The phytochemical composition of Melia volkensii and its potential for insect pest management

Due to potential health and environmental risks of synthetic pesticides, coupled with their non-selectivity and pest resistance, there has been increasing demand for safer and biodegradable alternatives for insect pest management. Botanical pesticides have emerged as a promising alternative due to their non-persistence, high selectivity, and low mammalian toxicity. Six Meliaceae plant species, Azadirachta indica, Azadirachta excelsa, Azadirachta siamens, Melia azedarach, Melia toosendan, and Melia volkensii, have been subject to botanical pesticide evaluation. This review focuses on Melia volkensii, which has not been intensively studied. M. volkensii, a dryland tree species native to East Africa, has shown activity towards a broad range of insect orders, including dipterans, lepidopterans and coleopterans. Its extracts have been reported to have growth inhibiting and antifeedant properties against Schistocerca gregaria, Trichoplusia ni, Pseudaletia unipuncta, Epilachna varivestis, Nezara viridula, several Spodoptera species and other insect pests. Mortality in mosquitoes has also been reported. Several limonoids with a wide range of biological activities have been isolated from the plant, including volkensin, salannin, toosendanin, trichilin-class limonoids, volkendousin, kulactone among others. This paper presents a concise review of published information on the phytochemical composition and potential of M. volkensii for application in insect pest management

Metagenomic analyses and genetic diversity of Tomato leaf curl Arusha virus affecting tomato plants in Kenya.

Funder: Bill and Melinda Gates Foundation; doi: http://dx.doi.org/10.13039/100000865BACKGROUND: Tomato production is threatened worldwide by the occurrence of begomoviruses which are associated with tomato leaf curl diseases. There is little information on the molecular properties of tomato begomoviruses in Kenya, hence we investigated the population and genetic diversity of begomoviruses associated with tomato leaf curl in Kenya. METHODS: Tomato leaf samples with virus-like symptoms were obtained from farmers' field across the country in 2018 and Illumina sequencing undertaken to determine the genetic diversity of associated begomoviruses. Additionally, the occurrence of selection pressure and recombinant isolates within the population were also evaluated. RESULTS: Twelve complete begomovirus genomes were obtained from our samples with an average coverage of 99.9%. The sequences showed 95.7-99.7% identity among each other and 95.9-98.9% similarities with a Tomato leaf curl virus Arusha virus (ToLCArV) isolate from Tanzania. Analysis of amino acid sequences showed the highest identities in the regions coding for the coat protein gene (98.5-100%) within the isolates, and 97.1-100% identity with the C4 gene of ToLCArV. Phylogenetic algorithms clustered all Kenyan isolates in the same clades with ToLCArV, thus confirming the isolates to be a variant of the virus. There was no evidence of recombination within our isolates. Estimation of selection pressure within the virus population revealed the occurrence of negative or purifying selection in five out of the six coding regions of the sequences. CONCLUSIONS: The begomovirus associated with tomato leaf curl diseases of tomato in Kenya is a variant of ToLCArV, possibly originating from Tanzania. There is low genetic diversity within the virus population and this information is useful in the development of appropriate management strategies for the disease in the country

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Records of Arthropod Species Sampled from Avocado Plant (Persea americana Mill) in Smallscale Agro-ecosystems at Taita Hills and Mount Kilimanjaro

Avocado, Persea americana Mill, plays a central role in distribution of both beneficial and detrimental arthropods thereby influencing local species diversity in agro-ecosystems adjacent to Afromontane forests at Mount Kilimanjaro in North-eastern Tanzania and Taita Hills in South-eastern Kenya. However, little is known about arthropod species that inhabit avocado trees in the two study areas despite the fact that the crop forms the major part of agro-ecosystem in the East African highlands. A novel survey was, therefore, carried out for two years between August 2012 and July 2014 to establish arthropod species in avocado orchards along South-eastern slopes of both Mount Kilimanjaro and Taita Hills. A total of sixty one species of arthropods were recorded from the avocado crop through fruit observation and canopy sampling. The present arthropod checklist provides baseline knowledge for scientists in evaluating beneficial and pest status of each species inhabiting avocado plant in the East African agro-ecosystems.Peer reviewe

Spatial characterization of common blossom thrips (Frankliniella schultzei) in smallholder avocado orchards along slopes of Taita Hills and Mount Kilimanjaro

