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Wheat disease update – 31 March 2014

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

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

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

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

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

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

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

Oklahoma wheat update 03/28/2014

On Friday, March 28th I made a tour through northwestern Oklahoma to diagnose a few problem fields and get a better feel for the wheat crop condition. I have provided a brief description of what I saw below. I did not make it to southwestern Oklahoma this trip, but by all accounts the wheat is dry, brown, and barely hanging on. A best case scenario in areas southwest of Apache this year is a poor wheat crop. It will have to rain a lot between now and harvest for this to happen.

Reports from Apache eastward are somewhat better. The wheat crop in this area still has potential, but the potential is declining. A farmer from the Hinton area called yesterday and indicated that moisture could still be found about 1 inch below the soil surface, but the top is still very dry. We need a soaking rain to move nitrogen into the rooting zone and to perk the crop up post dormancy.

My first stop this morning was at Lamont. Wheat in this area is smaller than normal and is at approximately Feekes GS5. There were several yellow areas in fields and uneven wheat. Much of this yellowing appeared to be nitrogen deficiency, but not all of it was due to insufficient top dress nitrogen. We simply have not had enough moisture to get good movement of top dress N into the rooting profile and for the wheat crop to take up applied N. Some of the yellowing was also due to drought stress. Some of the yellowing could have been due to brown wheat mite and/or winter grain mite activity (described more below).

My second stop was at our Cherokee variety plots. Wheat in this area was uneven, similar to Lamont. As shown in the picture below, part of our plot area was showing significant yellowing. Initially, I thought this was due to changes in soil type/nutrient variability. Upon closer inspection, this area was infested with brown wheat mite. These symptoms have only started to show in the last week or so. Thanks to variety trial cooperator Kenneth Failes, this situation will be remedied as soon as the wind settles.

The yellow, stunted areas in our Cherokee variety trial were caused by brown wheat mite

The yellow, stunted areas in our Cherokee variety trial were caused by brown wheat mite

 

Next stop was Alva, where the trend of uneven and yellow wheat continued. As shown in the picture below, there were several fields in the area with spots of dead or nearly dead wheat. Brown wheat mites were found in most of these fields and probably weakened plants which increased the amount of winterkill. In some fields seed had been placed at the proper depth, but the seed trenches were partially filled with residue rather than soil. Residue provides less insulation than soil and likely made heavy residue areas more prone to winterkill. I also noticed in these fields that the crown of the plant had developed in residue rather than soil, which likely increased winterkill. I looked at additional no-till fields in the area with severe winter injury, but plants that were still viable. Grazed fields seemed to have greater injury than non-grazed.

Areas of winterkill in no-till wheat near Alva

Areas of winterkill in no-till wheat near Alva

 

Although seeded at the proper depth, some wheat plants in heavy residue areas had crown placement at the soil surface. This increased the severity of winterkill.

Although seeded at the proper depth, some wheat plants in heavy residue areas had crown placement at the soil surface. This increased the severity of winterkill.

I looked at a few fields south of Enid. Unlike the fields in Grant, Alfalfa, and Woods Counties, this primary issue in these fields was winter grain mite instead of brown wheat mite. The symptoms were areas of the field having a silver tint. Some areas had died or lost several tillers and these areas got bigger as the season progressed and dry conditions worsened.

Field affected by winter grain mite south of Enid. Note the silver tint of the wheat on the left side of the terrace.

Field affected by winter grain mite south of Enid. Note the silver tint of the wheat on the left side of the terrace.

 

I ended my tour at Marshall, Oklahoma where I did not find any insects, but did find some thirsty wheat. All of the insect issues I encountered today can be corrected with scouting and insecticides. Wheat winterkill was present, but rarely affected entire fields and was not that widespread. The primary concern for all of Oklahoma remains lack of moisture. There are some fields in north central and northwestern Oklahoma with good yield potential; however, the best areas are starting to turn blue due to lack of moisture. Another couple of weeks of warm temperatures and wind without rain will turn blue wheat to brown. We need moisture.

Brown wheat mite showing up in winter wheat

by: Tom Royer, OSU Extension Entomologist

Our winter wheat has taken a beating this winter, with cold weather hanging on and some areas not getting that thirst quenching precipitation to help it get a great jump start this spring.  In addition, I have received scattered reports of brown wheat mites showing up and causing problems.  Producers need to remain alert so that their wheat is not suffering dual problems of dry growing conditions PLUS brown wheat mite.

