Gc. Schutte et al., RIND STIPPLING ON VALENCIA ORANGES BY COPPER FUNGICIDES USED FOR CONTROL OF CITRUS BLACK SPOT IN SOUTH-AFRICA, Plant disease, 81(8), 1997, pp. 851-854
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.