TOLERANCE TO FOLIAGE-APPLIED HERBICIDES IN COMBINING PEAS - EFFECT OFGROWTH STAGE, CULTIVAR TYPE AND HERBICIDE

Field research was conducted over a 3-year period, 1988-1990, to evalu ate tolerance of two pea cultivars of different herbicide tank mixes, at different growth stages. Three tank mixes, cyanazine in combination with either bentazone, bentazone/MCPA or MCPB, each at two rates, wer e applied. The tank mix cyanazine plus bentazone/MCPA was the only com bination inducing severe injury to peas. Crop tolerance was greatest w hen herbicides were applied to peas at the one-node stage before the f irst leaves were unfolded. At later growth stages, which ranged from t he two-node stage and until the ten-node stage, a range of response wa s found. In general, the crop was better able to recover from damage b y a given herbicide if this was incurred early in development, than fr om damage at a late stage. Minor differences in crop tolerance to herb icides were found between a cultivar with normal developed leaflets an d a semi-leafless cultivar.