Acaricidal properties of hemp (Cannabis sativa L.) essential oil against Dermanyssus gallinae and Hyalomma dromedarii

The use of conventional pesticides in pest management is facing issues such as developing resistance in pests, environmental pollution and impact on human health, together with regulatory hurdles for approval and marketing of new eco-friendly pesticides to comply with the global trend for residue-free foodstuff. In this framework, botanical pesticides represent valuable alternative products to be exploited. Hemp (Cannabis sativa L.) is an eco-friendly, multipurpose crop that is known for its resistance against insects and parasites. This property is assured by the production of bioactive secondary metabolites such as terpenes and cannabinoids. Notably, the hemp essential oil (EO) contains several terpenoid compounds endowed with pesticide properties. On this basis, in the present work we assayed the toxicity of hemp EO on two ectoparasites of veterinary im- portance, i.e. Dermanyssus gallinae De Geer and Hyalomma dromedarii Koch. In order to identify the EO chemical constituents responsible for the toxicity on the two ectoparasites, the main monoterpenes and sesquiterpenes of 1. Introduction Mites and ticks, collectively placed in a taxon of arachnids known as the acari, infest man and animals causing deleterious effects on human and animal health and subsequently serious economic losses. Decades of use of synthetic pesticides such as organophosphates and organo- chlorines for controlling ticks and mites resulted in several problems including development of resistance, environmental hazards, and undesirable effects on non-target organisms, animals and human health (Benelli et al., 2016; Benelli and Pavela, 2018; Benelli et al., 2019a). Organic plant-derived compounds endowed with acaricidal properties represent alternative controlling agents (Benelli, 2015; Pavela et al., 2016; Banumathi et al., 2017). Plants can produce a broad range of secondary metabolites; among them, terpenoids are among the most successful pesticides (Pavela et al., 2019; Benelli et al., 2019b). Ter- penoids are toxic to insects and can act as antifeedant and repellent hemp EO, namely α-pinene, myrcene, (E)-caryophyllene andα-humulene were tested as well. Mite contact 3 toxicity assays were carried out at the concentrations of 5, 10, 20, 50, 100 and 200 μg/cm . Tick larvicidal and ovicidal assays were done testing 0.5, 1, 2, 5, 10, 20, and 50 μg/mL of the hemp EO and its main components. Results from mite contact toxicity showed that hemp EO was toxic to D. gallinae with LC50 values of 47.1 μg/mL. Larvicidal and ovicidal assays revealed the promising activity of the EO against tick larvae and eggs. Among all the tested compounds, (E)–caryophyllene and α-humulene were the most toxic for both ticks and mites, showing LC50 values lower than the whole EO. Myrcene was moderately toxic, with LC50 values higher than the whole EO, whereas α-pinene showed weak acaricidal activity. Taken together our results remarked the potential of hemp EO as a potential botanical acaricide in pest management programs and food production. The industrial scalability is assured by the great availability of land for the cultivation of hemp and its low cost of production