For the last three years, CIRAD (Centre de Coopération Internationale en Recherche Agronomique pour le Développement, France) and the University of Pretoria led field research to evaluate the impact of transgenic Bt cotton, expressing the Cry1Ac toxin, on arthropod biodiversity in South Africa. The diversity and the density of insect populations were estimated at different crop development stages using traps, sweep-nets, and direct observations on the cotton plants. In untreated plots, the insect diversity in Bt cotton did not show major changes. The toxin was efficient in controlling one of the major bollworm species, Helicoverpa armigera (Hübner), and reduced the population density of specific larval parasitoids. Predators were present in comparable numbers in both cotton types, except for ladybirds. The toxin did not affect pollinators. In small-scale farming fields, where pesticides are still sprayed for controlling sucking insects, the introduction of Bt cotton did not help meet the expected reduction in insecticide use.

Studies conducted from 1969 to 2000 on termite ecology and biology in Senegal revealed high termite diversity and an influence of climate and soil conditions on termite group distribution. Sixty-four termite species were recorded. Some were specific to ecologically similar zones while others were widely distributed. Some species, known to inhabit wet zones, were found in semi-arid zones where relic forest vegetation still exists. Nioro, in the central part of the country, seems to be the buffer zone between species to the north and south of Senegal. In Ferlo, an arid zone, Macrotermes species was in regression and the subsisting colonies tended to establish in lowlands with a long humidity period and high vegetation density. The study also focused on termite damage in different agroecosystems. Odontotermes, Microtermes and Psammotermes spp. were the main pests on annual crops and vegetables. Microtermes, Amitermes and Microcerotermes spp. were found attacking young trees, thus affecting reforestation programmes in Senegal.

Life table studies of Earias vittella (Fabricius) on different hosts in the Insect Biotech Laboratory, Department of Entomology, Dr PDKV Akola, revealed that survival (lx) of immature stages of E. vittella on different hosts was 0.65 on okra, 0.56 on cotton, 0.54 on semi-synthetic diet and 0.51 on mesta. The net reproductive rate (Ro), at the end of each generation, of E. vittella was 81.91 on okra, 56.70 on cotton, 53.02 on semi-synthetic diet and 36.63 on mesta (Hibiscus cannabinus L.). The net reproductive rate (Ro) followed the same order as the survival rate (lx) on the different hosts. The innate capacity for increase in numbers (rm) ranged between 0.0888 and 0.1334 females/female/day. In descending order, the rm values on different hosts were okra (0.1334), cotton (0.1111), semi-synthetic diet (0.1029) and mesta (0.0888).

Computer programming is ideal for the identification of ticks. This is due to the ability of computers to make rapid, repeated and complete searches of a large database of features in answer to a series of questions which lead to a single species. The program can allow the search to start in any order and to avoid difficult questions. It enables illustrations to be displayed when a question is asked. In contrast, classical dichotomous keys need to be used in a fixed sequence in which it is difficult to avoid questions, and often use vaguely defined characters and obscure language. To program an electronic key a character state matrix is constructed of rows of precisely defined characters with the two or more states in which they may occur and of columns in which the species are placed. Each state is recorded as being positive or negative. This corresponds to the binary system needed for computing and this need enforces a discipline on the identification method that has to define in illustrations and precise standardized language the characters and their states. These concepts are illustrated by the development of ‘Multikey’ program for the identification of ticks of domestic animals in Africa. The advantages of Multikey are its ease of use, its compatibility with comprehensive tick guides on compact discs and the ability to expand it with more information. The disadvantages are the requirement for a computer next to the laboratory microscope and the difficulty in browsing the contents. These disadvantages can be overcome by a printed version and there is use for both the printed and the electronic versions of such guides.

