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Wheat and Corn Pathology Update

Wheat and Corn Pathology Update published on No Comments on Wheat and Corn Pathology Update

Wheat and Corn Pathology Update (4/15/2016)

Trey Price, Field Crop Pathology, Macon Ridge Research Station

Boyd Padgett, Wheat Pathology, Dean Lee Research Station

Wheat

At the time of this writing, most wheat in the state is at or past flowering with the exception of some later maturing varieties.  We have seen issues with vernalization in a few entries in variety trials throughout the state.  Simply, there was not enough cold weather to trigger reproductive development.  Fusarium head blight (scab, Figures 1 & 2) has been of utmost concern to the few wheat producers we have this year.  Conditions have been favorable for scab during flowering, and applications of Caramba or Prosaro using maximum rates and water volumes are recommended for management.  The best control we can expect is 50%, and time will tell if applications were successful or not.

 

 

Figure 1 (Fusarium head blight).
Figure 1 (Fusarium head blight).

 

Figure 2 (scabby kernels below healthy ones).
Figure 2 (scabby kernels below healthy ones).

Other concerns this season have been stripe rust (Figure 3) and leaf rust (Figure 4).  Conditions are currently favorable for both diseases; however, stripe rust activity is slowly decreasing and leaf rust activity is increasing rapidly.  Most varieties are resistant to stripe, leaf, or both rusts, and fungicide applications are usually not necessary.  In susceptible varieties, rusts are effectively and economically managed with triazole fungicide applications.

 

Figure 3 (stripe rust).
Figure 3 (stripe rust).
Figure 4 (leaf rust).
Figure 4 (leaf rust).

 

Other diseases of note have been Septoria leaf blotch (Figure 5) and bacterial streak (Figure 6).  Septoria usually remains low in the canopy and does not escalate to damaging levels; however, if infections occur on the flag leaf or flag leaf -1, a fungicide application may be warranted.  Most fungicides provide adequate control of Septoria leaf blotch.  Bacterial streak cannot be reactively managed.  Fungicides are not effective, of course, so variety selection in the fall is the primary management technique.  LSU AgCenter scientists rate wheat varieties for multiple diseases at multiple locations in the state, and the results are available online (www.lsuagcenter.com), from your county agent, or your nearest research station.  Bacterial streak and Septoria leaf blotch can be difficult to diagnose.  Older Septoria lesions will have black spots (pycnidia) within lesions, while bacterial streak will not.  Younger Septoria lesions may be indistinguishable from bacterial streak lesions; therefore, a quick diagnostic method can be used.  First, cut an affected leaf section then submerge in water.  Wait 5-10 minutes, and observe for bacterial streaming (Figure 7).  This can be accomplished on the turn row with a pocket knife and bottled water.

 

Figure 5 (Septoria leaf blotch).
Figure 5 (Septoria leaf blotch).

 

 

    

Figure 5 (Septoria leaf blotch). Figure 5 (Septoria leaf blotch). Figure 6 (bacterial streak).
Figure 6 (bacterial streak).

 

Figure 7 (bacterial streaming).
Figure 7 (bacterial streaming).


Corn

It is no secret that this has been a tough year for corn so far.  Soon after early planting, most producers received copious amounts of rainfall (particularly in NELA) over an extended period.  Many fields were replanted because of flooding.  On stands that withstood the flooding, the majority of field calls have involved corn plants that had poor nodal root development causing them to fall over (Figures 8 & 9) and stressing or breaking the mesocotyl (first true stem) in the process (Please see Dr. Dan Fromme’s post for more information on rootless corn syndrome (RCS)  http://louisianacrops.com/category/crops/corn/).  Most producers planted on the higher end of plant populations allowing tolerable losses due to RCS.

 

 

 Figure 8 (plant death as a result of RCS).
Figure 8 (plant death as a result of RCS).

 

Figure 9 (normal vs. poor nodal root development).
Figure 9 (normal vs. poor nodal root development).

 

Interestingly, damping off (Rhizoctonia solani) was commonly observed in RCS situations where fields had been planted for at least one month (V3-V4).  Over time, seed treatment efficacy declined, plants were stressed (particularly at the mesocotyl), and the pathogen took advantage of optimal environmental conditions.  Classic damping off lesions were observed on the upper sections of mesocotyl (Figures 10 & 11), and the pathogen was subsequently isolated in the laboratory.

 

 

 Figure 10 (damping off).
Figure 10 (damping off).

 

 Figure 10 (damping off).
Figure 10 (damping off).

