Insecticidal, biochemical and histological effects of monoterpenes against Musca domestica (Diptera: Muscidae)

The insecticidal activity of ten monoterpenes against larvae of Musca domestica (Diptera: Muscidae) was evaluated. Monoterpenes were mixed with food-media at concentrations of 2.5, 5.0, 10.0, 25.0, 50.0, 75.0 and 100.0 mg/kg. Three monoterpenes, p-cymene, 1,8-cineole and cuminaldehyde displayed a durable larvicidal activity with LC₅₀ values of 0.14, 1.59 and 1.90 mg/kg 3 days post treatment. The three monoterpenes were more toxic than deltamethrin (LC₅₀ = 3.36 mg/kg). Likewise, monoterpenes induced a significant reduction in pupation and adult emergence. Cuminaldehyde at 25.0 mg/kg, and p-cymene, 1,8-cineole and citronellal at 50.0 mg/kg caused a complete inhibition of pupation and adult emergence. Also, p-cymene at 25.0 mg/kg reduced the activity of larval amylase and lipase, while 1,8-cineole and cuminaldehyde increased their activity. Cuminaldehyde and α-terpinene inhibited the activity of proteases whereas p-cymene enhanced their activity. In the case of acetylcholinesterase, general-esterase and adenosinetriphosphatase, p-cymene and 1,8-cineole induced enzyme inhibition and citronellal increased enzyme activities. Finally, the tested monoterpenes caused histological changes on treated larvae, such as the basement membrane appeared and the epithelium cells deformed in some points and seen filled with scattered vacuoles. These findings indicate that the tested monoterpenes have a potential to be applied in IPM programs of M. domestica.