Studies were made of Glossina austeni captured with sticky panels during the dry and wet season in the northern and central part of the Jozani forest on the island of Unguja, Zanzibar. The density of the fly population was significantly higher in the northern part of the forest than in the central. Female and male daily catches remained stable in time in the northern part of the forest but the density of the male fly population declined significantly in the central part of the forest at the end of the dry season. The magnitude of the catch and the sex ratio of the samples was highly affected by the trap site in both locations. Only samples in the central part of the forest were biased towards one of the sexes depending on the seasons. The age composition of the male flies was independent of locality and season but the one of female flies was influenced by the seasons in the central part of the forest. The breeding and abortion rate of flies were similar in the two locations both during the wet and dry seasons. The stability of the fly population in terms of density and composition is probably a reflection of the optimal environmental conditions in this primary forest habitat.

A 2-year study was conducted to determine the abundance of rice arthropods as affected by weeding regimes and toposequence sites, from upland to lowland, in an inland valley in Côte d'Ivoire, West Africa. Toposequence site had an effect on insect populations. Most insects were found in the moist, lower portion of the slope (hydromorphic or phreatic zone) and in the valley bottom (irrigated lowland). Among these were the white leafhoppers Cofana spectra and C. unimaciilata (Hemiptera: Cicadellidae), the green leafhoppers Nephotettix spp. (Hemiptera: Cicadellidae), and the diopsids Diopsis longicornis and D. apicalis (Diptera: Diopsidae). Stemborer damage was generally most severe in the lowland ecology. Weed dry weights and weed species composition were affected by toposequence site. Cyperns difformis L. was most abundant in the lowland and Digitarla horizontalis Willd. in the upland sites. Weeding regime had an effect on the abundance of insect pests and natural enemies (spiders and damselflies) and on the extent of stemborer damage, the effect varying with toposequence site. Implications of the results for the integrated management of weeds and insects are discussed.

A ‘rice garden’ with monthly plantings of rice was established in an irrigated lowland area in April 1993 and continued for 3 years. Populations of the most common insects, the stalk-eyed flies, Diopsis spp., and the green leafhoppers, Nephotettix spp., and spiders and stemborer damage varied distinctly in relation to month of transplanting. Arthropod populations also exhibited distinct patterns in relation to crop growth stage. Grain yields varied with month of transplanting but there was no distinct trend from one year to the next. This study indicated that continuous cropping of the same fields over a 3-year period did not result in a build-up of insect pests or a decline in grain yield.

Among the major arthropods in soil and plant samples taken from groundnut farms during the 1996 cropping season in Mali, Burkina-Faso, Niger, and Nigeria, termites in the genus Microtermes (Isoptera: Termitidae) were the most abundant and widely distributed species of economic importance. None of the termite species identified on trees in the surveyed farms attacked groundnuts. At plant maturity, termites were less frequently observed in soils taken from bare ground but were predominantly found on plants. Residues of previous cereal crops in the fields contributed to termite spread. Most of the whitegrub (Coleoptera: Scarabaeidae) and millipede (Myriapoda: Odontopygidae) species identified belonged to the genera of Schyzonycha and Peridontopyge respectively. There was a general decrease in both their population densities and the percentages of farms they infested at plant maturity compared to the early stages of the crop. Mean percentages of plants attacked by termites, whitegrubs and millipedes in the surveyed groundnut fields were 39.4, 10.9, and 9.3% respectively. Yield loss due to termites, which predominantly damaged harvested kernels, was estimated at 9.6–30.4%, and was significantly correlated with percentage of plants damaged by termites (r2 = 0.73).