 

Since we have a significant number of corn acres that will be relatively late, foliar diseases, southern rust (Figures 12 & 13) in particular, will likely be a concern this year.  Southern rust (SR) can be devastating if it develops early (tasseling or before) and conditions (warm, wet) are favorable for development.  Scouting is key to managing this disease.  Typically SR will develop low in the canopy and progress upward.  Fungicides are effective on SR (Table 1).  If the disease is present at or before tasseling, fungicide applications are warranted.  Depending on disease severity and prevailing environmental conditions, applications could occasionally be warranted between tasseling and milk stage.  Applications are rarely warranted after this stage, because the crop will usually “out-run” disease progression.  Keep in mind that tasseling is the most vulnerable stage to foliar diseases.  As plants mature, more defoliation can be tolerated as time goes by.

 

Figure 12 (southern rust on upper surface of leaf).
Figure 12 (southern rust on upper surface of leaf).

 

 Figure 13 (southern rust on leaf sheath).
Figure 13 (southern rust on leaf sheath).

Northern corn leaf blight (NCLB) is an annual problem in Louisiana.  In fact, we can probably drop the “northern” at this point.  Scouting also is key to managing this disease.  Similar to SR, if NCLB develops during late vegetative stages or near tasseling, a fungicide application may be advisable.  Once the disease initiates, it will continue to progress for the remainder of the season.  Hot and dry weather may slow NLCB progression somewhat, but with most of our acreage irrigated, temperature and moisture requirements for the pathogen are satisfied until black layer.  Specific fungicide efficacy data on NCLB remains elusive; however, pooling of nationwide data indicates that fungicides are effective on NCLB (Table 1).  Similar to SR, the further the crop is past tasseling, more defoliation can be tolerated.

For more information please do not hesitate to contact your local county agent, specialist, or nearest research station.  Please visit our websites (www.lsuagcenter.com and www.louisianacrops.com) for the latest in field crop pathology.

 

 

 

 

 

Table 1.  Fungicide Efficacy for Control of Corn Diseases—April 2016

The Corn Disease Working Group (CDWG), which includes many members from the mid-South including several pathologists from Louisiana, has developed the following information on fungicide efficacy for control of major corn diseases in the United States.  Efficacy ratings for each fungicide listed in the table were determined by field testing the materials over multiple years and locations by the members of the committee. Efficacy ratings are based upon level of disease control achieved by product, and are not necessarily reflective of yield increases obtained from product application. Efficacy depends upon proper application timing, rate, and application method to achieve optimum effectiveness of the fungicide as determined by labeled instructions and overall level of disease in the field at the time of application. Differences in efficacy among fungicide products were determined by direct comparisons among products in field tests and are based on a single application of the labeled rate as listed in the table.  Table includes systemic fungicides available that have been tested over multiple years and locations. The table is not intended to be a list of all labeled products1. Efficacy categories: NR=Not Recommended; P=Poor; F=Fair; G=Good; VG=Very Good; E=Excellent; NL = Not Labeled for use against this disease; U = Unknown efficacy or insufficient data to rank product

1Additional fungicides are labeled for disease on corn, including contact fungicides such as chlorothalonil. Certain fungicides may be available for diseases not listed in the table, including Gibberella and Fusarium ear rot. Applications of Proline 480 SC for use on ear rots requires a FIFRA Section 2(ee) and is only approved for use in Illinois, Indiana, Iowa, Louisiana, Maryland, Michigan, Mississippi, North Dakota, Ohio, Pennsylvania, and Virginia.

2Harvest restrictions are listed for field corn harvested for grain.  Restrictions may vary for other types of corn (sweet, seed or popcorn, etc.), and corn for other uses such as forage or fodder.

Many products have specific use restrictions about the amount of active ingredient that can be applied within a period of time or the amount of sequential applications that can occur.  Please read and follow all specific use restrictions prior to fungicide use.  This information is provided only as a guide.  It is the responsibility of the pesticide applicator by law to read and follow all current label directions.  Reference to products in this publication is not intended to be an endorsement to the exclusion of others that may be similar. Persons using such products assume responsibility for their use in accordance with current directions of the manufacturer. Members or participants in the CDWG assume no liability resulting from the use of these products.

 

Conditions Favorable for Fusarium Head Blight (scab) in Wheat Again This Year

Conditions Favorable for Fusarium Head Blight (scab) in Wheat Again This Year published on No Comments on Conditions Favorable for Fusarium Head Blight (scab) in Wheat Again This Year

Trey Price, Field Crop Pathology, Macon Ridge Research Station;

Boyd Padgett, Central Region Director, Dean Lee Research and Extension Center

Last year Louisiana wheat was devastated by Fusarium head blight (scab) because of warm and wet weather conditions during flowering.  Weather conditions are currently favorable for wheat scab development statewide.  Most of the wheat in the state is at or very near flowering, which is the most susceptible stage to scab infections.  Wheat in southernmost production regions is already showing early signs of scab infection.

