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

Department of Entomology & Plant Pathology

Oklahoma State University – 127 Noble Research Center

405-744-9958

Wednesday through Friday (May 23-25) of last week, I was in western Oklahoma (Clinton area) and at field days in the panhandle at Goodwell and Hooker (Texas County), Keyes (Cimarron County) and Balko (Beaver County). The only disease observed of significance was indicated by white heads in fields. Often this was the result of Fusarium (dryland) root rot as reported in the last update (May 17, 2018). In fields showing this root rot, the white heads and white tillers were scattered across the field with an incidence ranging from low to moderate (Figure 1). Other fields in the panhandle exhibited large areas of not just white heads and tillers, but also white secondary tillers that had not headed. In these fields, some root rot was found, but Dr. David Marburger (OSU Small Grains Extension Specialist) and I believe that many of the white tillers/secondary tillers were the result of drought, freeze, or a combination of both. Often such tillers showed clean lower stems with no indication of root rot. We believe these secondary tillers were completely white without heading because they were sloughed off as a result of the stress from drought, freeze, or a combination of both. We suspect that more of these whiteheads will show in the coming week in northwestern OK and the panhandle, but the wheat crop is quickly turning and the whiteheads may not be as evident.

This likely is the last update I will be sending out this season as harvest in the southern half of Oklahoma has started with the crop quickly maturing in the northern half.

Figure 1.  White heads of wheat due to root rot. Typically the white heads are scattered in a field and can range from a low to high incidence. Notice in the middle photo just a few tillers of an individual plant are affected. [Credit for middle photo to Brad Babek, County Educator, Washita County]

Report by the Oklahoma Wheat Commission

Harvest for the 2018 season has begun in Oklahoma with combines rolling in the southwestern part of the state over the Memorial Day weekend. While much of the crop has been abandoned due to severe drought conditions in western regions of the state, some elevator locations in the south-central corridor have been reporting decent yields and favorable qualities on the wheat that is being harvested (the south-central corridor received rains in early spring that were timely). We have also had reports of wheat harvest beginning in central regions of the state around the Okarche, Kingfisher, Loyal, and Omega areas. While early reports are showing favorable proteins and test weights on the wheat being harvested, many elevator locations in the western part of the state predict this will be one of the fastest wheat harvests they have ever seen. This is based on all the acres abandoned due to the severe drought conditions that have plagued this part of the state since October. It is important to note we have also seen a decline in wheat acres due to increased cotton, sesame, and soybean plantings (one elevator location mentioned they hope to take in 10% of what they would in a normal year due to the drought and increased plantings of other crops). Producers are also hopeful the predicted storms tonight and Wednesday will pass thru without causing any damage.

Grandfield- Wheat harvest has just started in this region with most of the custom cutters now in town. On the wheat that was harvested over the weekend, test weights were running at 62 to 63 lbs./bu. Early protein reports were showing ranges from 11.5 to 12%. Yields from some of the producers have been reported better than expected with some reports of 40 to 50 bushel averages.

Frederick- Early reports from this region before the weekend had reports of one load of wheat coming in at 12.7% moisture, 62 lbs./bu., and protein at 12%. No yields from the weekend have been reported, although it is predicted that harvest will move rather quickly with little wheat harvested based on abandonment in the western half.

Snyder- This region took in over 85,000 bushels of grain over the weekend, and harvest is just starting to move at full speed. Reports so far on test weights have been exceptional with most of the wheat weighing 60 lbs./bu. or better. There have been a couple loads where weights were running 58 lbs./bu. The quality of the wheat has not had much dockage. Yields in this area have been reported all over the board ranging from the low 20’s to mid 40’s. No proteins have been reported.

Altus/Lone Wolf- Test weights on the wheat in this region have been averaging 60 to 62 lbs./bu. Proteins on the wheat to this point have been ranging from 10.5 to 12.5%, with more of the wheat coming in at that 11.5 to 12% protein range. No yields have been reported, although it is predicted that harvest will move extremely fast due to decline in planted acres of wheat and abandonment from the drought.

