This is article is authored by Dr. David Marburger, Dr. Jeff Edwards, Dr. Brett Carver, Robert Calhoun, Dr. Tracy Beedy, and Dr. Bob Hunger

As of right now, the 2015-2016 Oklahoma wheat production is estimated to be approximately 132 million bushels, which is about 34% greater than our 2015 production (Table 1) and 277% greater than production in 2014. Although the estimated harvested acres is lower than 2015, the statewide average yield is projected at 40 bu/ac, and this is a 14 bu/ac (54%) increase compared to 2015 (Table 1). Based on these projections, this would be the largest wheat production since 2012, but the average yield would be a new state record.

The 2015-2016 wheat growing season was unlike most years in Oklahoma, characterized by periods of plentiful rainfall and near optimal growing conditions at critical times. Most wheat was sown into soil with adequate moisture, allowing it to emerge rapidly. The sufficient rainfall and mild temperatures allowed for good fall growth and bumper forage yields. In fact, plants in many non-grazed fields were abnormally large and phenologically advanced going into winter, and there was some concern about winter-kill. With mild temperatures continuing into the winter months, this concern proved to be largely unfounded, and most plants moved to spring green-up without injury.

Similar to 2014 and 2015, January and February were dry months for the Southern Great Plains, and the ample forage growth quickly wicked moisture from the soil. As the wheat crop was coming out of dormancy, there was much concern that the dry conditions would quickly reduce yield potential. Fortunately, rain fell during early- to mid-March as the crop was greening up. This also helped provide grazed wheat the extra boost it needed to recover from grazing injury.

As the wheat crop progressed from green-up to flowering, rain continued to fall, but warmer than normal temperatures moved the crop along quickly, and at the time, most thought harvest would come earlier than normal. As we transitioned into grain fill, temperatures stayed at more ideal levels, favoring kernel filling.

Most wheat was mature in southwestern Oklahoma and in the central part of the state by the end of the May. Widespread rainfall at the end of May delayed most producers from beginning harvest until the first week in June. Dry weather during June allowed much of the wheat crop to be harvested quickly. Unfortunately, some areas of southwestern Oklahoma were plagued by regular and heavy rainfall events that delayed harvest towards the end of the month. Overall, harvest was pretty well wrapped up in the state by the end of June.

Yields throughout Oklahoma were very good overall, with field averages of 30 to 60 bu/ac being the norm. Field averages in the 60 to 90 bu/ac range were not uncommon, and there were even isolated cases of fields averaging over 100 bu/ac. Some producers expressed they will never see their yields this high again in their lifetime, and let’s hope they are wrong! Test weights throughout harvest remained at or above 60 lb/bu for early-harvested fields and did not drop much below the upper 50’s towards the end of harvest. This was a much welcomed change from the low test weights of 2015.

Other than bird cherry oat aphids and wheat curl mites, there were few widespread insect problems in 2015-2016. Aphids were not really on the radar screen of most producers until numbers ballooned in mid-March. As a result, it was not hard to find Barley Yellow Dwarf (BYD) as flag leaves and heads started to emerge. While there was quite a bit of purpling associated with BYD, there was not as much stunting as sometimes observed with early-season transmission of the virus. Wheat Streak Mosaic (WSM) was not as wide spread as in 2015, but it was still a significant issue for many producers in 2016. The favorable growing conditions likely reduced the impact of both BYD and WSM, and yield reductions were not as severe as they might have been in a more drought stressed environment.

Similar to 2015, stripe rust was the major foliar disease impacting wheat production in 2016. The devastation caused by the 2015 stripe rust epidemic had many producers more open to the idea of foliar fungicide application to susceptible varieties. Many fields throughout the state received at least one fungicide application, and anecdotal evidence from agricultural retailers indicates that Oklahoma wheat acres treated with a foliar fungicide in 2016 was more than double that treated in 2015. Variety trial results from Apache, Chickasha, and Lahoma indicate that producers were well justified in spraying many of these acres. Grain yield of the popular variety Ruby Lee, for example, was increased by 68 bu/ac at Chickasha when treated twice with a foliar fungicide. Our results at Chickasha also show the power of genetic resistance to disease in varieties such as Billings which maintained an 83 bu/ac grain yield without the assistance of a foliar fungicide. In addition to stripe rust, leaf rust was present, but it was at low levels in isolated areas and was not widespread throughout the state.

