Fumigant activity of essential oils from Cinnamomum and Citrus spp. and pure compounds against Dermanyssus gallinae (De Geer) (Acari: Dermanyssidae) and toxicity toward the nontarget organism Beauveria bassiana (Vuill.)

Abstract

Dermanyssus gallinae(De Geer) (Acari: Dermanyssidae) is the main ectoparasite associated with laying poultry. This mite is commonly controlled by the application of synthetic chemical insecticides, wich lead to the selection of resistant populations and formation of residues in eggs. Thus, new molecules must be developed to control D. gallinae. This work evaluated the toxicity of essential oils (EOs) from Cinnamomum cassia, Cinnamomum camphora, Cinnamomum camphora var. linalooliferum, Citrus aurantium, Citrus aurantium var. bergamia, Citrus aurantifolia and Citrus reticulata var. tangerine against D. gallinae. Additionally, the chemical profiles of the most bioactive EOs were analyzed by gas chromatography coupled with mass spectrometry (GC-MS) and the major compounds were subjected to new tests using D. gallinae. The most toxic EOs against D. gallinae were evaluated for the nontarget entomopathogenic fungus Beauveria bassiana (Unioeste 88). The EOs from C. cassia (LC₅₀ = 25.43 ± 1.0423 μg/cm³) and C. camphora var. linalooliferum (LC₅₀ = 39.84 ± 1.9635 μg/cm³) were the most active in the fumigant bioassay and caused mortality rates of 96 and 61%, respectively. The GC-MS analysis revealed that the major constituents of EOs from C. cassia and C. camphora var. linalooliferum were trans-cinnamaldehyde and linalool, respectively. The pure compounds, trans-cinnamaldehyde (LC₅₀ = 68.89 ± 3.1391 μg/cm³) and linalool (LC₅₀ = 51.45 ± 1.1967 μg/cm³), were tested on D. gallinae and showed lower toxicity than the EOs. Thus, the compounds were not the only active substances produced by C. cassia and C. camphora var. linalooliferum; moreover synergism may have occurred between the substances. The EOs from C. cassia and C. camphora var. linalooliferum were also toxic to B. bassiana (Unioeste 88). Thus, EOs from C. cassia and C. camphora var. linalooliferum are promising candidates for use in D. gallinae control, but cannot be used in conjunction with the fungus B. bassiana.

Keywords: Botanical acaricide; Cinnamomum spp.; Citrus spp.; Entomopathogenic fungus; Integrated pest management.