Amanda de Oliveira Silva, Small Grains Extension Specialist
I feel like this year’s planting season started like “Hurry up and wait! ” as my colleague Gary Strickland would say.
We had a great start with dual purpose wheat planting. There were lots of drills rolling around the state, and we were able to plant our dual-purpose trials in good soil moisture at 1 to 1.5 inches deep. However, with the wind blowing hard, temperature in the 80-90’s in some days, and lack of rain in the past few weeks, the soil has been drying up quickly in many areas of the state. There is a small or no chance of rain in the forecast for the next two-three weeks, and I am hearing producers discuss whether to park their drill for now or dust in wheat.
According to Wes Lee, the Oklahoma Mesonet Ag coordinator, rainfall is going to be very limited unless one of the tropical storms moves further west than expected. Dewpoints are very low, so if a rain occurs it will be light. He also mentioned that our current situation is a result of the moderate La Nina ENSO pattern, which tends to bring the driest falls and winters to Oklahoma. Gary McManaus, the Oklahoma Mesonet State Climatologist, says that predictions are not favorable at this moment, and we will likely see drought development and intensification by the end of the month and year in Oklahoma.
As of October 4th, 45% of Oklahoma wheat was already planted and 20% emerged, which is about the same as the 5-year average (USDA-NASS, 2020). They also reported that we are 54% short and 34% adequate in topsoil moisture, and 33% short and 56% adequate in subsoil moisture. Figure 1 shows the 4” plant available water in the soil at this time of the year for 2019 and this year.
With a likely drought scenario for fall and dry conditions advancing quickly in our state, it is good to have in mind the possible effects of drought on the wheat germination and early growth.
Wheat germination and emergence in dry soils
The most important physiological requirement for wheat to germinate and sustain the developing seedling is soil water. Therefore, planting decisions needs to be based on a combination of available soil moisture and expected rainfall. In addition, other factors such as adequate seeding depth, sowing date, soil fertility, seed treatment, seed quality, etc. should be considered to guarantee a good crop establishment. For more information, check our previous blog post (planting-date-and-seeding-rate-considerations-for-winter-wheat) and the materials on our website.
Wheat seeds need a minimum water content of 35 to 45 % of its dry weight to initiate germination, and germination will increase as moisture levels increase. Dry soils can still have a relative humidity of 99%, and that can be enough moisture for seeds to germinate, it might just take longer than if it were in moist conditions. My concern with the current situation in Oklahoma, is the lack of rain in the forecast. This could result in enough moisture to start the germination process in certain areas of the state, but the seedling emergence and growth could be compromised if we don’t see any rain soon.
What happens if the soil completely dries out before wheat emergence?
There are three phases during the germination process; water absorption, activation for when the seed coat is ruptured, and visible germination for when the radicle emerges, followed by the seminal roots and coleoptile. These processes will start and stop depending on the soil moisture. Thus, if the soil dries out before the roots and shoots are visible, the seed remain viable and the germination will be paused and continue once water is available. However, if the soil dries out after those structures are emerged (approximately 4-5 days after germination has begun), the seedling may not tolerate the lack of water resulting in loss or incomplete stand.
What should I do then? Choose your battle!
The optimal time for planting wheat in a grain-only system in Oklahoma is around Mid-October. So, I would say we still have a week of wiggle room to decide what do. There are different ways we can go about it, but we must keep in mind that there is always risk involved when planting wheat in dry conditions.
If you decide to dust in your wheat and wait for rain for wheat to germinate, watch your seeding depth. The optimum seeding depth to plant wheat is about 1-1.5” deep. We typically don’t have as many issues with winterkill in Oklahoma as they do in more northern states, so I am comfortable with dusting in at about 0.75 – 1” deep. Planting at 0.5” or less is too shallow in most circumstances. Also, there is always a chance for pounding rain occurring and forming soil crusts which makes it difficult for the coleoptile to push through the soil surface and may result in poor emergence. Fields with stubble cover may be less affected by pounding rain and reduce the risks of soil crusts forming. If the forecast follows through, and we receive rain in the next weeks, it would be light, and that could cause wheat to emerge but may be not enough for wheat to continue growing. Most of the field I visited in the past days had good subsoil moisture, so that could help!
