Western and northern corn rootworms are serious corn pests in Iowa and the Corn Belt. These pests readily adapt to management tactics, especially in continuous corn production. The larvae consume corn roots, thereby reducing nutrient and water uptake, and cause stalk lodging. The adults may also feed on above-ground parts of the plant, including silks and pollen, which may interfere with pollination.

Between May 4 and May 10, 19 trap sites reported a total of 39 black cutworm moths captured in traps (Figure 1). There were no additional significant flights during the week (Figure 2).

Using historical temperature data from the Midwest Regional Climate Center database, Table 1 shows the current projected cutting dates in counties that have had a significant flight. 

Over the last week, there was a lot of field activity across the state—planting, spraying, rotary hoeing, and fertilizer applications. Early planted corn and soybean fields have emerged, but there are concerns about soil crusting impacting emergence and stands. Insect activity is starting to increase, with reports of alfalfa weevil larvae and cutworms.

Early-season field conditions can set the tone for the entire growing season. Two common soil issues that can limit early crop development are soil crusting and sidewall compaction. While they look different in the field, both restrict crop establishment and early root growth, reduce early vigor, and can make crop stress symptoms show up sooner and more severely.

“Cutworm” is a common name for many caterpillars in the moth family Noctuidae. They are insects (not worms!) that chew, or cut through, plants above or below the soil line in the spring. One notable exception is the western bean cutworm, which occurs later in the season and targets reproductive tissues rather than cutting stems.