Weed Control in Conventional Corn (Prostko)

Yesterday while attending the Georgia Peanut Commission Research Update, I had the pleasure of sitting next to Tift Co. Extension Agent, Justin Hand.  He mentioned to to me that several of his growers are interested in weed control programs for conventional field corn.  I suspect that many of you might also be interested in this topic so here are a few thoughts:

1) Conventional field corn hybrids are available from several companies.  Here are a few:

Dekalb: DKC59-80, DKC111-30, DKC63-58, DKC66-02, DKC68-37

https://www.cropscience.bayer.us/corn/dekalb/seed-catalog

Dyna-Gro: D57CC51

https://dynagroseed.com/seed-finder/corn?cropsId=dynagroseed:crops/corn

Pioneer: P1197, P1870, P1608, P17677 all have conventional versions but supply might be limited

https://www.pioneer.com/us/product-catalog/crop-corn.html

Please contact our new Extension Grains Agronomist, Dr. Nick J. Shay (Nicholas.Shay@uga.edu) for more information about field corn hybrids. 

2) Here is a slide from my 2025 county presentation about weed control in conventional field corn. Growers need to double-check labels since some herbicide tank-mixes are prohibited (i.e. Callisto and Dual Magnum or Outlook).  Also, growers need to confirm the tolerance of any field corn hybrid to the WSSA/HRAC Group 2, Group 15, and Group 27 herbicides. If Counter is used in-furrow for soil insects/nematodes, Callisto, Revulin Q, and Steadfast Q cannot be applied POST. 

3) Here are some field pictures of these herbicide programs from my 2023 and 2024 research plots. This research was partially supported by the Georgia Corn Commission.

4) Feel free to contact me at any time via phone/text (229-392-1034), e-mail (eprostko@uga.edu), carrier pigeon, or smoke signal. I am available to you 365/24/7!

National Pesticide Safety Education Month (Prostko)

February 2025 is the 8th Annual National Pesticide Safety Education Month (NPSEM).  The NPSEM web-page has lots of good information about basic pesticide safety principles, storage, drift, wildlife protection, etc.  Check out the following web-page for more information:  

https://pesticidestewardship.org/national-pesticide-safety-education-month/

Does Roundup + Atrazine Applied POST in Field Corn Reduce Yields? (Prostko)

    I recently received a phone call from a south Georgia corn farmer who told me that someone was going around saying that a Roundup + Atrazine tank-mix, applied POST in field corn, will reduce yields.  My response was show me the data.  Here is my data from 3 on-farm field trials conducted in a high yield environment (250+ Bu/A) from 2014-2016.  Bottom line, yields from plots treated with Roundup + Atrazine + AMS applied POST were NOT statistically different from the untreated check in all trials.  

    As long as growers follow the label (i.e. rates and timing), I am not concerned at all.  A quick look at the Roundup PowerMax3 label:

USE INSTRUCTIONS: This product may be applied alone or in a tank-mix over the top of field corn hybrids with Roundup Ready 2 Technology from emergence through the V8 stage (8 leaves with collars), or until corn plant height reaches 30 inches (freestanding), whichever comes first, unless otherwise directed. Use drop nozzles for optimum spray coverage and weed control when corn plant height is 24 to 30 inches. When corn plants are 30 to 48 inches tall (freestanding), apply this product using only ground application equipment fitted 16 with drop nozzles aligned to avoid spraying into the whorls of the corn plants. Maximum single in-crop application rate of this product up to 48-inch field corn is 30 fluid ounces per acre. Total in-crop application of this product from corn plant emergence through 48 inches in height must not exceed 60 fluid ounces per acre.

    If a grower uses higher rates than listed above and/or applies Roundup later than suggested, yield losses can occur.  This is what what happens to corn ears when glyphosate is applied at tassel (i.e. way off-label).  

As a reminder, atrazine is only labeled for POST use in field corn up to 12" tall.

New Herbicide Classification Chart (Prostko)

The Take Action Pesticide-Resistance Management Program has recently updated their herbicide classification chart.  This chart has 2 sections including a color coded mode of action/site of action chart and pre-mix herbicide product chart.  This is a very good reference material to have in your office or truck. 