The development of a single cohort of the armoured ground cricket, Acanthoplus speiseri Brancsik was followed in the environs of the University of Zambia campus, Lusaka and a preliminary life table of the grain pest constructed. The pest's total generation mortality was influenced by: failed egg eclosion, failed ecdysis, cannibalism/predation and parasitism. The egg stage had the highest percent real mortality (98.57%) and sub-mortality k-value, indicating that this was the main contributor to the total generation mortality. The rest of the developmental stages suffered lower mortalities, although that of the 6th instar was comparatively higher. A mermithid nematode, Mermis sp., and another unidentified nematode species caused 2.61% sub-mortality in the 6th nymphal instar. The constructed preliminary life table of A. speiseri is analysed and the possible causes of the observed high mortalities in the egg and 6th instar stages are discussed.

Studies on the population dynamics and species composition of the sorghum stemborers Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae), Busseola fusca (Fuller) (Lepidoptera: Noctuidae) and Sesamia sp. were conducted at Melkassa, Rift Valley of Ethiopia, during the 1990 and 1992 cropping seasons. Chilo partellus at 92% dominated the species composition. Busseola frisca made up 7.7% and Sesamia calamistis less than 1% of the borers. Occurrence of partellus declined with delay in planting until the third planting ( early June to early July) then increased during late planting in July. Busseola fusca alone, however, tended to increase in numbers with delay in planting. In Melkassa area, early planting in July could be considered as the most suitable, with low borer numbers, damage symptoms and resulting in fewer stalks with peduncle damage. Grain yield was also higher during early planting in July while the lowest yield was obtained during late planting in July. Weather factors showed no consistency but relative humidity seemed to have a significantly negative correlation with insect numbers in the last two plantings in 1992.

The pathogenic effects of Beauveria bassiana (Bals.) Vuill. (Deuteromycotina: Hyphomycetes) were evaluated against workers of the termite Odontotermes obesus (Rambur) (Isoptera: Termitidae) in the laboratory. Termite mortality ranged from 41–90% in treatments, compared with 19–21% in controls. Both lethality and lethal time varied significantly with conidial concentration and age of culture. Mycelial growth was recorded on the leg joint, abdomen, antenna, thorax and head regions of treated cadavers after 24 h. Also observed in treatments were body surface shrinkage, colour change, and hardened and brittle appendages. The role of B. bassiana in the control of O. obesus workers is discussed.

A socio-economic study was executed in South East Niger to determine the conditions under which a novel mycopesticide based on the fungus Metarhizium flavoviride could be introduced for locust and grasshopper control as a possible alternative reducing the use of synthetic chemicals. From the interviews, all farmers estimated locusts and grasshoppers to be one of three major pests. The survey revealed that 93.8% of the farmers conduct collective pesticide applications. About 45.5% of the farmers received support from the brigades, at least once. The remaining farmers (54.5%) were not assisted by the brigades due to a lack of pesticides. Farmers estimate that the choice of any pesticide greatly depends upon its knock-down ability (57.5%) or the numbers of cadavers found after a treatment (42.5%). Most farmers (82%) consider the government to be responsible for locust and migrant grasshoppers control. On average, farmers were willing to pay US$ 1.00 per ha per year, to protect their crops.

The efficacy of a field vacuum unit for the management of Bemisia tabaci was evaluated on melon (Cucumis melo L.) during two summer seasons. The tractor-mounted unit was designed to dislodge insects by blowing air from lateral vents onto the plants while simultaneously vacuuming from above. Field observations, collection of leaf samples, and hand-vacuum sampling before and after the field vacuuming were used to evaluate the efficacy of removal. Bemisia tabaci population reductions were significant (30–60%) and lasted from week to week when vacuumed weekly. Parasitoid populations were slightly affected, but were not significantly different from populations in the untreated control plot. Field vacuuming was found to be as effective as insecticide applications for the control of B. tabaci in melons.

