Yellow Nutsedge/Cadre Resistance (Prostko)

In September 2017, after doing some preliminary screening (Figure 1), we collected yellow nutsedge tubers from a peanut field that were a strong suspect for resistance to Cadre (imazapic).  We sent the tubers to BASF for further greenhouse testing and just got back the results.  Unfortunately, it looks like this population of nutsedge has developed resistance to Cadre (Figures 2 and 3).  On the positive side, it does not appear to have developed cross-resistance to Sandea/Permit (halosulfuron).  In order to protect the grower's privacy, I would prefer not to reveal the exact location of this field at this time.  

Assuming adequate funding is obtained , I will be working very closely with our new teaching/research weed scientist on the main campus in Athens, Dr. Nick Basinger, to further investigate this issue.  Dr. Basinger recently replaced Dr. Bill Vencill.  If you are already aware of or become aware of peanut fields where Cadre has been used for yellow nutsedge control with less than optimum results, please let us know so that tubers can be collected from the field.   At this point in time though, I believe that this discovery of resistance is most likely an isolated case.  

Here are a few things to consider in regards to this issue, especially how it compares to the herbicide-resistant Palmer amaranth problems that we have been dealing with since 2004:  

1) At this point in time, only 1 case of herbicide-resistance in yellow nutsedge has been officially confirmed world-wide.   In 2013-2014, researchers from Arkansas confirmed halosulfuron resistance in a yellow nutsedge population collected from a rice field.  For comparison, 61 cases of herbicide resistance in Palmer amaranth have been confirmed.  

2) In Georgia, Cadre was first commercialized for use in peanut in 1996 so it took more than 20 years for this resistance to occur in yellow nutsedge.  It took roughly 3-4 years for glyphosate resistance to evolve in Palmer amaranth after the introduction of RR soybeans (1996) and RR cotton (1997).

3) The GA problem site is a dryland field where peanuts were grown for 5 continuous years and Cadre was used every year (for economic reasons).  This is atypical of the normal crop rotation sequences used by most Georgia peanut growers.  Unlike glyphosate, Liberty and PPO herbicides, Cadre is not applied to fields on a yearly basis. 

4) Yellow nutsedge can produce a large amount of seed but seed is not the primary propagation mechanism.  Some research has shown that <1% of yellow nutsedge seeds can develop into viable seedlings.  Seed is the only propagation mechanism for Palmer amaranth.  

5) The primary mechanism of  yellow nutsedge propagation is through tubers.  In Georgia, a single yellow nutsedge plant, growing without competition in a bareground area, produced 700 tubers after 6 months of growth.    

6) The primary mechanism of yellow nutsedge tuber dispersion in fields is through normal field operations such as tillage/disking and equipment movement (i.e. human action).   

7) Foraging and soil disturbance from feral hogs has been reported to promote the long-term population maintenance of yellow nutsedge.  

8) There could be also be some slight dispersion from waterfowl that prefer yellow nutsedge tubers as a food source (i.e. ducks, geese).  However, a recently published study from Missouri reported that no intact nutsedge tubers were recovered from mallard ducks in 8 feeding trials.  In these same feeding trials, 26% of Palmer amaranth seeds were viable after feeding.

Figure 1.  Cadre and Sandea field screen on suspect resistant yellow nutsedge population in Georgia, 2017.

Figure 2.  Suspect resistant yellow nutsedge population treated with Cadre 2AS @ 32 oz/A (8X rate), 21 DAT.

Figure 3.  Susceptible yellow nutsedge population (left) and suspect resistant population (right) treated with various rates of Cadre 2AS - 28 DAT.

Auxin Training Requirements for 2019 (Culpepper)

 Agents, see information below regarding the use of Engenia, FeXapan, XtendiMax, Enlist Duo or Enlist One for 2019. This is official and approved by the Georgia Department of Agriculture. You will also be sent this information through the normal chain of command. For questions regarding UPW trainings contact me. HOWEVER, for pesticide license questions contact Dr. McCann!!!
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AUXIN TRAINING REQUIREMENTS: GEORGIA 2019

NOTICE! U.S. EPA-Industry mandated label changes to dicamba products Engenia, FeXapan, and XtendiMax are now effective for the 2019 growing season.

Engenia, FeXapan, XtendiMax

1. As mandated by federal labels, one must hold a private or commercial pesticide applicator license to purchase and use these restricted use herbicides. Use is limited to ONLY those persons holding a private or commercial applicator certification.* It is no longer permissible for non-certified applicators to apply these products under the direct supervision of the certified applicator.
2. Prior to applying these products in 2019, ALL applicators must be trained according to the federal labels. In Georgia, applicators must complete the 2019 Using Pesticides Wisely classroom training. If you attended this training in 2015, 2016, 2017, or 2018, you must re-take the training in 2019.
3. Industry applicator trainings are encouraged and beneficial; however, they will not fulfill Georgia’s requirement for auxin training.
4. Each label requires certified applicators to document application information. Forms have been designed to help with this challenge and can be found at your local UGA Extension office, from the herbicide registrant, or at http://agr.georgia.gov/24c.aspx

Enlist Duo or Enlist One

1. All persons in charge of in-crop applications (planting through harvest) of Enlist Duo or Enlist One in Enlist cotton or soybean must complete the Using Pesticides Wisely classroom training. If you attended this training in 2015, 2016, 2017 or 2018, you must re-take the training in 2019.


