Evaluation of Pelargonic Acid as a Sustainable Defoliant in Cotton (Gossypium hirsutum L.) Production

Cotton production faces sustainability challenges due to the lack of effective sustainable defoliants for mechanical harvesting, which constrains the expansion of organic cotton (currently 0.5% of global production). In this framework, this study evaluated pelargonic acid, a rapidly biodegradable compound, as a sustainable defoliant alternative, comparing it with the synthetic pyraflufen-ethyl and a water placebo. A two-year field trial (2023–2024) in Sicily, southern Italy, tested three application rates per treatment in a randomized complete block design. Parameters assessed included defoliation efficacy, root diameter, boll number per plant, average boll weight, raw yield, lint yield, and seed yield. Results indicated significant “Year × Treatment” interaction effects on all parameters. Pelargonic acid applied at 16 L ha−1 achieved the highest boll number per plant in 2024, significantly exceeding pyraflufen-ethyl at its label-recommended rate, with treatments at 12 L ha−1 also producing larger root diameters than the synthetic defoliant. Pelargonic acid at 18 L ha−1 in 2023 achieved complete defoliation, matching the efficacy of pyraflufen-ethyl, while the lowest pelargonic rate (12 L ha−1) produced >90% leaf drop across both years. These findings position pelargonic acid as a rapidly degradable alternative to synthetic defoliants, directly addressing a key bottleneck in sustainable cotton production.