Dicamba Update (Culpepper)

Extension agents, I am optimistic that we are nearing a decision by our U.S. EPA regarding registrations for XtendiMax, Engenia, FeXapan, and Tavium and their potential uses for 2021. We certainly need to thank the EPA for the tremendous effort that they have invested in this challenging process. As I have shared several times, I am optimistic that labels will be approved for use in dicamba-tolerant cotton and soybean but I am also concerned about additional restrictions that may be added to labels challenging our farmers……….of course, that is just my guess. We will have in-depth discussions regarding this topic at our Using Pesticide Wisely training platform for 2021 and at our annual extension weed training on Dec 2………….make sure you attend! Of course, Prostko is organizing the training so send him an e-mail if you have questions or thoughts.

"New" Field Corn Herbicides for 2021 (Prostko)

In the last few weeks, I have seen some publicity about potential “new” herbicides in field corn.  In many cases, these “new” herbicides are not really new just a new pre-mix of older active ingredients.  The following table summarizes a few of these “new” field corn herbicides that growers might be asking you about for use in 2021.  FYI, none of these herbicides will appear in 2021 UGA Pest Control Handbook because I currently do not have enough data to support their widespread use.  It is the general practice of the UGA Weed Science Team to collect at least 2-3 years of solid data before a new product in "officially" recommended in the Pest Control Handbook.   

Company	Trade Name	Active Ingredients	WSSA MOA	Label
AMVAC	Sinate™	glufosinate + topramezone	10 + 27	https://s3-us-west-1.amazonaws.com/agrian-cg-fs1-production/pdfs/Sinate_Label1.pdf
	Impact Core™	topramezone + acetochlor	27 + 15	https://s3-us-west-1.amazonaws.com/agrian-cg-fs1-production/pdfs/Impact_CORE_Label.pdf
Summit Agro USA	Shieldex®	topyralate	27	https://www.summitagro-usa.com/wp-content/uploads/2019/09/SHIELDEX-400SC-Herbicide-Label.pdf
Syngenta	Acuron GT	bicyclopyrone + s-metolachlor + mesotrione + glyphosate	27 + 15 + 9	Not yet labeled

Here are few pictures of these products from my field research in 2020 (click on pictures to make them larger):

 

Late-Season Applications of Glyphosate and Weed Seed Production (Prostko)

Now that many growers are finishing up with field corn harvest, I have been getting lots of questions about the potential effects of late-season applications of glyphosate on the production of weed seed. Very glad to see that growers/agents are thinking about this issue.  Preventing weed seed-rain back into a field is a great long-term strategy for improving future weed control programs.  

Bottom line on this issue is that late-season applications of glyphosate can be very helpful in reducing weed seed production BUT ONLY IF APPLIED AT THE RIGHT TIME!  

Check out Figures 1 & 2.  You will note that glyphosate applications only reduced weed seed production when applied early.  Generally, glyphosate applications made to plants with maturing seed were not as effective and would likely be a waste of time and money.  

Many weeds in Georgia fields after corn harvest might already have maturing or mature seed.  Thus, growers (with the help of their local county extension agent) should look very closely before blindly applying glyphosate with the sole hope of reducing weed-seed rain.  

How much 2,4-DB can be applied in peanuts? (Prostko)

2,4-DB is a very popular and inexpensive peanut herbicide that is used on at least 35% of the acres in GA.  There are a few labels out there and use rates/time of application/PHI vary depending upon the specific label.  The following is a general summary of the 2,4-DB labels that I could find on the Agrian web-site (https://home.agrian.com/):

 

Product	Manufacturer	Rate/A (oz)	Time of Application	Total # Applications /Year	PHI (days)
2,4-DB 175	Winfield	16.0-28.0	No later than late bloom (90-100 DAPb)	2	60
2,4-DB 175	ACETO	16.0-28.0	No later than late bloom (90-100 DAP)	2	60
2,4-DB 200	Winfield	12.8-16.0	2-12 WAPa	2	60
2,4-DB 200	ACETO	14.4-25.6	No later than late bloom (90-100 DAP)	2	60
Butyrac 175	Albaugh	14.4-17.6	2-12 WAP	2	45-60
Butyrac 200	Albaugh	12.8-16.0	2-12 WAP	2	45-60
2,4-DB DMA 175	Drexel	14.4-17.6	2-12 WAP Do not apply later than 100 DAP	2	60
2,4-DB DMA 175	Drexel	12.8-16.0	2-12 WAP Do not apply later than 100 DAP	2	60

^aDAP = days after planting; ^bWAP = weeks after planting.

Peanut Weed Control Update - June 30 (Prostko)

Just a few comments based upon recent phone calls/texts/e-mails:

1) Be on the lookout out for pink purslane (Portulaca pilosa).  Best options for control at this time are either Ultra Blazer or Cobra (yes, these herbicides will burn peanuts). Do not spray Ultra Blazer or Cobra if peanut plants are 60-75 days old.

 

2) Select (clethodim), or Poast (sethoxydim), or Fusilade DX (fluazifop-P) for POST grass weed control? Is one better than the other? For whatever reason, many GA growers seem to prefer Select or generic Clethodim over the other grass herbicides.  What do I think?  Check out a summary of these previous peanut weed control studies:

a) Grichar, W.J.  1991.  Control of Texas panicum (Panicum texanum) and southern crabgrass (Digitaria cilaris) in peanuts (Arachis hypogaea) with postmergence herbicides.  Peanut Science 18:6-9.

