About Me

Amanda De Oliveira Silva

Amanda De Oliveira Silva

I have served as an Assistant Professor and Small Grains Extension Specialist at Oklahoma State University since August 2019. I believe that close interaction with producers is vital to understand their production strategies and to establish realistic research goals. My program focuses on developing science-based information to improve the agronomic and economic viability of small grains production in Oklahoma and in the Southern Great Plains.

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Oklahoma Wheat Harvest Completed for the Most Part with the State 99% Finished – Harvest Report June 29, 2020

Courtesy Oklahoma Wheat Commission

Wheat harvest is now complete in most regions of the state, with a few combines finishing up in parts of the Panhandle as well as Northern Oklahoma. This has been one of the fastest wheat harvest that we have seen in some time. The weather in all regions was favorable once machines started rolling in Southwest Oklahoma and allowed progress to move extremely fast from border to border. The Oklahoma Wheat Commission is calling wheat harvest 99% finished and this will be the final harvest report for the 2020 season. Test weight averages across the state have been extremely favorable in all regions, with most of the crop coming in at 61 lbs. to 64 lbs. per bushel.

Yields in Southwest and South Central Oklahoma varied with much of the wheat having low yields (ranging from the mid teens to high 20’s) due to excessive freeze damage that took place on April 15th. Yields were much better in central Oklahoma, with several reports in the mid 40’s to high 50’s. Yields in North Central and Northwest Oklahoma continue to range from the mid 40 to mid-60 bushels per acre depending on variety and location. In the Panhandle regions, irrigated wheat harvest continues. Yields on irrigated wheat in the central to the western regions of the Panhandle have not been as favorable as years past with a lot of irrigated wheat making 50 to 75 bushels per acre, with an occasional report of 100 bushels per acre or slightly higher. Test weights in the Panhandle continue steady at 60 lbs. to 62 lbs. per bushel. In some areas on the earlier harvested dryland wheat, test weights were a bit lower at 58 lbs. per bushel. Proteins across the state for this 2020 harvest have ranged from 8% to as high as 15.5%. The state average for protein is being reported between 11% to 11.2%.

This will be the last harvest report conducted by the Oklahoma Wheat Commission for the 2020 harvest season.

Oklahoma Wheat Harvest Moves Ahead but is Hindered by Rain in Most Regions Over the Weekend – Harvest Report June 22, 2020

Courtesy Oklahoma Wheat Commission

What is left of Oklahoma wheat harvest has been at a standstill in most places since Thursday night due to rain showers in the North Central and Northwest regions of Oklahoma. Rains have come thru off and on in all these areas the past 5 days, with the exceptions of Northeast Oklahoma in the Afton and Miami regions. Although they received light showers in parts of Northeast Oklahoma early this morning, producers were able to harvest in the Afton and Miami areas over the weekend.  Many of the acres in this region have gone into soybeans and other summer crops, so wheat harvest started and was finished over a period of 3 days. Combines were also slowed in all regions of the Panhandle over the weekend due to light rains on Friday night, but combines are back rolling in the Central Panhandle and Western Panhandle regions today.  Rains in the Eastern region of the Panhandle were heavier and producers will be at a standstill, although much of the wheat is already cut in this area.  Irrigated wheat in the central Panhandle around the Texhoma, Guymon and Hooker regions is ranging from the 60 bushels per acre to 90 bushels per acre depending on planting date, variety and location. Some higher yields have been reported with intensive management, but the severe drought and late freezes seem to have had an impact on both the dryland and irrigated crops. Dryland wheat harvest has finished in that area and with yields not too favorable making in the mid teens to mid 20’s. Proteins in the region from 11.9% to 14.9%.  Test weights on all wheat even with lower yields is still favorable ranging from 60 lbs. to 64 lbs. per bushel.  The Oklahoma Wheat Commission is calling Oklahoma Wheat Harvest 95% completed.

Panhandle

Texhoma/Guymon/Hooker – Much of the dryland wheat in this area has been utilized for other purposes due to the extreme drought conditions. Yields on irrigated wheat are reported at 60 bushels to 90 bushels per acre. Some higher yields over 100 have been reported on fields with intensive management practices.  Test weights are ranging from 61 lbs. to 66 lbs. per bushel. Proteins are ranging from 12% to 14.5%.  Harvest in this area is approximately 80% complete.

Boise CityHarvest is 60% complete.  Producers in this area were hindered from getting in the fields over the weekend due to rain, but combines are moving today.  For the most part, test weights on all wheat are favorable coming in at 60 lbs. to 63 lbs. per bushel. Protein is ranging from 11.0% to 14.9%. Yields on the dryland have been making in the mid teens to mid  20’s. Irrigated wheat is ranging from 50 bushels to 75 bushels per acre.