The disease is mainly caused by the fungus, Fusarium graminearum, which also causes ear, stalk, and root rots in corn. Symptoms of the disease will first appear 10 to 14 days after flowering as bleached heads which will be noticeable from the turn row (Photo 1).  This symptom is often mistaken with the appearance of maturing wheat.  Upon closer inspection, affected wheat heads will usually have infected kernels showing the characteristic bleached appearance with pinkish/salmon/light orange coloration along the glumes (Photo 2).  This coloration is millions of microscopic spores (reproductive structures) of the fungal pathogen.  There are usually healthy kernels along with the diseased kernels on the same head (Photo 3).  In extreme cases, however, the entire head may be infected.  At harvest, affected seed will be shriveled, off color, and much lighter than healthy kernels and are referred to as “tombstones” (Photo 4).

Photo 1. A view of a field heavily-infected with FHB.
Photo 1. A view of a field heavily-infected with FHB.
Photo 2. Closer view of a head infected with FHB. Note the salmon-colored fungal growth near the center.
Photo 2. Closer view of a head infected with FHB. Note the salmon-colored fungal growth near the center.
Photo 3. Wheat heads with FHB-affected and healthy kernels.
Photo 3. Wheat heads with FHB-affected and healthy kernels.
Photo 4. Diseased kernels (left) vs. relatively healthy kernels (right).
Photo 4. Diseased kernels (left) vs. relatively healthy kernels (right).

The pathogen over summers on corn, wheat, small grain residue, and other grasses.  With that in mind, there are some cultural practices that may aid in management:  crop rotation, tillage, mowing/shredding, or staggered planting/varietal maturity.  At harvest, combine fan speed may be increased to remove infected seed, which is lighter than healthy seed.  Additionally, seed cleaning equipment may help remove affected seed but may not be cost effective.  These cultural practices alone will not completely manage FHB.  An integrated approach is required to lessen the impact of FHB.

Triazole fungicides may be somewhat effective on FHB.  Some earlier research indicated that tebuconazole (Folicur and generics) may reduce incidence and severity of FHB.  Later research has shown that Prosaro (prothioconazole + tebuconazole), Proline (prothioconazole), and Caramba (metconazole) are most efficacious on FHB.  THESE APPLICATIONS WERE MADE UNDER IDEAL CONDITIONS WITH IDEAL TIMINGS AND THE MAXIMUM CONTROL WAS AROUND 50%.  AVERAGE CONTROL WAS ABOUT 40%.

Timing is critical.  We have a very short window during flowering to make an effective application for FHB.  The biggest problem is that ideal conditions (wet weather) for FHB infection are not ideal for making fungicide applications.  Head coverage also is critical.  Sprayers should be calibrated to deliver maximum water volume (minimum 15 GPA by ground, 5 GPA by air) and optimal droplet size (300 to 350 microns).  For ground sprayers, nozzles angled at 30° to the horizontal will maximize head coverage.  Some research has shown that dual nozzles angled in opposite directions will also increase head coverage.

It is common to see 2-3 years of epidemics of FHB followed by years with little to no disease.  Judging by the amount of scab we saw last year and current weather conditions, the probability is high for another severe epidemic.  An online (www.wheatscab.psu.edu) risk assessment tool that is based on temperature and relative humidity is available online, which has regional commentary that will help you to determine your risk at a given location.

For more information, please see the following resources:

www.scabsmart.org

www.scabusa.org

http://www.mississippi-crops.com/2015/04/24/wheat-disease-update-april-24-2015/

Wheat Variety Performance and Production Practices in Louisiana

Wheat Variety Performance and Production Practices in Louisiana published on No Comments on Wheat Variety Performance and Production Practices in Louisiana

Please see the link below by Drs. Steve Harrison, Boyd Padget and Trey Price.

2015 Wheat Update

Reports of Fusarium Head Blight of Wheat (Scab) Statewide

Reports of Fusarium Head Blight of Wheat (Scab) Statewide published on No Comments on Reports of Fusarium Head Blight of Wheat (Scab) Statewide

Trey Price, Field Crop Pathology, Macon Ridge Research Station
Boyd Padgett, Small Grain Pathology, Dean Lee Research and Extension Center

Over the past two weeks there have been multiple reports from producers and consultants throughout Louisiana of wheat scab, also known as Fusarium head blight (FHB). Reported incidences have ranged from 10 to 20 percent. The disease is mainly caused by the fungus, Fusarium graminearum, which also causes ear, stalk, and root rots in corn.

