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Timely Information > Posts > How to Keep Your Yields Up and Weeds Down in Wheat

Joyce Tredaway Ducar, Department of Crop, Soil, and Environmental Sciences, and Kathy Flanders, Department of Entomology and Plant Pathology,  Auburn University

06 September 2016

 

            The best yields that I ever made in wheat averaged 107 bu/acre and they were made when I did just a few things differently that I had the previous year. First, I controlled my weeds, in particular, ryegrass.  We have many options to use these days when it comes to ryegrass control.  An option that is not normally used for any crop but rice is a delayed Preemergence which is what is labeled for two products in wheat. A delayed PRE is when 80% of the wheat seed have germinated but have not broken through the ground yet. You can determine this by digging up your seeds and seeing if they have germinated or not yet and calculating the percent of the ones that you count. Two products that have a delayed PRE label for ryegrass control include Anthem Flex (Group 14,15) and Zidua (Group 15).  Early postemergence ryegrass options include Anthem Flex (Group 14 and 15), Osprey (Group 2), Powerflex (Group 2), Axial XL (Group 1), Axiom (Group 5 and 15) and Zidua (Group 15). However, Anthem Flex applied POST will not control ryegrass, only PRE.  If you have found that Osprey or Powerflex has not controlled your ryegrass in the past, most likely you have ALS-resistant ryegrass and need to go with a different group herbicide to control your ryegrass.  Hoelon used to be the old standard for ryegrass control but now over 95% of ryegrass is Hoelon-resistant. 

Axiom contains metribuzin and studies evaluating Zidua and metribuzin combinations revealed up to 99% control of Italian ryegrass throughout the season.  This image shows Zidua plus Metribuzin sprayed at the 2-leaf stage.

 

fig 1 zidua.jpg

Broadleaf weed control is something that cannot be ignored either.  Harmony Extra does a good job of controlling many broadleaf weeds in wheat (see image below) but there are some new products on the market that will work even better.  Travallas (Group 2 and 4) and Sentrallas (Group 2 and 4) are two new broadleaf herbicides that in our field trials provided excellent control of cutleaf eveningprimrose and mouseear chickweed.  Quelex is a Group 2 herbicide that can be applied to wheat from the 2-leaf to flag leaf emergence state. It covers a wide-range of broadleaf weeds such as Carolina geranium, mustards, hairy vetch, and henbit.  These three new herbicides have Section 3 federal labels and are awaiting state labels for Alabama at this time.

fig 2 Harmony.jpg

            After controlling your weeds, making timely fungicide applications helped increase my yields tremendously.  I had found that disease was bringing my yields down significantly in previous years and two timely fungicide applications at flagleaf to booting and at flowering made a huge difference.  The advantage of one of your fungicide applications is that it can be made at the same time as your postemergence herbicide application, thus reducing trips across the field.  The flowering spray is for head scab and is needed if weather conditions are favorable for spreading scab.  The Fusarium Head Blight Prediction Center provides timely information on the risk for this pathogen.

            In addition, controlling aphids was essential because every year my wheat would get barley yellow dwarf or cereal yellow dwarf (BYD/CYD), diseases caused by viruses that are spread by aphids.. Controlling the aphids at the right time minimizes the spread of the viruses.  The following recommendations apply to wheat that is planted at the recommended planting date for grain in Alabama: October 15-November 10 in north Alabama, October 15-November 15 in central Alabama, and November 15-December 1 in South Alabama.  In north Alabama, an insecticide seed treatment at the aphid rate, or a foliar spray with a pyrethroid insecticide 30 days after planting gives the best economic return.  In south Alabama, the foliar insecticide is most likely to pay off when it is applied in late winter (late January or early February).  It can be mixed with the liquid nitrogen application that is applied at this time.  In central Alabama, it may be necessary to control the aphids in fall and late winter.  If the forecast is for a warm winter, the additional effort to control aphids in the fall in central Alabama is more likely to pay off.  Seed treatments and foliar insecticides are listed in the aphid section, which begins on page _7, of the Small Grains Insect, Disease, and Weed Control Recommendations for 2016 .

There is always a risk from Hessian fly, so rotating your wheat and choosing a Hessian fly resistant variety is recommended.  In the northern half of Alabama, cereal leaf beetles may cause problems around flag leaf and after.  Scout wheat for this pest from late March through the end of April, and apply a foliar insecticide if populations exceed one cereal leaf beetle egg or larva per every two stems.  Don’t let this pest get ahead of you.  Once you see feeding damage on the leaves you may have already lost some yield.          Fertilization is the third component of a high-yielding wheat crop.  Making sure that the wheat had enough nitrogen fertilizer, especially in rainy years, was important. I would start out with 30 lb N/A in the fall but come back and side-dress with 60 lb N/A in the spring.  I always used ammonium nitrate or urea rather than liquid nitrogen for a couple of reasons. First, you lose a fair amount of Nitrogen to volatilization and as much as nitrogen costs, I wanted it all to go to the wheat. Secondly, using a granular fertilizer can be useful if it isn’t raining. It will remain on the ground until a rainfall and will not be wasted. A droughty plant won’t take in a liquid so sometimes applying liquid nitrogen can be wasted money. The main reason is the stress that the liquid nitrogen puts on the wheat plant. It causes such a yellowing on the wheat and whenever a plant is stressed, it is more susceptible to disease and insects.  


 


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