Droplet Sizes for Contact POST Herbicides (Prostko)

When visiting with your growers, please remind them to use a nozzle/pressure combination that produces COARSE droplets (VMD₅₀ = ≥ 270 microns) when applying contact herbicides such as Basagran (bentazon), Cobra (lactofen), Gramoxone (paraquat), Liberty (glufosinate), and Reflex (fomesafen).  COARSE droplets provide a reasonable balance of drift protection and coverage.  Droplets larger than coarse provide better drift protection but less coverage. Coverage is extremely important for contact herbicides especially when application conditions are not favorable (large weeds, cold temperatures, drought). Various nozzle types and pressures can be used to obtain COARSE droplet sizes (green color on TeeJet chart listed below).

Not playing favorites here with this TeeJet chart but a recent UGA Extension survey indicated that 68% of Georgia farmers use TeeJet nozzles. Other nozzle purveyors include the following:

Greenleaf Technologies: https://greenleaftech.com/

Pentair Hypro: https://www.pentair.com/en-us/flow/hypro/hypro-products/hypro-spraying-products/hypro-spray-nozzles.html

John Deere: https://cdn.prod.website-files.com/66e9e33a09ceaffe3ed4b8dd/66fef97547cff80b92845bf6_JD-Sprayer-Parts-Catalog-2019.pdf

Paraquat Trainings (Prostko)

Since Syngenta recently announced that they will no longer be manufacturing the active ingredient paraquat (https://www.syngenta.com/media/syngenta-cease-paraquat-production-uk-2026), I have received numerous inquires about the future of the US EPA required paraquat safety trainings (https://www.epa.gov/pesticide-worker-safety/paraquat-dichloride-training-certified-applicators#q4).  The following is information that I received from Syngenta on March 13 regarding the issue of paraquat safety training:  

"Syngenta will continue to provide paraquat training via its online training portal while channel inventories of Gramoxone® Herbicide still exist. Our commitment to stewardship, safe use, and regulatory compliance remains unchanged, and we recognize how essential this training is for certified applicators across the country.

 

As we look ahead, Syngenta is actively evaluating options to transition the paraquat training program to an alternative host to ensure continuity beyond our direct involvement. We will share updates as soon as a viable path is confirmed.

 

Thank you for your continued dedication to safe and responsible pesticide application. If you need assistance accessing the training, please reach out to your Syngenta representative or visit the paraquat training portal.  Gramoxone Herbicide is a Restricted Use Pesticide.  Always read and follow label instructions."

Dicamba Preplant in Field Corn (Prostko)

It has come to my attention that the recommendations for preplant/burndown applications of dicamba for field corn in the UGA Pest Control Handbook are NOT sufficiently described.  After closer review of the product labels, there needs to be some adjustment.  Please review the following with any grower who desires to use dicamba for preplant/burndown weed control prior to planting field corn.

1) The newer formulations of dicamba (Stryax®, Engenia®) are NOT labeled for this particular use.

2) Older formulations of dicamba (Clarity®, Rifle®, Sterling Blue®) are labeled for this use depending upon tillage system and soil type as follows:

a) PREPLANT AND PREEMERGENCE APPLICATION IN NO TILLAGE CORN: Rates: Apply 16 fluid ounces of Clarity®, or Rifle®, or Sterling Blue® per acre on medium-or fine-textured soils containing 2.5% or greater organic matter. Use 8 fluid ounces per acre on coarse soils (sand, loamy sand, and sandy loam) or medium-and fine-textured soils with less than 2.5% organic matter.  

b) PREEMERGENCE APPLICATION IN CONVENTIONAL OR REDUCED TILLAGE CORN: Rates: Apply 16 fluid ounces of Clarity®, or Rifle® or Sterling Blue® per treated acre to medium- or fine-textured soils that contain 2.5% organic matter or more. DO NOT apply to coarse-textured soils (sand, loamy sand, or sandy loam) or any soil with less than 2.5% organic matter until after corn emergence.  

c) Failure to follow these recommendations could result in excessive crop injury.  If a grower applies dicamba as a burndown in a field intended to be planted to dicamba-tolerant cotton or soybean and changes their mind and wants to plant field corn, please contact me ASAP. 