If you decide to plant deeper to reach moisture, be careful with the coleoptile length of the variety you have, and make sure it has a long-enough coleoptile that will allow emergence if conditions are favorable. Consider increasing seeding rate to compensate for the low emergence which is prone to occur in this situation.
Should we wait for rain to plant then? This is a farm by farm call and it depends on which source of risk you find most comfortable. Personally, I would rather plant my wheat in the optimal planting window and adequate seeding depth than waiting for a rain that may take too long to happen or missing my optimal planting window. If the latter is the case, make sure to bump your seeding rate to try to compensate for the reduced time for tillering. Planting wheat at optimal time allows for more time for root growth in seedlings, helping the crop to have a quicker establishment under dry conditions and possibly help the plant to scavenge for water that is available deeper in the soil profile.
Are there any specific agronomic traits that could help wheat seedling growth under water stress?
Traits that could help with seedling growth in dry conditions are the coleoptile length, which allows to plant a little deeper in moisture and good emergence (if deep planting is the practice of your choice). There are indications that sowing wheat varieties with larger seed may help to reduce the negative effects of drought during early growth (Mian and Nafziger, 1994). In general, the greater reserve of larger seeds results in a faster germination and crop establishment by increasing root growth and tiller production. Although, there are varieties with small seed size that germinate better than larger seeded varieties, demonstrating that genetics can also play an important role on the ability of variety to germinate in dry soils.
Wheat is known to be a resilient crop and to adapt to the low soil water availability, wheat that has already emerged will try to reduce transpiration (i.e. water losses from leaves) by reducing tillering and forage production.
Summary for managing wheat in dry conditions
Planting options: Dust in wheat at 0.75 – 1” deep, plant deeper to reach moisture, or just wait for a possible rain
Optimal timing for planting grain-only systems is Mid-October
Increase seeding rate if planting later than the optimal time
Plant varieties with long coleoptile length if planting deeper to reach moisture
There is no need for additional N in the fall as crops will not be using N in dry conditions
Don’t hesitate to contact your County Extension office.
For references cited in this post and additional information, see below:
GRDC. Grain Research and Development Corporation, Australia. 2016. Wheat – Plant growth and physiology. https://grdc.com.au/__data/assets/pdf_file/0026/370673/GrowNote-Wheat-North-04-Physiology.pdf
Lollato R. and Holman J. 2020. Considerations when planting wheat into dry soil. K-State Agronomy eUpdate – Issue 821. https://eupdate.agronomy.ksu.edu/article_new/considerations-when-planting-wheat-into-dry-soil-409
Mesonet Oklahoma http://www.mesonet.org/index.php/forecast/local_and_regional
Mian and Nafziger, 1994. Seed Size and Water Potential Effects on Germination and Seedling Growth of Winter Wheat. Crop Science. 34(1), 169-171. https://doi.org/10.2135/cropsci1994.0011183X003400010030x
Shroyer J.P., Kok H., and Thompson C.R. Planting Practices in Wheat Production Handbook. K-State C529. https://bookstore.ksre.ksu.edu/pubs/c529.pdf.
USDA-NASS, 2020. Oklahoma Crop Progress and Condition. October 5, 2020. https://www.nass.usda.gov/Statistics_by_State/Oklahoma/Publications/Crop_Progress_&_Condition/2020/ok-cw-10-04-2020.
This article was written by Dr. Bob Hunger, Extension Wheat Pathologist and Dr. Tom Royer, Extension Entomologist
Planting date: Much of the winter wheat sown in Oklahoma is used as a dual-purpose crop. In such a system, wheat is grazed by cattle from late fall through late winter/early spring and then harvested for grain in early summer. In a grain-only system, wheat is generally planted in October, but in a dual-purpose system wheat is planted in early to mid-September to maximize forage production. Planting wheat early significantly increases the likelihood that diseases and insect pests such as mite-transmitted viruses, the aphid/barley yellow dwarf complex, root and foot rots, and Hessian fly will be more prevalent and severe. For more detailed information on planting date and seed treatment considerations on wheat, see CR-7088 (Effect of Planting Date and Seed Treatment on Diseases and Insect Pests of Wheat) at: http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-7836/CR-7088web2012.pdf
Mite-transmitted virus diseases. These virus diseases are transmitted by wheat curl mites (WCMs) (Figure 1), and include wheat streak mosaic (WSM), high plains disease (HPD), and Triticum mosaic (TrM). Of these, WSM is the most common. WCMs and these viruses survive in crops such as wheat, corn, and sorghum as well as many grassy weeds and volunteer wheat. In the fall and spring, WCMs spread to emerging seedling wheat, feed on that seedling wheat, and transmit virus to the young wheat plants.
