Response of broccoli (Brassica oleracea) cultivars to post-transplant oxyfluorfen

Broccoli cultivars were evaluated for differential response to oxyfluorfen applied postemergence (0.1 to 1.6 kg ai/ha) in the greenhouse and post-transplant (0.125 to 1.0 kg/ha) in a spring and a fall field study. One cultivar, 'Green Goliath,' was injured more by oxyfluorfen than other cultivars in all environments. 'Pinnacle,' was consistently less injured than others. 'Early Dawn' and 'Emerald City' were intermediate in response to oxyfluorfen. At application rates of 0.25 kg/ha or less, all cultivars recovered sufficiently from injury to produce broccoli heads of equal weight and quality as controls. Cultivars differed in their tolerance of oxyfluorfen at rates above 0.25 kg/ha. Late-maturing cultivars (i.e., Pinnacle) usually recovered from injury to yield similarly to hand-weeded plots while early-maturing cultivars were more likely to show yield losses. Broccoli cultivars possess sufficient tolerance to oxyfluorfen applied post-transplant for weed control. Appropriate choice of cultivar will enhance its utility.