Wheat disease update – 09 April 2015

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

Oklahoma: On April 6, I traveled a route from Clinton (85 miles west of OKC) in west central Oklahoma going northeast through Custer County to Kingfisher (40 miles northwest of OKC) and then to Marshall (35 miles west of Stillwater). Although there was some good wheat on this route (e.g. the variety trials at Kingfisher and Marshall), it is posed to decline quickly unless rain is received. Most of the wheat I looked at in Custer County northeast of Clinton was small and fields were terribly dry. Wheat in this area seemed to be at GS 6-7 and I’m guessing was planted quite late due to the dry fall. The most common problem I saw were greenbug, especially in Custer County. However, as the photos show, there were many mummies present indicating the population should be crashing shortly. I also saw some stripe rust but only an infection here and there. Around the variety trial at Kingfisher, wheat was mostly around GS 9 and I saw no aphids or disease. At Marshall, wheat was at GS 8 and there was some stripe rust but at a low incidence.

Greenbugs and mummies in Custer County, Oklahoma

Greenbugs and mummies in Custer County, Oklahoma

On April 7, I traveled to Frederick in south central OK looking at wheat along the way. At a variety demo 20 miles west of OKC right at I-40, I found the wheat at GS 8 with just a little touch here and there of stripe rust. Soil moisture here looked good; this area must have caught a decent rain in the last week or so. The same could be said at another variety demo straight south about 15 miles south at Minco. Here the wheat in the field surrounding the demo was at GS 9, there was good soil wetness, and the wheat looked good. I did not see any rusts or powdery mildew, but there were occasional BYD spots. Further southwest near Apache (30 miles north of Lawton) wheat was at GS 9-10 and looked very good in the variety trial as well as in fields. However, some leaves were beginning to roll and the need for moisture to continue the crop was evident. I didn’t see any aphids or diseases in wheat west of Apache, but I the variety trial just south of Apache I found some stripe rust and greenbug; both at a very low incidence.

Wheat stripe rust

Wheat stripe rust

The rest of this trip was spent with Aaron Henson (Extension Educator, Tillman County) and Mark Gregory (Area Extn Agron Spec – SW Oklahoma) looking at wheat in Tillman County. Wheat in this area was mostly at GS 9-10 with awns occasionally just emerging from the boot. Some fields we visited were dry and impacted by drought, while others looked good but needed another drink soon. A few fields were outstanding and had good soil moisture. One field in particular was the best wheat I have seen since 2012. It was a field of Ruby Lee that was at GS 10 and had been sprayed on 15-Mar because of reports of severe stripe rust in the area and in northern Texas to the south. A 20 ft strip of unsprayed wheat was left on the outside of the north and west side of the field because of power lines and wind. This strip served as an excellent control to indicate the effect of the spray. The line between sprayed and not- sprayed was visible from the road and even more evident in the field (see photos). Within the not-sprayed strip, flag leaves were green with leaves beneath the flag hit hard with stripe rust (see photos). The field was sprayed a second time on 05-Apr because it has such good potential. Leaves in the sprayed area are completely green. I have difficulty explaining the complete lack of stripe rust on the flag leaves in the not-sprayed area. Likely the flag leaves were not yet emerged at the time of the first spray and then conditions after spraying did not allow spread of stripe rust to them. However, in talking to Aaron and Mark it seems there were conditions after the 15-Mar spraying that would have been conducive for spread of stripe rust. At any rate, this is an excellent example of how a timely spray did a tremendous job of protecting yield potential.

Stripe rust – note yellow cast to wheat in foreground that changes to deep green about halfway into phot


Signs of stripe rust were present in the lower canopy, but stripe rust was not present on flag leaves

Signs of stripe rust were present in the lower canopy, but stripe rust was not present on flag leaves

Fungicide-treated Ruby Lee in the same field as above photos

Fungicide-treated Ruby Lee in the same field as above photos


Other diseases observed across the Oklahoma include wheat streak mosaic, which has been detected in samples from several places including around Stillwater and from Noble County just north of Payne County (where Stillwater is located). However, I have not received indication yet of severe WSM; part of this may be related to the drought in western OK where WSM is typically more common. Recently samples from northwestern OK are beginning to come into the diagnostic lab, but results from some of those samples are still pending.


Reports/excerpts of reports from other states:

Texas Dr. Charlie Rush (Professor, Texas A&M AgriLife Research, Amarillo) 3-Apr-2015: “I haven’t checked all fields as closely as those around Bushland but there are a lot of GB and Russian wheat aphids as well as bird cherry.  Russian seems predominate in my fields.  We sprayed last week but will likely sustain significant yield loss from not spraying earlier.  I suspect we’ll start getting lots of calls and samples that end up being BYDV, although some WSM is also showing up.  Mild winter with more moisture than last few years has resulted in a crop that has looked very promising up to now but without good subsoil moisture what we had in the upper layers of the soil profile is disappearing fast and obvious symptoms of drought are beginning to appear.”

