The assessment of mealybugs (Pseudococcidae) and other Homoptera on mature cocoa trees in Ghana

Abstract

The numbers of mealybugs and other Homoptera on 96 cocoa trees in Ghana were assessed by examining four branches from each tree. The trees were then felled and examined in detail. Ten species of mealybugs, eight other coccoids, an aphid and a psyllid were recorded. Ninety–five of the trees were infested with mealybugs, 66, 90 and 69 trees, respectively, with Planococcoides njalensis (Laing), Planococcus citri (Risso) and Phenacoccus hargreavesi (Laing). Stictococcus sjostedti Ckll., a species of Gascardia near G. zonata (Newst.) and Mesohomotoma tessmanni (Aulm.) were found on 70, 68 and 48 trees, respectively. The remaining 14 species were found on fewer than 48 trees. All species other than Pseudococcus calceolariae (Mask.) and Ferrisia virgata Ckll.) were most prevalent in the canopy. In the field, mealybug densities recorded on shoots underestimated true levels by an average of 95%. Branches were as effective as whole trees for detecting mealybugs, but less effective for other Homoptera. Branches were suitable sample units for estimating population densities of mealybugs, stictococcids and psyllids. All species of mealybug other than F. virgata infested vegetative buds. An average of 21.7% of buds on the youngest shoots were infested. Samples of buds can be used for detecting mealybug infestations.