What's Up This Week (Prostko)

A couple of interesting things to share with you this week:

1) Check out the following picture sent to me by Dr. Alan York (NCSU).  On day 1, Mr. Peanut Grower mixed 2,4-DB and dry manganese sulfate in 700-800 gallons of water with no problems.  On day 2, Mr. Peanut Grower mixed the same combo with only 100 gals of water and OH NO!!!!.  A great advertisement for pre-slurrying dry formulations prior to mixing in a big tank.

2)  Much ado in the the Mid-South about off-target movement of dicamba.  We have experienced a few problems in GA but nothing compared to what's going on there.  Just recently, I was asked how non-dicamba soybean yields could be affected by off-target movement of dicamba.  Although soybeans are very sensitive to dicamba and low rates will cause leaf cupping and epinasty, vapor drift rates (1/1000th X) and particle drift rates (1/100th X) will likely cause yield losses of < 9% depending upon the soybean stage of growth.

3) Current list of dicamba tolerances (i.e. how much residue in a crop is legal) can be obtained at the following web-site:

https://www.law.cornell.edu/cfr/text/40/180.227

Recent Tank-Mix Issues (Prostko)

Last week, I received a few calls and pictures from some folks about tank-mixes and peanut injury (Figures 1 and 2).  I will remind you that there is nobody on the planet that can assure any peanut grower that a tank-mix will be 100% safe and 100% effective all the time. There are too many variables to consider including the number of products in the spray tank, GPA, air temperature, humidity, leaf wetness, overall peanut plant health, and time of day.   I think part of the problem last week was our higher than normal temperatures (Figure 3).  A few tips for growers considering spraying untested tank-mixes:

a) Limit the number of products that are put in a spray tank.  Bite the bullet and make separate applications when practical.
b) Spray early in the morning when air temperatures are lower and the peanut plants have not been baking in the sun all day.
c) Increase water volumes from 10 GPA  to 15 GPA (less concentrated spray droplets).

Figure 1.  Peanut response to Convoy + Alto + Bifenthrin fb Select + COC
 1 hour later (i.e. really a 5 way tank-mix)

Figure 2.  Peanut response to Propulse + 2,4-DB (i.e. really a 3 way tank-mix)

Figure 3.  Maximum air temperatures, Attapulgus (GA), June 30 to July 7, 2015, 2016, 2017
(Source:  UGA Automated Weather Network)

Weed Science Update - June 16 (Prostko)

Just got done rating some of my soybean weed control plots.  Thought I would pass along these few thoughts.

1) Not sure what to say when someone asks me "When are you guys going to figure out how to control pigweed?"  I am pretty confident that we have but not everyone listens or can get it done! (Figure 1).

  

Figure 1.  General overview of 2017 soybean weed control plots in Ty Ty, GA.   Notice weedy-checks in comparison to other plots (started clean + activated residual + timely POST).

2) I fear that some are thinking that the new auxin technologies are the greatest thing since sliced bread.  That would be very stale sliced bread since 2,4-D has been around since the 1940's and dicamba since the 1960's.  I am still getting great results with other chemistries (Figure 2).

Figure 2.  Soybean weed control in 2017 with Tricor (metribuzin) followed by Roundup PowerMax (glyphosate)+ Reflex (fomesafen).

3) If growers decide that they must use the auxin weed control systems, I cannot over emphasize the need for residual herbicides in these programs (Figure 3).

Figure 3.  Weed regrowth/emergence (1 sq. ft.) 25 days after a single application of Roundup PowerMax (28 oz/A) + Xtendimax with VaporGrip (22 oz/A).

  

Valor Injury or The Sky Is Falling (Prostko)

My right ear is currently bleeding due to the numerous telephone calls that I have received over the last few days about Valor injury in peanuts.  Peanuts that were planted approximately 10 days ago or so were in a great place to get hammered from Valor because of the recent rainfall events (Figure 1).   Everyone seems to be panicking as though this was a surprise??????  If it rains on Valor treated peanuts when they are cracking and small (~2 weeks after cracking), injury will occur.  Peanuts typically recover from this injury without a yield penalty.  Check out Figures 2 and 3 from some of my research back in 2009.  In this trial, more than 5" of rainfall occurred in the 30 day period after peanut planting.  Peanut injury was significant but yields were not reduced even at a 2X rate.  Not sure what else I can say or do at this point???

Zidua Peanut Label (Prostko)

On Friday afternoon, May 19, I received word from BASF that Zidua (pyroxasulfone) was labeled for use in peanut.  I have been conducting peanut research with pyroxasulfone for more than 10 years (over 47 field trials).  In a nutshell (no pun intended), Zidua will compete with Dual Magnum or Warrant in our POST peanut herbicide programs for the residual control of Palmer amaranth and a few other weeds (Figure 1). Some advantages for Zidua include its lower use rate (1.5 oz/A-2.1 oz/A) and improved control of other broadleaf weeds such as Florida beggarweed.  Generally, I have observed no real differences in performance/yield between Zidua, Dual Magnum, and Warrant when used in a complete peanut weed control program (Table 1). A copy of the supplmental peanut label can be obtained at the following web-address: http://www.cdms.net/ldat/ldAMK017.pdf

Figure 1.  Zidua vs. Dual Magnum Programs in Peanut - 2016.

Table 1.  Dual Magnum/Warrant/Zidua Peanut Weed Control Programs - 2014.

Common Cocklebur in Peanut (Prostko)

Chris Tyson (Tattnall County) recently sent me a picture of a common cocklebur seedling (Figure 1).  In 2016, Brian Hayes (Grady County) had a peanut grower with a very serious cocklebur problem (Figure 2).  In fact, that peanut field in Grady County was probably the first time that I ever made a recommendation just for that specific weed.  At one time though, cocklebur used to be a more widespread weed problem but sorta disappeared during the "glyphosate era".   Peanut herbicides with good to excellent activity on cocklebur include the following: 2,4-DB, Basagran, Cadre, Cobra, Gramoxone (paraquat), Pursuit, Storm, Strongarm, and Ultra Blazer.  On the downside, Valor is not very effective on this weed so don't be surprised if you see cocklebur in a Valor treated field. The fruiting structure of cocklebur (i.e. the big bur that sticks to your favorite shirt or hunting dog) contains 2 seeds, one for now and one for later.   

Figure 1.  Common cocklebur seedling (Source: Chris Tyson)

Figure 2.  Common cocklebur infestation in a Grady County peanut field, 2016.

Peanut Injury Likely (Prostko)

Rainfall events today will likely result in the development of Valor injury on peanut, especially in fields where the peanut plants are just beginning to emerge/crack.  In preparation for any upcoming questions, please refer to my Weed Science Blog on May 20, 2014.  This should help refresh your memory.  No need to re-invent the wheel.

http://ugaweedscience.blogspot.com/2014/05/peanut-injury-update-prostko.html