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Articles by B.W. Lawson
Total Records ( 2 ) for B.W. Lawson
  J.A. Timbilla , B.W. Lawson and K. Yeboah-Gyan
  Cabbage, Brassica oleraceae var. capitata is an important vegetable grown and consumed in Ghana. Apart from infestations of the lepidopterous Plutella xylostella and Hellula undalis resulting from continuous cultivation, a new pest Zonocerus variegatus has been reported to causing damage to the crop. The efficacy of a novel pyrrolizidine alkaloid (PA) based novel PA-attracticide developed from treating the roots of the neophyte, Chromolaena odorata which contains PAs with Carbofuran 3G for the management of Z. variegatus was tested using cabbage as a test crop in field caged plots. Field caged plots of cabbage artificially infested with Z. variegatus were treated with and without PA-attracticide in addition to a control treatment of caged cabbage plot with no insect and PA-attracticide. The experimental design was a RCB replicated three times in two ecological zones. The results showed that the establishment, leaf and head damage of cabbage was statistically the same in the PA-treated plots and the control treatment. These treatments, however, performed significantly better than the treatment without PA-attracticide. The results obtained holds promise for mitigating the menace of the grasshopper on cabbage using PA based attracticides.
  J.A. Timbilla and B.W. Lawson
  In Sub Saharan Africa seasonal outbreaks of Zonocerus variegatus coincide with the introduction of the neophyte Chromolaena odorata. Zonocerus variegatus is known to feed on the flowers of C. odorata which contain Pyrrolizidine Alkaloids (PAs), known to protect the grasshopper. A study was carried out with the objective to establish any possible link between the introduction of C. odorata and the outbreak of Z. variegatus. Questionnaire and field surveys were carried out in Ghana to determine the distribution, density and pest status of Z. variegatus and C. odorata and also to assess the seasonal populations of Z. variegatus with respect to the occurrence of flowers of C. odorata. The results indicated that C. odorata has spread as far north as latitude 8°30', an increase of 15' within a decade. The occurrence, density and outbreak of the dry season population of the uni-voltine Z. variegatus are related to the distribution of C. odorata which is also dependent on the rainfall pattern. In areas with dry season outbreaks of Z. variegatus, C. odorata occurs and the rainfall pattern is bi-modal. In the north where C. odorata is absent with only one population of Z. variegatus, the latter assumes pest status in isolated spots. The results indicate a strong linkage between the outbreak of dry season populations of Z. variegatus and the presence of Pas from the flowers of C. odorata, thus proving the existing pharmacophagous relationship proposed between the insect and the weed.
 
 
 
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