Algal bioactive compounds for next-generation biopesticides: a multi-target resource for sustainable pest management

The rapid growth in global population and the incessant demand for food warrant greater attention to sustainable agricultural practices. To ensure adequate food security, protection of crops from exposure to biotic agents (e.g., pathogens and insects) is imperative. Over the decades, synthetic pesticides have been used to control pests in agriculture. However, excessive and uncontrolled use of these chemical compounds causes serious environmental and health hazards. Therefore, algal biopesticides are used as biological agents to control soil-borne diseases and plant pests. The algae secrete a broad spectrum of metabolites, including phenolic compounds, terpenoids, alkaloids, peptides, and others. These bioactive compounds exhibit insecticidal, nematocidal, herbicidal, antibacterial, antifungal, and antiviral activities, thereby enhancing crop protection and productivity. Algal biopesticides are effective, eco-friendly, biocompatible, sustainable, and biodegradable, with low or no toxicity to the environment and beneficial off-target organisms. Thus, the present review focuses on the mechanisms of action and biological activities of various bioactive compounds produced from macroalgae and microalgae for exploitation as biopesticides. In addition, it presents the much-needed techno-economic analysis (TEA) and conceptual scenarios for cost-effective algal biopesticide production by integrating wastewater-based cultivation systems and designing multiple biorefinery approaches. The regulatory pathways for algal biopesticides, as well as some limitations hindering their commercial production, are also discussed.