ABSTRACT

The essential oil (EO) from different genotypes of Lippia gracilis Schauer (Verbenaceae) present two distinctive chemotypes containing either thymol or its isomer carvacrol as major compounds, both of which have proven bioactivity against several agricultural pests. Recently, we have shown that L. gracilis accession LGRA 106 and its major compound thymol are toxic and repellent against the coconut mite, Aceria guerreronis Keifer (Acari: Eriophyidae), a key pest of coconut plantations in Asia, Africa and America. Since intraspecific variation affects the chemical composition of EO and hence, its bioactivity, here we assessed the acaricidal and repellent effects of L. gracilis accession LGRA109 to A. guerreronis. Leaves of this accession contain carvacrol (49.35%) as major compound. The LC₅₀ of the EO and of carvacrol estimated for A. guerreronis were 28.01 and 6.84 mg/mL, respectively. Carvacrol, at its LC_50, as well as the EO and carvacrol at their LC_99, repelled the mite. Our results indicated that carvacrol and the EO of L. gracilis accession LGRA109 were bioactive against A. guerreronis; however, the EO was less effective than its major compound.

摘要

来自不同基因型的Lippia gracilis Schauer（马鞭草科）的精油 (EO)呈现出两种独特的化学型，其中含有百里酚或其异构体香芹酚作为主要化合物，两者均已证明对几种农业害虫具有生物活性。最近，我们已经证明L. gracilis种质 LGRA 106 及其主要化合物百里酚对椰子螨Aceria guerreronis Keifer（Acari：Eriophyidae）具有毒性和驱避作用，这是亚洲、非洲和美洲椰子种植园的主要害虫。由于种内变异会影响 EO 的化学成分，从而影响其生物活性，因此我们在这里评估了L. gracilis加入 LGRA109 对A. guerreronis的杀螨和驱虫效果. 该种质的叶子含有香芹酚 (49.35%) 作为主要化合物。估计A. guerreronis的 EO 和香芹酚的 LC ₅₀分别为 28.01 和 6.84 mg/mL。香芹酚的LC ₅₀以及 EO 和香芹酚的 LC _{99 都可以}驱除螨虫。我们的研究结果表明香芹酚和L. gracilis种质 LGRA109的 EO对A. guerronis 具有生物活性；然而，EO 不如其主要化合物有效。