|Harrison Jr, Howard|
Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/30/1999
Publication Date: N/A
Interpretive Summary: Oxyfluorfen (Goal) herbicide is used extensively for weed control in cole crops (broccoli, cabbage, cauliflower, collard, kale, etc.). Cole crops have shown inconsistent response to oxyfluorfen. In some instances, excellent weed control and no crop injury was observed. In other instances severe crop injury and yield losses have been reported. Several reports indicated that tolerance differed by season or by location. This led us to think that temperature may affect oxyfluorfen tolerance in cole crops. Leaf wax content is widely assumed to be the mechanism of differences in oxyfluorfen response among cole crop varieties. However, this has not been documented by experiments. Thus, we conducted a growth chamber study to determine the role temperature and leaf waxiness had on the response of cole crops to oxyfluorfen. Cole crop varieties were more susceptible to injury by the herbicide at cool temperatures than at warm temperatures. Although there were large differences among varieties in leaf wax content, wax content did not appear to be directly related to oxyfluorfen tolerance. These studies suggest that the use rate of this herbicide should be lowered for cole crops planted in cool seasons. If the oxyfluorfen use rates were reduced for cool season crops, hundreds of thousands of dollars could be saved. Current losses occur from yield reductions and harvest delays due to oxyfluorfen injury. By reducing the rates applied in cooler seasons the total amount of herbicide used on cole crops will be reduced. The result that oxyfluorfen tolerance is not due to leaf wax content is of scientific interest because it differs from the commonly held belief.
Technical Abstract: Growth chamber studies were conducted to investigate the effect of ambient temperature and leaf wax content of the response of cole crops (broccoli and collard) to oxyfluorfen and on the differential response of tolerant and susceptible cultivars. Cole crop cultivars grown under cool temperatures (15/10 C) were more susceptible to preemergence (PRE) or postemergence (POST) application of oxyfluorfen, as quantified by injury rating and shoot weight reduction, than those grown under warm temperatures (25/20 C). Differences in PRE oxyfluorfen tolerance between cultivars were more distinct at warm temperatures than at cool temperatures. Although cole crop cultivars varied in leaf wax content and POST oxyfluorfen tolerance, differences in leaf wax content did not appear to be the most important genetic factor contributing to differences in tolerance.