Brown what mite can severely damage wheat that is already stressed due to drought or other adverse environmental conditions.

Brown what mite can severely damage wheat that is already stressed due to drought or other adverse environmental conditions.

Brown wheat mite is small (about the size of this period.) with a metallic brown to black body and 4 pair of yellowish legs.  The forelegs are distinctly longer that the other three pair. Brown wheat mites can complete a cycle in as little as 10-14 days.  They will undergo up to 3 generations each year, but have probably already completed at least one or two by now. Numbers will likely decline if a hard, driving rain occurs.  Spring populations begin to decline in mid-late April when females begin to lay “diapause” eggs.

Brown wheat mite causes problems in wheat that is stressed from lack of moisture.  They feed by piercing plant cells in the leaf, which results in “stippling”.  As injury continues the plants become yellow, then dry out and die.  These mites feed during the day, and the best time to scout for them is in mid-afternoon.  They do not produce webbing and will quickly drop to the soil when disturbed. They are very susceptible to hard, driving rains, but until then they can cause yield loss when present in large numbers

A closeup of a brown wheat mite. Photo courtesy Franklin Peairs, CSU.

A closeup of a brown wheat mite. Photo courtesy Franklin Peairs, CSU.

Brown wheat mites are about the size of a period at the end of a sentence and can be difficult to see with the naked eye.

Brown wheat mites are about the size of a period at the end of a sentence and can be difficult to see with the naked eye.

Research suggests that a treatment threshold of 25-50 brown wheat mites per leaf in wheat that is 6-9 inches tall is economically warranted.  An alternative estimation is “several hundred” per foot of row.

Check CR-7194, Management of Insect and Mite Pests in Small Grains for registered insecticides, application rates, and grazing/harvest waiting periods. It can be obtained from any County Extension Office, at www.wheat.okstate.edu, or by clicking here.

Brown wheat mite eggs in soil.

Brown wheat mite eggs in soil.

 

 

First hollow stem update 03/18/2014

With the exception of Brawl CL Plus, Centerfield, and a few experimental lines all of the varieties in our plots at Stillwater are at first hollow stem. I have posted the measurements from 21 March 2014 below. 

Variety cm of hollow stem 03/21/2014
Endurance .
Deliver .
Pete .
OK Bullet .
OK Rising .
Billings .
Ruby Lee 2.4
Garrison .
Duster .
Gallagher .
Iba 2.6
Everest .
Jackpot .
Doans .
Greer .
CJ .
SY Southwind .
Sy Llano .
Armour .
WB-Cedar .
WB-Redhawk .
WB-Grainfield 3.7
Winterhawk .
WB4458 .
T153 .
T154 .
T158 1.5
LCS Mint 1.5
LCS Wizard .
LCH11-109 .
LCH11-1117 .
LCH11-1130 .
TAM 112 .
TAM 113 .
Byrd .
Brawl CL Plus 0.9
Centerfield 0.8
Doublestop CL Plus 1.9
OK09125 1.1
OK09520 .
OK10126 1.0
OK08707W-19C13 3.4
OK10805W 0.9
OK10728W .
OK11754WF .

Wheat disease update – 21 March 2014

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

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

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

Reports/excerpts of reports from other states:

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

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

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

First hollow stem update 03/18/2014

Most wheat varieties are now at first hollow stem in our plots at Stillwater. I have posted the measurements from 18 March 2014 below.

Variety cm of hollow stem 03/18/2014
Endurance 1.5
Deliver 1.5
Pete 1.7
OK Bullet 3.2
OK Rising 3.0
Billings 2.2
Ruby Lee 1.2
Garrison 1.9
Duster 2.0
Gallagher 3.1
Iba 1.1
Everest 3.6
Jackpot 4.6
Doans 1.9
Greer 1.7
CJ 2.6
SY Southwind 3.6
Sy Llano .
Armour 2.4
WB-Cedar .
WB-Redhawk 2.7
WB-Grainfield 1.3
Winterhawk 1.8
WB4458 1.7
T153 3.0
T154 2.1
T158 1.0
LCS Mint 0.2
LCS Wizard 1.5
LCH11-109 2.0
LCH11-1117 2.4
LCH11-1130 2.3
TAM 112 3.8
TAM 113 3.5
Byrd 2.0
Brawl CL Plus 1.0
Centerfield 0.9
Doublestop CL Plus 0.9
OK09125 1.3
OK09520 1.6
OK10126 0.6
OK08707W-19C13 1.3
OK10805W 1.2
OK10728W 3.3
OK11754WF .
Sample Average 2.1

Wheat disease update – 14 March 2014

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

Oklahoma:  No foliar diseases of significance to report in Oklahoma.  Wheat is mostly just coming out of dormancy, and cold/dry conditions have not favored initiation of foliar diseases.  My soilborne/spindle streak nursery is starting to show symptoms of these virus diseases.  The wheat is just starting to “green-up,” so symptoms of this virus complex will become evident over the next couple weeks if a susceptible variety was planted in areas where these diseases are present.

