Abstract

Plants produce arrays of secondary metabolites that act synergistically to deter and/or intoxicate herbivores. In this study, we evaluated the toxicity of piperine and β-asarone, individually and in binary mixtures, to examine their synergistic effects against larvae of two generalist herbivores, Spodoptera litura and Mythimna separata. Acute toxicity of piperine after topical application was lower than that of β-asarone for second instar larvae of both S. litura and M. separata (LD₅₀ 53.65 and 7.52 µg/larva, respectively, after 24 h). However, all mixtures produced synergistic, antifeedant effects. Mixtures of either 56.65 or 7.52 µg/larva of piperine + 18 µg/larva of β-asarone were highly synergistic in term of their acute toxicity (synergistic factor 11 and 44 for S. litura and M. separata, respectively). The more concentrated mixture also had the strongest antifeedant effects when presented on artificial diet to both species, S. litura and M. separata (56.64% and 62.30% at 24 h, respectively). Our results suggest that the combination of piperine and β-asarone is a greater deterrent than either pure compound alone. Use of this mixture may provide better crop protection rather than that offered by single compounds for controlling lepidopteran pests.

摘要

植物产生一系列次生代谢物，这些代谢物协同作用以阻止和/或毒害食草动物。在这项研究中，我们评估了胡椒碱和 β-细辛醚单独使用和以二元混合物形式使用的毒性，以检验它们对两种通才食草动物斜纹夜蛾和粘虫的幼虫的协同作用。胡椒碱外用后对斜纹夜蛾二龄幼虫的急性毒性低于β-细辛脑（LD ₅₀24 小时后分别为 53.65 和 7.52 µg/幼虫）。然而，所有混合物都产生了协同的拒食效果。56.65 或 7.52 µg/幼虫胡椒碱 + 18 µg/幼虫 β-细辛酮的混合物在急性毒性方面具有高度协同作用（分别为斜纹夜蛾和M. separata的协同因子 11 和 44 ）。当以人工饲料呈现给斜纹夜蛾和M. separata两种物种时，浓度更高的混合物也具有最强的拒食效果（24 小时时分别为 56.64% 和 62.30%）。我们的结果表明，胡椒碱和 β-细辛脑的组合比单独使用任何一种纯化合物具有更大的威慑力。使用这种混合物可以提供比单一化合物更好的作物保护来控制鳞翅目害虫。