Northeast Oklahoma

Afton and Miami- Harvest is 99% complete.  Harvest started last Wednesday and producers in this region were able to get everything harvested over a 3 to 4 day period, before rains came into the region early Monday morning. Yields ranged from 20 to 40 bushels per acre and were much lower due to excessive moisture and late freezes.  Few wheat acres were harvested in this region due to producers putting a majority of acres into summer crops. Test weights were extremely favorable ranging from 61 lbs. to 62 lbs. per bushel even on the Soft Red Winter wheat that was harvested.  Soft Red Winter wheat test weights are usually much lighter but this year they managed to come in just as high as the Hard Red Winter wheat acres.  No proteins were reported. 

The next harvest report by the Oklahoma Wheat Commission will be published Wednesday, June 24, 2020.

Wheat Disease Update – 17 June 2020

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

I thought my 5-June update would be my last, but two samples/reports have come in that are prompting another update.  One of these reports was wheat kernels with darkened-colored germ ends with the dark discoloration moving toward the middle of the seed and into the crease.  This is indicative of black point (Figure 1; photo on the left), which is a discoloration of the seed (typically the germ end of the seed) resulting from either infection by a number of different fungi that typically are saprophytes (living on dead tissue) but can occasionally parasitize living tissue, or from a combination of abiotic (environmental) conditions that promote the discoloration without the presence of an organism.  Often black point occurs when freeze damage has occurred, or harvest was delayed and dead tissue in the heads has been heavily colonized by fungi that cause sooty mold (Figure 1; photo on the right).  Black point in wheat grain can be a grading factor as the discoloration can result in black flecks in flour milled from such grain.  Additionally, if used as seed wheat, kernels with black point can have reduce germination resulting in a lower seedling emergence.  Hence, if wheat showing black point is to be used as seed wheat, it is imperative to check the germination of that seed and to use a seed treatment that controls seed and seedling rots.

Figure 1. Wheat kernels with black point (photo on the left; note the pinkish color on the two outer wheat kernels, which is a seed treatment that had been applied), and sooty mold on a mature wheat head (photo on the right; photo credit – Dr. Erick DeWolf; Kansas State University)

 A second notable occurrence has been the report of wheat infested with common bunt/stinking smut.  This disease should not be confused with loose smut.  Loose smut is readily identified in the field as wheat is heading, and is characterized by heads with loose black spores (Figure 2; photo on the left).  There is a big difference between loose smut and common bunt/stinking smut.  Wind moves spores of the loose smut fungus to healthy wheat heads where they infect the developing seed at about the same time that flowering occurs.  Hence, the loose smut fungus is inside of that seed.  If the wheat is sold for flour there is no problem.  However, if that infected seed is used as seed wheat the next fall, then the loose smut fungus will grow within the seedling and plant that emerges from that infected seed.  Then at heading, instead of a normal head emerging a head filled with the black, loose smut spores emerges.  In contrast to loose smut, common bunt/stinking smut produces ‘bunt balls’ in wheat heads (Figure 2; middle photo and photo to the right), which break and spread spores onto healthy wheat kernels as well as into the soil in the field.  Hence, spores of the common bunt fungus survive on wheat kernels or in the soil and not inside of seed as is the case with loose smut.  In the fall when wheat germinates, the common bunt spores also germinate and infect the young seedling.  The fungus then grows with the plant, and as heading occurs and the wheat senesces, bunt balls are formed rather than wheat kernels.  Another difference between these two smuts is that no odor is associated with loose smut, whereas a strong musty/fishy odor is associated with common bunt, especially if there is a bad infestation.

Figure 2. Loose smut (left photo); common bunt/stinking smut bunt balls in a mature wheat head (middle photo; photo credit; Dr. Bill Bockus; Kansas State University); bunt balls of common bunt/stinking smut compared to healthy wheat kernels (right photo).

Recently I have received reports and a sample of wheat grain heavily infested with common bunt/stinking smut.  The wheat kernels appear to have blackened tips (Figure 3; top left and top right photos), but in contrast to black tip (Figure 1) where the germ end is darkened, in this case the brush end of the seed is darkened.  This blackening of the brush end is caused by thousands of common bunt/stinking smut spores being trapped in the brush (Figure 3; bottom photo).  I am bringing this to your attention because although both loose smut and common bunt/stinking smut can create significant problems, both are readily controlled by the use of an appropriate seed treatment.  Many such treatments are available.  Some are for insects, some are for bunts and smuts, some are for root rots, and many are for a combination of wheat insect pests and wheat diseases.  A good starting point as a guide for an appropriate seed treatment is the table on pages 262-263 in the 2020 OSU Extension Agents’ Handbook of Insect, Plant Disease, and Weed Control (OCES publication E-832) where many (but not all) of the more common seed treatments are listed.  It may not be necessary to plant treated wheat seed every year to manage loose smut and common bunt/stinking smut, but it is much better to manage them preventatively rather than wait until there is a severe outbreak of either one in a field.

Figure 3. Healthy wheat kernels covered with spores of the common bunt/stinking smut fungus (top two photos). Note the dark color at the top (brush end) of the kernels, which is due to the trapping of thousands of spores in the brush of the wheat kernel (bottom photo).

