Late-Season Options for Morningglory Control in Peanut (Prostko)

Recently, I have been in several fields and have had numerous phone calls about late-season morningglory control in peanut (Figure 1).  Here a few thoughts to consider:

1) Depending upon the anticipated digging date, 2,4-DB can be used to slow down the spread/growth of annual morningglory.  However, this treatment will not provide any real control or result in complete weed death.  For convenience, 2,4-DB could be tank-mixed with a fungicide.  The pre-harvest interval (PHI) for 2,4-DB is 45-60 days depending upon the specific product label.  Only 2 applications/year of 2,4-DB are legal in peanut.

2) Aim 2EC (carfentrazone) can be used as a harvest-aid for annual morningglory in peanut (but not smallflower) .  Please refer to page 448 of the 2013 UGA Pest Control Handbook for more info about this particular treatment.  Applications of Aim will not provide complete control of large morningglories but Aim will make the stems brittle enough to improve harvest efficiency.  ET (pyraflufen-ethyl) could also be used in a similar manner but I have less experience with ET than Aim.  Both of these herbicides will cause minor peanut leaf burn.

3)  Top-mowing can be a very effective method for removing unwanted weed-growth and improving harvest efficiency.  The top few inches of the peanut plants can be mowed just prior to harvest.  However, excessive top-mowing will severely effect the flow of the peanut vines over/through the digger.  I prefer mowing with a flail mower (vertical blades) rather than a rotary mower (horizontal blades) since the rotary mower often leaves a bunch of debris on one side of the row which can cause problems.  Top-mowing is a common practice that I use in some of my weedy research plots.




Figure 1.  Late-season morningglory in peanut.

 

Reflex/Glyphosate Compatibility Issues in Soybeans (Prostko)

Just a quick reminder that there have been a few issues regarding tank-mixtures of glyphosate and Reflex.  Generally, some K-salt formulations of glyphosate have not mixed well with Reflex.  In order to prevent incompatibility problems, please refer to the following Syngenta document:

A Few Thoughts About Peanut Tank-Mixtures (Prostko)

The wet weather has caused significant spray delays for most peanut growers.  Consequently, they are now considering tank-mixtures of any and all chemicals to reduce trips across the field.  Over the last few days, I have had numerous questions about tank-mixing Select (clethodim) with other agri-chemicals.  Here are a few things to consider:

1) Tank-mixtures of Select (or any other grass herbicide) + Cadre should be avoided due to the fact that reduced grass control will occur (Figure 1).  The grass herbicide should be sprayed first and then followed a minimum of 3 days later by the Cadre.  This antagonism is a result of the Cadre reducing the photosynthetic rate of the grass which reduces the sensitivity of the grass plant's ACCase enzyme to Select.

2) Results from an older multi-state (GA, NC, TX) research project suggested that when 2,4-DB is tank-mixed with a postemergence graminicide, grass control can be reduced 8-15% approximately 45% of the time (York et al.  1993.  Peanut Science 20:57-61).

3) For optimum grass control, it not a great idea to mix POST grass herbicides with a fungicide due to the increased potential for antagonism.  Generally, Abound, Bravo WS, Headline, and Folicur have all reduced grass control at some point when tank-mixed with POST grass herbicides.  When a grass/fungicide interaction has occurred, grass control has been reduced by as little as 3% (Poast + Bravo WS - large crabgrass) or as much as 45% (Select + Bravo WS - large crabgrass).  It all depends upon the grass species and fungicide used.  Way too many what if's and maybe's for me to remember.

4) New and seasoned county agents might benefit from reviewing the following publication: Tank-Mixing Chemicals Applied to Peanut Crops:  Are the Chemicals Compatible?
http://www.peanut.ncsu.edu/pdffiles/004993/tank_mixing_chemicals_applied_to_peanut_crops.pdf

Glyphosate and Peanut Yield (Prostko)

In the May/June 2013 issue of the Southeastern Peanut Farmer (page 16), there is an article that suggests that applying low rates of glyphosate to peanut late in the season will improve yields.  This research work is being conducted by scientists at the National Peanut Lab in Dawson.

A few years ago (2006-2007), I conducted similar research with glyphosate (Figure 1).  In my research, there was no positive benefit from applying glyphosate at 105 DAP.  In fact, peanut yields were significantly reduced by several glyphosate treatments.   Because glyphosate is not labeled for such a use in peanut and there are contradictory results regarding the benefits/risks, please encourage your growers to NOT use glyphosate for this purpose.

