Response of white bean (Phaseolus vulgaris) to imazethapyr

Tolerance of white bean to the pre-emergence application of imazethapyr at the dose of 0, 25, 50, 75, 150 and 300 g ai ha−1 was studied at 11 Ontario, Canada locations over a 3-year period. White bean tolerance to imazethapyr was dependent on dose and environmental conditions. Crop injury generally increased as the dose was increased. Imazethapyr-applied pre-emergence caused up to 62% visible injury and reduced plant height as much as 32%, shoot dry weight 48%, root dry weight 20% and yield 77%. Seed moisture content was increased as much as 1.1%. The dose of imazethapyr to cause 5%, 10% and 20% injury in white bean was as low as 17, 31 and 58 g ai ha−1 for visible injury, 36, 73 and 155 g ai ha−1 for plant height, 4, 9 and 22 g ai ha−1 for shoot dry weight, 27, 54 and 108 g ai ha−1 for root dry weight, and 10, 21 and 44 g ai ha−1 for yield, respectively. Leaf tissue potassium (K) concentration was not affected with imazethapyr at 25, 50 and 75 g ai ha−1; however, it was reduced 27% at 150 g ai ha−1 and 36% at 300 g ai ha−1. Based on these results, imazethapyr-applied pre-emergence at the currently registered dose of 75 g ai ha−1 in white bean in Ontario has the potential to cause significant crop injury and yield losses under some environmental conditions.