Oklahoma Wheat Harvest Moves Quickly Northward – Harvest report June 15, 2020

Courtesy Oklahoma Wheat Commission

Oklahoma wheat harvest continues to move forward with great progress being made in the Southwest, Central and Northern regions of the state.  Harvest is wrapped up in Southwest and South Central Oklahoma for the most part. Parts of North Central Oklahoma are also reporting to be 95 to 99% completed, with areas of Northern and Northwest Oklahoma 50% to 80% completed depending on location.  In Northeast Oklahoma at Afton and Miami, producers are just getting into the fields. In the Panhandle region, producers continue working on dryland harvest, with the hopes they will start with irrigated wheat towards the middle or the end of the week. Test weights across the state are being reported as extremely positive with averages for all regions ranging from 61 lbs. to 64 lbs. per bushel. Yields in Southwest Oklahoma varied all over the board from 15 bushels to 30 bushels per acre with a few higher yields noted.  In parts of South Central Oklahoma around Apache and Hinton, the yields have been reported to be better. In some areas around Apache, yields were reported in the mid 40’s to mid 50’s depending on variety and field location.  Yield trends have been higher in Central, Northern and most parts of Northwest Oklahoma.  A lot of wheat ranging from the mid 40’s to mid 50’s and several yields reported in the mid 60’s also have been reported.  In Northeast Oklahoma as harvest begins, no yields have been reported but it looks like the test weights are going to remain strong with yields lower due to severe freeze damage.  In the Panhandle region, decent yields are being reported on dryland wheat in the Eastern region of the Panhandle, with higher yields in the mid 40’s being reported around Buffalo. Dryland wheat in Texas county especially the southern and western portions of Texas County and in Cimarron county has had lower yields reported in the mid-teens to mid-20’s with some higher yields reported in the mid 30’s in the Northern and Eastern regions.  A lot of the dryland wheat will not be harvested due to insurance claims being made in those Southern and Western regions of the Texas and Cimarron counties in the Panhandle due to drought. Proteins across the state are ranging from 8.0% to as high as 15.5%.  It is to early for a statewide assessment, but indications are showing we might be looking at a number somewhere in the range of 10.5% to 11.2% for a statewide average.  The Oklahoma Wheat Commission is calling Oklahoma Wheat Harvest 62% completed.  This will be the last harvest report that will cover Southwest, South Central and Central Oklahoma regions since harvest has wrapped up in these areas.

Grandfield/Chattanooga-Harvest in this region is 99 percent complete.   Yield reports are ranging from 5 to 25 bushels per acre. In some parts of the Grandfield region, some of the later planted wheat is doing much better with some reporting yields in the mid 40’s, although that is still very rare.  Test weights have ranged from 58 lbs. to 62 lbs. per bushel, with the average running at 61 lbs. per bushel.  Even though much of the wheat has been put up for hay, some of the later planted wheat with higher yields are going to make the overall grain being hauled in better than what was previously predicted.  At the beginning of harvest, the Grandfield location was hoping to take in 1/3 of the wheat that would normally be harvested, but that number has now changed to 1/2.  Proteins ranging from 9% to 13%, with hopes of an 11.5% average. 

Altus/ Hobart/Lone Wolf/GoteboHarvest is 99% completed.  Yields are ranging anywhere from 15 to 40 bushels per acre, with more being towards the lower numbers. Some of the later planted wheat is doing better, with an occasional 50 bushels per acre. The test weight average is reported at 61 lbs. per bushel for this entire area. The protein average is currently at 11.5%.

ApacheHarvest is 95% completed. Test weights for the Apache location will average 62 lbs. to 63 lbs. per bushel. Yields in this area for the most part have been from the mid 40’s to the mid 50’s, with some lower yields on lower lying fields due to severe freeze damage.  No proteins were reported.

Sentinel/RockyHarvest has progressed and is 99% complete.  At both locations, yields are being reported in the low 20’s to mid 30’s. The severe drought, late freeze and heavy hail damage have really impacted what will be harvested. A lot of wheat has already been put up for hay. Test weights are ranging from 60 lbs. to 62 lbs. per bushel. No proteins were reported.

Okarche/Reeding/Kingfisher/OmegaThis region has progressed greatly over the weekend and is 98% harvested. Yields have been in the upper 30’s to mid 60’s. Test weights have been positive ranging from 62 lbs. to 66 lbs. per bushel.  Proteins are ranging from 9% to 12%, depending on variety and location.

Greenfield- Test weights on the wheat ranging from 63 lbs. to 66 lbs. per bushel. The lowest yield reported at this location was 36 bushels per acre. Several fields are making in the high 40’s to mid 60’s, depending on variety and planting date. Proteins have ranged from 9% to 13%.  This region is 99 percent completed.

Goltry/Helena- Harvest has progressed fast over the weekend. This region is estimated to be 65% to 70% completed with harvest.  Test weights have remained steady with the area reporting a 64 lbs. to 65 lbs. per bushel average.  Yields have been from the high 30’s to the mid 60’s, with many reports making in the mid 40’s to mid 50’s.  No proteins have been reported as of this date.