Wheat disease update – 16 March 2015

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

Oklahoma:  The leaf rust I saw around Stillwater in February seems to have “died out.”  The cold weather we had from late February into early March killed the lower leaves where leaf rust was active and conditions did not allow spread to younger leaves.  Dr. Brett Carver (OSU Wheat Breeder) confirmed this to me this morning as he indicated late last week he did not see any rust (leaf or stripe) around Stillwater or at his nurseries in Lahoma and Marshal.  This also is the case for northern and northwestern OK, as well as for KS (see Dr. De Wolf’s observations under “Other States” below).  Dr. Tom Royer and I visited variety trials at Cherokee and Alva last week.  No foliar diseases were observed but Dr. Royer did find a small greenbug colony on wheat in the field surrounding the Alva trial.  However, with mild temperatures and moisture predicted for the coming week and with inoculum to the south of us in Texas and southern Oklahoma, foliar diseases should be increasing in incidence and severity across central and northern OK.

Leaf and stripe rust are active in Texas (see Dr. Ron French’s observations below), and southern and central Oklahoma.  Mark Gregory (Area Extn Agron Spec – Duncan, OK) has reported seeing both leaf and stripe rust (but more stripe rust) across much of south-central and southwestern OK – especially around Grandfield, OK located north of Wichita Falls, TX.  Similar reports have come from Aaron Henson (Extn Educator; Tillman Cnty) and Gary Strickland (Exten Educator; Jackson Cnty).  Incidence has ranged from scattered to many “hot spots” of stripe rust, and from light to intermediate incidence of leaf rust.

Some of these fields (especially if it is a susceptible variety) will merit an early application of fungicide to curtail foliar disease activity (especially the stripe rust).  Be aware that applying a fungicide now will not last the entire season, and a second application toward head emergence also may be needed if weather continues to be favorable for foliar diseases.  For an early season application I recommend using a full rate (as opposed to a half rate) of a less expensive fungicide because there is so much time left in the growing season.  Then a later season application with a more expensive fungicide may or may not be needed.  Also be sure to not exceed the maximum amount of fungicide applied and to rotate chemistries to prevent resistance. Also consider your variety.  A variety like Ruby Lee that has good yield potential should be protected from early and late stripe or leaf rust, but a variety such as Duster may show some leaf rust early but still has good resistance to this rust.  However, stripe rust on Duster may merit control.  ALSO, in no-till fields watch for incidence of diseases such as tan spot, septoria, and powdery mildew as these diseases likely will be more common in fields with wheat residue and may merit an early season fungicide application.

Reports/excerpts of reports from other states:

Texas  Dr. Ron French (Ast Prof & Extn Plant Pathologist, Texas A&M AgriLife Extension Service, Amarillo) 9-Mar-2015:  “Last week, I was visiting the lower Coastal Bend of Texas (around Kingsville/Corpus Christi) and the Lower Rio Grande Valley of Texas (along the southernmost part of the Texas-Mexico border area). In Weslaco (Hidalgo County, Lower Rio Grande Valley), I visited sentinel plots (21 lines-winter wheat, spring wheat, barley…).”

“In Weslaco (March 4), Puccinia graminis f. sp. tritici, the causal agent of stem rust, was found on leaf tissue only, at trace levels to 1% severity in six 6 lines including  Morocco,  Marvelous, Kyto (CI 8250) and Line B (1% severity). Last year, stem rust was first observed on Siouxland, Panola, and  Morocco but observations were done the week of April 7, 2014.”

“Stripe rust (March 3)on wheat was observed  in 5 lines, ranging from  trace levels in Siouxland  to 25% incidence and 40% severity on Sisson.  Leaf rust was only observed at trace levels in lines such as Siouxland, Panola, and Sisson.  Powdery mildew was only present in the lower canopy of barley  Hypana, Morex DPH, and Hyproly.  Some wheat was already in the boot stage (Morocco, Line B).”

“Last year, dry conditions (little or no rain) were present in this area when stem rust was first observed. This year has seen more rain during the past three weeks, with temperatures ranging from as low as 38° F to as high as 84°F (lower on average for that area). With rain and warmer weather expected this week, disease pressure may be more conducive to seeing more disease development for all rusts.”

“No stem rust was observed in wheat in  the lower coastal bend around Kingsville, approximately 110 miles north of Weslaco. Fields did have stripe rust (up to 20% severity) but had already been sprayed with a fungicide and trace levels of leaf rust could also be observed.”

