Early planted corn is five+ leaves and soybeans V3. The crop stage is variable in fields with emergence issues from flooding and crusting. Highly variable crop stages are likely to concentrate insects in parts of the field later. Some examples are corn rootworm beetles and soybean aphids. Variable planting dates and crop stages can also affect plant disease.
Areas that have been very dry the past couple of years are seeing herbicide carryover (several groups and several crops). Drought, a gift that keeps on giving.
Black cutworms continue to cause concern this year in southern Minnesota crops this spring. Large black cutworms can tunnel into the crowns of larger corn (V5-6) and sugarbeets. The reports I’ve received of injury to corn have been from fields that are high risk based on planting date and early season weeds planted to hybrids without an above-ground Bt trait labeled for black cutworm.
(https://www.texasinsects.org/uploads/4/9/3/0/49304017/bttraittable_feb_2023.pdf.) Larvae from moths arriving in April should begin to pupate next week, larvae from mid-May flights will be active longer. Don’t ignore signs of black cutworm injury in soybeans. Some fields, particularly weedy fields, may have very large cutworm populations.
True armyworm larvae have also been observed across a wide area of southern Minnesota. Most of these have been in field borders and grass hay fields (e.g., Redwood, Sibley, McLeod, Olmsted, and Winona Counties). There have also been reports of infestations in corn planted into rye. I have received a report of buffer sprays in corn adjacent to grassland also. Thanks, Curt. Pheromone traps in NW Minnesota just detected a large armyworm moth flight so potential armyworm problems are not limited to southern Minnesota.
Remember, every field will be different, and it is worth scouting for cutworms and armyworms this year. Scout first and treat only where needed. An armyworm rate of a pyrethroid or other labeled insecticide should be effective on both cutworms and armyworms.
At the SWROC, corn rootworms have accumulated 464-degree days (base 52) at the 4-inch soil depth. The corn rootworm egg hatch should be beginning. Eggs hatch of western corn rootworm starts around 380 DDs and peak hatch occurs at 684-767 DD. In a strange coincidence, I just received a report of fireflies in South Central Minnesota.
The timing of egg hatch will vary by rootworm species, soil type, residue, and the depth of eggs in the soil profile. I would wait until after the peak egg hatch for most rootworm work. I may still have a few sets of sticky traps available for beetle scouting, let me know if you are interested.
Happy trails,
Bruce