Acaricidal activity and repellency of essential oil from Piper aduncum and its components against Tetranychus urticae

The chemical composition of essential oil of leaves of L., growing wild in a fragment of the Atlantic Rainforest biome in northeastern Brazil, was determined through gas chromatography-mass spectrometry. The acaricidal activity and repellency of the essential oil and its components [dillapiole (0.28 g/ml), alpha-humulene (0.016 g/ml), ()-nerolidol (0.0007 g/ml) and beta-caryophyllene (0.0021 g/ml)] were evaluated in the laboratory against adults of Koch. The mites were more susceptible to the oil in fumigation tests (LC50 = 0.01 mu l/l of air) than in contact test with closed Petri dish (LC50 = 7.17 mu l/ml); mortality was reduced by approximately 50 % in the latter test. The repellent action of the oil and toxicity by fumigation and contact did not differ significantly from the positive control (eugenol). The repellent activity was attributed to the components ()-nerolidol, alpha-humulene and beta-caryophyllene, whereas toxicity by fumigation and contact was attributed to beta-caryophyllene. The effect of oil and the role of its components regarding host plant preference with a two-choice leaf disk test are also discussed.