Figure 1.  Peanut Response to Roundup WeatherMax Applied 105 DAP in Georgia, 2006-2007.

Keep Gramoxone (Paraquat) in the Peanut Mix (Prostko)

Peanut growers need to be reminded (gently, bluntly, harshly, your choice) that Cadre is almost always better following an EPOST (cracking) application of paraquat (Figure 1).  Growers should only consider not using a cracking treatment of paraquat (+ Basagran or Storm) if weather conditions have prevented a timely application (< 28 days after peanut emergence) and/or when there is not enough weed growth to justify the application (i.e. no weeds).

Reflex Injury on Soybean (Prostko)

Many soybean growers are in the process of applying their 1st postemergence (POST) herbicide.  One of the most popular POST soybean herbicide used in Georgia is Reflex (fomesafen).  Reflex can be mixed with glyphosate (avoid K+ salt formulations of glyphosate though) and will provide both POST and residual control of Palmer amaranth.  Growers who have not used Reflex in the past need to be aware of the fact that this herbicide will cause temporary crop injury (Figure 1).  Since Reflex is a contact herbicide, the injury will only be observed on the leaves that were present at application and yield should not be affected.  Any new soybean growth should not exhibit Reflex injury symptoms.  Other PPO-inhibitor herbicides, including Cobra (lactofen) and Ultra Blazer (acifluorfen), will cause similar soybean injury symptoms.



Figure 1.  Fomesafen injury on soybean, 7 DAT, Ty Ty, GA 2013.

Valor Injury on Peanut (Prostko)

Last night, I received 1.7" of rainfall in about 1-1.5 hours.  If this type of rainfall occurred in your county, be prepared for phone calls about potential Valor injury on peanuts.  Any Valor treated peanut plants that were cracking or ~2 weeks old will likely exhibit some damage (Figures 1 and 2).  The good news is that the peanut plants will likely recover without suffering yield loss (Figure 3).  The yield results presented in Figure 3 occurred after observing significant crop injury in Figure 2 (i.e. the same test).

Figure 1.  Valor Injury on Peanut.

 

Figure 2.  Valor Injury on Peanut.

 

Figure 3.  Peanut Yield Response to Valor After Observing Significant Crop Injury -
Pooled Over 3 Cultivars (GA Green, GA-06G, GA-07W) - PE-08-09.

 

Cleaning Valor From Sprayers (Prostko)

In the last 2 weeks, I have received 2 inquiries from county agents regarding field corn injury symptoms caused by POST applications of Roundup + Atrazine (+/- Warrant).  In both cases, the symptoms resembled a "burning" or "spotting" type of injury (Figure 1).  These symptoms are not typical of Roundup + Atrazine.  Another common theme in both situations was that Valor and been recently used in the sprayer.  Historically, Valor has caused numerous headaches in regards to sprayer contamination problems even when "properly" cleaned.  I am not saying with 100% certainty that these problems were caused by Valor.  However, I am suggesting that if sprayers are not cleaned according to Valent's directions (Figure 2), weird, perhaps unexplainable, things can happen.  These types of symptoms could also be caused by Reflex, Direx, or Liberty if they were accidently included in a mixture.  


Figure 1.  Corn injury from recent application of Glyphosate + Atrazine (maybe Warrant).

Figure 2.  Valor Sprayer Cleanout Procedure (Valent)
 

Pegging Peanuts (Prostko)

Over the last few days, I have been getting quite a few phone calls about "cracking" peanuts and herbicides.  The rainy weather and warm temperatures have caused a more rapid emergence of peanuts in many fields.  Additionally, the rainy weather has prevented the timely application of residual herbicides.  Here are a few things to remember:

1) DO NOT apply Valor or Prowl to peanut fields that are cracking.  The risk of injury from these herbicides is significantly increased at this stage of growth.  Growers in this situation who intended to use Valor + Prowl (or Sonalan) need to re-adjust their herbicide programs.
2) My suggestion would be to wait a few days until the peanuts fully emerge, then apply a combination of Gramoxone SL (12 oz/A) + Storm (16 oz/A) + Dual Magnum (16 oz/A).  Yes, this combination will be very "hot" but the peanuts should recover (Figure 1).
3) In my research program, I have been very successful at controlling pigweed without Valor using a Dual-based program.  An additional application of Dual (16 oz/A) should be applied in combination with either Cadre (4 oz/A) or Cobra (12 oz/A) approximately 14-21 days after the initial Gramoxone treatment. (Figure 2).
4) When Dual is included in any POST herbicide mixture used on peanuts, additional surfactant/crop oil is NOT needed.

