Diversity and abundance of wild host plants of lepidopteran stem borers in two different agroecological zones of Kenya

Abstract

Abstract.A survey was carried out between 2004 and 2005 in two ecologically different locations, Kakamega and Muhaka to assess diversity and abundance of wild host plants of lepidopteran stem borers as compared to maize plots during the cropping and non-cropping seasons. Kakamega in Western Kenya is characterized by a Guineo-Congolian rain forest mosaic and Muhaka at the Kenyan coast by a Zanzibar Inhambane mosaic with secondary grassy and woody vegetation. In Kakamega, wild host plants and maize covered 2 and 43% of the surveyed area. No variation in diversity and relative abundance of wild host plants was observed between both the cropping and non-cropping seasons. In Muhaka, the diversity and relative abundance of wild host plant species differed between seasons, with the Shannon Weaver Index (H) of 1.67 and 0.95 for cropping and non-cropping seasons, respectively. Similarly in this location, wild host plant cover varied between cropping (23%) and noncropping (17.9%). During both seasons, this was higher than the maize cover, with 10.7% and 0% for the cropping and non-cropping seasons, respectively. For both localities, the implication of the differences found in the abundance and diversity between the cropping and non-cropping seasons is discussed.

Factors Affecting Stem Borer Parasitoid Species Diversity and Parasitism in Cultivated and Natural Habitats

“…In line with the resource concentration hypothesis (Root 1973) and previous results by Ndemah et al (2007) and Matama-Kauma et al (2008), stem borer density was generally low in natural habitats. Low stem borer host abundance in this study coupled with a high density of nonhost plant species in natural habitats existing in the same localities (Otieno et al 2006(Otieno et al , 2008 suggests host Þnding difÞculty of parasitoids in such habitats (Chabi-Olaye et al 2005). Moreover, parasitoids exhibit low Þtness and high mortality on wild host plants, as a consequence of low nutrition (Sé tamou et al 2005) and/or toxic phytochemicals or secondary plant compounds (Ode 2006).…”

“…Cereals were grown at subsistence level, with an average Þeld size of 0.28 ha located in open forest patches, or scattered around noncompact homesteads, and also along forest edges and the river bank. The area of natural habitats was 51.9%, of which the total relative cover of all potential wild host plants of stem borers was 0.5 and 0.3% during the rainy and dry seasons, respectively (Otieno et al 2006). In addition to growing Pennisetum purpureum Schumach for fodder, wild grass patches were numerous, mainly around crop Þelds or homesteads and along road sides and river banks, with a moderate level of connection between patches.…”

“…Cereals were grown at subsistence level, in Þelds scattered around a more compact homestead settlement. The area of natural habitats was 72.3%, of which the total relative cover of all potential wild host plants of stem borers was 2.2 and 1.0% during the rainy and dry seasons, respectively (Otieno et al 2006). Numerous wild grass patches were available surrounding crop Þelds and along major roads and around ponds.…”

Temporal patterns of emergence, calling behaviour and oviposition period of the maize stem borer,Busseola fusca(Fuller) (Lepidoptera: Noctuidae)

“…Th is insect species is mostly found on cultivated habitat and rarely on wild grasses (Le Ong'amo et al, 2006a;Ong'amo et al, 2006b;Otieno et al, 2006, Wale et al, 2006. Crop losses occur as the consequences of plant death, stem tunnelling, early leaf senescence and grain feeding (Bosque-Perez & Mareck 1991;Kfi r 1998).…”

Les recherches sur les lépidoptères foreurs des graminées et leurs antagonistes : bilan et perspectives

“…Ce nouvel essor de l'étude de la diversité spécifi que des foreurs est probablement lié à l'utilisation accrue de l'outil moléculaire qui, combiné à l'étude morphologique classique des espèces permet de mieux défi nir le statut taxonomique du matériel récolté . Beaucoup de ces foreurs se sont spécialisés sur une espèce végétale (monophagie) ou un petit nombre d'espèces appartenant à la même famille botanique (oligophagie) Ong'amo et al 2006 ;Otieno et al 2006). Une meilleure compréhension des mécanismes de sélection et d'adoption d'une plante hôte est illustrée par l'exemple de l'étude de l'équipement sensoriel de B. fusca .…”