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Wheat Disease Update – 19 May 2016

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.”

OSU to open new Lahoma research station facility in honor of Raymond Sidwell on May 13

LAHOMA, Okla. – The life’s work of the late Raymond Sidwell of Goltry is continuing to provide benefits to agricultural producers across the region, thanks to a new facility that bears his name at the Oklahoma State University Division of Agricultural Sciences and Natural Resources’ North Central Research Station.
OSU to open new Lahoma research station facility in honor of Raymond Sidwell on May 13

Bambi (front), Brady (left) and Brenda Sidwell gear up for the grand opening of the Dr. Raymond Sidwell Research Facility on May 13

“We can think of nothing more suitable than to have our new Dr. Raymond Sidwell Research Facility’s grand opening be part of our May 13 Wheat Field Day, as Raymond worked diligently for decades to make the annual field day one of the premier agricultural events in the Southern Plains,” said Tom Coon, OSU vice president for agricultural programs.

Sidwell served as senior station manager for the 143-acre experiment station, located in the heart of wheat production country near Lahoma, from June of 1980 until his passing in December of 2013.

“We invite everyone to join us as we honor Dr. Sidwell and showcase the importance of crop research being conducted through our statewide Oklahoma Agricultural Experiment Station system,” Coon said. “Lahoma is situated on Highway 60 just west of Enid, for those who have never been to the experiment station. Signs will be posted.”

There is no cost to attend the 2016 Wheat Field Day, which will take place from 8:30 a.m. to approximately noon. Lunch will be provided free of charge thanks to the generosity of several sponsors.

Richard Austin, current station superintendent, said the state-of-the-art Dr. Raymond Sidwell Research Facility has a conference room, offices and restrooms compliant with the Americans with Disabilities Act, and features a large open bay design that will facilitate equipment and make possible field day events unimpeded by weather.

“There is a lot of orange integrated into the building, signifying it is an OSU facility, which everyone who knew Raymond recognizes would be important to him,” Austin said.

In addition, Sidwell was known to be fond of porches, so one was incorporated into the front of the facility.

“It’s a nice touch people can enjoy, allowing those who visit the facility to be outside but out of the sun and hopefully remember what Raymond meant to Oklahoma agricultural producers and agribusinesses,” said Randy Raper, OAES assistant director.

More than three decades of Sidwell’s meticulous management of the station allowed for major research efforts in wheat breeding and variety development, soil fertility, weed science, soybean varieties and cropping systems, grain sorghum variety trials, plant pathology and entomology.

Through station educational activities such as the annual Wheat Field Day, Sidwell hosted literally thousands of guests over the years, including agricultural producers, commodity groups, foreign dignitaries, national and state legislators and numerous other officials, representatives and individuals from the public and private sectors.

“Dr. Sidwell was an important part of our Wheat Improvement Team, working to ensure wheat growers were able to take advantage of improved crop varieties and research-based best management practices,” Coon said. “He really was one of the great ambassadors of the land-grant mission, helping Oklahomans improve the quality of life for them, their families and their communities.”

The Sidwells – Raymond, his wife Brenda and their children Bambi and Brady – have long been highly regarded members of Oklahoma’s agricultural and agribusiness communities, and are recognized by their farmer peers as very progressive and proactive production agriculturalists.

An OSU agricultural economics alumnus and president of Sidwell Seed and the newly established Enterprise Grain Company located in Kremlin, Brady Sidwell said his father implemented many science-proven practices into the family operation that were backed by cutting-edge research done at the North Central Research Station under his guidance.

“Our family is both extremely proud as well as humbled to have this opportunity to honor our father in such a way,” he said. “Research and Extension programs at land-grant institutions play a critical role in Oklahoma and American agriculture.”

Sidwell added the family is grateful to be able to do their part in further promoting the work being done by the OSU Wheat Improvement Team.

“As a longstanding certified seed wheat producer, we will continue to utilize the best-in-class seed genetics being released by OSU every year and know that the new Dr. Raymond Sidwell Research Facility will only help this already well-respected program reach new heights,” he said.

For Bambi Sidwell, she always knew how passionate her father was about agriculture, in general, and wheat improvement, in particular.

“Growing up on our family farm near Goltry, our dad had an excitement about continuously improving wheat production,” she said. “He enjoyed sharing ideas with other producers that would have a significant and positive impact on people’s lives and their farming operations. Our dad was keen on maintaining a meticulously clean operation, something we strive to continue today.”

