This year was a tough one for weed control in Nebraska. A drive east to west on I-80 in July and August painted a clear picture of several soybean fields full of resistant waterhemp and marestail.

For Clint Einspahr's region in southwest and west-central Nebraska, it started with the cool, dry weather in March and early April. "We were applying early in dry weather, and never got rain to get chemicals worked into the soil," says Einspahr, sales lead at Crop Production Services in Arapahoe and member of the 2011 class of the Syngenta Resistance Fighter Leadership Program. "When we did finally get a rain in mid-April, we got about 6-7 inches."

PROBLEM WEED: While resistant waterhemp has been a problem in Einspahr's region for several years, the cool, wet weather this spring made it an even bigger challenge to control this year. "I think we cleaned up most of the Palmer amaranth this year, but waterhemp became a more difficult issue," he says.

Some places in the region saw half of their annual average rainfall from mid-April through May, keeping growers and applicators out of the field for nearly a month, Einspahr notes. "The rain started in mid-April; we were out of the field until mid-May — almost a month," he says.

2-pass system pays off
That made it a challenge to control key resistant weeds in the area. While resistant waterhemp has been a problem in Einspahr's region for several years, the cool, wet weather this spring made it an even bigger challenge to control this year. In addition, a new challenge has been making its way into fields in western Nebraska recently: resistant Palmer amaranth.

About 400,000 acres in western Nebraska are infested with herbicide-resistant Palmer amaranth. However, resistant kochia remains the biggest weed challenge for western Nebraska producers, infesting around 1.2 million acres in the region, followed by resistant marestail at around 600,000 acres.

"I think we cleaned up most of the Palmer amaranth this year, but waterhemp became a more difficult issue. It grew too fast," Einspahr explains "It wasn't that growers and applicators weren't trying to get out there; it was wet. The two-pass system worked very well where we could get it done. Those that had flexibility of applying a pre and early post could delay some weeds and get them really early in their life cycle."

This two-pass system of applying a preemerge followed by overlapping residuals and a postemerge application later on paid off when applied at the right time, but some growers and applicators struggled with applying the post at the right rates for the height of the weed species. "If you get into the field and weeds are a certain height, we need to up our rates more than we have before," Einspahr says. "I think we have to do a better job of understanding how tall our weeds are; 8 inches is not knee-high. This year, we were spraying a lot of knee-high weeds with the same amount we'd spray an 8-inch weed with."

Concerns moving forward
With the challenges faced this year, Einspahr encourages producers in the region not to judge their weed control program based on its 2016 performance. "Sticking with what you know is going to work is going to be a big deal going into 2017," he says. "Don't change up chemical programs because it just didn't work this year as well as it has in the past; there were a lot of circumstances that led to it not work this year."

However, it's also important to not rely on the same mode of action over and over again and make the same mistakes that have resulted in ALS and glyphosate-resistant weeds. In a period of tight margins, one concern of Einspahr's is growers may be less apt to adopt a two-pass system, but Einspahr says it will be critical when using new technologies like dicamba and 2,4-D-tolerant corn and soybeans.

"We won't have those technologies very long unless we work harder to make sure they stay effective in our system," Einspahr says. "It's a hard sell to talk to growers and get them to commit, but we had so many soybean fields and even cornfields that had weed pressure that didn't before that I think growers know they can't cut back without hurting themselves on their yield, because they need all the yield they can get."

Options for chem-fallow acres

An ongoing challenge in western Nebraska is glyphosate-resistant kochia creeping into chem-fallow acres. However, because kochia is a late-maturing weed, growers in Clint Einspahr's part of the state have been adapting by planting cover crops on fallow acres. "It's slowly increasing," says Einspahr. "We try to get something out there early enough that grows above the kochia and crowds it out. It seems that what kochia does come up struggles, and we can kill it easier when we have to apply."

On the other hand, resistant kochia has caused some wheat-fallow producers to revert back to tillage, giving up benefits of keeping residue on the soil, Einspahr says. "Growers are definitely looking at options to change what they do, which is a good thing," he says. "We need to be more flexible and understand other ways to manage weed pressure, but I don't like seeing people go away from no-till."