Optimizing efficacy of acetochlor + atrazine and dicamba at various doses to manage Conyza stricta L. in sugarcane

Abstract Background: Conyza stricta L. (Horse weed) is an annual problematic weed in an agricultural ecosystem and considerably decreases the crop yield and quality. Objective: To determine the most effective pre and post emergence herbicides and their dose to control C. stricta in sugarcane crop. Methods: A two years field study comprised of six herbicides treatments along with weedy check and hand weeding. The design of study was RCBD with three replications. Results: Hand weeding recorded more leaf area index (LAI), crop growth rate (CGR) and net assimilation rate (NAR), biological and stripped yield. However, greater LAI, CGR and NAR, biological and stripped yield were recorded by acetochlor + atrazine at the rate of 2,715 g ha-1 (pre emergence) and dicamba at the rate of 466 g ha-1 (post emergence). All the treatments produced statistically comparable harvest index except weedy check, which produced less harvest index. Minimum C. stricta density and dry weight were recorded for acetochlor + atrazine at the rate of 2,715 g ha-1 and dicamba at the rate of 466 g ha-1. Acetochlor + atrazine at the rate of 2,715 g ha-1 (pre emergence) and dicamba at the rate of 466 g ha-1 (post emergence) gave better C. stricta control with high herbicides efficiency index. Conclusion: Acetochlor + atrazine at the rate of 2,715 g ha-1 (pre emergence) or dicamba at the rate of 466 g ha-1 (post emergence) may be used for efficient control of C. stricta in sugarcane.

摘要 背景：直立白酒草（Conyza stricta L.，俗称Horse weed）是农业生态系统中的一年生恶性杂草，可显著降低作物的产量与品质。目的：明确可用于防控甘蔗田直立白酒草的最优芽前、芽后除草剂及其施用剂量。方法：本研究为为期两年的田间试验，共设置6种除草剂处理，另设空白杂草对照与人工除草处理。试验采用随机完全区组设计（RCBD, Randomized Complete Block Design），设置3次重复。结果：人工除草处理的叶面积指数（LAI, Leaf Area Index）、作物生长速率（CGR, Crop Growth Rate）、净同化速率（NAR, Net Assimilation Rate）、生物产量与剥茎产量均为最高。而施用剂量为2715 g·ha⁻¹的乙草胺+莠去津（芽前处理）与466 g·ha⁻¹的麦草畏（芽后处理），同样可获得较高的叶面积指数、作物生长速率、净同化速率、生物产量与剥茎产量。除空白杂草对照外，其余各处理的收获指数无统计学显著性差异，空白杂草对照的收获指数最低。施用剂量为2715 g·ha⁻¹的乙草胺+莠去津与466 g·ha⁻¹的麦草畏，对直立白酒草的种群密度与干物重抑制效果最佳。上述两种除草剂处理对直立白酒草的防控效果与除草剂效率指数均表现最优。结论：在甘蔗田中，可采用剂量为2715 g·ha⁻¹的乙草胺+莠去津（芽前施用）或剂量为466 g·ha⁻¹的麦草畏（芽后施用），以高效防控直立白酒草。