An OSU agribusiness alumna, Bambi said the family is proud to be able to take part in honoring her father in a way that enhances research and educational programs conducted at the Lahoma experiment station. Funding for the new facility was made through the Sidwell family, the Sitlington Trust and OAES.

Wheat disease update – 16 April 2016

Wheat disease updates are written by Dr. Bob Hunger, OSU Extension Plant Pathologist

OklahomaI had limited trips outside of Stillwater this past week, and only was able to contact one County Educator before writing this today.  Wheat around Stillwater is mostly at various stages of head emergence.  I did see a few anthers on scattered heads, but not many.  By contrast, Aaron Henson (County Educator; Tillman County in south-central OK) indicated wheat in his area is mostly at flowering.

During this past week, I had several calls about spraying wheat with a fungicide.  Although rust (stripe and leaf rust) didn’t appear to increase this past week, conditions reverted to being more favorable for stripe rust development with rainfall, increased dews, and favorable temperature.  With more rains and cool temps in the forecast, stripe rust could “reactivate” again, and leaf rust will start to come into the picture.  Wheat is now at the point where it will quickly move past the stage (the start of flowering) where it can be sprayed with most fungicides.  As far as I know, all wheat foliar fungicides (with the exception of Prosaro) must be applied prior to the start of flowering (Feekes’ growth stage 10.5).  Prosaro can be applied through growth stage 10.5.1, which is when flowering is just starting (anthers emerged mostly from the middle of heads).  Be sure to read all labels regarding a fungicides use on wheat.  There also are varying pre-harvest intervals (PHIs) required for the various fungicides, and often the length of time from heading to harvest can be short in Oklahoma.  So, be aware of these PHIs, and spray accordingly.

Active sporulation of stripe rust still can be found around Stillwater and the surrounding area.  Stan Fimple (County Educator, Pawnee County just to the northeast of Stillwater) sent me the following photos showing active stripe rust.  The photo on the top shows an actively sporulating “stripe” of strip rust (yellowish-orange in color), whereas in the photo on the bottom in the “stripes” you can see dark, blackish specks (teliospores) starting to appear.


Active spore stage of stripe rust

Active spore stage of stripe rust

Survival spore stage of stripe rust

Survival spore stage of stripe rust


Other than this, I have seen scattered leaf rust pustules on lower leaves around Stillwater, and powdery mildew also has become more apparent around Stillwater and at Lahoma as reported by Dr. Brett Carver (OSU Wheat Breeder).  However, both of these diseases are at low levels on lower leaves but with coming rain and cool temperatures both (especially leaf rust) could continue to increase on the upper canopy.  Around Stillwater, barley yellow dwarf spots continue to be observed but the aphids are now gone or at least in much lower in frequency.  If heavy rains come over the next 3 or so days, I would imagine aphid populations will be mostly eliminated.

Finally, I want to raise awareness once again to Fusarium head blight (scab) of wheat.  When wheat flowers it is susceptible to infection by the Fusarium fungus that causes scab.  That time is quickly approaching. Occasionally Oklahoma has problems with this disease, typically more so in eastern/northeastern Oklahoma than through the central and western parts of the state.  However, scab was severe across the state for a couple years around 2010 and there also was some reported last year.  For more information on scab, please see PSS-2145 (Fusarium Head Blight (Head Scab) of Wheat:  Questions & Answers) and PSS-2136 (Considerations when Rotating Wheat Behind Corn) that can be found at: wheat.okstate.edu.  An additional resource is the Fusarium Head Blight Prediction Center at http://www.wheatscab.psu.edu/.  At this site you can read commentaries submitted by specialists from each state but more importantly see if weather conditions in your area have been conducive to development of FHB.  The site is easy to use and especially may be beneficial in helping make fungicide application decisions.

Reports/excerpts of reports from other states:

Louisiana:  Dr. Stephen Harrison, Wheat & Oat Breeder, Louisiana State University, Apr 15, 2016:  My research associate (Kelly Arceneaux) is at the Rice Research Station in Crowley (Southwest) Louisiana rating plots today.  We plant a double-headrow set of a number of nurseries every year for disease screening at this location in collaboration with Don Growth (rice pathologist).  This site is inoculated with scabby corn but is not misted due to the abundance of humidity and free moisture at this site.  Nurseries include: Statewide Variety Trial, Uniform Southern Soft Red Winter Wheat Nursery, Uniform Southern Scab Nursery, Sunwheat, GAWN.  Kelly reports that stem rust is heavy and widespread at this site.  Leaf rust is moderate and scab is at an intermediate level, which is good for distinguishing lines.  The earliest plots are starting to mature, probably just past soft dough, while the latest lines are just past heading or not vernalized and not going to head.  We only received about 50% of our normal vernalization hours this winter and quite a few lines in the statewide variety trials will not be harvested due to vernalization issues.