Symptoms of the disease will first appear 10 to 14 days after flowering as bleached heads which will be noticeable from the turn row (Photo 1). This symptom is often mistaken with the appearance of maturing wheat. Upon closer inspection, affected wheat heads will usually have infected kernels showing the characteristic bleached appearance with pinkish/salmon/orangish coloration along the glumes (Photo 2). This coloration is millions of microscopic spores (reproductive structures) of the fungal pathogen. There are usually healthy kernels along with the diseased kernels on the same head (Photo 3). In extreme cases, however, the entire head may be infected. At harvest, affected seed will be shriveled, off color, and much lighter than healthy kernels and are referred to as “tombstones” (Photo 4).

Photo 1.  A view of a field heavily-infected with FHB.
Photo 1. A view of a field heavily-infected with FHB.
Photo 2.  Closer view of a head infected with FHB.  Note the salmon-colored fungal growth near the center.
Photo 2. Closer view of a head infected with FHB. Note the salmon-colored fungal growth near the center.
Photo 3.  Wheat heads with FHB-affected and healthy kernels.
Photo 3. Wheat heads with FHB-affected and healthy kernels.
Photo 4.  Diseased kernels (left) vs. relatively healthy kernels (right).
Photo 4. Diseased kernels (left) vs. relatively healthy kernels (right).

 

Since 1996, outbreaks of FHB have been as variable as the weather. Outbreaks have been reported in the Great Plains, Central U. S., Mid-South, and Southeast with reported losses of up to 20% and up to 80% in isolated fields. Conditions favoring development are wet, warm weather during flowering. The fungus may infect wheat from flowering to harvest with the most devastating infections occurring during flowering. This infection timing creates hurdles for managing the disease.

The pathogen oversummers corn, wheat, small grain residue, and other grasses. With that in mind, there are some cultural practices that may aid in management: crop rotation, tillage, mowing/shredding, or staggered planting/varietal maturity. At harvest, combine fan speed may be increased to remove infected seed, which is lighter than healthy seed. Additionally, seed cleaning equipment may help remove affected seed but may not be cost effective. These cultural practices alone will not completely manage FHB. An integrated approach is required to lessen the impact of FHB.

Triazole fungicides may be somewhat effective on FHB. Some of the earlier research showed that tebuconazole (Folicur and generics) may reduce incidence and severity of FHB. Later research shows that Prosaro (prothioconazole + tebuconazole), Proline (prothioconazole), and Caramba (metconazole) may be efficacious on FHB. THESE APPLICATIONS WERE MADE UNDER IDEAL CONDITIONS WITH IDEAL TIMINGS AND THE MAXIMUM CONTROL WAS AROUND 50%. AVERAGE CONTROL WAS ABOUT 40%.

Timing is critical. Essentially we have a 5 day window during flowering to make an effective application for FHB. The biggest problem is that ideal conditions (wet weather) for FHB infection are not ideal for making fungicide applications. Head coverage is also critical. Sprayers should be calibrated to deliver maximum water volume (minimum 15 GPA by ground, 5 GPA by air) and optimal droplet size (300 to 350 microns). For ground sprayers, nozzles angled at 30° to the horizontal will maximize head coverage. Some research has shown that dual nozzles angled in opposite directions will also increase head coverage.

The vast majority of fields in Louisiana are currently past the application window. Fungicide applications at this point would likely by off label and ineffective.

It is common to see 2-3 years of epidemics of FHB followed by years with little to no disease. Judging by the amount of calls and observations at this point, FHB has been more prevalent this year compared to previous years. If we have similar weather conditions next year during flowering, expect to encounter FHB again in 2016. An online (www.wheatscab.psu.edu) risk assessment tool that is based on temperature and relative humidity is available online, which has regional commentary that will help you to determine your risk at a given location next year.

