Enhanced Toxicity of Binary Mixtures ofBacillus thuringiensissubsp.israelensisand Three Essential Oil Major Constituents to WildAnopheles sinensis(Diptera: Culicidae) andAedes albopictus(Diptera: Culicidae)

Abstract

An assessment was made of the toxicity of 12 insecticides and three essential oils as well as Bacillus thuringiensis subsp. israelensis (Bti) alone or in combination with the oil major constituents (E)-anethole (AN), (E) -cinnamaldehyde (CA), and eugenol (EU; 1:1 ratio) to third instars of bamboo forest-collected Aedes albopictus (Skuse) and rice paddy field-collected Anopheles sinensis Wiedemann. An. sinensis larvae were resistant to various groups of the tested insecticides. Based on 24-h LC50 values, binary mixtures of Bti and CA, AN, or EU were significantly more toxic against Ae. albopictus larvae (0.0084, 0.0134, and 0.0237 mg/liter) and An. sinensis larvae (0.0159, 0.0388, and 0.0541 mg/liter) than either Bti (1.7884 and 2.1681 mg/liter) or CA (11.46 and 18.56 mg/liter), AN (16.66 and 25.11 mg/liter), or EU (24.60 and 31.09 mg/liter) alone. As judged by cotoxicity coefficient (CC) and synergistic factor (SF), the three binary mixtures operated in a synergy pattern (CC, 140.7-368.3 and SF, 0.0007-0.0010 for Ae. albopictus; CC, 75.1-245.3 and SF, 0.0008-0.0017 for An. sinensis). Global efforts to reduce the level of highly toxic synthetic insecticides in the aquatic environment justify further studies on the binary mixtures of Bti and essential oil constituents described, in particular CA, as potential larvicides for the control of malaria vector mosquito populations.

Enhanced cuticular penetration as the mechanism for synergy of insecticidal constituents of rosemary essential oil in Trichoplusia ni

“…Similar reports of partial and incomplete activity of individual major constituents of essential oils on microorganisms and insects suggest synergy with minor constituents of essential oils 8 9 10 11 12 . Synergy can be also found between essential oils 13 or terpene compounds 14 15 , even in their interactions with synthetic antimicrobials 16 , insecticides 5 , or other natural organic and inorganic materials such as amphotericin B 17 , Bacillus thuringiensis 18 , diatomaceous earth 19 and vanillin 20 21 .…”

Control methods against invasive Aedes mosquitoes in Europe: a review

“…Moreover, binary mixtures of some EO constituents with Bti were observed to be more active against Ae. albopictus larvae than Bti alone …”

“…albopictus larvae than Bti alone. 98 The production of EOs is generally cheaper than that of individual compounds that must be isolated or synthesised. Apart from being economically viable, plant-based larvicides are obtained from a renewable resource and are widely accepted by the population.…”

Amylose Inclusion Complexes as Emulsifiers for Garlic and Asafoetida Essential Oils for Mosquito Control

“…However, evolution of Bti resistance remains a serious concern highlighting the need for the discovery and development of new biopesticides for application in integrated vector management [65,66,67]. Additionally, some essential oils have been shown to work in synergy with Bti [68]; thus, a combination of Bti and essential oil emulsions may be a novel strategy for managing insecticide resistance. Further studies are needed to determine how garlic and asafoetida essential oil emulsions interact with Bti and other commercially available biopesticides.…”