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.”

Weed Science Update - August 21 (Prostko)

A couple of things you might find of interest:

1) A local crop consultant recently sent me this picture of prostrate globe amaranth (Gomphrena celosioides).  I have never seen this plant before and for the record, Dr. Mark "The Czar" Czarnota (UGA-Griffin Campus) identified it for me.  It is a member of the Amaranthaceae (pigweed) plant family.  For more general information about this weed, please refer to the following link: http://wssa.net/wp-content/uploads/Gomphrena-celosioides.pdf

2) Had a peanut grower ask me if 2,4-DB applied to large sicklepod plants would have any effect on seed production.  A quick review of the literature would suggest that 2,4-DB applications made at the initial flower to peak flower stages of growth will cause significant reductions in the number of sicklepod seed produced.  However, applications before or after that time have no effect on seed production (only initial flower and peak flower seed numbers were statisicially different than the NTC-none).

Reductions in Grass Control in 2018? (Prostko)

Getting plenty of calls about perceived reductions in grass control after applications of ACC-ase inhibiting herbicides, such as Select (clethodim) or Poast (sethoxydim), have been applied.  Some folks first reaction to this "lack" of control is that we suddenly have widespread ACC-ase resistance.  When its comes to the issue of resistance, I will never say never.  But, before traveling down that bumpy road, I would like for you and your growers to consider the following:

1) Currently, only 2 grass species have been "officially" confirmed to have evolved ACC-ase resistance in Georgia including large crabgrass and Italian ryegrass. Scientific confirmation of herbicide resistance takes lots of time, manpower, and greenhouse space.

2) Labeled heights for optimum control of various common grasses with Select, including crabgrass, Texas panicum crowfootgrass, and goosegrass, are 2"- 6".  

3) The following is some data illustrating the effect of Select rate and timing on the control of goosegrass.  Please note that goosegrass control was reduced by 16-23%, depending upon rate, when applied at the 4-6 tiller stage of growth.

Figure 1.  Goosegrass control with Select applied at different rates and timings.

4) If Cadre (imazapic) was applied prior to the grass herbicide application, it is very likely that grass control will be reduced.   Research has shown that Cadre can reduce the photosynthetic rate of goosegrass which then reduces the sensitivity of the ACC-ase enzyme to clethodim (Burke and Wilcut.  2003.  Physiological basis for antagonism of clethodim by imazapic on goosegrass.  Pesticide Biochemistry & Physiology) 

5) At this time of the year, peanut plants are kinda tall (> 12").  Thus, any grass plants peaking out of the top of the peanut canopy are not likely to be adequately controlled due to size and coverage issues.

6) Before dropping the R-bomb, please double-check use rates, stages of growth, adjuvants, rain-free periods, and field history.  The threat of herbicide resistance is definitely real but it does not happen in one night.

Peanut Tank-Mix Thoughts (Prostko)

     Rain delays and/or late planting have resulted in continual inquiries about peanut herbicide + fungicide tank-mixes and their potential effects on weed control and crop injury. UGA will never be able to adequately address all concerns with 90,000+ potential tank-mixtures in peanuts.   Here is a quick review of some of the published data:

1) When 2,4-DB is tank-mixed with a postemergence graminicide, grass control can be reduced by 8% to 15% approximately 45% of the time.

2) When averaged across 5 grass species, Cadre (imazapic) + Select (clethodim) tank-mixtures provided 19% less effective grass control than Select alone.

3)  Abound (azoxystrobin), Absolute (tebuconazole + trifloxystrobin), Bravo (chlorothalonil) and Headline (pyraclostrobin) are 4 fungicides that have caused significant grass antagonism when tank-mixed with Select (~12% to 30% reductions in grass control).

4) Grass efficacy with Poast (sethoxydim) and Select has not been consistently reduced by tebuconazole (various trade names including Folicur, Orius, TriSum, Integral, Ebustar, Muscle, Tebuzol).  However, when reductions have been significant, grass control was reduced by 4% to 13% with tebuconazole mixes.

5) Palmer amaranth (PA) control was not reduced when 2,4-DB was tank-mixed with Bravo, Provost (prothioconazole + tebuconazole), Headline, or Absolute.  But, 2,4-DB is not that great on PA anyway though?

6)  Sicklepod control with 2,4-DB was reduced by 14% when applied with Abound but not with Bravo or tebuconazole.  

