Chemical control of signalgrass for establishing Tanzania-grass

ABSTRACT. Herbicides have been used to control Brachiaria grass in pastures established or in formation given their practicality, however their efficiency is questionable due to the lack of specific graminicides for different forage species. Therefore, the goal of this study was to evaluate the efficiency of glyphosate and fluazifop-p-butyl in the control of Brachiaria decumbens (signalgrass) and the intoxication levels of Panicum maximum cv. Tanzania (Tanzania quinea grass) in pasture establishment. The experiments were designed in randomized blocks, in a 2 × 5 × 4 factorial arrangement of two herbicides (fluazifop-p-butyl and glyphosate), five doses equivalent to the commercial dosage of each herbicide (0.25; 0.50; 1.00; 1.50; 200), and four evaluation times after herbicide application (15, 21, 30 and 45 days). There was interaction between doses and evaluation times. The dose 1.5 L ha-1 fluazifop-p-butyl provides efficient control of signalgrass, however, leads to high intoxication in Tanzania guinea grass. Glyphosate is efficient in the control of signalgrass even at the lowest dose (90 g ha-1), however, it causes high intoxication in Tanzania guinea grass, preventing its use in developing pastures. It can be concluded that fluazifop-p-butyl and glyphosate herbicides are not recommended for the control of B. decumbens, cv. Basilisk in developing pastures of Tanzania guinea grass.

摘要：鉴于操作便捷性，除草剂已被用于防控已建植或在建牧场上的臂形草（Brachiaria grass），但其防控效果尚存争议，原因是缺乏针对不同饲草物种的专用禾本科除草剂。为此，本研究旨在评估草甘膦（glyphosate）与精吡氟禾草灵（fluazifop-p-butyl）对俯仰臂形草（Brachiaria decumbens，又名信号草signalgrass）的防控效果，以及其对坦桑尼亚品种大黍（Panicum maximum cv. Tanzania，又名坦桑尼亚几内亚草Tanzania guinea grass）的药害程度，以支撑牧场建植阶段的相关研究。本试验采用随机区组设计，设置2×5×4三因素析因排列：2种供试除草剂（精吡氟禾草灵与草甘膦）、5种按各自商品用量折算的施药梯度（0.25、0.50、1.00、1.50、200），以及施药后4个调查时间点（15、21、30和45天）。研究发现，施药剂量与调查时间点之间存在显著交互作用。施用量为1.5 L·ha⁻¹的精吡氟禾草灵可有效防控信号草，但会对坦桑尼亚几内亚草造成严重药害。即便以最低剂量（90 g·ha⁻¹）施药，草甘膦仍可有效防控信号草，但同样会对坦桑尼亚几内亚草造成严重药害，使其无法应用于在建牧场的杂草防控工作。综上，在坦桑尼亚几内亚草的在建牧场中，不推荐使用精吡氟禾草灵与草甘膦防控巴西利斯克型俯仰臂形草（B. decumbens cv. Basilisk）。