*For those seeking certification as a private pesticide applicator:

Initial certification to become a certified private pesticide applicator requires the completion of an interactive, online Private Applicator training program administered by University of Georgia Extension (http://extension.uga.edu/programs-services/pesticide-safety-education/private-applicators.html). The online training and testing requires a total time commitment of approximately 4-5 hours and a $25 fee. Applicants MUST be able to read and understand a label. Application of auxin herbicides carries certain inherent risks associated with off-target movement. Anyone applying them should be well-trained, have a clear understanding of the potential for off-site damage, and be able to make complex decisions on when and where these products should be applied. Applicants and their employers should carefully consider who is capable of applying these products safely before beginning the certification process.


USING PESTICIDES WISELY TRAINING DATES/TIMES/LOCATIONS WILL BE PROVIDED IN MID-JANUARY 2019

Protecting Endangered Species – U.S. EPA (Culpepper, UGA and Tommy Gray, GDA).

Agents see the information and link below regarding the new dicamba labels and buffers, provided by Region IV EPA. The web site is interesting and, I think, predicts the future for ALL pesticides in protecting endangered species.

“Please be advised, OPP has posted the additional endangered species restrictions related to dicamba on The EPA Bulletin’s Live! Two website here https://www.epa.gov/endangered-species/bulletins-live-two-view-bulletins. All states in Region 4 have been affected. Please check the website to see the affected Pesticide Limitation Use Areas in your state. The additional restrictions include the following: “In combination with the 110 foot in-field wind-directional spray drift buffer, a 57 foot omnidirectional infield buffer is required to protect federally listed threatened and endangered species. Non-sensitive areas, defined below, may be included as part of the buffer. Non-sensitive areas: The following areas may be included in the buffer distance calculation when directly adjacent to the treated field edges: 1. Roads, paved or gravel surfaces, mowed and/or managed areas adjacent to field such as rights of way. 2. Planted agricultural fields containing: corn, cotton, and soybeans. 3. Areas covered by the footprint of a building, silo, or other man made structure with walls and or roof.”

As of today, the following 6 counties in Georgia are affected by the additional 57' omni-directional buffer dicamba restrictions:  Decatur, Dooly, Floyd, Mitchell, Seminole, and Worth.  This could change in the future so it is important that the web-site be monitored on a regular basis in order to maintain compliance.

Row Pattern, Burial Depth, and Tillage Effects on Tropical Spiderwort/Benghal Dayflower (Prostko)

At the recent UGA Weed Science Agent Training on December 5, I was asked for more specific data regarding the effects of row spacing, burial depth, and tillage on tropical spiderwort/Benghal dayflower (TSW/BDF).   For those wanting to know, here you go.

1) TSW/BDF control in peanut is better with twin rows.

2) TSW/BDF emergence is significantly reduced with deeper burial depths.  No emergence of TSW/BDF occurred at a depth of ~4.8".

3) TSW/BDF control is better in conventional tillage (moldboard plow) systems.

4) TSW/BD dayflower seed viability was < 2% when buried for 36 months at a depth of 8".

Wheat Circular is Ready! (Culpepper)

The 2018/2019 wheat weed control circular is ready. For those not familiar with the circular, it is a two page laminated handout with a programs approach for controlling ryegrass and wild radish in wheat. If you would like a copy prior to it being uploaded on the UGA Weed Science web-site (www.gaweed.com) in January of 2019 do the following: Email Jenna Vance at jcsmith3@uga.edu and ask for one of the following options:

Option 1: Request laminated circulars to be mailed to you. Provide the number of circulars that you would like and provide and address to send them.
Option 2: Request a PDF version. An email response will provide the PDF as an attachment.


Vegetable weed management laminated circulars will be provided at the Vegetable conference in Savannah.

Cotton weed management laminated circulars will be delivered to you and your growers during your weed meeting. If I am not visiting your county for a weed meeting or UPW meeting then let me know and I will send them through the cotton team when they visit.

Dicamba Registration Update (Culpepper)

Agents, please refer below to last nights (Oct 31, 2018) EPA press release regarding dicamba registration for 2019 and 2020.  Additionally, MAKE SURE you attend the weed science training Prostko has set up in Tifton on December 5.  In addition to our normal training approach, we will have two special speakers coming in to talk about auxin labeling/training in GA for 2019 as well as how Extension should handle pesticide drift calls/cases.

