths are loving it. We’ve begun tracking heat unit accumulations to predict future cutting by this pest, which will be published in future issues of the Pest&Crop.
What fields will egg-laden black cutworm moths arriving in your area find 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 cutworm’s least favorite foods, it just so happens it is the only plant remaining by the time larvae have emerged and weeds have been killed. A window of weed-free ground before planting is an ideal solution. Cutworm larvae starve if weeds are treated with tillage or herbicide 2-3 weeks before corn emergence. However, with this season’s compression of field activity, this is unlikely to happen.
As many producers learned last year with a black cutworm outbreak, seed-applied insecticides do not offer satisfactory control under high pressure. In addition, some varieties of Bt-traited corn do not perform well, those are cases where the label provides only “suppression” and not “control.” Check the fine print on the trait you are using! Weak performance (suppression) is fine under ideal environmental conditions and zero to low-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., cooler soils) the efficacy of these control products are greatly reduced, leaving the struggling seedling vulnerable to attack by above and below ground insect pests. Admittedly, cooling of soils doesn’t seem likely this spring.
We’ve heard that many fields are being treated with a foliar insecticide at the time of herbicide burn-down. We can understand the proactive approach, especially with such early planting. Understand that these insecticides have their limitations, specifically when subjected to sunlight, rainfall, heat, and dust. Claims of multiple weeks of control with foliar insecticides in spring conditions are simply unfounded; 7-10 days of control is the most optimistic measure. Remember that these are contact insecticides, and as soon as they hit the soil, breakdown begins. Don’t panic - we can manage this pest effectively and have done so in the past: Timely scouting and rescue foliar insecticides when necessary are the tried and true approach with black cutworm. Happy scouting!