Kremlin/ Pond Creek/ Medford/ Blackwell- The south end of this region is reported 75% complete and the North end is reported to be 50% finished.  The yields for the most part are falling in the mid 40’s to mid 60’s. Test weights are averaging 64 lbs. per bushel for the region. Proteins are ranging from 9% to as high as 15%. 

Alva/ Buffalo– Harvest in Alva is 90% complete and in Buffalo is 50% finished. Test weights are exceptional, being reported in ranges of 63 lbs. to 67 lbs. per bushel.  Proteins are ranging from 9% to 11.5%.  Yields around Alva are being reported in the mid 40’s to mid 60’s.  In Buffalo yields are being reported in the mid 40’s, with some in the low 50’s.

Panhandle

Hooker– Harvest continues with the dryland wheat.  Yields on the dryland range anywhere from 15 to 25 bushels per acre and in some parts the occasional 30 is being reported. Irrigated wheat harvest will hopefully be ready by the end of the week. The irrigated wheat in the region does look favorable and producers are hopeful for decent irrigated yields. Test weights are ranging from 61 lbs. to 63 lbs. per bushel.  Proteins are ranging from 10% to 13%.

Northeast Oklahoma

Afton and Miami- Harvest is just getting started in this region as of today.  Early test weights have been favorable coming in at 61 lbs. to 63 lbs. per bushel.  No reports on yields have been made, but much of the wheat is expected to yield lower, due to severe freeze damage.   No protein was reported.

The next harvest report by the Oklahoma Wheat Commission will be published Wednesday, June 17, 2020.

Oklahoma Wheat Harvest Rolling from Border to Border

Courtesy Oklahoma Wheat Commission

Oklahoma wheat harvest continues to move forward with great progress being made in the Southwest and Central regions of the state. Parts of South Central Oklahoma have been moving slower due to the grain being ready but greener straw.  Producers have been getting a good start in other parts of North Central and Northwest Oklahoma, but in some areas around Helena and Goltry, farmers have been dealing with greener and tougher straw that is still not ready to cut, even though the grain is ready.   Producers have also had to contend with extremely high winds yesterday and today which was making it difficult for cutting, also with major concerns for fire.  In some places, elevators stopped taking grain because fire danger was too high, and local communities had concerns rural fire departments would not be able to keep up if large fires got started. We did see an increase on fires reported yesterday in all regions of the central and western parts of the state. Test weights continue to be phenomenal across the state with some areas in Northwest Oklahoma reporting averages at 64 lbs. to 65 lbs. per bushel.  Yields being reported in central and northern regions of the state are trending higher, with several reports of most fields at least making in the mid 40’s, with a large amount of reports of many fields making in the mid 50’s to mid 60’s, depending on variety, planting date and production practices.  Proteins across the state are ranging across the board from 8.5% to as high as 15.5%.  It is to early for a statewide assessment, but indications are showing we might be looking at a number somewhere in the range of 10.8% to 11.2% for a statewide average. 

Grandfield/Chattanooga-Harvest has been moving along at a fast pace.   Yield reports are ranging from 5 to 25 bushels per acre. In some parts of the Grandfield region, some of the later planted wheat is doing much better with some reporting yields in the mid 40’s, although that is still very rare.  Test weights have ranged from 58 lbs. to 62 lbs. per bushel, with the average running at 61 lbs. per bushel.  Even though much of the wheat has been put up for hay, some of the later planted wheat with higher yields are going to make the overall grain being hauled in better than what was previously predicted.  At the beginning of harvest the Grandfield location was hoping to take in 1/3 of the wheat that would normally be harvested, but that number has now changed to 1/2.  Proteins are reported to be all over the board ranging from 9% to 13%, with hopes of an 11.5% average.  This region is 92% completed with harvest.

Altus/Hobart/Lone Wolf/Gotebo– Harvest is 75% completed in this region.  Yields are ranging anywhere from 15 to 40 bushels per acre, with more being reported towards the lower numbers. Some of the later planted wheat is doing better, with some reports of an occasional 50 bushels per acre. The test weight average is reported at 61 lbs. per bushel for this entire area. The protein average is reported currently at 11.5%.

Sentinel/RockyHarvest has really progressed over the weekend with 80% of the area completed. At both locations, yields are being reported in the low 20’s to mid 30’s. The severe drought, late freeze and heavy hail damage have really impacted what will be harvested. A lot of wheat has already been put up for hay.  Test weights are ranging from 60 lbs. to 62 lbs. per bushel.  No proteins were reported.

Okarche/Piedmont/Kingfisher/HennesseyThis region has progressed greatly over the weekend and is 80% harvested. Yields have been reported in the upper 30’s to mid 60’s. Test weights have been positive with reports ranging from 62 lbs. to 66 lbs. per bushel.  Proteins are ranging from 9% to 12%, depending on variety and location.

Greenfield- Test weights on the wheat are reported to be ranging from 63 lbs. to 66 lbs. per bushel. The lowest yield reported at this location was 36 bushels per acre. Reports of several fields are making in the high 40’s to mid 60’s, depending on variety and planting date. One 40 acre patch was reported to have made 84 bushels per acre. Proteins have ranged from 9% to 13%.  This region is 65% to 70% completed with harvest.