For information regarding the 2015-2016 OSU Wheat Performance Trials, visit the home page of wheat.okstate.edu. Yield results from all individual locations, as well as a two-page summary of all locations, are posted. For those of you also also interested in the fall forage variety trial information, you can find that here: http://wheat.okstate.edu/variety-testing/forage-yield.

This article is written by Dr. Bob Hunger, Extension Wheat Pathologist.

Department of Entomology & Plant Pathology – 127 Noble Research Center

Oklahoma State University – Stillwater, OK

405-744-9958 (work) – bob.hunger@okstate.edu

This likely will be my last OK disease update for a while as diseases have mostly “run their course” in Oklahoma and harvest has started.  However, I wanted to provide a follow-up on the late season root rots we saw at several locations across northern Oklahoma.  Symptoms and a description of the setting in the field all pointed to take-all in several of the samples, and Jen Olson in the Diagnostic Lab and I did find visual signs of the take-all fungus.  With further examination, Jen found lesions indicative of Rhizoctonia root rot, and subsequently, she isolatedRhizoctonia.  In another sample with whiteheads that to me appeared to be take all, Jen isolated Parastagonospora nodorum and Fusarium (most likely acuminatum as indicated by DNA sequencing).  In a third sample in which roots appeared clean but the lower stems were discolored, Jen isolated Rhizoctonia, but also more commonly Fusarium (again most likely acuminatum), Curvularia, and Parastagonospora.  Likely some of these were secondary.  So, the exact cause of the whiteheads is somewhat uncertain with Rhizoctonia root rot, take-all, and perhaps some Fusarium-induced root rot all involved.

Reports/excerpts of reports from other states:  Just to let you know, stripe rust appears to be a major disease up through the northern Great Plains and into the mid-east as indicated below.  In many of these states, producers are facing the dilemma of needing two sprays – one to control early season stripe rust and another at flowering to help suppress Fusarium head blight (scab).  We faced a similar dilemma here in Oklahoma but with an early application to control early season stripe rust and then perhaps a later one to control later season foliar diseases and or scab (in eastern/north-eastern OK).  All with low wheat prices, but without the fungicide yield and quality (test weight) would be hurt as with what happened last year.

North Dakota:  Dr. Andrew Friskop (Ast Professor/Cereal Extn Pathologist); North Dakota State University; May 23, 2016:  “Stripe rust was confirmed in two counties in North Dakota on May 23. One sample was from a winter wheat research plot near Fargo (Cass County), and the other was from a winter wheat variety performance trial in southwest ND near Hettinger (Adams Co.). This is approximately 10 days ahead of when stripe rust was detected in North Dakota last year. Given the susceptibility in popular spring wheat and winter wheat varieties, growers will be encouraged to scout especially with rain and dew in the forecast.”

Ohio:  Dr. Pierce Paul (Aso Professor); Ohio State University; May 24, 2016:  “Stripe rust continues to spread across the state of Ohio. This is the most widespread and the earliest I have seen this disease in the state in 13 years. Several varieties in fields south of interstate 70 and west of interstate 71 are severely affected, with substantial damage to the flag leaf well before flowering in multiple hot spots in some field. As we approach flowering in more northern counties, the reports continue to come in. Several fields have already been sprayed for stripe rust, but the dilemma facing most growers is whether to spray for stripe rust or wait to spray for scab in fields not yet at anthesis.”

