Early Harvest Aid Application Approach to Pima Cotton Defoliation
Chemical defoliation is a necessary pre-harvest practice in Pima cotton (Gossypium barbadense L.) production. Cotton growers are advised to begin defoliation as early as possible with both Pima and Upland cotton, but not so early that it results in yield and quality loss. California Pima’s potentially harvestable bolls often fail to reach full maturity for the recommended defoliation timing. Applying harvest aids before the recommended maturity can advance the start of harvest, avoiding late-season pests and adverse weather that can damage lint quality. The objective of this research was to compare different rates of Ginstar ® (thidiazuron/diuron, Ginstar plus Finish ® (ethephon/cyclanilide, on defoliation, yield, and fiber quality of Pima cotton when applications began at an earlier 6 to 7 NACB (nodes above cracked boll) timing versus the common 4 to 5 NACB timing. ‘Delta Pine DP-340’ and ‘Phytogen 802’ were treated with harvest aid materials in field trials and were analyzed as a factorial split-plot design with four replications. Starting the defoliation of Pima at 6 to 7 NACB rather than 4 to 5 NACB brought about a potential 7 to 10 day earlier harvest and did not significantly affect yield or cotton fiber quality characteristics except for micronaire in some years of the study. These data indicate that earlier defoliation could be beneficial when later-maturing crops or worsening harvest-season weather necessitate the initiation of an earlier harvest.