The effectiveness of black soldier fly (Hermetia illucens L) frass as a biopesticide of green peach aphid (Myzus persicae)

Biopesticides are non-toxic and biodegradable, less likely to develop resistance to pests and break down more quickly than synthetic pesticides. Black soldier fly (Hermetia illucens L) frass, the solid waste of black soldier fly larvae, can be used as a potential biopesticide due to its high chitin content, which has insecticidal properties and stimulates plant defences. However, research is needed to understand its effectiveness. This study evaluated the efficacy of black soldier fly frass tea (BSFFT) and residues incorporated into the soil as a potential biopesticide of the green peach aphid established on Brassica oleracea capitata L seedlings. The BSFFT at different concentrations (15, 30 and 60 g l−1) and a frass soil amendment (50 g) were compared with that of diluted dishwashing liquid (15 g l−1) (positive control) and distilled water (negative control). Behaviour and mortality were observed over 48 hours. Responses were analysed using beta regression, revealing that Myzus persicae Sulzer behaviour and mortality varied significantly between treatments. Adult aphid mortality was significantly higher for diluted dishwashing liquid (83%), the 50g soil amendment (21%), 15 and 60 g l−1 (both 18%) BSFFT than that of distilled water and 30 g l−1 frass tea. In contrast, the 30 g l−1 BSFFT and 60 g l−1 (16%) frass tea foliar applications also functioned as a bio-repellent, with 16–17% of adult nymphs moving off treated plants. The additive effect of mortality and repellence reduced aphid numbers by up to 34%. Overall, BSF frass exhibits some pest control activity and, as an organic and sustainable input, may contribute to plant health in addition to reducing pest pressure.