Southern Sudan has tremendous agricultural potential, particularly in the high rainfall green belt of western Equatoria that borders the Democratic Republic of the Congo. A wide range of tropical and semi-tropical crops is grown there in a variety of complex cropping systems. Although a long civil war severely disrupted agriculture in the region, there is now hope that the recent peace accord will return stability and agriculture will remain a mainstay of a revived economy in western Equatoria. The environment supports crop production, but pests and diseases also thrive, although very little has been recorded about them. This article represents the sole record of an agricultural insect pest collection and disease notes assembled at Yei over several years in the early 1980s, but which were destroyed during the civil war. It is hoped that these notes will be useful in addressing biotic constraints to rehabilitation of agriculture in western Equatoria. Traditional methods of pest and disease management will be particularly important given the poor state of the economy, the need to produce crops for subsistence farming and the relative geographical isolation and poor communications that characterize southern Sudan. Le sud du Soudan offre d'énormes potentialités de développement agricole, en particulier dans la ceinture verte humide de la région Ouest de l'Equateur qui borde la République Démocratique du Congo. Une large gamme de cultures tropicales et subtropicales y est cultivée selon une grande variété de systèmes culturaux complexes. Bien qu'une longue guerre civile ait sévèrement perturbé l'agriculture de la région, il y a maintenant un espoir que les accords de paix récemment signés rétablissent la stabilité et que l'agriculture puisse constituer la base d'un renouveau économique dans l'Ouest de l'Equateur. L'environnement est favorable á la production agricole, mais également au développement des ravageurs et des maladies, bien que nous ayons très peu d'informations. Cet article constitue une source unique d'informations sur les insectes ravageurs et les maladies des cultures répertoriées pendant plusieurs années au début des années 80 dans la région de Yei, mais dont les notes ont été détruites pendant la guerre civile. On espère que ces notes seront utiles pour identifier les contraintes biotiques et permettre la réhabilitation de l'agriculture dans l'Ouest de l'Equateur. Les méthodes traditionnelles de gestion des ravageurs et des maladies seront particulièrement importantes compte tenu du mauvais état de l'économie, du besoin de produire des cultures de subsistance, du relatif isolement géographique et des mauvaises communications qui caractérisent le sud du Soudan.

Genetic and biological implications from interbreeding the Ghanaian okra and cassava biotypes of Bemisia tabaci (Gennadius), reared on eggplant, were studied in reciprocal crossing plans and crosses compared with parental generations using RAPD–PCR. Interbreeding did not affect fecundity of mated females and survival of F1 progeny. However, the sex ratio of the hybrid progeny was significantly male dominated (by 70% males) compared to purebred progeny of each biotype (>60% females) (P<0.01). Each biotype was characterized by its own RAPD profiles. Hybrid females had one locus identical to that of both parents, while the males resembled the mother biotype at two loci. The F1 females were oviposited normally and there was a possible restricted gene flow between insects from the two biotypes, sharing the same host plant. However, the biological isolation seems to buttress ecological isolation in nature, hence maintaining the genetic and biological identity of sympatric populations in both biotypes.

The sweet potato whitefly Bemisia tabaci (Gennadius) is a pest of diverse agricultural systems worldwide, owing to its capacity to transmit viruses, both intraspecific and host-associated variations. In Ghana, it is the only known arthropod vector for cassava-infecting begomoviruses (Geminiviridae). Two genetic variants of B. tabaci, previously characterized by RAPD–PCR and subsequently reared on cassava and okra, were allowed access to five weed species in order to examine host preference and suitability: Amaranthus retroflexus, Chromolaena odorata, Desmodium tortuosum, Euphorbia heterophylla and Malvastrum coromandelianum. Overall, the duration of the life cycle ranged between 16.5 and 26.3 days and survival rates were 0–27.5%. The population from field-infested okra reproduced and developed to maturity on C. odorata, D. tortuosum and E. heterophylla. Both populations produced male and female progeny. Amaranthus retroflexus and M. coromandelianum were considered poor hosts for both populations, due to the low fecundity and survival of eggs, pupae and adults. The rearing host did not significantly (P>0.05) influence survival on subsequent hosts in either case. The host-restriction of the population collected from cassava was not corroborated here, based on the demonstrated ability of the Ghanaian cassava population to complete its life cycle on D. tortuosum and E. heterophylla. It was estimated that B. tabaci could achieve 13–22 generations per year in Ghana. Removal of C. odorata, D. tortuosum and E. heterophylla from the vicinity of susceptible crops is recommended.

