DIFFERENTIAL TOLERANCE OF BROCCOLI (BRASSICA-OLERACEA) CULTIVARS TO PREEMERGENCE APPLICATION OF OXYFLUORFEN

The tolerance of 10 broccoli cultivars to preemergence (PRE) applicati ons of oxyfluorfen was evaluated in greenhouse and field experiments. Differences in tolerance among cultivars were expressed as differences in seedling injury ratings and growth and stand reduction. The cultiv ars 'Pinnacle' and 'Mercedes' were most tolerant, 'Embassy' and 'Early Dawn' were least tolerant, and other cultivars were intermediate in t olerance. Broccoli seedling weights and stand counts averaged across 1 0 cultivars and oxyfluorfen application rates of 0.125, 0.25, and 0.5 kg/ha were 70 and 81% of control, respectively. for the two fall-plant ed experiments and 39 and 50% of control, respectively, for the spring -planted experiment. Differences in tolerance among cultivars were les s distinct in the cooler spring than in the warmer fall season. Oxyflu orfen application that caused stand and early growth reduction did not always affect broccoli head weight or quality or delay harvest.