Ethoxylated rapeseed oil derivatives as non-ionic adjuvants for glyphosate

In a study aimed at finding environmentally benign adjuvants for glyphosate, ethoxylates of rapeseed oil and of methylated rapeseed oil were synthesized, with ethylene oxide (EO) content up to 40 and 8 respectively. They had less influence on spray retention by barley shoots than ethoxylated (15 EO) tallow amine (ETA). At 10 g L(-1), ethoxylated rapeseed oil with 30 or 40 EO and ethoxylated methylated rapeseed oil with 6 or 8 EO promoted glyphosate uptake by barley leaves to a greater extent than ETA at the same concentration. However, uptake rates were similar when the concentration was lowered to 2.8 and 3.1 g L(-1) for rapeseed oil derivatives and ETA respectively. In the case of ethoxylated methylated rapeseed oil with 8 EO (MeOil-8), glyphosate uptake increased when MeOil-8 concentration was raised from 5 to 10 g L(-1). In bioassays under controlled conditions, ethoxylated rapeseed oil with 40 EO (Oil-40) and MeOil-8 were slightly less effective than ETA in favouring the efficacy of glyphosate on barley. The same was found on ryegrass. However, both rapeseed oil derivatives compared well with glyphosate formulants such as ethoxylated diethylamine and alkyl ethoxy phosphate. In one field experiment, the efficacy of glyphosate in the presence of Oil-40, MeOil-8 or ETA was comparable with that of a commercial formulation. In another trial, MeOil-8 was as effective as ETA, but Oil-40 performed less well. It is concluded that ethoxylates of rapeseed oil and of methylated rapeseed oil are a promising chemistry for glyphosate adjuvants, provided that their ethylene oxide content is high.