Lentil seeds infested with Callosobruchus chinensis (Linnaeus) for 12–15 days were exposed to Dinarmus basalis (Rondani) alone, Anisopteromalus calandrae (Howard) alone, or to both species, at densities of 2, 4, 8, 16 and 32 insects. Intra-specific competition and host emergence decreased with increasing parasitoid density in both D. basalis and A. calandrae, but progeny production of the parasitoids and parasitoid-induced mortality (PIM) increased with increasing parasitoid density. Dinarmus basalis was much more efficient in parasitizing C. chinensis than A. calandrae. Emergence of D. basalis and A. calandrae, and the PIM were highest at a parasitoid density of 32. Parasitoid density and a combination of parasitoids significantly (P<0.01) affected the number and progeny sex ratio of emerged parasitoids. There were significant (P<0.01) effects of inter- and intra-specific competition on host mortality. Host mortality increased with increasing parasitoid density. Parasitoid combination and parasitoid density also significantly affected PIM.

Three species of fruit fly parasitoids, Psyttalia concolor (Szépligeti), Psyttalia cosyrae (Wilkinson) and Psyttalia lounsburyi (Silvestri) (Hymenoptera: Braconidae) were reared on different host larvae to determine the effects of host species, size and colour on parasitoid development. Ovipositor, ovipositor sheath and hind tibia lengths were found to be different for progenies from preferred and non-preferred host larvae. Ratios of ovipositor–tibia and ovipositor sheath–tibia showed no difference when P. concolor was reared on a bigger host (Ceratitis cosyra) (Walker) (Diptera: Tephritidae), whereas rearing P. cosyrae on a smaller host (C. capitata) (Wiedemann) showed significant differences. Comparison of the linear measurements, ratios and number of flagellomeres of parasitoids reared on preferred hosts, separated the species into their natural groupings. When reared on a different-coloured host, P. lounsburyi lost its dark markings but other characters remained unchanged. Morphometric analysis also indicated differences between parasitoids reared on preferred host larvae and those reared on non-preferred host larvae. Rearing parasitoids on larvae other than their preferred hosts resulted in colour and size changes, and thus, these characters alone were not reliable for the identification of parasitoids. This is especially important in post-release sampling surveys to ascertain establishment of the parasitoids in new environments where they may adapt to new host species.

Aspidiotus destructor Signoret (coconut scale) occurs on bananas in Hawaii, infesting leaves and fruit. Seasonal population fluctuations on two banana varieties and a preliminary sampling plan for management decision making are described. There were distinct seasonal variations in A. destructor numbers on bananas in Hawaii and varietal differences in population densities and proportions of plants infested, with cv. Cavendish incurring highest A. destructor populations. An aggregated dispersion was found for A. destructor. A preliminary sequential sampling plan based on a nominal threshold is provided.

The parasitic wasp Anisopteromalus calandrae (Howard) was released at six (5, 10, 20, 30, 40 and 50 pairs) densities to evaluate the effects of different introduction rates in controlling residual populations of the lesser grain borer Rhyzopertha dominica (Fabricius) in wheat grain stored in bulk in 46 m2 rooms. At the 50-pair density, the parasitoid suppressed 83% of R. dominica in June–July and 74% in August–September. At the 5-pair density, the numbers of F1 progeny per female were 44 and 51, during the first and second period, respectively while at the 50-pair release rate, only 6 and 7 individuals were recorded, respectively. In a second test, the effects of different materials used for storing were evaluated on both insects. Five hundred (500) grain-residing 20–22-day-old R. dominica larvae were mixed with 250g fresh wheat stored separately in each of five types of bags, i.e. jute, calico (Americana cloth), polypropylene, polythene, nylon, then exposed to 50 pairs of A. calandrae. The parasitoid suppressed host populations in all types of bags, except in those made of polythene. The highest percentage (69 and 81%) suppression occurred in calico bags during the June–July and August–September periods, respectively. The lowest suppression of 51 and 57% was observed for polypropylene bags during the respective periods. The parasitoid-induced mortality was positively correlated with the parasitoid density.

