Parasitism of Lepidopterous Stem Borers in Cultivated and Natural Habitats

Abstract

Plant infestation, stem borer density, parasitism, and parasitoid abundance were assessed during two years in two host plants, Zea mays (L.) (Cyperales: Poaceae) and Sorghum bicolor (L.) (Cyperales: Poaceae), in cultivated habitats. The four major host plants (Cyperus spp., Panicum spp., Pennisetum spp., and Sorghum spp.) found in natural habitats were also assessed, and both the cultivated and natural habitat species occurred in four agroecological zones in Kenya. Across habitats, plant infestation (23.2%), stem borer density (2.2 per plant), and larval parasitism (15.0%) were highest in maize in cultivated habitats. Pupal parasitism was not higher than 4.7% in both habitats, and did not vary with locality during each season or with host plant between each season. Cotesia sesamiae (Cameron) and C. flavipes Cameron (Hymenoptera: Braconidae) were the key parasitoids in cultivated habitats (both species accounted for 76.4% of parasitized stem borers in cereal crops), but not in natural habitats (the two Cotesia species accounted for 14.5% of parasitized stem borers in wild host plants). No single parasitoid species exerted high parasitism rates on stem borer populations in wild host plants. Low stem borer densities across seasons in natural habitats indicate that cereal stem borer pests do not necessarily survive the non-cropping season feeding actively in wild host plants. Although natural habitats provided refuges for some parasitoid species, stem borer parasitism was generally low in wild host plants. Overall, because parasitoids contribute little in reducing cereal stem borer pest populations in cultivated habitats, there is need to further enhance their effectiveness in the field to regulate these pests.

Evaluation of tropical maize inbred lines for resistance to two stem borer species, Busseola fusca and Chilo partellus

“…The results from the current study agree with the findings of Ajala et al, (2010), Akinwale et al (2011), andMailafiya et al, (2011) reported that leaf damage and cumulative tunneling were positively correlated. These may show differences among B. fusca and C. partellus nature of feeding, stem tunneling, oviposition, and exit from host plants.…”

“…The spotted stem borer (Chilo partellus Swinhoe) Pyralidae and African stem borer (Busseola fusca Fuller) Noctuidae, Lepidoptera are among the most damaging insect pests that greatly reduce maize grain yield in east African environments (Citation). Tropical environments are favourable for insect development and lead to the formation of several generations of the pests in the same season leading to severe crop yield losses (Mailafiya et al, 2011). For example, in Kenya, grain yield loss due to stem borers in maize is estimated annually at about 400,000 metric tons or about $72 million (De Groote et al, 2003;De Groote et al, 2005).…”

“…Suitable maize germplasm should have resistance to both B. fusca and C. partellus. Recent reports indicate that climate change has led to C. partellus increasingly displacing B. fusca from the high altitude areas in Kenya (Mailafiya et al, 2011;Tefera et al, 2011;Mwimali et al, 2015). Furthermore, farmers exchange maize germplasm across agroecologies, therefore, the need to investigate the reaction of these tropical maize inbred lines for resistance to these borers becomes paramount.…”

Quantitative trait loci for resistance to spotted and African maize stem borers (Chilo partellus and Busseola fusca) in a tropical maize (Zea mays L.) population

“…Increased maize productivity beyond the current two (2) tons per hectare is critical for food security in sub-Saharan Africa. The stem borers are some of the major pests that account for the low maize production, with lepidopteran stem borers, including the African stem borer (Busseola fusca Fuller), the spotted stem borer (Chilo partellus Swinhoe) and the pink stem borer (Sesamia Calamistis Hampson) being the most damaging pests in eastern and southern Africa, where they cause 13 to 40% yield losses (De Groote, 2002;Mailafiya et al, 2011). In Kenya, the major maize stem borer species are C. partellus, B. fusca and S. calamistis.…”

Combining ability for stem borer resistance and heterotic orientation of maize inbred lines using CIMMYT single cross testers under Chilo partellus infestation

“…Chilo partellus occupied Africa from Asia before 1930's and accounts for 90% of the stem borers in the lowland tropics, mid altitude and the moist transitional areas of East Africa (Ong'amo et al, 2012). The distribution and occurrence of C. partellus stem borers in different crop ecosystems is affected by host availability, location and suitability, mate location, success of oviposition, larval survival and establishment, temperature and altitude (Mailafiya et al, 2011;Ong'amo et al, 2012). Although C. partellus is absent in the highland tropics, it is progressively intensifying its range to higher altitudes, and currently, it is the most widely distributed stem borer in the maize growing zones in Kenya (Kfir et al, 2002;Tefera et al, 2011).…”