Nebraska:  Dr. Stephen Wegulo, Extn Plant Pathologist, University of Nebraska, April 14, 2016:  “On Friday April 8, Jenny Rees, UNL Extension Educator, found trace amounts of stripe rust in a wheat field in Nuckolls County in south central Nebraska.  Earlier this week, samples from several wheat fields in Banner County submitted to the lab of Dr. Bob Harveson (Extension Plant Pathologist) at UNL’s Panhandle Research and Extension Center in Scottsbluff were positive for stripe rust and leaf rust.  This week on April 12 and 13 I surveyed wheat fields in the southernmost tier of counties in southeast, south central, and west central Nebraska.  Dry weather which has prevailed over the last two weeks or so stopped rust development.  I did not find rust in any of the fields I visited in the southernmost tier of counties.  Several fields showed symptoms of stress from lack of moisture.  Today I looked at research plots at Havelock Farm here in Lincoln (Lancaster County) and at the Agricultural Research and Development Center (ARDC) near Mead (Saunders County, about 35 miles north of Lincoln).  I found a few hot spots of stripe rust at Mead (see first attachment), mostly on the lower leaves.  I also found trace levels of leaf rust at Mead (second attachment).  Powdery mildew was the predominant disease at Lincoln and Mead, but I also saw significant levels of Septoria tritici blotch in one research field at Mead.  Wheat growth stage across the state ranges from Feekes 5 and 6 (most fields) to Feekes 7 in some irrigated fields.”

South Dakota:  Dr. Emmanuel Byamukama, Extension Plant Pathologist, South Dakota State University; Apr 13, 2016:  “Several winter wheat fields in central South Dakota were scouted yesterday for stripe rust. One field originally found with stripe rust last week was the only one we found with stripe rust. Stripe rust was found on old/dying leaves and some of the leaves had teliospores, indicating the source of this rust would have been from overwintered stripe rust in South Dakota.”


Wheat disease update – 02 April 2016

Wheat disease updates are written by Dr. Bob Hunger, OSU Extension Plant Pathologist

Wheat has advance in maturity across OK this past week flag leaves definitely are emerging around Stillwater.  From reports I’ve received I believe across the state wheat ranges from flag leaves emerging to heads starting to emerge (although wheat in far northwest OK and the panhandle may not be quite as far along).  I didn’t hear specifics but was told that freeze damage has been observed around Kingfisher in central OK.  With frost/freezing temps again last night, additional damage is possible.  Drought, although not as bad as last year, also is creeping back into the picture.  One producer from southwestern OK indicated to me that “leaves are rolling-up at 2 o’clock in the afternoon.”  I didn’t see any wheat that looked stressed, but in several locations had to dig 4” or more to find moist soil.

In my trips this past week to central OK (Watonga) and to more north-central OK (Blackwell), I could find stripe rust, but it doesn’t appear to me that it had advanced (become more severe).  In fact, Zack Meyer (Extn Educator; Kingfisher Cnty) sent me the following photo that shows the telial spore stage of the stripe rust fungus forming on wheat leaves.  Look closely at the photo and you can see minute yellowish-orange pustules of stripe rust also present on the leaves (especially the greener leaf).  The telial stage is considered more of a survival spore stage and indicates that stripe rust is encountering unfavorable conditions and starting to shut down.  Although this is good news, stripe rust can quickly “reactivate” if favorable temperature and moisture are resumed.

Telial/uredinial pustules of the stripe rust fungus. Zack Meyer; Extn Educator; Kingfisher Cnty

Telial/uredinial pustules of the stripe rust fungus. Zack Meyer; Extn Educator; Kingfisher Cnty


Unfortunately there also is a lot of active stripe rust still in the state as I have had numerous calls from across OK to discuss spraying options, and Greg Highfill (Extn Educator; Woods Cnty) sent me the following photo showing moderate/severe and active stripe rust on wheat in northern-central OK.


