Insecticidal Activities of Plant Essential Oil Compounds Showing Juvenile Hormone Agonist or Antagonist Activity

Abstract

Pests cause huge economic damages not only by harming crops or livestock production but also transmitting vector borne diseases like malaria, yellow fever and dengue fever. To control pests, chemical insecticides like organophosphates, carbamates, pyrethroids have been commonly used. However, use of chemical insecticides faced several limit such as environmental threat or resistance. Insect growth regulators (IGRs) are attractive alternative pesticides due to their low environmental toxicity and high specificity. Plant essential oils have been reported to show repellent, insecticidal and growth-reducing effect on many insect herbivores. Recently, it has been reported that plants synthesize secondary metabolites regulating insect juvenile hormone (JH) receptor complex as a part of their defense mechanisms. In this study, 195 plant essential oil compounds were tested for their JH agonist and antagonist activities using a yeast two-hybrid system transformed with the Aedes aegypti JH receptor as a reporter system. Among them, 17 compound that showing high JH agonist (JHA) or antagonist (JHAN) activities were identified. They were grouped into 4 groups by their structural similarity. Their insecticidal activity and nematicidal activity were tested against Aedes albopictus, Plutella xylostella, Plodia interpunctella, Laodelphax striatellus and Bursaphelenchus xylophilus. Against A, albopictus 3rd instar larvae, 5 Plant essential oil compounds showed over 70% mortality at 10 ppm. Against 3rd instar larvae of P. xylostella, undecyl aldehyde indicated over 80% mortality at 200ppm. Against P. interpunctella, nerolidol showed over 80% mortality against 2nd instar larvae and undecyl acetate showed reduced egg hatching rate. Also benzyl sulfide, benzyl disulfide, benzyl trisulde and dodecyl aldehyde showed nematicidal activity against B. xylophilus. These results could provide insights on the plant-insect coevolution and may be useful for the development of insect specific and safe pesticides.