Efficacy of pendimethalin and cyhalofop-butyl + penoxsulam against major grass weeds of direct-seeded rice

Abstract

Direct-seeded rice (DSR) helps in saving water and is beneficial for soil physical health along with environmental benefits, but weeds poses a serious threat to efficient crop production. In the absence of ponded water, weeds emerge in several flushes making it difficult to manage them with a single pre- or postemergence herbicide application. Studies were carried out under the screen house conditions at CCS Haryana Agricultural University, Hisar, where the response of four dominant grass weeds of direct-seeded rice, viz. Echinochloa glabrescens, Leptochloa chinensis, Eragrostis japonica and Dactyloctenium aegyptium was evaluated against pendimethalin and cyhalofop-butyl + penoxsulam mixture. The four grassy weed species were planted in pots replicated four time with 20 seed per plot. Pendimethalin was applied as preemergence at 0.25, 0.5, 1.0 and 2.0 kg/ha and cyhalofop-butyl + penoxsulam mixture was sprayed as post-emergence (PoE) (at 25 days after sowing) at 32.5, 65, 135 and 270 g/ha with the help of knapsack sprayer and control pots were maintained for each species and herbicides. Periodical observations on visual mortality (0–100 scale, where 0 = no effect and 100=complete mortality) and dry weight per pot was observed at harvest. Application of pendimethalin at 1.0 kg/ha resulted in excellent control of L. chinensis and D. aegyptium, whereas at 2.0 kg/ha application rate killed all the weeds. Cyhalofop-butyl + penoxsulam applied at 270 g/ha showed 100% mortality of E. glabrescens and L. chinensis. However, the highest rate (270 g/ha) of this mixture had no effect on E. japonica, and provided only 20% control of D. aegyptium. Results of this study suggest that pendimethalin can be used for managing E. glabrescens, L. chinensis, E. japonica and D. aegyptium. However, cyhalofop-butyl + penoxsulam can be used as PoE in fields dominated by E. glabrescens and L. chinensis.