Left flat: Growers plan to manage around sawfly | TSLN.com

Left flat: Growers plan to manage around sawfly

Rachel Gabel
for The Fence Post
Sawfly larvae damage is difficult to control. Pesticide application seems to be ineffective in controlling larvae which are the ones doing the damage. This larvae was found in a wheat stem near Prospect Valley.
Photo by Marc Arnusch

Marc Arnusch’s phone has been ringing with calls from wheat growers preparing to plant after a year wrought with sawfly damage. Sawfly damage, which leaves stalks laying flat at or near harvest, is becoming more prevalent, he said. Arnusch said the pest has been moving south from the northern states and he had damage on his farm this year near Prospect Valley, Colo.

“I suppose if you’re south of I-70 or down in the southeastern part of the state, it might not be affecting you today, but for our producers in northern Colorado and certainly on the eastern plains, it’s becoming a bigger and bigger deal all the time,” he said.

He said he was surprised to see the damage in his fields this year as the area rotates crops consistently, leaving little wheat fallow, and his fields are not in close proximity to large expanses of dryland wheat. He said he noted damage even on fields that hadn’t been planted to wheat in five years or more. One test plot was even damaged so severely that he said it was mowed off at the ground, leaving it looking like hail damage.

“We know our pressures are certainly there,” he said. “In my experience, it’s prevalent when you have fields of wheat near grassy areas, maybe a grass sprinkler corner or maybe some pasture. It’s very prevalent when you have a standing wheat crop next to last year’s stubble crop with no separation and it seems more prevalent on the dryland than the irrigated but it doesn’t mean that you won’t be affected on the irrigated.”

Arnusch said producers may not know the extent of the damage until harvest when the stem falls right in front of the combine, making harvest difficult and leaving yields literally flat. Evidence of sawfly feeding is more evident once moisture levels fall below about 12 percent but the pest is difficult to target and control.


Arnusch carries and grows a number of varieties of wheat and said while they may not be bred specifically for resistance to sawfly damage, they have demonstrated tolerance to withstand sawfly with solid or semisolid stems.

“We feel if we err on the side of stalk quality or straw strength, and have a little stronger stem for the larvae to saw through, that’ll give us one tool in the toolbox for managing this pest,” he said. “I think we’re going to have to take a very multipronged approach to managing our infestation and we have to plant for it, selecting varieties that will withstand moderate to heavy pressures.”

On his farm, Arnusch said they will elect to plant earlier varieties that they can get out of the field earlier, perhaps harvesting at a higher moisture percentage of 13 or 14 percent in an attempt to harvest earlier.

“We’re also going to do a little bit more tillage and try to disturb some of the feed bed we have in the rotation on our dryland acres though that goes against conventional wisdom,” he said. “It may be surgical tillage where we go around the outside of the field or we have a little more special separation between this year’s wheat crop and last year’s stubble crop. We’ll work with industry leaders to see if there’s something we can do with seed-applied technologies to mitigate some of the pressures.”

This added pest pressure is especially frustrating for growers experiencing an already depressed marketplace.

“It’s hard to throw a lot of investment at managing the sawfly when wheat is $4.50 a bushel,” he said. “I think we have to use or heads in managing the pest and do it somewhat on a low budget right now, and that’s probably going to handcuff us more than anything. This seems to be our battle cry moving forward to take on the world with an empty checkbook.”

Arnusch is hoping there will be a concentration on establishing countries with emerging demand as trading partners. With less emphasis invested in the Chinese market, he identified Africa, India as natural trading partners.

“We do a really good job in this country of growing a lot of crops,” he said. “We have abundance in just about everything we grow here in Colorado.

He has heard from a number of seed customers hesitant to plant wheat this year given the plethora of challenges. Crop alternatives like millet and milo can break up the rotation cycle, he said. There’s no product on the market currently, he said, labeled to withstand sawfly but he said the time has come to work with industry partners to discover a good strategy. Montana seems to be experiencing heavy sawfly pressure but Arnusch said the pest is relatively new to Colorado in just the past five to 10 years. However, he said he has heard veteran growers who dealt with sawfly 30 to 40 years ago but said the past two or three years is the first time in his own farming career he’s faced the challenge.

“It’s like having a hailstorm without a cloud in the sky,” he said. “When you walk out there, it looks like you just got smoked in a hailstorm and when you open it up, you can see that they sawed right around the stem.”​ F