Armyworm

FOR IMMEDIATE RELEASE
July 3, 2008

Armyworm damage to corn was recently observed. This pest can also infest wheat and pasture. The armyworm moth enters the state on the same prevailing winds and storm fronts that bring black cutworm moths.

Armyworm moths seek rank grass on which to lay eggs. Thus, wheat fields and corn planted into a grass cover crop or into grassy weeds are prime candidates for armyworm feeding. Corn planted no-till into rye is especially prone to armyworm infestation.

Young larvae are pale green in color, although longitudinal stripes are apparent, and the head is yellow-brown. Older larvae are green-brown and more prominently striped. A narrow, broken stripe along the center of the back and three stripes along each side of the body can usually be seen. The tan head is mottled with dark brown and each proleg (the false, peglike legs on the abdomen of a caterpillar) has a dark band.

You can track the development (by accumulation of degree-days) of armyworm at www.ipm.uiuc.edu/degreedays Click on "degree day calculator" in the upper right corner of the page to begin.

As mentioned above, armyworms can defoliate corn and pasture, and cut wheat heads. Suggested treatment thresholds and insecticides are listed in the 2008 Illinois Agricultural Pest Management Handbook at www.ipm.uiuc.edu/pubs/iapmh/01chapter.pdf Your local University of Illinois Extension office can also help you get a copy.

When monitoring corn, wheat, and pasture, check for their presence-don't let armyworms surprise you in 2008!