Tropical Spiderwort/Benghal Dayflower (TSW/BD) Control in Peanuts (Prostko)

Been getting quite a few phone calls about TSW/BD in peanuts.  This particular plant loves wet weather so I am not surprised.  Here are few thoughts to consider especially since many of you were not employed by UGA back when TSW/BD was Public Enemy #1.

1) The backbone of all TSW/BD programs has been Dual Magnum.  Over the years, Dual Magnum has provided some of the most consistent residual control of this weed.  When Culpepper, Flanders, and I were frantically searching for control strategies back in the early 2000's, Warrant and Zidua were not yet players in this game.  Warrant and Zidua have good activity on TSW/BD but I have more data/experience with Dual Magnum.  

2) Paraquat + Dual Magnum + Basagran or Storm is an excellent EPOST treatment for the control of TSW/BD, assuming the peanut field is still within the labeled paraquat application window of ~33-38 DAP.

Figure 1.  Tropical spiderwort/Benghal dayflower control with paraquat + Basagran + Dual Magnum.

3) If growers miss the paraquat application window, the best POST treatment for TSW/BD is Strongarm.  Growers who apply Strongarm POST in peanut need to pay close attention to the labeled crop rotation restrictions.   

Figure 2.  Tropical spiderwort/Benghal dayflower control with POST applied Strongarm.

Weed Science Update - May 29 (Prostko)

Yes, it has been raining every day since May 12, Valor damage (peanut) is everywhere, and growers need to apply POST treatments and cannot get in the field.  What do I think?  

1) Most areas in Georgia have received at least 4" of rain or more since May 12 (Figure 1).  This has resulted in many problems including Valor injury (no surprise) and/or the failure to get PRE herbicides applied.

Figure 1.  2018 Georgia Rainfall Totals - May 12 to May 28

2) Peanut growers who were planning on spraying Gramoxone + Storm/Basagran + Dual/Warrant/Zidua will very likely miss the ~33-38 DAP (28 DAC) labeled application window.  If they miss that window, they need to pull the trigger on something else (#3 below).  The following is some weed-free data I collected a few years ago regarding the response of GA-06G to various timings of Gramoxone + Basagran (Figure 2):

Figure 2.  GA-06G Yield Response to Gramoxone + Basagran

3) Peanut growers who have missed the Gramoxone window should consider applying the following as soon as the weather permits:

a) Cadre + 2,4-DB + Dual/Warrant/Zidua (assuming ALS-resistance is NOT present and crop rotations are acceptable) or 
b) Cobra or Ultra Blazer + 2,4-DB + Dual/Warrant/Zidua (assuming ALS resistance is present).  Check out Figure 3 for a recent picture of Ultra Blazer's effectiveness on pigweed when applied correctly (rate, timing, GPA, nozzle, speed).  I would expect the very same from Cobra.

Figure 3.  Palmer amaranth control with Ultra Blazer + 2,4-DB - 2018

c) Some peanut growers have tank-mixed Cadre + Cobra/Ultra Blazer + 2,4-DB + Dual/Warrant/Zidua and have not had any major problems.  But, I do not have a ton of data to support this 4-way mixture (1 test) but currently have another trial in the field right now to investigate.  Hope to spray that this week.  

4) Soybean growers who have run into some weather troubles might want to consider the following:

a) Avoid herbicide applications when soybeans are cracking.  For whatever reason, soybeans tend to be more sensitive to injury from herbicides during this stage of growth and current environmental conditions (i.e. wet), including residual herbicides such as Valor, Prowl, and Zidua.
b) My preference would be for POST herbicide applications in soybean to occur at the V1 stage (1 trifoliolate leaf) or later (Figure 4).

Figure 4.  V1 soybean stage of growth.  Source: Iowa State University.

c) The following would be good POST + residual weed control options for soybean fields in need:

RR soybeans: glyphosate + Reflex or Prefix or Warrant Ultra

LL soybeans: Liberty + Reflex or Dual Magnum or Warrant

Xtend soybeans:  glyphosate + Xtendimax or Engenia or Fexapan + Warrant or Dual Magnum [check current web-sites for drift reducing adjuvant (DRA) requirements]

Weed Science Update - May 18 (Prostko)

A few things based upon my telephone calls and e-mails this week:

1) Growers must not cut corners when cleaning a sprayer after Valor has been used.  Heard someone say this week that if you cut out the corners, you just go in circles.  I have discussed this tank-cleaning issue in a previous blog (June 3, 2013).

