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.

Acaricidal activity against Tetranychus urticae and chemical composition of peel essential oils of three Citrus species cultivated in NE Brazil.

The repellency and fumigant toxicities of the peel essential oils of Citrus sinensis var. pêra (LP), C. sinensis var. mimo (LM), and C. aurantium (LL) cultivated in northeast Brazil were evaluated against Tetranychus urticae. Analysis of the oils by GC and GC/MS led to the identification of twenty-eight components, which represented 99.9%, 99.7% and 99.3% of the total constituents of the LP, LM and LL oils, respectively. Limonene was the main component found in all three oils. Other main components were alpha-pinene (1.5% in LP; 1.4% in LM), myrcene (5.7% in LP; 5.9% in LM and 5.6% in LL) and linalool (2.4% in LP; 2.3% in LM and 3.9% in LL). The best repellency action was observed for LM at 2.0%, followed by LL oil and eugenol, both of them at 2.5%. The Citrus oils were less active than eugenol (LC50 = 0.004 microL/L air) and phosphine, which revealed 100% mortality at 2 x 10(-3) g/L (66.7% of the recommended dose). However, the most potent fumigant toxicity was found with LL oil, with an LC50 value of 1.63 microL/L air, followed by the oils from LM and LP with LC50 values of 2.22 microL/L air and 4.63 microL/L air, respectively. The associated fumigant and repellent properties of these Citrus peel oils, particularly those of C. aurantium and C. senensis var. mimo, could be used to advantage for the control of T. urticae.