3) Everyone always asks me what my preferred burndown is for field corn.  Lots of good choices.  But, I prefer Roundup or Gramoxone + atrazine because these combos will control most of our common winter weeds and field corn can be planted immediately without concern for crop injury.  See below.

Ryegrass Control in Conventional Field Corn (Prostko)

Lucy Ray from Morgan County recently asked me about ryegrass control in conventional field corn.  Here are my thoughts:

1.  I contacted several local GA corn seed reps to see what conventional hybrids with tolerance to ALS-inhibiting herbicides would be recommended in Georgia.  The short list is as follows: Dekalb 68-37 or 66-02 or 111-30; Integra 6588; Dyna-Gro 57CC51; Pioneer 1608 or 17677; and AgriGold A645-16.
2. Ryegrass is extremely difficult to control in conventional corn.  Expectations should be fair/marginal at best. NO miracles here!
3. Three postemergence herbicides are available for use in conventional corn that have some activity on ryegrass (again not great but all we got).  These include Accent Q (nicosulfuron), Revulin Q (nicosulfuron + mesotrione), and Steadfast Q (nicosulfuron + rimsulfuron).  These herbicides cannot be used if Counter is applied in-furrow for soil insect/nematode management.  
4. My suggested weed control program for this scenario would be as follows (reduced tillage/strip tillage): 

1. Prior to planting, if ryegrass and other winter weeds are emerged, split shot of Gramoxone 3SL (paraquat) @ 32 oz/A (~10 days apart) + COC @ 1% v/v (1 gal/100 gal). In the second shot, add Dual II Magnum 7.64EC (S-metolachlor) @ 16 oz/A for residual control of annual grasses and broadleaf weeds.  This second shot of Gramoxone + Dual II can be applied before or after planting (but before corn emergence).  The goal here is to start off as clean as possible.
2. At V3-V5 stage of corn, apply either Accent Q 54.5WDG @ 0.9 oz/A or Steadfast Q 37.7WDG @ 1.5 oz/A or Revulin Q 51.2DF @ 3.5 oz/A + Atrazine 4L @ 64 oz/A + NIS @ 0.25% v/v (1 qt/100 gals).  Remember these are not great (for ryegrass/crabgrass) but all we have for POST grass control in conventional corn.  

    5)  FYI, ryegrass is one of many weeds that does not like deep tillage (i.e. turning plow).

Positive Pesticide Points (Prostko)

It's not too often that the general public hears any positive information about the safe use of pesticides in agriculture. In 1991, the U.S. Department of Agriculture (USDA) Agricultural Marketing Service (AMS) was charged with designing and implementing the Pesticide Data Program (PDP) to collect data on pesticide residues in food. Congress mandated the program in the 1996 Food Quality Protection Act (FQPA). The results of the 2024 PDP Annual Summary were recently published.  Here are the highlights:

1) 9,872 food samples were tested

2) Fresh and processed foods tested were as follows: almonds, apples, avocados, blackberries (fresh and frozen), cherry tomatoes, cucumbers, head lettuce, leaf lettuce, onions, oranges, pineapples (fresh and frozen), potatoes, canned pumpkin, sweet corn (fresh and frozen), tomatillos, and salmon. 

3) Domestic samples accounted for 60.1% of all samples, while 38.9% were imports, 0.9% were of unknown origin, and less than 0.1% were of mixed national origin.

4) Over 99% of the samples tested had residues below the tolerances established by the EPA with 42.3% having NO detectable residue.  