For more information, please see the following resources:

www.scabusa.org
www.scabsmart.org
http://www.mississippi-crops.com/2015/04/24/wheat-disease-update-april-24-2015/
http://www.arkansas-crops.com/2015/04/23/update-management-Arkansas/#sthash.xSo0EAqt.dpuf

 

N management in wheat

N management in wheat published on No Comments on N management in wheat

Josh Lofton, Steve Harrison, and Beatrix Haggard- LSU AgCenter

As we transition from January to February and wheat begins to show spring growth, it’s time to think about applying topdress N fertilizer. Most wheat is around Feekes 5 (green-up; http://varietytesting.tamu.edu/wheat/docs/mime-5.pdf) growth stage, and it’s time to begin applying topdress N. Decisions on N fertilization rate and timing dramatically  influence final yield, and N mismanagement can certainly be a limiting factor. However, N management in wheat is not as cut and dry as it can be in other crops. This is true for not only N application rates but also application timing.

Current recommendations are to apply 90-120 lbs N ac-1 throughout the growing season, split between all applications; however, these rates can vary depending on soil type, previous crop and crop condition. That means if 15 lbs N ac-1 was applied preplant, an in-season application should be between 75 and 105 lbs N ac-1. These application rates seem fairly straight forward, but attempting to manage around changing crop conditions (lush growth or stunted) or environmental conditions can be quite challenging. The major challenge for N application in wheat comes with determining how to split N applications and when those splits should occur. Currently, splitting in-season N application into two or even three topdress applications is considered the best management practice for wheat. This is due to N loss that can occur because of volatilization, leaching or denitrification. However, the most critical time for N application to have a yield benefit is late winter or early spring just prior to jointing. An initial application after jointing will limit yield potential of the crop. Furthermore, as the wheat progresses further, the benefit of N application is minimal or non-existent (by flag leaf). Therefore, N fertilizer should be applied in two to three applications between green-up and jointing with only rescue application between jointing to beginning emergence of the flag leaf.

While determining the optimum time to apply N fertilizer may seem perplexing, let your crop help you make your decision. For late-planted or wheat that did not properly develop in the fall, earlier N application (late January) is typically needed to help stimulate tillering. These applications are not needed on more developed wheat, and early topdress N application to well-tillered and advanced wheat could result in premature spring growth and subsequent yield loss if late freezes occur. Properly developed wheat in south Louisiana should probably receive an initial N application in early February, while north Louisiana should start to apply N by mid-February. However, these are just generalizations. Watch the wheat crop for signs of rapid development during warm conditions. If splitting N applications, the second application should follow the initial application by 14-28 days, allowing the crop time to green-up from the initial application and begin rapid spring growth.

While N management during in-season applications is the primary concern, managing S and, to a lesser degree, P can be critical during these stages as well. The benefit of S applications is not as wide-spread as N applications. Deficiencies are typically found on non-clay soils with lower amounts of organic matter; however, significant response can still be found on clay-textured soils with adequate organic matter content. Similar to N, S can be lost from the soil system through leaching during heavy precipitation events. Where this is an issue, the application of initial N application with urea and ammonium sulfate will minimize S issues. Managing P issues in-season for the wheat crop can be more challenging. Even if P is adequate in the soil system, cold and wet conditions can minimize the amount of P that can be taken up by the crop. If P deficiencies are present, the application of DAP as an N source cannot only help supply N needed for in-season application but also provide available P to the growing crop until conditions return where the crop can access soil-available P.

Josh Lofton, State Wheat Specialist, LSU AgCenter, jlofton@agcenter.lsu.edu

Sulfur deficiency in a wheat crop.  Note the similarity to N deficiency but occurs in the upper canopy. (Photo courtesy of R. Weisz)
Sulfur deficiency in a wheat crop. Note the similarity to N deficiency but occurs in the upper canopy. (Photo courtesy of R. Weisz)
Phosphorous deficiency in tillering wheat crop. (Photo courtesy of R. Weisz)
Phosphorous deficiency in tillering wheat crop. (Photo courtesy of R. Weisz)

Wheat cultural management in Louisiana

Wheat cultural management in Louisiana published on 1 Comment on Wheat cultural management in Louisiana

by:

Josh Lofton and Steve Harrison, LSU AgCenter


 

As much of the state is just gearing up for harvest of corn, soybeans and grain sorghum, it is time to start preparing for the state’s wheat crop. While wheat planting is still months away, it is this early season management that begins to determine the yield potential for the upcoming season.

Variety selection:

Choosing varieties for the upcoming season is potentially your most important decision prior to planting. Most producers agree that grain yield is the most important criterion for variety selection. However, there are many aspects of grain yield that need to be evaluated when selecting varieties. Two-year average yields give some indication of stability. This not only demonstrates the performance of varieties across various growing environments but also attempts to minimize environmental influence on variety performance (i.e. current year was better for early- or late-maturing varieties). Additionally, test weight is important because varieties with low test weight may result in the producer being docked at the mill.  Therefore, when evaluating variety yield performance, it is essential to use as many parameters as possible.

