Invasive knotweeds (Reynoutria spp.) pose an ongoing challenge for weed management programs worldwide, requiring years of persistent treatment. In this study, we tested efficacy of diquat applied as foliar spray early in the growing season for short-term suppression, and for potential to boost long-term control when applied sequentially with a mid-season treatment of imazapyr. We evaluated responses of knotweeds (R. japonica, R. × bohemica, and R. sachelinensis) treated with one of three diquat concentrations (0.25%, 0.50%, or 1.0%, v/v), using multiple metrics to capture changes in aboveground plant density and abundance. Canopy cover and biomass were significantly reduced by all diquat concentrations and resembled pre-treatment conditions at 8WAT, reflecting the shift toward reduced stem heights in treated compared with untreated plots. Stem counts at 8WAT, however, did not differ in response to diquat treatments. Sequentially applied early-season diquat and mid-season imazapyr treatments reduced canopy cover (66%–82%), biomass (65%–91%), and stem density (57%–79%) when evaluated 1 year after treatment; reductions were greatest in plots treated with medium and high diquat concentrations, suggesting that diquat treatments may have an additive effect. Overall, our study establishes rates of diquat to reduce biomass of invasive knotweed, and supports additional testing to assess improvement in long-term control when used sequentially with a systemic herbicide.

中文翻译：

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敌草快减少入侵虎杖的功效和比率以及与灭草烟序贯使用的潜力

入侵性虎杖（Reynoutria spp.）对全世界的杂草管理计划构成了持续的挑战，需要多年的持续治疗。在这项研究中，我们测试了敌草快在生长季节早期叶面喷施的短期抑制功效，以及与季中灭草烟连续施用时增强长期控制的潜力。我们评估了虎杖（R. japonica、R. × bohemica和R. sachelinensis ）的反应）用三种敌草快浓度（0.25％、0.50％或1.0％，v/v）之一处理，使用多种指标来捕获地上植物密度和丰度的变化。所有敌草快浓度均显着降低了冠层覆盖度和生物量，并且与 8WAT 的预处理条件相似，反映出与未处理地块相比，处理过的地块茎高度向降低的方向转变。然而，8WAT 时的茎计数对敌草快处理的反应没有差异。处理后一年进行评估时，依次施用早季敌草快和中季灭草烟处理降低了冠层覆盖度（66%–82%）、生物量（65%–91%）和茎密度（57%–79%）；在用中等和高浓度敌草快处理的地块中，减少幅度最大，表明敌草快处理可能具有累加效应。全面的，