Biotoxicity of Melia Volkensii Fruit Pulp and Nut Extracts on Selected Beneficial Insects in Embu, Kenya

Abstract

The predominant approach in safeguarding crops against insect pests has mainly been centered on synthetic pesticides. Pesticide use has helped mitigate pest menace. However, concern about their detrimental effect on the environment and human health is rising. The adverse effects necessitated the development of eco-friendly pest management alternatives. Bioderivatives exhibit promise as biopesticides as alternatives to synthetic pesticides, but their impact on beneficial insects remains understudied. Beneficial insects play a vital role in the ecosystem; thus, protecting them from the adverse effects of pesticides is vital. This study aimed to assess the eco-friendliness of Melia volkensii fruit extracts on beneficial insects. The study exposed African honeybees (Apis mellifera), icipe braconid wasp (Cotesia icipe), and seven spotted ladybug beetles (Coccinella septempunctata) to different Melia extracts dosages, Emamectin benzoate, and Azadirachtin through ingestion and direct contact. The experiments were laid out in a completely randomized design, replicated four times, and repeated once. Observations were made 12 hours after incubation. The monitoring process persisted daily for 3 days for bees and wasps, and 20 days for the ladybug beetle. Parameters observed following exposure of the beneficial insects to the pesticides included mortality rates, paralysis incidence, and instances of no observable effect. Direct application of Melia volkensii extracts to honeybees led to significant (p<0.05) mortality of bees compared to control, especially at higher concentrations of 1% and 2%, similar to the effects of Emamectin benzoate. Lower concentrations (0.1% and 0.5%) resulted in lower mortality rates. Emamectin benzoate caused significant (p<0.05) rapid and complete mortality within 24 hours. Ingestion of Melia volkensii extracts produced variable effects. Emamectin benzoate led to 100% mortality, while Azadirachtin and the control showed minimal impacts on bees. Melia nut extract ingestion resulted in high mortality, with 0.1% allowing only 20% survival. Melia pulp extracts exhibited higher survival of bees, with concentrations of 0.1% and 0.5% showing approximately 70% survival, mirroring the neem-based treatment...