Rain delays and/or late planting have resulted in continual inquiries about peanut herbicide + fungicide tank-mixes and their potential effects on weed control and crop injury. UGA will never be able to adequately address all concerns with 90,000+ potential tank-mixtures in peanuts. Here is a quick review of some of the published data:
1) When 2,4-DB is tank-mixed with a postemergence graminicide, grass control can be reduced by 8% to 15% approximately 45% of the time.
2) When averaged across 5 grass species, Cadre (imazapic) + Select (clethodim) tank-mixtures provided 19% less effective grass control than Select alone.
3) Abound (azoxystrobin), Absolute (tebuconazole + trifloxystrobin), Bravo (chlorothalonil) and Headline (pyraclostrobin) are 4 fungicides that have caused significant grass antagonism when tank-mixed with Select (~12% to 30% reductions in grass control).
4) Grass efficacy with Poast (sethoxydim) and Select has not been consistently reduced by tebuconazole (various trade names including Folicur, Orius, TriSum, Integral, Ebustar, Muscle, Tebuzol). However, when reductions have been significant, grass control was reduced by 4% to 13% with tebuconazole mixes.
5) Palmer amaranth (PA) control was not reduced when 2,4-DB was tank-mixed with Bravo, Provost (prothioconazole + tebuconazole), Headline, or Absolute. But, 2,4-DB is not that great on PA anyway though?
6) Sicklepod control with 2,4-DB was reduced by 14% when applied with Abound but not with Bravo or tebuconazol