Kansas  Dr. Erick De Wolf (Prof & Small Grains Extn Pathologist, Kansas State Univ) 11-Mar-2015:  “We did some scouting for rust diseases near Manhattan (Northeastern KS).  We were checking on research plots where rust had been noted last fall but were unable to detect leaf rust in these plots so far this spring.  We noted severe tip die-back of the leaf tissue in these plots and suspect that this winter injury has removed much of the leaf rust from this location. Bethany Grabow, Ph.D candidate with KSU detected a trace of leaf rust on wheat in an adjacent field.  Incidence of disease was <0.01% with only a few pustules detected. This wheat was planted later than the aforementioned plots and did not experience the winter injury to the leaf tissue.  We also noted small colonies of aphids in the research plots with each colony having 3-5 aphids a few winged aphids were also observed near the colonies. We will continue to monitor the diseases this spring and provide more updates soon.”

Wheat leaf rust

Wheat leaf rust

Wheat stripe rust

Wheat stripe rust

Wheat disease update – 27 February 2015

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

Oklahoma:  As indicated in the Texas reports below, both leaf rust and stripe rust are present across Texas with stripe rust appearing to be the most prevalent and severe.  This also seems to be the case in Oklahoma – at least across central to southern Oklahoma.  John Fenderson (Monsanto) indicated yesterday that on a recent trip he took across central to southern Oklahoma he saw “clean” wheat around Chickasha but along highway 70 going west to Frederick he saw lots of stripe rust and some leaf rust.  In a few places he saw the ground colored orange from stripe rust spores indicating a stripe rust “hot spot.”  In fields such as this (especially if there are many hot spots), application of a fungicide to control the stripe rust should be considered.  In addition to helping to control the stripe rust, there could be the benefit of also limiting leaf rust, powdery mildew and possibly tan spot/septoria.

Around Stillwater, I have not seen much change since two weeks ago.  I have not confirmed any stripe rust, but have seen leaf rust.  However, we have been mostly quite cold with only slight moisture but stripe rust may also be starting.  I will wait until it warms up a bit before I look again.

Wheat leaf rust

Wheat leaf rust

Wheat stripe rust

Wheat stripe rust

Reports/excerpts of reports from other states:


Dr. Amir Ibrahim (Prof, Small Grains Breeding and Genetics, Texas A&M AgriLife Research) 26-Feb-2015:  The wheat crop in South Texas is at now at Feekes stages 5-6 [start of node elongation/first node detectable at base of tiller] depending on the line.   Leaf Rust (P. triticina) is spreading in our trials at College station (Brazos County) and both ‘Baldwin’ catch plot and ‘TAM 110’ are 100S.  As for stripe rust (P. striiformis), the ‘Sisson’ catch plot is 70S whereas the ‘Patton’ border is 100S.  It is noteworthy that we reported stripe rust on Patton near Ennis (Ellis County) on January 29, 2015.

Leaf rust is easy to find, but severity is very low at Bushland (Potter County) in Texas High Plains and Chillicothe (Hardeman County) in Texas Rolling Plains.  Unconfirmed reports also indicated spread of stripe rust in Brady (McCulloch County) in the heart of the state. Reports also indicated that ‘Redhawk’ was especially susceptible there and that some producers are already applying fungicides. Both leaf and stripe rusts are also present in Wharton County in South Texas.

If conditions continue to prevail, we can have significant leaf and stripe rust levels compared to last year, in my opinion.

Dr. Ron French (Ast Prof & Extn Plant Pathologist, Texas A&M AgriLife Extension Service, Amarillo) 25-Feb-2015:  Update on wheat rust in Texas- some commercial fields.  Leaf rust had been reported in Texas in fall 2014 as far north as Hansford County (Texas Panhandle, bordering the Oklahoma Panhandle) and throughout NW Texas, especially the Texas Panhandle. In early winter 2015, leaf rust was still found around the Amarillo area. This winter in Amarillo, we have had temperatures as low as 3°F  and will still be as low as 12°F and not much higher than the mid- 50s F for the next week, including snow.  In some cases when temperatures have dropped this much, some fields with trace levels of leaf rust no longer exhibited leaf rust for a while, whether that meant inoculum did not survive, was not active, or had new inoculum come in to that field. I visited some random fields today in the Amarillo area and was not able to find any leaf rust. This does not mean that leaf rust is not present but that it may be present at really low trace levels.

Last Wednesday, February 18, I did find leaf rust in one wheat field in Wichita County at trace levels in very few plants and only in the lowest two leaves. The biggest wheat in that field was at Feekes 4. Wichita County is in the Texas Rolling Plains and borders Clay, Wilbarger, and Archer Counties in Texas, and Tillman and Cotton Counties in SW Oklahoma. With high temperatures expected not to be higher than 63°F and as low as 25°F for the next seven days, could disappear, as observed in previous years when leaf rust was first observed in mid-to-late March.

Unlike 2014, no leaf rust has been observed so far in the lower Coastal Bend of Texas around Kingsville and Corpus Christi by this time. Some days have been cooler than normal and they have had more rain than in some previous years.

