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Articles by K. Yeboah-Gyan
Total Records ( 2 ) for K. Yeboah-Gyan
  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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