Seaweed tannins are phenolic compounds that possess strong bioactivity and may offer eco-friendly alternatives to synthetic pesticides in cotton pest management. Their formulation as emulsifiable concentrates (ECs) can enhance stability and field applicability for sustainable crop protection. Tannins extracted from the red algae Gracilaria corticata and Gracilaria fergusonii, and the green algae Chaetomorpha media and Ulva lactuca were formulated into ECs and characterized by GC–MS and 1 H and 13 C NMR spectroscopy. Emulsion stability, optical density, and pH were evaluated. Phytotoxicity tests were conducted on tomato, cotton, cucumber, and radish, while field evaluations were performed under screen house, irrigated, and rain-fed cotton conditions to assess plant growth, pest incidence, and economic benefits. GC–MS identified 1,2,3-benzenetriol (pyrogallol, 35.15%) as the major bioactive compound, confirmed by NMR peaks of aromatic hydroxyl carbons (158–162 ppm) and protons (6.5–7.5 ppm). ECs remained stable without phase separation for 210 days. Phytotoxicity tests showed 100% germination and enhanced seedling growth. Field applications with the EC at 0.03% concentration improved cotton growth by 17.30%, 11.27%, and 19.22% under screen house, irrigated, and rain-fed conditions, respectively, and reduced Xanthomonas malvacearum infection by 80%. Populations of Helicoverpa armigera, Bemisia tabaci and Polydrusas sericeus declined by 100%, 80.1% and 87.4%, respectively, with no adverse effects on beneficial insects or pollinators. Economic analysis revealed cost–benefit ratios of 1:2.60, 1:2.29, and 1:2.17, surpassing vijayneem (1:2.16) and monocrotophos (1:2.01). Seaweed tannin-based ECs are stable, non-phytotoxic, and eco-safe biopesticides that effectively suppress cotton pests and enhance yield, demonstrating strong potential for sustainable pest management.
Madasamy et al. (Mon,) studied this question.