Late-Season Weed Woes (Prostko)

A few things to consider based upon my texts/e-mails/telephone calls over the last few days or so: 

1) Field corn growers should be reminded that post-harvest (if it ever stops raining in some locations) is a great time of the year to get a handle on Benghal dayflower/tropical spiderwort.  Herbicides of choice include Gramoxone (paraquat), Aim (carfentrazone) and/or 2,4-D.  Check out page 74 of the 2022 UGA Pest Control Handbook for more info and peruse this old poster (click on pics to get a better/clearer view).

https://extension.uga.edu/content/dam/extension/programs-and-services/integrated-pest-management/documents/handbooks/2022-comm-chapters/Corn.pdf

2) My preferred pre-harvest treatment for late-season morningglories and other junk in field corn is a combination of Roundup (glyphosate) + Aim (carfentrazone).  Check out page 73 of the 2022 UGA Pest Control Handbook.  This combination will not magically remove running morningglory plants from the field but it will dry them out enough to facilitate an easier harvest.

https://extension.uga.edu/content/dam/extension/programs-and-services/integrated-pest-management/documents/handbooks/2022-comm-chapters/Corn.pdf

3) Peanut growers can also use Aim for late-season morningglory dessication about 7 days prior to digging.  Check out page 224 of the 2022 UGA Pest Control Handbook.  Remember, Aim is not very effective on smallflower morningglory and will cause some cosmetic (i.e. non-yield robbing) peanut leaf injury.

https://extension.uga.edu/content/dam/extension/programs-and-services/integrated-pest-management/documents/handbooks/2022-comm-chapters/Peanut.pdf

4) Here is yet another example of the awesome power of an activated PRE herbicide from my field plots earlier today.  At 20 DAT, excellent control of Palmer amaranth with all formulations of flumioxazin.

5) I am currently in the process of updating my sections (field corn, soybean, grain sorghum, canola, English/winter pea, pearl millet, peanut, sunflowers, and sugarcane) of the UGA Pest Control Handbook for 2023. If you have any comments/suggestions or have found some errors in the 2022 edition, please let me know ASAP.  Also, I will be adding a new section for sesame for those that are interested.  

Sunflower Weed Control and Windmillgrass (Prostko)

 A few things you might find interesting:

1) Here's why Valor (flumioxazin) ain't labeled for weed control in sunflowers!

2) Lots of questions lately about windmillgrass aka fingergrass (Chloris spp.).  Could be an annual or perennial plant depending upon the species.  Supposed to be very sensitive to Roundup (glyphosate), Poast (sethoxydim), Select (clethodim), and Assure II (quizalofop) when applied from seedling to tillering stage of growth but less sensitive to these herbicides when applied at heading [Hennigh et al. 2005. Weed Science 53(3):315-322].

Windmillgrass photo courtesy of H. McLean (Syngenta).

Goosegrass (Prostko)

Dr. Culpepper recently gave you his 2 cents worth about the control of goosegrass in the most recent UGA Cotton Newsletter - July 2022 (http://www.ugacotton.com/vault/file/July-2022-Cotton-Team-Newsletter.pdf).  Thought I would add my 3 cents worth as well since my ears are also bleeding from all the phone calls.  

1) The #1 enemies of POST herbicide applications are big weeds and dry weather.  If POST graminicides (i.e. Select, Poast, Fusilade, or generics) are applied applied to large plants, they will not work.  A flowering goosegrass plant is way too big!!!

Seed-heads of common annual grasses. From left to right: goosegrass; barnyardgrass: Texas panicum; crabgrass; and crowfootgrass.

2) Check out this greenhouse data from a few years ago.  Keep in mind that herbicides are much more active in the greenhouse than in the field.  The take home message here is that rate and timing are very important.

3) Growers should expect less grass control with graminicides if applied in tank-mixes with certain fungicides or broadleaf herbicides (Cadre, 2,4-DB).  Additionally, grass control can be reduced when graminicides are applied after an application of Cadre has already occurred.  The same thing happens with Cadre/Classic/Florida beggarweed.  

 

More Tank-Mix Info/Mixing Order Problems (Prostko)

Here are a few things of interest from last week:

1) Been getting a lot of questions about the use of COC (1% v/v) vs. NIS (0.25% v/v) with Select/Clethodim 2EC on peanut.  Generally, clethodim works better when applied with a COC vs. NIS (~10-15% better on some days).  But, COC increases crop injury (see below) especially when hot/dry.  In the picture below Dyne-Amic (Helena), is a combination of methylated seed oil (soybean) + organosilicone-based NIS.  Growers who are overly concerned about peanut injury could use the other formulations of clethodim (Select Max 0.97EC, Tapout 0.97EC, Intensity One 0.97EC) that already include an adjuvant, can be used with a NIS, and are less likely to cause major leaf burn (will still get some leaf burn in this weather).  