5) As a reminder, the U.S. EPA determines the maximum residue levels (MRL’s) or tolerance of pesticides in food products based upon a standard 100-fold margin of safety to protect all people and the environment.  In addition to this base margin of safety, the FQPA of 1996 imposed an additional 10-fold safety factor (1000X) to protect infants and children, unless sufficient evidence is presented to reduce (Reeves et al., 2019. Adv. Nutr. 10:80-88).

6) A copy of the complete report can be found at the following web-address:

https://www.ams.usda.gov/sites/default/files/media/PDPAnnualSummary.pdf

7) Spread this good news when you have the opportunity to talk to someone about pesticides/agriculture!

Harvest Weed Seed Control Information from GROW (Prostko)

County extension agents and grain (soybean, wheat, sorghum, not so great for corn due to combine header differences) producers interested in harvest weed seed control methods (i.e. seed impact mills and chaff lining) might want to check out a newly released web-page from the GROW Project.  GROW (Getting Rid of Weeds) is a team of university/USDA agronomists, weed scientists, economists, and communicators from all over the United States.  The mission of GROW is to help farmers across the U.S. fight herbicide resistance by using a greater diversity of weed control strategies to complement chemical use.  Check out this new GROW web-page for more information about harvest weed seed control:

https://growiwm.org/how-harvest-weed-seed-control/

Soybean Green Stem (Prostko)

Late yesterday afternoon, I received a phone call from Floyd Co. Extension Agent, Keith Mickler, about green stem in soybean (Figure 1.)  I can tell you from personal experience that green stem can cause major headaches when combining soybeans.  In fact, it took 6 man hours to clean out my small-plot combine last year after it got stopped up with green stemmed beans! (knife, machete, long screwdriver, torch, lots of sweat equity)

A few things to know about green stem:

1) Green stem is a term used to describe abnormal or delayed maturation in soybeans where the stems and/or leaves of affected plants stay green even after pods reach physiological maturity.

2) Any factor that reduces seed pod development and seed set can lead to green stem.

3) Natural senescence of soybean requires a strong draw of nutrients from the vegetative portion of the plant (source) to the developing seed (sink).  When sink tissue is reduced, protein and sugars are retained in the source tissue resulting in green stems.

4) Seasonal environment stresses (water, temperature, hailstorms, animal damage, excessive soil nitrogen availability at R6-R7), certain viruses (Bean pod mottle virus, Tobacco ringspot virus and Alfalfa mosaic virus), insects (stinkbugs, common brown leafhopper, bean leaf beetle), soybean genetics (cultivars), and fungicides (especially strobilurims) are considered to be causal agents and risk factors associated with green stem.

5) Harvest aids or desiccants such as Gramoxone (paraquat) or Defol (sodium chlorate) have had some effect on green stem but are often inconsistent.  Recent research showed that desiccants reduced green stem about 50% of the time.  Defol 5 applied at R7 reduced green stem by 38.3%-50.9% compared to the NTC with short (0.5-1.0 point shorter than normal) and normal maturity groups but not in long (0.5-1.0 longer than normal) maturity groups. (FYI, I have never sprayed a single drop of Defol in my entire career.)

6) Combine operators will need to reduce speed when harvesting soybean fields with green stem.

7) Green stem can resolve itself after a hard freeze.

8) Current soybean harvest-aid/desiccant recommendations can be found on pages 265-266 of the 2025 UGA Pest Control Handbook. 

https://fieldreport.caes.uga.edu/wp-content/uploads/2025/08/SB-28-28_3.pdf

Information Sources (recently published in 2025):

Geiss et al.  Understanding green stem in soybeans.  Crop, Forage & Turfgrass Management. 2025;11:e70065 (https://acsess.onlinelibrary.wiley.com/doi/epdf/10.1002/cft2.70065)

Kendall et al.  Harvest aid applied at soybean growth stage R7 rarely impacted seed, protein, or oil yield.  Agronomy Journal. 2025;117:e70109 (https://acsess.onlinelibrary.wiley.com/doi/epdf/10.1002/agj2.70109)