Five sweet corn cultivars were evaluated for tolerance to bentazon in five field experiments conducted during 2 yr in Ontario. Bentazon was applied postemergence (POST) at 1.08 and 2.16 kg ai/ha, the highest registered rate and twice the highest registered rate, respectively, used in sweet corn in Ontario. When bentazon was applied POST at 1.08 and 2.16 kg/ha to sweet corn cultivar ‘DelMonte 2038’, injury included plant stunting and leaf damage ranging from 6 to 69% and 15 to 90%, respectively. Plant height was reduced to 48 and 100% of the untreated check when treated with bentazon at 1.08 and 2.16 kg/ha, respectively. The visual injury and height reductions were reflected in the marketable yields, which were reduced to 94% when treated with bentazon. Significant reductions in height and marketable yield were not observed in the other four cultivars tested. No correlation was observed between bentazon sensitivity and endosperm genotype. Based on visual injury ratings, sweet corn height, and marketable yield, it was concluded that ‘Calico Belle’, ‘GH 2684’, ‘Reveille’, and ‘Rival’ are tolerant to POST application of bentazon.

Nomenclature: Bentazon; sweet corn, Zea mays L. ‘Calico Belle’, ‘DelMonte 2038’, ‘GH 2684’, ‘Reveille’, ‘Rival’.

Additional index words: Cultivar tolerance, herbicide injury, photosystem II–inhibiting herbicide.

Abbreviations: DAT, days after treatment; POST, postemergence.