The Spatial Distribution of the Cocoa Shield Bug, Bathycoelia Thalassina (H.-S.), and Its Implications for the Control of the Pest
The numbers of the separate cohorts of the cocoa shield bug Bathycoelia thalassina which were observed up to hand-height on 50 cocoa trees in a Nigerian cocoa farm were recorded. The data were analysed for any patterns of aggregation. In the egg as well as 1st to 3rd nymphal instar stages, B. thalassina was highly aggregated on individual cocoa trees and the coefficients of aggregation ranged from 2.14 to 2.77. In the 4th and 5th nymphal instar and the adult stages distribution was random and analyses of data in units of 1, 2, 4, 8 and 16 cocoa trees did not reveal any patterns of aggregation.
More egg batches were laid on stem than on pods and the least number of batches was found on the leaves. There was no significant difference in the size of batches laid on different plant parts (P < 0.05) and cocoa pods did not influence the choice of oviposition sites by B. thalassina.
The implication of this distribution pattern was discussed, and a suggestion made for spot application of insecticides on the eggs or 1st instar nymphs as a method of control that would be both economical and of ecological advantage.
Key WordsSpatial distribution control cocoa shield bug Bathycoelia thalassina cocoa
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