Acuron GT For Weed Control in Field Corn (Prostko)

Syngenta recently received registration for a new postemergence field corn herbicide sold under the trade name of Acuron® GT.  Acuron® GT is very similar to Halex® GT but it contains an additional active ingredient (bicyclopyrone).  Syngenta has several similar field corn herbicides in the market and I have summarized them in Table 1.  I have only had the opportunity to evaluate Acuron® GT for 1 year (Figure 1) so I would encourage any interested GA growers to use it on a limited basis until I can get more data in 2021.  A complete copy of the Acuron® GT label can be downloaded here: https://www.syngenta-us.com/current-label/acuron_gt.   

Table 1. A comparison of Acuron, Acuron Flexi, Acuron GT, and Halex GT.

Trade Name	Active Ingredients (lbs/gal) (WSSA MOA)
	glyphosate (9)	mesotrione (27)	bicyclopyrone (27)	S-metolachlor (15)	atrazine (5)
Acuron	-	0.240	0.060	2.14	1.0
Acuron Flexi	-	0.320	0.080	2.86	-
Acuron GT	2.00	0.200	0.095	2.00	-
Halex GT	2.09	0.209	-	2.09	-

 

2021 Cotton Weed Management Circular is Ready for Agents! (Culpepper and Vance)

The cotton circular should be on-line (gaweed.com) by late February but if you would like them before then or if you would like them laminated, do the following:

E-mail 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 plus an address of where to send them.

Option 2: Request a pdf version.  An e-mail response will provide the PDF as an attachment.

Some Reminders Before Field Corn Planting (Prostko)

Based upon my 22 years of experience in Georgia, here are 3 things that I know will happen somewhere in a patch of field corn in 2021:

1) Herbicide carryover will be blamed for corn injury but low soil pH is the real problem (Figure 1). Favorable average soil test results and/or "grid-sampling" do not guarantee that there are no areas of low soil pH in a field.

2) Herbicide carry-over will be blamed for corn injury but nematodes are the real problem (Figure 2).  In my opinion, nematodes are much more of a problem than is currently perceived by many.

3) Valor (flumioxazin) injury, from either sprayer contamination (i.e. improper cleanout) or drift will occur (Figure 3).  Good news is that depending upon rate and stage of growth, field corn has some tolerance to Valor (Figures 4 and 5).

Enlist™ Soybean Variety Data – 2020 (Prostko)

UGA-OVT just recently released the results of their 2020 soybean yield trials.  In those trials, several Enlist™ (2,4-D choline tolerant) varieties were included.  There has not been much Georgia generated data about the performance of Enlist™ soybean varieties in our state.   A quick summary of those Enlist™ varieties is presented in the following table. 

Table 1.  Enlist Soybean Variety Performance in Georgia – 2020. 

Variety	Statewide Average Yield (Bu/A)	Maturity Group Average (Bu/A)
DM 48E73	48.3	47.9
AGS 48E19	54.1	47.9
MS 4800E	52.5	47.9
DM 59E01	65.1	62.5
ZS 5098E3	64.0	62.5
MS 5110E	60.7	62.5
AGS 51E19	61.9	62.5
DM 51E01	61.6	61.7

Five of the eight Enlist™ soybean varieties in these tests had higher yields than the maturity group average.  To get the full report of the preliminary 2020 UGA-OVT soybean yield results, check out this link: https://swvt.uga.edu/content/dam/caes-subsite/statewide-variety-testing/docs/performance-trials/2020/soybean-prelim-2020-tables.pdf

 

EPA Proposes New Safety Measures for Paraquat (Culpepper)

Extension Agents, below is a summary of additional measures that our U.S. EPA has proposed for paraquat (full details at https://www.epa.gov/pesticides/epa-proposes-new-safety-measures-paraquat). If any of these potential requirements challenge the sustainability of our family farms please let me know by January 6, 2021.    

“As outlined in the proposed interim decision for paraquat, the agency is proposing new measures to reduce risks associated with paraquat in order to better to protect human health and the environment. These measures include:

• Prohibiting aerial application for all uses and use sites except cotton desiccation;
• Prohibiting pressurized handgun and backpack sprayer application methods on the label;
• Limiting the maximum application rate for alfalfa to one pound of active ingredient per acre;
• Requiring enclosed cabs if area treated in 24-hour period is more than 80 acres;
• Requiring enclosed cabs or PF10 respirators if area treated in 24-hour period is 80 acres or less;
• Requiring a residential area drift buffer and 7-day restricted entry interval (REI) for cotton desiccation;
• Requiring a 48-hour REI for all crops and uses except cotton desiccation; and
• Adding mandatory spray drift management label language.

In addition, EPA is proposing to allow truck drivers who are not certified applicators to transport paraquat when certain conditions are met.”

Excalia/Herbicide Tank-Mixes (Prostko)

At the recent UGA Peanut Agent Training on December 9, Dr. K. mentioned a new peanut fungicide from Valent sold under the trade name of Excalia (inpyrfluxam). Lately, all my industry friends seem to have forgotten that the crop safety/efficacy of peanut herbicide/fungicide tank-mixtures is one of my most common questions. Thus, I do not have a ton of data for this one in regards to tank-mixtures.  In 2020, I did some quick and dirty strip-trials with tank-mixes of Excalia with either Cadre or Cobra or Ultra Blazer + 2,4-DB + Dual Magnum. In those trials, I did not observe any physical compatibility problems or significant increases in peanut injury (Figure 1, 2, 3),  But, I really need to collect more replicated data.

 

Agent Training Follow Up (Prostko)

Just a few things to follow up on after our recent weed science training on December 2:

1) If you are looking for something to help you better understand herbicide modes of action (MOA), check out the Herbicide Resistance Action Committee's (HRAC) 2020 MOA Classification Chart.  A good one for your pickup truck library.

https://hracglobal.com/files/HRAC_Revised_MOA_Classification_Herbicides_Poster.pdf

2) We had some discussion about the potential residual effects of glyphosate on crops and some of the research that we are conducting.  It's a very complicated issue influenced by many factors (soil type, OM, pH, other soil cations, application rate, timing, species sensitivity).  However, I am not really worried about the residual effects of glyphosate on most major row crops grown in Georgia.  

I was asked specifically about the effects of soil pH on the adsorption of glyphosate.  In general, as soil pH increases, soil adsorption of glyphosate decreases (Figure 1).  This also happens with herbicides in other families such as the triazines (atrazine) and sulfonylureas (chlorimuron).  But, just because glyphosate adsorption is decreased as soil pH increases, it does not automatically mean it will cause excessive crop injury.