Category Archives: Wheat

Ryegrass Management in Wheat

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With all the issues with ryegrass in wheat last year many are asking if there are any better options for control. The main issue is resistance. About 10 years ago resistance to ALS-inhibiting herbicides (Broadstrike, Finesse, Osprey) started showing up and now a decade later is a very common biotype in many fields.  As a result, many moved to Axial to control ryegrass and it did a very good job for some time but in recent years ryegrass control has slipped as well.  So what are some good options now?

One of the best options to use is a pyroxasulfone-based herbicide this fall. There are three herbicides with the active ingredient pyroxasulfone in them that now have labels for wheat in Tennessee.  The three herbicides are Anthem Flex (pyroxasulfone + Aim), Fierce (pyroxasulfone + Valor) and Zidua (pyroxasulfone). In our research, all have provided very effective control of ryegrass.

Of course it would be too easy if they all had the same label directions in wheat but they differ a good bit.  Many of those differences go to best management practices to avoid wheat injury. Here are some particulars:

Anthem Flex can be applied from PRE-emergence to early POST (3 tillers).  The going rate would be 2.8 to 3 oz/A.  The 2.8 oz/A rate provides 1.5 ozs of pyroxasulfone. Do not apply to coarse textured soils as the probability for loss of wheat stand is increased greatly. Do not apply on broadcast wheat due to increased potential for crop response. Plant in to good moisture and avoid spraying prior to a rainfall event during germination. In other words, if wheat is to be planted and there is a good chance of rain in the next two days, then go to ”Plan B” and apply it POST to avoid potential injury.  The POST application should be applied up to 3 tillers of growth  with 3 oz/A of metribuzin to clean up any emerged weeds.

Fierce can be applied up to 14 days before planting.  A glance at the label would suggest it can be applied to wheat at a rate up to 3.0 oz/A. The 3 oz/A rate is not recommended in Tennessee. Research conducted in Georgia, North Carolina and Tennessee would suggest that a rate of 1.5 oz/A of Fierce has provided good weed control and greatly tamped down potential wheat injury. Other recommendations to avoid loss of wheat stand with Fierce is to plant wheat no-till at least 1” deep.

Zidua is labeled as a “delayed” PRE application for control of ryegrass. The definition of delayed PRE historically has varied but in Zidua’s case if the wheat has a ½” shoot it is good to go.  In practical terms it would be 3 to 7 days after planting depending upon soil temperature and moisture. The rate of Zidua to use is 1 to 2 oz/A depending upon soil type. The trick is to apply Zidua after that ½” shoot but before most of the ryegrass or poa has emerged.  If you can hit that timing, Zidua will do a great job of controlling those weeds.

 

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Corn and Cotton Producers’ Prevented Planting Decision

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Federal crop insurance programs have a prevented planting provision that can protect producers from the financial losses and risks associated with not being able to plant the intended crop within the desired planting period. Revenue Protection, Revenue Protection with Harvest Price Exclusion, Yield Protection, and Area Risk Protection insurance policies pay indemnities if producers were unable to plant the insured crop by a designated final planting date or within any applicable late planting period due to natural causes, typically drought or excess moisture. This post highlights several components of those provisions and provides a few examples.  

Kevin Adkins, Graduate Research Assistant, Department of Agricultural and Resource Economics, University of Tennessee

**Christopher N. Boyer, Associate Professor, Department of Agricultural and Resource Economics, University of Tennessee 302-I Morgan Hall Knoxville, TN 37996 Phone: 865-974-7468 Email: cboyer3@utk.edu **Corresponding author Continue reading

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A Reminder About Armyworms

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Each year, about this time, I end up writing essentially the same article. There have been a couple of reports of armyworms in wheat. Nothing crazy but much of the wheat is still in the milk stage and would be susceptible to excessive defoliation. Occasionally, armyworms may even cut the heads, typically when populations are high. Yield loss is most likely if defoliation occurs during the milk stages, with Continue reading

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Fungicide considerations and disease identification in wheat

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While I have not heard of any reports of diseases in wheat in Tennessee, as we get closer to flag leaf it will be important to be scouting for diseases. To better guide fungicide decisions, one first needs to correctly identify what disease they are trying to manage. Resources on both disease identification and fungicide selection can be found on the new, mobile-friendly field guide at guide.utcrop.com.