Photo credit:  Greg Highfill - Extn Educator; Woods Cnty in northern-central OK

Photo credit: Greg Highfill – Extn Educator; Woods Cnty in northern-central OK


Reports/excerpts of reports from other states:  No reports from Texas, but did hear the following from Kansas and Nebraska.

Kansas:  Dr. Erick DeWolf; Extn Plant Pathologist; Kansas State University; Manhattan, KS; Apr 1, 2016:  “The Kansas wheat crop is progressing rapidly through the jointing stages of development in much of the state.  Wheat in the Southeast portion of the state is at or fast approaching flag leaf emergence.  The crop is generally considered to be two or three weeks ahead of schedule.

Scouting reports indicate that stripe rust is becoming established in the 2016 wheat crop.  This past week, stripe rust was reported in many counties in central and eastern Kansas.  The disease is still at low levels in most fields with a few exceptions in Southeast Kansas.  This early establishment of stripe rust increases the risk of severe yield loss and growers should continue to monitor the situation carefully.  If weather conditions become favorable, the disease could spread rapidly from the lower leaves, where it is now established, to the upper leaves that are critical for grain development.  Leaf rust is still active in the western tier of counties bordering CO but remains a low levels in most fields.  Powdery mildew is severe in some fields in central and eastern Kansas.”



Nebraska:  Dr. Stephen Wegulo; Professor/Extn Plant Pathologist; University of Nebraska-Lincoln; Lincoln, NE, KS; Mar 31, 2016:  “Yesterday March 30, 2016: Jennifer Rees, UNL Extension Educator, found trace levels of actively sporulating leaf rust in wheat fields in Nuckolls County in south central Nebraska.  Nuckolls County is in the southernmost tier of counties that border Kansas.  She did not find actively sporulating stripe rust; however, in one field there was evidence of stripe rust that was active last fall.”


Colorado:  Dr. Kirk Broders; Ast Professor; Colorado State University; Ft. Collins, CO; Mar 29, 2016:  “As I mentioned last week stripe rust is now present in eastern Colorado with a confirmed report of stripe rust in the Prospect Valley region northeast of Denver. We have received several reports of stripe rust from that same region. This past week was windy with some precipitation in this area of Colorado, so spores were spread but there was limited moisture to promote additional infection.  There is rain in the forecast for this coming week and the rain is certainly needed for the wheat, but also will provide a favorable environment for stripe rust to increase because temperature is supposed to be staying in the 50s-70s for the days and 20s-40s at night. If you already have noticeable levels of rust in your field you may want to consider including a fungicide at tillering (GS 4) or when you make your herbicide application. If you do not currently have rust in your fields or in your region, I would recommend waiting until closer to flag leaf and monitor the spread of stripe rust in the state.  CSU Extension specialist Wilma Trujillo was able to examine wheat in the southwest part of the state near Lamar, where stripe was present last fall. We examined these leaves and found no evidence stripe rust was able to overwinter in this region of the state. It is still early in the season, but there is certainly the possibility for stripe rust to become a serious problem in the state again this year. There are also the threat of leaf rust we should not forget about. Leaf rust has been present in western Kansas for the last 2 weeks and has likely moved into eastern parts of the state. I have not received in specific reports, but would appreciate you feedback if you have observed either stripe rust of leaf rust in you fields.

Bird cherry oat aphids in wheat: showing up in large numbers

By Tom Royer, OSU Extension Entomologist

I have received several reports of (and photos, Figure 1) of bird cherry oat aphid (BCOA) numbers in winter wheat that will require treatment with an insecticide

Bird cherry oat aphid

Bird cherry oat aphid


Severe bird cherry oat aphid infestation

Severe bird cherry oat aphid infestation

Bird cherry oat aphids are small (2mm) olive-green aphids with a red-orange patch surrounding the base of each cornicle (Figure 1). Old, wingless, overwintering adult aphids are darker, almost black.  At this time, you may also find winged aphids that have moved in to the field (Figure 2).

Winged bird cherry oat aphid

Winged bird cherry oat aphid

What are my suggestions regarding control of bird cherry oat aphid in winter wheat?