Figure 1.  Peanut injury caused by Gramoxone + Storm + Dual Magnum - 2 DAT.



Figure 2.  Weed control in peanuts with a Dual-based herbicide program.
 

Roundup/Atrazine Tank-Mix Problems (Prostko)

Over the last few days, I have been bombarded with questions regarding problems with Roundup + Atrazine tank-mixtures.  Some folks have observed foaming problems while others have observed sludge/precipitate problems.  Most of the complaints I have received have revolved around the use of Roundup PowerMax and Roundup WeatherMax.  I am not really sure what is going on since I have not experienced any problems this year with my own tank-mixtures (Roundup WeatherMax + Aatrex).   I do know that Atrazine can be a difficult formulation to handle since it goes directly to the bottom of the spray tank when dumped into water.  Thus, aggressive agitation with any flowable herbicide formulation is important.  After scouring the world for some help with this problem, I came across the following publication from Monsanto which might be of use to your growers:



Avoiding Mixing Issues with Paraquat! (Culpepper, York, Mclean, Faircloth)

UGA AGENTS:  Below is a newsletter that will also go out on our cotton blog shortly.  It addresses tank-mix compatibility issues with paraquat when used at burndown or right after planting in cotton.  In the pest control hand book, we recommend Crop Oil as the adjuvant of choice with these mixtures and at the time we published the book data suggested Crop Oil was the best adjuvant; however, recent research has suggested a surfactant is a better choice to reduce compatibility concerns.  Keep in mind for weed control a Crop Oil is the better choice but again for compatibility the data suggest surfactants may be less problematic.

The smart guy is going to do a jar test and find a Crop Oil that is compatible with the products he/she wants to use based on their water source!!  Also, we (UGA and Syngenta) will provide kits to address this next year and the process will be much easier with these kits as compared to information provided below.   If you (only you guys) want a kit for this year call Wilson Faircloth (Syngenta) at 229-854-0278 and he will send you one.

------------------------------------------------------------------------------------------------------------------------

During 2012, numerous tank compatibility issues occurred when mixing paraquat (Gramoxone SL 2.0 and others) with commonly used burndown or preemergence herbicides for cotton (Figure 1).  Efforts over the winter have shown that each major supplier of adjuvants (non-ionic surfactants, AMS, crop oils, etc.) has products that are effective in avoiding compatibility issues (Figure 2).  Two themes are clear from these tests: 1) use higher GPA’s such as 15 when possible, and 2) slow down and remember proper pesticide mixing procedures; such as adding half the water to the tank before adding ANY pesticide or adjuvant to the spray tank.  Due to the numerous adjuvants available, different water sources, and spray volumes, the best approach is for each grower to conduct compatibility tests prior to mixing herbicides in their spray tank.   

Methods to conduct compatibility tests when applying paraquat mixtures at 15 GPA:

1.  Place 1 quart of water in an approved clear container for pesticides.

2.  Add adjuvants: 4.7 mls or 1 teaspoon equals 0.5% v/v as recommended. Invert

10 times and evaluate.  Invert EACH time you add an adjuvant or pesticide to the container.

3.  Add 7.9 mls of Reflex, or 1.5 teaspoons (this equals 1 pt/A).

4.  Now each grower would have to decide which Reflex tank mix partner will be used such as Warrant, Direx, or Prowl.  For Warrant add 24 mls or 5 teaspoons (equal to 3 pt/A), Direx add 12 ml or 2.5 teaspoons (equal to 1.5 pt/A) or Prowl add 16 mls or 3 teaspoons (equal to 1 qt/A).

5.  Add 16 mls or 3 teaspoons of paraquat (this equals 1 qt/A).

6.  After placing products in container, place lid on container and tighten.  Invert at least 10 times and evaluate.

7.  If incompatibility is apparent, repeat the test with the addition of a compatibility agent at the

appropriate rate BEFORE adding a non-ionic surfactant.  AMS-containing adjuvants have been
effective in some cases.

8.  After compatibility testing is complete, dispose of any pesticides and containers in accordance with the

Storage and Disposal section of the labels for the herbicides used.

 

Spray Tank Mixing Order When Applying Paraquat:

1 .  Fill spray tank ½ full with clean water.

