No. 9 Article 1/May 20, 2005

Arrival of More Spring Moths

Moth traps are becoming quite busy in southern Illinois these days. Ron Hines, Dixon Springs Agricultural Center, has reported the first captures of European corn borer and Southwestern corn borer moths of the spring. Traps in Massac and Pulaski counties picked up the first ECB moths on May 13 and in Pope County on May 16. On May 17, the Pulaski County trap also had a capture of two Southwestern corn borer moths. While it's too early to begin scouting for these insects, the presence of adults is worth noting. Usually, early-planted corn is most at risk for infestations of European corn borers. Even though some areas in Illinois had a slow start on corn planting this spring, planting progress is nearly caught up compared with last year. However, the recent corn growth and emergence have been slow. Corn under 18 inches tall is not very susceptible to European corn borer injury because it possesses a compound, DIMBOA, that prevents larvae from establishing. This slow corn growth may lead to an asynchrony with European corn borer hatch, which as a result may affect European corn borer survival if both early- and late-planted corn is still producing DIMBOA. Only time will tell.

European corn borer moths.

Southwestern corn borer moths caught in Pulaski county May 17 (photo courtesy of Ron Hines).

True armyworm moth flights continue, although at very low levels. But don't forget about this insect either. Armyworm moths prefer lush vegetation to deposit their eggs. Pastures, roadsides, along fencerows, and weedy or reduced tillage fields are all prime locations. As larvae hatch, they feed on host plants until they begin to run out of food. They then begin to move to other host plants, such as small grains and corn. Wayne Bailey, University of Missouri extension entomologist, reports that numbers of armyworm larvae are approaching five small larvae per square foot in some pastures in northern Missouri. Here in Illinois, we need to keep our eyes on our fields to avoid a surprise infestation. As Wayne remarks in a news release, "If you notice feeding when driving by in a pickup truck, it's too late." Scouting for armyworm early in the season will require getting down on your hands and knees, searching the ground and lower leaves of the plant.

True armyworm larvae (photo courtesy of Matt Montgomery).

On a final note, black cutworm moth flights remain low as well. This past week, two more intense flights occurred. Sam Markert, Adams County, captured 16 moths over the weekend, and Marc Rigg, Pioneer, reported the second intense flight of the spring in his trap on the Mason/Tazewell county line. The list of potential cutting dates compiled as a result of the captures in those locations is in Table 1. Even though significant moth flights have been few and far between this spring, continue to scout fields for potential black cutworm injury. Corn is susceptible to injury until it reaches about 15 inches, although taller plants are sometimes attacked. The slow growth of corn will provide a longer window for potential injury caused by black cutworm. Although larvae do not begin cutting plants until they reach fourth instars, they can feed on corn leaves, causing small irregular holes.



Black cutworm injury.

To read more about these insects, visit their respective fact sheets on the IPM Web site: European corn borer (Adobe PDF), true armyworm (Adobe PDF), and black cutworm (Adobe PDF). As always, if you notice any injury occurring in your fields, please share your findings with us.--Kelly Cook

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