Heading day, plant height, lodging and disease susceptibility are also important selection criteria. Heading day allows producers to gauge relative maturity of the individual variety. Early-heading and maturing varieties permit earlier harvest and timelier planting in a double-cropping system, while later-heading varieties guard against damage from a late spring freeze and can be planted a little earlier. Early-heading varieties should be planted in the second half of the recommended planting window to avoid the likelihood of spring freeze damage. Lodging resistance helps in some years. Intense storms can occur during late grain fill and cause severe lodging, which results in lower test weight, decreased yields and lower harvest efficiency. Disease susceptibility is very important in terms of yield and profitability. It should be noted that varieties less susceptible to disease may not always produce the highest yields, especially if disease pressure is not present. However, in high disease pressure situations, the resistance may result in higher yields as well as enhanced profitability by saving the costs of fungicide applications. Therefore, managers and producers must weigh the benefits of disease susceptibility with potential yields.

Crop management:

Planting dates for Louisiana wheat depend on location and variety. For southern and central Louisiana optimum planting dates range from November 1 through November 30. The optimum planting for northern Louisiana is slightly earlier, ranging from October 15 through November 15. Early-heading varieties should generally be planted after the mid-date, while late-heading varieties can be pushed a little on the early side of the planting window. The weather in north Louisiana is cooler in the fall and early winter, which slows growth and prevents excess winter growth. It is important that the wheat crop be well-established and fully tillered before going dormant in the coldest part of the winter. Additionally, because of the cooler conditions, the threat for fall pests (Hessian fly, army worms and rust) are decreased earlier in the fall compared to south and central Louisiana. While these dates are the optimum planting window averaged over years, the timing will vary in some years depending on weather patterns. Additionally, if wheat cannot be planted within these optimum windows, planting later than the optimum window would be preferred. Early planting can result in greater insect and fall rust establishment and also makes plants more prone to spring freeze injury due to excessive fall growth and development. Planting too late (more than 14 days after the optimum window) can result in significant stand loss due to slow emergence and seed rotting and can decrease yield potential due to poor tillering and decreased canopy density.

Wheat can be planted by broadcasting seed and incorporating; however, it is preferred that the seed be drilled. Drilling the seed increases the uniformity of depth and stand. If drill seeding, wheat should be planted at a rate of 60 to 90 pounds per acre of high quality seed into a good seedbed with adequate moisture. If the seed is broadcast, seeding rates should be increased to 90 to 120 pounds of high quality seed to account for decreased germination and emergence. This higher seeding rate should be adapted for conditions in which high germination or emergence is not expected, as with late-planted wheat or heavy, wet soils. Late-planted seed should be planted at a higher seeding rate using a drill to ensure rapid, adequate and uniform emergence.

Nitrogen fertilization of wheat can be a challenging aspect of production. Total N application should normally range from 90 to 120 pounds per acre, but this will vary depending on soil type and rainfall after applications. Timing of N application depends on several factors. The wheat crop needs adequate N in the fall and early winter to establish ground cover and properly tiller; however, excessive levels of fall N can result in rank growth and increased  lodging potential, as well as a higher probability of spring freeze damage from early heading. If the wheat crop is following soybeans, soil residual or mineralizable N should be adequate for fall growth, and no pre-plant N is needed. However, if the wheat crop follows corn, sorghum, rice or cotton, the application of 15 to 20 pounds of N per acre would typically be beneficial. Where the wheat crop is planted later than optimum, additional N may be necessary to ensure adequate fall growth prior to winter conditions. If the wheat crop did not receive a fall application and appears to be suffering from N deficiency in January, the initial topdress N application can be made early to promote additional tillering. Early spring is when the majority of N for the wheat crop should be applied. There is no universal rule on how early spring N should be applied. Each field should be evaluated based on tillering, stage of development, environmental conditions and crop color. A crop that has good growth and good color should not need N fertilization prior to erect leaf sheath (Feekes 5), usually sometime in February. However, first spring fertilizer application should be applied prior to first node (Feekes 6) in order to ensure optimum head development, tiller retention and head size. Crop N stress around jointing (Feekes 6) will result in yield losses. Any additional N applied following flag leaf typically contributes very little to crop yield. Splitting topdress N into two or three applications is common in Louisiana production systems due to the increased risk of N losses often associated with heavy rainfall and our long growing season. Splitting N typically occurs by applying fertilizer N at or just prior to jointing with a second application occurring 14 to 28 days later. About 50 percent of the topdress N is normally applied with the first split, but this may be decreased if the first split is put out early and plants are not well enough developed to take up that much N.

