Armyworms Showing up in a Few Mississippi Wheat Fields

In the last 7 days there have been a few calls coming in about armyworms in wheat.  Numbers have ranged from 1–12 per square foot.  Mississippi has always used a threshold of 5-6 larvae per square foot through the milk stage.  Once past the milk stage armyworms should be treated if they begin to clip heads.  Most calls to date have been smaller larvae down in the canopy feeding on lower leaves; however, I have had one report of a few heads being clipped on a field border.  Data from Arkansas in the early 2000’s suggested that once wheat reached the milk stage that very little yield loss was associated with foliage feeding. This was true even when they defoliated all plant foliage including the flag leaf.  Nearly everyone I have been talking to lately says their wheat is at least in the soft dough stage if not slightly beyond.  If this is the case I would only recommend treating armyworms if head clipping begins.  We do not have a sweep net threshold on armyworms.  Armyworms are generally sampled by folding back the canopy and shaking plants on the ground.  Armyworm infestations will likely be highest where bluegrass is mixed in the wheat.  True armyworms are not difficult to control as long as you can get the material down to them.

Armyworm larvae on wheat heads, 2001 (photo courtesy of Robert Bellm, University of Illinois Extension).