Kenaf tolerance to acifluorfen, cyanazine, diuron, fluometuron, fomesafen, lactofen, or prometryn applied postemergence-directed

Abstract

Field experiments were conducted in 1993 (Dundee clay loam, 1.8% OM, pH 6.2), and 1994 (Tunica clay loam, 1.8% OM, pH 5.5) to evaluate kenaf ( Hibiscus cannabinus L.) tolerance to acifluorfen (0.42, 0.56, and 0.84 kg ai ha −1), cyanazine (0.89, 1.2, and 1.8 kg ai ha −1), diuron (0.67, 0.89, and 1.3 kg ai ha −1), fomesafen (0.42, 0.56, and 0.84 kg ai ha −1), fluometuron (1.12, 1.45, and 2.24 kg ai ha −1), lactofen (0.22, 0.29, and 0.45 kg ai ha −1) or prometryn (0.56, 0.73, and 1.12 kg ai ha −1), applied postemergence-directed. Herbicides were applied with a compressed air spray system calibrated to deliver 187 1 ha −1 of spray solution. Four-row plots (3 × 6 m) were simultaneously cultivated and sprayed. Herbicides were directed towards the base of kenaf plants which were 30 to 35 cm tall in 1993 and 35 to 51 cm tall in 1994. X-77 ® (0.25% v v ) was used as an adjuvant in 1993 for all treatments. In 1994, Agri-Dex ® (1.0% v v ) was used with diuron and fomesafen and Latron, AG-98 ® (0.25% v v ), was used with all other herbicides. All rates of diuron or fomesafen caused kenaf injury (necrosis) but did not exceed 22 and 14%, respectively. Only fomesafen at the highest rate resulted in kenaf height reduction 24 days after treatment (DAT). All injury symptoms disappeared as leaves abscised and no visual injury symptoms were observed either year by mid season. Kenaf was defoliated in the fall of each year and 5.3 m of the center two rows was hand-harvested at ground level. No treatment caused yield reductions when compared to the untreated control except the high rate of diuron in 1994.