Take Action is a farmer-focused educational platform designed to help farmers manage herbicide, fungicide, and insect resistance. Take Action started with industry-wide collaborative discussions about the growing threat of herbicide-resistant weeds. Parties included representatives from major ag chemical companies, land-grant university weed scientists, and soybean/corn/cotton/sorghum/wheat commodity groups.  Resource development for Take Action on Weeds is funded through a United Soybean Board grant.

A copy of this herbicide classification chart can be downloaded from the following web location:

https://iwilltakeaction.com/wp-content/uploads/2024/11/2025-Herbicide-Classification-Poster-GROW-2024-Oct-V2.pdf

Additionally, I have 100 hard copies of this chart in my office and these are available to anyone who wants one on a first-come/first-serve basis. Just let me know.

For more information about The Take Action Pesticide-Resistance Management Program refer to the following web-site:

https://iwilltakeaction.com/about-take-action/

New Pesticide Data Program Summary (Prostko)

 I am always on the hunt for positive information about the use and need for pesticides in agriculture.  In November of this year, the USDA/AMS released its Pesticide Data Program's 33rd Annual Summary (2023).  This report provides high-quality data on pesticide residues in food, particularly foods most likely consumed by infants and children.  A few highlights of this report are as follows:

1) 9,832 food samples were collected.

2) Fresh and processed fruit and vegetables tested during 2023 were: almonds, apples, avocados, baby food applesauce, baby food carrots, baby food green beans, baby food peaches, baby food pears, baby food peas, baby food sweet potatoes, blackberries (fresh and frozen), celery, grapes, mushrooms, onions, plums, potatoes, sweet corn (fresh and frozen), tomatillos, tomatoes, and watermelon.

3) More than 99% of the samples tested had residues below the tolerances established by the EPA with 38.8% having no detectable residue.    

4) Residues exceeding the tolerance were only detected in 0.49% of the total samples tested.

5) A residue is any amount of pesticide that remains after an application.  A tolerance is the maximum amount of residue that may remain in or on food marketed in the US.  The US 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 Food Quality Protection Act (FQPA) of 1996 imposed an additional 10-fold safety factor to protect infants and children, unless sufficient evidence is presented to reduce.    

6) A copy of the complete report can be obtained from the following web-site:

https://www.ams.usda.gov/sites/default/files/media/2023PDPAnnualSummary.pdf

Corteva Enlist® Training (Culpepper/Prostko)

We just wanted to make you aware of the fact that Corteva will be hosting several Enlist® training meetings in AL, GA, and SC.  Topics to be covered include tank-mixing, nozzle selection, sprayer cleanout, weather, and field planning.  Since the dicamba cotton/soybean labels are currently vacated, it is likely that we could see more use of Enlist® One (2,4-D choline) and Enlist® Duo (2,4-D choline + glyphosate) in both cropping systems.  For more information about the Enlist® weed control system, check out the following web-site: Enlist.com

Post-Harvest Tropical Spiderwort/Benghal Dayflower Control (Prostko)

Field corn growers who do not control tropical spiderwort/Benghal dayflower in the fall after harvest are missing a HUGE opportunity to reduce seed-rain back into a field.  Failure to control this plant in the fall is one reason why many Georgia growers continue to have major problems with this weed.  

Check out the following data/pictures from a test that we currently have in a Grady Co. harvested corn field (Thanks Cale!).  You will note that the most effective treatment at this time was a split application of Gramoxone 3SL @ 32 oz/A + Induce @ 0.25% v/v.  I would expect better control from the other treatments if they would have been applied earlier to smaller plants and/or also included a COC or MSO (I was trying to save $$ and determine if a tank-mix with a "loaded" glyphosate would be adequate).   

Since we are not likely to get a hard freeze until ~November 15 in south GA, there is still plenty of time left for tropical spiderwort/Benghal dayflower to produce viable seed.  Viable/ripe seed can be produced within 14 to 22 days after aerial flower opening.  Additional information about the post-harvest control of tropical spiderwort/Benghal dayflower can be found on page 74 of the 2024 UGA Pest Control Handbook.

Newer county extension agents might also want to print out this publication that the UGA Weed Science Team wrote a few years ago.  It's still very relevant.

https://secure.caes.uga.edu/extension/publications/files/pdf/C%20884_2.PDF