University of Illinois

No. 10/May 30, 1997

Sporadic Black Cutworm Injury Reported

This spring has been characterized by very few reports of black cutworm injury to seedling corn plants. Although intense flights of moths have occurred in certain areas of the state, black cutworm larvae have not made a big splash yet. Let's hope they don't. Until fields move beyond the 4-leaf stage of development, continued vigilance in your scouting efforts is well worth the effort. Dave Mowers, of Mowers Soil Testing Plus, Inc., indicated recently that several fields in Peoria County had black cutworm injury with 4 to 5 percent of the plants affected. Ellen Phillips, Crop Systems Educator, DeKalb Extension Center, reported that some cornfields in southern DeKalb and Kane counties had black cutworm injury. Ellen described the injury as noneconomic; however, many late-planted fields will remain at risk for several weeks. Because of the very cool spring, plants will continue to be susceptible to cutting well into the month of June. Bottom line--don't forget about this insect pest as we move beyond May.

Cooperators in our black cutworm monitoring program reported moth captures in 22 counties for the monitoring period of May 17 to 23. Moths were caught in pheromone traps as far south as Alexander County northward to Boone, McHenry, and Stephenson counties. Volunteers also reported captures in western counties, such as Brown, Greene, and Hancock. Not to be left out, the eastern edge of the state also reported moth captures in counties like Clark, Douglas, Iroquois, and Vermilion. This wide distribution of moth captures has been a typical pattern this spring. An intense capture of moths was reported in Ford County on May 22--the only intense capture for the entire state for the most recent monitoring period. Table 1 provides updated information regarding potential cutting dates. Next week will be the last monitoring period for the black cutworm migratory flight of 1997. However, black cutworm larval injury could linger well into the month of June.

Table 1. Potential dates when 300 heat units above 50F have accumulated from an intense moth capture, indicating when black cutworm larvae are large enough (fourth instar) to cut corn seedlings.
Date of intense moth capture (9 or more moths caught over a 1- to 2-day period)County of intense moth captureProjected date when 300 heat units (base 50F) have accumulated from an intense capture
April 28FordMay 31
April 29AdamsMay 28
May 3ClarkMay 30, June 1
May 6PikeJune 1
May 6WayneMay 31
May 7LaSalleJune 3, June 7
May 10OgleJune 9
May 11MonroeJune 1
May 14MaconJune 4
May 14HancockJune 6
May 15LoganJune 4
May 22FordJune 9
Note: Two dates may be listed for the same county if the heat-unit accumulations were generated from different Illinois Climate Network sites. Heat unit projections were provided by Bob Scott, Illinois State Water Survey.

Mike Gray, Extension Entomology, (217)333-6652