Root bark extracts of five Meliaceae species (Turraea abyssinica Hochst., Turraea wakefeldii Oliv., Turraea mombassana Hiern ex C.DC., Trichilia roka (Forsk) Chiov. and Melia volkensii Guerke.) and different fractions thereof (following chloroform extraction and column chromatographic separation) were compared for their immediate toxicity and long-term effects on Anopheles gambiae Giles sensu stricto (Diptera: Culicidae). Larvicidal effects of the extracts appeared to be largely associated with limonoids of medium polarity with M. volkensii and T. mombassana extracts being more potent than those of the other Meliaceae. Long-term (6–8 days post-exposure) observations at lower doses showed that 100% cumulative mortality can be achieved with some extracts (particularly those of T. mombassana and M. volkensii) with interesting growth-inhibition effects. Follow-up studies that are needed and practical implications of the results in terms of development of larval control strategies for African malaria vectors are discussed.

The banana weevil, Cosmopolites sordidus (Germar), is a nocturnal insect that is not readily observed in banana fields. Knowledge on its distribution is essential for the design of management strategies that target the adult stage. Marked weevils were released into seven-year-old banana plots. Ten days later the plots were systematically sampled for adult weevils by first removing the banana leaf mulch and residues, searching subsections of the soil to depths of 3 and 25 cm and, finally, removal and dissection of the banana mats. Of the marked weevils, 62, 56 and 82% respectively, were recovered in three trials. Most weevils were found in close association with either the banana mat (46–66%) or with cut residues lying on the ground between the mats (24–31%). Lesser numbers were found in the leaf mulch and in the top 3 cm of soil away from the mat. The distribution of weevils is likely to be influenced by crop management practices and the availability of residues and by the presence of mulch. Implications for banana weevil IPM are discussed.

The leaf miner Coelaenomenodera lameensis Berti & Mariau (Coleoptera: Chrysomelidae: Hispinae) is the most serious pest of oil palm in West Africa. A study of mortality factors was carried out at 19 sites located in seven plantations of 3000–7000 ha, over a 2–4-year period in the early 1980s throughout the forest zone of Côte d'Ivoire, West Africa. All life history stages of C. lameensis were found to be attacked by natural enemies. Fluctuations in numbers of egg parasitoids were related to climatic factors and host population dynamics and parasitism rates varied substantially among sites. High egg mortality in C. lameensis, related to parasitism, was directly linked to climatic factors, mainly relative humidity. Fluctuations in egg mortality not linked to parasitism were similar among plantations. There was also a negative correlation between beetle fecundity and egg mortality; climatic conditions favourable to an increase in fecundity also disfavoured egg mortality. This can be a major cause of population increase of larval C. lameensis. Different species of larval and pupal parasitoids and predators were observed. In addition, viruses, isolated from dead larvae in galleries, killed 55–60% of the larvae, probably playing an important role in limiting populations. The destruction of mines by several species of ants also eliminated about 25% of beetle larvae. Parasitoids played a smaller role (less than 10% of larval mortality is due to parasitoids). Mortality in larvae and pupae can exceed 90%, but varied widely from one plantation to another. Examples of mortality tables are given for clearly characterized situations and they help to explain the stability of populations and the occurrence of outbreaks on a plantation or sites scale. Mortality rates lower than 98.6% can lead to population instability and an outbreak in an area.

Pollination in the genus Ceropegia L. (Apocynaceae: Asclepiadoideae–Ceropegieae) in East Africa is discussed based on field observations and herbarium studies. All inferred or confirmed pollinators are small, mostly female dipteran flies, c. 2.5mm long, which carry pollinaria on their proboscis. Identified putative pollinator flies belong to families Milichiidae, Chloropidae and Ceratopogonidae. The most important factors for an insect to effect pollination appear to be the appropriate overall size, i.e. small size of c. 3×;3mm at most, and appropriate mouth parts, i.e. extendible probosces with suitable surfaces and adjacent pads on which a pollinarium can attach. The complex and diverse floral morphology of the tubular flowers and their disposition as well as other commonly occurring features namely, diverse interior and exterior coloration, diverse scents, secretions such as nectar and water droplets, vibratile corolla lobes and hairs, specialized hairs, interior sculpturing, sliding zones and differential lighting within the flower are important mechanisms for attracting and detaining insect pollinators.

Pollination ecology was investigated in Citrullus lanatus (Thunb.) Matsum. & Nakai, which is a species vulnerable to pollinator loss. It was found that this species depends heavily on the honeybee, Apis mellifera L., as the main pollinator. Other pollen vectors identified include Xylocopa bees, halictid bees, Hypotrigona bees, flies and beetles. Phenologically, the plant was found to promote male fitness by producing numerous male flowers, which serve as pollinator attracting structures. Blooming sequence and A. mellifera visitation rates to these flowers are presented. This will enable farmers and pollination managers to better understand visitation patterns and to safeguard pollinators during pesticide application schedules.

