Weed control in white beans is currently limited by the small number of registered herbicides. The tolerance of two white bean cultivars, ‘AC Compass’ and ‘OAC Thunder’, to various postemergence (POST) herbicides at the maximum use rate and twice the maximum use rate for soybean or corn was evaluated at two Ontario locations in 2001 and 2002. Generally, the two cultivars did not differ in their response to the POST herbicides. POST applications of imazamox plus fomesafen, imazamox plus bentazon, and cloransulam-methyl decreased plant height, shoot dry weight, and yield by as much as 29, 41, and 55%, respectively, and increased seed moisture content up to 3.9%. POST applications of thifensulfuron, chlorimuron, and bromoxynil decreased plant height as much as 57%, shoot dry weight by up to 71%, yield as much as 93% and increased seed moisture content up to 15.5%. Based on these results, AC Compass and OAC Thunder white beans do not possess sufficient tolerance to support the registration of imazamox plus bentazon, imazamox plus fomesafen, cloransulam-methyl, thifensulfuron, chlorimuron, and bromoxynil.

Nomenclature: Bentazon; bromoxynil; chlorimuron; cloransulam-methyl; fomesafen; imazamox; thifensulfuron; corn, Zea mays L.; soybean, Glycine max (L.) Merr.; white bean, Phaseolus vulgaris L. ‘AC Compass’, ‘OAC Thunder’.

Additional index words: Crop tolerance, herbicide injury, postemergence herbicides, seed moisture content, white beans, yield.

Abbreviations: DAP, days after planting; DAT, days after treatment; POST, postemergence.