A comparison of assessment methods in cocoa mirid control trials
Various methods of evaluating treatment effects in spray trials against the cocoa mirids Distantiella theobroma and Sahlbergella singularis are described and compared Pyrethrum knockdown mirid counts on sample trees gave an average more than x 12 mirids per unit area or tree than visual hand height counts on whole plots of half ha but there was good correlation between them so that either method was equally effective in showing differences between treatments. Proportionately more than twice as many Sahlbergella as Distantiella were recovered by Pyrethrum knockdown compared with visual counts. The category, trees infested with mirids, was found to be as effective as actual mirid counts, with a correlation coefficient of over 0.8. Canopy rating assessments an counts of trees with fresh damage matched the general trend of mirid counts but gave smaller and less significant differences between spray trial treatment means. Pod counts on sample trees or on whole plots gave good negative correlations (r= major 0.8) with eigher counts of infested trees or actual mirids during the previous peak mirid population period and together with canopy rating assessments gave a clear measure of the comparative overall success of an insecticide treatment over the growing season following a treatment cycle
| Main Authors: | , , |
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| Format: | biblioteca |
| Published: |
Tafo (Ghana)
1971
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| Subjects: | THEOBROMA CACAO, SAHLBERGELLA SINGULARIS, DISTANTIELLA THEOBROMAE, INSECTOS DAÑINOS, CONTROL DE INSECTOS, INSECTICIDAS, PIRETRINAS, PULVERIZACION, INFESTACION, MIRIDAE, |
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| Summary: | Various methods of evaluating treatment effects in spray trials against the cocoa mirids Distantiella theobroma and Sahlbergella singularis are described and compared Pyrethrum knockdown mirid counts on sample trees gave an average more than x 12 mirids per unit area or tree than visual hand height counts on whole plots of half ha but there was good correlation between them so that either method was equally effective in showing differences between treatments. Proportionately more than twice as many Sahlbergella as Distantiella were recovered by Pyrethrum knockdown compared with visual counts. The category, trees infested with mirids, was found to be as effective as actual mirid counts, with a correlation coefficient of over 0.8. Canopy rating assessments an counts of trees with fresh damage matched the general trend of mirid counts but gave smaller and less significant differences between spray trial treatment means. Pod counts on sample trees or on whole plots gave good negative correlations (r= major 0.8) with eigher counts of infested trees or actual mirids during the previous peak mirid population period and together with canopy rating assessments gave a clear measure of the comparative overall success of an insecticide treatment over the growing season following a treatment cycle |
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