Update on Black Cutworm Moth Captures

April 16, 1999
Reports of black cutworm moth captures continued in many counties of Illinois during the most recent week. On April 9, 11 moths were captured near Tuscola (Douglas County) by John Pflum. As has been discussed previously, moth captures at or beyond nine moths collected during a 1- to 2-day period should be viewed as intense. After 300 heat units (base temperature 50°F) have accumulated beyond this date, cutworm larvae may be at a size (fourth larval instars) to begin cutting plants. Prior to this stage of development, smaller cutworm larvae feed on leaves, creating small holes on the leaf surface. Cornfields most susceptible to cutting and economic losses are those with plants at or below the 4-leaf stage of development. So far, moth captures in other areas of the state have been relatively low. Jim Morrison, Crop Systems Educator, Rockford Extension Center, reported very light captures of moths during the evenings of April 8 and 9 in Stephenson and Winnebago counties. This confirms that black cutworm moths can be found throughout Illinois, even in the northern tier of counties. In southern areas of the state, moth captures also remain very light. Jeff Staley monitors seven traps throughout Gallatin County and through April 7 continued to report very low numbers of moths being captured. Len Dobbins, FMC Corporation, also has organized a network of cooperators who monitor black cutworm moth flights throughout the state. For the week of April 2 through April 8, captures were reported but were below intense levels for the following counties: Bureau, Christian, Coles, Grundy, Henry, LaSalle, Mercer, Piatt, Shelby, and Whiteside. However, on April 5, 18 moths were collected by a Montgomery County cooperator, WLS Flying.

As we learn of more intense captures this spring, we will cooperate with Bob Scott, Illinois State Water Survey, to generate tables that offer projections for when cutting is most likely to begin for the different regions of Illinois. These projections will be based on meteorological data collected through the Illinois Climate Network, which includes the following sites: Belleville, Bondville, Brownstown, Carbondale, Champaign, DeKalb, Dixon Springs, Fairfield, Freeport, Kilbourne, Monmouth, Olney, Peoria, Perry, Rend Lake, St. Charles, Springfield, Stelle, and Wildlife Park. Stay tuned for these projections in upcoming issues of the Bulletin.--Mike Gray

Author: Mike Gray