2) Check out this tank-mix. Ouch!! Class Act NG is a NIS + AMS product (Winfield).  Praiz 6F is a generic chlorothalonil (Winfield).  Domark 1.9ME (tetraconazole), from Gowan, is labeled for early/late leaf spot, web blotch, and rust.  In my opinion, the Class Act NG was not really needed and the rate of Dual Magnum could have been reduced to 16 oz/A.  This is a great example of everyone on the planet (me included) not knowing what will happen on any given day when 6 products are tank-mixed together (especially when hot/dry).  

3) Somebody asked me about tank-mixing boron with Cadre + DB + Dual Magnum + Priaxor???  Never did it before.  See below.  Not as bad as I was anticipating but it could be very different on any given day and/or when sprayed later in the PM.  

4) Check out this picture from JK.  A huge mess.  Best we could come up with after reviewing product labels and scratching our heads was an incorrect mixing order.  Mixing order matters!!!!

 

Cobra or Ultra Blazer for Large Pigweed (Prostko)

A late night text from "The Greatest American County Agent (see below and note chest logo) prompted this blog.  For you Millennials reading this, it's a spin on an 1980's TV show called "The Greatest American Hero" (https://en.wikipedia.org/wiki/The_Greatest_American_Hero).  This is what you get when you text me at 7:42 pm (Ha Ha! But all kidding aside, I am available 24/7/365 for county agents!)

What are my thoughts about controlling large pigweed in peanuts with Cobra or Ultra Blazer?

1) I do not have a preference between Cobra or Ultra Blazer if the pigweed plants are 2"-4" tall.

2) I do prefer Cobra over Ultra Blazer when plants get bigger than that. But, I would not expect any miracles when plants get larger than 4".  For the record, labeled maximum heights for Ultra Blazer (24 oz/A) and Cobra (12.5 oz/A) are 4" tall/6 leaf and 3" tall/6 leaf, respectively.

3) If plants are too big, grower is wasting his time and money on a revenge spray.

4) Other options for controlling large pigweed include hand-weeding, mechanical cultivation, and/or using paraquat in a non-selective applicator (wiper, rope-wick, etc.).

From the Field - June 2 (Prostko)

 A few things for you to consider, fresh from the field:

1) New technologies are great but you can control weeds without it.  Nothing beats starting clean, using a strong residual herbicide (activated with moisture) at planting, followed by a timely POST (with more residual).  The Palmer amaranth population in these soybean plots is both glyphosate and ALS-resistant and was at an initial density of 40+ plants/sq. ft.  Boundary is a combination of metribuzin + s-metolachlor.

2) These peanut weed control programs have worked for me for more than 20+ years (started clean).  Once again, I have not observed any differences between Prowl or Sonalan based programs.  If you don't like Dual Magnum, you can substitute Anthem Flex, Outlook, Warrant, or Zidua.  If you don't like Cadre, use Ultra Blazer or Cobra but lower your weed control expectations, especially if nutsedge and/or sicklepod are present. 

3) Don't expect to see much much from Cadre on yellow nutsedge for at least 21 days after application.  Cadre must be absorbed by both the leaves and roots for it to be the most effective.  POST applications of Cadre in dryland peanut fields that have not gotten much rain after application will likely provide less than optimum control.

4) Tank-mixes of Basagran/Broadloom (bentazon) with Cadre will NOT improve the control of yellow nutsedge.  In fact, it could cause antagonism.

"Cracking" Time Again on Peanuts (Prostko)

Many peanut growers are in the field right now making "cracking" applications of paraquat (whether they really need it or not?).  I always get tons of questions about product use rates.  Check out these pictures from earlier today.  These are rates I have been testing for years and they work pretty much all the time (when applied to small weeds 1"-3").  Higher rates and later applications, especially in dryland fields, can push a peanut plant's paraquat tolerance to its limits.   

A few other thoughts:

1) If grower wants to use the 3 lb/gal formulation of paraquat (i.e. Helmquat or Gramoxone 3SL), the normal application rate in these tank-mixtures is 8 oz/A (0.1875 lb ai/A).

2) If a grower wants to use Basagran 4SL (bentazon) instead of Storm 4SL (bentazon + acifluorfen), I would suggest using 8 oz/A of Basagran 4SL.

3) If a grower wants to make his own Storm, I would suggest the combination of Ultra Blazer 2SL @ 16 oz/A + Basagran 4SL @ 8 oz/A.