Frankliniella schultzei Trybom (Thysanoptera:Thripidae) is an important flower pest of avocado crop (Persea americana Mill) at Taita Hills in South-eastern Kenya and Mount Kilimanjaro in North-eastern Tanzania. However, its geographical distribution is not known in the East African avocado cropping systems. In order to generate the spatial data of the common blossom thrips (Frankliniella schultzei), a survey was carried out in smallholder avocado orchards along altitudinal gradient (900 -1800m.a.s.l.) of Taita Hills and Mount Kilimanjaro using a white coloured beating tray and camel brush. Once the specimens of thrips were taxonomically verified, the abundance data was tabulated into three altitudinal zones, namely; lowland (900-1199m.a.s.l.), sub-montane (1200-1499m.a.s.l.) and montane (1500-1799m.a.s.l.). Frankliniella schultzei was recorded in all altitudinal zones of both transects with mean abundance being highest at Taita Hills (5.4) compared to Mount Kilimanjaro (0.9). However, abundance of the pest was greater in cooler highlands (>1200m.a.s.l.) than warmer lowland areas (<1200m.a.s.l.) of both transects. The findings of this study contributes significantly towards spatial mapping of Frankliniella schultzei in East Africa and this information is important in developing strategies aimed at controling infestation of avocado flowers by the insect pest at the two study transects.Peer reviewe

Datasets on abundance of common blossom thrips and weather variables in small-scale avocado orchards at Taita Hills and Mount Kilimanjaro

Avocado, Persea americana Miller (Lauraceae), is an important fruit crop cultivated by small-holder farmers along Afrotropical highlands of Taita Hills in South-eastern Kenya and Mount Kilimanjaro in Northern Tanzania. The small-holder farmers in these East African regions generate substantial food and cash from avocado fruits. However, the avocado crop is faced with challenges of infestation by insect pests such as the common blossom thrips (Frankliniella schultzei Trybom) which feeds on pollen and floral tissue thereby reducing productivity of the trees. Moreover, there is no information describing distribution patterns of Frankliniella schultzei and associated weather in East African avocado orchards despite the fact that small-scale farming is dependent on rainfall. This article was, therefore, initiated to provide dataset on abundance of Frankliniella schultzei from the avocado plants that relates with monthly rainfall and air temperatures at Taita Hills and Mount Kilimanjaro. Frankliniella schultzei was collected using white coloured beating tray and camel brush whereas air temperatures (°C) and rainfall (mm) was recorded daily using automatic data loggers and rain gauge, respectively. The survey at the two transects commenced during peak flowering season of avocado crop in August up to end of harvesting period in July of the following year. Temporal datasets were generated by Kruskal-Wallis Chi-square test. Current temporal datasets presents strong baseline information specifically for Kenya and Tanzania government agencies to develop further agricultural strategies aimed at improving avocado farming within Taita Hills and Mount Kilimanjaro agro-ecosystems.Peer reviewe

Consumer Demand for Value-added Products of African Indigenous Vegetables in Coastal Kenya: The Case of Sun-dried and Frozen Cowpea Leaves

Some recent efforts to improve the food and nutrition security of rural households have focused on the promotion of African indigenous vegetables (AIVs). This has been due to the challenges smallholder farmers face in participating in high-value global food systems. AIVs contain vitamins and micronutrients not found in most exotic vegetables, and therefore their consumption could contribute to resolving malnutrition among poor rural households. Higher consumption could also lead to improved rural incomes through sales into urban niche markets, resulting in enhanced community development. Despite the role AIVs can play in promoting food security and community development, the AIV supply is highly seasonal, characterized by large gluts and acute shortages. Much study of AIVs has focused on production rather than consumption. In this study we use descriptive analysis to describe AIV consumers and assess demand for basic value-addition practices by AIV retailers. We then use regression analysis to examine the factors conditioning consumers' willingness to pay (WTP) for more advanced value-addition processes that can smooth out the supply of AIVs. It focuses on cowpea (Vigna unguiculata), one of the most widely consumed AIVs in western, eastern, and coastal Kenya. We find that several socio-economic factors and varietal attributes condition the WTP for value addition. Specifically, WTP is affected by age, gender, education, awareness of the selected value-addition techniques, and the self-reported likelihood of purchasing value-added vegetables. Additionally, color, tenderness of leaves, and the washing off of soil affect WTP for value addition. The paper discusses the implications of these findings for traditional fresh produce food systems, community development, and policy

Occurrence and Damage Levels of <i>Thaumatotibia leucotreta</i> on Capsicum in Selected Counties in Lower Eastern Kenya

The false codling moth (FCM), Thaumatotibia leucotreta (Meyrick), is believed to have originated from Ethiopia and sub-Saharan Africa. Currently, this pest has extensively spread and is found in most parts of Africa, with records in approximately 40 countries in over 100 host plant species. Despite Thaumatotibia leucotreta being the leading cause of interceptions of Capsicum and cut flowers exported by Kenya to the European Union, information on abundance and damage levels inflicted on capsicum is limited. The objective of the study was to assess the abundance and damage levels of T. leucotreta on capsicum in the selected counties in Lower Eastern Kenya (Kitui, Machakos, and Makueni counties). Higher T. leucotreta larval density per farm was recorded in Kitui County compared to other counties. In farms with capsicum only (not intercropped with other crops), the mean number of FCM larvae was relatively higher in Kitui. Farming practices such as the use of uncertified seeds and seedlings and the excessive use of pesticides may be the major contributors to high larval incidence in Kitui County