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

Sampling lepidopterous pests on maize in West Africa

The spatial distribution of five lepidopterous pests, Sesamia calamistis Hampson (Noctuidae), Eldana saccharina Walker (Pyralidae), Spodoptera exempta (Walker) (Noctuidae), Mussidia nigrivenella (Ragonot) (Pyralidae), and Cryptophlebia leucotreta (Meyrick) (Tortricidae), on maize in West Africa is described using Taylor's power law and the relationship of proportion of infested plants to the mean density. All five species showed a highly aggregated distribution, with Taylor's indices of aggregation ranging between 1.23 for C. leucotreta and 1.52 for Sesamia calamistis. Enumerative and binomial sampling plans that incorporate Taylor's power law are proposed to estimate mean densities of S. calamistis, C. leucotreta and the species complex consisting of E. saccharina, M. nigrivenella and Spodoptera exempta which showed similar spatial distributions, with a predefined reliability level

Multitrophic interactions in cassava, Manihot esculenta, cropping systems in the subhumid tropics of West Africa

The effect of fertilizer and mulch across tropic level of the cassava ecosystem, i.e. the plant, the cassava mealybug(CM), the wasp Apoanagyrus lopezi and its hyperparasitoids, was studied in two field experiments planted ins southern Benin. Several cassava cultivars with different branching patterns and varying susceptibility to the cassava mealbug were planted on a sandy loamy and a sandy soil, respectively. Four to seven months after application of the soil treatments, differences in N.P.K in the first 50cm of the soil had mostly disappeared, indicating that the soil nutrients had been taken up by the plant and/or had leached to deeper layers of the soil

Journal of extracellular vesicles

Plasma and other body fluids contain cell-derived extracellular vesicles (EVs), which participate in physiopathological processes and have potential biomedical applications. In order to isolate, concentrate and purify EVs, high-speed centrifugation is often used. We show here, using electron microscopy, receptor-specific gold labelling and flow cytometry, that high-speed centrifugation induces the formation of EV aggregates composed of a mixture of EVs of various phenotypes and morphologies. The presence of aggregates made of EVs of different phenotypes may lead to erroneous interpretation concerning the existence of EVs harbouring surface antigens from different cell origins

Effet de la fumure en potassium sur le developpement, la survie et la fecondite de Sesamia calamistis Hampson (Lepidoptera: Noctuidae) et de Eldana saccharina Walker (Lepidoptera: Pyralidae)

The effect of potassium application to maize plants on the development, survival and fecundity as well as larval and pupal weight of Sesamia calamistis and Eldana saccharina were studied in the laboratory. Six different potassium treatments corresponding to 0, 30, 60, 60, 90, 120 and 150 kg K2O/ha were used. Potassium had no influence on larval and pupal developmental time or longevity of adult S. calamistis. The highest larval mortality was observed at 0 and at 150 kg K2O/ha. Increased doses (> 60 kg K2O/ha.) tended to reduce pupal survival. The lowest pupal weight was obtained at 150 kg/ha whereas fecundity was negatively related with potassium. The highest values of intrinsic rate of increase (rm) and net reproductive rate (Ro) were obtained with 60 kg K2O/ha and lowest with 150 kg K2O/ha. For E. saccharina, potassium had no significant effect on larval and pupal developmental time, larval survival, and pupal weight. The highest larval weight, pupal survival and fecundity as well as rm and Ro values were observed at 90 kg K2O/ha

Review: Annexin-A5 and cell membrane repair

Annexins are soluble proteins that bind to biological membranes containing negatively charged phospholipids, principally phosphatidylserine, in a Ca2+-dependent manner. Annexin-A5 (AnxA5), the smallest member of the annexin family, presents unique properties of membrane binding and self-assembly into ordered two-dimensional (2D) arrays on membrane surfaces. We have previously reported that AnxA5 plays a central role in the machinery of membrane repair by enabling rapid resealing of plasma membrane disruption in murine perivascular cells. AnxA5 promotes membrane repair via the formation of a protective 2D bandage at membrane damaged site. Here, we review current knowledge on cell membrane repair and present recent findings on the role of AnxA5 in membrane resealing of human trophoblasts. (C) 2015 Published by IFPA and Elsevier Ltd

Exchanging natural enemies species of lepidopterous cereal stemborers between African regions

Difficulties of identification of natural enemies of cereal stemborers for 'redistribution' in Africa are discussed. Tritrophic level studies on wild and cultivated habitats of borers and beneficial species are needed to judge the impact of a natural enemy species in the cropping system. Areas witli low Pest pressure which are climatically favorable for Pest development may be selected for study. Based on the results of various countrywide surveys to map the relative importance of Sesaniia calnmistis Hampson, Eldam sncc@rim (Walker) and Busseola fuscn (Fuller) in western Africa, recommendations are given for sites for tritrophic level studies. It is hypothesised that because maize is not always present in the field and because of its high susceptibility, natural biological control has to come I'rom wild habitats. This emphasises the importance of the knowledge on the wild host-plant range. Survey results complemented with oviposition and life-table studies in the laboratory showed that, ratlier than being reservoirs for pests, most wild grass species act as trap plants causing mortalities of 100%. A comparison of light trap catches with pupae found on wild hosts and the scarcity of known wild hosts in areas with high Pest pressure suggest gaps in Our knowledge of the range of host plant species. Based on comparison of known natural enemy complexes in East and West Africa, the scelionid egg parasitoid Teleriorrius isis and an East African strain of the braconid larval parasitoid Cotesia sesainine (Cameron) are proposed for redistribution against B. fuscn and S. calaniis fis, respectively. Telenonius isis has never been reported from East Africa whereas C. sesaniiae is common in East and southern Africa and scarce in western Africa, suggesting that C. sesaniiae is probably not adapted to S. culnmistis and B.fiisca in this region

Frequency of Sahelian storm initiation enhanced over mesoscale soil-moisture patterns

Evapotranspiration of soil moisture can affect temperature and humidity in the lower atmosphere, and thereby the development of convective rain storms. Climate models have illustrated the importance of soil-moisture–precipitation feedbacks for weekly rainfall totals in semi-arid regions, such as the Sahel1. However, large variations exist between model feedbacks, and the mechanisms governing the strength and sign of the feedback are uncertain. Here, we use satellite observations of land surface temperatures and convective cloud cover over West Africa—collected during the wet seasons between 2006 and 2010—to determine the impact of soil moisture on rainfall in the Sahel. We show that variations in soil moisture on length scales of approximately 10–40 km exert a strong control on storm initiation—as evidenced by the appearance of convective cloud. The probability of convective initiation is doubled over strong soil-moisture gradients compared with that over uniform soil-moisture conditions. We find that 37% of all storm initiations analysed occurred over the steepest 25% of soil-moisture gradients. We conclude that heterogeneities in soil moisture on scales of tens of kilometres have a pronounced impact on rainfall in the Sahel, and suggest that similar processes may be important throughout the semi-arid tropics