Submitted to: National Meeting of Entomological Society Of America
Publication Type: Abstract only
Publication Acceptance Date: 7/23/2009
Publication Date: 12/13/2009
Citation: Ranger, C.M., Reding, M.E., Oliver, J. 2009. Acute Toxicity of Essential Oils to Japanese Beetle Larvae and their Corresponding Mass Spectral Analysis. National Meeting of Entomological Society Of America, December 13-16, 2009, Indianapolis Indiana. Interpretive Summary:
Technical Abstract: The root-feeding larvae of the Japanese beetle, Popillia japonica Newman have traditionally been viewed as contaminant pests of field-grown nursery crops. However, increasing attention is being paid to the deleterious effects of root herbivory by white grubs, which can cause girdling of roots and eventual stunting or death of nursery crops. The consistent deregistration of conventional insecticides warrants the pursuit of user and environmentally friendly alternatives. Botanically based formulations represent a sustainable alternative to synthetic insecticides. In order to develop an optimal blend of extracts, the current study was undertaken to determine the toxicity and composition of selected essential oils to Japanese beetle larvae. Twenty two essential oils were purchased from Simplers Botanical Co. (Sebastopol, CA) and serial dilutions were made using acetone. A Burkhard microapplicator was used to topically apply one µl of each formulation to the dorsal thorax of 3rd instar P. japonica. A wide range in toxicity was associated with oils. Thyme and white pepper were the two most toxic oils tested against P. japonica, while the individual component eugenol was also comparatively toxic. Gas chromatography-mass spectrometry determined thymol was the major component of the two most active oils, namely, red thyme and white pepper. Cymene, linalool, and terpinen-4-ol were minor components common among both oils. Eugenol, citronellal, cinnamaldehyde and citronet were major components of clove, citronella, cinnamon leaf, and geranium/rose oils, respectively. These results demonstrated that individual chemical components must be considered for developing optimum blends of botanical formulations. Furthermore, it appears that high concentrations of nontoxic oils in botanical formulations, such as sesame and soya oils, likely improves cuticular penetration of insecticidal oils. Synergism studies among the most toxic oils and their components are currently in progress.