4) I am not a huge fan of using paraquat + Dual Magnum or any other Group 15 herbicide without some Basagran or Storm to cool it down some on the peanut plant.  

5) No adjuvants are needed when Dual Magnum or Outlook are used (i.e. oil-based formulations) but NIS @ 0.25% v/v (1 qt/100 gallons) is suggested when using Anthem Flex, Warrant, or Zidua.  

6) Do I use i.e. and/or italics too much???? (probably)

Monday Musings (May 16) - Prostko

 A few things from the field earlier today:

1) When you get up early, you get to see some cool stuff!

Irrigating under the "blood" moon from last night (6:31 am)

Rainbows for breakfast!  A great omen for the rest of the week (hopefully).

2) Check out the awesome power of a PRE herbicide (activated with moisture).  These are from my grain sorghum plots.  It's 2 weeks after planting and in plots that are not weedy, there were PRE applications of various residual herbicides including one of the following: Aatrex (atrazine); Moccasin II Plus (S-metolachlor); Parallel (metolachlor); Everprex (S-metolachlor); Parallel Plus (atrazine + S-metolachlor); or Cinch ATZ (atrazine + S-metolachlor).  EPOST treatments were applied today. Not sure why growers, especially those with irrigation, are often reluctant to use a PRE??????????

3) Here's what diuron injury looks like on field corn.  It took 3 days before the symptoms started to show up.  I will let you know what happens to final yield.  

4) I am seeing some good weed control results in my soybean plots with Liberty + Enlist One (applied 19 DAP, V1 soybeans, 3-6" Palmer amaranth).

5)  Peanut growers who use Anthem Flex (carfentrazone + pyroxasulfone) in their paraquat "cracking" applications should expect to see more leaf injury (cosmetic) than when Dual Magnum, Outlook, Warrant, or Zidua are used.  Based upon previous UGA research, this injury should not reduce yields.

  

Monday Musings (May 9) - Prostko

Here are a couple of things to think about based upon recent phone calls/texts and observations from some of my current research projects.

1) If growers observe unexpected/unusual leaf injury/burn after a corn herbicide is applied, it is most likely caused by Valor sprayer contamination.  See below for what this injury looks like and how it could potentially influence corn yields. 

2) When evaluating the potential effects of Liberty on pigweed control, growers should wait at least 7 days before making a final decision on whether or not it worked.  FYI, the colder temperatures this week (< 60 F) will slow down the activity of Liberty for sure.  

3) Peanut growers will be making the decision to spray or not spray an early-postemergence (cracking) herbicide.  If the peanut field was clean at planting and a strong residual herbicide program was used (activated with moisture), it is very likely that a cracking spray will not be needed.  See below (i.e. no weeds in my standard PRE program at 12 DAP):

4) My general recommendations for early-postemergence (cracking) treatments in peanut are as follows:

a) Either paraquat (2 lb/gal) @ 12 oz/A or paraquat (3 lb/gal) @ 8 oz/A + either Storm @ 16 oz/A or Basagran @ 8 oz/A + one Group 15 herbicide [either Anthem Flex @ 3 oz/A or Dual Magnum @ 16 oz/A or Outlook @ 12.8 oz/A or Warrant @ 48 oz/A or Zidua @ 2.5 oz/A (liquid)]. 

Generally, I have no preference between the Group 15's when my suggested PRE/EPOST/POST peanut weed control programs are followed.

b) Add NIS @ 0.25 v/v when using Anthem Flex, Warrant, or Zidua.

c) If need be, growers can make their own Storm (I call it Georgia Storm), by tank-mixing Ultra Blazer (16 oz/A) + Basagran (8 oz/A). This is a slightly different rate than what is applied with current commercial Storm formulation @ 16 oz/A (equivalent to Ultra Blazer @ 11 oz/A + Basagran @ 11 oz/A).

d) Use at least 15 GPA and pressure/nozzle configurations to produce medium to coarse droplets (236-403 microns).  Medium/coarse droplets are yellow and green on this chart.

e) Excessive dust caused by dry weather and tractors driven at Warp Speed 10 will reduce the effectiveness of paraquat.  

NOTE:  Click on pictures for a better view.

Across My Plate Today (Prostko)

A couple of interesting weed science items that came across my plate today that I thought you might find helpful:  

1) A grower sent me the following picture of a Bryozoan spp. jamming up his irrigation system (pond).  I reached out to UGA's former aquatic weed specialist (Dr. Gary Burtle) for some help.  A few fun facts about Bryozoans: 1) Bryozoans are microscopic aquatic invertebrates that live in colonies; 2) their presence in ponds is an indicator of good water quality; and 3) control options include copper complexes and stocking ponds with bream (~500/acre).

