Toxic effects of an essential oils mixture on Aleurodicus cocois (Hemiptera: Aleyrodidae) and Chrysoperla externa (Neuroptera: Chrysopidae)

Abstract

ABSTRACT The whitefly Aleurodicus cocois is one of the main pests of cashew, Anacardium occidentale L. in Brazil. The use of essential oils and their constituents is an alternative means of controlling pests with low risk to natural enemies. In the present study, the chemical profile and toxicity of a mixture of the essential oils of Lippia sidoides Cham. (Verbenaceae) and Cymbopogon winterianum Jowitt. (Poaceae) on the third and fourth nymphal stages of A. cocois were evaluated, as well as their toxicity to the predator Chrysoperla externa (Hagen, 1861) (Neuroptera: Chrysopidae). Thymol and ρ-cymene were the majority monoterpenes in L. sidoides oil, whereas in C. winterianus, geraniol, citronellal and citronellol oil were the main components. In the concentration-mortality bioassays, the toxicity of the mixture of the two essential oils evaluated on the third and fourth nymphal stages of A. cocois in terms of LC50 was estimated at 11.17 and 16.92 mg/mL, respectively. At all concentrations evaluated, the mixture of essential oils caused low mortality of C. externa eggs and larvae and did not alter predator development time. Additional repellency tests showed that independent of the tested concentrations and exposure times (1, 3, and 24 h), C. externa larvae were repelled by the mixture of essential oils. It is concluded that the mixture of the essential oils of L. sidoides and C. winterianum is toxic to nymphal stages of A. cocois and moderate toxicity to C. externa.