Importance of wild host plants for stem borer parasitoid diversity and control of parasitism in cereal cropping ecosystems in Kenya

摘要

Field studies were carried out over 2 years (2005-2007) at four locations in Kenya to assess the effects of three plant families (Poaceae, Cyperaceae and Typhaceae) on parasitoid diversity and stem borer parasitism in natural habitats. Field collections were made using destructive sampling. Per locality, stem borer abundance was highest in Poaceae (>69%). Stem borer density per plant (<0.081) did not vary amongst plant families within each locality. Stem borer parasitism was highest in Poaceae in most localities (0.49-2.84%). Although stem borer diversity (Shannon index (H')) (H'= 0.09-2.47) did not vary among plant families per locality, stem borer diversity and dominance were positively correlated with parasitism in Poaceae and Cyperaceae. Presentresults show that Poaceae, Cyperaceae and Typhaceae are important plant families for sustaining parasitoid diversity or function in natural habitats and adjacent cultivated habitats within the cereal crop ecosystem. Wild host plants that harbour parasitoid species or stimulate stem borer activity could also regulate stem borer populations within the cropping ecosystem. Indiscriminate destruction of wild host plants in the Poaceae, Cyperaceae and Typhaceae surrounding cultivated cereal crops should thusbe avoided.