Close-up of a leaf of corn damaged by southern corn rust. Tamra Jackson-Ziems
SCR MORE COMMON: An ongoing challenge in eastern Nebraska is the increasing prevalence of southern corn rust in Nebraska cornfields. In parts of southeast Nebraska, the disease has been present since mid-June.

Despite challenges, August conditions could make a difference for corn, soybeans

Whether disease, drought, weeds or herbicide injury, a number of issues plagued Nebraska corn and soybean growers this year. Still, conditions over the next month could make a big difference.

As the crop season heads down the home stretch, crop conditions are varied throughout the state,  depending on location, disease pressure and the amount of rain that's fallen.

Parts of northeast Nebraska are in moderate to severe drought, while many parts of the west-central region are abnormally dry or in moderate drought as of early August, according to the University of Nebraska Drought Monitor.

Here's a look at how corn and soybeans are shaping up across Nebraska:

• East-central. Many parts of east-central Nebraska received several inches of rain in July, with the exception of a few pockets, notes Nathan Mueller, Nebraska Extension cropping systems educator in Dodge and Washington counties. "In about 80% of Dodge and Washington County we actually have some pockets that will probably yield better than last year if we continue to have good conditions in August," Mueller says.

While some corn planted in mid-May is around R2 or blister, earlier May and April-planted corn is reaching the milk stage or R3. However, Mueller notes some late-planted corn on the Missouri River bottom near Blair hadn't tasseled until just recently. The bulk of soybeans are at the beginning to full pod stage around R3 to R4, while earlier-planted soybeans are nearing beginning seed at R5.

A few cornfields are showing signs of pollination and ear development issues after several days of excessive heat in July.

"Most of pollination occurs over a five-day period. If you throw in some drought and heat stress over three of those five days, you can have some issues with kernels not pollinating and ear deformity," Mueller says. "We had some actual ear development issues with certain hybrids. There might be some of those same issues again like we had last year, but I don't think it's severe."

Southern rust, while not a common problem in east-central Nebraska, is spreading further into the region. It was recently confirmed near Scribner.

"We can control southern rust with a fungicide, but for those that already sprayed corn in mid-July, you're only getting residual protection for three weeks," Mueller says. "Into the first week of August, southern rust could move in, and if it gets bad, you may be in a situation where you have to decide whether to spend more on another fungicide application."

Some soybean fields are showing signs of frogeye leaf. Most occurrences are in fields where frogeye leaf spot has been identified before.

One of the widespread issues consistent across Nebraska has been dicamba injury on non-dicamba-tolerant soybeans. Most of the dicamba issues appear to be related to volatility rather than drift, notes Mueller.

Amit Jhala

SYMPTOMS OF INJURY: This year, soybean growers in parts of Nebraska saw the telltale signs of dicamba injury in soybeans. In most cases, the injury was likely due to volatilization, since the signs of injury have largely been consistent across entire fields. 

• Southeast. Dry conditions persist in portions of southeast Nebraska, where certain pockets haven't received significant rain since late May, says Jenny Rees, Extension educator serving York, Seward, Clay, Nuckolls, Fillmore and Thayer counties. "Non-irrigated corn, even beans for that matter look fairly tough right now where we’re seeing the effects of drought," Rees says. In this part of the state, corn ranges from late blister all the way to late dough stage. Soybean progress ranges from beginning pod at R3 to seed filling at R5.

Cornfields in southeast Nebraska counties are also taking a hit from diseases like southern rust and gray leaf spot.

"We've been seeing southern rust since July 17. We haven't seen an explosion of southern rust yet, but my guess is we're probably going to see more of it in the next several weeks," says Rees. "With the cooler temps and humidity, gray leaf spot is also progressing on lower canopy leaves up to mid-canopy. We've also been seeing bacterial leaf streak since June and it appears to be fairly hybrid-dependent. However, I think our growers are becoming more aware of it, and I wouldn't say there's as much concern this year as last year."

