Spread of the spiraling white fly Aleurodicus dispersus (Homoptera: Aleyrodidae) and its parasitoids Encarcia species (Hymenoptera: Aphelinidae) on horticultural plants in Northwest and Central Nigeria

A survey was conducted in central and northwestern Nigeria to establish the extent of Aleurodicus dispersus Russel and Encarsia spp. spread on horticultural plants, especially citrus. The population dynamics of A. dispersus and the impact of Encarsia spp. were monitored on citrus for a period of two years in an orchard located in central Nigeria. Survey results indicated the spread of whitefly A. dispersus and its parasitoids in parts of central and northwestern Nigeria, notably in states sharing common boundary with the republic of Benin. Population of A. dispersus tended to depend on some factors such as vegetation zone and human activities in the surveyed area. In the monitored orchard, the population of Encarsia sp. nr haitiensis Dozier, the major parasitoid species, fluctuated with that of its host Aleurodicus dispersus especially during pick periods and had impact on the host over time

A Survey of the Insect Pests and Farmers' Practices in the Cropping of Tomato in Nigeria

A survey of some tomato producing areas of Nigeria indicated that the major insects attacking tomato included the fruit borer Helicoverpa armigera Hübner, the grasshopper Zonocerus variegatus L., the whitefly Bemisia tabacci Gennadius, and various species of aphids, mostly Aphis gossypii Glover. Interviews conducted to assess farmers' practices which contribute to insect damage showed that inappropriate application of insecticides and the use of wrong dosages may have contributed to insect control failures. Intercropping tomato with crops such as cereals tubers and other vegetables reduced infestation in some areas. However, most farmers' practices did not affect insect pest abundance. Insect populations and percentages of infestation were, in most cases, found to be significantly higher in Oyo state (in the rain forest agro-ecological zone) than in other surveyed states located in the savannah agro-ecological zones

A Survey of Rootstock Usage and their Influence on Major Insects and Diseases of Citrus in Nigeria

In the various agro-ecological zones of Nigeria, most farmers do not use the recommended rootstocks that enable the production of vigorous and pest/disease resistant plants. Consequently there are many reports of citrus stand losses and low fruit yields in pest and disease endemic areas. This necessitated the initiation of the present study with a view to appraise the validity of existing rootstocks and evaluate, where necessary, new ones adapted to the areas lacking appropriate ones. Questionnaires were administered to 84 citrus farmers in selected producing areas of Nigeria and field visits were made to sample for pests and disease incidence in their farms. The questionnaires covered citrus types and varieties cultivated, sources of planting materials and rootstocks used, pests and diseases causing damage. Results indicated that the citrus types cultivated were in the following decreasing order of preference: sweet oranges (100 % of the farms), mandarins (32 %), tangelo (30 %), grape (28 %), lemon, lime and shaddock altogether were cultivated in 20 % of the farms. Seedlings were either obtained locally or from agricultural agents. Somefarmers combine budded seedlings with seedlings from seeds to establish their orchards. Often, the rootstocks chosen for seedling production were not based on recommendations. Only 16 % of the farmers used the recommended rootstocks. Major insect pest and disease attacks that directly correlated with stand losses included those of termites, scale insects, aphids, Phytophthora and tristeza. The rootstocks used affected the severity of some pests and diseases when compared

Sustainable use of termite activity in agro-ecosystems with reference to earthworms. A review

International audienceAbstractSustainable agriculture and agro-ecology justify the need to study and understand the role played by ecological processes, and soil biodiversity in particular, in agro-ecosystem functioning. A large number of studies have focused on earthworms in temperate and humid tropical ecosystems and have demonstrated their importance for improving soil biological, physical, and chemical properties in agro-ecosystems. Their “success” is so essential that earthworms are widely considered key species and relevant indicators of soil health in temperate ecosystems. In arid and sub-arid ecosystems, the role of “soil engineer” is usually attributed to termites, and especially fungus-growing termites in Africa and Asia. However, despite this recognition, significant effort is spent eradicating them in plantations because of their pest status. In this review, we discuss the status of termites (“pests” vs. “soil engineers”) and question whether termites play similar roles to earthworms in arid- and sub-arid agroecosystems, with a focus on their influence on nutrient cycling and water dynamics. We argue that the dream of controlling natural interactions and ridding plantations of termites remains a costly legacy of the green revolution. We review the agricultural practices that have been used to reduce termite damage in plantations by restoring refuges to predators or by reorienting termite foraging activity towards organic amendments. Then, we show that the stimulation of termite activity can be used to improve key ecological functions in agro-ecosystems, such as increasing water availability to plants or producing fertility hot-spots. Finally, we suggest that more research on how termites can be used for improving ecosystem services, as is actually done with earthworms in temperate and humid tropical countries, could lead to a paradigm shift in our understanding of the impact of termites in tropical agro-ecosytems

Biological, environmental and socioeconomic threats to citrus lime production

Limes as a fruit crop are of great economic importance, key to Asian and South American cuisines and cultivated in nearlyall tropical and subtropical regions of the world. Demand for limes is increasing, driven by World Health Organizationrecommendations. Pests and pathogens have significantly reduced global productivity, while changes in agronomictechniques aim to alleviate this stress. We present here a holistic examination of the major biotic (pests and pathogens) andabiotic (environment and socioeconomic) factors that presently limit global production of lime. The major producers oflimes are India, China and Mexico, while loss of lime production in the United States from 2006 has led many countries inthe Western Hemisphere (Mexico, Costa Rica and Brazil) to export primarily to the USA. The most widespread inver-tebrate pests of lime areToxoptera citricidaandScirtothrips citri. Another insect,Diaphorina citri, vectors both Huan-glongbing (HLB) and Witches Broom of Lime, which are particularly destructive diseases. Developing agronomictechniques focus on production of resistant and pathogen-free planting materials and control of insect vectors. HLB infectscitrus in nearly all growing regions, and has been particularly devastating in Asian citrus. Meanwhile,Citrus tristeza virushas infected over 100 million citrus trees, mainly in the Americas and Mediterranean. Currently, Witches Broom Disease ofLime is localised to the Middle East, but recently it has been detected in South America. The range of its vectors (D. citriandHishimonus phycitis) further raises concerns about the potential spread of this disease. Abiotic threats to limeproduction are also a significant concern; key areas of lime production such as Mexico, India and the Middle East sufferfrom increasing water stress and high soil salinity, which combined with invasive pests and pathogens, may eliminate limeproduction in these areas. To ensure future security in lime production, policy makers, researchers and growers will need toexamine the potential of more resistant lime cultivars and establish novel areas of cultivation