Phosphorus, K, and micronutrients should be applied in the fall based on soil test reports. All fertilizers applied as well as lime should be incorporated into the soil prior to planting. Required lime should be applied as soon as possible because it takes time for the lime to begin to neutralize the acidity of most soils. The application of sulfur is a growing concern in Louisiana production systems, with increasing deficiencies appearing every year. Oftentimes, early spring S deficiencies are mistaken for N deficiencies and additional S is not applied. Because sulfur is mobile, similar to N, the application solely in the fall will not be adequate. Supplemental applications of S with spring N applications are often warranted.

 

For further questions or comments contact:

Josh Lofton, Wheat Extension Specialist, jlofton@agcenter.lsu.edu

Steve Harrison, Small Grain Breeder, sharrison@agcenter.lsu.edu

 

 

Winter wheat update: How recent rains will influence the wheat crop

Winter wheat update: How recent rains will influence the wheat crop published on No Comments on Winter wheat update: How recent rains will influence the wheat crop

by:

Josh Lofton- LSU AgCenter, State Wheat Specialist

Steve Harrison- LSU AgCenter, Small Grain Breeder

A recent article discussed how much potential the current wheat crop had but we may be seeing that yield potential in jeopardy due to heavy rains for the past week. One of the greatest impacts this can have on wheat seed is in the final harvest test weight. Mature wheat kernels are smooth and have the highest test weight as soon as they initially reach harvest moisture (10 – 14%). Every time a heavy rain falls on a mature wheat field the dry kernels re-absorb moisture and swell up. Upon drying again the kernel shape changes slightly and test weight is lost.  Test weight losses can reach several pounds per bushel, resulting in dockage at the elevator and decreased profitability. The article below, published by the Virginia Cooperative Extension Service, summarizes findings from NC State on the impact of delayed harvest of test weight. Hot weather during late grain fill can also negatively impact test weight, particularly for late-heading varieties. This is why some late-maturing varieties are not suitable for Louisiana, even if they do fully head out and have relatively good grain yields.

Sunken embryo.tif

 

http://www.sites.ext.vt.edu/newsletter-archive/cses/2006-06/wheattestweight.html

 

While decreased test weights may be the most common and damaging condition experienced across the state, others certainly exist. Seed diseases can also be a concern. One that has been identified in the southern part of the state by Dr. Steve Harrison is black point (Shown below).

Black tip

 

This fungus develops when humidity and temperature in the canopy are high during grain fill. While this disease can be damaging, how wide-spread these conditions become are yet to be determined. Additionally, with frequent rainfalls the seed can lose sprouting resistance and germinate in the head prior to harvest (Shown below). This not only influences seed quality but may result in significant dockage at the mill and influence harvest moisture.

sprouting

In addition the effect at the seed head level, these storms can also impact the crop at the field scale level. One common and easily identified impact is lodging in the crop. Lodging can occur when the seed head becomes too heavy and the straw deteriorates and snaps when storms occur. While most producers will be able to harvest, this high rate of lodging can increase seed deterioration and shattering prior to harvest.

Wheat lodging

While these problems may seem like a foreboding effect for the current wheat crop, there is still a large amount of potential for the crop. It will be essential to let the field and crop dry prior to recommencing harvest. However, as soon as these conditions exist, wheat harvest should be the upmost task and mechanical drying may be important. While this will not decrease damage that has already been done, it will decrease the potential of continued damage going forward.

 

For additionally questions or comments, feel free to contact:

Josh Lofton- LSU AgCenter, State Wheat Specialist, jlofton@agcenter.lsu.edu

Steve Harrison- LSU AgCenter, Small Grain Breeder, sharrison@agcenter.lsu.edu

Wheat update and transitioning into double-crop soybeans

Wheat update and transitioning into double-crop soybeans published on No Comments on Wheat update and transitioning into double-crop soybeans

By:

Josh Lofton, LSU AgCenter, Wheat Specialist and Field Crop Agronomist

Steve Harrison, LSU AgCenter, Small Grain Breeder

 

It’s the time of year where we will start to see combines rolling through wheat fields around the state. In fact, while we have been one to two weeks behind normal growth for much of the season, recent dry weather across the state has led to a rapid dry-down and, as a result, many locations in south Louisiana have already begun harvesting. Initial reports from these regions indicate yields have been very promising, with little noticeable influence from this last winter. The majority of north Louisiana has yet to begin harvest, with the majority of fields five to 15 days from beginning harvest. By the look of the crop, it can be expected that yield will potentially be as promising as those being seen in south Louisiana.

