A. van Huis

Toxicity and repellence of African plants traditionally used for the protection of stored cowpea against Callosobruchus maculatus

In a search for botanical products to control the main insect pest of stored cowpea, Callosobruchus maculatus, 33 traditionally used African plants were tested in the laboratory for their toxic and repellent effects against this beetle. Toxicity was evaluated measuring life history parameters in a no-choice situation. Powders of Nicotiana tabacum, Tephrosia vogelii and Securidaca longepedunculata significantly reduced the number of progeny. Repellence was evaluated by observing the behaviour of female beetles exposed to treated and untreated beans in a linear olfactometer. Clausena anisata, Dracaena arborea, T. vogelii, Momordica charantia and Blumea aurita were repellent to the beetle, whereas Chamaecrista nigricans, Azadirachta indica and Hyptis suaveolens were attractive. Our results indicate that botanical products may provide effective control of C. maculatus in cowpea.

Insects as Food in sub-Saharan Africa

Data on insects as food in sub-Saharan Africa were collected by reviewing the literature and conducting interviews in a number of African countries. A list of about 250 edible insect species from Africa was compiled. Of these, 78 percent are Lepidoptera (30%), Orthoptera (29%) and Coleoptera (19%), and 22 percent Isoptera, Homoptera, Hymenoptera, Heteroptera, Diptera and Odonota. Insects are rich in protein, vitamins and minerals, and a good source of iron and B-vitamins. Examples of insects being toxic are given, but often traditional methods are used to remove the poison. Whether or not insects are eaten depends not only on taste and nutritional value, but also on customs, ethnic preferences or prohibitions. The harvesting of insects is often done by women. The way of collecting depends on insects’ behaviour. For example, inactivity at low temperatures enables easy catching of locusts and grasshoppers in the morning. Night flyers (termites, some grasshoppers) can be lured into traps by light and some insects like palm weevils can be attracted to artificially created breeding sites. Some species (crickets, cicadas) can be located by the sound they make. A number of tools are used to facilitate capturing such as glue, sticks, nets and baskets. Because most insects are only seasonally available, preservation by drying is often practised. Some examples of how to prepare them as food are given from important insect groups.

Linking science and farmers' innovative capacity: diagnostic studies from Ghana and Benin

The article is an introduction to a series of articles about diagnostic studies carried out by eight PhD students in Ghana and Benin. These studies form a prelude to their experimental action research with groups of farmers to develop technologies that work in local conditions and are acceptable to farmers. A last article reports on a comparison of these eight studies by the ninth PhD student in the Convergence of Sciences (CoS) project. In this introductory article, it is argued that the need to ground agricultural research in the needs and circumstances of farmers is as strong as the need to ground research in the international scientific discourse. It explores the reasons why the West African context requires careful diagnostic studies to be able to design agricultural research that is of any use. It introduces preanalytical choice as an overriding concept to explain why choices that reduce the degrees of freedom have to be made explicitly on the basis of criteria. Such criteria are suggested for the quality of preanalytical choices, and the paper ends by examining the way the CoS project made some of its choices

Causes of low productivity of cocoa in Ghana: farmers' perspectives and insights from research and the socio-political establishment

Ghana is a major producer of cocoa in the world and relies heavily on the crop for foreign exchange revenue. However, production declined since the mid-1960s, reaching its lowest level in 1983. Although production has increased consistently since the mid-1980s, it still is less than the level attained in the mid-1960s. The decline is partly a result of decreasing areas under cultivation. Another problem in cocoa production in Ghana is low yields per ha, which is attributed to the incidence of pests and diseases, a low producer price, and non-adoption of research recommendations. Based on the idea that current research and extension messages might insufficiently address farmers’ actual problems and context, a diagnostic study was carried out to better understand farmers’ views on the problems of cocoa production. The study was conducted in three villages in the Suhum-Kraboa-Coalter District, Eastern Region, Ghana. An action research approach was followed to gather and analyse qualitative data with the objective of stimulating collective action in subsequent research activities with the farmers. Low productivity was identified as the main problem and the causes were classified into biological and socioeconomic factors. The biological factors include the incidence of pests and diseases, most of which have received extensive research attention in Ghana, and of epiphytes, which have been neglected. The socioeconomic causes were indirect and include the low producer price and the lack of amenities like electricity, which leads to migration, with as a result labour shortages and high labour costs. From the study it can be concluded that the biological and socio-economic causes of low productivity are inter-related in such a manner that tackling them separately will not overcome the problem unless the socio-technical nature of the causes are recognized and tackled in a holistic way. In this context, current interventions by research and extension seem to ignore important aspects of the problematic situation. Although the study shows the relevance of using a diagnostic approach, it is argued that outcomes may be affected by various contextual factors, including stakeholder selection and the relationship between the researcher and the participants. Hence, the outcomes of a diagnostic study should be approached with care.

Growth performance and feed conversion efficiency of three edible mealworm species (Coleoptera: Tenebrionidae) on diets composed of organic by-products

Insects receive increasing attention as an alternative protein-rich food source for humans. Producing edible insects on diets composed of organic by-products could increase sustainability. In addition, insect growth rate and body composition, and hence nutritional quality, can be altered by diet. Three edible mealworm species Tenebrio molitor L., Zophobas atratus Fab. and Alphitobius diaperinus Panzer were grown on diets composed of organic by-products originating from beer brewing, bread/cookie baking, potato processing and bioethanol production. Experimental diets differed with respect to protein and starch content. Larval growth and survival was monitored. Moreover, effects of dietary composition on feed conversion efficiency and mealworm crude protein and fatty acid profile were assessed. Diet affected mealworm development and feed conversion efficiency such that diets high in yeast-derived protein appear favourable, compared to diets used by commercial breeders, with respect to shortening larval development time, reducing mortality and increasing weight gain. Diet also affected the chemical composition of mealworms. Larval protein content was stable on diets that differed 2-3-fold in protein content, whereas dietary fat did have an effect on larval fat content and fatty acid profile. However, larval fatty acid profile did not necessarily follow the same trend as dietary fatty acid composition. Diets that allowed for fast larval growth and low mortality in this study led to a comparable or less favourable n6/n3 fatty acid ratio compared to control diets used by commercial breeders. In conclusion, the mealworm species used in this study can be grown successfully on diets composed of organic by-products. Diet composition did not influence larval protein content, but did alter larval fat composition to a certain extent.

