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Articles by J.A. Timbilla
Total Records ( 4 ) for J.A. Timbilla
  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.
  J.A. Timbilla , K. Yeboah-Gyan , B.W. Lawson and E. Woode
  Current research has shown that derivatives of pyrrolizidine alkaloids (PA) from the dry chopped roots of Chromolaena odorata (Asteraceae) are effective lures for Z. variegatus. Bioassays on the effect of a developed PA-based attracticides on 4th instar nymphs of Z. variegatus were conducted in the laboratory with a completely randomized design. The PA-source was the dry roots of C. odorata. The PA-attracticides evaluated comprised 300 g each of dry roots of C. odorata poisoned with three dilutions each of three standard insecticides, Carbofuran® 3G, Perfekthion® 40 EC and Karate® 2.5 EC, each with control treatment without attracticide. The insects were exposed to cassava (serving as feed) and the PA-attracticides in choice tests. The effects of the Carbofuran® 3G based PA-attracticides in knocking down Z. variegatus was concentration dependent while those of Perfekthion® 40 EC and Karate® 2.5 EC were not. The results showed that treating the dry chopped roots of C. odorata with as low as 0.5% w/v 3G Carbofuran derives an effective PA-based attracticide for the management of Z. variegatus. The results indicate that poisoning the dry roots of C. odorata could serve as a new management strategy for Z. variegatus. Here, the insect will be lured to its doom rather than spraying large hectares of infested fields with pesticides. On the other hand, the use of the dry roots of C. odorata as a lure will be contributing to the management of the weed which impacts negatively on agriculture and forestry.
  J.A. Timbilla , K. Yeboah-Gyan and B.W. Lawson
  The increasing importance of dry season populations of the African polyphagous grasshopper, Z. variegatus as a pest in agriculture and forestry has been attributed to the sequestration of pyrrolizidine alkaloids (PAs) from the flowers of the exotic noxious weed Chromolaena odorata for defense against natural enemies and protection of its diapausing eggs. This phenomenon is, however, seen as a novel opportunity to lure the insect with PAs for the development of PA-based attracticides for its management. This, notwithstanding, there is no empirical data on the efficacy of the available PA containing plants and the stage (s) of Z. variegatus worth targeting for the development of an integrated management strategy. Four categories of the growth stages of Z. variegatus were evaluated for the extent of migration to the roots of C. odorata, Heliotropium indicum and Crotalaria retusa which are plants containing PAs. Subsequently, fifth instar hoppers of Z. variegatus were evaluated for their attraction to the dry and fresh roots and flowers of C. odorata with a blank control in the laboratory. The results showed that 300 g of the dry chopped roots of C. odorata hold promise for use as PA-lures for the development of PA-based attracticides. The 3rd to 6th instar larvae of Z. variegatus have the highest degree of attraction to PAs. Also, the roots of C. odorata stored for a year are effective lures for the grasshopper while the flowers lose their attractive principle after 24 h. The results raise hope for the cost efficient and sustainable management of the grasshopper to salvage the agriculture and timber industries in Ghana and the sub region.
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