Like other areas of Nebraska, dicamba injury has also been a major issue this year. In this part of the state, much of it early on was due to volatility from applications to cornfields, notes Rees.

"Early on in June we had a 10-day window where a lot of corn applications were made. We had high heat, high humidity, and there were days where we had proper wind conditions for spraying but it got completely still at night," says Rees. "I've never before seen field-scale volatility issues from corn applications, but the weather conditions, increased use of dicamba products in both corn and soybeans for Palmer amaranth control in particular, and many spraying in a short time frame led to a perfect storm this year. Dicamba can be volatile at least 24 hours after an application."

• South-central. Early on in the season, through most of May and June, many parts of south-central Nebraska were dry. However, Todd Whitney, Extension educator in Furnas, Gosper, Harlan and Phelps counties, note some pockets in the region timely rains in July.

"It's been one of those years where it's varied a lot. We had a pocket of 3.5 inches of rain in Holdrege about 10 days ago, but a few miles west, an inch and a half, and then 40/100 as you get farther west," says Whitney. "Overall, we have received enough rainfall the last couple of weeks where people may have turned their pivots off for a week or more as varied rains continue."

Most of the corn crop in the region has been tasseled for about three weeks, with moisture demand trending

lower as fields near the blister development stage. Soybeans are mostly in the R3 to R4 stage; they aren't quite to pod, but are getting close. Field scouting for southern rust and grey leaf spot continues; however, this year corn’s biggest concern has been record numbers of western bean cutworms.

A top soybean issue has been dicamba injury — evident by the telltale signs of cupping on soybean leaves likely due to volatility. One of the key indicators of dicamba volatility is injury across entire fields.

Judging by cupped leaves on nodes 3 and 4 up from ground level, Whitney says most of the injury in his part of the state likely occurred in early June. That being said, it's more likely the injury stemmed from volatilization from nearby dicamba-tolerant soybean fields, adds Whitney. According to the label, dicamba should only be applied on corn when the plant is less than a foot tall. By early June, unless planted late, corn should be well beyond this height.

"It was almost like people that didn't plant dicamba-resistance soybeans may have been victim from either soybean or cornfields sprayed with dicamba nearby, as it moved off of their fields to those that weren't resistant," says Whitney. "We think people did the right thing, preventing resistance from building up using new modes of  herbicide action, such as Ignite with LibertyLink soybeans. But when they did that, they were susceptible to drift or volatilization from those that used dicamba."

• West-central. Rodrigo Werle, Extension cropping systems specialist at the West Central Research and Extension Center at North Platte, notes it's been a rough year for dryland corn in the area.

"Soybeans are finally canopying now. It was a rough start with a cold spell early on," says Werle. "I think we're a little bit behind last year, but well-managed irrigated corn is progressing well. We were real dry for three to four weeks, so the rain-fed corn isn't in the best shape. However, since last Friday [July 28] we had 2 to 5 inches of rain depending on the region. Unfortunately, it's coming a little late, but it's better than not having anything."

Many cornfields in this part of the state are slightly behind schedule. Some fields tasseled later — about two weeks ago. Corn progress ranges from silking at R1 to early milk stage at R3. Most soybean fields are around the R2 to R3, or beginning pod stage.

In early August, much of the west-central part of the state was considered abnormally dry and in moderate drought. Moving forward, Werle notes there may be some relief in the hot, dry weather.

"One top of dry conditions, we had a week with triple digits almost every day and that doesn't help during the tasseling period. Looking at the forecast the next week, it looks like temperatures aren't going to be as hot," he says. "At this point, all you can do is see how things progress. We've been talking to some growers who believe they may harvest a little later this year, just because of how the crop is progressing. I don't know whether that will hold true or not, but with cooler days as we progress, they slow the crop development. The cooler days we have, the slower the crop is going to finish and the later harvest comes."

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