Given this disease cycle, it is easy to see several factors that determine the incidence and severity of these diseases. First, controlling volunteer wheat and other grassy weeds that serve as alternative hosts for the mite and the viruses is imperative to help limit these diseases. Often an infected field of commercial wheat is growing immediately adjacent to a field left fallow during the fall and winter (Figure 2). The fallow field contained abundant volunteer wheat and grassy weeds from which WCMs carrying Wheat streak mosaic virus (WSMV) spread into the commercial field. Wheat infected in the fall will be severely damaged the next spring. Wheat infected in the spring also is damaged, but not as severely as wheat infected in the fall. Hence, it is imperative to do yourself and your neighbors a favor by controlling volunteer wheat and grassy weeds in fields left fallow – especially, if they are adjacent to commercial wheat fields.
A second factor linked to the severity of these mite-transmitted virus diseases is planting date. Early planting dates associated with grazing provides for a much longer time period in the fall for mites to spread to and infect seedling wheat. Planting later in the fall (after October 1 in northern OK and after October 15 in southern OK) and controlling volunteer wheat are the two practices that can be employed to help manage these diseases. It is extremely critical that volunteer wheat is completely dead for at least two weeks prior to emergence of seedling wheat because WCMs have a life span of 7-10 days. Thus, completely killing or destroying volunteer wheat for a period of at least two weeks prior to emergence of seedling wheat will greatly reduce mite numbers in the fall.
The incidence and severity of these mite-transmitted virus diseases as affected by planting date can be illustrated by the number of samples that tested positive for WSMV and HPV during each of the last three years. In 2017, which was the last year mite-transmitted virus diseases were prevalent in Oklahoma, 103 wheat samples were tested by the Plant Disease and Insect Diagnostic Lab at OSU for presence of mite-transmitted viruses. Of these 103 samples, 69 (67%) tested positive for WSMV and 22 (21%) tested positive for HPV. In 2018, only 12 of 126 (10%) samples tested positive for one or both of these viruses. In 2019, only 21 samples were submitted for testing with 7 samples (33%) testing positive for WSMV (no positives for HPV). In 2020, few samples (less than 5) tested positive for any of these viruses. This lower number of positive samples in 2019 and 2020 likely was the result of an overall later planting date of wheat in the fall of 2018 due to wet conditions and in fall 2020 due to extremely dry conditions. I believe this later planting date in conjunction with more awareness and action in limiting the green bridge helped to lower the incidence and severity of the mite-transmitted viruses in Oklahoma in both 2019 and 2020.
