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Susceptibility of two Cocoa Progenies to Attack by Insect Species. II—Effects of Canopy Size on Numbers of Mealybugs

Published online by Cambridge University Press:  03 October 2008

M. Bigger
M. Bigger
Affiliation:
Cocoa Research Institute, P.O. Box 8, Tafo, Ghana
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Summary

The main axis of a Principal Components Analysis, based on measurements of width and depth of canopy of two cocoa progenies was shown to be an index of canopy size and the second axis an index of shape. Mean scores of the progenies T85/799×T17/359 and E1:C43/291×T63/967 (Series IIB hybrid) on these axes showed that their canopies did not differ significantly in shape, but that the canopy size of Series IIB trees was on average greater than that of T85/799×T17/359. Regression lines of log numbers per tree of Planococcus citri Risso against canopy size of the two progenies were parallel, indicating that for a given canopy size P. citri was 2·3 times more prevalent in trees of Series IIB than in T85/799×T17/359. A similar analysis with the combined numbers per tree of seven mealybug species showed that they were 1·9 times more prevalent in Series IIB than in T85/799×T17/359 trees of the same size.

Type
Research Article
Information
Experimental Agriculture , Volume 11 , Issue 3 , July 1975 , pp. 193 - 199
Copyright
Copyright © Cambridge University Press 1975

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References

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