Dutiful cooperators in Indiana have captured an inordinate number of black cutworm moths in the last couple weeks. Indiana researchers believe many of those moths were carried here on a large and powerful weather pattern from the southwest that came to Indiana on March 23.
Black cutworm moths would have little interest in this lean stubble field for egg laying.
After burn-down herbicides, wait at least a week before planting to starve cutworm and/or armyworm larvae.
Black cutworm moths would find this field quite appealing for egg deposition.
Black cutworm moths have also been captured in pheromone traps by cooperators throughout much of Illinois. Many fields across southern and central Illinois have been planted and are beginning to emerge. Corn in the 1- to 4-leaf stages of development is most susceptible to cutting by black cutworm larvae.
Normally early-arriving moths are discounted because they freeze out, but not this year. Indiana is the new Georgia and BCW moths are loving it. Indiana officials have 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.
“I urge producers to look for early signs of leaf-feeding injury that could signal potential cutting of plants by black cutworm in the near future,” says Mike Gray, crop sciences extension coordinator for the University of Illinois. “Even if you planted a Bt hybrid, don't be lulled into complacency. Under heavy infestations, control afforded by some Bt hybrids may be inadequate.”
Fields most at risk for black cutworm injury include those heavily infested with winter annual weeds. Favorite weed targets for egg-laying black cutworm moths include mouse-eared chickweed, bitter cress, shepherd's purse, yellow rocket, and pepper grass, Gray says.
Indiana researchers heard that many fields are being treated with a foliar insecticide at the time of herbicide burn-down. They say they understand the proactive approach, especially with such early planting but farmers should understand that those 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.