In vitro Evaluation of Fungicides and Plant Extracts to Control Purple Blotch Disease of Onion in Pakistan

Nisar Uddin, Abdul Naseer, Muhammad Shahid, Noor Muhammad and Niaz Ali

Background and Objective: Purple blotch caused by A. porri (Ellis) Cif. is a devastating disease of onion (Allium cepa L., 2n =16) throughout the world. This study compared effectiveness of the most frequently used fungicides and different plant extracts as control measures for the purple blotch disease. Materials and Methods: The fungal inhibition potential of leaf extracts was evaluated from 7 plants, indigenous to District Swat as well as the commonly available fungicides under laboratory conditions. Multivariate analysis and the ANOVA results revealed a direct relationship for the plant extracts/fungicides application and mycelial inhibition. Results: The extracts of C. sativa (1 and 2 ppm) was found the most effective and caused over 91.89 and 91.66% inhibition of mycelial growth. The order of efficacy of the 1 ppm plant extract was followed by D. mucronata (79.00%), D. viscosa (78.99%), C. procera (77%), J. adhatoda (60.65%) and A. altissima (57.98%), while in 2 ppm 83.14% was followed by 82.09, 82.02, 71.33, 55.05 and 39.32%, respectively. Among the 5 fungicides applied, DuPont^TM Curzate^® M8 in both concentrations were the most effective and caused over 89.88% inhibition. Potential synergy of the of leaf extracts of C. sativa+J. adhatoda was highly effective, resulted in 80 and 84.28% mycelial inhibition. Conclusion: The results highlight the critical role of finding the right proportion of appropriate compounds to perform as a potential pesticide. These results indicate to the importance of phyto extracts as promising alternatives to synthetic fungicides for being cost effective, eco-friendly and sustainable means of controlling the purple blotch of onion.

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