Compatibility of Mancozeb 75 WP with some plant extracts in the integrated management of Cercospora leaf spot disease of okra (Abelmoschus esculentus (L.) Moench)

Abstract

The use of synthetic mancozeb fungicide has not been effective in the control of okra leaf spot (Pseudocercospora abelmoschi) disease amidst critical issues of environmental concerns. Therefore, this study evaluated the compatibility of mancozeb 75 WP with some botanicals in the integrated management of the disease. Laboratory assay was a 3×4×2 factorial laid out in a completely randomized design with three replications, while the field experiment was a randomized complete block design with 14 treatments. Four extract concentrations, 15, 30, 45 and 50% w/v and 0.5 g/l Mancozeb 75 WP were evaluated. The application of Syzygium aromaticum extract at 50% w/v concentration had the highest mycelial growth reduction of 71.89% of the pathogen. The soil textural class was sandy loam and treatments effect on okra growth indices did not differ significantly (p>0.05). The highest pod yield of 15.48 t/ha-1 was obtained in treatment inoculated with P. abelmoschi. but treated with a combination of S. aromaticum and Mancozeb. The same treatment had the lowest disease incidence of 4.01%, while combined application of C. papaya, S. aromaticum and Mancozeb recorded significantly (p<0.05) lower disease severity among inoculated plants. Therefore, this combination is recommended as foliar spray on okra in place of Mancozeb.