Goltry/Helena- Some producers cut a couple of the heavier grazed fields earlier this week. Test weights on the earlier cuttings are ranging from 63 lbs. to 65lbs. per bushel with a couple 66 lbs. per bushel being reported.  One field was reported in the mid 40’s.  Producers have now been dealing with greener straw on the better wheat and it has been slowing them down from being able to get into the fields. Farmers were hopeful to get into the fields this afternoon with better chances of drier straw so things can get rolling. Much of the wheat currently looks favorable in this region with predictions of many fields making in the high 40’s to mid 60’s.  No proteins have been reported as of this date.

Kremlin/Pond Creek/Medford/Blackwell- The south end of this region has kicked off with harvest being in full swing.  Producers in the Northern areas are just getting a good start.  The yields being reported for the most part are falling in the mid 40’s to mid 60’s.  Test weights are averaging 62 lbs. to 63 lbs. per bushel. Proteins are ranging all over the board from 9% to as high as 15%, and it is too early for averages to be reported. Overall this region is 20% harvested.

Burlington- Producers have been cutting in Burlington over the weekend.  Test weights are ranging from 62 lbs. to 63 lbs. per bushel on average.  Some yields have been reported in the mid 50’s to mid 60’s. One small 80 acre patch was reported to have made 90 bushels per acre on dryland wheat.  Proteins are ranging from 9% to 13%.  This area is considered to be 15% harvested.

Alva/Buffalo– Harvest is just getting started around Alva with four or five producers cutting. Test weights are exceptional, being reported in ranges of 63 lbs. to 67 lbs. per bushel. Only one yield for the region has been reported coming in at 63 bushels per acre.  Proteins are ranging from 9% to 11.5%.  Harvest has not really begun in the Buffalo area, but they are hopeful grain will start being harvested in this area over the weekend.  While nothing has been reported in the Buffalo area, in the Eastern part of the Panhandle much of the wheat currently looks favorable.

Hooker– Harvest continues with the dryland wheat. Yields on the dryland are being reported anywhere from 15 to 25 bushels per acre. Irrigated wheat harvest will hopefully be ready sometime the beginning or middle of next week. The irrigated wheat in the region does look favorable and producers are hopeful for decent irrigated yields. Test weights are ranging from 61 lbs. to 63 lbs. per bushel.  Proteins are ranging all over the board from 10% to 13%.

The next harvest report by the Oklahoma Wheat Commission will be published Monday, June 15, 2020.

Wheat Disease Update – 4 June 2020

This article was written by Bob Hunger, Extension Wheat Pathologist

This likely is the last disease update from Oklahoma until preparation starts for planting in the late summer.  Harvest is definitely underway across central and southern/southwestern OK, and Josh Bushong (Area Extn Agron Spclst – northwestern and northeastern OK) indicated wheat is quickly turning across northern OK as well.  Dry conditions in northwestern OK and the OK panhandle have limited diseases in those parts of OK, and with wheat quickly turning, diseases should not be a factor from here on.  The one exception to this would be if head scab was occurring at a high incidence, but to date I have had only one report of just light scab in the northeastern part of Oklahoma.

One report of interest that has come is the occurrence of dark brownish/black to dark bronze-colored heads in mature wheat (Figure 1).  Although at a low incidence (Figure 1, left photo) these heads are noticeable and have been observed across multiple varieties by Gary Strickland (Extn Educator; Jackson Cnty; southwestern OK), Dr. Amanda de Oliveira Silva (Ast Professor & Small Grains Extension Agronomist) and Dr. Brett Carver (Regent’s Professor/OSU Wheat Geneticist & Breeder), and myself.  These heads, which typically are sterile or only have small and shriveled grain, seem to be most common in areas where freeze was most damaging, and likely are related to that environmental cause (i.e., freeze).

Figure 1.  Darkened heads at low incidence in mature wheat in a field in southwestern OK.  Cause likely is environmental; most likely related to freeze. [photo credit: Gary Strickland; Extn Educator; Jackson Cnty]

I also want to follow-up on the widespread occurrence of splotchy browning and spotting of wheat leaves that was observed across many varieties over Oklahoma this year.  I collected and plated numerous leaves from such plants, and the best I can determine is that much of this browning was caused by Septoria leaf blotch (and to a lesser extent, tan spot).  Freeze and drought also likely contributed in some cases.  Figure 2 shows my reasoning for this.  The first four photos are examples of the splotchy browning and spotting of leaves. Some leaves would be almost entirely brown/necrotic. Upon plating and incubating these leaves, I often would not find any pathogens after two days in alternating light dark, which is needed to induce sporulation of the tan spot fungus. However, if I kept these leaves for a longer time (6-10 days), I often would find a high incidence of pycnidia indicative of Septoria leaf blotch forming over the leaves (bottom photo in Figure 2). Oozing from these pycnidia contained spores of the fungus that causes Septoria leaf blotch.  Occasionally I also would find sporulation of the fungus that causes tan spot as well as the fungus that causes spot blotch.  Also mixed in and often overgrown were many secondary, non-pathogenic fungi that are taking the opportunity to grow on the dead leaf tissue.  As a result, I am attributing the widespread leaf browning observed this year to be primarily the result of Septoria leaf blotch.