Reports/excerpts of reports from other states:

Texas Dr. Amir Ibrahim (Prof, Small Grains Breeding and Genetics, Texas A&M University) 07-Mar-2014:  Our rust evaluation nursery was planted at Castroville, TX, about 12 miles west of San Antonio.  The wheat crop is now at Feeks stage 7‐9.  There is a mild buildup of leaf rust (Puccinia triticina) in the lower canopy of the spreader rows throughout the field. At this time last year, leaf rust was already 50S on ‘TAM 110’. The unusually cold weather that we have encountered this year did not favor rapid spread, but the disease seems ready to move if the weather starts to warm up.  Stripe rust (Puccinia striiformis) has been detected on some plots located in the middle of the field, and is mostly limited to a 600 ft2 area. Night temperatures for next week will range from 39 – 48 F, which will favor new infections by urediniospores and pick up in sporulation.

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

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

First hollow stem update 03/14/2014

WB-Cedar and Sy Llano reached first hollow stem this week, and there are several additional early-maturing varieties that are near first hollow stem. The results from a March 13 sampling of plots are posted below, and we will post results from another sample early next week. I have also posted the map from the Oklahoma Mesonet’s First Hollow Stem Advisor for medium maturity varieties. As indicated in the map, most wheat south of I-40 is likely at or past first hollow stem.

Probability of first hollow stem for medium maturity wheat varieties on 03/14/14

Probability of first hollow stem for medium maturity wheat varieties on 03/14/14

 

First hollow stem works as a pull off date for cattle on wheat pasture because it allows the plant a small amount of time prior to jointing to recover some of the green leaf area lost to grazing. As evidenced by the results posted on this blog, first hollow stem is running a good 1.5 to 2 weeks later than normal. Given the situation, it is advisable to consider removing cattle from wheat pasture sooner rather than later. In many cases this would be before the occurrence of first hollow stem. I make this recommendation because once our temperatures start to warm, it is likely that that wheat phenological development will proceed in rapid fashion. We could easily encounter a situation where there are only a few days separating first hollow stem and jointing. Pulling cattle from wheat pasture a little early will allow extra time for recovery, which might be needed this year.

Variety cm of hollow stem 03/13/2014
Endurance 0.5
Deliver 0.7
Pete 1.4
OK Bullet 0.4
OK Rising 0.5
Billings 1.1
Ruby Lee 0.4
Garrison 0.6
Duster 0.1
Gallagher 0.8
Iba 0.3
Everest 1.0
Jackpot 1.1
Doans 0.8
Greer 0.4
CJ 1.1
SY Southwind 1.0
Sy Llano 1.5
Armour 1.0
WB-Cedar 1.7
WB-Redhawk 0.7
WB-Grainfield 0.1
Winterhawk 0.7
WB4458 0.8
T153 0.8
T154 0.9
T158 0.5
LCS Mint 0.2
LCS Wizard 0.4
LCH11-109 0.3
LCH11-1117 0.8
LCH11-1130 0.6
TAM 112 1.3
TAM 113 1.4
Byrd 0.4
Brawl CL Plus 0.6
Centerfield 0.1
Doublestop CL Plus 0.4
OK09125 0.5
OK09520 0.3
OK10126 0.0
OK08707W-19C13 1.4
OK10805W 0.3
OK10728W 1.2
OK11754WF .
Average 0.7

First hollow stem update 03/11/2014

With the exception of one experimental line, there are still no varieties at the first hollow stem stage of growth at Stillwater. The results from a March 10 sampling of plots are posted below, and we will post results from another sample later this week. First hollow stem works as a pull off date for cattle on wheat pasture because it allows the plant a small amount of time prior to jointing to recover some of the green leaf area lost to grazing. As evidenced by the results posted on this blog, first hollow stem is running a good 1.5 to 2 weeks later than normal.

