REINVESTIGATING ADJUVANTS FOR THE WILD OAT HERBICIDE, FLAMPROP-M-ISOPROPYL .2. FIELD PERFORMANCE

A field trials programme was conducted in which the performance of a n ew emulsifiable concentrate formulation (ECI) of flamprop-M-isopropyl containing the adjuvant, 'Dobanol' 25-7, in a ratio of 2:1 (by weight) with the AI, was compared with the current commercial formulation of 'Commando,' in combination with its recommended adjuvant, 'Swirl', for the control of wild oat (Avena fatua L.) in wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.). A further treatment, in which the 'Dobanol' 25-7: AI ratio was increased to 4:1 by the spray tank addit ion of the former, was also included. The mean results from six trials (five wheat, one barley) showed that the addition of 'Swirl' to 'Comm ando' was beneficial, increasing wild oat floret control from a mean v alue of 80% to 92% at current recommended rates (flamprop-M-isopropyl, 600 g ha-1; 'Swirl', 2.5 litre ha-1). However, combinations of flampr op-M-isopropyl and 'Dobanol' 25-7 gave superior levels of control even at lower AI application rates. For example, a mean level of 96% contr ol of Avena spp. was obtained at 300 g AI ha-1 with 1200 g ha-1 'Doban ol' 25-7 with even better control at higher rates of application of bo th components. This improvement in performance was accompanied by a hi gher risk of crop phytotoxicity than observed with the 'Commando'/'Swi rl' mixtures. Symptoms initially were scorch and subsequently growth d epression, particularly of tillers. None of the mean values in the six 'efficacy' trials reached commercially unacceptable levels, but in a further six 'crop effects' trials (three wheat, three barley), in whic h double rates were applied, the levels of phytotoxicity did become un acceptable and subsequently reduced grain yields. In contrast, two bar ley 'crop effects' trials gave yields higher than the control plots, p ossibly through the effects of reducing stem length and lodging thereb y enabling more efficient harvesting. Nevertheless, there were rates o f application of flamprop-M-isopropyl in the range 300-400 g ha-1 with ratios of 'Dobanol' 25-7 in the range 2:1 to 4:1 that would achieve h igh levels of control of Avena spp. without undue risk of crop phytoto xicity and further trials are planned to support this new adjuvant sys tem.