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The whitefly Bemisia tabaci (Gennadius) is the vector of cassava mosaic viruses causing cassava viral diseases, which are the most important biotic constraints of cassava production in sub-Saharan Africa (SSA). Presently, B. tabaci management in cassava fields calls for the development of an integrated approach that relies on host plant resistance and biological control. Data on B. tabaci's natural enemies, particularly parasitoids, in Central Africa are limited. Field surveys were conducted from 2015 to 2017 to identify parasitoids associated with B. tabaci in 5 Cameroon agro-ecological zones. Additionally, population dynamics studies were conducted in replicated fields experiments were conducted from 2016 to 2018 to identify cassava genotypes that can best promote B. tabaci parasitism. Two parasitoids, Encarsia sophia (Girault & Dodd) and Encarsia lutea (Masi) were found parasitizing B. tabaci nymphs with higher parasitism by E. lutea compared with E. sophia. The average parasitism rate during the survey was 33.4% for E. lutea and 8.4% for E. Sophia, regardless of AEZ. The highest parasitism rates by E. lutea (48.2% and 24.2% from field trials and surveys, respectively) were observed in the Western Highlands (AEZ 3) while parasitism by E. sophia was less than 12.4%. Four cassava genotypes (I090590, I011797, I090574, and I070593) promoted higher parasitism rates of B. tabaci by E. lutea and E sophia. The contributions of the two parasitoids and their integration with cassava genotypes for the management of B. tabaci in cassava fields are discussed. • Three-years countrywide surveys of Bemisia tabaci in Cameroon. • Encarsia lutea and E. sophia identified from parasitized B. tabaci nymphs. • Higher parasitism rate obtained from E. lutea. • Two cassava genotypes (I090590, I011797, I090574, and I070593) recorded the highest parasitism rates. • Total parasitism reached 39.2% regardless of the Agro-ecological zones. [ABSTRACT FROM AUTHOR]

The present research paper discussed the utilization of plant waste materials such as blast furnace flue dust and sludge as macro pellets and use of these macro pellets in the production of sinter. Wastes addition as pellets to the sinter modifies the productivity of the laboratory grade sinter machine as well as the better mechanical strength of sinter. At the same it also decreases the coke rate for sinter production. The maximum productivity achieved is 5t/m 2 /day at basicity 2.2(super fluxed sinter). Microstructure of the sinter of basicity 2.2 revels that it consists of re-oxidized hematite (Fe 2 O 3 ) and few magnetite (Fe 3 O 4 ) phases with some slag phase of calcium silicate(CaSiO 3 ). X-ray diffraction also confirms the presence of hematite and magnetite as the main constituents of the sinter. Although using these waste made pellets in the sintering process leads to decrease the coke consumption, simultaneously it is used as secondary raw material and at the same time it is eco-friendly also due to recirculation of hazardous wastes. [ABSTRACT FROM AUTHOR]

The nickel base superalloy, supercast 247A gains its appropriate microstructure and high temperature strength through precipitation hardening mechanism. Because of their service conditions, tensile properties of the alloy have strong influence on stability and life of the turbine blades. Tensile fracture mechanisms of the cast and heat treated superalloy were studied in ambient temperature, with a constant strain rate of 0.1 mm per minute. Scanning electron microscopy was used to provide structural and fractography evidence of the nickel base superalloy supercast 247A of different heat treatment conditions. The fractography results of the tensile tested specimens were in good agreement with the variation in alloy ductility. Many fractography features such as transgranular and intergranular fracture with fine dimples, cleaved facets and a combination of them were observed in the specimens tested at different heat treatment temperatures. [ABSTRACT FROM AUTHOR]

Abstract: Most smallholder farmers in developing countries depend on an informal Seed System (SS) for their seed. The informal SS is often criticized because farmer-produced seed samples are not tested for seed health, thus accepting the risk of planting infected seeds. Here we aimed at assessing the quality of seeds acquired from the informal SS, and compared this with the quality of seeds obtained from the formal SS. Cowpea seed production in northern Nigeria was used as a case study to evaluate the seed health of samples from farmers, seed companies, and foundation seed producers. In two years, a total of 45,500 seeds from 91 seed samples from 43 sources (farmers, seed companies and research) were tested for seed-borne bacteria and fungi by plating disinfested seed onto an agar medium. The most commonly isolated plant pathogens were Fusarium oxysporum (69% of the samples), Macrophomina phaseolina (76%) and Pseudomonas syringae pv. phaseolicola (48%). The infection incidence, the percentage of seeds infected per sample, varied from 0.2 to 75.6%. F. oxysporum had a median infection incidence of 9% in 2009 and 25% in 2010, while M. phaseolina had a median infection between 4 and 10%. On average, 8.8 species per sample were isolated from foundation seed, 9.2 from farmer-produced seed and 9.8 from seed companies'' seed. No evidence was found that seed recycling in the informal SS did lead to increased levels of seed-borne pathogens. In contrast to farmers, seed companies distribute seed over large distances, and therefore form a potential threat for spreading diseases at relatively large scale. Responsible authorities are recommended to make seed dressing mandatory for all seeds sold by seed companies. [Copyright &y& Elsevier]