The effects on the reproductive responses and the offspring fitness in monogamous and promiscuous females of the seven-spotted ladybird Coccinella septempunctata Linnaeus were studied. Reproductive responses were higher in monogamous and promiscuous females with unlimited mating than those subjected to limited mating. Monogamous females with unlimited mating recorded longer oviposition period and higher fecundity than those subjected to limited mating. Promiscuous females with multiple mating recorded the longest oviposition period, the highest fecundity and percentage egg viability (short-term benefits), and the shortest developmental period, maximum larval survival and adult emergence (long-term benefits).

Studies were conducted at Mtwapa, in the coastal area of Kenya, during the long and short rains of 1999 and 2000 to evaluate interaction of mortality factors in lowering Chilo partellus (Swinhoe) populations in diverse agroecosystems. Treatments consisted of hedgerows of leucaena only, gliricidia only, alternating rows of leucaena and gliricidia, and three plots without trees. During the cropping seasons, maize was planted between the hedgerows while a row of cowpea was planted between the rows of maize. One of the plots without trees was planted to an intercrop of maize and cowpea. The remaining two plots without trees were planted to maize alone, one of which was mulched. The treatments were laid out in a randomized complete block design with four replications. There was no evidence of enhanced mortality in the more diverse systems indicating that the vegetation structure and cultural treatments studied did not enhance activity levels of C. partellus mortality factors. The highest mortality occurred in the early and medium larval stages in all treatments. This mortality was attributable to ‘disappearance’, which represented mortality from sources other than parasitism. The total real generation mortality showed that from the initial cohort of first and second instar larvae, less than 10% of C. partellus survived to adult stage under field conditions in all the treatments. Mortality by Cotesia sesamiae Cameron and Cotesia flavipes (Cameron) was very minimal, indicating the parasitoids were not important mortality factors of C. partellus under the cropping systems studied. Their effects were also not influenced by the cropping systems studied.

In order to predict host accessibility by the pupal parasitoid Xanthopimpla stemmator (Thunberg), four grass species (Sorghum bicolor, Pennisetum purpureum, Sorghum arundinaceum and Zea mays) were sampled for stemborer pupae in Kwale, in the low altitudes of southern Kenya, and in Trans-Nzoia, in the high altitudes of western Kenya. The pupal position of Chilo orichalcociliellus (Strand), Chilo partellus (Swinhoe), Sesamia calamistis Hampson, Sesamia sp. nr oriaula (Tams and Bowden) and Busseola fusca (Fuller) in the plant were determined in relation to (a) the distance of pupae from the edge of the stem (depth), (b) the distance between the moth-exit hole and the head of the pupa (location) and (c) the length of the tunnel from the moth-exit hole to the base of the tunnel. Pupal depth and location for C. partellus and B. fusca varied significantly in the different plant species tested, and the pupae tended to be embedded deeper in cultivated than wild hosts. On all host species, the borers were located at a depth less than 0.35 cm. Most C. orichalcociliellus and S. calamistis pupae were found pupating in the ears of maize or the upper part of the wild hosts' stem. Sesamia sp. nr oriaula was only collected from the lower parts of P. purpureum. For B. fusca, tunnel length varied significantly among plant species and was longer in cultivated hosts. Xanthopimpla stemmator has an ovipositor length of about 0.52 cm, thus it is anticipated that the parasitoid could easily reach and parasitize the pupae in these host species.

Field experiments on reduced application doses of Metarhizium anisopliae var. acridum (I 91 609: Zonocerus variegatus strain) were carried out in 1996–1997 in southeastern Benin and central Ghana. The first experiment, which took place in southeastern Benin, consisted of ULV applications of an oil based formulation of M. anisopliae on 1-ha plots of cassava, at the rates of 1 × 1011, 4.65 × 1011 2.5 × 1012 and 1 × 1013 conidia/ha. In a second experiment carried out in central Ghana, the application doses were reduced by increasing the space between spray tracks. Treatments were applied at 5, 10 and 20m track spaces, corresponding to doses of 2.5 × 1012, 1.25 × 1012 and 0.625 × 1012 conidia/ha, respectively. After application, samples of L4–L6 larvae and adults of Z. variegatus were collected using sweep nets and their mortality monitored in small cages. Zonocerus variegatus population density was monitored at three-day intervals over a 21-day period. In southeastern Benin, analysis of survival time, resulting from the first sampling, did not reveal any significant difference between the various dose treatments. In central Ghana, for treatments at different doses and track spaces, there was no difference between 5 and 10m track spaces, corresponding to 2.5 × 1012 and 1.25 × 1012 conidia/ha. But the 1.25 × 1012 conidia/ha treatment at 10 m-track space reduced the application time by half (17 min instead of 34 min).

