Methods of testing insecticides against cocoa capsids in the field in Ghana

(1) Field trials with chlorinated hydrocarbon insecticides against capsids, done in 1956-60, are described and data used to discuss difficulties and improvements in the methodology of field trials. (2) The effects of spraying were assessed from the percentage of newly damaged trees and also the numbers of capsids at fortnightly intervals, and from the condition of the canopy every six months. (3) Analysis of the data showed that the initial effect to spraying are most efficiently assessed from the mean of the first two counts, wheter of new damage or of capsids. Trend in new damage (or capsids) is most efficiently assessed by the difference between first and last counts. By eliminating the need for repeated fortnightly counts the amount of labour can be halved. (4) The alternative methods of counting capsides or of assessing percentage of newly damaged trees are compared. The assessment of damage gave the more consistent and reliable results. (5) The problem of replication is discussed. From known ranges of variability between plots, the number of replicates needed to detect differences between effects of treatment ranging from 10 to 300 per cent are estimated. (6) Assessing the state of the canopy is considered as an alternative method to assessing trend in new damage. (7) Untreated control plots for assessing differences between treatments are unnecessary; their inclusion in analyses of variance increased variability and obscured differences between treated plots (Table 4). Controls are, however, essential for assessing canopy regeneration

Bibliographic Details

Main Authors:	81334 Johnson, C.G., 5331 Cocoa Research Institute, Tafo (Ghana), 33021 3. International Cocoa Research Conference Accra (Ghana) 23-29 Nov 1969
Format:	biblioteca
Published:	Tafo (Ghana) 1971
Subjects:	THEOBROMA CACAO, INSECTOS DAÑINOS, CONTROL DE INSECTOS, INSECTICIDAS, METODOS DE APLICACION, PULVERIZACION, SUPERFICIE FOLIAR, CAPSIDOS, GHANA,
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