Search

Maize lethal necrosis disease (MLND) has emerged as a major threat to maize production in East Africa. The disease is caused by a co-infection of maize by maize chlorotic mottle virus (MCMV) and sugarcane mosaic virus (SCMV) which are respectively vectored by corn thrips, Frakliniella williamsi Hood and corn leaf aphids, Rhopalosiphum maidis Fitch. Developing a reliable and practical sampling plan and action threshold for population monitoring of the two vectors is key for implementing a reliable integrated vector management strategy. A study was carried out to determine the sampling regime and action threshold levels for the vectors. Three maize stratas (upper, mid and lower foliage levels), three sampling intervals and five spray regimes using Thunder OD 145 (110 g/L Imidacloprid and 100 g/ L Betacyfluthrin 45 g/L) (were tested. The upper plant strata proved a preferred target for corn thrips (P < 0.001) while the lower section was preferred by corn leaf aphids during season 2(P = 0.03). Scouting at 8.30 to 10.30 am (P = 0.04) gave a better estimation of the vector infestation. Corn thrips infestation was significantly lower on maize sprayed on a weekly regime (P = 0.01). However, maize crop from thunder sprayed plots was MLND negative while the unsprayed maize crop was positive (P < 0.001). Although the yield from weekly sprayed plots was higher than any other treatments (P < 0.001), the net returns from monthly sprayed plots was higher. The action threshold level for corn thrips and corn leaf aphids was found to be six and three per plant respectively. These findings provide information on how, when and where to scout and spray for the two vectors. This may eventually lead to minimal wide spread of the virus by the vectors. [ABSTRACT FROM AUTHOR]

Understanding the demographic history and genetic make-up of colonizing species is critical for inferring population sources and colonization routes. This is of main interest for designing accurate control measures in areas newly colonized by vector species of economically important pathogens. The biting midge Culicoides imicola is a major vector of orbiviruses to livestock. Historically, the distribution of this species was limited to the Afrotropical region. Entomological surveys first revealed the presence of C. imicola in the south of the Mediterranean basin by the 1970s. Following recurrent reports of massive bluetongue outbreaks since the 1990s, the presence of the species was confirmed in northern areas. In this study, we addressed the chronology and processes of colonization in the Mediterranean basin. We characterized the C. imicola genetic structure of its populations across Mediterranean and African regions using both mitochondrial and nuclear markers, and combined phylogeographical analyses with population genetics and approximate Bayesian computation. We found a west/ east genetic differentiation between populations, occurring both within Africa and within the Mediterranean basin. We demonstrated that three of these groups had experienced demographic expansions in the Pleistocene, probably because of climate changes during this period. Finally, we showed that could have colonized C. imicola the Mediterranean basin in the Late Pleistocene or Early Holocene through a single event of introduction; however, we cannot exclude the hypothesis involving two routes of colonization. Thus, the recent bluetongue outbreaks are not linked to colonization event, but rather to biological changes in the vector or the virus. [ABSTRACT FROM AUTHOR]

In a co-digestion system running with rapeseed oil and sewage sludge, an extremely fast increase in the organic loading rate was studied to develop a procedure to allow for flexible and demand-driven energy production. The over-acidification of the digestate was successfully prevented by calcium oxide dosage, which resulted in granule formation. Mineralogical analyses revealed that the granules were composed of insoluble salts of long chain fatty acids and calcium and had a porous structure. Long chain fatty acids and calcium formed the outer cover of granules and offered interfaces on the inside thereby enhancing the growth of biofilms. With granule size and age, the pore size increased and indicated degradation of granular interfaces. A stable biogas production up to the organic loading rate of 10.4 kg volatile solids m–3 d–1 was achieved although the hydrogen concentration was not favorable for propionic acid degradation. However, at higher organic loading rates, unbalanced granule formation and degradation were observed. Obviously, the adaption time for biofilm growth was too short to maintain the balance, thereby resulting in a low methane yield. [ABSTRACT FROM AUTHOR]

Yields of commercially important crops in Kenya are often far below their potential. Amongst the possible reasons for such low yields may be the ecosystem degradation that can be expected to have negative impacts on pollinator presence in cropland, and the consequent food security issue for smallholder farmers who depend on these crops for their livelihood. Our study was carried out to assess the potential pollination deficit of French beans (Phaseolus vulgaris L.), a major export vegetable crop in Kenya grown by small-scale farmers. Sufficient pollination of French beans likely results in high seed set and uniform heavier green pods. Such pods get the highest grade while malformed pods are unmarketable, reducing family income. We hypothesized that pollination success was linked to the abundance and diversity of large pollinators, itself associated with the proximity to natural habitats. Flower visitors to French beans were sampled in 2011 and 2012 in ten farmer-managed plots, five within 200 m from the edge of Mt. Kenya forest and five farther away, more than 1000 m. Each plot measured 760 m2 and was planted at the same time, with the "Julia" variety. Flowers were observed for 2 h in each plot once weekly for three weeks at peak flowering from 0900-1100 h in the morning and 1200 – 1400 h in the afternoon on alternate days. Honey bees (Apis mellifera ) were the most abundant visitors of French bean flowers followed by carpenter bees (Xylocopa spp.) and leafcutter bees (Megachile spp.). Significantly higher numbers of leafcutter bees were recorded on farms far to the forest. There was no significant difference in honey bee abundance among the study sites, probably because apiaries and wild colonies are located across the landscape. French bean yield was significantly correlated with the mean abundance of carpenter bees in 2011. This suggests the possible occurrence of pollination deficit in French beans where the density of carpenter bees is insufficient, which was reflected by the high variability of yields in the farmland. We advocate that area-wide management and conservation of carpenter bees should be initiated to support French bean farming in the area. [ABSTRACT FROM AUTHOR]