Evaluation of Trinexapac-ethyl (Moddus®) as a New Chemical Ripener for the South African Sugarcane Industry

Abstract

Although information from Brazil and Australia indicate that trinexapac-ethyl (Moddus®) is an excellent new sugarcane ripener, there is no information on the response of South African varieties to this chemical. The objective of this investigation was to establish the ripening potential of this chemical in a local variety and to compare responses with current industry standards, 2-chloroethyl phosphonic acid (Ethephon®) and fluazifop-p-butyl (Fusilade Forte®). Evaluation was conducted in an irrigated plant and first ratoon crop of variety N32 at Pongola, South Africa. The field trial was laid out as a complete randomised design with five replicates per treatment. The nine treatments comprised: (a) untreated control, (b) Ethephon® (1.5 L/ha) applied 84 days before harvest (DBH), (c) Fusilade Forte® (0.2 L/ha) applied 43 DBH, (d) Moddus® at three rates (0.8, 1 and 2 L/ha) applied 70 DBH, (e) Ethephon® (1.5 L/ha) and Fusilade Forte® (0.2 L/ha) applied in combination 84 and 43 DBH, and (f) Moddus® (0.8 and 1 L/ha) and Fusilade Forte® (0.2 L/ha) applied in combination 70 and 43 DBH. The various ripener treatments improved estimated recoverable crystal (ERC) yields in the 12-month old crops by between 1.6 and 4.9 t/ha when compared with the control. Moddus® applied at 0.8 and 1 L/ha achieved similar improvements as Fusilade Forte® and Ethephon®, but at 2 L/ha outperformed the latter two ripeners by up to 1.9 t ERC/ha. Best ERC yield responses were achieved in the three combination treatments. However, the Moddus®—Fusilade Forte® combination treatments outperformed the standard Ethephon®—Fusilade Forte® combination treatment by up to 1 t ERC/ha. These results indicate that Moddus® is an effective sugarcane ripener under South African high-potential irrigated conditions and that improved in ERC yields exceeding those obtained with current industry standards might be possible.