Management of purple blotch (Alternaria porri) in onion using indigenous plant extracts and cow urine: a sustainable alternative to synthetic fungicides
摘要
Purple blotch, caused by Alternaria porri (Ellis) Cifferi, is a widespread fungal disease that severely affects onion yield. In the present study, survey across major onion-growing regions of Himachal Pradesh, India, revealed 25.0–84.0% disease incidence and 13.3–66.7% disease index. In pursuit of sustainable and eco-friendly management strategies, aqueous and cow urine-based extracts of native plants were evaluated against purple blotch. In vitro assays exhibited significant antifungal activity with aqueous Datura stramonium extract (@ 50%) achieving 63.7% mycelial inhibition, whereas cow urine alone completely inhibited the growth of the pathogen. Furthermore, cow urine-based biopesticide formulations of Murraya koenigii and D. stramonium (@ 40%) inhibited mycelial growth by 84.5% and 68.1%, respectively. Pot experiments confirmed the efficacy of these treatments, with cow urine alone reducing disease incidence and disease index by 91.3% and 93.6%, respectively. Field trials were conducted in a randomized block design during 2018–2019 and 2019–2020 at the experimental farm of college to validated these results under natural epiphytotic conditions. Based on pooled data over two years, cow urine (@ 40%) emerged as the most effective treatment, reducing disease incidence by 82.3%, disease index by 86.0% and enhancing bulb yield to 7.0 kg/plot compared to 3.9 kg/plot in the untreated control. M. koenigii and D. stramonium biopesticide formulations demonstrated moderate efficacy, while those containing Ocimum tenuiflorum and Calotropis gigantea were comparatively less effective. The present study establishes the effectiveness of cow urine-based biopesticides for the management of purple blotch in onion. The findings underscore the potential of these biopesticides not only in suppressing disease, but also in promoting plant growth and enhancing yield. Hence, cow urine-based biopesticides represent a safe, cost-effective and environmentally sound alternative to conventional synthetic fungicides for the management of purple blotch of onion.