Sugarcane (Saccharumspp. hybrids) Tolerance to Clomazone

Field studies were conducted over four years to determine sugarcane response to clomazone applied POST at 1.1 and 2.2 kg ai/ha. Sugarcane leaves present when clomazone was applied were chlorotic 2 WAT. Injury 4 WAT ranged from 0 to 38% following single applications in March and April. Chlorosis 4 wk after the May application of a March plus May sequential treatment was only greater than for the single March application in 1992. The number of harvestable sugarcane stalks following treatments with clomazone was intermediate between those produced with standard applications of either metribuzin at 2.6 kg ai/ha (least injurious) or terbacil as a single treatment at 1.8 kg ai/ha in March and April or as a 1.8 plus 0.9 kg/ha March plus May sequential treatment. Sugar recovery as an average of all herbicide treatments was lower for the sequential applications than for the single applications. Averaged over single and sequential treatments, theoretically recoverable sugar levels with clomazone at both rates was intermediate between the recoveries obtained with standard applications of metribuzin (highest) and terbacil. Gross cane and sugar yields following all applications of clomazone at 1.1 kg/ha and following single applications of clomazone at 2.2 kg/ha in March and April were similar to the metribuzin standard. Sugar yields following the sequential treatment of clomazone at 2.2 kg/ha, although lower than the metribuzin standard, were similar to the standard terbacil sequential treatment.