  • Unpublished research provided by Dr. Kris Giles (OSU) and Dr. Norm Elliott (USDA-ARS) along with studies conducted in South Dakota, Minnesota, and North Dakota on spring wheat indicated that BCOA causes yield loss before wheat reaches the boot stage. Approximately 5-9% yield loss occurs when there are 20-40 BCOA per tiller (average 7%).
  • Visible damage from bird cherry-oat aphid is not very noticeable so infestations may go unnoticed. It is very important to check fields for infestations and make treatment decisions only after a field has been checked.

My suggestion for making a treatment decision is as follows:

If greenbugs and bird cherry oat aphids are both present, use Glance n’ Go to scout, which can be accessed at http://entoplp.okstate.edu/gbweb/index3.htm.  Published research from Giles and Elliott showed that Glance n’ Go sampling will work with both aphids if they are both present.

If bird cherry-oat aphid is present alone, count the number of aphids present on each of 25 randomly-selected tillers across a zigzag transect of the field. The reason that you can’t use Glance n’ Go is that the most available research suggests that the threshold is too high to effectively use Glance n’ Go.

Look for evidence of parasite activity in the form of mummies (Figure 3).  A rule of thumb is that if 5-10% of the aphids are mummies, more than 90% are already parasitized.  If mummies are not present, use the guidelines below to make a treatment decision.

Parasitized bird cherry oat aphid

Parasitized bird cherry oat aphid

If, after thoroughly scouting your field, you can identify that infestations are spotty, consider spot spraying with a ground rig.

Use the YIELD LOSS TABLE to determine a potential YIELD LOSS from the aphids.  Then estimate your CROP VALUE and calculate your CONTROL COSTS.  Use those numbers to estimate PREVENTABLE LOSS.    If estimated PREVENTABLE LOSS is greater than CONTROL COSTS, Treat; otherwise, Don’t Treat.


Here is an Example:


Step 1:  Estimate YIELD LOSS:


  • Total # aphids_______525___________/25 tillers = average # aphids/tiller_____21_____


Step 2:  Estimate CROP VALUE:  (Crop Value = Yield potential X Price per bushel)

  • Yield potential__40____ bushels/acre X price per bushel $____4.50____ per bushel


CROP VALUE = $___180____


Step 3:  Estimate CONTROL COSTS: (Control Cost = Insecticide Cost + Application Cost)


  • Insecticide cost $___6_____ /acre  +  Application Cost       $ ____3_____/acre


CONTROL COSTS $_____9_____/acre


Step 4:  Estimate PREVENTABLE LOSS (Crop Value X Yield Loss from Aphid)


  • Crop value/acre $___180_____  x Yield Loss from aphid ___0.07_____


PREVENTABLE LOSS $____12.60______/acre


IF PREVENTABLE LOSS $___12.60_____ is greater than CONTROL COSTS $___9.00_____ TREAT


IF PREVENTABLE LOSS $________ is less than CONTROL COSTS $__________                                   DON’T TREAT


Check CR-7194, “Management of Insect and Mite Pests in Small Grains” for registered insecticides, application rates, and grazing/harvest waiting periods.

It can be obtained from any County Extension Office, or found at the OSU Extra Website at http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-2601/CR-7194web2008.pdf

Wheat disease update – 19 March 2016

Wheat disease updates are written by Dr. Bob Hunger, OSU Extension Plant Pathologist

Oklahoma:  This past week I looked at wheat around Stillwater as well as in central OK (Blaine County NW of Oklahoma City; Kingfisher just NW of OKC; Apache in Caddo County SW of OKC), and in SW OK around Altus.  I saw wheat as far along as approaching flag leaf emergence to at growth stage 6-7.  The more advanced wheat typically was planted relatively early and not grazed.  Everywhere I was had sufficient moisture, although areas in southwestern and western OK were getting to a point where some rain definitely would be beneficial.  In addition to my observations, I’ve received numerous reports that I’ll summarize here.

At nearly all the places I stopped, I observed varying levels of stripe rust, leaf rust, aphids, and powdery mildew, with powdery mildew being by far the least prevalent.  Stripe rust typically was scattered across fields, but there were some significant hot spots.  In some fields (for example the variety trial at Kingfisher) I saw no stripe rust.  Greg Highfill (Extn Educator, Woods County) and Darrell McBee (Extn Educator, Harper County) sent me the photo below showing stripe rust they found this past week.  They indicated the stripe rust was scattered and not common, but this does mean that spores are present in the field and will increase with favorable (cool and wet) weather.  They also indicated finding a little powdery mildew.  I also heard reports of severe stripe rust in susceptible varieties such as Pete, Garrison, and Everest.