Rice yellow mottle virus (RYMV) is one of the most economically damaging diseases of rice in sub-Saharan Africa. It is found only in Africa and the surrounding islands, where it is transmitted by insect vectors such as Tricliispa sericea Guérin, Chaetocnema piala Chapius and Sesselia pusilla Gerst., (all Coleoptera) respectively within the subfamilies Hispinae, Halticinae and Galerucinae of the Chrysomelidae; Chnootriba (= Epilachna) similis Thunberg (Coleoptera: Coccinelidae); and Conocephahis longipennis de Haan (Orthoptera: Tettigoniidae). These vectors are leaf-feeders with biting mouthparts and are abundantly present on rice and grasses in irrigated lowland fields. Transmission of RYMV is mechanical as a result of feeding damage. However, the dynamics of virus spread and the role of the vector is poorly understood. A better understanding of RYMV epidemiology requires information on the distribution, biology, host range, nature of damage, and management strategies of the vectors. It is hoped that this review will be a useful source of information in the further development of integrated pest/disease management (IPM)in rice.

The intensity of diapause of field-collected diapausing larvae of Olilo partellus (Swinhoe) and Chilo orichalcociliellus Strand (Lepidoptera: Pyralidae) was compared in the laboratory at 28 ± 0.5°C under a photoperiod of 12:12 (L:D)h. Chilo partellus terminated diapause faster than C. orichalcociliellus. Mean time to diapause termination was 9.7 days for C. partellus and 14.4 days for C. orichalcociliellus. Male and female C. partellus larvae terminated diapause and adults emerged at the same time, while significant differences were found in diapause termination and in emergence times between male and female C. orichalcociliellus.

The effect of fluoride on the food and dietary water intake and utilisation were studied in final instars of silkworm, Bombyx mori L. race NB4D2 fed ad libitum with mulberry leaves treated with sodium fluoride at concentrations of 25 ppm, 50 ppm and 75 ppm. The larval duration increased by two days while food consumption, assimilation rate, assimilation efficiency, feeding and metabolic rates increased significantly in all the treated larvae. On the other hand, the amount of faeces produced, food conversion, conversion rate and conversion efficiencies decreased significantly in all the treated batches when compared to controls. The water intake and utilisation parameters increased significantly while rate of water loss through faeces, water retained in the body and retention efficiency decreased in all the fluoride-treated silkworms. The factors responsible for these changes in treated batches are discussed in relation to the effect of fluoride on cocoon and shell weights.

Eggs and larvae of Microplitis rufiventris Kok. (Braconidae: Hymenoptera) were exposed to two sublethal concentrations (0.2 and 0.4 ppm) of the chitin synthesis inhibitor lefenuron, by feeding treated artificial diet to their hosts, Spodoptera littoralis (Boisd.) (Noctuidae: Lepidoptera) larvae. Each concentration was initiated during the egg stage or different instars of the parasitoid larvae. Between 4.3 and 33.8% of parasitoid larvae in lefenuron-treated hosts showed morphological and developmental abnormalities. The effect of the compound on the developmental rate and sensitivity of the parasitoid larvae varied according to the parasitoids' age at treatment; the egg stage and older parasitoid larvae were more tolerant to the compound than the first instars. In all treated hosts the developmental rate of the parasitoid was lower than that of controls. The lower lefenuron concentration (0.2 ppm) was more effective at disrupting the development of young parasitoid larvae than the higher one. Delayed or latent effects of the compound were evident in non-emergence of parasitoid adults that were exposed to the compound as first instars. Reduced sensitivity of old parasitoid larvae could be compatible with survival of the parasitoid in integrated control programme of S. littoralis.

Indoor-resting blood-fed Anopheles gambicie s.l. were collected from selected localities in Ethiopia. Anopheles arabiensis was the only sibling species identified. Paracentric chromosomal inversion polymorphisms were observed on the 2R and 3R arms. A significant excess of heterozygotes was obtained in samples from Siile carrying the 3Ra inversion. Similarly, significant variation was seen in the frequencies of the 3Ra inversion between the study localities. The observed intraspecific inversion polymorphisms relative to indoor resting behaviour are discussed.

