Essential oils from Dysphania ambrosioides and Tagetes minuta enhance the toxicity of a conventional insecticide against Alphitobius diaperinus

The darkling beetle Alphitobius diaperinus is one of the most common pests in poultry farms, with its occurrence causing several problems including the dispersion of pathogenic microorganisms, injuries and stress in birds, as well as structural damage to the facilities. The aim of this study was to investigate the chemical composition of essential oils (EOs) from Dysphania ambrosioides and Tagetes minuta, and to determine their contact toxicity alone and in combination with cypermethrin against adults of A. diaperinus. The main components of the EOs were ascaridole, p-cymene and carvacrol in D. ambrosioides oil, and dihydrotagetone, cis-ocimenone, trans-tagetone and trans-β-ocimene in T. minuta oil. The EOs from both plants showed a high contact activity, while cypermethrin was slightly toxic to the insect when applied alone. The toxicity of D. ambrosioides oil was six times better than that of T. minuta oil, and more than fifty times more effective than cypermethrin. When cypermethrin was applied in combination with the EOs at low concentrations, the toxicity of this insecticide increased significantly. As the EOs studied have interesting properties against A. diaperinus, their use could be considered in new strategies for pest management.