Bio-activities of Clerodendrum inerme extracts, essential oil, main terpenes and Ag nanoparticles against the stable fly, Stomoxys calcitrans (Diptera: Muscidae) and their non-target effects against its parasitoid, Spalangia cameroni (Hymenoptera: Pteromalidae) and earthworms.

The stable fly, Stomoxys calcitrans, is a cosmopolitan noxious dipteran hematophagous insect of veterinary and medical importance. There is a renewed interest to develop eco-friendly green pesticides to control stable flies while avoiding the health and environmental hazards of synthetic pesticides. In that framework, Clerodendrum inerme essential oil (EO) was produced by hydrodistillation, and analysed by using (GC-FID) and GC-MS). Isoeugenol (33.1 %) and dibutyl phthalate (29.3 %) were identified as the main components. Silver nanoparticles (Ci-based AgNPs were produced using the methanol (MeOH) extract and characterized using microscopic and spectroscopic instruments. The phytochemicals exhibited considerable insecticidal bioactivity towards S. calcitrans. Using topical application, Ci-based AgNPs displayed the strongest bioactivity, followed by EO, dibutyl phthalate, isoeugenol, MeOH, and aqueous extracts. At a test concentration of 160 µg/fly, Ci-based AgNPs and EO killed all insects after 24 h. The LC50 values ranged between 41.1 and 124.6 µg/fly. Using fumigation, the EO was the strongest fumigant, followed by isoeugenol, Ci-based AgNPs, and dibutyl phthalate, where the 24 h fumigation LC50's ranged between 20.8 and 73.7 µL/L air. Botanicals substantially inhibited insects' acetylcholinesterase (AChE) bioactivity. Non-target effects revealed that the phytochemicals showed an acceptable safety margins towards the parasitoid, Spalangia cameroni with LC50 values ranged between 988.18 and ˃ 2000 µL/mL. They were considered as safe for earthworms, Eisenia fetida, at concentration up to 200 mg/kg soil. The results confirm the potential of using C. inerme extracts, EO and nanoparticles as eco-friendly green insecticides against S. calcitrans.