Finally, seed treatments and insecticides are not effective in controlling the mites or these mite-transmitted virus diseases. Regarding resistant varieties, there are several winter wheat varieties that have resistance to either WSM or the curl mites, but the adaptation of these varieties to Oklahoma is limited, and the resistance is not typically an absolute resistance to the disease. Hence, severe and continuous disease pressure especially at higher temperature (greater than about 75 F) can overcome the resistance. For more information on mite-transmitted virus diseases, see OSU Fact Sheet 7328 (Wheat Streak Mosaic, High Plains Disease and Triticum Mosaic: Three Virus Diseases of Wheat in Oklahoma) at: http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-8987/EPP-7328.pdf
Aphid/barley yellow dwarf (BYD) complex: Viruses that cause BYD are transmitted by many cereal-feeding aphids (Figure 3). BYD infections that occur in the fall are the most severe because virus has a longer time to damage plants as compared to infections that occur in the spring. Several steps can be taken to help manage BYD. First, a later planting date (after October 1 in northern Oklahoma and after October 15 in southern Oklahoma) helps reduce the opportunity for fall infection. Second, some wheat varieties tolerate BYD better than other varieties; however, be aware that no wheat variety has a high level of resistance to the aphid/BYD complex. For a listing of reaction of wheat varieties to BYD, other diseases and insect pests, and agronomic traits there are several sources available including variety comparison charts from Oklahoma State University (http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-6107/PSS-2142web2018.pdf) and Kansas State University (https://bookstore.ksre.ksu.edu/pubs/MF991.pdf), and the annual wheat variety publication titled, “Wheat Varieties for Kansas and the Great Plains by Layton Ehmke (34 Star Publishing Inc.; firstname.lastname@example.org; https://thewheatfarmer.com; 1-844-643-0170). Third, control aphids that transmit the viruses that cause BYD. This can be done by applying contact insecticides to kill aphids, or by treating seed before planting with a systemic insecticide. Unfortunately, by the time contact insecticides are applied, aphids frequently have already transmitted the viruses that cause BYD. Systemic seed-treatment insecticides containing imidacloprid or thiamethoxam can control aphids during the fall after planting. This may be particularly beneficial if wheat is planted early to obtain forage. Be sure to thoroughly read the label before applying any chemical.
Hessian fly: Hessian fly (Figure 4.) infestations can occur in the fall and spring. Fall infestations arise from over-summering pupae that emerge when climate conditions become favorable. In states north of Oklahoma, a “Hessian fly free” planting date often is used to help limit fall infestations by Hessian fly. However, such a planting date does not apply in Oklahoma because Hessian fly can emerge in Oklahoma as late as December (Figure 5.).
Delayed planting (after October 1 in northern Oklahoma, and after October 15 in southern Oklahoma) can help reduce the threat of Hessian fly, but a specific “fly free date” does not exist for most of Oklahoma as it does in Kansas and more northern wheat-growing states. This is because smaller, supplementary broods of adult flies emerge throughout the fall and winter. A number of varieties are resistant to Hessian fly; for a listing of reaction of wheat varieties to Hessian fly, other diseases and insect pests, and agronomic traits there are several sources available including variety comparison charts from Oklahoma State University (http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-6107/PSS-2142web2018.pdf) and Kansas State University (https://bookstore.ksre.ksu.edu/pubs/MF991.pdf), and the annual wheat variety publication titled, “Wheat Varieties for Kansas and the Great Plains by Layton Ehmke (34 Star Publishing Inc.; email@example.com; https://thewheatfarmer.com; 1-844-643-0170). Hessian fly infestations can be reduced somewhat by destroying volunteer wheat in and around the field at least two weeks prior to emergence of seedling wheat. Seed treatments that contain imidacloprid or thiamethoxam will also help reduce fall infestations of seedling wheat, especially if combined with delayed planting and volunteer destruction. For more information on Hessian fly, see OSU Fact Sheet: EPP-7086 (Hessian fly Management in Oklahoma Winter Wheat) at:http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-6189/EPP-7086web2015.pdf
Root and foot rots: These are caused by fungi and include several diseases such as dryland (Fusarium) root rot, Rhizoctonia root rot (sharp eyespot), common root rot, take-all, and eyespot (strawbreaker). Every year samples are received in the lab that are diagnosed with root rot. Typically wheat affected by seedling/root rots are either submitted in the fall when wheat is in the seedling stage or in later May and early June as plants are maturing. Germinating seeds and seedlings have small root systems that if infected impacts seed germination and seedling emergence (Figure 6). Later in the season (late May/early June), root rots again become apparent as maturing plants are unable to obtain sufficient moisture to finish grain development especially if drought conditions are present. In mature plants, white heads often indicates the presence of root rot (Figure 7).
