Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: September 22, 1997
Publication Date: N/A
Technical Abstract: The IR-4 project is conducting research to register metolachlor for use in direct-seeded and transplanted cole crops. The feasibility of using preemergence application of metolachlor for weed control in direct-seeded collard and kale was evaluated by assessing the response of eight collard and three kale cultivars in greenhouse and field studies. The lowest rates tested, 0.75 kg /ha in the greenhouse and 1.5 kg/ha in the field caused significant injury and reduced seedling weights; however, yield was reduced in the field at rates of 3.0 and 6.0 kg/ha only when seedling injury and seedling weight reduction were severe. Differences between cultivars in metolachlor tolerance were expressed as differences in injury ratings and seedling shoot weight reduction in the greenhouse and field. Shoot weights of the most tolerant cultivar, Flash were not reduced at metolachlor rates that reduced the weights of the least tolerant cultivar, Georgia. These studies indicate that metolachlor at rates of 1.5 kg/ha or lower can be used safely for weed control in direct-seeded collard and kale if susceptible cultivars are avoided. The observation of differential tolerance in a relatively small group of cultivars suggests that metolachlor tolerance of cole crop cultivars should be evaluated to avoid losses that could occur if the herbicide is used on highly susceptible cultivars.