Stripe rust in northwestern Oklahoma - Photo courtesy Greg Highfill and Darrell McBee

Stripe rust in northwestern Oklahoma – Photo courtesy Greg Highfill and Darrell McBee

More severe hot spots of stripe rust were reported by David Nowlin (Extn Educator; Caddo County), who sent the following photo of stripe rust on ‘Pete’, which is highly susceptible to stripe rust.

Stripe rust in Pete in Caddo County - photo courtesy David Nowlin

Stripe rust in Pete in Caddo County – photo courtesy David Nowlin


Similar reports regarding stripe rust were made by Dr. Brett Carver.  He also has reported seeing considerable chlorosis (yellowing) often with the lack of sporulation.  I saw the same type of yellowing with no sporulation at Kingfisher yesterday (see photo below).  I’m not sure of the cause of this yellowing, but I don’t believe it to be from rust or other foliar diseases because it is widespread in its distribution on lower leaves.  Perhaps it is the result of the environment.

Yellowing in wheat at Kingfisher

Yellowing in wheat at Kingfisher

In no-till fields near Altus and Apache I saw striking tan spot on lower leaves along with numerous pseudothecia of the tan spot fungus on the wheat residue in the field.  Near Altus, this was combined with stripe rust presence such as described above.  In such a case, applying a fungicide early to catch both of these diseases should be considered, especially if the field at this point has a good yield potential.  For more information to help make this decision, see OSU CR 7668 available at www.wheat.okstate.edu

tan spot

tan spot


Reports/excerpts of reports from other states:  

Texas : I’ve only received two reports from Texas this past week.  One is from a former student that now lives in the Weatherford, TX area.  He indicates that stripe rust is in the area.  The other report is from David Nowlin (Extn Educator, Caddo County), who indicates a colleague of his located near Denton, TX sent him the following report on 15-March.

“We’re getting hammered with strip and leaf rust as well as powdery mildew on our varieties down here in Denton, TX. We’re just a little further ahead of you. Wheat is not as far along as we normally see.

Kansas:  Dr. Erick DeWolf; Extn Plant Pathologist; Kansas State University; Manhattan, KS; Mar 19, 2016: “The wheat crop is growing rapidly throughout Kansas. The crop in the more advanced fields are approaching jointing in the northwest and are about a week away from flag leaf emergence in the south central and southeast portions of the state.  The crop is generally considered to be about 3 weeks ahead of schedule with respect to normal growth and development. There are multiple reports of leaf rust and stripe rust in Texas, Oklahoma, and other surrounding states.

The Crops Extension team has been busy scouting for disease in recent weeks. We are finding active leaf rust and stripe rust in the state. Leaf rust was reported in west central and northwest, Kansas with most activity in counties bordering Colorado. Low levels of leaf rust were also observed in research plots in Riley County, which is located in northeast Kansas. The winter has been very mild in Kansas and it is very likely that the leaf rust has overwintered in the state. Stripe rust was reported in multiple counties this past week. Stripe rust is generally at very low levels with most activity reported in the southeast portion of the state.  Tan spot and powdery mildew have also been reported in some areas of the state.”



Freeze injury update 21 March 2016

Temperatures over the weekend were cold enough to cause injury to the Oklahoma wheat crop. As shown in the figure below from the Oklahoma Mesonet many areas of Oklahoma spent several hours below 28F. While temperatures in the wheat canopy might have remained slightly higher than reported air temperatures, they were still probably low enough to result in significant injury to wheat.


Hours spent below 28F March 18 - 20

Hours spent below 28F March 18 – 20


A few points I would encourage everyone to consider:

Every freeze event is unique – the temperatures and time durations we use regarding freeze injury are rules of thumb and are not exact. I have seen instances where conventional wisdom would indicate complete crop loss and we skate through with minimal damage.
It will take a few days to see how bad things are – Symptoms may start to appear later this week and will likely be clearly identifiable by the end of this week. Healthy wheat heads will remain turgid with a green color. Damaged wheat heads will be bleached, yellow, or brown and will easily break when pushed against. I anticipate that we will not have any partial “blanking” of wheat heads and that most wheat heads will either be okay or a complete loss. This post from last year has some pictures showing tell tale signs of freeze injury. The linked post also serves as a reminder that while freeze is the concern of the day, the potential worsening of drought conditions in NW Oklahoma has the potential to do far more damage.