Severe stripe rust in Ohio – Dr. Pierce Paul

South Dakota:  Dr. Emmanuel Byamukama (Ast Professor/Extn Spec – Plant Pathology); South Dakota State University; May 27, 2016:  “I scouted several winter wheat fields this week in East (Codington, Clark) , Central (Beadle, Hyde, Hand, Hughes) and West (Stanley, Jackson, Pennington) South Dakota and I found stripe rust in almost every field I scouted. The majority of these fields have stripe rust just starting while a few have moderate to severe stripe rust. Winter wheat is beginning to head and a few fields are at flowering. With more rain in the forecast, a fungicide may be necessary to manage stripe rust. The challenge is going to be needing another fungicide shortly for scab management. And with the wheat prices not encouraging, producers are concerned applying 2-3 fungicides in winter wheat this season.”

Severe stripe rust in South Dakota – Dr. Emmanuel Byamukama

Article written by Dr. Bob Hunger, Extension Wheat Pathologist

Department of Entomology & Plant Pathology – 127 Noble Research Center – Oklahoma State University – Stillwater, OK

405-744-9958 (work) – bob.hunger@okstate.edu

      This past week (Monday & Tuesday) I visited the Dr. Raymond Sidwell Station near Lahoma (Major County), and the variety trials near Cherokee (Alfalfa County) and Alva (Woods County) on my way to field days in the panhandle near Balko and Hooker (Texas and Beaver Counties).  Except for in the panhandle, wheat foliage is pretty much done for in Oklahoma.  Wheat in the panhandle was mostly in the kernel forming stage.  Diseases observed on the trip to the panhandle included stripe rust (some still actively sporulating), wheat streak mosaic/high plains, and barley yellow dwarf.  Samples submitted to the Plant Disease and Insect Diagnostic Lab also have tested positive for these viruses.  As indicated in the 14-May update, take-all/root rot has been confirmed from a couple samples received from across central and northern Oklahoma.  Take-all has been confirmed, but it appears another root rot also may be involved.  Jen Olson in the PDIDL is making isolations to help resolve exactly what is involved in terms of root rot disease.  In south-central Oklahoma Aaron Henson (Tillman County Extn Educator) indicated to me that wheat is variable in maturity but he estimates that some harvesting should begin in 1.5 to 2 weeks.  Heath Sanders (Area Extn Agron Spclt located in southwestern OK) indicated much the same – especially if the cool/wet weather becomes more seasonally hot and dry.

Reports/excerpts of reports from other states:

Cereal Rust Bulletin from the Cereal Disease Lab in Minnesota; May 18, 2016:  Highlights/reports in the Cereal Rust Bulletin include:

·        Wheat stem rust was found in a nursery in south central Georgia.

·        Wheat stripe is widespread in the U.S., now reported in 24 states.

·        Oat crown rust has now been reported in Texas, Louisiana, Mississippi, Alabama and North Carolina.

The link to this report is: http://www.ars.usda.gov/SP2UserFiles/ad_hoc/36400500Cerealrustbulletins/16CRB4.pdf

Kansas:  Dr. Erick De Wolf (Extn Plant Pathologist); Kansas State University; May 18, 2016:  “Wheat in central and south central Kansas is at the grain filling stages of growth with many fields at or near the milk stages of kernel development.  Stripe rust is severe in many fields that were not treated with fungicides this year.  Fields of susceptible varieties have stripe rust severity >80% on flag leaves in demonstration plots in Pratt, Kingman, Harper, Barber counties.  The disease was also severe in Ellsworth county were a fungicide demonstration plot had nearly 100% severity of the flag leaves.   The weather this week appears highly conducive for continued disease development and the risk of severe disease appears to be high in Northwestern and West Central KS where low levels of stripe rust have been reported on the flag leaves.  Varieties with genetic resistance are performing well with disease reactions very similar to what we saw in previous years.   To date, T-158, Gallagher, WB-Grainfield, TAM 114, WB Cedar, Sy- Monument have all had moderate levels of resistance to the disease.  This suggests that the race structure of the stripe rust fungus is similar to last year.  Low levels of leaf rust were observed in Kingman, Pratt, Barber and Harper Counties.”