Tag Archives: K-State

In some years, wheat streak mosaic virus (WSMV) can be a severe problem for Kansas wheat producers. Fields with very severe wheat streak mosaic can typically be traced back to a lack of control of volunteer wheat. Problems with wheat production the previous year can leave large amounts of seed on the soil surface. As this seed germinates, it creates a “green bridge”, allowing wheat streak mosaic and wheat curl mites to survive locally.

Challenges faced in 2020

This year, the wheat crop faced several challenges that might have increased the amount of seed left behind after harvest, which could also increase the amount of volunteer wheat (Figure 1). These problems included:

  • Freeze damage during stem elongation (which caused many delayed wheat heads to emerge)
  • Hailed out wheat
  • Some reports of head scab (Fusarium head blight)
  • Waterlogging conditions in parts of central Kansas
  • Drought-stressed wheat

The presence of later-emerged heads due to the freeze damage to main stems can cause differences in maturity between tillers that survived the freeze and later tillers, which can increase harvest losses. One of the recommendations to manage fields affected by head scab is to increase the fan speed of the combine and “blow” the diseased kernels out of the harvested grain.  Likewise, waterlogged conditions and drought stress both decrease wheat kernel weight and likely increase harvest losses of grain. These smaller kernels might germinate into volunteer wheat increasing the risk of severe wheat streak mosaic the following year.

Figure 1. Thick stand of volunteer wheat after wheat harvest. Photo by Stu Duncan, K-State Research and Extension.

 

Wheat curl mites will move off growing wheat as the green tissue dries down and dies. After moving off the existing wheat at or near harvest time, the mites need to find green tissue of a suitable host soon or they will die of desiccation.

Producers often like to wait several weeks after harvest before making their first herbicide application to control volunteer wheat. This allows as much volunteer as possible to emerge before spraying it or tilling it the first time. Often, a second application or tillage operation will be needed later in the summer to eliminate the green bridge to fall-planted wheat by making sure all volunteer is dead within ½ mile of wheat being planted in the fall. Wet weather through late summer often favors multiple flushes of volunteer wheat and also favors the growth of other grassy weeds that can also support moderate populations of the curl mites and virus. These weather patterns keep a lot more alternate host plants alive during the critical period when mites and virus would not have plants to survive on.

If volunteer has emerged and is still alive shortly after harvest in hailed-out wheat, wheat curl mites could easily build up rapidly and spread to other volunteer wheat that emerges later in the season. On the other hand, if this early-emerging volunteer is controlled shortly after harvest, that will help greatly in breaking the green bridge. However, if more volunteer emerges during the summer, follow-up control will still be needed.

Other hosts for the wheat curl mite

Volunteer wheat is not the only host of the wheat curl mite. Over the years, multiple research studies have evaluated the suitability of wild grasses as hosts for both the curl mite and the wheat streak virus. There is considerable range in the ability of a grassy weed species to host the mite and the virus. Barnyardgrass is among the more suitable hosts for both virus and mites, but fortunately it is not that common in wheat fields. In contrast, various foxtails, although a rather poor host, could be an important disease reservoir simply because of their abundance. These grasses may play an important role in allowing the mites and virus to survive during the summer months particularly in the absence of volunteer wheat.

The K-State Research and Extension publication, MF3383 – Wheat Streak Mosaic, includes information about grassy weed hosts of the mite and virus, and the contribution of these hosts to the risk of severe wheat streak mosaic infections. Take note of significant stands of these grasses in marginal areas and control them as you would volunteer wheat.

If volunteer wheat and other hosts are not controlled throughout the summer and are infested with wheat curl mites, the mites will survive until fall and could infest newly planted wheat. Wheat curl mite infestations of wheat often lead to wheat streak mosaic infections (Figures 2 and 3).

Figure 2. Volunteer wheat on the edges of a sunflower field were infested with wheat curl mites and caused a wheat streak mosaic infection in the adjacent wheat crop that fall. Photo by Stu Duncan, K-State Research and Extension.

Figure 3. Close-up of wheat showing symptoms of a wheat streak mosaic virus infection in the fall. Photo by Jeanne Falk Jones, K-State Research and Extension.

Genetic resistance to wheat streak mosaic can also reduce the risk of severe disease problems. There are currently a few varieties adapted to Kansas that have wheat streak mosaic resistance, including KS Dallas (red), Guardian (red), Oakley CL (red), Joe (white), and Clara CL. All of these varieties have the same resistance source (WSM2). This resistance helps, but does have some serious limitations.  For example, this resistance is effective against wheat streak mosaic but does not cover triticum mosaic or high plains (two other viral diseases also spread by the wheat curl mites). The resistance conferred by WSM2 is also temperature sensitive and is much less effective at high temperatures, although the resistance in KS Dallas seem to endure greater temperatures before breaking down.  If wheat is planted early for grazing or if high temperatures persist into October, the resistance is much less effective. KS Silverado (white) also has temperature sensitive resistance to wheat streak mosaic, although from a different source other than WSM2.