Stripe rust has been present as far west as Tom Green County in west Central Texas, where the city of San Angelo is located. Stripe rust was first observed at the very end of January and beginning of February. Stripe rust levels were significant in lower leaves only and the ground was covered in orange spores. A few fields that were sprayed with Tilt on February 16th had taken advantage of the fact that topdressing of nitrogen was being done on the wheat. Within a week, fields looked great and new growth looks “excellent” (probably a combination of topdressing, moisture from overhead pivot irrigation, root growth, and the fungicide application). At time of spraying, the wheat was fully tillered. Some varieties with some level of stripe rust include TAM 113, Coronado, Greer, Redhawk, Cedar, and TAM 304.

The farthest north I have seen stripe rust is in Wichita County at low trace levels, on February 18th.  The biggest wheat in that field was at Feekes 4. Although normally dry, this area may be getting some snow and rain in the next week or so, so there could be an increase in inoculum. But since temperatures are expected to range from 25° to 41°F on the low side, and between 32-63°F on the high side for the next seven days, this may not be conducive to stripe rust increase or establishment. Time will tell. Other fields in that area have not had stripe rust so far from what I gathered today.

Other locations with stripe rust include fields around De Leon, in Comanche County, located in Central Texas. The application Tilt in February is not uncommon in some locations in southern Texas as powdery mildew can be an issue. This year, applications of Tilt have occurred due to stripe rust concerns and in many cases, taking advantage of top dressing of nitrogen on wheat.

Wheat disease update – 11 February 2015

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

Oklahoma: Reports of diseases in Oklahoma have been sparse (as expected for this time of year) but certainly more numerous than last year when drought curtailed foliar diseases.  Yesterday (10-Feb) I found wheat leaf rust at a low, but consistent level in guard strips of Jagalene planted around a large wheat breeder nursery here in Stillwater.  Susceptible-type pustules were on lower leaves at 15-25%.  As temperature increases and with moisture this rust will increase and spread.

Gary Strickland (Extension Educator – southwest Oklahoma) indicated to me that he had heard reports of some leaf rust in Tillman County and also has seen a few pustules here and there on wheat in Jackson County, but nothing severe.  He has seen no powdery mildew and no root rots to speak of.  He also indicated there were a lot of acres of “little wheat” with some looking good if moisture had been received but that the southwest OK was quickly drying out.

Symptoms of wheat soilborne mosaic/wheat spindle streak mosaic (SB/SS) have shown up in Dr. Edward’s variety demonstration as well as in my SB/SS evaluation nursery, but symptoms are not yet striking as the flush of spring growth has not yet started.

Wheat soilborne mosaic virus can cause yellowing in the spring in susceptible varieties such as the one on the left.

Wheat soilborne mosaic virus can cause yellowing in the spring in susceptible varieties such as the one on the left.


Reports/excerpts of reports from other states:

Louisiana; Dr. Stephen Harrison (Professor; Wheat & Oat Breeder, LSU AGCenter) 3-Feb-2015:  “Stripe rust has been reported in several commercial fields and nurseries around central and northeast Louisiana.”


Texas Dr. Amir Ibrahim (Prof, Small Grains Breeding and Genetics, Texas A&M AgriLife Research) 3-Feb-2015:  “Wheat stripe rust found in Texas Blacklands area:  On January 29th, Russell Sutton, Assistant Research Scientist with the Small Grains program at Texas A&M University and our anchor in the northern Blacklands area and northeast Texas, visited our research plots near Ennis Texas. Russell found a small hot spot of stripe rust on the susceptible variety ‘Patton’ that we use as a spreader. The spot was about three feet in diameter and the lower leaves where heavily infected. The wheat appears to have completed the tillering stage and ready to begin jointing.  Russell will return in two weeks and collect some spores and look for more infection sites.

Wheat disease update – 31 October 2014

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

Oklahoma:  We’ve not seen any diseases so far this fall around Stillwater, but we have been relatively dry and much of the wheat was not planted until the past couple of weeks.  Mark Gregory (Area Extn Agron Spclt – southwestern OK) indicated to me earlier this week that he has not seen or heard any reports of leaf rust or other diseases.  However, Bryan Vincent (Crop Scout – NW/NC Oklahoma) sent me some photos of leaf rust pustules he found in several fields around the Aline-Helena area (30-40 miles northwest of Enid in north-central OK).  The pustules were extremely sparse and found only in very early planted wheat.  Bryan also reported seeing some light tan spot infections.  Leaf rust also has been observed in Kansas, Colorado, and Nebraska (see reports below), and stripe rust has been reported in Wyoming, Montana and the PNW.

