Relative performance of fungicides and crude leaf extract of Azadirachta indica against leaf blight of onion

摘要

Leaf blight caused by Stemphylium vesicarium is a major production constraint in seed production of onion. The disease adversely affects the quantity and quality of seed. Stringent laws favoring eco-friendly alternatives to agrochemicals and the ban of many fungicides advocate the necessity of safer alternatives to combat this fungal menace. The present study highlights the performance of crude leaf extracts of Azadirachta indicia against leaf blight of onion to provide insight into the safe and effective nature of this botanical in curtailing the pathogenic losses to the crop. Six commercial fungicides having different mode of action viz. Zineb75WP (2.5), Mancozeb75WP (2.5), Iprobenfos 48 EC (0.1), Tebuconazole 25 EC (0.1), Difenconazole 25 EC (0.1) and Azoxystrobin 25 SC (0.1) were used to compare their efficacy relative to crude leaf extract of A. indica . The crude leaf extract of A. indica exhibited better reduction in disease incidence (61.82, 57.70) and severity (64.52 and 61.50) than organophosphate and strobilurin fungicides under field conditions during crop season 2018–19 and 2019–2020 respectively . Seeds obtained from A. indica crude leaf extract sprayed plots exhibited 83.05, 80.33 seed germination during the two consecutive years, 2018–19 and 2019–20 which was comparable with the dithiocarbamate and triazole (85.05 from Mancozeb 75 WP and 85.11 from Tebuconazole 25 EC) fungicides sprayed plots. Three sprays of crude extracts of A. indica leaves were as effective as chemical fungicidal applications for the management of this devastating disease in seed production of onion.