In addition, there are a handful of varieties with resistance to the wheat curl mite, including TAM 112, Byrd, Avery, Langin, KS Western Star, Whistler, Canvas, Guardian, Crescent AX, Incline AX, Fortify SF, TAM 115, TAM 204, and T158. These varieties are actually susceptible to the viral diseases, but they generally slow the development of the mite populations in the fall.  This resistance can help reduce the risk of severe disease but will not provide enough protection if wheat is planted in close proximity to volunteer wheat or other hosts infested with large populations of the curl mites and virus.

MANHATTAN, Kan. — Registration is now open for a webinar that will help Kansas beef cattle producers prepare to manage and reduce the impacts of drought and reduced forage availability on cow herds.

The webinar will be hosted by the Kansas State University Department of Animal Sciences and Industry and K-State Research and Extension via Zoom on Thursday, July 9, at noon (CDT).

“As the saying goes, failing to plan is planning to fail,” said K-State beef specialist Sandy Johnson. “This webinar is being conducted to help cow-calf producers evaluate the options they have to make strategic adjustments in response to reduced forage availability. We want producers to be prepared to take advantage of opportunities that may arise given current resources, markets and weather.”

The program features strategic reduction of grazing pressure, drought supplementation of cows, early weaned calf nutrition and management, and calf health considerations, presented by members of the K-State beef extension team.

Register for the webinar online at https://tinyurl.com/KSUBeef-Drought-Preparedness or at www.KSUBeef.org. For questions about the event or to register, contact Lois Schreiner, lschrein@ksu.edu, or 785-532-1267.

MANHATTAN, Kan. — Kansas farmers participating in the first-ever Virtual Wheat Field Day last week got an early report on two hard red winter wheat lines expected for release later this year by Kansas State University.

K-State wheat breeder Allan Fritz said two new lines planned for central Kansas growing conditions show promise for leaf rust resistance, and have performed well in university trials.

“We don’t have names for these yet, so right now they’re referred to by their experimental numbers,” Fritz told viewers during the field day, held May 27-28.

One variety, KS09049K8, is the offspring of two Kansas varieties – Duster and Overley – “with a little bit of spring wheat from CIMMYT,” the International Maize and Wheat Improvement Center that has headquarters in Mexico City, Mexico, according to Fritz.

“It’s a medium early variety, and is really the culmination of our efforts to breed race non-specific lines for leaf rust resistance,” he said. “This holds up very well to leaf rust.”

Fritz said the new wheat line is “moderately tolerant” on acid soils, and has “very good” tillering capacity.

“Those of you who remember Duster will know that it is extremely high for tillering,” a term to indicate a wheat’s ability to form additional stems off the plant’s main shoot, thus increasing its potential for higher-yielding wheat.

The new line, Fritz added, doesn’t quite get to the capacity of Duster, but says he believes it will have good yield potential in central Kansas.

“The quality of this one is good, and the other thing I like about it is it does have some Hessian fly resistance,” Fritz said. “Hessian fly is not a huge issue around here, but it is nice to have some options out there to deal with Hessian fly, when necessary.”

The line is moderately susceptible to stripe rust, Fritz said: “The genes that give us durable resistance to leaf rust also work on stripe rust, but they’re just not quite as good, so they don’t give us as strong a resistance to stripe.

“But I would say the resistance is good enough to give you a broader window for fungicide application. With this line, you should have enough stripe rust resistance, so I would put it in the moderately-susceptible category. If it’s a stripe rust kind of year – like this year in many places – then you would definitely want to put a fungicide on it.”

Fritz stopped short of naming the new line, but noted he and others are considering a name to honor former U.S. Department of Agriculture entomologist Jim Hatchett, who was based in Manhattan and contributed to wheat breeding in the Great Plains, he said.

A second wheat line ready for release is currently known as KS12DH0156-88, which has lineage connected to an Oklahoma State University wheat named Gallagher.

“This one is more intermediate on acidic soils, so if you’re getting into soils with fairly low Ph levels, I might lean toward planting something else,” Fritz said. “But this one will handle soils with Ph levels down to at least 5 and maybe even a little lower than that.”

He called the quality of this wheat line “good, but not great” with yield potential on the higher end. “This one has been a bit of a race horse for us,” Fritz said. “It’s done really well in our trials, and that’s the history of Gallagher, as well.”

“Even though it’s a later-maturing line – and I would normally say later fits better in the north part of Kansas – this has actually been better in southcentral Kansas.”

Fritz said both of the lines he talked about are susceptible to fusarium and, thus, he does not suggest either as an option in no-till fields following corn.