Fall infestations of leaf rust rarely carryover to the spring and generally do not warrant treatment. Monitor fields and consider a split fungicide application in the spring if heavy foliar disease is still present at Feekes GS 6 - 7

Fall infestations of leaf rust generally do not warrant treatment. Monitor fields and consider a split fungicide application in the spring if heavy foliar disease is still present at Feekes GS 6 – 7 in early March

When leaf rust occurs in the fall in Oklahoma, the question arises regarding the value of spraying to control that rust.  Fall-infected leaf rust plants typically have yellowed lower/older leaves with rust pustules, but the youngest 2 or 3 leaves are green and healthy.  As temperature drops through November and December, the older rust-infected leaves die and new infections are greatly slowed and inhibited.  Grazing also helps to remove these leaves and increase air circulation and drying that are conditions less favorable to spread of the disease.  Given these considerations, spraying to control leaf rust in the fall is of limited value.  The primary concern with fall infections of leaf rust is that with a mild winter and sufficient moisture, the rust will survive through the winter and inoculum will be present in fields to start the disease early in the spring.  Hence, monitoring of these fields through the winter and early next spring is recommended to determine if a split application of a fungicide is merited to control the rust (and also possibly tan spot, septoria, and/or powdery mildew) in the early spring.

Reports/excerpts of reports from other states:

Kansas (Dr. Erick De Wolf, Extn Plant Pathologist, Kansas State University) 27-Oct-2014:  Wheat Leaf Rust Update in Kansas:  Planting of the winter wheat crop in Kansas is well underway. Farmers are reporting that wheat has emerged and is looking good in many areas of the state. Wheat planting on some farms was delayed by a late soybean harvest this fall, but these acres should be planted soon.

I was checking wheat this week in Manhattan (Northeast KS) and found leaf rust in some research plots.  This wheat was sown about 2-weeks prior to the optimal planting date but well within the normal planting range for wheat production in the state.  The leaf rust was not difficult to find with disease incidence near 5% some plots. The severity was 2 percent or less on most of the infected leaves. This level of fall infection of leaf rust is common in Kansas; however, 60% of the time cold temperatures and leaf desiccation during the winter months will eliminate the disease in many fields.

Ned Tisserat, retired plant pathologist from Colorado State University, also reported leaf rust in Northeast Colorado this past week. So it is possible that leaf rust is active in other areas of Kansas as well.  I will be checking other locations for leaf rust in Kansas this coming week and let the group now what I find.

Nebraska (Dr. Stephen Wegulo, Extn Plant Pathologist, Univ of Nebraska) 27-Oct-2014:  On Friday last week, Oct 24, I answered a call from a crop consultant who told me there is leaf rust in several wheat fields in the Panhandle of Nebraska.

Wheat disease update – 03 May 2014

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.

Wheat disease update – 26 April 2014

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

Oklahoma:  Wheat around Stillwater is mostly at GS 10.2 to 10.4 (heads ¼ to ½ emerged from boot).  Conditions are still dry, not only around Stillwater, but also around much (if not all) of the state.  Some rain fell this past week in the 1 inch range in a few areas, but in southwestern OK it was most likely too late to help the wheat.  Freeze damage also is becoming much more apparent.

Dr. Jeff Edwards (OkSU Small Grains Exten Spec) and I looked at wheat and attended a field day yesterday evening near Apache, OK (about 75 miles southwest of Oklahoma City).  The variety trial and field at Apache was lost because of freeze.  Wheat at Dr. Edward’s trial at Chickasha (30 miles northeast of Apache) also had some freeze damage but not as severe as the wheat around Apache.  No foliar diseases were seen at any field at which we stopped, and no reports of foliar diseases have come to me since my last update (10-Apr).  As you can tell from the reports below from Texas, there just is not much inoculum south of us to be carried northward, and what does blow up is likely not finding an environment conducive to infecting.

Our diagnostic lab has received few samples.  Of two recent samples from Garfield County (north-central OK), one was positive for Wheat streak mosaic virus (WSMV) and the other was positive for WSMV and High plains virus.  The diseases caused by these viruses, which are transmitted by the wheat curl mite, were fairly widespread in Oklahoma in 2013 and probably will be again in 2014.  However, I suspect that the drought and freeze will mask these infections.

Reports/excerpts of reports from other states:

Texas  Dr. Ron French (Ast Prof, Extn Plant Pathologist, Texas A&M AgriLife Extn Service) 25-Apr-2014:  Was driving all day and night (600 miles) yesterday looking at crops from Castroville to the Lower Rio Grande Valley and back. Today heading back to Amarillo.  Last Tuesday April 15 I drove from Amarillo to Wichita Falls (Northern Central part of the state right along the Oklahoma border) and back to  Amarillo (220 miles NW of Wichita Falls). Looked at commercial wheat and some trial plots in Chillicothe.

Did not see any rust at all and brought samples back just to make sure.  In the Wichita Falls area, wheat was at Feekes 10.4 (3/4 fully headed) on average. So now they should be at least flowering. In the Chillicothe area (65 miles NW of Wichita Falls towards Amarillo) wheat was on average at Feekes 10.3 (heading half complete).  Have not heard of any rust in this area (Rolling Plains and Panhandle) this week.