Figure 2. Various “types” and “degrees” of leaf browning/yellowing/spotting observed on wheat across northern Oklahoma during mid to late May.

Wheat Disease Update – 22 May 2020

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

The disease situation in Oklahoma has not changed significantly since my last update on May 15th.  The weather in Oklahoma has remained atypically cool and mostly dry; however, off-and-on rain is forecast over much of the state starting tonight and into next week.  This will provide excellent conditions for continued grain filling, and typically would also provide conditions favorable for foliar diseases to increase.  However, over about the southern half of the state, much of the canopy has turned or is turning and no longer will be threatened from foliar diseases.  For example, Dr. Brett Carver (OSU Wheat Geneticist & Breeder) was in Tipton (southwestern OK) earlier this week and indicated most of the wheat he saw was within about 7-10 days of being ready to harvest.  Here around Stillwater, most of the canopy is turning, and the grain is mostly around late milk to early soft dough.  On wheat such as this, foliar diseases are no longer a concern, and wheat at this stage even with green foliage is way past the time to spray.  Josh Bushong (Area Extension Agronomy Specialist) indicated diseases overall are lacking in northwestern Oklahoma and the Oklahoma panhandle primarily because of dry conditions.

On Tuesday, 19-May, I took a trip to Kildare (north of Ponca City) over to Cherokee (northern OK) and to Lahoma (just west of Enid).  On the same day, Dr. Amanda de Oliveira Silva (Ast Professor & Small Grains Extension Agronomist) started in Alva (about 15 miles west of Cherokee) and then worked her way east to Cherokee and Lamont (north-central OK about 15 miles west of I-35 at the Tonkawa exit, highway 11).  Wheat in a field near Alva and in the variety trials near Cherokee, Lamont, and Kildare were in the late milk to soft dough stage.  In a field near Alva, Dr. de Silva saw very little rust (leaf or stripe) or other foliar diseases (too dry).  At the variety trial near Cherokee, rust (both leaf and stripe) as well as powdery mildew were present but sparse.  In the variety trial near Lamont, Dr. DeSilva did observe moderately severe leaf rust but the leaves, although still having some green area, are turning/dying quickly.  The most common symptoms seen at all these variety trials was the leaf browning/spotting (Figure 1) that I’ve talked about in the last couple of updates.  This browning/yellowing/leaf spotting is curious, because there appears to be diseases involved as well as environmental/weather factors such freeze and perhaps drought and wind.  For example, in the photo on the right in figure one, you can see dead areas consistent with Septoria leaf blotch as indicated by the irregular, small blotchy areas in which pycnidia (small black spots) of the Septoria fungus can be observed.  Many of the other spots appear to be consistent with tan spot symptoms, but the tan spot fungus has been only occasionally isolated from such leaves.  I am continuing to isolate from leaves such as those in Figure 1 to try to ascertain the cause, but remain puzzled at the cause.

Figure 1. Various “types” and “degrees” of leaf browning/yellowing/spotting observed on wheat across northern Oklahoma during the week of May 18th. (right photo credit; Dr. Brett Carver; OkSU).

So in summary, the time for active foliar diseases in Oklahoma is coming to an end as the crop is maturing and moving toward senescence.  It is possible that foliar diseases such as leaf rust could still appear in northwestern OK and the OK panhandle, but dry conditions have prevented that to this point in time, and the wheat crop in Oklahoma is moving steadily toward harvest.

Wheat Disease Update – 9 May 2020

This article was written by Bob Hunger, Extension Wheat Pathologist

This past week was quite cool across Oklahoma (mid 60s F in Stillwater today) and central Oklahoma received needed rain.  Unfortunately, western OK and the panhandle were not as fortunate and remain dry.  Wheat around Stillwater this week was as far along as the milk to soft dough stage; wheat today at Lahoma in north-central OK ranged considerably but was as far along as approaching full kernel but watery.

Stripe rust has fairly well shut down across the state as indicated by turning to the telial spore stage (see 27-April update at http://entoplp.okstate.edu/pddl/2020/PA%2019-15.pdf), and although this cool weather with rainfall and dew in central OK will favor stripe rust, I doubt if we will stay sufficiently cool and wet for stripe rust to pick up again across Oklahoma (plus, northwestern OK and the panhandle remain dry).  However, leaf rust has started to become more prevalent over this past week and likely will continue to increase in areas where there is rainfall or dew formation.  This past week around Stillwater, both Dr. Brett Carver and I were able to rate plots and trials around Stillwater for leaf rust incidence and severity.  Additionally this past week here at Stillwater for the first time in about a decade, I found wheat stem rust.  Recall there are three wheat rusts including stripe rust, leaf rust, and stem rust.  Stem rust is rare in Oklahoma and is only observed in years when we have an extended cool spring (much like this one).  Figure 1 shows photos comparing these three rusts on wheat leaves.  In contrast to the implication of its name, stem rust can occur on leaves as well as on stems, whereas pustules of stripe rust and leaf rust are more typically found on leaves.

