Bioactivity and Ecotoxicological Safety of Subcritical Water Extracts from Coffee Production Waste as a Multifunctional Biopesticide

Valorizing agro-industrial by-products within a circular bioeconomy provides sustainable alternatives to synthetic pesticides. This study evaluated a coffee production waste (CPW) aqueous extract, obtained via subcritical water extraction, as a multifunctional biopesticide. We assessed its chemical profile, antifungal and insecticidal efficacy, ecotoxicology, allelopathy, and biochemical phytotoxicity. HPLC-DAD-MS revealed high levels of caffeine (12.9 mg/g DM), trigonelline (10.8 mg/g DM), and chlorogenic acids (~8.5 mg/g DM). It demonstrated broad in vitro antifungal activity, inhibiting Botrytis cinerea mycelial growth (84.0%) and conidial germination (98.1%). In vivo, CPW reduced apple gray mold severity to 34.9%, though in planta protection on tomato was partial. The extract reduced Halyomorpha halys egg hatching to 33.0% and increased nymphal mortality to 49.0% via symbiotic disruption, without harming its parasitoid Trissolcus japonicus. However, high acute mortality in the pollinator Osmia bicornis highlights the need for risk mitigation. Crucially, CPW showed negligible phytotoxicity on crops but selectively reduced weed germination by up to 25%, supported biochemically by its non-inhibition of plant defense CYP74 enzymes. In conclusion, CPW extract is a promising bioactive candidate for sustainable crop protection, requiring formulation optimization to enhance field safety and performance.