S U M M A R YI n laboratory trials, phenyl mercury nitrate at 0-02 p.p.m. and fentin acetate at 0.2 p.p.m. severely retarded growth of four isolates of Phytophthorapalmivora on cassava agar. These two chemicals, with captan, maneb and a dithiocarbamate-copper chelate, were also highly toxic to encysted zoospores of a 'rubber' group isolate of P. palmivora.Deposits of captan on pods were readily removed by artificial rain, but some improvement in tenacity was obtained by the addition of a sticker. I n other laboratory trials, the deposit from low-volume sprays of cuprous oxide dried more quickly on pods than that from high-volume sprays but showed no advantage in subsequent resistance to weathering.I n a field trial in 1961, seven fungicide treatments were applied three-weekly and compared with an unsprayed control. T h e lowest percentage black-pod infection followed treatment with fentin acetate : Bordeaux mixture and carbide Bordeaux both gave good control. The captan treatments were completely ineffective. More black pods were harvested from close-spaced trees than from those wide-spaced.Weekly applications of 0-15 yo fentin acetate to seedlings induced no significant damage. I n a field trial made in 1962 very heavy rainfall provided a severe test of the fungicides, the most effective being Bordeaux mixture and carbide Bordeaux mixture applied three-weekly, carbide Bordeaux mixture applied four-weekly and fentin acetate applied two-weekly. Captan with added sticker was again no better than the control. There was no marked effect of spacing.Comparisons of Bordeaux and carbide Bordeaux mixtures made at two other sites in 1962 showed no difference in disease control. It is suggested that carbide Bordeaux mixture could be replaced by the cheaper preparation made with lime.

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.