Figure 1. The active spore stage (urediniospores) of the three wheat rusts, including stripe rust (left photo; credit to Dr. Guy Padgett, Louisiana State University), leaf rust (second photo from left), and stem rust (two photos on the right). Note the difference in color between stripe rust and the other two wheat rusts. Leaf rust and stem rust spores are similar in color, but stem rust pustules typically are more robust than leaf rust, often are found on leaves as well as stems, and seem to me to have a bit darker brick-red brown color than leaf rust.

Leaf browning also is still apparent around much of the state and has multiple causes this year as discussed in the 27-Apr Disease update (http://entoplp.okstate.edu/pddl/2020/PA%2019-15.pdf).  These causes include leaf spot diseases, freeze, drought, necrosis (tissue death) due to a resistant reaction to stripe rust, and even a browning due to an unknown physiological factor.  Over this past week, both Dr. Brett Carver and I have observed another possible cause of leaf browning, which is bacterial streak (Figure 2).  Bacterial streak isn’t usually a significant problem in Oklahoma, but occasionally has been observed in low to moderate incidence.  It causes not only a browning of leaves (but without the “pepper spots” as with Septoria/Stagonospora), but also can cause a darkening of the heads (black chaff).  As I said, we have not confirmed bacterial streak to be present, but it is a possibility.

Figure 2. Bacterial streak on wheat leaves (left phot; Dr. Jeff Edwards, Oklahoma State University), a wheat head and stem just under a wheat head (center photo), and causing black banding on wheat awns (right photo).

Finally, it is worth mentioning that a number of individuals have reported seeing a higher incidence of wheat heads with loose smut (Figure 3) this year.  This agrees with what Dr. Carver, Dr. Amanda de Oliveira Silva, and I have seen.  Spores of the loose smut fungus (Figure 3, right photo) are released in the field when wheat is flowering.  The spores infect the fertilized seed and are carried within the seed.  If this infected seed is used to plant the next year’s crop, the growing plant from that seed will be infected and produce loose smutted heads in the spring – hence, completing the disease cycle.  The ways to avoid problems from loose smut are to (1) not save seed wheat from fields in which loose smut is present, and (2) plant seed wheat treated with a fungicide labeled for use to manage loose smut.  Many such seed treatments are available.  I need to point out that if you have a field this year with loose smut and you plant treated wheat in this field next year, there may still be some loose smut-infected plants the next spring.  These infected plants would not be from the treated seed wheat, but are volunteer plants from the previously infected crop.  If you have questions about the bunts and smuts please contact your local county extension educator or me.

Figure 3. Loose smut of wheat. The center photo is to show that the smut fungus does not necessarily take over an entire head. The left photo is to show the powdery nature of the spores of the loose smut fungal pathogen.

Freeze damage update – 05/05/2020

Amanda de Oliveira Silva, Small Grains Extension Specialist

As time goes by the impact of the Mid-April freeze event becomes more evident across wheat fields in the West, Southwest, and Southcentral regions of Oklahoma. Other regions of the state were lightly or not affected by the freeze.

Wheat should be filling kernels by now, but all we are finding are sterile and “empty” heads (Figure 1). Wheat continue to be green and sometimes look healthy from the outside but is not producing any grain.

A significant freeze-damage on wheat at Roger Mills and Washita counties on the West part of the state may lead to a reduction in harvested acres this year.

 “The April freeze has significantly impacted most Southwest wheat acres. Fields that remained for grain production estimates have some level of freeze damage and in just about all counties hay and graze-out acres have gone up” – Gary Strickland.  

Although multiple fields in the Southwest and Southcentral region were affected by the freeze, the level of freeze damage largely varies across and within fields. At Jackson County for example some fields are severely damaged (80%) and some are not (5%). The south and west sides of the county seem to have a heavier damage. Tilman County is showing an average of 40% damage. The eastern to southeastern and along the south part of the county seems to have the greatest damage (60-80%) and the other parts with as low as 10% of damage. Greer County is showing an average of 33% damage.

Cotton County shows an average of 40% freeze damage. It is possible that only about 50% or less of the wheat planted will be harvested as several fields were already cut for hay.

Figure 1. Freeze-damaged head with “empty” green heads.