2) Field corn growers might be able to use a lay-by rig for cleaning up some messes or improving annual morningglory control.  In the past, I have talked alot about Evik (ametryn) but I have had some trouble with the formulation this year.  If a grower decides to use Evik, he/she must pre-slurry, have aggressive tank agitation, use 20 GPA, and get new product.  There have been some older and bad batches of Evik out there.  There are other lay-by options such as Gramoxone (paraquat) and Aim (carfentrazone).  Currently, I am investigating the potential for Laudis (tembotrione) to be used in a lay-by rig. 

3)  Growers who are considering using a dicamba product for pigweed or morningglory control in field corn need to be reminded that the use rate in field corn (0.25 lb ae/A) is 1/2 of the use rate in Xtend cotton/soybean (0.50 lb ae/A). Thus, it is highly unlikely that dicamba in field corn will control a large escaped pigweed plant (>3" tall).     

4) Zidua, Zidua, Zidua???????  Tons of questions about this new peanut product.  Based upon all the work I have done since 1997, I have seen no differences in performance between Dual Magnum, Warrant, and Zidua when used in our recommended peanut weed control programs.  I have also discussed this topic in a previous blog (May 23, 2017).  There might be some minor differences between these herbicides on individual weed species but these differences tend to disappear when a complete weed control program is used.  

Zidua in Peanuts (Prostko)

It appears as though the following statement on the supplemental Zidua peanut label has many people confused:

"Apply Zidua as a broadcast spray to peanut from "at-cracking" stage to first true leaf stage through beginning of pod development."

A few points to consider:

a) For whatever reason, most people do not talk about peanut stages of growth as frequently as they do with other crops such as soybean and corn.  However, there are some "official" stages of growth for peanuts (Figure 1).

Figure 1.  Peanut stages of growth (K.J. Boote.  1982.  Peanut Science 9:35-40).

a) Zidua is not labeled for PRE use in peanut for good reason.  Peanuts do not have a 2X tolerance to PRE applications.  In my research since 1997, PRE applications of 2X rates have caused peanut yield losses ranging from 7% to 25%.  The 1X rate of Zidua is 1.5-2.0 oz/A (85WG) or 2.50-3.25 oz/A (4.17SC).

b) I have applied Zidua as early as V2-V3 (10 DAP) and as late as R6 (90 DAP) with no yield loss.  However, applications made at V2-V3 did cause more peanut injury than later applications but this injury did not result in yield loss.

c) I have applied the equivalent of 8 oz/A of 85DG or 13 oz/A of 4.17SC (4X rate) at 44-51 DAP (R1 to R2 stage) with no yield loss.  Not suggesting that growers do this but this is a good indicator of the tolerance of peanuts to POST applications of Zidua.

d) **Bottom line, growers should never apply Zidua PRE and POST applications can be made from the V2 through R3 stages of growth.

Tank-Mixing (Prostko)

Tank-mixing pesticides can be rather complicated especially when numerous products will be mixed.  Here are a few questions and answers based upon some recent inquiries that I have received:

1) Can I tank-mix Prowl EC and Prowl H20?

I have never have done this in my research plots but I recently conducted a small tank-mix test (Figure 1).  With good agitation, I did not observe any problems.  Do not mix these two herbicides together before putting in water.  They should be put in spray tank (already filled with water) separately.

Figure 1.  Prowl H20 3.8ASC + Prowl 3.33EC Tank-Mix (32 oz/A of each in 15 GPA, Prowl H20 was put in 1st)

2) Can I tank-mix dry and liquid Valor formulations together in a spray tank?

I have never done this either in my research plots but I conducted another small tank-mix test (Figure 2).  With good agitation, I did not observe any problems.  Remember, it is always a good idea to pre-slurry dry formulations in water before dumping into a large spray tank.

Figure 2.  Valor SX 51WG + Valor EZ 4L Tank-Mix (3 oz/A of each in 15 GPA)

3)  When tank-mixing various pesticides, what is the correct mixing order?  

The general formulation science mixing order is as follows:

a) water soluble bags (WSB)
b) water soluble granules (WSG)
c) water dispersible granules (WG, XP, DF)
d) wettable powders (WP)
e) water based suspension concentrates/aqueous flowables (SC, F)
f) water soluble concentrates (SL)
g) suspoemulsions (SE)
h) oil-based suspension concentrates (OD)
i) emulsifiable concentrates (EC)
j) surfactants, oils, adjuvants
k) soluble fertilizers
l) drift retardants

For those Millennials out there that sleep with their cell phones taped to their head or hands, there is an app called Mix-Tank (Precision Laboratories) that you might find useful (http://www.mixtankapp.com/). There might be some other apps out there that I am not yet aware of?

