All posts by Larry Steckel, Extension Weed Specialist

Results of the 2019 Palmer amaranth Dicamba Screen

Response of Palmer amaranth to 0.5 lbs/A of Dicamba: 2001 collected seed Left and 2019 collected seed Right. 11 days after application

In 2019 we ran calls on about 40 fields where producers were disappointed with their Palmer amaranth control from applications of Engenia or XtendiMax. We collected Palmer amaranth seed last fall from 22 of these fields where it looked like the Palmer had survived timely application(s) of dicamba. Subsequently, we were able to get a critical mass of seed to germinate from 12 of these collections in order to evaluate plants for possible dicamba tolerance in three separate greenhouse screens conducted throughout the winter months. Continue reading


New Thoughts on Pre-Emergence Options in Cotton

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Goosegrass Escapes after two applications of Roundup PM + Engenia

Clearly, after all the struggles in 2019 controlling grass weeds, many are looking to change their weed management program. The most frequent question recently has been on the best pre emergent (PRE) options to more account for barnyardgrass, jungle rice and goosegrass. Continue reading


New Thoughts on Burndown Strategy

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Junglerice escaping glyphosate plus dicamba burndown in Titpon county TN 2019

For the last two decades dicamba has been used extensively as a pre plant burndown on almost all Tennessee cotton and soybean acres. It was often used at 8 to 12 oz/A of a Clarity-type product 14 days before planting. I know it has become tradition to use it in this fashion, but I believe this should be changed for three reasons. Continue reading


Upcoming Events

January 24, 2020 – Gibson County Extension Crop Production (Ed Jones Agri-plex) 8:00 a.m. – 2:45 p.m.  (Contact Philip Shelby for details)

January 30-31, 2020 – Cotton & Rice No-Till Conference (Memphis, TN)

February 3, 2020 – Henry County Extension Crop Production (Henry Co. Fairgrounds) 6 – 9 p.m. (Contact Ranson Goodman for details)

February 4, 2020 – Middle Tennessee Grain Conference (UT Space Institute in Tullahoma, TN)

February 6, 2020 – West Tennessee Grain and Soybean Conference (Dyer Co. Fairgounds, Dyersburg, TN)

February 7, 2020 – KY/TN Grain Conference (Russellville, KY)

February 11, 2020 – Haywood/Madison Extension Crop Production (Samuel T. Bryant Distillery, Jackson, TN) 9AM-12PM (Contact Jake Mallard or Lindsay Stephenson for details)

February 12, 2020 – Tennessee Agricultural Production Association Winter Agronomic Workshop (DoubleTree Hotel, Jackson, Tennessee) 8 AM – 4 PM

February 13, 2020 – Cotton Focus (West Tennessee Research and Education Center, Jackson, TN) 8 AM-12PM (lunch provided, pre-registration is not required)


Tennessee Certified Pesticide Applicator Recertification, Dicamba and Paraquat Training in 2020.

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Tennessee Certified Pesticide Applicators must take recertification training in 2020. The recertification training is good for three years. In addition, those who will be spraying Engenia, Tavium, FeXapam or XtendiMax on Xtend crops must take dicamba training in 2020. A new addition from the EPA will be the requirement that anyone who purchases, mixes or applies a paraquat-containing herbicide to take the “How to Safely Use and Handle Paraquat-Containing Products” training module. Continue reading


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.

 


Reports of Palmer Amaranth Escapes in Xtend Crops Continue to Mount

(Picture 2) Xtend soybeans wrapped Up with Palmer amaranth that escaped Engenia + Roundup PM + Warrant
(Picture 1) Shortened branch 2nd from right was original apical meristem…. It was 4″ tall and never re-grew after Engenia applicaton

I was thinking it might be 2021 or at least 2020 before we would start getting reports of Xtend soybean fields that were wrapped up with Palmer amaranth.  Wrong! It is 2019. I visited several soybean fields this week where, judging by the Palmer amaranth regrowth, Engenia had been applied to Palmer that was 2 to 6″ tall (Picture 1). A small percentage died and the rest went on to over run several Xtend soybean fields (Picture 2).  In another field a follow-up Engenia application was made and it did improve the pigweed control some but the field was still far from being a success story. Continue reading