There is a limited number of herbicides available for weed control in adzuki bean production in Ontario, Canada. A total of six field trials were conducted in Ontario over a 2-yr period (2003 and 2004) to evaluate tolerance of adzuki bean to preplant incorporated (PPI) application of EPTC (4,400 and 8,800 g ai/ha), trifluralin (1,155 and 2,310 g ai/ha), dimethenamid (1,250 and 2,500 g ai/ha), S-metolachlor (1,600 and 3,200 g ai/ha), and imazethapyr (75 and 150 g ai/ha). All treatments, including the nontreated control, were maintained weed free during the growing season. EPTC and dimethenamid caused as much as 39% visual crop injury and reduced plant height, shoot dry weight, and yield up to 34, 63, and 38%, respectively. Maturity was delayed with the application of EPTC and dimethenamid. Trifluralin caused as much as 9% visual crop injury and decreased plant height up to 11%. There was no effect of trifluralin on shoot dry weight, seed moisture content, and yield. S-metolachlor caused as much as 19% visual crop injury, decreased plant height up to 23%, and reduced shoot dry weight up to 29%. Yield was not affected at the low rate but was decreased 19% at the high rate. There was no effect of S-metolachlor on maturity. Imazethapyr caused up to 6% visual injury but had no adverse effects on plant height, shoot dry weight, seed moisture content, and yield except at the high rate, which caused a 15% reduction in plant height. Based on these results, trifluralin and imazethapyr applied PPI have an adequate margin of crop safety for weed management in adzuki bean production in Ontario.

Nomenclature: Dimethenamid; EPTC; imazethapyr; S-metolachlor; trifluralin.

Additional index words: Adzuki bean, Vigna angularis.(Willd.) Ohwi and Ohashi ‘Erimo’; crop injury; tolerance.

Abbreviations: DAE, days after emergence; PPI, preplant incorporated.