% damaged heads might not = % yield loss –  It is still relatively early in the growing season and there is still opportunity for smaller (two nodes or less) wheat to produce additional tillers and/or retain secondary tillers. Whether or not these tillers are able to compensate for larger tillers that were lost due to freeze will depend on moisture and weather. IF (and that is a big if) weather conditions remain favorable, late emerging tillers in central and northern Oklahoma might still have a shot at producing grain. It will be tougher for more advanced wheat in southern Oklahoma to make this type of recovery.


Wheat disease update – 04 March 2016

Wheat disease updates are written by Dr. Bob Hunger, OSU Extension Plant Pathologist

Oklahoma –  Foliar diseases are becoming active in Oklahoma.  Around Stillwater I have found both leaf and stripe rust, powdery mildew, and septoria.  Incidence/ severity of all these foliar diseases is relatively light, but I am especially watching what happens to the leaf and stripe rust.  The leaf rust pustules are small and on lower/older leaves indicating that leaf rust likely overwintered in Central OK.  The stripe rust pustules were on the upper leaves of ‘Pete’ wheat (see photo) indicating the spores causing these initial infections likely blew up from the south.  With rain and cool wet weather in the forecast, I definitely expect for there to be an increase in foliar diseases.  Around Stillwater, I also have seen quite a few aphids (mostly bird cherry-oat but also a few greenbug) and many lady beetles.  However, no symptoms yet of barley yellow dwarf.


Stripe rust on Pete 03/04/2016

Stripe rust on Pete 03/04/2016

Gary Strickland (SWREC Dryland Cropping Systems Spclt – Jackson Cnty) relayed to me that in SW OK he has seen leaf rust in fairly high levels on lower leaves of Endurance and other wheats, and has heard reports of stripe rust but has not seen any himself.

Yesterday I traveled to north-central OK (Alva).  On the way there and while there I visited several fields and found a few very small leaf rust pustules.  Overall the wheat from I-35 over to Alva (Hwy 11) looked good and was greening-up nicely.  Also while in Alva, numerous producers, etc. relayed reports of mostly leaf rust showing up across central OK, such as leaf rust around Geary, OK, etc.

Regarding rust incidence/severity in Texas, I talked to a wheat breeder in Texas last week and he indicated that wheat in southern Texas was showing both leaf and stripe rust but had not yet reached a severe level.  Early next week I’ll be at a meeting of wheat pathologists and should be able to find out more about diseases in Texas.

All these reports indicate the potential for significant foliar disease on the current wheat crop.  Genetic resistance in some of wheat varieties helps protect against the foliar diseases, but fungicides also provide an excellent management tool to protect not only yield, but also quality (test weight).  To help with deciding if and when to apply a fungicide, Dr. Jeff Edwards and I earlier this week updated and revised CR 7668 (Foliar Fungicides and Wheat Production in Oklahoma – March 2016).  It can be found at www.wheat.okstate.edu.  This Current Report discusses the significant aspects related to using fungicides to manage wheat foliar diseases.

One point I want to be sure to emphasize when using fungicides is the importance to not exceed the maximum amount of a fungicide applied to a crop in a single year.  Such a consideration couldespecially be an issue when more than one fungicide application is made.  In many states through the southeastern region of the U.S., two fungicide applications on wheat are more common, with the last application typically targeted toward Fusarium head blight (scab).  In Oklahoma, where scab usually is not a concern, deciding when to make a single fungicide application typically is the only consideration.  However, if you have early disease pressure from stripe rust or have early season powdery mildew, tan spot, or Septoria leaf blotch in no-till fields, more than one application may be needed to adequately manage these diseases.  In these situations, care must be taken to insure label compliance.  For example, if an early application of a generic form of tebuconazole is applied at 4 oz/ac, a subsequent application of any fungicide containing tebuconazole around heading would put you over the 4 oz limit for the crop season.  Thus, be sure to read the label to determine the maximum amount of a chemical that can be applied in a single season and the exact amount of a chemical(s) that is in a fungicide.

