Peanut Weed Control Thoughts This Week - May 25 (Prostko)

A few things to share with your growers based upon my phone calls and field observations: 

1) I am getting the feeling that many peanut growers are blindly applying EPOST or "cracking" sprays of paraquat without first walking their fields.  From my field plots earlier today, Figure 1 is a picture of a non-treated check (NTC) plot while Figure 2 is a picture of Prowl + Valor + Strongarm applied PRE.  In this case, the PRE herbicides worked as expected and there is no need for an EPOST or "cracking" application of paraquat.  

Figure 1. Non-treated check plot. Ty Ty, GA. May 28, 2020.

Figure 2.  PRE applied Prowl H20 @ 32 oz/A + Valor EZ @ 3 oz/A + Strongarm @ 0.225 oz/A.
Ty Ty, GA.  May 28, 2020.  Photo 17 DAP.

2) I have been hearing some interesting recommendations for "cracking" sprays coming from industry but I (UGA) will stick with what works and has been proven by lots of research (i.e. paraquat + Storm or Basagran + Anthem Flex or Dual Magnum or Outlook or Warrant or Zidua) (Figure 3).

Figure 3.  Left = NTC; Right = Prowl H20 @ 32 oz/A (PRE) then Gramoxone 3SL @ 8 oz/A + Storm @ 16 oz/A  + Dual Magnum @ 16 oz/A  applied 3 days ago.

3)  The current price of Storm 4SL (~$80/gal) has some folks gasping for breath.  Thus, 16 oz/A costs $10.00/A.  If a grower wants to make his/her own Storm, the equivalent mix would be Ultra Blazer @ 11 oz/A ($4.38/A) + Basagran @ 11 oz/A ($3.87/A).  However, if a grower was going to mix his/her Storm, I would prefer the mixture to be Ultra Blazer @ 16 oz/A ($6.38/A) + Basagran @ 8 oz/A ($2.81/A).  But, this mix would be slightly hotter and more effective.  

Valor Injury on Peanut Is likely (Prostko)

Rainfall events of May 20/21 will likely result in Valor injury on peanut.  Although I have addressed this issue in many previous blogs (June 3, 2013; May 20, 2014, May 26, 2017, May 6, 2019), here is another general summary of the Valor injury/yield data that I have collected over the past 21 years: 

1)      11 replicated field trials with reliable yield data

2)      11/11 trials, Valor 51WG @ 3 oz/A had no negative effect on peanut yield

3)      9/11 trials, no difference in yield between 3 oz/A and 6 oz/A (FYI, 6 oz/A is not labeled or recommended)

4)      2/11 trials, 6 oz/A caused yield losses when compared to 3 oz/A (6.9% to 8.8% yield loss).

Bottom line is that peanut fields suffering from injury, when Valor was applied at the labeled rate (3 oz/A) and timing (no later than 2 DAP), will very likely recover with no effects on final yield!

Cracking Time Reminders for Peanuts (Prostko)

As of May 11, 28% of the Georgia peanut crop was reported as planted.  Thus, peanut growers should now be evaluating the success of their PRE weed control programs and deciding on the need for early postemergence or "cracking" herbicide applications.  Here are a few reminders about cracking sprays:

1) If a peanut grower started clean and used a good residual weed control program (i.e. Prowl or Sonalan + Valor + Strongarm) that was activated with irrigation or rainfall, the need for a cracking spray is questionable.  Best thing in this situation is to go to the field and look to see what has escaped or not.  If the field is relatively weed-free, a cracking spray may not be justifiable.   Growers might consider waiting until 30-40 DAP to pull the trigger earlier on a POST program such as Cadre + 2,4-DB + Anthem Flex or Dual Magnum or Outlook or Warrant or Zidua.  

2) If a grower decides to use a cracking spray, I would suggest a combination of paraquat + Storm or Basagran + Anthem Flex or Dual Magnum or Outlook or Warrant or Zidua.  Suggested use rates would be as follows:

    a) 2 lb ai/gal paraquat = 12 oz/A or 3 lb ai/A paraquat = 8 oz/A

    b) Storm 4SL @ 16 oz/A or Basagran 4SL @ 8 oz/A.  If a grower wants to make his own "Georgia" Storm then use Ultra Blazer 2SL @ 16 oz/A + Basagran 4SL @ 8 oz/A.

    c) Anthem Flex 4SE @ 3 oz/A or Dual Magnum 7.62EC @ 16 oz/A or Outlook 6EC @ 12.8 oz/A or Warrant 3ME @ 48 oz/A or Zidua 85WG @ 1.5 oz/A or Zidua 4.17SC @ 2.5 oz/A.

3) If Dual Magnum or Outlook are used with paraquat + Storm or Basagran, no additional adjuvants are required.  If Anthem Flex or Warrant or Zidua are used, a NIS @ 0.25% v/v is suggested.

4) I would prefer peanut cracking sprays to be applied in 15 GPA and tractor speeds of 10 MPH or less to improve spray coverage and reduce the production of dust (which can greatly reduce paraquat efficacy). 

5) Given the option of using either an AIXR or TTI spray tip, I would prefer the AIXR tip.  

6) If growers use higher rates of paraquat and/or delay paraquat applications past 28 days after cracking (DAC), the risk for yield loss resulting from paraquat injury is increased.  Recent results from a 2018 weed-free field trial indicated that paraquat treatments applied ~35 DAC resulted in a 5.5% peanut yield reduction.