The introduction of two-gene Clearfield technology and the release of an Oklahoma-developed two-gene Clearfield wheat variety have resulted in increased interest in the Clearfield system in the southern Great Plains. This has also resulted in several questions, some of which I will attempt to answer in this blog post. If you have specific questions regarding rates, timings, etc., I encourage you to contact your local BASF representative.
Are Clearfield wheat varieties GMO’s? No. The Clearfield system is a non-genetically modified crop herbicide tolerance technology.
What is two-gene technology and what does it mean? As the name implies, two gene Clearfield varieties have two copies of the gene that confers resistance to imidazolinone herbicides. Two gene varieties have “Plus” or “+” in the name (e.g. Doublestop CL Plus). In wheat two-gene technology provides the option of adding 1% v/v methylated seed oil (MSO) to the spray solution. In my experience, addition of 1% v/v MSO greatly increases Beyond efficacy on feral rye. Methylated seed oil should NOT be added to the spray solution for one-gene Clearfield varieties, as crop injury will occur.
What is the new OSU two-gene Clearfield variety? Doublestop CL Plus was released by OSU in 2013 and is marketed through Oklahoma Genetics Inc. It is a late to first hollow stem and late maturity (about the same as Endurance) variety with a wide area of adaptation. A few of the strengths of Doublestop CL Plus include yield potential, acid soil tolerance, test weight, and milling and baking characteristics. More information on Doublestop CL Plus can be found by clicking here.
Can I save seed from Clearfield varieties? No. The gene that confers the Clearfield trait is protected by a utility patent and new seed (registered or certified) must be purchased each year.
Can I grow a Clearfield variety two years in a row? The better question might be should you grow a Clearfield variety two years in a row? Multiple years of using the same herbicide or herbicide mode of action can result in herbicide resistance. Of particular concern is jointed goatgrass, which has the ability to hybridize with wheat. This ability to hybridize could result in a population of resistant jointed goatgrass in a fairly short time period. So, if jointed goatgrass is the primary weed problem, rotating crops and/or herbicide chemistries to avoid consecutive years of Clearfield technology is a good stewardship practice.
Other grasses, such as feral rye, do not have the potential to hybridize, but the potential for weed resistance is still there through selection pressure. In these situations, I would not be as concerned about two consecutive years of a Clearfield system, but would certainly switch herbicide chemistry for a year after that.
Ultimately, it is important to rotate crops and herbicide modes of action to ensure the longevity of the Clearfield system. Weed resistance is bad and it is worse if your farm is the epicenter of the problem. Clearfield stewardship guidelines are available from BASF by clicking here
This blog post is an abbreviated posting of our wheat forage results. For the complete report, consult OSU Current Report 2141 Fall forage production and date of first hollow stem in winter wheat varieties during the 2013-2014 crop year by clicking here.
As was the case across most of Oklahoma, our wheat plots were sown into dry topsoil in late September. Soils in southwest and northwest Oklahoma were extremely dry due to multiple years of drought, and wheat pasture was short in these areas of the state. Summer rainfall provided ample subsoil moisture in the central part of the state, but topsoil was largely dry through September. Rains fell across much of the state in October and provided the fuel needed to build wheat pasture. Unfortunately, these October rains would be the only significant rainfall events most of the Oklahoma wheat crop would receive .
Fall forage production by winter wheat at Stillwater and Chickasha averaged 3,240 and 2,580 pounds per acre, respectively (Tables below). There was a large group of varieties at Stillwater and Chickasha that produced statistically equivalent forage yield, and producers are encouraged to consider two and three year averages when available.
|Table 2. Fall forage production by winter wheat varieties at Stillwater, OK during the 2013-2014 production year.|
|—————lbs dry forage/acre—————-|
|OGI||Doublestop CL Plus||3,200||3,020||–|
|CWRF||Brawl CL Plus||2,980||2,860||–|
|Table 3. Fall forage production by winter wheat varieties at Chickasha, OK during the 2013-2014 production year.|
|–lbs dry forage/acre–|
|CWRF||Brawl CL Plus||2,830||–|
|OGI||Doublestop CL Plus||2,700||–|
First hollow stem data are reported in ‘day of year’ (day) format (table below). To provide reference, keep in mind that March 1 is day 60. Average occurrence of first hollow stem at Stillwater in 2014 was day 77. This was approximately five days later than 2013 and 25 days later than in 2012 and was the result of much cooler than normal temperatures. Unlike previous years, there was only about ten days difference among varieties in occurrence of first hollow stem.
|Table 4. Occurrence of first hollow stem (day of year) for winter wheat varieties sown in 2013 and measured in 2014 at Stillwater, OK|
|–day of year–|
|OGI||Doublestop CL Plus||80|
|CWRF||Brawl CL Plus||83|
Wheat disease updates are written by Dr. Bob Hunger, OSU Extension Plant Pathologist
Oklahoma: Wheat around Stillwater is mostly at GS 10.5.1 (start of flowering) and is looking dry. With temps forecast in the upper 90s for the next 3-4 days and no rain, conditions will continue to deteriorate. Areas in other parts of the state are worse, with only a few areas better.