Crude fractions of aerial parts of Andrographis paniculata (Burm.f.) (Acanthaceae) were evaluated for antifeedant, growth-inhibitory and oviposition-deterrent activity against larval and adult stages of the Bihar hairy caterpillar, Spilarctia obliqua (Arctiidae). The methanol fraction had the highest growth-inhibitory activity. Further fractionation resulted in nine sub-fractions of which the most active, identified as the diterpene andrographolide, displayed significant growth-inhibitory and antifeedant properties with GI50 and FD50 values of 100.4 and 159.7 μg/g diet respectively. The ethyl acetate fraction possessed the highest oviposition-deterrent activity.

Evaluations of toxicity, antifeedant, growth-regulatory activity of the methanol extract of Gliricidia sepium leaves were carried out against Dysdercus koenigii Fabr. (Heteroptera: Pyrrhocoridae), Achaea Janata Linn, and Spodoptera litura Fab., (both Lepidoptera: Noctuidae). Topical application of 100-300 μg of the extract to different stages of the test insects resulted in dose-dependent effects including larval-pupal intermediates and deformed adults. The highest tested dosage (300 μg/ μl) resulted in reduced survival rate and morphological abnormalities. At certain doses a strong antifeedant activity was evident against the lepidopteran insects.

An artificial diet developed for the rice leaffolder, Cnaphalocrocis medinalis was used in a bioassay of endotoxin proteins from Bacillus thuringiensis (Bt) strains and plant-derived protease inhibitors against the leaffolder, C. medinalis, and the yellow stemborer, Scirpophaga incertnlas. Of the 14 samples of endotoxins derived from different strains of Bt (sub-species kurstaki and sphericus) tested, 5 samples — BT 29, BT 47, BT 61, BT 70 and HD-1— were effective against leaffolder larvae in preliminary tests. Subsequent tests indicated HD-1 to be the most effective against the leaffolder, followed by BT 61 and BT 70, with non-overlapping 95% fiducial limits of LC50 values (3.9,18.2 and 41.1 mg protein/kg diet, respectively). Mortality was observed after 48 h of release of neonate larvae. In contrast, the two protease inhibitors tested, namely soybean trypsin inhibitor (SBTI) and jackfruit seed trypsin inhibitor (JSTI) were less lethal to the two pests. The latter was more effective against the yellow stemborer at much lower concentrations.

The effects of neem seed kernel extract (NSKE), neem oil (NO) and nucleopolyhedrovirus (NPV) of the Spodoptera litura Fabricius (Lepidoptera: Noctuidae) on the mortality, feeding and development of S. litura were evaluated in the laboratory. Dose-dependent mortality was evident after NPV treatment, which also depended on larval age at treatment. Upon combining NPV with neem products, the percentage mortality was enhanced threefold even at reduced concentrations. The NSKE and NO significantly inhibited the growth and development of S. litura, and extended the duration of its larval and pupal stages. Oviposition period, adult longevity and fecundity were significantly reduced following treatment with neem products and with neem + NPV treatment. The efficiencies of conversion of ingested food (ECI) and digested food (ECD) were also significantly decreased by treatment with NSKE, NO and NPV, either alone or in combination.

A laboratory study was carried out to assess the effects of seed treatment and fumigation of artificially infested cowpea with the volatile oil of air-dried leaves of Ageratum conyzoides L. (Asteraceae). The oil exerted acute toxicity on adults of the cowpea weevil, Callosobruchus maculatus F. upon fumigation. Maximal mortality of 95–97% was inflicted by 60 μl oil. Application of oil dressing on cowpea seed exhibited remarkable insecticidal activity-against the weevil. Significant oviposition deterrency and complete inhibition of emergence of adult insects (F1 offspring) from oil-treated beans were evident at doses of 2.5 μl to 10 μ1/9.5 g beans. No adverse physical effects on the beans were noticed at these doses. The major isolate of the essential oil, precocene I, was four times as active as the oil.

Nineteen specimens of Pauropoda from East Africa were studied. They belong to six species in the genus Allopauropus, 4 of them new to East Africa and 3 of them—A. etliiopicus and A. galamanus from Ethiopia and A. kemjanus from Kenya—new to science. Pauropods are reported for the first time from Ethiopia.