David Owens, Extension Entomologist, owensd@udel.edu
Corn
Between April 12 and April 19 we experienced our greatest black cutworm flight of the season in our Harrington trap, enough to kick off a degree day model. Those cutworms should just be large enough now to cut corn according to degree day models (300 degree days following a ‘significant’ flight). Admittedly, this may be old news to some of you and I apologize for not putting in an alert last week. A report was received just this morning from Kent County Maryland of cutworm cutting V2 plants. Scouting alerts have also been made in the last couple of days by Iowa and Pennsylvania.
Cutworm moths like weedy fields to lay eggs into. They are not choosy between weeds and green cover crop. If a field was not burned down a couple of weeks before planting, there is a chance there may be cutworm in it. Scout fields for cutworm now! Cutworm are going to leave rows of circular holes in the leaves before they cut plants. Cutworm damage can be confused with bird damage. In moist soil, birds are going to leave round holes with flat sides and be exactly where the seedling was. They will pull seedlings up to consume the seed. Cutworms do not pull plants out of the ground, but will cut plants and sometimes drag them into perfectly round burrows that can be anywhere in or between rows. Thresholds are 3% cut plants, 10% with leaf feeding, and larvae present. This last point is important, because there are other cutworm species in our area that develop earlier than black cutworm and may cycle out shortly after a field is planted while black cutworm will remain active for a much longer period of time. If a field is deemed to be at risk for cutworm damage, rescue treatments consist of pyrethroids. Apply at the end of the day. Cutworms hide during the daytime in the soil or under loose clods and come back out at night.
Early Season Moth Activity
Many thanks to Joanne Whalen and David Armentrout at UMD for assistance with monitoring pheromone traps. Moth activity continues to be quite low this year. I do not anticipate significant true armyworm activity. Black cutworm is a bit more of an enigma and we DO NOT have thresholds based on pheromone trap.
| Location | # of Nights | Total Catch | |
| TAW | BCW | ||
| Salisbury, MD | 7 | 0 | 0 |
| Seaford, DE | 8 | 0 | 17 |
| Sudlersville, MD | 7 | 0 | 8 |
| Harrington, DE | 9 | 4 | 16 |
| Smyrna, DE | 9 | 1 | 2 |
Soybean
This weekend is going to be critical for soybeans, both in terms of slugs and seedcorn maggot. While flies shouldn’t be as active right now as they were, cool, moist weather puts beans at risk in tilled fields. These seeds should have an insecticidal seed treatment. In no-till or minimal -till fields, slugs are the primary threat. Scout emerging beans closely and carefully. If slug feeding looks significant (seedlings permanently bent over, lost cotyledons, perhaps lost growing point) and are beginning to cause stand loss, an application of Deadline (metaldehyde) or the various iron phosphate baits. A 10 pound rate of Deadline should result in about 5 or so pellets per square foot.