*****FYI, I am not interested in becoming the new aquatic weed specialist.  My plate is already very full.  Any future calls to me about pond weeds will result in the following: 1) changing my cell phone number to an unlisted number; 2) early retirement; and/or 3) beginning a new career with normal work hours and no throne calls (i.e. Lowes).

2) At every soybean meeting I attend, you will always hear me talking about the need for Georgia farmers to strongly consider the use of metribuzin (PRE).  Metribuzin is cheap, will provide about 21 days of residual pigweed control, and is not a PPO herbicide.  Check out the following picture from some of my soybean plots earlier today.  More than 40+ Palmer amaranth plants/ft2 in the non-treated control (NTC) and ZERO plants where metribuzin was used.

  3)  Metribuzin is available as a solo product and/or as a component of numerous pre-mixes.

4) Growers who want to use metribuzin in soybean must plant a tolerant variety (page 279 of 2022 UGA Pest Control Handbook-Volume 1) and pay very close attention to planting depth (at least 1.5"), rate of application (0.25 lb ai/A), and soil organic matter/texture. 

https://extension.uga.edu/content/dam/extension/programs-and-services/integrated-pest-management/documents/handbooks/2022-comm-chapters/Soybean.pdf

Empyros™ Herbicides for Field Corn? (Prostko)

I received a few questions about "new" corn herbicides being sold by Helena® under the trade name of Empyros™.  Here is some information for you in case you get asked questions:

1) There are three different products being sold under that brand name.  I was under the impression that only the Empyros™ formulation would be sold in the south but I could be wrong on that one.

2) Last year was the first time that I had the opportunity to evaluate these specific pre-mixes.  Generally, they performed very well but I only have 1 year of data.  I just planted another test on Monday (03/28/22) to get another look. Check out these field pictures from 2021:

3) For more information, check out the product labels:

https://s3-us-west-1.amazonaws.com/agrian-cg-fs1-production/pdfs/Empyros_HAE_Label.pdf

https://s3-us-west-1.amazonaws.com/agrian-cg-fs1-production/pdfs/Empyros_Triad_HAE_Label.pdf

https://s3-us-west-1.amazonaws.com/agrian-cg-fs1-production/pdfs/Empyros_Triad_Flex_HAE_Label.pdf

4) The active ingredient, tolpyralate, is also sold under the trade name of Shieldex® 400SC from SummitAgro™USA.  After collecting multiple years of data, Shieldex® was added to the "official" field corn weed control recommendations in the 2022 UGA Pest Control Handbook Vol. 1 (page 69).  Check out this field picture from 2021:

5) A copy of the Shieldex® label:

https://s3-us-west-1.amazonaws.com/agrian-cg-fs1-production/pdfs/SHIELDEX_400SC2k_Label.pdf

6) Tolpyralate is a WSSA Group 27 herbicide (HPPD inhibitor) thus is very similar to other actives in this group such as tembotrione (Laudis®), mesotrione (Callisto®), and topramezone (Impact®).

Pigweed At Burndown? (Prostko)

I received this picture from a grower yesterday who was about to burndown with some Roundup (before looking in the field).  This field was treated with a Roundup + 2,4-D combo several weeks ago (but no residual).  Two main takeaways here:  1) always a great idea to include a residual herbicide in a preplant burndown weed control program especially when applied many weeks before planting; and 2) the very best thing a grower can put in a field is a foot.  In this scenario, Roundup would not have been a great option because of resistance.  The grower wisely switched to Gramoxone (and was also including Dual Magnum) since he will be planting field corn and soybean. 

 

Preplant Burndown Update (Prostko)

Some responses to a few common questions this week about preplant burndowns:

1)  What is the plant-back restriction for field corn following an application of 2,4-D?

Plant-back restrictions for field corn after a burndown application of 2,4-D are 7 days (16 oz/A) or 10-14 days (>16 oz/A)

2) If a grower cannot wait to plant field corn in 7-14 days after an application of 2,4-D, what other burndown options are available? 

Roundup (glyphosate) or Gramoxone** (paraquat) + Atrazine 4L (32 oz/A) is my first choice.  There are no field corn plant-back restriction for these treatments.  Check out the following picture from my burndown plots yesterday in a Tift Co. growers' field (many thanks to Justin H. and Regan V.).

3) What's the best option for controlling a failed stand of field corn?