I have not received any feedback of stripe rust moving north of Ellis County (from my April 10 report), although now it is also in Hill County, adjacent to Ellis, but in a SW direction. In Hill County, wheat with stripe rust was past pollination and into grain fill.  Even in Bell county (Temple area, 120 miles south/southeast of Dallas) there was trace levels of stripe rust and none in the flag leaf.  Except for the Texas Panhandle, all other areas will soon (early next week for the Vernon area) be out of the window for spraying any fungicides.

So the good news is that rust is not moving north, yet. With warm temperatures during the day but cool at night, this might be affecting continuous fungal growth for both stripe and leaf rust fungi.

Texas (from a report issued by Dr. Erick DeWolf at KSU 25-Apr-2014:  Texas has reported some stripe rust activity just south of Dallas but warm temperatures have slowed the progress of that disease. Bob Bowden, USDA Plant Pathologist, reports that leaf rust remains active in research plots near San Antonio, Texas. However, the disease remains at low levels in commercial fields according to Tom Isakeit, Extension Plant Pathologist for Texas A&M. Wheat fields in southern Texas are nearly ready for harvest.

Kansas  Dr. Erick DeWolf, Extension Wheat Pathologist, Kansas State University 24-Apr-2014:  The risk of severe leaf diseases remains low throughout Kansas. My own scouting and reports from K-State agronomists indicate that leaf rust and stripe rust are not present in the state. Tan spot, septoria leaf blotch, and powdery mildew were absent in most fields; however, we did find a small number of fields with low levels of tan spot in Saline, McPherson, and Sedgwick counties. These fields all had wheat residue from previous crops on the soil surface. This residue is important because it often harbors the fungus that causes tan spot.

Drought stress was evident in most fields and the dry conditions are holding disease in check for now. Recent rains have brought some temporary relief to the dry conditions in a few areas of the state. We will continue monitoring the disease situation as this moisture may stimulate some disease. The symptoms of any new infections would not become evident for 7-10 days.  The current risk of severe disease in Kansas and the need for foliar fungicides is low.

Wheat disease update – 10 April 2014

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

Oklahoma:  Wheat around Stillwater is mostly at GS 7 (2 nodes detectable).  In a few places the flag leaf has emerged but only in one field.  I still have not received reports of significant foliar diseases in Oklahoma, which is not surprising given the dry conditions.  Around Stillwater I have seen some powdery mildew on low foliage in scattered spots.  I and my technician Brian Olson also found tan spot in a no-till field, but only on low foliage and not severe.  The one find of a different disease that is concerning was wheat streak mosaic (WSM) in Dr. Jeff Edward’s variety trial in Kay County near Kildare.  Visiting the trial on April 2nd, yellowing and streaking were present in all varieties but some were much worse than others.  I was not thinking about WSM at the time, but 5 samples I brought back to the lab all tested positive for the virus that causes WSM, so I believe that is what is present.  On a trip today to northern Oklahoma and over to Lahoma in north central Oklahoma, I saw some good and some bad wheat that ranged from GS 6 to GS 7 (or close to it).  However, all the wheat seemed short to me – some not much more than 10-12 inches tall.

Powdery mildew

Powdery mildew

In northwestern Oklahoma, Rick Kochenower (Area Res & Extn Agron Spclt) indicated, “I see a lot of dryland wheat dying but not from disease.”  He said that wheat was just starting to tiller.  In southern/central/southwestern Oklahoma, Mark Gregory (Area Extn Agron Spclt) reported that today he was in wheat towards the eastern side of the district and saw no diseases; also that the wheat furthest along had flag leaves fully extended (GS 9).  Gary Strickland (Extn Educator, Jackson County – southwestern OK) indicated wheat in his area was in the flag leaf stage – anywhere from flag leaf just emerging to fully-emerged.  Drought is the problem; no rust, powdery mildew or other diseases, but brown wheat mites have exploded.

Reports/excerpts of reports from other states:

Texas (southern) Dr. Amir Ibrahim (Prof, Small Grains Breeding & Genetics, Texas A&M Univ) 09-Apr-2014:

Wheat rust conditions at Castroville, TX – Wheat looks very good here and most of it is at the ripening stage. We have been applying a ½ of irrigation per week for the past two weeks. We may put another ½ next week, depending on the conditions. The morning fog at this location is also keeping the rust going.

Wheat stripe rust (P. striiformis)- This week provided an opportunity for taking notes on infection type and severity of wheat stripe rust (P. striiformis). Evidence points to a milder repeat of 2012 virulence that attacked ‘TAM 111’, ‘Garrison’ and other HRW. There is no indication of Yr17 vulnerability, which seemed as a one‐time incident that took place in 2010. Stripe rust is up to 70S on susceptible ‘Patton’.  We don’t expect infection types to be distinguishable next week but ratings for green leaf area duration can be taken. A lot of guessing has to be made, though, as both P. striiformis and P. triticina have been competing for the upper leaf surfaces. The former has started to dry up and newer infections are not likely. This does not overrule establishment farther north of here where conditions are conducive.  ‘Armour’ received a 40 S rating at this site, but ‘Redhawk’ looks very vulnerable with a rating 50S on the flag leaf and homogenous spread across the plot.

