Crop advisor casebook: Can you identify the worms in this barley?

A Crop Advisor's Solution from the January 7, 2020 issue of Grainews

I could see lots of the worms crawling around next to an armyworm that I also observed on the plant.
Raeanne Denomie. photo: Supplied

Like most farmers, Tom has dealt with his share of insect pests. He’s encountered many different pests at his 6,000-acre mixed grain operation near Wadena, Sask., over the years, but this past August he came across a new insect that had him stumped.

Tom called me in early August to say he’d been out inspecting one of his barley fields at head emergence when he’d spotted some unusual little worms crawling around in the awns of some plants. He had no idea what they were, and because he’d already seen cutworms and flea beetles in his crop earlier in the season, he was worried this unfamiliar insect could cause further problems.

Tom asked if I could come out right away to help identify the worms. I arrived at his farm and started scouting the barley field, but I couldn’t see any sign of the insect.

Tom, like most producers in the area, had had a challenging year dealing with emergence and insect issues throughout the season, so I was aware that he’d been monitoring his crops very carefully to ensure nothing else went wrong. I knew there had to be something there or else Tom wouldn’t have called me, so I kept looking.

Finally, I encountered a barley plant with the insect Tom had described. I could see lots of the worms crawling around next to an armyworm that I also observed on the plant. Looking around, I spotted more worms and some cocoons on other barley plants and even on some wild oats that were also in the field.

These unusual little worms were crawling around in the awns of some plants. photo: Supplied

I wasn’t sure what I was looking at either, but when I consulted my textbook on field pests to identify the insect, it became clear what this insect was and just what kind of threat it posed to Tom’s barley crop. When I informed Tom, the answer to those questions took him by surprise.

Crop Advisor’s Solution: Not all insects are pests

After consulting my textbook on field pests, I knew what I was looking at wasn’t a pest at all!

The worms and cocoons belonged to a beneficial insect called the Braconid wasp, which parasitizes caterpillar pests such as armyworms. Braconid wasps lay their eggs in the caterpillars, which then hatch and produce larvae that consume the caterpillars from the inside out.

The little worms I found with the armyworm were, in fact, Braconid wasp larvae, which had likely just emerged from the armyworm. Within hours of emerging from their insect hosts, the larvae will cocoon and continue their life cycle.

When I gave Tom the news, he was relieved to hear he didn’t have another problem insect on his hands. I told him nature has a way of taking care of pests, and I advised Tom to leave the Braconid wasps to do their job in his barley crop.

Reanne Denomie, PAg, CCA, BSc, works for Richardson Pioneer in Wadena, Sask.

About the author



Stories from our other publications