2.  Begin tank agitation and continue agitation until the tank is empty after application.

3.  High quality adjuvant(s). 

4.  Dry Formulations (WP, DF, etc.)

5.  Liquid Formulations (SC, EC, L, etc.)

6.  Paraquat

7.  Fill remainder of spray tank

 

Additional Thoughts:

1.  Using at least 15 GPA carrier volume will lesson compatibility issues; thus, the example above used 15 GPA, but if applying other volumes make appropriate changes above.

2.  Each water source should be tested as it can greatly impact compatibility.

3.  Test each adjuvant; test 2012 product and 2013 product even if it is the same name brand.

4.  Warm water will lessen compatibility issues.

5.  If compatibility problems do occur in the tank, a commercial degreaser has been shown to be an

effective cleaning agent.  Avoid exposure to pesticides while cleaning tanks.

6.  The example above uses general herbicide rates; adjust rates according to those being applied.

7.  Pesticide mixing containers can be purchased:

http://www.co2sprayers.com/results.cfm?Category=56&subcat=ALL

8.  Syringes, marked in ml, can be purchased at: http://www.fishersci.com   (just search syringes).

9.  Joint efforts are underway between Syngenta and UGA to develop and distribute an inexpensive test kit that is simple to use for 2014. 

Figure 1. Fomesafen + paraquat with an incompatible non-ionic surfactant. 

Figure 2.  Fomesafen + paraquat with a compatible non-ionic surfactant.

Glyphosate Formulations Loaded or Unloaded? (Prostko)

Should crop oil be added to Glyphosate + Atrazine tank-mixes in field corn?  This is one of the most common questions that I receive at this time of year.  Generally, my response is that if you are using a “loaded” formulation (i.e. already has adjuvants included) then there is no need for an additional adjuvant.  Which formulations of glyphosate are loaded or unloaded?  Rather than reinvent the wheel, check out the links below for additional information about the various formulations of glyphosate: 

http://www.ag.ndsu.edu/weeds/sugarbeet-files/Glyt%20RRbeets.pdf 

http://extension.psu.edu/agronomy-guide/pm/tables/table-2-4-1a 

http://www.agronomy.ksu.edu/extension/doc2053.ashx 

http://www.lsuagcenter.com/NR/rdonlyres/668FD70D-CD74-4553-99AE-55B943F6B557/89884/13Z2GlyphosateAPPENDIXA.pdf 

http://www.msuweeds.com/assets/2013WeedGuide/2013WGTable10.pdf

 

Steadfast Q and Certain Dekalb Corn Hybrids (Prostko)

Recently, it has come to my attention that a few field corn hybrids being sold in our state (DKC 64-69, DKC 62-08, and DKC 62-09) may be sensitive to certain sulfonylurea (SU) herbicides.  As you may recall, there has always been a precaution when using SU herbicides on field corn since some hybrids can be more sensitive than others.  This herbicide by hybrid interaction has been studied since the early development days (i.e. late 1980’s) of Accent (nicosulfuron) and Beacon (primisulfuron). 

A few years ago, DuPont released their Q line of SU herbicides which contain the crop safener, isoxadifen.  Isoxadifen increases the tolerance of field corn to the SU herbicides by triggering rapid herbicide metabolism.  One of the most popular field corn herbicides used in Georgia is Steadfast Q (nicosulfuron + rimsulfuron + isoxadifen).  Since Dekalb currently rates the above mentioned hybrids as being sensitive to the SU herbicides, there has been some concern about using Steadfast Q on these hybrids.  From what I have heard, the sensitivity of these corn hybrids was tested using the unsafened formulation of Steadfast (- isoxadifen) not Steadfast Q (+ isoxadifen). 

Quoting directly from an official DuPont publication, “DuPont recommends and stands behind labeled use of our products on all field-corn hybrids.”   Since DuPont has put in writing that they will support/backup the use of Steadfast Q on these hybrids, growers, dealers, and consultants should have fewer reservations about using the product.  Keep in mind that I have no UGA data to support DuPont’s claims but will be evaluating a 1X and 2X rate of Steadfast Q on DKC 64-69 this year. 

At this point, I am not aware of other field corn hybrids being planted that could be sensitive to the SU herbicides.  Pioneer corn hybrid herbicide sensitivity information is available in the following publication: https://www.pioneer.com/CMRoot/Pioneer/US/products/stewardship/2013_corn_herbicide_guide_ProdList.pdf

Since I could not quickly find a valid web-address for their publication, a copy of DeKalb’s 2013 field corn hybrid herbicide sensitivity guide has been provided in a separate e-mail or is available upon request.

