Few postemergence (POST) herbicides are available for broad-spectrum weed control in pea. Field experiments were conducted to determine the suitability of imazamox to provide selective control of grass and broadleaf weeds in pea. Imazamox controlled several grass and broadleaf species, but the rate required to attain 90% control ranged from 7 to 36 g ai/ha depending on the weed species. Imazamox efficacy differed with the adjuvant included in the spray mixture. Merge adjuvant often increased imazamox activity on weeds more than Sun-It II methylated seed oil or a combination of Agral 90 adjuvant plus 28–0–0 liquid fertilizer. Pea exhibited excellent tolerance to imazamox up to the highest rate applied, 40 g/ha. Pea yield comparable to that of the hand-weeded control was attained with 20 to 30 g/ha of imazamox. Imazamox offers growers a POST option for broad-spectrum weed control in pea.

Herbicides were evaluated for weed control and crop response in conventional and no-tillage dry pea production. Preplant or preemergence (PRE) applications of imazethapyr, sulfentrazone, flumetsulam, cloransulam, and BAY FOE 5043 + metribuzin did not show crop injury within the locations, years, and tillage systems where applied. Postemergence applications of cloransulam had crop injury in excess of 60% where applied, and injury with flumiclorac and fomesafen ranged from 0 to greater than 40% with differences in crop injury as a result of dry pea growth stage at the time of application and surfactant use. Imazamox injury was as great as 24% when applied at a more advanced dry pea growth stage and was not different from 0% when applied at an earlier growth stage. Dry pea injury with bentazon was not significant, with an exception at one of the six locations where injury was 14%. Common lambsquarters was best controlled (80 to 90%) with sulfentrazone and imazamox. Preplant and PRE applications of sulfentrazone consistently provided the greatest mayweed chamomile control across tillage systems (control ranged from 59 to 93%), whereas bentazon provided the greatest postemergence (POST) control of mayweed chamomile (control ranged from 46 to 84%). Prickly lettuce control with preplant or PRE treatments was greatest with sulfentrazone (74 to 85%), whereas the greatest POST control was with imazamox in combination with urea-ammonium nitrate solution and surfactant or bentazon and crop oil concentrate (71 to 92%). Dry pea yields with herbicide treatments were not always greater than the nontreated and were often affected by crop injury.