Black cutworm larval activity in Iowa may occur for an extended period of time this season, according to data collected from black cutworm traps in 64 Iowa counties. Fields of higher risk to black cutworm include those that are poorly drained and low lying; those next to areas of natural vegetation; and those that are weedy or have reduced tillage. Black cutworm also may cause more damage in fields where corn is planted later.
In a recent Integrated Crop Management News article, Iowa State University Extension entomologists urge corn farmers to scout fields weekly until the corn reaches V5 stage. Examine 50 corn plants in five areas of each field. Look for plants with wilting, leaf discoloration and damage, and those that are either missing or are cut off at the soil surface. Note areas with suspected damage and return later to assess further damage. Larvae can be found by carefully excavating the soil around a damaged plant.
“What if you’ve applied an insecticide mixed with a herbicide when you made your weed control application? Should you still scout for cutworms? ‘The answer is yes,’ says Erin Hodgson, an Iowa State University Extension entomologist, in a recent Wallaces Farmer article. ‘Actually, preventative black cutworm insecticide treatments applied as a tank-mix with herbicides are of questionable worth. Black cutworm is a sporadic pest and therefore every field should be scouted to determine the presence of the insect prior to spraying insecticides. The scouting and rescue treatment approach is the best strategy’.”
To help determine the threshold for treatment, the ISU Corn-Soybean Initiative has developed an Excel spreadsheet to serve as a dynamic decision-making tool.