Adsorption of phenol from aqueous solutions onto natural and thermallymodified kaolinitic materials

Phenol removal from aqueous solutions by kaolinite (KAO) and metakaolinite (MET) have been carried out at 25 °C in batch mode to evaluate the effects of parameters such as pH, initial phenol concentration and adsorbent mass on the extent of adsorption. It was observed that phenol uptake increased with increases in adsorbent concentration at maximum pH of 2 and equilibrium time of 40 minutes for both KAO and MET. Results showed that pseudo second-order kinetic model best describes the chemisorption of phenol from aqueous solutions onto the two clay samples. The low correlation coefficient of the intraparticle diffusion model proves that pore diffusion plays little or no significant role in the adsorption of phenol onto KAO and MET. Also, from adsorption isotherm analysis, only the Temkin equation modeled best the adsorption process of phenol from aqueous solutions onto MET while the Freundlich and Temkin models best described the adsorption of phenol onto KAO. Maximum adsorption capacity for KAO and MET were 1.71 and 5.82 mg/g respectively through Langmuir model equation. It can be inferred from experimental results and modeled parameters that clay samples are not very effective for the removal of phenol from aqueous solution.Keywords: Environment, clays, organic pollutants, Kinetic models, Isotherm models

Atoxigenic-based technology for biocontrol of aflatoxin in maize and groundnuts for Tanzania

Article in Press; Published online: 10 Aug 2022Application of biocontrol products containing atoxigenic isolates of Aspergillus flavus to reduce aflatoxin content in crops is an effective strategy for managing aflatoxin in several regions throughout the world. We report the development and validation of two aflatoxin biocontrol products, Aflasafe TZ01 and Aflasafe TZ02, for use in maize and groundnut in Tanzania, a country frequently affected by aflatoxin contamination. Each product contains four atoxigenic A. flavus genotypes native and widely distributed in Tanzania. Efficacy tests on maize and groundnut were conducted over two years and in four regions of Tanzania where aflatoxin contamination is prevalent. Application of both products significantly (P<0.05) reduced aflatoxin levels in maize and groundnut in both years and in all districts. No differences were observed in total Aspergillus section Flavi population in treated and untreated fields, revealing that application of the biocontrol products do not alter overall Aspergillus populations in the environment. The results indicate that both products are effective tools for aflatoxin mitigation in groundnut and maize. The products were officially registered in 2018. Currently, there are scale-out and-up efforts of aflatoxin biocontrol products in Tanzania through a private sector company that is making the products available to farmers. Protecting maize and groundnut from aflatoxin contamination in Tanzania can result in health, income, and trade benefits

DISTRIBUTION AND SPECIES COMPOSITION OF CEREAL STEMBORERS IN THE EASTERN ZONE OF TANZANIA

A survey was conducted in the four regions of Tanga, Morogoro, Coast and Dar es Salaam in eastern Tanzania to determine the distribution and species composition of cereal stemborers and their natural enemies. A total of 22 fields were sampled in Tanga, 28 in Morogoro, 17 in Coast and one in Dar es Salaam. Chilo partellus was found to be the predominant species, accounting for 80 % of all stemborers collected. Busseola fusca, Sesamia calamistis and Chilo orichalcociliellus made up 15, 4 and less than 1 % of the stemborers collected respectively. Infestation levels varied with the age of the plants, whereby younger plants were more severely infested (infestation ranging from 20 - 40 %) than mature plants (infestation ranging from 5 - 15 %). Two larval parasitoids, Cotesia sesamiae and Cotesia flavipes, were the main natural enemies collected. However, the levels of parasitism of the stemborers were very low. The exotic natural enemy Co. flavipes may have spread from the Kenya coast (where it is established) into eastern Tanzania. RÉSUMÉ Une enquête a été menée dans les quatre régions de Tanga, Morogoro, Coast et Dar es Salaam dans l'est de la Tanzanie afin de déterminer la distribution et la composition en espèces des foreurs de tige de céréales et de leurs ennemis naturels. Au total, 22 champs ont été échantillonnés dans Tanga, 28 dans Morogoro, 17 dans Coast et un dans Dar es Salaam. Chilo partellus est l'espèce dominante, il représente 80% de tous les foreurs des tiges récoltés. Busseola fusca, Sesamia calamistis et Chilo orichalcociliellus représentent respectivement 15, 4 et moins de 1 % des foreurs de tige récoltés. Les niveaux d'infestation varient avec l'âge des plantes; ainsi les plantes les plus jeunes sont plus sévèrement infestées (l'infestation est comprise entre 20 - 40%) que les plantes mûres (l'infestation est comprise entre 5 et 15%). Deux parasitoïdes larvaires, Cotesia sesamiae et Cotesia flavipes, sont les principaux ennemis naturels récoltés. Cependant, les niveaux de parasitisme des foreurs des tiges sont très bas. L'ennemi naturel exotique Co. flavipes a dû s'étendre de la côte kenyanne (où il est établi) vers la côte tanzanienne

