Researchers Deploy Parasitoid Wasps in Battle with Wheat Stem Sawfly

January 31, 2025

Researchers Deploy Parasitoid Wasps in Battle with Wheat Stem Sawfly

By Chabella Guzman - Panhandle Research, Extension and Education Center Communications Specialist

men talking in wheat field

UNL Graduate Student Vinicius Zuppa discusses research on the wheat stem sawfly at the High Plains Ag Lab 2024 Wheat Variety Tour. (Photo by Chabella Guzman | Nebraska Extension)

One UNL research team is exploring a unique tactic for combatting Nebraska’s wheat stem sawfly woes. 

A native to Nebraska, the wheat stem sawfly has become a big problem for wheat growers in the Panhandle. The High Plains Ag Lab (HPAL) has spent many years and extensive research on the sawfly, conducted by Team Sawfly and Vinicius Zuppa, a graduate student. 

“One of the bigger findings we’re seeing under sawfly infestation is smaller wheat heads,” said Amanda Easterly, Nebraska Extension dryland cropping specialist. “So, not only are we losing yield to lodging and the inability to harvest, we're also seeing that it's actually taking a toll on photosynthate going up to the grain.”

During extension’s Jan. 8 Crop Production Clinic at the UNL Panhandle Research Extension and Education Center in Scottsbluff, growers learned of an exciting new development in the battle against wheat stem sawfly. 

The bright spot in HPAL’s ongoing research is the increase in Bracon spp. — a parasitoid wasp and natural predator of the sawfly — which is beginning to make a dent in the infestation problem. In the Sidney area and southern Panhandle, the wasp has begun to show a measurable impact on protecting the grain yield. 

wheat stem sawfly and wasp specimens
Figure 1. Wheat stem sawfly adult (left) and the two species of Bracon parasitoids (middle and right) that are commonly found parasitizing wheat stem sawfly larvae in Nebraska. (Photo by Jeff Bradshaw | Nebraska Extension)

“The (wasp) is able to paralyze and incapacitate the sawfly larvae early enough to reduce damage,” Easterly said.  

Team Sawfly is investigating a new project that involves transporting the wasps in bales of straw to areas with sawfly infestations. The straw bales will come from HPAL, which Team Sawfly considers a parasitoid wasp nursery. 

“It's a big project that involves a lot of collaboration and expertise,” said Pin-Chu Lai, Nebraska Extension entomologist. “So, we're excited and we'll be doing a lot of monitoring and moving straw around this coming season.” 

The European corn borer was another insect pest discussed at the Crop Production Clinic. This pest has not been a problem since 1996, when BT crops — including corn — were introduced, and the borer’s populations decreased. However, the insect is back on the extension radar, as it has developed some resistance to BT crops in Canada and the northeastern U.S. 

“The European corn borer is a small, light-colored moth with small whitish larvae who have shiny black heads and some dark spots on them,” said Julie Peterson, Nebraska Extension entomologist. “There are two generations a year, so for the first generation, you're going to be looking around June in your vegetative stage corn.” 

The borer caterpillar has a distinct feeding pattern that looks like small hole punches in a line across the corn leaves. As the caterpillar eats, it tunnels into the corn plant. The second generation appears at tasseling or just past tasseling, burrows into the cornstalk or the ear, and feeds, damaging the stalk or ear and decreasing yield.

Peterson said that while BT resistance by the European corn borer has not been detected in Nebraska, growers should be aware of it and be on the lookout for the pest.

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