RIND STIPPLING ON VALENCIA ORANGES BY COPPER FUNGICIDES USED FOR CONTROL OF CITRUS BLACK SPOT IN SOUTH-AFRICA

Four copper sprays and copper mixtures with dithiocarbamates aggravate d stippling of the fruit rind of Valencia oranges if sprayed in succes sion at registered rates during the recommended protection period from October to January for control of citrus black spot in South Africa. Copper stippling was more severe on treatments in which copper oxychlo ride was sprayed in succession, individually, or in combination with m ancozeb or maneb/ZnO. On the other hand, less copper stippling was obs erved on treatments in which three mancozeb applications were altered with a single copper oxychloride as tank mixtures with or without manc ozeb, which was sprayed during midsummer (December and January). Cupri c hydroxide resulted in more general copper stippling lesions than any other copper oxychloride spray program. Four successive applications of the wettable powder copper oxychloride formulation resulted in more copper stippling when compared with the suspension concentrate formul ation. Stippling was calculated to be more severe with late applicatio ns of copper fungicides during December and January. In another experi ment, all contact fungicides tested were effective in controlling citr us black spot.