As the wheat crop is beginning to wind down, many producers across the state will begin to look toward the successive crop. For a majority of these wheat acres, this will be double-crop soybeans. One of the most important stages in double-crop production systems is the transition from the winter crop to the summer crop. To optimize the soybean yields, a quick and efficient transition is critical. One aspect that will influence this transition is wheat residue management. While most managers will want to manage the residue in a similar manner between years and locations, it is essential that residue management decisions be made individually. The two most commonly used management options for wheat residue management are no-tillage into standing wheat residue and no-tillage into burned wheat stubble. While burning of wheat residue has received substantial negative publicity in recent years, there are conditions and circumstances where it has the potential to be the best management decision. When deciding which management practice to use for each individual system, managers should look at the current growing conditions and previous typical conditions. The recent dry conditions have aided in wheat dry-down. However, it may have detrimental impacts on the successive soybean crop. While these dry conditions will be detrimental in different residue management conditions, these conditions are amplified when the wheat residue is burned ahead of the soybean planting. Therefore, if soils are dry, caution should be used if wheat residue burning is intended. Additionally, while the chance of precipitation in the latter part of the week is always in flux, if wet conditions return, this will also influence management. No-tillage into standing wet wheat stubble can negatively influence planting practices and could result in delayed or poor soybean stands. However, wet wheat stubble will burn inconsistently and potentially, again, negatively influence stand and emergence.

While we have a potentially very productive wheat crop finishing, producers and managers in double-crop systems must already be thinking toward the successive soybean crop. While these double-crop systems can be very productive and profitable, increased management is essential, and residue management is one of the most critical issues.

Wheat continuing to grow with colder weather near

Wheat continuing to grow with colder weather near published on No Comments on Wheat continuing to grow with colder weather near

by:

Josh Lofton, LSU AgCenter, Field Crop Agronomist and Wheat Specialist

Steve Harrison, LSU AgCenter, Wheat Breeder

In recent weeks, the wheat crop has experienced near optimum growing conditions across much of the state. This has allowed the wheat crop to develop rapidly, although the crop is still late in heading this spring. The return of cool weather will slow wheat development over the next week, and record-breaking low temperatures are expected for the state, especially in north Louisiana. With the impact of last season’s late freeze still fresh in our minds, it is understandable that many producers and managers are concerned with the colder weather. While the wheat crop has survived one of the coldest winters on record, much of the wheat crop in Louisiana is near the most cold-sensitive growth stage. As with the previous freezes, determining the growth stage of the wheat crop will be critical to determine how much potential damage can be expected should a freeze occur. Wheat still in the tillering to booting growth stages is relatively cold-tolerant and can withstand temperatures around 26 degrees F because the grain head is still relatively protected. Wheat is most sensitive to cold weather in the heading to flowering stages of development. As the crop further progresses to milk, soft dough and hard dough stages, the crop once again gains a degree of colder tolerance. During these cold-tolerant stages, the crop can sustain temperatures as low as 28 degrees F for up to two hours before critical damage can be expected. Wheat in the flowering stage can sustain significant damage with temperatures at or slightly below 30 degrees F for just a few hours, primarily due to sterilization of the pollen and resulting failure to set seed.

weather damage to wheat at different growth states

It is important to understand the damage that can occur with these lower temperatures at these advanced growth stages. Oftentimes, because the reproductive components are exposed, cold damage at these stages can often result in substantial yield reductions. Symptoms experienced at these stages are often associated with aborted kernel production with white, bleached seed heads.

Fortunately, for grower and managers across the state, temperatures are not expected to fall below freezing, and damage should be minimal and limited to cold packets of air. Temperatures are expected to return into the 70s and 80s for the remainder of the week, and the wheat crop should quickly recommence growth and continue to progress.

wheat head damage

 

Wheat that has sustained frost/freeze damage can be noted by bleached or white seed heads.

It can be expected that when this colder weather passes and warmer conditions return, the winter wheat crop will quickly recommence growth. In doing so, most of the wheat across the state will be near or past the flowering growth stage. It is critical to note that fungicides can be applied up to Feekes 10.1 or heading but cannot be applied once the wheat crop reaches Feekes 10.5 or flowering. Any applications at or beyond this stage are considered off-label.

 

For any further questions, concerns or comments, please contact:

Josh Lofton, 318-498-1934, jlofton@agcenter.lsu.edu

Steve Harrison, SHarrison@agcenter.lsu.edu

 

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