Tag Archives: Nebraska

LINCOLN — Wheat stem sawfly (WSS) has been a very significant pest of wheat in the northern wheat-producing regions of our country such as Montana and North Dakota and well into Canada. Larvae cut and weaken the stems of maturing wheat causing the wheat to lodge creating very significant harvest losses in many situations. WSS damage in winter wheat was first noted in Nebraska in the early to mid-1990s. The first infestations were noted in Banner County near the Wyoming border. It has continued to increase ever since and now is a very significant issue. Integrated pest management will be needed to attack the problem with multiple tactics. Crop rotation, resistant varieties with solid stem characteristics, tillage, field width, and trap crops are some of the tools that can be used to combat this problem.

Following the moderately heavy infestation of WSS in winter wheat in the 2019 growing season, we had concern for ongoing infestations in 2020. During May and early June 2020, adult sawflies were observed in fields, but we were unsure of the level of infestation. Those emerging numbers of sawflies developed into another year of significant sawfly infestation and cutting as we are seeing during the 2020 winter wheat harvest. Infestations this season are moderate in the northern Panhandle and heavier in the southern Panhandle. Note the lodged tillers remaining after harvest in a Deuel County field (Figure 1). Dryland wheat yields are looking good averaging from 40 to 50 bu/ac despite sawfly activity in the northern Panhandle. Some yields in the southern Panhandle are as low as 25-30 bu/ac due to the sawfly. The wheat harvest this year is ahead of last year due to warmer, drier weather.

Figure 1. Unharvested tillers remaining in field due to Wheat Stem Sawfly lodging.

Dryland wheat is most seriously affected but some level of infestation also occurs in irrigated wheat. Dryland wheat adjacent to undisturbed stubble from last year appears to have the worst infestations. In some fields, 50 to 70 percent of the stems are cut for the first 50 to 100 feet of the field edge (Figure 2). Cutting tapers off further into the field but may be as high as 15% across an entire field.

Sawfly larvae overwinter in the stubble (Figure 3) of the previous year’s crop and emerge in May and June to attack the developing crop during stem elongation. Females (Figure 4) emerge from the stubble, mate, and lay an egg in the newly elongating wheat stem. The egg hatches and the larvae feed and tunnel through the nodes of the developing wheat finally to girdle and weaken the stem causing lodging for its exit from the remaining stub the following spring. The larvae live in a pupal chamber inside the stub at the very base of the stem (Figure 5 & 6) after harvest and through the winter.

Wheat Stubs
Figure 3. Wheat Stubs remaining in field.
Adult female
Figure 4. Adult female WSS.
pupal chamber and larvae
Figure 5. Cellophane like pupal chamber and larvae.
Wheat Stem Sawfly larvae
Figure 6. Wheat Stem Sawfly larvae.

After extreme highs and lows in Nebraska throughout the wheat growing season, harvest has finally begun. Producers along the southern border and in the southwest corner of the state have cleaned and tuned up their combines and are hitting the fields this week. As the month progresses we will see harvest continue to move into the northern panhandle to wrap up Nebraska’s wheat growing season.

Mother Nature was not kind to wheat farmers this year. Hard late freezes, minimal moisture and one of the hottest June’s in history took its toll on the state’s crop. “The April freezes claimed some fields and also left the crop standing shorter than normal” said Royce Schaneman, Executive Director of the Nebraska Wheat Board. “Producers were continually weary throughout the season due to the lack of rain paired with hot, windy days. The soil moisture seemed to be continually depleted.”

For most of the state, harvest is beginning earlier than normal with the exception of the southeast corner being a week late. Mark Knobel, a wheat farmer from Fairbury, NE said “I expect yields to be average this year. Protein content should be good due to the lower yields, though we may find ourselves in trouble if we get low test weights.”

Along with Hard Red Winter wheat, Nebraska will also be harvesting around 10,000 acres of Hard Red Spring wheat this year. The Hard Red Spring variety began appearing in the state a few years ago as farmers looked for alternative wheat markets and value added products. Acres planted has been on a gradual increase, though this year’s crop may not fair the best. “My spring wheat is standing 10” tall,” explained Brent Robertson, a wheat farmer near Elsie, NE. “It is beginning to turn, though I don’t expect to see a good return on it this year.”

As the Nebraska wheat harvest goes into full effect this upcoming week, producers will gain a better understanding of where their crop stands this year. There are many predictions of an average crop and the United States Department of Agriculture is predicting a 44.4 million bushel harvest.

To stay up to date on the Nebraska wheat harvest, follow the Nebraska Wheat Board on Twitter at @NebraskaWheat or on Facebook at www.facebook.com/nebraskawheatboard.

The Nebraska Wheat Board administers the check-off of 0.4% of net value of wheat marketed in Nebraska at the point of first sale.  The board invests the funds in programs of international and domestic market development and improvement, policy development, research, promotion, and education.