Major diseases of concern include stripe rust and leaf rust of wheat. There have been reports of rust to the south, there’s still not any near Tennessee or its borders. Rust spores usually cannot survive northern winters and have to be blown in from the south each year, (see Figure 1 – wheat rust pathways from http://www.ars.usda.gov/Main/docs.htm?docid=9757 which also contains specific reports on rust in wheat).

Figure 1. Wheat rust pathways in the U.S.

Stripe rust (caused by the fungus Puccinia striiformis) has a cooler, optimal temperature range (50 to 64 °F) and intermittent rain or dew promotes infection and disease development. Stripe rust is best identified by tiny, yellow to bright orange pustules that form distinct stripes on the leaves (Image 1 and 3).

 

Image 1 – Usual symptoms of stripe rust on wheat

Leaf rust (caused by the fungus Puccinia triticina) has a warmer, optimal temperature range (64 to 77 °F) along with high humidity or moisture to promote infection and disease development. Symptoms of leaf rust include small round or oblong raised pustules that are orange red in color. Leaf rust pustules are more scattered and larger in size compared to stripe rust (Image 2 and 3).

 

Image 2. Orange pustules of leaf rust
Image 3. Leaf rust pustules on left are darker orange and larger than the stripe rust pustules which are arranged in a line on right side of leaf.

Two other common diseases observed in Tennessee include septoria leaf blotch (Septoria tritici) and stagonospora leaf/glume blotch (Stagonospora nodorum). The leaf lesions look very similar and usually begin in the lower canopy and progress upward, with the latter disease also causing discoloration on the glumes (Image 4 and 5). Some injury, such as fertilizer burn or freeze damage on the leaves, can look very similar to these diseases. Noticing where in the canopy the symptoms are seen and if they are progressing will help distinguish injury from disease. More information on these diseases and others can be found at guide.utcrop.com as well as at UTcrops.com.

Image 4. Septoria-Stagnospora leaf blotch
Image 5. Glume blotch

The decision to apply a fungicide to wheat should be based upon multiple factors including: 1) disease presence, 2) fertility and yield potential, 3) weather conditions and 4) cropping history. A detailed foliar fungicide point system can be found at UTcrops.com (Wheat Foliar Fungicide Point System) that can be used as a guide to determine the need for a fungicide application.

Fungicide applications in wheat are most beneficial after the flag leaf has emerged (Feekes 9 or later growth stage), since the flag leaf can make up approximately 75% of the leaf area that contributes to grain fill. Fungicide application can be delayed further if no disease is present and/or there is low disease risk.

The next crucial time period for fungicide application is beginning bloom (Feekes 10.5.1) to protect from Fusarium Head Blight (Head Scab). Consult the Fusarium Head Blight Prediction Center at http://www.wheatscab.psu.edu/ for Head Scab forecasts for your area and the “Wheat Fungicide Table” at UTcrops.com for more information on fungicide products and their efficacy against different wheat diseases. Additional information on wheat can be found at UTcrops.com and on the Wheat Quick Facts – http://news.utcrops.com/wp-content/uploads/2015/10/W321_2015.pdf

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2017/2018 County Standard Wheat Trials

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2018 County Standardized Trials (CST) wheat harvest data are now available.  Our county trial yields were consistent with yields in much of the state, down around 15 bu from what we had last year.  Late planting due to excess moisture and a cool, wet spring with delayed fertilizer and insecticide applications, didn’t get this crop set up for record year.

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