No. 11 Article 1/June 4, 2004

Sporadic Armyworm Infestations Reported in Wheat

Producers should remain vigilant with regard to their scouting efforts for armyworm infestations in wheat. Late last week, Matt Montgomery, a crop systems educator for the Sangamon and Menard Extension unit, reported finding armyworms in northern Menard County at levels that ranged from two to eight larvae per foot of row. As mentioned in the Bulletin last week (issue no. 10, May 28, 2004), producers should consider a rescue treatment when armyworms reach densities of six or more nonparasitized armyworms (3/4 to 1-1/4 inches long) per linear foot of row. In addition, wheat growers need to pay particular attention to the threat of head cutting. To find these larvae, Matt indicated that he scouted the field in the early evening and found the larvae beneath decaying plant residue. He also found considerable defoliation on some plants. Please refer to the Bulletin from last week for more detailed information on armyworm management and suggested insecticides.

Armyworm larva with parasitoid egg attached to thorax.

Dead armyworm larva that has succumbed to a viral disease.

Dead armyworm larvae (caused by a viral disease) on wheat heads.

Before making any final treatment decision, keep in mind that armyworms are very susceptible to a number of natural enemies that include parasitoids and diseases. I have observed large armyworm populations collapse within just a few days. Care should be taken during scouting efforts not only to estimate armyworm numbers but also to look for evidence of diseased or dying armyworm larvae. Matt indicated that he will continue his scouting efforts through Sangamon County and report his findings to us. When we receive his updates, we'll pass them along to you.--Mike Gray

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