Studies on the chemical control of Phytophthora palmivora (Butl.) Butl. on Theobroma cacao L. in Nigeria

Abstract

A pneumatic knapsack sprayer, a motorized shoulder-mounted mist-blower and an automatic tractor-mounted mist-blower have been compared for efficacy in controlling black-pod disease of cocoa and for cost of operation. Preliminary evaluation of these machines was carried out using fungicideldye mixtures applied to artificial paper-covered pods. Fungicide deposits for different methods of spraying were determined from the simple colorimetric estimation of the dye. On the basis of these tests three blocks of Amazon cocoa were sprayed with cuprous oxide during the black-pod season of 1962. Both knapsack machines gave good control of the disease but the cost of spraying with the mist-blower was three times that for the more simple machine. The tractor-mounted machine was expensive to use and gave poor disease control. It is suggested that the use of mist-blowers might be economic only in areas where labour is expensive or scarce, and where yields and black-pod losses are high. I N T R O D U C T I O NAt the end of 1962 the total number of farmers who had received training in blackpod disease control measures in Western Nigeria was 184,065. Most of these farmers have only small areas of cocoa and the vast majority rely on simple pneumatic knapsack machines which can be used equally effectively for black-pod disease or capsid pest control.With the advent of the farm settlement programme in Western Nigeria (Aribisala, 1961) it was suggested that some other quicker method of spraying trees might be necessary, as each farmer might have to deal with 10 or more acres of cocoa. Besides these farm settlements, a number of large cocoa plantations have been started in Nigeria, and it was thought that these might require mechanized spraying. It was therefore decided to compare three spraying machines which in theory should be suitable for use on small, medium and large cocoa farms. The machines selected were a simple pressurized knapsack sprayer, a small shoulder-mounted motorized mistblower and an automatic tractor-mounted mist-blower. The object of the present study was to compare the machines for effectiveness in disease control and for cost of operation.