Category Archives: Weeds

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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Reminder – Soybean Scout School This Week (7/17) in Dyersburg

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UT’s Soybean Scout Schools will be held in July (see below). These field-side programs cover the basics of soybean growth, scouting, pest identification, and general management. Pesticide recertification and CCA CEU points will be available. Scout Schools are offered free of charge with sponsorship from the Tennessee Soybean Promotion Board. Registration is not required. Participants will receive a scouting notebook and a sweep net while supplies last. Continue reading

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Control Options for Prickly Sida that has Escaped Engenia or XtendiMax and Glyphosate

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Prickly Sida and Palmer amaranth escaping 22 oz of XtendiMax and 32 oz Roundup PM picture taken 28 DAA

There have been a good number of calls reporting poor prickly sida (teaweed) control with Engenia or XtendiMax tankmixed with Roundup PM.  I have seen prickly sida escape dicamba tankmixed with glyphosate in some research here at the station as well.   This appears to have been a building problem as I recall similar, though fewer, calls last year.  The lack of prickly sida control in the Xtend system has been building a seed bank that is apparently showing up in many fields this year. Continue reading

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New Tactics Needed in Managing Weeds in Xtend Crops

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Palmer amaranth recovering 20 days after 12.8 oz Engenia and 32 oz Roundup PM

After more questions this past week on follow-up applications to remove Palmer amaranth, junglerice and goosegrass in Xtend crops it occurred to me we need a new thought process on weed management  with this technology. Roundup Ready soybeans came out in 1996 and cotton in 1998.  If we look back at the first three years with that technology, glyphosate was controlling every weed no matter the weed height. That Roundup Ready performance in the early years is still the expectation with Xtend technology. It has become abundantly clear, in year three, that Engenia or XtendiMax mixed with glyphosate is not providing even close to the level of weed control that glyphosate alone did back in it’s hay day.  Continue reading

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Control Options for Palmer Amaranth that has Escaped Engenia or XtendiMax

Palmer recovering from 22 oz/A of XtendiMax applied 30 days ago

A number of folks in the past few days have asked about the best way to take out the Palmer amaranth that has lived through an Engenia or XtendiMax application. The answer depends upon the crop and if there is still time on the label to try to respray a labeled dicamba product. Continue reading

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Weed Tour: June 19, 2019

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JACKSON, Tenn. – The University of Tennessee Institute of Agriculture will host the annual Weed Tour on Wednesday, June 19 at the West Tennessee AgResearch and Education Center. The guided tour will feature 60 weed management research tests in corn, soybean and cotton.

Weed Tour runs from 9 – 11:30 a.m., with registration opening at 8:30 a.m. A light breakfast will be served. Continue reading

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