Glasshouse studies were conducted to determine mechanisms of resistance of five genotypes of lentil Lens culinaris (Medikus) previously identified as resistant and moderately resistant to the pea aphid Acyrthosiphon pisum (Harris). A susceptible standard, ILL 8127, was also included. French Indigo had high levels of antibiosis, demonstrated by reduced reproductive period, fecundity and longevity, while Spanish Brown had high levels of antixenotic and tolerance components of resistance. Based on overall resistance, French Indigo was the most resistant genotype followed by Spanish Brown. These genotypes could be a source for resistance to A. pisum. All five genotypes had varying levels of antibiosis, antixenosis and tolerance components of resistance compared with ILL 8127.

A study was carried out for four years in the forest area of Daloa in Côte d'Ivoire to assess the rate of trypanosome infection in tsetse, and thereby the trypanosomiasis infection risk. In different Glossina biotopes, 18,908 Glossina palpalis palpalis were caught with Vavoua traps and were dissected. The most widespread species of trypanosomes infecting the Glossina was Trypanosoma congolense (7.63%) followed by T. vivax (4.50%). Trypanosoma brucei, the trypanosome responsible for animal and human African trypanosomiasis (HAT), was found only in 34 of the tsetse flies collected, and it had a very low infection rate (0.18%). Although infected tsetse flies were captured in all habitats examined, the infection rate was relatively higher along footpaths (0.44%), in farms (0.20%) and around forested water springs (0.27%) compared to the edge of villages (0.06%) and forest borders (0.05%). Among the 34 tsetse flies infected with T. brucei, only 0.05% had parasites exclusively in their salivary glands. Our results suggest that footpaths, plantations of coffee and cocoa and forested water springs are potential biotopes where the risk of infection by T. brucei is most important. The anthropophily of Glossina associated with the high number of parasites in these sites could be the reason for the disease is endemic in Daloa today. In our study, female Glossina were infected more frequently with trypanosomes (0.14%) than males (0.04%) and generally, females lived longer than males. It is likely that the longevity of females, which carry parasites, is the major cause for the endemicity of HAT in this locality.

To investigate the existence of inter-strain fecundity in the groundnut beetle Careydon serratus, the fecundity and larval survival of crosses of beetle strains from Bauhinia, Cassia, Piliostigma and Tamarindus were studied. The crosses produced viable eggs, but the fertility of beetles mated within strains was significantly higher than that of inter-strain matings, the former being nearly double the latter. Differences in larval mortality between the various crosses were also observed.

The study reported examined mechanisms of pollen transfer within the genus Lagenaria, including insect vectors in the natural and cropped field environment. The major flower visitors to Lagenaria were observed for 10 months, from June 2001 to April 2002 at five sites, namely the Botanic Garden of the National Museums of Kenya, three farmers' crop fields in Dungicha village in Kilifi District, Katitika and Wayowani villages in Kitui District and the home garden of one of the authors, in Westlands, Nairobi, Kenya. Twenty-two species of insects represented in four orders belonging to 10 families were found to be the major visitors of L. siceraria flowers. From the foraging patterns of the flower visitors, visiting frequencies and development of fruits, four groups of flower visitors comprising hawkmoths (Hippotion celerio, Agrius convolvuli), moths A–D (Noctuidae spp.), skipper butterfly (Gorgyra johnstoni) and honeybee (Apis mellifera) were considered active flower visitors. Hawkmoths were suspected to be the major pollinators of this plant in the locations surveyed.

Anthesizing male inflorescences of oil palms were randomly sampled for the oil palm-pollinating weevil Elaeidobius kamerunicus at the Nigerian Institute for Oil Palm Research (NIFOR) (field 56) in Benin City, Nigeria from March to September 2002. The weevils were counted and later examined for nematodes. There were no significant differences in the mean number of adult weevils sampled from various positions on the inflorescences, but there were significant differences in their mean numbers sampled on the various dates (P=0.001). Microscopic examination of adult weevils indicated that nematodes are associated with the weevils and the spikelets. This preliminary survey indicates that E. kamerunicus is a major insect pollinator of the oil palm in NIFOR oil palm plantations. Its association with parasitic nematodes may have a bearing on the weevil's pollination efficiency. These findings will help in understanding further the factors that govern pollination efficiency, percent fruit set and the occurrence of seasonal peaks in yields of fresh fruit from Nigerian oil palms.

