Effects of pyrethroid and organophosphate insecticides on reared black soldier fly larvae (Hermetia illucens)

Abstract

Black soldier fly larvae (Hermetia illucens) receive growing interest as a potential alternative animal feed source. These insects may be exposed to insecticide residues in the rearing substrate. This study aimed to investigate the effects of six different pyrethroid and organophosphate insecticides on this insect species’ performance. The toxicity of two “model” substances for each of these classes (cypermethrin; pirimiphos‐methyl) was quantified, with and without the synergist piperonyl butoxide (PBO). Critical effect doses corresponding to 10% yield (CED10) for cypermethrin (0.4 mg/kg) and pirimiphos‐methyl (4.8 mg/kg) were determined. The addition of PBO to cypermethrin enhanced its relative potency with a factor 2.6. These data were compared against the relative toxicity of two analogue substances in each class (permethrin, deltamethrin; chlorpyrifos‐methyl, malathion). Results suggest that exposure to concentrations complying with legal limits can cause significant reductions in yield. Exposure to multiple substances at lower concentrations resulted in negative additive and synergistic effects. Of the tested substances, deltamethrin was most toxic, causing 94% yield at 0.5 mg/kg. Analytical results suggested that transfer of tested substances to the larval biomass was substance‐ and concentration‐specific, but appeared to be correlated to reduced yields and the presence of PBO. Transfer of organophosphates was overall low (<2%), but ranged from 8% to 75% for pyrethroids. Due to very low limits in insect biomass (∼0.01 mg/kg), high transfer may result in noncompliance. It is recommended that rearing companies implement lower contractual thresholds, and that policymakers consider adjusting legally allowed maximum residue levels in insect feed.

Toxicity, transfer and metabolization of the pyrethroid insecticides cypermethrin and deltamethrin by reared black soldier fly larvae

“…Furthermore, elevated transfer from substrate to larvae was observed for cypermethrin (30.8%), deltamethrin (26.3%), and permethrin (26.4%) when a cocktail of these substances was used in conjunction with PBO than without it (12.8, 10.4, 8.3%, respectively). This suggested that elevated mortality and reduced yield were correlated with higher transfer of pesticides to the larval biomass, and that this was mediated by the presence of PBO (Meijer et al, 2023). The latter would be in line with the intended effect of PBO to block the detoxifying capacity of cytochrome P450 enzymes (Snoeck et al, 2017).…”

“…A concentration/response curve was calculated for deltamethrin. Data for cypermethrin was compared to the curve calculated in Meijer et al (2023). The substrate (pre-trial) and selected larvae and frass samples (post-trial) were analysed using liquid chromatography tandem mass spectrometry (LC-MS/MS) to determine concentrations of the primary compounds.…”

“…Further, we hypothesised that metabolic breakdown products of cypermethrin and deltamethrin, with or without PBO, could provide an indication of the relevant resistance mechanisms involved. This study partly expands on the prior work in Meijer et al (2023) but focuses more on the individual toxicity of deltamethrin and its potential metabolites.…”

“…These two pyrethroid insecticides are used on a large variety of (stored) crops, including grains, legumes such as soy, potatoes, and fruits and vegetables; and residues are stable for at least one year in storage of plant-based commodities (EFSA, 2015b(EFSA, , 2023. Meijer et al (2023) showed highly significant adverse effects of dietary exposure of the insecticides cypermethrin and deltamethrin on reared black soldier fly larvae (BSFL, Hermetia illucens, L. 1758; Diptera: Stratiomyidae), manifesting in significant reductions in yield, at concentrations at or below the applicable maximum residue limit (MRL). Calculations to determine a concentration/response curve for cypermethrin showed a critical effect dose (CED) of 10% less yield to be 0.40 mg/kg.…”

Mitigation Strategies against Food Safety Contaminant Transmission from Black Soldier Fly Larva Bioconversion

“…Another found that λ-cyhalothrin negatively affected BSFL development but was nonetheless degraded in the substrate and not bioaccumulated [ 66 ]. Others found that while spinosad, deltamethrin, and cypermethrin present in a substrate at the EU’s maximum residue level negatively affected BSFL growth, imidacloprid stimulated growth while chlorpyrifos, propoxur, and tebufenozide had no effect even at ten times the maximum residue level [ 64 , 67 ]. Toxicity increased if multiple compounds were in the substrate at the same time, or if synergists like piperonyl butoxide were added.…”