Evaluation of Biofertilizer and Pesticide Performance of Black Soldier Fly Larvae <i>(Hermetia illucens) </i>Frass on Farming of Kales <i>(Brassica oleracea</i>)

Farming of edible insects is on the increase globally because it can promote circular economy. However, the resultant frass is a potential environmental pollutant, despite its high content of valuable nutrients and bioactive compounds. This research investigated application of black soldier fly frass as both biofertilizer and biocontrol agent on kales (<i>Brassica oleracea</i>). The study specifically investigated effect of black soldier fly frass on growth performance, assessed its pesticide activity; and determined effect of fermentation on frass efficiency as a pesticide. The study used a randomized complete block design to arrange the experimental plots. Three frass types were applied on kales a rate of 50 grams per plant in potted pots in a field and performance assessed by counting number of leaves in a plant and measuring leaf surface area. Frass mixed with water at a ratio of 1:1 was filtered to make frass tea and applied on kales at a weekly rate of 100 ml per plant for 4 weeks. Performance was evaluated by counting the number of pest spot attacks on the vegetables and counting number of insect larvae collected per plant. Lastly, frass from the most potent substrate was selected, and fermented for 2 and 4 days respectively to produce “frass tea” and used as above. The results were analyzed in SPSS using ANOVA and presented in graphs and tables. Results showed that kales grown on frass from chicken+fruit+brewery waste treatment had superior growth with mean value of 1.01±0.8 for number of leaves and 2.15±0.02 for leaf surface area respectively, compared to 0.47±0.1 and 1.16±0.10 respectively for the control. Secondly, frass tea from chicken+brewery waste was more effective as it recorded mean values 0.16±0.10 and 0.06±0.06 respectively for pest bites and number of larvae collected respectively, compared to 0.87±0.09 and 0.42±0.17 respectively for the control. Thirdly, fermentation had no effect on frass performance as a biopesticide as results from 2- and 4-day fermentations showed no significant differences. In conclusion, frass can be used as both an effective biofertilizer and biocontrol agent to replace conventional chemicals.