For more information about crop production and yield estimates across Oklahoma watch the 2020 Crop Reports Webinar here: https://youtu.be/UhxZt4KvgZY

Thanks to our field contributors

Aaron Henson – Tilman County Extension Educator

David Nowlin – Caddo county Extension Educator

Gary Strickland – Jackson and Greer County Extension Educator, SWREC Dryland Cropping System Specialist

Kyle Worthington – Canadian county Extension Educator

Melissa Koesler – Garvin County Extension Educator

Robert Calhoun – Senior Agriculturalist for the OSU Small Grains Program

Ron Wright – Custer County Extension Educator

Wheat Disease Update – 27 April 2020

This article was written by Bob Hunger, Extension Wheat Pathologist

Wheat diseases are active across Oklahoma, but perhaps the bigger story is the freeze damage that Dr. Amanda de Oliveira Silva has observed in south-central and southwestern OK.  For information on that, please see her update at: https://osuwheat.com/

Around Stillwater, wheat is mostly at or just past flowering with kernels beginning to form.  This is similar to the wheat I saw on a trip this past Friday to Chickasha (central OK), Altus and Tipton (southwestern OK).  However, Josh Anderson (Senior Research Associate, Noble Research Institute, Ardmore, OK) indicated to me in an email on 24-Apr that, “Most all local lines are well past flowering and at the soft dough stage.”

Based on that trip as well as samples received and input from others, I would offer the following to help explain the browning and death of upper leaves (flag leaf and F-1 leaf).  One factor is the freeze, which seems to cause a burning or death to the leaf tip up to the outer third of the leaf [see Dr. de Oliveira Silva’s post for photos of this (https://osuwheat.com/)].  Stripe rust is another factor involved, and has been reported to range from a low to a high incidence and severity.  Sometimes this striping has sporulation in it of urediniospores (yellowish-orange color – Figure 1-left photo), teliospores (black spore spots – Figure 1; center photo), or, just striping that is chlorotic that becomes necrotic (Figure 1; right photo).  Based on my recent trip, it appears that stripe rust across central and southern OK is moving from the urediniospore stage to the teliospore stage.  This transition indicates that temperature is becoming too warm for the stripe rust fungus to remain active, so spore production is being switched to teliospores.  Reports of leaf rust have been made [e.g., Josh Anderson (Senior Research Associate, Noble Research Institute, Ardmore, OK) in south-central OK and Gary Strickland (Extension Educator; Jackson County)], but presently the incidence and severity of leaf rust seems to be staying low.  However, an increase in leaf rust could become a reality as temperature increases and if moisture/dews remain common.

Figure 1.  Various expressions of wheat stripe rust observed across Oklahoma the week of April 20th.  Leaf with active sporulation of yellowish-orange urediniospores (left photo; Gary Strickland (Extension Educator; Jackson County), leaf with teliospores (center photo) and leaves with yellowing or dead stripes but with no or little sporulation (right photo).

Figure 1. Various expressions of wheat stripe rust observed across Oklahoma the week of April 20th. Leaf with active sporulation of yellowish-orange urediniospores (left photo; Gary Strickland (Extension Educator; Jackson County), leaf with teliospores (center photo) and leaves with yellowing or dead stripes but with no or little sporulation (right photo).

Septoria leaf blotch (Figure 2) is another disease that is contributing to the upper leaf browning this year.  Typically Septoria leaf blotch on wheat in Oklahoma is restricted to the lower and mid canopy, and only rarely reaches the upper canopy.  This year is one of those exceptions.

Figure 2. Septoria leaf blotch showing the blotchy, irregularly shaped dead areas on leaves with pycnida (black pepper spots – photo on the right) formed in the dead leaf tissue. Septoria leaf blotch typically is restricted to the lower and mid-canopy, but this year has been observed on upper wheat leaves (flag and F-1 leaves).

Finally, there also appears to be some upper leaf browning and death from a cause not related to a disease/pathogen.  The freeze may be involved, but there also may be some other physiologically related cause (Figure 3).  This discoloration and leaf death has been observed at multiple locations, and although possibly related to a freeze, it does not seem that freeze alone always can account for the damage.  To date, we have not been able to identify a cause for this damage.

Figure 3. Other upper leaf tissue burning and death does not appear to have a biotic (pathogen/disease) cause, but is may involve freeze damage or some other type of physiologically related cause. [photo on right from Mike Schulte; Kingfisher area]

A fungicide application will help manage this upper leaf spotting/burning/browning IF the cause is a pathogen/disease such as stripe rust or Septoria leaf blotch.  However, such an application will only protect the remaining green tissue and not be able to reverse any dead area and will not help if the discoloration is due to an environmental factor such as freeze.  Also keep in mind that only certain fungicides can be applied through flowering while others have a required time interval between application and harvest.  Some have both types of restrictions.  Hence, be sure to consult the label to be in compliance with the requirements as described on the label of the fungicide.

Finally, I also should indicated that a few samples have tested positive for the presence of Wheat streak mosaic virus.  One such sample was submitted from Kingfisher County, and another photo of a sample came from the Texas panhandle (Figure 4).  So, some of the mite-transmitted virus diseases such as wheat streak mosaic are present in Oklahoma and I would suspect as temperature increases more fields with symptoms of these diseases likely will appear.

Figure 4. Photo of wheat from Cimarron County sent in by Josh Bushong (Northwest Area Ext Agron Spclt) that is indicative of a mite-transmitted virus disease such as wheat streak mosaic, wheat yellow mosaic (high plains disease), or Triticum mosaic.