The influence of overhead shade and fertilizers on the Homoptera of mature Upper-Amazon cocoa trees in Ghana.
1984
Campbell, C. A. M.
Homoptera were assessed by examining branches from mature cocoa trees in an Upper-Amazon 3 X 33 shade X nitrogen, phosphate and potash fertilizer experiment at Tafo, Ghana. Shade was supplied by Terminalia ivorensis at 2 spacings: 17 X 17 m (lightly shaded) and 8.6 X 8.6 m (heavily shaded). Trees in territories of the ants Crematogaster clariventris (Mayr) and Acantholepis capensis (Mayr) were sampled. Planococcoides njalensis (Laing), Planococcus citri (Risso), Phenacoccus hargreavesi (Laing), Pseudococcus concavocerarii James, Maconellicoccus ugandae (Laing) and Mesohomotoma tessmanni (Aulm.) were more abundant on unshaded trees than on shaded ones. Steatococcus sp. and Stictococcus sjostedti (Ckll.) also occurred most frequently on unshaded trees. The abundance of 5 other infrequently recorded species was unaffected by overhead shade. A species of Gascardia near G. zonata (Newst.) was more common as shade increased. Planococcus citri increased with increasing nitrogen where A. capensis was dominant, and decreased with increasing potassium on heavily shaded trees where C. clariventris was dominant. M. tessmanni decreased with increasing potassium both on unshaded trees where A. capensis was dominant and on trees which had received most phosphate where C. clariventris was dominant. No responses to fertilizers were detected among other species. An estimated 100, 99 and 83%, respectively, of unshaded, lightly and heavily shaded trees were infested with mealybugs, vectors of cocoa swollen shoot virus. These estimates presage little change in the rate of spread of virus due to the continued shade thinning over cocoa in Ghana.
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