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EPA Announces Changes To Dicamba Registration

WASHINGTON (October 31, 2018) – Today, U.S. Environmental Protection Agency (EPA) announced that it is extending the registration of dicamba for two years for “over-the-top” use (application to growing plants) to control weeds in fields for cotton and soybean plants genetically engineered to resist dicamba. This action was informed by input from and extensive collaboration between EPA, state regulators, farmers, academic researchers, pesticide manufacturers, and other stakeholders. 

“EPA understands that dicamba is a valuable pest control tool for America’s farmers,” said EPA Acting Administrator Andrew Wheeler. “By extending the registration for another two years with important new label updates that place additional restrictions on the product, we are providing certainty to all stakeholders for the upcoming growing season.”

The following label changes were made to ensure that these products can continue to be used effectively while addressing potential concerns to surrounding crops and plants:

Dicamba registration decisions for 2019-2020 growing season

·         Two-year registration (until December 20, 2020)

·         Only certified applicators may apply dicamba over the top (those working under the supervision of a certified applicator may no longer make applications) 

·         Prohibit over-the-top application of dicamba on soybeans 45 days after planting and cotton 60 days after planting

·         For cotton, limit the number of over-the-top (OTT) applications from 4 to 2 (soybeans remain at 2 OTT applications)

·         Applications will be allowed only from 1 hour after sunrise to 2 hours before sunset

·         In counties where endangered species may exist, the downwind buffer will remain at 110 feet and there will be a new 57-foot buffer around the other sides of the field (the 110-foot downwind buffer applies to all applications, not just in counties where endangered species may exist)

·         Clarify training period for 2019 and beyond, ensuring consistency across all three products

·         Enhanced tank clean out instructions for the entire system

·         Enhanced label to improve applicator awareness on the impact of low pH’s on the potential volatility of dicamba

·         Label clean up and consistency to improve compliance and enforceability

The registration for all dicamba products will automatically expire on December 20, 2020, unless EPA further extends it.  EPA has reviewed substantial amounts of new information and concluded that the continued registration of these dicamba products meets FIFRA’s registration standards. The Agency has also determined that extending these registrations with the new safety measures will not affect endangered species.

Learn more: https://www.epa.gov/ingredients-used-pesticide-products/registration-dicamba-use-genetically-engineered-crops

Do Harvest-Aid Applications of Paraquat Reduce Soybean Seed Germination? (Prostko)

Historically, glyphosate has always been a no-no for use as a harvest-aid in soybeans grown for seed because of its potential negative effects on seed germination.  But, what about paraquat?

Since I have never conducted any harvest-aid research, I would not really consider myself an "expert" on this subject.  I can only go by what I read and who I talk to (usually my weed science colleagues who work more on soybeans).  Also, hope that we can all agree that we are never too old to learn new stuff.   A few thoughts about this paraquat/soybean seed germination issue:

1) A quick review of the published literature is as follows:

a) Whigham, D.K. and E.W. Stoller.  1979.  Soybean desiccation by paraquat, glyphosate, and ametryn to accelerate harvest.  Agronomy Journal  71(4):630-633.

"Paraquat applied 4, 3, or 2 weeks before harvest did not affect soybean seed germination."

b) Cerkauskas, R.F., O.D. Dhingra, J.B. Sinclair, and S.R. Foor.  1982.  Effect of three desiccants on soybean (Glycine max) seed quality.  Weed Science 30:484-490.

"Paraquat applied at R7 stage (50% defoliation) caused 16% to 29% reductions in soybean seed germination, depending upon cultivar and seed germination test (potato dextrose agar or rolled celluose towels).

c) Ratnayake, S. and D.R. Shaw.  1992.  Effects of harvest-aid herbicides on soybean (Glycine max) seed yield and quality.  Weed Technology 6:339-344.

"Paraquat had no effect on soybean seed germination when applied at R5 (beginning seed), R6 (full seed), R7 (beginning maturity), or R8 (full maturity) stages of growth."

2) I did not realize this but the Gramoxone SL 2.0 paraquat formulation (Syngenta) has a label for use on soybeans grown for research, field trials, and seed production.  This label includes a 3 day PHI which is very different from the regular soybean harvest-aid PHI label of 15 days. Other commercial formulations of paraquat, including Firestorm (Arysta), Parazone (AMVAC) and Helmquat (HELM Agro), do not have this harvest-aid/soybean seed production use on their current labels.  

Gramoxone SL 2.0 Label (check out page 41)
https://s3-us-west-1.amazonaws.com/www.agrian.com/pdfs/Gramoxone_SL_2.0_Label1q.pdf

3) Dr. Wilson Faircloth, Syngenta's local Agronomic Services Representative, provided the following information about this subject:

“The PHI for soybean grain is set to avoid paraquat residue in grain.  The application for soybeans grown for research or seed does not allow seed to enter grain channel, these soybeans must not enter normal grain channel.  So if the question is around concerns over impact on seed germination, neither application will cause a problem with germination when applied to mature seed.”