In 2017-2018, the incidence and severity of root rots across Oklahoma dramatically increased compared to the 2016-2017 season. This increase likely resulted from weather conditions that favored the root rots along with heat and drought in May/June of 2018 that promoted white heads to develop. Dryland (Fusarium) root rot was the most common root rot observed in 2018, and caused significant damage to wheat in southwestern, western, northwestern OK as well as the panhandle. In 2018-2019, dryland (Fusarium) root rot again became prevalent across much of Oklahoma, but was not as damaging as the previous year likely because ample moisture and cool temperatures meant that water stress on plants was much less than in 2017-2018. Root rots were only sparsely observed in 2019-2020 and only at low severity. Controlling root and foot rots is difficult. There are no resistant varieties, and fungicide seed treatments with activity toward the root and foot rots are effective in protecting germinating seed and emerging seedlings, their activity usually involves early-season control or suppression rather than control at a consistently high level throughout the season. Often, there also are different “levels” of activity related to different treatment rates, so again, CAREFULLY read the label of any seed treatment to be sure activity against the diseases and/or insects of concern are indicated, and be certain that the seed treatment(s) is being used at the rate indicated on the label for activity against those diseases and/or insects. Later planting (after October 1 in northern Oklahoma and after October 15 in southern Oklahoma) also can help reduce the incidence and severity of root rots, but planting later will not entirely eliminate the presence or effects of root rots. If you have a field with a history of severe root rot, consider planting that field as late as possible or plan to use it in a “graze-out” fashion if that is consistent with your overall plan. For some root rots, there are specific factors that contribute to disease incidence and severity. For example, a high soil pH (>6.5) greatly favors disease development of the root rot called take-all. OSU soil test recommendations factor in this phenomenon by reducing lime recommendations when continuous wheat is the intended crop. Another practice that can help limit take-all and some of the other root rots is the elimination of residue. However, elimination of residue by tillage or burning does not seem to affect the incidence or severity of eyespot (strawbreaker).
Seed treatments: There are several excellent reasons to plant seed wheat treated with an insecticide/fungicide seed treatment. These include:
1. Control of bunts and smuts, including common bunt (also called stinking smut) and loose smut. The similarity of these names can be confusing. All affect the grain of wheat, but whereas common bunt spores carryover on seed or in the soil, loose smut carries over in the seed. Seed treatments labeled to control bunts and smuts are highly effective. If common bunt (stinking smut) was observed in a field and that field is to be planted again with wheat, then planting certified wheat seed treated with a fungicide effective against common bunt (stinking smut) is strongly recommended. If either common bunt (stinking smut) or loose smut was observed in a field, grain harvested from that field should not be used as seed the next year. However, if grain harvested from such a field must be used as seed wheat, treatment of that seed at a high rate of a systemic or a systemic + contact seed treatment effective against common bunt (stinking smut) and loose smut is strongly recommended. In 2020, loose smut in fields and common bunt in harvested grain was observed at higher incidence and severity than for several years, so I strongly recommend planting certified wheat seed that was been treated with a fungicide labeled for control of bunt and smut. For more information on common bunt (stinking smut) & loose smut, see: http://www.entoplp.okstate.edu/ddd/hosts/wheat.htm and consult the “2020 OSU Extension Agents’ Handbook of Insect, Plant Disease, and Weed Control (OCES publication E-832),” and/or contact your County Extension Educator.
2. Enhance seedling emergence, stand establishment and forage production by suppressing root, crown and foot rots. This was discussed above under “Root and Foot Rots.”
3. Early season control of the aphid/BYDV complex. This can be achieved by using a seed treatment containing an insecticide. Be sure that the treatment includes an insecticide labeled for control of aphids.
4. Control fall foliar diseases including leaf rust and powdery mildew. Seed treatments are effective in controlling foliar diseases (especially leaf rust and powdery mildew) in the fall, which may reduce the inoculum level of these diseases in the spring. However, this control should be viewed as an added benefit and not necessarily as a sole reason to use a seed treatment.
5. Suppression of early emerged Hessian fly. Research suggests that some suppression can be achieved, but an insecticide seed treatment has little residual activity past the seedling stage and Hessian fly often infests wheat after the seedling stage.
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.
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 City – Harvest 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.
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.
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.
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.
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.
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/Gotebo– Harvest 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%.
Apache– Harvest 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/Rocky– Harvest 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/Omega – This 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.
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%.
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.
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/Rocky– Harvest 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/Hennessey– This 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.
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).
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.
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.
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.
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.
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.
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.