Bionomics, morphometric measurements and partial mitochondrial cytochrome oxidase I gene (mtCOI) sequences were examined for a population of Bemisia afer (Priesner & Hosny) (Hemiptera: Aleyrodidae) collected from cassava in Uganda. The development of the eggs, first to fourth instar nymphs and adults required respectively, 12, 31 and 10 days, with a total life duration of approximately 53 days on the cassava cultivar Ebwanateraka. Each female laid one egg per day for 13 days and about 40% of the eggs failed to develop into adults. The male: female sex ratio was 1:4. The length and width of the four nymphal instars were positively correlated (correlation coefficient=0.97). Females were bigger than males and the sexes differed significantly based on body length (P<0.001) and width (P<0.001). Overlaps in their body sizes, however, makes sex assignment based on size alone unreliable. The B. afer population shared 68% mtCOI sequence (817 nucleotides) identity with a cassava Bemisia tabaci population (Namulonge) from Uganda. This is the first study on B. afer fecundity and morphometrics, and the variability that might exist in this species is discussed.

The African rice gall midge Orseolia oryzivora is a major pest of rice in Burkina Faso. The present study was carried out during four consecutive crop seasons from 1999 to 2001, in three rice-irrigated schemes, near Bobo Dioulasso town in south Burkina Faso. The fluctuation of immature stages of the pest and their damage, with regard to host plants was monitored. These included the cultivated rice Oryza sativa and its ratoons, and wild rice Oryza longistaminata. Sampling on growing rice was carried out monthly in 1m2 quadrats, in each of 100 randomly selected farmers fields. Sampling on rice ratoons was carried out after rice harvest and 500 tillers were randomly selected in the same fields and taken to the laboratory for dissection. Data on wild rice were collected every month by sampling and dissecting 500 tillers per site. This study revealed that in the absence of rice, the pest survived on rice ratoons and wild rice. However, cultivated rice was the preferred host plant as the crop recorded over 15% galling during wet seasons while damage was very low in dry seasons. Results from this study represent an important step towards the development of an IPM programme to control the rice gall midge, with regard to its host plant relationships.

On the island of Madagascar and five neighbouring islands: Aldabra, the Comoros, Mauritius, Réunion and the Seychelles, the number of hitherto found Ptyctima species is 57, including 37 Phthiracaroidea (of which ten are new to science), 18 Euphthiracaroidea (one new to science) and two Mesoplophoroidea. Of those 57 species, 30 are endemic (53%), ten Ethiopian species (17%), 12 pantropical species (21%) three oriental (5%) and two semicosmopolitan (3%). Endemism of Phthiracaroidea (62%) is similar to Euphthiracaroidea (59%). Similarity between the ptyctimous fauna of Madagascar and the neighbouring islands is very small—only one or two species are common. Moreover, the fauna of Mauritius is completely different from that of Madagascar. The ptyctimous fauna of Madagascar and the near islands must have been shaped before separation of Madagascar from Africa, which is suggested by the presence of the phylogenetically oldest and the youngest genera of Phthiracaroidea and Euphthiracaroidea. On the other hand, a large number of species of late derived genera Notophthiracarus and Hoplophorella may indicate a relatively late colonization of the islands by Phthiracaroidea. Dispersion of Ptyctima onto Madagascar and the neighbouring islands took place from the east—the Oriental region or from the south—the Australian region.

Powders from dry leaves of four plant species: Ficus carica (Moraceae), Eucalyptus globulus (Myrtaceae), Olea europaea (Oleacea) and Citrus limon (Rutaceae), were evaluated under controlled conditions (30±1°C and 70±5% RH), for their biological activity against Callosobruchus maculatus (Coleoptera: Bruchidae), and were compared to a powder from cloves of myrtle Syzygium aromaticum (Myrtaceae) and to eugenol (the essential oil from cloves). Once mixed with seeds of chickpea Cicer arietinum at doses of 1 to 5% (w/w), all the five powders significantly reduced adult longevity. Among these tested botanicals, clove powder was the most toxic as adult survival in treated seeds was less than 24h, even at the lowest dosage of 1%. The powders from dry leaves also reduced fecundity while that from cloves completely inhibited oviposition in C. maculatus. Indeed, the mean number of eggs laid in chickpea seeds treated with powders from dry leaves of the four plant species above varied from 273.2±30.3 to 373.8±58.2 against 401.8±37.9 in the control (untreated seeds). At the highest dose of 5%, all powders significantly reduced the number of emerging adults: 149.3±46.7 in treatment with O. europaea, 139.8±25.1 with E. globulus, 82.8±48.1 with C. limon, 31.5±20.5 in treatment with F. carica and 0.0±0.0 with S. aromaticum. Tests with lower doses (0,1–0,5%) of clove powder revealed that from the dose of 0.2% and above, C. maculatus adults died before laying eggs. Treatments with eugenol at 5μl/50g seeds (v/w), significantly reduced adult longevity (1±0.0 day), the number of eggs laid (0.0±0.0 egg) and adult emergence rate (0.0±0.0 adult), compared to the control used in this test where these parameters are respectively 7.00±0.8 days, 1134.4±204.2 eggs and 745.6±144.9 adults of the first generation.