Given the situation, it is advisable to consider removing cattle from wheat pasture sooner rather than later. In many cases this would be before the occurrence of first hollow stem. I make this recommendation because once our temperatures start to warm, it is likely that that wheat phenological development will proceed in rapid fashion. We could easily encounter a situation where there are only a few days separating first hollow stem and jointing. Pulling cattle from wheat pasture a little early will allow extra time for recovery, which might be needed this year.

Variety cm of hollow stem 03/10/2014
Endurance 0.16
Deliver 0.00
Pete 0.32
OK Bullet 0.15
OK Rising 0.15
Billings 0.60
Ruby Lee 0.13
Garrison 0.20
Duster 0.02
Gallagher 0.84
Iba 0.17
Everest 0.60
Jackpot 1.09
Doans 0.04
Greer 0.33
CJ 0.07
SY Southwind 0.57
Exp F14 0.86
Armour 1.00
WB-Cedar 0.97
WB-Redhawk 1.08
WB-Grainfield 0.09
Winterhawk 0.35
WB4458 0.40
T153 0.64
T154 0.37
T158 0.07
LCS Mint 0.29
LCS Wizard 0.00
LCH11-109 0.00
LCH11-1117 0.12
LCH11-1130 0.88
TAM 112 1.03
TAM 113 0.84
Byrd 0.62
Brawl CL Plus 0.00
Centerfield 0.00
Doublestop CL Plus 0.00
OK09125 0.08
OK09520 0.05
OK10126 0.00
OK08707W-19C13 0.55
OK10805W 0.00
OK10728W 0.24
OK11754WF 1.61
Average 0.40

First hollow stem update 03/05/2014

First hollow stem is the optimal time to remove cattle from wheat pasture (full explanation). We measure first hollow in our September-sown wheat forage plots at Stillwater each year, and normally have approximately 50% of varieties at or past first hollow stem by March 1st. I have posted first hollow stem measurements from these plots in a table at the end of this blog. No varieties are currently at first hollow stem at Stillwater, but I anticipate the small amount of moisture gained from recent snow and warming temperatures will spur onset of first hollow stem over the next week or so. We will take another set of measurements on March 10 and report the results on this blog.

Keep in mind that the numbers reported from Stillwater are likely behind those being observed in southern Oklahoma and ahead of those observed in northern Oklahoma. Dillon Butchee in the Altus area reported finding first hollow stem in Jagger last week. The First Hollow Stem Advisor on the Oklahoma Mesonet indicates that  early varieties in southern Oklahoma are likely past first hollow stem and that early varieties in central Oklahoma will reach this point within a week. Keep in mind the one week projection uses historical weather conditions which exceed our current forecast. Cooler than normal conditions will not last forever, though, and my advice is to move cattle off of wheat pasture in southern Oklahoma yesterday, start moving them off of wheat pasture in central Oklahoma today, and move cattle off wheat pasture in northern Oklahoma next week.

Probability of first hollow stem for early varieties 03/05/2014

Probability of first hollow stem for early varieties 03/05/2014

One week projected probability of first hollow stem for early varieties 03/05/2014

One week projected probability of first hollow stem for early varieties 03/05/2014

Variety cm of hollow stem 03/05/2014
Endurance 0.00
Deliver 0.00
Pete 0.24
OK Bullet 0.00
OK Rising 0.00
Billings 0.62
Ruby Lee 0.04
Garrison 0.22
Duster 0.00
Gallagher 0.39
Iba 0.00
Everest 0.29
Jackpot 0.12
Doans 0.00
Greer 0.31
CJ 0.02
SY Southwind 0.11
Exp F14 0.03
Armour 0.22
WB-Cedar 0.51
WB-Redhawk 0.66
WB-Grainfield 0.10
Winterhawk 0.09
WB4458 0.00
T153 0.00
T154 0.23
T158 0.02
LCS Mint 0.02
LCS Wizard 0.02
LCH11-109 0.11
LCH11-1117 0.10
LCH11-1130 0.16
TAM 112 0.14
TAM 113 0.77
Byrd 0.12
Brawl CL Plus 0.00
Centerfield 0.00
Doublestop CL Plus 0.03
OK09125 0.00
OK09520 0.03
OK10126 0.00
OK08707W-19C13 0.02
OK10805W 0.02
OK10728W 0.02
OK11754WF 0.77
Average 0.15