Comparative Evaluation of Fungicidal Effects of Some Botanicals and Ridomil Plus on the Management of Black Pod Disease of Cocoa (Theobroma cacao L.)

Abstract

Phytophthora, the ‘plant destroyer’, is a cosmopolitan genus of Oomycete obligate plant pathogens with about 60 described species, attacking several plants in both the temperate and the tropical regions of the world. Cocoa had been one of the major sources of income and foreign earnings to Nigerians before the crude oil discovery in commercial quantities in the 1970s. The aim of the study is to compare the evaluation of fungicidal effects of some botanicals and Ridomil plus on the management of Black Pod Disease of Cocoa (Theobroma cacaoL.). Phytophthora megakarya-infected cocoa pods were obtained from the plantation of Cocoa Research Institute of Nigeria (CRIN), Ibadan and transported in sterile polythene bags to the Plant Pathology laboratory. Leaf samples of Chromolaena odorata, Morinda lucida and Ocimum gratissimum collected from the campus of Ekiti State University, rinsed with sterile distilled water and air dried for 4 weeks. The effect of aqueous extract of Chromolaena odorata, Morinda lucida and Ocimum gratissimum on the mycelia growth of P. megakarya at 3, 5 and 7days post inoculation. The highest inhibitions of 90.53%, 91.09, and 93.13 by Chromolaena odorata against P. megakarya at 3, 5 and 7 days post inoculation at 30g 100 ml-1 were observed, but the lowest at a concentration of 10 g 100 ml-1. C. odorata exhibited higher inhibition (67.13, 71.64 and 79. 64%) than ridomil plus (62.91, 66.31 and 67.83%) at 3, 5 and 7 days after treatment. The aqueous extracts of (30%) Occimum gratissimum also showed comparable effectiveness with ridomil gold in reducing the radial growth of the pathogen. This work also gives credence to the global advocacy for organic food production for human health benefit. C. odorata is cheap and easily affordable for farmers to use in the management of the menace of Phytophthora megakarya.