Distribution and abundance of cassava pests in Tanzania with a note on the spiralling whitefly

Two surveys were conducted in Tanzania in May- June 2003 and June-August 2004 to determine the incidence and severity of several cassava arthropod pests including cassava green mite, cassava mealybug, spiralling whitefly, Bemisia spp., cassava scale, red mite, Zonocerus elegans, and several species of termites. Cassava green mite densities were relatively low except in the Lake region in 2004. The introduced phytoseiid predator of cassava green mite Typhlodromalus aripo was found in all regions, with the highest abundance in the Eastern and Lake regions in 2003, and in the Eastern region in 2004. Cassava mealybug infestations were very low throughout the surveyed regions, while B. tabaci (probably in mixed infestations with B. afer) were found in all regions but never exceeding 5 nymphs per leaf. Termite damage was widespread but impact on plant growth and yield is not known. Cassava scale was found only in few fields in the Southern Highlands, Lake and Eastern regions, with damage severity ranging from 2 to 4 (on a scale of 1 to 5). The spiralling whitefly Aleurodicus dispersus, first recorded in Zanzibar in 2002, was found for the first time on the mainland, but only in the Eastern region and at low infestation levels

Achievements and outcomes in implementation of Napier smut and stunt resistance project in Tanzania

A presentation to the ASARECA/ILRI Workshop on Mitigating the Impact of Napier Grass Smut and Stunt Diseases, Addis Ababa, June 2-3, 2010

Biology and management of Bemisia whitefly vectors of cassava virus pandemics in Africa

Cassava mosaic disease and cassava brown streak disease are caused by viruses transmitted by Bemisia tabaci and affect approximately half of all cassava plants in Africa, resulting in annual production losses of more than $US 1 billion. A historical and current bias towards virus rather than vector control means that these diseases continue to spread, and high Bemisia populations threaten future virus spread even if the extant strains and species are controlled. Progress has been made in parts of Africa in replicating some of the successes of integrated Bemisia control programmes in the south-western United States. However, these management efforts, which utilise chemical insecticides that conserve the Bemisia natural enemy fauna, are only suitable for commercial agriculture, which presently excludes most cassava cultivation in Africa. Initiatives to strengthen the control of B. tabaci on cassava in Africa need to be aware of this limitation, and to focus primarily on control methods that are cheap, effective, sustainable and readily disseminated, such as host-plant resistance and biological control. A framework based on the application of force multipliers is proposed as a means of prioritising elements of future Bemisia control strategies for cassava in Africa

Biological control of cassava green mite in Tanzania

The cassava green mite Mononychellus tanajoa (Bondar) (Acari: Tetranychidae) is one of the most important pests of cassava, a main staple food crop in Tanzania. The International Institute of Tropical Agriculture (ETA) in collaboration with the Tanzania National Biological Control P r o m (NBCP) launched in 1998 the biological control campaign against cassava green mite in Tanzania with the release of the neotropicd phytoseiid predator Z)phlodromallus aripo DeLeon (Acari: Phytoseiidae), which had proven to be an efficient biological control agent of the cassava green mite in West Mca. The campaign consisted of new introductions and redistributions of I: aripo from infested cassava shoot tips, follow-up surveys to determine establishment, spread, and impact, as well as extension and farmer training on pest and natural enemy recognition and means of enhancing predator efficacy. ~phlodromallusa ripo was h t fo und in March 1998 in the Tanga region, most likely invading h m the southern Kenya coast where it was released in 1996. Subsequently, the Tanzania NBCP in close collaboration with IITA has carried out numerous introductions and redistributions of the predator. Surveys conducted in the following 6 years revealed success M establishment, persistence and spread in five agro-ecological zones including the Lalce (Mars and Kagera regions, except parts of Mwanza region), Western (Kigorna region except Shinyanga region), Southern Highlands (Mbeya and Iringa region), Eastem (Tanga and Coast regions) and Southern (Lindi and Mtwara regions) zones. Up to 2005, there was still no T. arip in parts of 3 regions: Mwanza, Shinyanga and Ruvuma. Cassava green mite mean densities have declined to low levels (less than 20 actives per leaf) in all regions where 'I: a r b has been present. In on-fm impact assessment trial, 'I: aripo was capable of reducing population density of cassava green mite by 64.3% and increasing total and marketable cassava root weights by 61.2% and 71.7%, respectively. There was also a significant increase in total number of roots (25.4%), number of marketable roots (45.78%), stem weights (47.39%), and leaf weight (40.7%) where T, aripo was not eliminated. This report present evidence of the impact of biological control on cassava green mite populations and cassava yield in Tam&, and recommends the use of exotic isolates of the fungal pathogen Neozygites tanajoae, which has been established in West Africa, as a complementary alternative approach in controlling further the cassava green mite in the remaining spots of high infestations