Sentinel- As of Tuesday morning, one sample was tested, but the moisture was too high.  Producers are hopeful they will be able to start harvest within the next day or two in this region.

Clinton- As of Tuesday morning, no wheat had been taken in this region. 

Hinton-  As of Tuesday morning, no wheat had been taken in this region.

Union City- One sample was taken at 14% moisture as of Tuesday morning, so producers are  hopeful that within in the next day harvest will get rolling in this region.

Banner- As of Tuesday morning, no wheat had been taken in this region.

Okarche- Wheat harvest has begun in this region on Memorial Day, with a few loads received. Test weights on the earlier harvested wheat was lower with ranges from the mid 50’s to 58 lbs./bu. Protein averages on earlier reports are coming in much better than the past couple years with ranges of 12 to 14% being reported. No yields were reported at this time.

Kingfisher- Harvest began over the weekend in this region with test weights averaging anywhere from 60 to 62lbs./bu. Proteins have been reported from as low as 10.9% to as high as 14%. Most of the proteins are coming in at 11.5% or higher on this earlier harvested wheat. Some yields have been reported to be making in the mid 40’s on what has been received so far. Keep in mind, much of the wheat has been abandoned west of the Kingfisher trade territory due to the persistent drought conditions that have existed since October.

Omega- Harvest has begun in this region on some of the earlier planted and heavily grazed wheat. Yields on the earlier wheat were reported to be making in the low 20’s.  Test weights were being reported at 56 to 58 lbs./bu.  Protein on one load of wheat was reported at 17.4%, and that variety was Doublestop CL+.  Producers are hopeful they will get into wheat that have better test weights and yields in this area towards the end of the week.

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

Department of Entomology & Plant Pathology

Oklahoma State University – 127 Noble Research Center

405-744-9958

Although not as obvious as in previous weeks, powdery mildew is still hanging on in Oklahoma, and has even moved up onto the heads in some fields. One such field is my foliar fungicide trial here at Stillwater. Examining this trial yesterday revealed many of the lower heads were lightly to moderately infected with powdery mildew (Figure 1). This is one of the few times I have seen powdery mildew move onto wheat heads in Oklahoma. It is important to note that these infected heads are the ones produced on the lower tillers beneath the main, taller tillers. I did not find any powdery mildew on any of the higher heads. This appears to me to be a light to moderate infection severity, but I have not had a lot of experience with powdery mildew on wheat heads, so this is just my estimation. Exactly how much of an impact this powdery mildew will have on yield and test weight may be hard to determine because the level of powdery mildew on these heads seemed to be fairly constant across all treatments.

Figure 1.  Powdery mildew on wheat heads in a foliar fungicide trial near Stillwater, OK. Note lower heads in background also show powdery mildew, but there was no powdery mildew on higher heads.

Yesterday, I also observed leaf rust on scattered leaves in the foliar fungicide trial at Stillwater (mostly in the not-sprayed control plots). Typically this was just a couple pustules scattered on a leaf, but there were a few leaves as shown in Figure 2. If you enlarge Figure 2, you can see what looks like the remnant of stripe rust stripes with a few telia (small black dots) associated with the stripes. There also appears to be a pustule or two of powdery mildew. As indicated, leaves infected to this level were not common, but this does indicate that leaf rust is starting to appear and may increase a bit over the next 7-10 days. However, this is a late infection as this trial is at late milk to early soft dough. Hence, the leaf rust will have only a minimal impact on yield even if it does increase significantly.

Figure 2.  Leaf rust on a flag leaf at Stillwater, OK on May 16, 2018. Note that some inactive stripe rust also is visible in the center of the leaf (you will have to enlarge the photo to see this) but it appears to be “shutting down” as indicated by the small, black telia. A lesion or two of powdery mildew also is present.