Wheat leaf rust (P. triticina): While stripe rust infections are fading, leaf rust (P. triticina) is now moving into the flag leaves of susceptible wheat. I have rated TAM 112 as 15S (FL) today. We have good diversity of races, but the Lr24 virulence is moving faster as evidenced by the rating of 60S on the flag leaves of ‘Jagalene’ as opposed to Lr17Lr39, and Lr41. We plan to come back here on April 21st to take notes on leaf rust, tag plants, and make selections.

Texas  Dr. Ron French (Ast Prof, Extn Plant Pathologist, Texas A&M AgriLife Extn Service) 10-Apr-2014:  I have spent many of the last 14 days traveling the Northern Central part of the state, from Wichita Falls (right along the Oklahoma border) and towards Amarillo (220 miles NW of Wichita Falls), and From Amarillo down to the Plainview area (70 miles south) and the Lubbock area (120 miles south of Amarillo). I have not seen any rust at all in commercial fields. Visual observation but also sampled just in case rusts were latent and not quite rupturing the epidermal tissue. No reports of there being any rusts from consultants as well.

From what I have gathered from consultants, there is/has been stripe rust as far north as Waxahachie, TX (Ellis County), 30 miles south of Dallas. Other locations with stripe rust are around Elgin, TX (Bastrop and Travis Counties, approximately 25 miles East of Austin, TX) and Taylor, TX (Williamson Co, approximately 25 miles south of Austin and approximately 75 miles West of College Station).

As far as leaf rust is concerned, these and other locations in that area have also had leaf rust, and in varieties such as Greer, Cedar, and Coronado.  Low levels but enough to warrant sprays as much of that crop is fully headed. In some locations, 7-10 before getting into the milk stage for Cedar.  I have also been told that Fannin had low levels of rust, something out of the usual.  I need to confirm which rust it is (leaf or stripe).

We are a bit behind other years where we have seen leaf rust by late March/early April as far north as Wichita Falls (a few miles from the Oklahoma border) and early April for stripe rust, North and Northeast of Dallas and close to the Oklahoma border.

With temperatures expected to be in the high 80s and low 90s Fahrenheit in the Texas High Plains sometime this weekend but lower next week but with little to no rain, disease pressure is still not there (humidity-wise) although common heavy winds could bring inoculum our way.

Texas (northern – blacklands area north of Dallas)  Jim Swart (IPM, Texas A&M AgriLife Extension 31-Mar-2014:  Wheat is rapidly recovering from the hard freeze we received in early March.  Winterkill does not appear to be an issue in any of the commercial varieties planted across the region, but some early maturing varieties in our research plots were damaged by the freeze.  Wheat planted in October is jointed (Feekes 6), and some plants are in Feekes 7 (two nodes above the ground).  Wheat planted in November is just beginning to joint.  We have identified a few bird cherry oat aphid infestations in central and southern Hunt County, but most of the area wheat crop has very low numbers of aphids (greenbug and bird cherry oat aphids).  We have not observed any stripe or leaf rust yet.

Louisiana Trey Price (Field Crops Pathologist LSU Ag Ctr, Winnsboro, LS) 31-Mar-2014:  There’s really not much to report at the moment in Louisiana.  Steve spotted leaf rust at Ben Hur Research Station in Baton Rouge a couple of weeks ago, and incidence and severity were low.  I’m unsure of the current status.  We have stripe rust developing in GACT7, a susceptible variety, at the Dean Lee Research Station in Alexandria.  Incidence and severity were less than 1% last week.  In Winnsboro, there are no rust issues on wheat or oats at the moment.  Low incidence and severity of leaf and stripe rust at Crowley (Rice Station, Southwest Louisiana).

Georgia  Dan Bland (Crop & Soil Dept, Univ of Georgia-Griffin) 3-Apr-2014:  We were down visiting our nursery in Plains, GA yesterday and found a lot of leaf rust in a strip of wheat planted about 2 months earlier than the recommended date for the purpose of spreading hessian fly to a small replicated test.  This is done every year so that David Buntin can get pupa and larva counts on the state variety test.  We normally see leaf rust in this area especially if the strip planted is susceptible.  This year Jerry Johnson says it’s the most he’s ever seen for this time of year.  We also saw leaf rust on the lower leaves of the most susceptible lines in another test about 300 yards away.  Leaf rust also has been reported in southeast Georgia.  Plains is in southwest Georgia.

