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.

For the Doubting Thomas (Prostko)

Here is a quick picture from my research plots earlier today.  Further proof that herbicides work well when applied on time.  Generally, I do not have any preference for what Group 15 herbicide is used in this EPOST + POST program (Anthem Flex, Dual Magnum, Enversa, Outlook, Warrant, or Zidua).  But, I would prefer that our growers not tank-mix Anthem Flex with Cadre + Cobra + 2,4-DB (POST) at this time (i.e., I need more data).  Also, please keep in mind that these are average prices and prices may be more or less depending upon the grower.  

If you need more info about herbicide mechanisms of action (Groups), check this out from the Weed Science Society of America:

https://wssa.net/wp-content/uploads/WSSA-Mechanism-of-Action.pdf

More Tank-Mix Stuff (Prostko)

 1) Here is a quick picture of a recent peanut tank-mix from JB in Wilcox Co. that was applied without a hitch. I would welcome more pictures from any County Agent of good and bad tank-mixes.  If you send me a tank-mix picture, try to get planting date, application date, and picture date. 

2) Here is an example why conducting meaningful tank-mix research is nearly impossible.  

Grower Tank-Mix Application:

 

My tank-mix application of same treatment: Looks nothing like what grower saw?

3) This ain't starting clean and no way any soil residual herbicide will work on a large, buried pigweed plants!!!! Notice buried stems/roots.  

Palmer Amaranth Control Update (Prostko)

About 2 weeks ago, I put out a small Palmer amaranth control test in Wilcox Co. with John Bennett and Macie Mosteller.  The goal of the test was to investigate potential PPO-resistance.  About 10 minutes after we were done spraying, it rained 0.7".  I went back to the field 2 days later and re-treated in another area of the field.  Here are a few things that we learned:

a) Sometimes the weatherman is correct.  

  

b) Cobra was rain-fast in those 10 minutes (label says 30 minutes) but Gramoxone + Ultra Blazer + Basagran + Dual Magnum was not (need 4 hour rain-free period).  FYI, I have most rain-free periods listed in the comment sections of my various chapters in the 2025 UGA Pest Control Handbook.

c) Applications of Cobra made just 48 hours later were significantly less effective.  In that short time period, average Palmer heights went from 3.54" to 5.05".  Using average heights is NOT a great idea because at both application times 30-50% of the measured plants were larger than the average.

d) Had we and the farmer been in the field 7 days earlier (with no rain), I am certain that a "cracking" application of Gramoxone + Ultra Blazer + Basagran + Dual Magnum would have cleaned up this mess.  TIMELINESS is everything!!!

e) Pretty sure that this population of Palmer amaranth is not PPO-resistant since the 1st application of Cobra was effective.  We also sent some plant samples to the University of Illinois Plant Clinic since they can test for PPO-resistance.  Have not received any results at his time.  

https://extension.illinois.edu/plant-clinic