Responses of Some Sugarcane Varieties to Standard and Combination Ripener Treatments

The effects on sucrose yield of varying the time interval between Ethrel and Fusilade Super applications in a combination treatment were tested on variety NC0376. Results suggested that Ethrel applied 12 weeks, and Fusilade Super applied eight weeks before harvesting were the most beneficial. Other varieties which responded to a combination treatment were N19, N12 and N22. Varieties N14, N19, N17, N12, N22 and NC0376 grown under irrigation all responded to one of the ripener treatments, and their responses to Ethrel and Fusilade Super are discussed. There were no significant gains in sucrose yield of CP66/1043 in response to the ripeners although sucrose content was increased. Introduction The firstrecords oftwo ripeners being applied in sequence to the same cane in southern Africa are of experiments conducted at the South African Sugar Association Experiment Station during 1977 (Anon., 1978). An experiment in which Mon 8000 (Polado) was applied to cane which previously had been sprayed with ethephon (Ethrel) or Embark, gave encouraging results. Following the registration of fluazifop (Fusilade Super) as a ripener in South Africa, Rostron (1985) tested this concept with Ethrel followed by Fusilade Super. Comparing commercially ripened fields in Swaziland, Sweet et al. (1987) reported excellent results from combining Ethrel and Fusilade, stating that the individual benefits are 'additive' when the chemicals are applied in sequence. The combination treatment soon became commercial practice on NC0376 in Swaziland, and Leibbrandt (1989) verified that responses to the combination treatment were additive on NC0376, but not on N14. The poor responses ofNl4 to the combination treatment were attributed to the lack of response of this variety to Ethrel. In a comparison of ripeners conducted in Cuba on six varieties, Cutino et al. (1992)found that Fusilade Super and glyphosate (Roundup) applied individually were economically more favourable than the combination of Ethrel + Fusilade Super. Three of the experiments reported here were conducted on NC0376 to assess the effects of varying the interval between applying Ethrel and Fusilade Super. A combination treatment and lone applications ofEthrel and Fusilade Super were tested in two experiments on N19, N12, CP66/1043 and N22. Responses of NC0376, N14, Nl7 and Nl9 to standard Ethrel and Fusilade Super treatments were also tested in two experiments. Treatments and Methods Three combination treatments, in which the time of applying Fusilade Super was varied following Ethrel application, were compared with Ethrel alone (experiment I) or Ethrel and Fusilade Super alone (experiments II and III). In experiments IV and V Ethrel and Fusilade Super were applied about twelve and eight weeks respectively before har-