Cocoa Research Institute of Nigeria, Nigeria
Title: Toxicity estimation of copper–based fungicides on Phytophthora megakarya causing black pod of cacao
Biography: Dele Adeniyi
Aim: The study determines the estimated toxicity and efficacy of copper-based fungicides use to control Phytophthora megakarya
Study Design: Toxicity of fungicides against Phytophthora megakarya was determined in-vitro using mycelial growth inhibition.
Methodology: Isolates of Phytophthora megakarya were collected from cacao plantation in the demonstration/experimental plots of Cocoa Research Institute of Nigeria, Ibadan, South Western Nigeria. Three active ingredients: Cuprous oxide, Copper hydroxide and Copper hydroxide + metalaxyl in fungicides retailed in open market in Ibadan were assayed in-vitro at 0.5 µg/ml, 1.0 µg/ml, 1.5 µg/ml, 2.0 µg/ml and 2.5 µg/ml of active ingredient against mycelial growth of Phytophthora megakarya; pathogen of black pod disease. The antifungal index and effective concentration at which mycelial growth was inhibited by 50% (EC50 value) was calculated for pathogen/fungicide combination and probit analysis.
Results: Toxicity of fungicides against Phytophthora megakarya using the EC50 showed significant variation as estimated from the mycelial growth inhibition. Highest mycelial inhibition (85.25%) of Phytophthora megakarya was recorded at 2.5 µg/ml of Copper hydroxide + metalaxyl with estimated EC50 value of 0.18 µg/ml and highest toxicity was recorded in Copper hydroxide + metalaxyl while Cuprous oxide was least toxic against Phytopthora megakarya. The toxicity responses of these Copper-based fungicides against Phytophthora megakarya vary with active ingredients and Copper hydroxide + metalaxyl gave the highest fungitoxic effect.