The effect of covering post-harvest banana stumps with soil on banana weevil Cosmopolites sordidus (Germar) oviposition levels was investigated at three locations, Sendusu, Kawanda Agricultural Research Institute (KARI) and Ntungamo district of southwestern Uganda. In the first experiment oviposition levels were assessed in a banana system comprising growing plants and residues. Oviposition increased on sword suckers, reaching a peak 1–7 days after harvest and decreased thereafter. In the second experiment conducted on farmers' fields, corms received 70% of the eggs and pseudostems 30%. The area 5–10 cm below the collar received 27% of the eggs, the area 0–5 cm above the collar 30% and the area 5–10 cm above the collar 0.3%. The remaining eggs (43%) were laid 0–5 cm below the collar. The effect of stump height and covering the stumps was evaluated in both the wet and the dry seasons at Kawanda and Ntungamo. Cutting stumps to the ground level alone had no effect on oviposition. Covering post-harvest banana stumps reduced C. sordidus oviposition in the wet but not in the dry season.

Little is known about phase polymorphism in the red locust, Nomadacris septemfasciata (Serville) in Madagascar, despite its economic importance. Only solitary and transiens forms have been reported from the island earlier, but not the gregarious form. Important recent outbreaks have allowed for the studying of the phase polymorphism under experimental and field conditions. Morphometric differences (pronotum size and shape, and F/C and E/F ratios) were noted among hoppers and adults caged for several generations and at various densities, in a field laboratory. These criteria were later used to study adults collected in different areas between 1996 and 2002, from populations with various densities (<1000 to >25,000 imagos/ha). Morphometric measurements revealed that gregarious red locust populations have existed naturally in Madagascar and that these were erroneously classified as transiens forms. The upper threshold density for the solitary phase was estimated at 5000 adults/ha; beyond this limit, locusts develop either into transiens or into highly gregarious forms. The southern part of the island, known as a red locust outbreak area, has harboured gregarious phases despite previous reports that prevailing ecological conditions are not suitable for its complete phase transformation. Deforestation in the northern part of the island has probably led to new favourable biotopes for serious outbreaks and gregarious populations development.

Two β-glycosidases were purified from the termite Macrotermes subhyalinus (Rambur) workers by chromatography on gel filtration, ion exchange and hydrophobic interaction columns. The preparations were shown to be homogeneous on polyacrylamide gel. Both enzymes have a similar molecular mass (68 KDa) and optimum pH (5.4) but differ in optimal temperature and thermal stability. The β-glycosidases preferred β-fucosides to β-glucosides, β-galactosides and β-xylosides, and hydrolysed glucose-glucose-β-(1–4) linkages better than β-(1–3), β-(1–2) and β-(1–6) linkages. They did not hydrolyse saccharides such as melibiose, sucrose, lactose, xylobiose, melizitose, stachyose, lactose, raffinose, laminarin, arabinogalactan, carboxymethylcellulose, inulin, lichenan and starch. β-Glycosidase A and β-glycosidase B of M. subhyalinus workers are capable of catalysing transglucosylation reactions. The yields of glucosylation of hydroxyamino acid derivatives and phenylethanol, catalysed by the two enzymes in the presence of cellobiose as glucosyl donor, were lower than those reported previously with conventional sources of β-glycosidases. In addition, the optimum pH is different for the hydrolysis and transglucosylation reactions. On the basis of this work, it is proposed that the physiological role of β-glycosidase A and β-glycosidase B of M. subhyalinus workers is the digestion of di- and oligosaccharides derived from hemicelluloses and celluloses.