This past week I traveled from to southwestern OK stopping at numerous fields along the way as well as the variety trials or demonstrations at Kingfisher (60 miles southwest of Stillwater), Granite (southwestern corner of OK) and El Reno (20 miles west of OKC). Typically wheat was at my knee height or shorter and thin. I saw no foliar diseases, but did find several locations where I believe wheat streak mosaic and/or high plains disease was present. Samples are being evaluated to confirm, but samples processed by the Diagnostic Lab this past week from the panhandle and from central OK would support this (i.e., positive for Wheat streak mosaic virus and/or High plains virus). I also have noted symptoms of barley yellow dwarf in my trials around Stillwater, but no stunting is associated with these symptoms most likely indicating a spring infection. I did have a report from Roger Musick in central Oklahoma that he found a high incidence of tan spot and light leaf rust in a no-till wheat field under pivot irrigation. That is the only confirmed report of foliar disease I have received.
Reports/excerpts of reports from other states:
Mississippi Dr. Tom Allen (Extn Plant Pathologist, Mississippi State University) 03-May-2014: Wheat throughout MS ranges from flowering north of Highway 82 to wheat that has likely reached ripening stages south of I-20 (I haven’t seen as much of that wheat in more than 2 weeks).
Trace levels of wheat rust were observed in the Greenwood, MS area on Tuesday by a chemical distributor field rep. I confirmed the observation by text photo. In addition, I was able to find a few stripe rust infected leaves on the experiment station in Stoneville last Friday. I haven’t made much about the stripe rust confirmation because the plants were volunteer plants under a rainout shelter. I was shocked to see that most of the infected leaves had already formed telia as a result of the warmer temperatures. At present, we have not confirmed stripe rust in either a commercial field, variety trial plot, or any other part of the state.
Quite frankly, this is one of the cleanest wheat crops I’ve observed. Until the past week the only observable diseases were bacterial leaf streak throughout much of the state and Barley yellow dwarf virus. I rated the variety trial south and west of Hattiesburg a few weeks ago and also observed a low level of scab at that location. Some Septoria leaf blotch has been observed, tan spot in a few fields in eastern MS, and some glume blotch. In addition, since we were so wet and cold throughout much of the winter, and the rain continued, field work has been way behind so we’re starting to get some calls regarding glyphosate drift as well as paraquat.
Arkansas (Dr. Jason Kelley (Assoc Prof; Wheat & Feed Grains; Univ of Arkansas) 02-May-2014:
This week I visited several wheat fields around the state and looked through the plots that I have at the Lon Mann Research Station at Marianna. Overall I would say the crop is later than it was last year, which seemed very late. Many fields in central Arkansas heading this week, fields in south Arkansas generally headed last week and by this time next week most fields in Northeast Arkansas will likely be fully headed. According to the Arkansas Agricultural Statistics Service report, for the week prior to April 28th only 17% of the crop had headed. This compares to 67% for the five year average and 32% last year.
Overall the crop looks okay, but I can tell the last few weeks of rain has taken a toll on it with yellow pockets of wheat from mud holes is more common than it should be. Foliar disease levels have been low with the exception of Septoria leaf blotch, which is common in most fields lower in the canopy, but has moved up the plant in the last week on more susceptible varieties. I found a small hot spot of stripe rust on Wednesday April 30th at my plots at Marianna. This was the first reported stripe rust in the state. At this point with most wheat headed, heading or will be headed by the end of next week, stripe rust will most likely not have enough time to get well established and be a big issue this year.
I have been out in much of the state with wheat field days this week and wanted to share a few observations. Drought conditions are worsening in most wheat producing areas of the state and yield potential is declining fairly rapidly. An area roughly extending from Chickasha to Enid along highway 81 still has some potential, provided that that we receive rain soon. The same can be said for a few small pockets of wheat that received rain earlier this spring in Alfalfa, Grant, and Kay counties. With temperatures predicted to climb to the upper 90’s next week, however, the potential in these areas could decline rapidly. Most other areas of western Oklahoma have very limited or no yield potential remaining.
The effects of the April 15th freeze are still showing up in the Oklahoma wheat crop. We have several fields with lots of tillers but few heads. Most wheat south of Hwy 51 in Oklahoma is as fully headed as it is going to get. That is, the heads that were not killed by the freeze are fully emerged. Tillers that still look yellow or even green but are not headed out most likely have dead wheat heads inside. These can easily be identified by splitting the stem and examining the wheat head as shown in the pictures below.