Nursery Application of Raw and Thermally Treated Hermetia illucens Frass Shows Dose-Dependent Effects Against Fusarium oxysporum f. sp. lycopersici on Tomato Under Greenhouse Conditions

Interest in the rearing of Hermetia illucens L. by-products has increased in recent years. This study evaluated the effects of H. illucens frass, obtained from larvae reared on a Gainesville diet, for the control of Fusarium oxysporum f. sp. lycopersici (Sacc.) W.C. Snyder & H.N. Hansen (FOL). Greenhouse trials were conducted comparing thermally treated (70 °C for 60 min) and untreated frass applied at different concentrations (1–20% v/v). Disease severity, disease incidence, area under the disease progress curve (AUDPC), and plant fresh weight were assessed. Frass application significantly reduced disease severity and incidence, compared with the inoculated untreated control, with the greatest reductions observed in the 20% thermally untreated treatment and in the 5% and 10% thermally treated treatments under the greenhouse conditions of this study. The area under the disease progress curve (AUDPC) analysis suggested a reduction in disease progression over time. No significant differences were observed between thermally treated and untreated frass. Fresh weight was mainly influenced by frass dose, and the highest values were obtained with treatments at 10% and 20%. H. illucens frass showed preliminary potential as a sustainable starter for the suppression of Fusarium wilt of tomato under greenhouse conditions.