Oregon  Dr. Michael Flowers (Extension Cereal Specialist, Oregon State University, Corvallis, OR) 3-Apr-2014:  After I sent out the note yesterday, reports have been coming in from both the north and south Willamette valley about stripe rust.  Currently there are reports of stripe rust found on Goetze, Kaseberg, Sy Ovation and Tubbs 06.  It appears that maybe we were not as lucky as hoped and that stripe rust did overwinter in some fields throughout (north and south) Willamette Valley

Wheat disease update – 31 March 2014

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

Oklahoma: No reports of significant diseases in Oklahoma. Around Stillwater, wheat soilborne/spindle streak mosaic are still showing strong in my screening nursery, but these virus diseases should not be much of a problem around the state due to resistance in nearly all planted varieties. Looking in the same places as 10 days ago, I did find a slight increase in the number of powdery mildew pustules on low leaves, but these pustules still are small and did not appear to be actively sporulating. Wheat is mostly at the Feekes stage 6 but likely approaching stage 7.

Reports/excerpts of reports from other states:
Many thanks to Dr. Amir Inbrahim for sending the report below as this is the most comprehensive disease report I have heard to date from Texas. I interpret his observations to indicate that both stripe and leaf rust are present (especially leaf rust), but that build-up has not yet hit the upper canopy but in this area producers should be ready to “pull the trigger” to protect wheat with high yield potential. In Oklahoma we will need to wait and see if moisture comes to allow inoculum coming from southern Texas to infect the Oklahoma wheat crop.

Texas Dr. Amir Ibrahim (Prof, Small Grains Breeding and Genetics, Texas A&M University) 30-Mar-2014: I have received reports from our research associates, around March 26, 2014, about the rust situation in South Texas.
Castroville, TX: The wheat crop is now at Feekes growth stages 8-10.5. Cultivars such as ‘Everest’ and ‘Billings’ have already headed at this site. There is a uniform spread of leaf rust (P. triticina) in the lower canopy of the spreader rows throughout the field. The infection has not yet moved up into the middle canopy or the flag leaves. It has been raining during the week of March 24th, and the weather forecast calls for temperatures in the high 80’s for the next few days, which will help promote the spread of the infection. Stripe rust (P. striiformis) has spread throughout the replicated trials, especially on the spreader rows of ‘Patton’. The infection was as high as 60S on the flag leaves of some experimental lines. There is uniform spread on TAM 111 in the range of 20-30S, which points to the presence of 2012 virulence. Temperatures have been cooler than normal which helped the spread of P. striiformis at this site. However, the warming temperatures will slow spread at this site but not necessarily at sites farther north if infection has already started.

Wharton, TX: The Wharton uniform rust nursery is located 90 miles south of College Station. The wheat crop is now at Feekes growth stages 8-10.5. ‘Everest’ has already headed at this site.
There is a uniform spread of leaf rust in the lower canopy of the spreader rows throughout the field. The infection is beginning to move into the mid canopy, and we believe mid-April should be a good target date for taking readings at this site.

Beeville, TX: Beeville is located 50 miles NW of Corpus Christi. We have both spring and winter wheat plots and head-rows at this site. The majority of the winter wheat here is at Feekes 5-7 growth stages, whereas the spring wheat is at 9-10. There is a buildup of leaf rust on TAM 112 in the head-rows and on the spreader rows around the yield trial plots.

College Station, TX: The wheat at this site is at Feekes 7-9 growth stages. There is a buildup of leaf rust in the lower canopy of ‘TAM 110’.

Wheat disease update – 21 March 2014

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

Oklahoma:  Diseases are still quiet across Oklahoma.  Gary Strickland (Extension Educator – southwest Oklahoma) indicated he has “seen one leaf rut pustule.”  Also, wheat just has not grown in his area and is just starting to get to the point of tillering but there is so little growth he doesn’t feel there is sufficient growth to support much tillering.  He did indicate he has seen and has a lot of reports of brown wheat mites.

Around Stillwater, the wheat soilborne/spindle streak mosaic is the only disease of prominence.  I did find some small pustules of powdery mildew in the extreme low leaves of ‘Pete’ wheat that was in the range of Feekes 6.  Wheat around Stillwater is in much better condition than in western Oklahoma where drought has been severe.  I also have seen quite a few lady beetles in my trials and plots, but have yet to see any aphids.

Reports/excerpts of reports from other states:

Arkansas  Dr. Gene Milus (Professor/Wheat Pathologist, Univ of Arkansas) 20-Mar-2014:  Jason Kelley, Extension wheat agronomist, found fresh leaf rust pustules on volunteer wheat at the Cotton Branch Experiment Station near Marianna on March 20.

Louisiana Dr. Stephen Harrison (Professor/Wheat Breeder, LSU AgCenter) 18-Mar-2014:  I found leaf rust at the Ben Hur Research Farm in Baton Rouge yesterday.  This was in an early-planted field for Hessian Fly where I found a few pustules around Christmas.  The cold and very wet winter put the rust on hold until recently but it is active and should ‘take off’ now.  I have not received any other rust reports from around the state but will check nurseries in north Louisiana tomorrow.

The wheat crop is a little later than normal and has a much tighter range of heading dates due to the cold winter.  The variety trial probably averages second node but is very rapidly developing.