Insecticidal properties of Pimpinella anisum essential oils against the Culex quinquefasciatus and the non-target organism Daphnia magna

The efficacy of an essential oil obtained from Pimpinella anisum fruits and its major compound, trans-Anethole, was tested on the eggs, larvae and adults of Culex quinquefasciatus. While causing no significant mortality on eggs, other tested stages were very sensitive to the essential oil and trans-Anethole. LC50 for the 2nd to 4th instar larvae was estimated as 26-27 mu L center dot L-1 and 15-19 mu L center dot L-1 for the essential oil and trans-Anethole, respectively. As for the essential oil applied on adults, LC(LD)(50) was estimated as 9.3 mu L mL(-1) (spray test), 1.9 mu L L-1 (fumigation test) and 0.6 mu g cm(-2) (tarsal test), and for trans-Anethole as 8.1 mu L mL(-1) (spray test), 2.1 mu L L-1 (fumigation test) and 0.4 mu g cm(-2) (tarsal test). The time needed to achieve 50% mortality after application of LC(LD)99 of the essential oil was significantly different; for example, in larvicidal assays it ranged from 15 to 235 mffi depending on the larval instar, and from 9 to 180 mffi when applied to adults, depending on the mode of application. It was also found that temperature had an important effect on the larvicidal efficacy of the essential oil, and oviposition deterrent activity was studied. The essential oil and trans-Anethole were toxic for Daphnia magna (62-92% mortality) and significantly reduced its fertility at high concentrations (35-50 mu L mL(-1)) and long exposure (48 h). However, no negative effect on Daphnia mortality or fertility was found at shorter exposure times (6 h) and/or lower concentrations (20 mu L mL(-1)). Based on the results of this study, we can recommend the essential oil from P. anisum as a suitable active substance for potential botanical insecticides. (C) 2014 Korean Society of Applied Entomology, Taiwan Entomological Society and Malaysian Plant Protection Society. Published by Elsevier B.V. All rights reserved.