Armyworm and grass sawfly showing up in wheat
The window for spraying armyworms and grass sawflies in wheat fields may be closed.
We’ve still been getting a few calls about wheat. When head clipping is involved, many growers report armyworms plus grass sawflies are present. As the wheat crop matures, spray decisions are more difficult. If armyworms are large (1.5 inch), they will be pupating in a few days and the problem is over. If there are still smaller worms, two or more per square foot, fresh head clipping is occurring, and the field still has four weeks until harvest, a spray may be justified (I stress may).
However, spraying is balanced by having to run over wheat, or spray aerially where coverage can be an issue. Product choice is limited – Pre-harvest Intervals (PHIs) are 14 days for Mustang and seven days for Lannate. Lannate is the preferred choice if grass sawflies are common. In general, my feeling is the spray window has closed.
Dr. DiFonzo's work is funded in part by MSU's AgBioResearch.