Acaricidal activity against Tetranychus urticae and essential oil composition of four Croton species from Caatinga biome in northeastern Brazil.

Volatile components of essential oils from the leaves and stems of Croton jacobinensis, C. rhamnifolius, C. muscicapa and C. micans, which are medicinal plants found in the Caatinga biome of northeastern Brazil, were analyzed using GC and GC/MS. The acaricidal activity of these oils against Tetranychus urticae was evaluated using the fumigation method. Oil yields from the Croton species ranged from 1.1 +/- 0.0 to 0.6 +/- 0.0%, w/w, for leaves and 0.7 +/- 0.0 to 0.1 +/- 0.0% for stems. Sesquiterpenoids were dominant in all oils, except the stem oil from C. rhamnifolius, which exhibited a high monoterpene content, and the leaf and stem oils from C. muscicapa, which were rich in phenylpropanoids. The major volatile components of the leaf and stem oils from C. jacobinensis were (Z)-alpha-atlantone (24.3 +/- 0.4%) and trans-isolongifolanone (22.8 +/- 0.5%), respectively. The most abundant constituents detected in C. rhamnifolius were alpha-cedrene epoxide (23.3 +/- 0.1%) and caryophyllene oxide (21.9 +/- 0.0%) in the leaf oil, and camphor (16.6 +/- 0.5%) and tricyclene (12.8 +/- 0.1%) in the stem oil. Foenicolin was the main compound identified in the leaf (50.6 +/- 0.2%) and stem (72.7 +/- 0.6%) oils of C. muscicapa, while alpha-bulnesene (32.9 +/- 0.2%) and guaiol (17.9 +/- 0.7%) were the principal components of C. micans oils. These oils exhibited a high degree of toxicity in the fumigation assay. The stem oils from C. jacobinensis and C. rhamnifolius exhibited high lethality rates, with LC50 values of 0.3 and 0.2 microL/L of air after 24 h, respectively. The results suggest the potential use of stem essential oil, especially from C. rhamnifolius and C. jacobinensis, for the integrated control of Tetranychus urticae.