Grass Sawflies Clipping Heads in Wheat Too

There have been a number of reports of heads being clipped in wheat.  Some of it can be blamed on armyworm, but some cases (at least in Rodney) have been due to larvae known as grass sawflies.  These larvae are green to green-yellow in colour with a yellow brown head.  They look like caterpillars but are actually larvae from the order Hymenoptera or wasp group.  Unlike armyworm, they do not have stripes along their body but do have 8 pairs of chubby prolegs starting directly after their 3 pairs of true legs all the way to their last body segment.

Chris DiFonzo from Michigan State University is also starting to see heads being clipped there.  She put together a great infosheet this weekend on which critters could be blamed for the clipping and how to tell them apart.

Sawfly larvae feed during the day so they should be easier to spot, though they do blend in well with the colour of the crop.  They can actually do more damage, according to the literature, than armyworm if in high enough numbers.  Thresholds are hard to peg down since this is a rare occurence but Delaware has a threshold of 2 larvae per 5 feet of row.  If significant head clipping is noticed I feel that control is necessary.  Treat them as you would armyworm, but spraying can take place during the day since that is when they are feeding.

As for the armyworm populations, larvae are still reasonably small in size (most at 1/2 inch to some at 1 inch) and populations do not seem as high as usual.  But given that they are still small, they have a lot more feeding to do.  So scouting this week is VERY IMPORTANT. The armyworm larvae seem to be more green and orange in colour than the darker brown versions we are accustomed to seeing.  Again, use the infosheet provided above to help confirm your ID.

Keep the comments coming in so that we can get a good sense of what the head clipping situation is like out there.