Chemical Composition and Bioactivity of Essential Oils of Croton blanchetianus Bailland and Sida cordifolia L. on Callosobruchus maculatus (Fabr., 1775)

This study aimed to evaluate the yield and chemical composition of essential oils from Croton blanchetianus and Sida cordifolia, in addition to investigating the insecticidal potential of these oils on adults of the bean weevil, Callosobruchus maculatus. To obtain the oils, the hydrodistillation method was adopted, using a Clevenger apparatus. The identification and quantification of chemical constituents was performed by means of gas chromatography coupled to mass spectrometry (GC-MS). For each oil, fumigation bioassays were performed on adults of C. Macullatus in six concentrations, 0; 0,30; 0,48; 0,60 e 0,70 (µL/750 mL) for C. Blanchetianus. As for the essential oil of S. cordifolia, the concentrations applied were 0, 3, 6, 9, 12 and 15 (µg/750 mL). The bioassays were carried out under constant conditions of temperature (25 ± 2ºC) and relative humidity (60% ± 10%). In the fumigation tests, different concentrations of the oils were applied to strips of filter paper (2x3 cm) attached to the bottom of the lid of a glass container (750mL), which contained 10 grams of cowpea and 15 unsexed adult insects. Insect mortality was evaluated 48 hours after the treatments were applied. Data were submitted to analysis of variance and regression analysis. When possible, lethal doses were calculated for 50 and 95% of the test population (LD50 and LD95). The yield of essential oil from C. blanchtianus was 0.50%, higher than that obtained for S.cordifolia, which was 0.03%. For the species C. blanchetianus, 20 components were identified, with the monoterpene eucalyptol being the major compound (32.89%). For S.cordifolia, 12 components were identified, with sesquiterpene spathulenol being the major compound (31.76%). In fumigation bioassays, considerable insecticidal activity of C. blanchetianus essential oil was observed on C. maculatus adults, with relatively low lethal doses. As for the essential oil of S.cordifolia, the doses used in the study caused a maximum of 5.3% mortality, and it was not possible to determine the LD50 and 90 for the essential oil of this species.