    

    - EPOST applications (1-6" tall grass) of clethodim, fluazifop-P, and sethoxydim provided similar control of Texas panicum (>88% control).

    - In 1 of 2 years, control of southern crabgrass with EPOST applications of fluazifop-P was lower than with either clethodim or sethoxdim. 

b) Wilcut, J.W.  1991.  Efficacy and economics of common bermudagrass (Cynodon dactylon) control in peanut (Arachis hypogaea).  Peanut Science 18:106-109 

    - Split applications (21 days apart) of either sethoxydim (0.28 + 0.14 lb ai/A), fluazifop-P (0.19 + 0.10 lb ai/A). or clethodim (0.25 + 0.25 lb ai/A) provided at least 90% control of common bermudagrass. 

c) York, A.C., J.W. Wilcut, and W.J. Grichar.  1993.  Interaction of 2,4-DB with postemergence graminicides. Peanut Science 20:57-61.

    - At 28 DAT, clethodim provided 98% control of broadleaf signalgrass, sethoxydim provided 97% control of broadleaf signalgrass, and fluazifop-P provided 92% control of broadleaf signalgrass.

d) **Please review page 233 of 2020 UGA Pest Control Handbook for a summary of peanut grass herbicides.  

3) Check out these new pictures from my research plots taken earlier today.  I observed no differences between Sonalan or Prowl.  Also observed no differences between Anthem Flex/Dual Magnum/Outlook/Warrant/Zidua programs.  

 

4) As always, I am readily available for any formal or in-formal field visits upon request (FYI, I will be on vacation from July 11-18).  

New Liberty 24 (c) State Label to Help Georgia Cotton Farmers (Culpepper)

As a result of great team work with the Georgia Department of Agriculture and BASF, Georgia cotton farmers have a new Liberty label allowing shortened intervals between sequential Liberty applications which can improve weed control.

Research has shown understanding the time interval between sequential post applications is one of many critical components for an effective weed management system. The figure below compares 6" Palmer amaranth response to sequential Liberty applications as influenced by interval between applications. Obviously, one needs to apply Liberty when the biggest pigweed in the field is 3” for complete control and in this event a follow up application can be made when the next flush of pigweed reaches 3”. With the challenging weather during 2020, spraying all weeds at 3” or less may not be practical for some fields; thus, when pigweed is too large to kill with the first application then the second application timing is important.

DO NOT MAKE MORE THAN TWO LIBERTY APPLICATIONS in a season for resistance management purposes; follow the second Liberty application 10-12 days later with a lay-by directed application including conventional chemistry such as Diuron + MSMA + Crop Oil or Roundup + Diuron (add Envoke with lay-by if morningglory or nutsedge is an issue; check carryover restrictions)!

A few critical points from the label: 

1) One must have the following 24 (c) label in hand when making application (click on label picture to make larger); 

2) Liberty may be applied twice over-the-top of glufosinate-tolerant cotton as long as there is at least a 5 day interval between applications; 

3) Do not include tank-mix partners when making two applications less than 10 days apart. 

4) Do not apply more than 36 oz/A over-the-top of cotton per application.

Dicamba Update (Culpepper)

Yesterday, the U.S. EPA released critical information on the use of Engenia, Fexapan, and XtendiMax. The entire news release can be found at https://www.epa.gov/newsreleases/epa-offers-clarity-farmers-light-recent-court-vacatur-dicamba-registrations

Please visit the website for details; however, below are the details of the order:

“Details of the Order

EPA’s order addresses sale, distribution, and use of existing stocks of the three affected dicamba products – XtendiMax with vapor grip technology, Engenia, and FeXapan.

1. Distribution or sale by any person is generally prohibited except for ensuring proper disposal or return to the registrant.
2. Growers and commercial applicators may use existing stocks that were in their possession on June 3, 2020, the effective date of the Court decision. Such use must be consistent with the product’s previously-approved label, and may not continue after July 31, 2020.”

Cotton Weed Control Thoughts (Use only labeled products and follow all labeled directions and restrictions):

Scenario One:  Large pigweed with enough in-crop dicamba for two applications:  Spray labeled Roundup + dicamba immediately, wait 7 to 10 days and then make a second application; 12 days later run the lay-by rig with either 1) Direx + MSMA + Crop Oil if grasses are not up or 2) Roundup + Direx if grasses are up (add Envoke with lay-by if morningglory or nutsedge is a problem).

Scenario Two:  Large pigweed with enough in-crop dicamba for one application:  Spray labeled Roundup + dicamba immediately, wait 7 to 10 days and then make a Liberty tank mix application; 12 days later run the lay-by rig with either 1) Direx + MSMA + Crop Oil if grasses are not up or 2) Roundup + Direx if grasses are up (add Envoke with lay-by if morningglory or nutsedge is a problem).

Scenario Three: Large pigweed with no dicamba available. Sequential Liberty applications will be best approach although less effective than either dicamba system above. We were able to obtain a new state label for Liberty shortening intervals between sequential applications which will improve control (will be sending this information in another blog soon).

Other Thoughts:

1. Tavium registration was not revoked and therefore the herbicide is not impacted as of now.
2. The Enlist program of herbicides are following a similar path to that of Engenia, Fexapan, and XtendiMax in the court system. No one can predict the future.

In Georgia, we have all worked so hard to steward every pesticide and we should collectively be proud! However, this is a wakeup call in several ways. First, we must work together even harder generating sound science to preempt this type of situation in the future. Second, for those few growers who have down played