I have received calls this week about weed control options in peanuts, especially dry land peanuts. Some have been concerned that we might add too much stress by applying certain herbicides to an already struggling plant due to the heat and drought. UGA Weed Scientist, Dr. Eric Prostko:
1) Cracking/EPOST applications of paraquat mixtures or solo applied Storm or Ultra Blazer should be delayed as late as possible in peanut fields suffering from Valor injury. I would argue that if Valor injury has occurred, then good weed control has also occurred and a cracking treatment might not really be needed. Paraquat treatments can safely be applied in peanuts up to 28 days after cracking.
2) Common paraquat mixtures include paraquat + Storm or Basagran + Dual Magnum or Warrant or Zidua. I have no preference between Dual Magnum, Warrant or Zidua. There is no need for additional adjuvants with Dual Magnum mixes but a NIS (0.25% v/v) should be used in Warrant or Zidua + paraquat tank-mixes. FYI, I am not a huge fan of paraquat + Dual Magnum or Warrant or Zidua without any Basagran/Storm due to greater injury potential that might reduce yields (especially under these lava-like weather conditions). Also, paraquat without Basagran/Storm is not very effective on smallflower mg.
3) With paraquat mixes, I prefer Storm (bentazon + acifluorfen) over Basagran (bentazon) due to the variety of weeds that can occur in any given peanut field in Georgia. My typical recommended use rate of Storm in EPOST paraquat tank-mixes is 16 oz/A. If need be, growers can make their own “Georgia” Storm by mixing 16 oz/A of Ultra Blazer 2SL + 8 oz/A of Basagran 4SL (yes, this is a slightly hotter mix than 16 oz/A of Storm).
4) It is very hot and very dry right now. Non-irrigated growers who were planning on using paraquat tank-mixes after peanut emergence might want to re-considering their options. Why? Rainfall/irrigation is critical in helping peanut plants recover from paraquat injury. I do not think that irrigated growers need to worry about this issue since they can help the peanut plants recover from paraquat injury with well-timed irrigation events.
5) When paraquat + Storm/Basagran + Dual/Warrant/Zidua mixtures are applied in peanut, there is no need to be a great ID’er of weeds since these mixes control just about everything (small grasses and small broadleaf weeds). But, if a non-irrigated grower decides to go with something other than paraquat mixtures (which is fine), such as Ultra Blazer or Strongarm or Cadre or 2,4-DB, they better know what is in the field since these herbicides are not as broad spectrum. I am not comfortable with very early applications of Cobra unless the peanut plants have reached the 6 true leaf stage.
I also had a question on how long Dual Magnum (s-metolachlor) would wait on a rain. The answer is 7-10 days.