Laboratory studies were carried out to investigate the role of larval habitat-derived microorganisms in the production of semiochemicals for oviposition site selection by Anopheles gambiae Giles sensu stricto mosquitoes. Dual-choice bioassays with gravid females were conducted in standard mosquito cages. Field-collected or laboratory-reared mosquitoes, individually or in groups, were offered a choice between unmodified (water or soil from a natural breeding site) or modified substrates (filtered water, autoclaved soil or sterile media to which bacterial suspensions had been added). Egg counts were used to assess oviposition preferences. Mosquitoes preferred to oviposit on unmodified substrates from natural larval habitats containing live microorganisms rather than on sterilized ones. Variable responses were observed when sterile substrates were inoculated with bacteria isolated from water and soil from natural habitats. We conclude that microbial populations in breeding sites produce volatiles that serve as semiochemicals for gravid An. gambiae. These signals, in conjunction with other (non-olfactory) chemical and physical cues, may be used by the female to assess the suitability of potential larval habitats in order to maximize the fitness of her offspring.

Honeybees are of critical importance in Africa for both ecological and economic reasons. Their contribution to floral biodiversity and conservation, by virtue of their pollination of indigenous flowering plants is unknown, but certain to be considerable. Economically, honeybees are critical for the pollination of a host of commercial crop plants as well as being the source of energy and livelihood for many thousands of mostly small-scale beekeepers. In the past, honeybee pests and problems have been of limited importance in Africa. More recently, however, an increasing number of exotic diseases and pests as well as home-grown problems threaten honeybees, beekeeping and honeybee-pollination in Africa. Two problems in South Africa, the capensis problem and varroa mites, have severely curtailed beekeeping in that country and may well have impact on bees and beekeeping throughout the continent.

The effect of diet on the biology of the predatory mite Amblyseius denmarki Zaher & El-Borolosy (Acari: Phytoseiidae) was studied in the laboratory. Predatory mites fed on the eriophyid mites eriophyes dioscoridis, E. olivi and Cisaberoptus kenyae had a faster development, higher fecundity and a more female-biased sex ratio than those fed on the other diets tested, namely pollen of the palm Phoenix dactylifera, the scale insect Parlatoria ziziphus and the whitefly Bemisia tabaci.

In studies aimed at optimizing the substrate for rearing Helicoverpa armigera (Hübner) under laboratory conditions, the noctuid's oviposition behaviour was studied in the laboratory using pigeonpea leaves, muslin cloth, tissue paper and cotton wool as oviposition substrates in free-choice and no-choice tests. Egg counts revealed the moth's preference for oviposition substrate, in descending order, to be cotton wool, pigeonpea leaves, tissue paper and muslin cloth. The preference index of cotton wool was 65% higher than the least preferred substrate, muslin cloth. A total of 300 eggs per female were laid in the free-choice tests, while 200 were laid in the no-choice assays.

A modified technique to extract intact DNA from Aedes aegypti and Anopheles darlingi mosquitoes is presented. The samples were treated initially with proteinase K to digest all proteinaceous matter. For both vectors, the optimum temperature for the protease treatment was 55°C and the best pre-incubation time was 4 h. RNA contamination was eliminated with RNAse treatment. The purity of the DNA was high since the A260/A280 ratio averaged >1.80 for all samples and the quantity of DNA extracted was >1.6 times higher than that using the unmodified procedure. The DNA obtained displayed clear random amplified polymorphic DNA (RAPD) profiles, which indicates that it can be used for polymerase chain reaction (PCR)-based techniques.

A study was conducted to investigate whether a lack of pollinators, pollination and therefore, a shortage of fruit set of perennial plants is more likely to occur in overgrazed land than farmland without grazing pressure, as this could have considerable effects on the reproduction of certain plant species. The study was conducted at two adjacent BIOTA biodiversity observatories (<url>www.biota-africa.org</url>) in Namaqualand, South Africa. Individuals of certain plant species of the family of Aizoaceae were measured and flower and fruit production recorded. Malaise traps and transect walks were used to document insect diversity. Preliminary results indicate that not all plant species show reduced flower production but that fruit set is indeed compromised on overgrazed land. Insect diversity and abundance is partially reduced under heavy grazing pressure, especially in locations where the vegetation cover is low and dominated by unpalatable plant species.