Assessing the potential economic impact of Bacillus thuringiensis (Bt) maize in Kenya

The Insect Resistant Maize for Africa (IRMA) project is currently developing Bt maize for Kenya. So far, Bt genes with resistance to Chilo partellus, Chilo orichalcociliellus, Eldana sacharina, and Sesamia calamistis, four of the five major stemborers were successfully incorporated into elite CIMMYT maize inbred line (CML216) and tested in insect bioassays in Kenya. Participatory Rural Appraisals showed that stem borers are indeed major pest problems for farmers. Four seasons of on-farm crop loss assessment showed an average crop loss of 13.5%, or 0.4 million tons, valued at US$80 million. If the project manages to find a Bt gene that is effective to the fifth stemborer, Busseola fusca, adoption rates are likely to be high, and therefore the returns. Under standard assumptions, the economic surplus of the project is calculated at$ 208 million over 25 years (66% of which is consumer surplus) as compared to a cost of $5.7 million. Geographically, the project should focus on the high production moist-transitional zone. However, if such gene cannot be found, Bt maize technology would only be effective in the low potential areas, and adoption rates would be fairly low, although benefits would still exceed costs.Key words: Maize, genetically modified crops, Bacillus thuringiensis, adoption, economic impact

The variable influence of dispersant on degradation of oil hydrocarbons in subarctic deep-sea sediments at low temperatures (0-5 °C)

The microbial degradation of petroleum hydrocarbons at low temperatures was investigated in subarctic deep-sea sediments in th e Faroe Shetland Channel (FSC). The effect of the marine oil dispersant, Superdispersant 25 on hydrocarbon degradation was also examined. Sediments collected at 500 and 1000 m depth were spiked with a model oil containing 20 hydrocarbons and incubated at ambient temperature (5 and 0 °C, respectively) with and without marine dispersant. Treatment of sediments with hydrocarbons resulted in the enrichment of Gammaproteobacteria, and specifically the genera Pseudoalteromonas, Pseudomonas, Halomonas, and Cobetia. Hydrocarbon degradation was faster at 5 °C (500 m) with 65-89% of each component degraded after 50 days compared to 0-47% degradation at 0 °C (1000 m), where the aromatic hydrocarbons fluoranthene, anthracene, and Dibenzothiophene showed no degradation. Dispersant significantly increased the rate of degradation at 1000 m, but had no effect at 500 m. There was no statistically significant effect of Superdispersant 25 on the bacterial community structure at either station. These results show that the indigenous bacterial community in the FSC has the capacity to mitigate some of the effects of a potential oil spill, however, the effect of dispersant is ambiguous and further research is needed to understand the implications of its use

The Present and Future Role of Insect-Resistant Genetically Modified Maize in IPM

Commercial, genetically-modified (GM) maize was first planted in the United States (USA, 1996) and Canada (1997) but now is grown in 13 countries on a total of over 35 million hectares (\u3e24% of area worldwide). The first GM maize plants produced a Cry protein derived from the soil bacteriumBacillus thuringiensis (Bt), which made them resistant to European corn borer and other lepidopteran maize pests. New GM maize hybrids not only have resistance to lepidopteran pests but some have resistance to coleopteran pests and tolerance to specific herbicides. Growers are attracted to the Btmaize hybrids for their convenience and because of yield protection, reduced need for chemical insecticides, and improved grain quality. Yet, most growers worldwide still rely on traditional integrated pest management (IPM) methods to control maize pests. They must weigh the appeal of buying insect protection “in the bag” against questions regarding economics, environmental safety, and insect resistance management (IRM). Traditional management of maize insects and the opportunities and challenges presented by GM maize are considered as they relate to current and future insect-resistant products. Four countries, two that currently have commercialize Bt maize (USA and Spain) and two that do not (China and Kenya), are highlighted. As with other insect management tactics (e.g., insecticide use or tillage), GM maize should not be considered inherently compatible or incompatible with IPM. Rather, the effect of GM insect-resistance on maize IPM likely depends on how the technology is developed and used

Parasitism of Lepidopterous Stem Borers in Cultivated and Natural Habitats

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

Biological control of the millet head miner Heliocheilus albipunctella in the Sahelian region by augmentative releases of the parasitoid wasp Habrobracon hebetor: effectiveness and farmers’ perceptions

On-farm augmentative releases of the parasitoid Habrobracon hebetor (Say) for controlling the millet head miner (MHM) Heliocheilus albipunctella (de Joannis) were tested in Burkina Faso, Mali and Niger from 2007 to 2009. In addition, a survey of farmers’ perceptions of insect pests, with particular focus on MHM, and the biological control program (BCP) was carried out. There was a significant increase of MHM parasitization rate after the releases, with up to 97% mortality. The survey on farmers’ perceptions revealed a fair knowledge of the MHM and the ability of farmers to describe the pest and the damage it caused. Farmers claimed that the biocontrol agent H. hebetor is effective and perceived a significant gain in grain yield due to this control strategy. Implications of these findings for a large extension of the MHM biocontrol program are discussed

Steborer research in Zimbabwe: prospects for the establishment of Cotesia flavipes Cameron

The stemborers Busseola fusca (Fuller) and Chilo partellus (Swinhoe) cause the highest economic damage to maize and sorghum in Zimbabwe. A number of studies on stemborer bioecology and management in Zimbabwe have been conducted, but most are still incomplete. The more important of these are studies on life history, incidence and distribution patterns, host plants, yield losses, chemical control, cultural control, host plant resistance, the use of sex pheromones, and biological control. These are discussed here in detail, and areas where further research is needed are pointed out. As part of an integrated strategy for managing stemborers in Zimbabwe, an exotic braconid larval parasitoid, Cotesia flavipes Cameron, has been released in the lowveld area and prospects for its establishment appear to be good. However, this establishment might be curtailed mainly by the inability of Co. flavipes to adapt to the seasonal carryover mechanisms utilised by the indigenous Cotesia sesamiae (Cameron). RÉSUMÉ Les foreurs Busseola fusca (Fuller) et Chilo partellus (Swinhoe) causent les plus grands dégâts économiques sur maïs et sorgho au Zimbabwe. A certain nombre d'études ont été menées sur la bio-écology et la gestion des foreurs au Zimbabwe, mais plusieurs sont encore inachevées. Les plus importantes d'entre elles sont: l'étude des cycles de vie, l'incidence et le mode de répartition, les plantes hôtes, les pertes de récoltes, la lutte chimique, les pratiques culturales, la résistance des plantes, l'utilisation de phéromones sexuels et la lutte biologique. Ces études sont discutées en détails dans cet article et les aspects nécessitant des études plus approfondies sont soulignées. Dans le cadre d'une strategie intégrée de la gestion des foreurs au Zimbabwe, un parasitoïde larvaire exotique, Cotesia flavipes Cameron, a été lâché dans la région de basse altitude et les possibilities d'acclimation semblent être excellents. Toutefois, cette acclimatation pourrait être limitée par l'inabilité de Co. flavipes à s'adapter aux mechanisms de passages saisoniers, utilisés par le parasitoïde local Cotesia sesamiae (Cameron)