Finally, Brad Babek (County Educator, Washita County in southwestern Oklahoma) reported increasing areas of white heads in wheat fields (Figure 3). In cases where I have observed such heads this year, it has been due to dryland (Fusarium) root rot. Typically the roots will be rotted and often the lowest part of the stem is discolored (dark) and often there is a pinkish-purple color associated with the lower tiller and roots. Splitting such a tiller often reveals a stem filled with white or pinkish-white fungal growth (Figure 3).

Figure 3.  Whiteheads on wheat tillers in Washita County (western Oklahoma). Photo and report credit to Brad Babek, County Educator, Washita County.

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

Department of Entomology & Plant Pathology

Oklahoma State University – 127 Noble Research Center

405-744-9958

This past week I was at field days in southwestern Oklahoma (Apache and Altus), and northeastern Oklahoma (Afton). I did not see a single leaf or stripe rust pustule at any location. Wheat in southwestern OK ranged from at flowering to kernel formation, and typically was short (less than knee high). There were a few exceptions to this, namely a couple fields near Apache that had been planted on summer fallow ground. Wheat in these two fields looked good with some powdery mildew on the low to mid-canopy. There also was evidence of root rot (white heads) that was caused by Fusarium (Figure 1). This root rot was at a low incidence. By contrast, wheat in northeastern OK was at flowering and typically was over knee-high, thick, and with high yield potential. On many varieties, powdery mildew was heavy in the low and mid-canopy, and in a few instances also was present on the flag leaf (Figure 2). Besides powdery mildew, Septoria leaf blotch was heavy throughout the lower leaves of most varieties. In northeastern OK it appears that if a fungicide is going to be sprayed, that needs to be applied as soon as possible.

Based on my observations this past week and the recent report from Dr. Clark Neeley (see below), it appears that rust pressure is low across Texas and Oklahoma. Based on Dr. Neeley’s report, it appears that leaf rust has started to appear, but is still somewhat limited. Hence, although there still is time for the rusts (especially leaf rust) to impact Oklahoma, it does not appear there will be an early season (during heading) high rust pressure as in most years. I still would be watchful and if you have a variety known to be susceptible to leaf rust with good yield potential (>about 30 bu/acre) I recommend considering a fungicide application. Be sure however, that your wheat has not matured past the allowed time (as indicated on the label) for the fungicide you apply. Additional information related to foliar fungicides can be found on the fungicide label and in OSU Current Reports 7668, Foliar Fungicides and Wheat Production in Oklahoma, which is available at:

http://wheat.okstate.edu/wheat-management/diseasesinsects/CR-7668web2018.pdf.

Reports from other states:

Texas – 4-30-2018; Dr. Clark Neeley; Small Grains/Oilseed Extn Specialist; Texas A&M AgriLife Extension.  “I was attending field days across Central Texas last week and saw mostly leaf rust as I travelled around. Pressure was strong at Thrall, McGregor and Temple, TX, but wheat is pretty far along in all three locations. Mostly in the milk and soft dough stage. I was in a variety trial and producer’s field in Abbott, TX just north of Waco and leaf rust was nearly undetectable despite the field only receiving a Tilt fungicide application at topdress. Stripe rust was still active on ‘Patton’ border there, but teliospores were appearing and thus was shutting down. Did not find any stripe rust in any of the trial entries. I found no or negligible amounts of stripe rust on trial entries at all locations except McGregor. I did find low levels of stripe rust there on flag leaves of HRWW varieties ‘TAM 304’ and ‘WB 4303’ and SRWW variety ‘USG 3120’. Will be at field days later this week and the following week in the Rolling Plains and Northeast Texas and will try to post updates then for those regions.”

Figure 1.  Fusarium (dryland) root rot observed on a wheat tiller from a variety demo near Altus, OK. Note the reddish-purple color near the tiller base with fuzzy reddish-purple fungal growth also present inside the split stem (bottom photo).

Figure 2.  Powdery mildew on the flag leaf of a wheat plant in the variety trial near Afton, OK.