Soil-Applied Glyphosate and Peanuts (Prostko)

I received a few questions recently about the use of glyphosate prior to planting or shortly after planting peanuts.  Many of you have remembered (surprisingly!) what Dr. Culpepper has said about the potential residual effects of higher rates of glyphosate on crops such as transplanted squash, broccoli, and collards. Despite what most of us learned in school many years ago, glyphosate does have soil residual properties but it all depends upon the crop and the application rate.  Fortunately, peanut is not a crop that is overly sensitive to glyphosate residues.  In 2020, I conducted a field study to prove this point.  In this study, I applied Roundup PowerMax II 5.5SL at rates ranging from 32 oz/A to 160 oz/A.  Applications were made preplant (6 DBP) or preemergence (1 DAP).  Results indicated that glyphosate had no effect on peanut density, height, width, or yield.  I do not think that a grower should ever use a 160 oz/A rate (5X) but it does prove a point.

  

Valor/Peanut Injury (Again) - Prostko

Last night (May 12), many areas of the state received some rainfall.  In some locations, it was more than 1" (Camilla = 1.47"; Ft. Valley = 2.04"; Midville = 2.67", TyTy = 3.14").  Thus, I am pretty sure that my phone will be ringing off the hook this week about Valor injury in peanuts.  I have discussed this problem many times before in this blog (June 3, 2013; May 4, 2017; May 21, 2020) so check those other posts out.  A few things to remember: 1) This is not a new problem.  Valor injury has occurred somewhere in GA since it was first registered way back in 2001; and 2) History and lots of data suggest that most peanut fields suffering from Valor damage will recover without yield losses.  Here are some pics and data to help you advise your growers not to panic.  Note in the graphs that these plots received more than 8" of rainfall/irrigation within the first 30 DAP and no yield losses were observed even at the 6 oz/A rate.  But, I NEVER want any peanut grower to apply a 2X rate Valor on purpose though!

  

Herbicide Name Recognition (Prostko)

Recently heard of a major whoopsie due to some communication errors.  There are least 3 herbicides floating around Georgia with similar trade names but have very different uses.  Please encourage your growers and dealers to pay close attention to what is being sprayed.

  

Field Corn Weed Control Pictures - 2023 (Prostko)

1) Thought you might be interested in seeing the following pictures from my field corn weed control plots taken over the last week.  For more specific information about these herbicides, check out the 2023 UGA Pest Control Handbook (pages 64-88).  FYI, this is what I am doing when you try to call me between 6 am-9 am.

2) Question #1: Why do I have Prowl H20 3.8SC (pendimethalin) mixed with everything in these treatments?

Texas panicum/buffalograss/bullgrass is one of the most common annual grass weeds in Georgia field corn.  Put very simply, Prowl provides the best residual control of Texas panicum.  If growers are concerned about potential crop injury from Prowl, other residual annual grass control options include Anthem Maxx (pyroxasulfone + fluthiacet), Dual Magnum (s-metolachlor), Outlook (dimethenamid-P), Warrant (acetochlor), and Zidua (pyroxasulfone).  Of these, Anthem Maxx and Zidua are slightly better on Texas panicum (but neither are as good as Prowl).  FYI, Prowl should NEVER be applied PPI or PRE in Georgia field corn, only POST (labeled up to 30" tall/V8).

3) Question #2:  I have heard that Prowl will cause root damage and yield loss when applied to field corn?

A long time ago in a galaxy far far away, Prowl was used as an EPOST (spiking) treatment in combination with atrazine.  Back then, this was about the only way to get reasonable control of Texas panicum.  In that scenario, root pruning was more likely to occur especially when corn was planted <1.5" deep and furrow closure was incomplete.  Delaying Prowl applications allows the corn plant to develop a deeper root system (but still a good idea to plant at least 1.5" deep and have complete furrow closure though).  For many years, I have been applying Prowl POST with various herbicides and have never observed any significant yield losses.