The potential of imazethapyr as a selective herbicide in four pulse crops was investigated at Melfort, Saskatchewan in 1988 and 1989. Lentil, field pea, faba bean and annual vetch were tolerant to imazethapyr applied preemergence to a silty clay loam soil at 0.05, 0.10, 0.15, and 0.20 kg ai ha-1. Postemergence treatments above 0.05 kg ha-1, however, stunted lentil and vetch in both years. Environmental factors, the dominant weed in the experimental site, as well as timing of application strongly influenced the performance of imazethapyr. Seed yield increases observed with imazethapyr treatments, compared to metribuzin or untreated check, were greater in 1989 when wild oat was the dominant weed and moisture was not a limiting factor in the early stages of crop development, than in 1988 when field pennycress was the dominant weed. Mean seed yield for all imazethapyr treatments, compared to the check, increased 0 and 930%, 24 and 89%, 21 and 600%, and 47 and 44% in 1988 and 1989, for lentil, field pea, faba bean and vetch, respectively. Significant increases in lentil seed density, seed size, and germination were also obtained though protein content decreased 2%.

Response of flax, canola, field pea, sunflower, field corn, lentils, and common buckwheat to soil residues of CGA-131036 and chlorsulfuron applied at 22 g ai ha–1 was determined on two soil types at Morden, Manitoba. on a fine sandy loam with a pH of 7.4 and 4.5% organic matter, the length of time required before crops showed no phytotoxicity from CGA-131036 residues was: sunflower 4 yr; canola and common buckwheat 3 yr; flax 2 yr; field pea and field corn 1 yr. on a clay loam with a pH of 6.5 and 5.3% organic matter, the corresponding duration was: lentil, canola, and sunflower 3 yr; flax and field pea 1 yr. Chlorsulfuron residues persisted somewhat longer than CGA-131036 residues on the sandy loam but not on the clay loam.