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)

Post-Harvest (Field Corn) Weed Management Reminders (Prostko)

Field corn harvest is well underway in much of south Georgia.  Please remind your growers that it is a great idea to think about managing weeds such as Palmer amaranth and Benghal dayflower at this time of year.  Remember that Palmer amaranth seed is viable within ~2 weeks after pollen shed and Benghal dayflower can go from seed to seed in about 42 days.  Thus, there is ample time to produce lots of seed in those harvested corn fields from now until first frost.  Check out the UGA Pest Control Handbook (pages 74 and 86) for more specific information.

 https://secure.caes.uga.edu/extension/publications/files/pdf/SB%2028-15_3.PDF

a) For growers who will not be planting a small grain this fall, here is one of my favorite post-harvest treatments.  The rate for Gramoxone 3SL (paraquat) would be 32 oz/A. Tricor = metribuzin.

b) For those fields that are plagued by Benghal dayflower, splits shots (7-14 days apart) of either Gramoxone or 2,4-D.

Recent Peanut Problems (Copperleaf, Roundup, Mixing Order, 2,4-DB Rain-Free Period) - Prostko

A few interesting things that crossed my path over the last few weeks:  

1) From Macie Mosteller in Turner County.  Hophornbeam copperleaf in peanut.  Way too big now for herbicides (but not hands or hoes).  Ultra Blazer (acifluorfen) and Cobra (lactofen) are 2 POST control options for smaller copperleaf plants.  Check out this older fact sheet for more info about hophornbeam copperleaf in peanut:

https://secure.caes.uga.edu/extension/publications/files/pdf/C%20882_5.PDF

2) From former legendary Dodge Co. Agent Greg Slaughter (now with RW Griffin).  Roundup (glyphosate) contamination on peanut.  Grower sprayed Cadre (imazapic) + 2,4-DB + Basagran (bentazon) + Dual Magnum (s-metolachlor) + COC.  Sadly, this happens a lot (too much) in south Georgia.  Tissue samples sent to Waters Lab in Camilla confirmed the presence of glyphosate (0.3 ppm). How did it get there? Jug management????? Check out this older fact sheet for more info about peanut tolerance to glyphosate:  

https://archive.ces.ncsu.edu/wp-content/uploads/2014/10/PEANUT-NOTES-No.-104-2014-UGA-Glyphosate-on-Peanut.pdf?fwd=no

3) From Bill Tyson in Bulloch Co. The tank-mix blues strike again! Mixing order is important!! A slight change in mixing order helped fix this problem.  Check labels for proper mixing orders. Tons of good info in those labels!

4) It has come to my attention that the rain-free period for 2,4-DB listed in the peanut section of the 2025 UGA Pest Control Handbook of 1 hour (page 222) is NOT correct.  Not sure where I came up with the 1 hour since nothing specific is listed on any label nor is it consistent with other sources? After talking with technical folks at Albaugh, LLC (makers of Butyrac 175 or Butyrac 200), the rain-free period for 2,4-DB should be 6 hours.

Florida Beggarweed in Peanut (Prostko)

I was texted the following picture (slightly blurry) early yesterday morning from a SW-GA crop consultant.  He commented that it was all over the field.

This is Florida beggarweed (kidney-shaped cotyledons).  When I first got to GA in 1999, Florida beggarweed was the #1 peanut weed.  It became less troublesome when Valor (flumioxazin) was registered in 2001 (very effective) and when Palmer amaranth exploded. Florida beggarweed tends to be a later emerging weed and prospers during wetter conditions. 

At this point in the growing season, there are not many good options for controlling Florida beggarweed in peanut. The first option is a POST (60 days after peanut emergence) application of Classic (chlorimuron).  The other option is to use Gramoxone (paraquat) in a non-selective applicator (wiper, sponge, rope-wick).  Both of these options are described on page 224 of the 2025 UGA Pest Control Handbook and/or listed below. Please carefully read the comment sections of these recommendations.  Peanut cultivar tolerance to Classic is a major concern.  If a newer peanut cultivar is not listed in the comment section (i.e. Arnie, TifNV-HG, etc.), that means I DO NOT have any tolerance data and have no clue what will happen.