Evaluation of vetiver oil and seven insect-active essential oils against the formosan subterranean termite

Repellency and toxicity of 8 essential oils (vetiver grass, cassia leaf, cl ove bud, cedarwood, Eucalyptus globules, Eucalyptus citrodora, lemongrass a nd geranium) were evaluated against the Formosan subterranean termite, Copt otermes formosanus Shiraki. Vetiver oil proved the most effective repellent because of its long-lasting activity. Clove bud was the most toxic, killin g 100% of termites in 2 days at 50 mug/cm(2). The tunneling response of ter mites to vetiver oil also was examined. Vetiver oil decreased termite tunne ling activity at concentrations as low as 5 mug/g sand. Tunneling and paper consumption were not observed when vetiver oil concentrations were higher than 25 mug/g sand. Bioactivity of the 8 oils against termites and chemical volatility were inversely associated. Listed in decreasing order of volati lity, the major constituents of the 8 oils were: eucalyptol, citronellal, c itral, citronellol, cinnamaldehyde, eugenol, thujopsene, and both alpha- an d beta -vetivone. Vetiver oil is a promising novel termiticide with reduced environmental impact for use against subterranean termites.