Acute Toxicity of Hermetia illucens, Zophobas morio, Alphitobius diaperinus, and Tenebrio molitor Frass Water Extracts on Meloidogyne incognita and Chemical Composition Analysis

Global plant production systems face increasing pressure from growing food demand, climate change, and biodiversity loss, driving the search for sustainable plant protection products (PPPs). Meloidogyne incognita, a destructive plant parasitic nematode, has traditionally been controlled with synthetic pesticides, but natural nematicides are gaining attention. Frass, the organic waste produced by insects, contains excreta, undigested material, and shed exoskeletons. In the European Union, insect-derived products for food/feed purposes are approved as an organic fertilizer after heat treatment at 70 °C for one hour, and frass from Hermetia illucens, Zophobas morio, Alphitobius diaperinus, and Tenebrio molitor is authorized as a food ingredient. This study evaluated frass from these four species, before and after heat treatment, for nematicidal activity against M. incognita. Paralysis of second-stage juveniles was measured and linked to chemical composition before and after heat treatment. All treatments showed dose–response effects, with irreversible paralysis after 72 h with the exception of H. illucens not reaching EC50 values at the highest test concentration. Prior to heat treatment, the highest potency at 24 h was observed for Z. morio extracts with an EC50 of 6.6% v/v. Among the species tested, T. molitor and A. diaperinus frass maintained the highest nematicidal activity following the heat-treated frass.