4) How do I mix Reflex and Gramoxone?

a) add 1/2 of the required amount of clean water into the spray tank
b) start up and maintain tank agitation
c) add NIS
d) add Reflex
e) add Gramoxone
f) add remaining amount of clean water

5) How do I mix Atrazine and Halex GT?

a) add 1/2 of the required amount of clean water into the spray tank and start/maintain agitation
b) add AMS (**only if water quality sample indicates need)
c) add NIS
d) add atrazine (make sure atrazine is fully dispersed before adding other products)
e) add Halex GT
f) add remaining amount of clean water

Using Pesticides Wisely (UPW) – Last Opportunity for 2018 Classroom Training! (Culpepper)

Over the next few days, please communicate with your growers/applicators that the very last opportunity to attend a UPW Classroom Training will occur on April 4th in Tifton. No additional UPW classroom trainings will be added for the 2018 production season. Please have your growers/applicators RVSP to the number provided in information listed below:

Region: South Central GA
Date: April 4, 2018
Time:  9 AM
Location:  UGA Tifton Campus Conference Center
RSVP #:  229-386-3328
Address: 15 RDC Road, Tifton, GA 31793

Questions of the Week? (Prostko)

Here a few questions that I received over the last few days or so.  Thought all might benefit?

1) How do I control ryegrass prior to planting peanuts if I suspect that I might have glyphosate resistance?

Select 2EC @ 8 oz/A or Select Max 0.97EC @ 16 oz/A (or generic equivalents) + 1% v/v COC  would be a good choice for this problem.  Remember that ryegrass stage of growth is important (Figure 1) and that temperatures below 50 F can significantly reduce control.  Higher rates of paraquat (3.5-4.0 pts of 2 lb ai/gal) can also be effective but 2 applications (10-14 days apart) may be needed.    

Figure 1.  Influence of clethodim timing on ryegrass control.  

2) What is the best nozzle to use for soil applied residual herbicides?

Generally, nozzle type is not as critical with soil applied residual herbicides when compared to postemergence herbicides.  For many years, I used a flat fan nozzle (11002DG) for all my weed control trials.  Recently, I started using an AIXR11002 nozzle as my standard.  I have also applied soil residuals with a TTI-02 nozzle.  I have not observed any reductions in the performance of residual herbicides when using these larger droplet nozzles.  Check out Figure 2 for a quick look at the coverage provided by these different nozzle types.  However, I would suggest that growers refer to the nozzle manufacturer for more specific information about the potential performance of nozzles with soil residual herbicides.

Figure 2.  Spray Coverage with Various Nozzle Tips

3)  What is ACURON herbicide?

Acuron, from Syngenta, is a mixture of s-metolachlor + atrazine + mesotrione + bycyclopyrone registered for use in field corn, seed corn, silage corn, sweet corn, and yellow popcorn.  Acuron can be applied preemergence or postemergence depending upon the type of corn.  I have tested Acuron for a number of years and it is a very good product.  It would be especially useful to growers who are dealing with glyphosate, atrazine, and/or ALS resistant weeds.  But in the absence of resistance, it's very difficult to for most higher priced new herbicides to beat the cost-effectiveness of a timely postemergence application of glyphosate + atrazine + Prowl tank-mixture in Georgia.   I do not have an exact figure but I have heard that Acuron is a bit pricey?

4) What is SHIELDEX herbicide?  

Shieldex, from Summit Agro USA, contains the active ingredient topyralate.  Shieldex is labeled for postemergence use in field corn, sweet corn, and popcorn.  Shieldex has the same mode of action as several other corn herbicides such as Callisto (mesotrione), Impact (topramezone), and Laudis (tembotrione).  All of these herbicides are HPPD inhibitors (WSSA MOA #27).  There are 2 good reasons why Georgia corn farmers need not worry about this herbicide:  1) it is not yet labeled in GA; and 2) I only have 1 field trial with this product (i.e. not enough data to make a solid recommendation).   

