Stress, disease, viral impacts expected in US wheat

However, not all areas shared equally in the long-awaited precipitation. That disparity means drought stress will be more evident in select areas. Plus, other crop issues such as freeze damage, disease and viruses are likely to be evident, resulting in a highly variable crop.

More information will disseminate from the top hard red winter wheat production state of Kansas May 14-16 when scouts from across the wheat value chain, academia, government and media will traverse the Sunflower State on the Wheat Quality Council’s annual winter wheat tour. 

Several weeks of intermittent rains from late April to early May hewed largely to the easternmost areas of Kansas. More consistent and widespread rain soaked Nebraska and Oklahoma, greening pastures and perking up winter wheat fields. Some areas received too much rain too quickly and standing water was reported in fields along Kansas’s eastern border and into northeast Oklahoma by a trader on an earlier crop tour heading south. Areas to the east of Wichita, Kansas, US, looked to be in good shape but “from Dodge City to Garden City looked pretty rough,” he said. 

“The drought areas are probably going to be the dominant story for the wheat tour, but there’s just going to be so much variability across the state on the routes for day one, day two, and day three,” said Justin Gilpin, chief executive officer of Kansas Wheat. “We’re going to see some wheat that’s benefited from the moisture along certain parts of the state, like the northern part of the state. And some pockets up in the northwest part of the state, but the real challenged areas are going to be some of those west-central over to the central part of the state who have not have just unfortunately missed out on these recent rain events.”

Though he expects the crop to show drought stress in places, the scenario differs from the dry crops of the past two years, which were severe enough to prevent plants from emerging, Gilpin said. 

“Abandoned won’t be as high as we saw last year,” he said. “I think we’ll be a little bit surprised on how the wheat’s responded to some of the recent rain that’s been beneficial for those who’ve been able to get it. But there are still wide areas such as the west-central area from north of Garden City over to Great Bend where wheat was probably past the point of being able to take advantage of the moisture just because it was a little too far gone. We’re in the third year of impactful drought scenarios for these producers. The crop got off to a pretty good start last fall, got some snow cover over the winter, but didn’t get the follow-through rain at an important time when the crop broke dormancy.”

Beyond the drought effects, scouts will be on the lookout for three other factors Kansas State University agronomists have said are present to some degree in the crop.

Disease

Foliar diseases called leaf rust and stripe rust impact the overall health of the wheat plant. Stripe rust has been noted in wheat plants in 35 Kansas counties this year, K-State Research and Extension said this week. When rust shows up on the flag leaf of a wheat plant, it is an indication the overall health of the plant is compromised. Instead of a tall, healthy, green plant using photosynthesis to maximize filling the head, the rust deteriorates the main flag leaf, which can’t absorb the sunlight and nutrients to fill the head to maximize filling the head to its full potential.

“When you have a Texas wheat crop that starts to get some incidence of stripe rust or leaf rust, these big southern winds we’ve seen this year blows through the crop up north,” Gilpin said. “And that’s worked its way through Oklahoma, now it’s into Kansas and it hits the plant like a fungus.”

Virus

Chatter among agronomists has indicated wheat streak mosaic virus is present in some of the southwestern areas of production. Wheat streak mosaic limits yield potential and gives plants a yellow, sickly appearance and blocks the development of a wheat head. It’s carried by wheat curl mites sometimes present on volunteer wheat growing before the field’s actually seeded. That can impact wheat through the development phases and then become a vector exacerbated by dry conditions and southern winds infecting a broader area.

“We’re seeing it in areas where growers thought it was just solely drought pressure,” Gilpin said. “But now that they’re getting some rain on those plants and they’re not recovering, it’s pretty clear that they that there are incidents of wheat streak mosaic virus and so we’ll see some of that most likely on tour day two when we go through that west-central and southwest part of the state. It’s really detrimental to yield potential and what’s so frustrating about it is producers can’t treat a crop with a fungicide to try to protect it. They’ve got to hope for genetic resistance and then hope management to controlling volunteer wheat helps keep it from impacting or infecting fields.”

Freeze damage

K-State agronomists expect crop scouts will see evidence of freeze damage in the form of emerging white heads that don’t have any kernels. Ideas are that a late-March freeze event hit the crop at a crucial development point.  

“We’ll see that kind of in the central part of the state,” Gilpin said. “If the plant suffered a freeze event while it was developing the head in the boot stage, because the growth point was high enough that it got impacted by that freeze event, what emerges looks like a head, but it just doesn’t have any kernels in it because it was kind of killed by the freeze event. You don’t really know the impacts of a freeze event until you get out in the field and see that whether or not the head actually fills kernels or not.”

The USDA’s latest winter wheat conditions update, which rated the crop as of May 5, showed where recent rainfall was most beneficial. The Department said winter wheat rated good-to-excellent was 32% in Kansas (31% a week earlier), 52% in Oklahoma (46% a week earlier), 48% in Texas (48%), 45% in Colorado (46%), 67% in Nebraska (63%), 69% in South Dakota (67%) and 37% in Montana (43%). 

On May 6, severe storms moved across the southern Plains. Gusty winds whipped through Goodland, Kansas, US. Tornado watches were issued for most of Kansas and some central areas of the state received damaging winds and hail. A rain-wrapped tornado moved through northeast Oklahoma, bringing 60 mph wind gusts and hail up to ½-inch in diameter. Tornadoes severely damaged the Oklahoma towns of Barnsdall and Bartlesville on May 6. Kansas had significant storms over a 24-hour period where parts of southeast Kansas received eight inches of rain, and parts of central and western Kansas received no rain.

“It was the definition of excesses of the haves and have-nots,” Gilpin said. “That accumulation heavy rainfall in the eastern part of the state has caused some sogging and some flooding that will impact some of that wheat. Eastern Kansas had a nice crop last year. I don’t think that region will have the record-high high yields we saw last year, but I think as you move east in the United States from Eastern Kansas into Missouri into the soft red winter wheat states, that crop is actually looking in pretty good shape.”

The USDA said winter wheat in drought on May 7 totaled 75% in Kansas (76% a week earlier), 7% in Texas (8%), 39% in Colorado (17%), 3% in Nebraska (6%), 13% in Montana (15%) and none in South Dakota.