Biological methods of bruchid control in the tropics: a review.

Bruchid beetles cause high losses of stored legumes in the tropics. Chemical control is inappropriate for the small scale farmer and the use of alternative measures should be encouraged. Different biological methods of control such as cultural, physical, varietal, biological, biorational and genetic control are reviewed. Cultural control techniques such as timely and frequent harvesting, legumes planted away from granaries, crop hygiene and storage in pods, are within the technical and financial means of the small scale farmer. The use of inert substances, vegetable oils and repellent plants may be cheap and effective if properly managed. The use of controlled atmosphere, vacuum, heating, cooling and sterilizing, requires relatively advanced techniques. Growth regulators and pheromones are currently not available for control. Varieties resistant to bruchids have been identified, but incorporation of resistance into suitable varieties has proven to be difficult. Biological control of bruchids should receive more attention in particular research on the introduction and conservation of natural enemies. To effectively implement control measures at farmer’s level socio-economic and cultural aspects should be taken into account. Proven appropriate techniques should be combined in an overall integrated pest management strategy.

Evidence of controlled corpus allatum activity in the adult Colorado potato beetle

Abstract The in vivo control of corpus allatum (CA) activity in females of Leptinotarsa decemlineata was investigated. Evidence was obtained that CA activity is adjusted by negative feedback when juvenile hormone (JH) titres are changed experimentally. Conclusions are based on determination of the rate of in vitro JH synthesis by the CA, on changes in CA volume, and on JH titres in the haemolymph. These assay methods are used alternatively in some of the experiments. After unilateral allatectomy, the remaining CA had doubled its activity 7 days later. On the other hand, the activity of CA in young adults was suppressed after the JH titre was elevated by the implantations of 2 CA taken from active females. Similarly, in beetles treated topically with exogenous JH the CA atrophied and showed a much reduced activity after 5 days. Denervation of CA in 0-day-old long-day and 7-day-old short-day females did not change CA activity when measured 1 day later.

Farmers' knowledge and perception of cotton pests and pest control practices in Benin: results of a diagnostic study

Cotton production constraints in Benin as perceived by farmers were studied from May to July 2003. The knowledge, perceptions and practices of farmers growing cotton under different pest management regimes were analysed. The methods used were open and semi-structured interviews with groups and individuals, as well as participatory exercises (brainstorming, prioritization, and problem analysis). Pest damage, low price of produce, late payment for seed cotton, and increasing input costs were the main production constraints perceived by producers. Regardless of the pest management system practised, most of the farmers adapt the recommendations of the research institute and nongovernment organizations to their livelihood systems. In general, farmers had a poor understanding of the key concepts underlying alternative pest control systems. Pest damage was considered important and farmers were eager to share their knowledge, perceptions and practices in pest management. The study provides the foundation for the creation of a learning platform; actors will be invited to collaborate in participatory experimental agricultural technology development linked to the farmers’ needs. In order to develop sustainable pest management strategies further interactive research is proposed, involving all stakeholders.

Efficacy of plant extracts against the cowpea beetle, Callosobruchus maculatus

Traditionally used African plant powders, with a known effect against the cowpea beetle Callosobruchus maculatus in stored cowpea, were extracted with water. The extracts, 13 volatile oils, 2 non-volatile oils and 8 slurries, were evaluated for their toxic and repellent effects against the beetle. Application of volatile oils led in most cases to a reduced number of eggs on treated beans. The volatile oils of Cymbopogon nardus and C. schoenanthus caused the majority of the eggs not to develop into adult beetles. Repellent effects were found for Clausena anisata, Cymbopogon citratus, Cymbopogon nardus, a mixture of Cymbopogon citratus and Cymbopogon flexuosus, Hyptis spicigera, Tagetes minuta and for two samples of Ocimum basilicum. Non-volatile oils were not repellent and had no effect on the number of eggs laid, but the development of these eggs was hampered, most so by Azadirachta indica oil. None of the slurries had a toxic effect on the beetles, but the slurries obtained from Carica papaya, Dracaena arborea and Tephrosia vogelii were repellent, whereas the slurry from Azadirachta indica leaves was attractive. Oils, both volatile and non-volatile, were easily extracted from plant material and showed promising results as a protective agent for stored cowpea.

‘Entomophagy’: an evolving terminology in need of review

There is growing interest in insects as human food in academia, food and agricultural industries, public institutions and the public at large. Yet many of the words and concepts used to describe these organisms and the human practices surrounding them are still rudimentary, compared to the diversity of the organisms themselves and the existing complexity and rapid evolution of the practices they aim to describe. The goals of this paper are to: (1) show how the roots of the term ‘entomophagy’ and its uses have evolved over time; (2) illustrate some of the term’s problems that necessitate its review; and (3) offer recommendations for use of the term in future research and other practice. Our paper offers a brief historical review of insect eating as described by certain Western cultural sources, explores some of the taxonomic ambiguities and challenges surrounding the category ‘insects’, and ultimately argues for more precise and contextual terminology in this both richly traditional and rapidly developing ...