     

Weed Science Update - February 26 (Prostko)

     Over the last several days, a few interesting things have crossed my desk.  Thought you might want to see them as well.  Figure 1 is a picture of a weed from a plantation in SW Georgia (https://plants.usda.gov/core/profile?symbol=pagl17).  Numerous yellow flowered plants are blooming at this time of year so be careful when identifying.  Figure 2 is a picture of Palmer amaranth that has already emerged somewhere in SE Georgia.  Seems too early to me but also serves as a reminder that growers should consider a residual herbicide if planting will be delayed after ground preparation.  Figure 3 is a picture of volunteer Xtend (dicamba) soybeans in winter wheat.  Not an easy weed to control since they are resistant to dicamba.  Depending upon wheat stage of growth, best bet for control might be Harmony Extra + MCPA?  Importantly, these soybeans were not STS/SR.  Figure 4 illustrates how glyphosate rate and timing are important for the control of annual ryegrass.  Assuming resistance is not an issue, I would suggest at least 48 ozs/A of glyphosate are needed.

Figure 1.  Butterweed (Packera glabella).

Figure 2.  Palmer amaranth emergence in February??

Figure 3.  Volunteer Xtend (dicamba) soybeans in wheat? 

Figure 4.  Rate and timing of glyphosate for annual ryegrass control.

Bermudagrass Burndowns (Prostko)

     During the last few weeks, I have received a few inquiries about controlling bermudagrass prior to planting various row crops.  An established stand of bermudagrass can be very difficult to manage.  When dealing with bermudagrass burndowns, glyphosate rate and time of application are crucial.  Here are a few points to consider:

1) When applying glyphosate in the spring, when is the best time of application?  Generally, later applications are more effective after the bermudagrass has greened up and is actively growing (Figure 1).

  
2) Can bermudagrass be effectively controlled with 1 application of glyphosate?  What rate of glyphosate should be used?  In previous UGA research, the most effective control of bermudagrass occurred when 3 applications of glyphosate @ 2 lb ai/A were applied (Figure 2).  Obviously, this program would have to be implemented the year before planting a spring row crop.  I hope you notice that a single application of 4 lb ai/A of glyphosate applied in May was not very effective (38% control).

3) Growers who are relying on spring applications of glyphosate only will almost certainly have to follow up in-crop with 1 or 2 applications of a postemergence grass herbicide, such as Select or Poast (only in labeled broadleaf crops), or glyphosate (only in labeled GR-crops).  Consequently, those extra herbicide costs should be included in their budget plans.  Additionally, it might take a few years of fighting before optimum bermudagrass control will be obtained.

Future Paraquat Changes (Prostko)

Paraquat is the active ingredient in several popular herbicide formulations used in Georgia (Firestorm, Gramoxone, Helmquat, and Parazone).  It has multiple uses including preplant burndown applications, early-postemergence weed control in peanut, and as a soybean harvest-aid.  Paraquat registration has been under review by the EPA and many changes will be occurring in the very near future.  The main reason for these changes is that many people have died over the years from ingesting paraquat that was improperly stored in various types of containers (cans, plastic bottles, cups, etc.)   The following table of future changes was provided to me by Syngenta (the purveyors of Gramoxone) and these dates are subject to change:  

Cold Temperatures and Herbicides (Prostko)

     Growers who have sprayed certain POST systemic herbicides (i.e. Roundup, Poast, Select) over the last 15 days are likely to observe slower and/or reduced performance due to the cold weather.  When temperatures drop below 50 F, weird things start to happen because plant growth is stalled and physiological processes such as absorption and translocation are reduced.  In the past 15 days, most areas in Georgia had 10-11 days of temperatures below freezing (Figure 1).  Those temperatures are not very herbicide friendly.  Daily low temperatures are expected to be below freezing through Saturday night (Jan 20).  Growers with ants in their pants might want to wait until Sunday or later to resume any herbicide spraying that is needed. If a grower has already made an herbicide application during this cold snap, I would suggest that he/she evaluate the situation 10-14 days after treatment and re-treat if needed and if the label permits.

Chart Source:  UGA Environmental Network, accessed 01/16/18

Weed Control in Field Pea (Prostko)

      In some areas of our state, the poultry industry is encouraging growers to plant winter field peas for use as chicken feed.  Unfortunately, the UGA Weed Science Group has limited (i.e. no data) on herbicide use in this crop.  I have put together the following table of herbicides that are labeled for use in field pea.  However, there is no UGA research data supporting crop tolerance and/or weed efficacy.   My research counterparts are in the process of setting up field trials right now in Plains and Athens.  Will let you know how they turn out. (click on chart to make it larger).  

     Other herbicides such as Valor (flumioxazin) or Tricor (metribuzin) are registered for field pea use in other states but not in Georgia.  Since these are not labeled and we have no supporting data, it would not be a good idea use these!!!!