Effect of the Rearing Substrate Contamination with λ-Cyhalothrin Pesticide on the Growth Performance and Survival of Black Soldier Fly (Hermetia illucens) Larvae: A Study of Biodegradation Kinetics

Pesticide residues may be present in fruits and other organic wastes used as rearing substrates for black soldier fly larvae (BSFL, Hermetia illucens). These contaminants are toxic, and their presence in rearing substrates might affect the growth and survival of BSFL as well as the safety of larvae. The present study assesses the effect of λ-cyhalothrin pesticide present in rearing substrates (mixture of oranges and pineapples) on the growth performance and survival of BSFL. Moreover, the biodegradation kinetics of λ-cyhalothrin by BSFL and kinetic parameters were determined. Six-day old larvae were reared on the fruit wastes, spiked with known concentrations of λ-cyhalothrin. The High-Performance Liquid Chromatography (HPLC) technique was used in the determination of residual concentrations of λ-cyhalothrin in both larvae and substrates. By application of the HPLC method, a linear dynamic range of λ-cyhalothrin was found within the concentration range of 0.625—20 mgL−1, with a limit of detection and limit of quantification of 0.124 mgL−1 and 0.820 mgL−1, respectively. Overall, the presence of λ-cyhalothrin (concentration ≥ 30 × Maximum Residual Limit) in the spiked substrate was observed to slow down the development of larvae, but no bioaccumulation of λ-cyhalothrin was detected in the survived larvae at all developmental stages. No larvae survived on the substrates with λ-cyhalothrin concentrations of 5 mgL−1 (A total mortality was observed 48 h after incubation). The development of BSFLs on substrates containing 3 mgL−1 of λ-cyhalothrin was weak, but larvae showed an ability to degrade λ-cyhalothrin and no by-products were identified. The obtained degradation kinetics were found to be of second order, with half lives of 2.00, 8.85 and 9.52 days for λ-cyhalothrin at 0.5, 1, and 3 mgL−1, respectively. The present approach showed no contamination risk of BSFLs by pesticide residues present in rearing substrates. However, the presence of pesticide residues affects the development of larvae at certain concentrations and therefore could reduce the production. The proposed approach could be an efficient alternative for a quality control analysis of BSFL produced in West Africa.