 

Glyphosate Use in RR Field Corn (Prostko)

There were 2 trait events, discovered by Monsanto, that lead to the development of RR corn hybrids.  GA21 was the first event used to develop the original RR corn hybrids.  These hybrids were commercialized in 1998.  A later trait event, NK603, resulted in increased tolerance to glyphosate and the subsequent commercial release of RR2 corn hybrids in 2001. 

It has recently come to my attention that not all field corn hybrids planted in Georgia are RR2 corn hybrids.  There are some corn hybrids that contain the original RR event, including Pioneer’s new racehorse, 2023BVT.  This is very important for those of us who make public recommendations since certain formulations of glyphosate are not currently labeled for use on RR corn hybrids.   Corn growers should check with their seed salesman to determine if their planted hybrids are RR or RR2 before making a POST application of glyphosate.

Syngenta corn hybrids (Northrup King) that have the glyphosate-tolerance trait are being sold as Agrisure® GT hybrids.  The event used in these hybrids was GA21, thus they could be considered RR hybrids.  Pioneer 2023BVT has the Agrisure® GT trait. 

The following is a summary of various glyphosate products that can be used on glyphosate-tolerant corn hybrids:

Glyphosate Formulation	Manufacturer	Product  Rate/A (ozs)		RR Corn Hybrids	RR2 Corn Hybrids
		0.75 lb ae	1.12 lb ae
Buccaneer Plus	Tenkoz	32	48	Yes	Yes
Credit 41 Extra	NuFarm	32	48	Yes	Yes (?)*
Gly Star Plus	Albaugh	32	48	Yes	Yes
Gly-4 Plus	UCPA	32	48	Yes	Yes (?)*
Glyfos X-tra	Cheminova	32	48	Yes	Yes
Honcho Plus	Monsanto	32	48	No	Yes
Roundup PowerMax	Monsanto	22	32	No	Yes
Roundup WeatherMax	Monsanto	22	32	No	Yes
Touchdown HiTech	Syngenta	19	29	Yes	Yes
Touchdown Total	Syngenta	23	34	Yes	Yes

*These generic labels make no specific distinction between RR and RR2 hybrids. 

The next issue of concern is what application rate of glyphosate can legally be used on RR and RR2 corn hybrids?  Generally, RR corn hybrids can receive 2 in-crop applications of glyphosate at 0.75 lb ae/A from emergence through the V8 stage or 30” in height (whichever occurs first).  RR2 corn hybrids can receive 2 in-crop applications of 1.12 lb ae/A from emergence through V8 or 30”.  Glyphosate can also be applied on RR2 corn hybrids when the corn is 30-48” tall with drop nozzles.

There is one exception to these rules.  The labels of Syngenta’s Touchdown products make no rate/timing distinctions between RR and RR2 corn hybrids.

If this makes absolutely no sense at all to you, join the club.  I have spent numerous hours over the last week trying to determine what is legal or not.  Also, it is very likely that Monsanto will amend their glyphosate labels in the very near future to include RR corn hybrids.

Bottom line, growers need to know if their corn hybrids are RR or RR2 and they must READ their specific glyphosate label to determine if, when, and how much can be applied.

 

  

 

Zidua Labeled for Use in Soybean (Prostko)

Zidua 85WG (pyroxasulfone) recently received a registration for use in soybean.  You may recall that back on January 10, I published some information on this blog about its potential uses in field corn.  Zidua provides residual control of certain annual grass and broadleaf weeds, including Palmer amaranth (Figure 1).  Zidua can be applied PPI, PRE, or EPOST at rates ranging between 1.0 to 2.1 oz/A on coarse soil types (~$6.50/A to $13.65/A).  Zidua should NOT be applied from soybean emergence (cracking) through the unifoliolate stage of growth or unacceptable crop injury may occur. A copy of the complete supplemental soybean label can be found at the following location: http://www.cdms.net/LDat/ldAMK004.pdf

Additionally, there have been revisions to the crop rotation restrictions for Zidua.  Current crop rotation restrictions for Zidua can be viewed at the following location:
http://www.cdms.net/LDat/ldAMK003.pdf

Figure 1.  Weed Control in Soybean with Zidua 85WG @ 2 oz/A.