![]() Flag areas with suspected BCW feeding and return later to assess further injury. BCW larvae sometimes drag cut plants under soil clods to continue feeding during the day. Look for wilting, leaf discoloration or damage, and missing or cut plants (Figure 4). BCW scouting can easily be combined with stand counts and scouting of other early-season pests.Įxamine 10 corn plants in five areas of the field (50 total plants). Begin scouting several days before estimated cutting dates early scouting is important because local larval development varies due to weather variation within a climate division, and regular scouting is important because additional flights could prolong the presence of BCW larvae in a field. Photos by Adam Sisson.įields should be scouted every 7-10 days until corn reaches V5. Corresponding tubercles on dingy cutworm are about the same size. For black cutworm, the tubercles nearest the head on each segment are about 1/3 the size of the tubercle closest to the rear. Black cutworm (left) can be distinguished from other larvae, such as dingy cutworm (right), by the dark tubercles along their bodies. Black cutworm larvae have grainy and light grey to black skin. The Field Crop Insects publication from the ISU Extension Store can aid in identification of other cutworm species.įigure 2. On each body segment, the tubercle closest to the head is about 1/3 the size of the tubercle closest to the rear for BCW the corresponding tubercles on each segment for dingy cutworm are roughly the same size. The tubercles are used to distinguish BCW from other similar cutworm species, like dingy cutworm (Figure 3), that rarely cause economic injury in corn. There are pairs of dark tubercles, or bumps, along the sides of the body. ![]() IdentificationīCW larvae have grainy, light grey to black skin and four pairs of fleshy prolegs at the end of the abdomen (Figure 2). Scouting fields is the only way to determine if BCW are present and whether management is warranted. Estimated black cutworm dates for each Iowa crop reporting district based on peak flights during April.Ĭapturing BCW moths in a pheromone trap does not necessarily mean there will be economic infestations in a particular location. Keep up with the Iowa Moth Trapping Network by subscribing to the ICM Blog or checking the maps on. BCW trapping will continue throughout May, and any additional peak flights that occur will be included in our weekly ICM Blog updates. These cutting dates are estimated by combining actual and historical GDD data. Counties that have reported significant flights include Mahaska (April 8, 12, and 30), Benton (April 8), Carroll (April 29), Pottawattamie (April 29), O’Brien (April 8), Washington (April 9), Taylor (April 8, 18, and 26), and Monona (April 9).įigure 1 shows the predicted cutting dates for BCW in each crop reporting district. Significant flights have occurred in most areas of the state. You can read more about what a significant flight means in the Week 2 Update for the Iowa Moth Trapping Network, and an introduction to the 2021 Iowa Moth Trapping Network can be found here. We can predict when black cutworm will reach the 4 th instar based on accumulating degree days and when a significant flight occurred. Larvae must attain a certain size (4 th instar) to be large enough to cut corn plants, and cutting can occur until plants reach the V5 stage. Since much of the corn planting around the state is complete and many fields have emerged, now is a good time to begin scouting for larvae.īCW moths lay eggs in and near crop fields, and larvae can feed on leaves or cut corn seedlings. It is sporadic and unpredictable, making it essential to scout to determine whether BCW larvae are present in a field and management is required. ![]() Black cutworm (BCW) is a migratory pest that arrives in Iowa with spring storms each year.
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