South Texas – Amir Ibrahim TAMU Wheat Breeder – The wheat crop in our trials at Castroville and Uvalde, TX is at Feekes stages 5‐10, ranging from the latest winter to the earliest spring types. Growth is very lush and there is no winter kill or frost injury in either winter and spring types. Stripe rust is at 70S, in the medium to upper canopy, on our  ‘Patton’ spreader passes across the field. Stripe rust is about 60S on ‘TAM 110’. ‘Coronado’ is hammered with yellow rust at Castroville.  Stripe rust is more progressed at Uvalde. We have been getting natural and uniform stripe rust infection at Uvalde every year for the last few years. The Texas A&M AgriLife Center at Uvalde sits at the bottom of a valley with constant morning dew that favors infection. Stripe rust has also been found at low levels in the wheat breeding trials near Chillicothe in the Rolling Plains of Texas.

Texas – Dr. John Fenderson – WestBred.  “I saw rampant Stripe in Central TX on Ruby Lee.  I also saw it on sensitive lines from I-20 south anywhere it has rained.  Some spraying has occurred in the Austin area.  I also pulled wheat in the Red River corridor both sides with a lot of stripe on older leaves.  It is just waiting on the right conditions to explode.  I was all the way down in S. TX this week and I did not see stripe on the spring wheat but there was some on Winter wheat around San Angelo etc.”

First hollow stem update 03/04/2016

First hollow stem is the optimal time to remove cattle from wheat pasture (full explanation). This will be the last of the 2016 first hollow stem updates, as the vast majority of varieties are at or well past first hollow stem.

Keep in mind that the numbers reported from Stillwater are likely behind those being observed in southern Oklahoma and ahead of those observed in northern Oklahoma. The First Hollow Stem Advisor can provide an estimate of first hollow stem progress in your neck of the woods.

First hollow stem measured in wheat sown 09/15/2015 at Stillwater, OK. Varieties with ‘-‘ reached first hollow stem on a previous measurement date
Variety cm of hollow stem 03/04/16
Endurance 1.5
OK Rising
Ruby Lee
Doublestop CL Plus 1.57
NF 101
SY Monument 1.5
SY Flint
SY Llano
SY Drifter
SY Wolf
SY Razor
SY Grit
Oakley CL 1.74
Larry 1.8
Tatanka 1.81
Joe 1.1
LCS Pistol 1.68
LCS Wizard 1.43
LCS Mint 2.08
LCS Chrome 1.84
T158 1.5
Long Branch 1.73
TAM 112
TAM 204
TAM 114
AG Robust
Brawl CL Plus 1.26
Avery 1.97
OK1059060-3 1.91
OK10126 1.41
OK11D25056 1.55
OK12621 2.18
Stardust 2.24
OK12716R/W 1.16
OK11231 1.26
OK09915C-1 1.32
OK12912C 1.17

First hollow stem update 02/29/2016

First hollow stem is the optimal time to remove cattle from wheat pasture (full explanation). We measure first hollow in our September-sown wheat forage plots at Stillwater each year, and normally have approximately 50% of varieties at or past first hollow stem by March 1st. I have posted first hollow stem measurements from samples taken from these plots on 02/29/16 in a table at the end of this blog. Most wheat varieties are now at or well past first hollow stem.

Keep in mind that the numbers reported from Stillwater are likely behind those being observed in southern Oklahoma and ahead of those observed in northern Oklahoma. The First Hollow Stem Advisor can provide an estimate of first hollow stem progress in your neck of the woods.

First hollow stem measured in wheat sown 09/15/2015 at Stillwater, OK. Varieties with ‘-‘ reached first hollow stem on a previous measurement date
Variety cm of hollow stem 02/29/2016
Endurance 1.0
OK Rising 1.5
Ruby Lee 2.0
Duster 2.0
Doublestop CL Plus 1.4
NF 101
SY Monument 1.0
SY Flint
SY Llano
SY Drifter
SY Wolf 2.7
SY Razor
SY Grit
KanMark 1.5
Oakley CL 1.3
Larry 0.9
Tatanka 1.1
Joe 0.8
LCS Pistol 1.1
LCS Wizard 1.3
LCS Mint 1.4
LCS Chrome 1.2
T158 1.1
Long Branch 1.2
TAM 112 1.6
TAM 204 1.7
TAM 114 1.6
AG Robust
Byrd 1.7
Brawl CL Plus 1.1
Avery 1.1
OK1059060-3 1.4
OK10126 0.8
OK11D25056 1.1
OK12621 1.1
Stardust 1.0
OK12716R/W 1.1
OK11231 1.0
OK09915C-1 0.8
OK12912C 1.1
OK12DP22002-042 1.6