It has been my experience that the best option for controlling a failed stand of field corn is to use Select Max 0.97EC (or other equivalent formulations) @ 6 oz/A + NIS. But, there is a for real 6 day plant-back restriction (field corn) for this treatment.  Since many of our current field corn hybrids have tolerance to both Roundup and Liberty, neither of these are great options.  Gramoxone has been too inconsistent for me to have much confidence.  FYI, it takes about 10-14 days before you really start to observe the full effects of Select Max.  

4) What is our current recommended preplant burndown program for peanut?

Roundup or Gramoxone** + Valor @ 2 oz/A + 2,4-D (1 pt/A).  An additional 2 oz/A of Valor can be applied at planting.  Peanuts can be planted anytime.

**When using Gramoxone on small grain cover crops, applications need to be made when seedheads are present.

Counter (terbufos) and Herbicide Reminders (Prostko)

Since we have so many new folks on our UGA Extension team, here is a quick follow-up to Dr. Bob K's earlier e-mail about the use (or not) of Counter with certain herbicides in field corn:

1) Why is it a bad idea to apply certain herbicides, particularly ALS herbicides and some HPPD herbicides, following an in-furrow (INFR) application of Counter in field corn?

Both the insecticide and the herbicide are metabolized (i.e. broken down into non-lethal compounds) by the mixed function oxidase enzyme (MFO) system.  Simply put then, the use of both products overloads the field corn plant's ability to metabolize the chemicals.  

2) What does corn injury from this negative interaction look like?

3) How much can corn yields be reduced?

4) Where can I get more info about herbicides that can or cannot be used following an INFR application of Counter?

a) Check out the the following information from AMVAC:

https://www.amvac.com/sites/default/files/_media/product/document/2022_Counter_Tech_Sheet.pdf

b) You should also be able find this information in 2022 Georgia Pest Control Handbook:

https://extension.uga.edu/content/dam/extension/programs-and-services/integrated-pest-management/documents/handbooks/2022-comm-chapters/Corn.pdf

Grass Herbicides for Pre-Plant Burndown?? (Culpepper and Prostko)

Thinking about using a grass herbicide such as Select Max (clethodim) for pre-plant burndown? Have you seen any data suggesting this is a wise decision?

Interestingly, there is a lot of buzz about using grass herbicides to burndown small grain cover crops and annual ryegrass because of the glyphosate price/shortage issues.  Most of the conversations also include tank-mixing the grass herbicide with either 2,4-D or dicamba and applying as a March/April burndown.

Prior to making the effort and spending a significant amount of money, it might be wise to review the grass herbicide label itself for the level of control the product potentially offers.  Additionally, you may find value in the data we generated in 2021 (Figure 1). A couple of important clarification notes regarding this research are as follows: 1) the application was made on February 28 (2021) when conditions were cooler; 2) we did not tank-mix with dicamba or 2,4-D, which could negatively influence grass control (i.e. antagonism); and 3) this is data from only one location.

When considering your burndown treatment for 2022, a significant amount of research suggests that the value of glyphosate may be at its maximum for the pre-plant burndown application if grasses are present in the field. Thus, we would encourage staying with the burndown program that you know is successful if anyway feasible. Planting into weed-free fields, with the potential lack of some postemergence herbicides this year, will be extremely important.

Once grassy weeds, as well as other broadleaf weeds are mature, Gramoxone (paraquat) + diuron + COC (cotton) or Gramoxone + Valor + 2,4-D amine + COC (peanut) are fantastic options (small grains must have seed heads). It appears, at least currently, that most of our winter weeds are maturing at a faster rate than in the past so these treatments may be very timely options.

Tillage is also a very effective option as you well know, just be cognizant implementing steps to avoid soil erosion.

Another possible negative.  If Select Max is used prior to planting field corn, the plant-back restriction would be 30 days.  The rate needed for burndown control (marginal) is much higher than the rate needed for volunteer corn control thus warrants a longer restriction.    

Enlist Soybean Variety Update for Georgia - 2022 (Prostko)

At the recent Laurens County Weed Meeting, I was asked if UGA has any information about the performance of Enlist soybean varieties.  The following is a quick summary of the yield performance of Enlist soybean varieties tested in the official UGA-OVT Tests in 2020 and 2021 (DM = Don Mario; AGS = AGSouth; MS = MorSoy; SH =Southern Harvest):

Results of the UGA-OVT soybean tests can be obtained at the following locations:

2020: https://swvt.uga.edu/content/dam/caes-subsite/statewide-variety-testing/docs/performance-trials/2020/soybean-prelim-2020-tables.pdf

2021: https://swvt.uga.edu/content/dam/caes-subsite/statewide-variety-testing/docs/performance-trials/2021/2021-soybean-prelim.pdf