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.

Comparative field studies were conducted during the rainy and dry seasons at the Mbita Point Field Station of ICIPE in southwestern Kenya, to investigate the pattern and rate of dispersal of Aphis craccivora on aphid-resistant (ICV-12) and aphid-susceptible (ICV-1) cowpea cultivars in relation to key weather factors. The effects of the dispersal trends on crop performance and aphid population dynamics were analysed. Treatments consisted of initial aphid releases at the north, south, west, east and centre of test plots and uninfested controls maintained on plants for 22 days. Parameters recorded included: pattern (direction of spread of aphids) and rate (number of aphid-infested plants at a given time) in test plots; crop growth and yields and associated factors such as incidence of sooty mould and plant mortality, and aphid density and associated factors, including the incidence of natural enemy species, particularly coccinellids. Dispersal was fastest when releases were made in the west, north and centre of plots, and resulted in adveVse effects on ICV-1 growth and yields. Infestations of ICV-12 did not significantly affect crop performance. There was an apparent direct, positive relationship between wind direction and pattern of spread of aphid infestations, but this pattern was more apparent during the rainy season, when wind speeds were higher, than during the dry season. The incidence of natural enemy species correlated with the spread of aphid infestations, while the abundance of coccinellids correlated with aphid density.

The International Red Locust Control Service (IRLCS) was formally established in 1949 with the primary objective of controlling locusts in their outbreak areas, thereby preventing the recurrence of plagues. The name of IRLCS was subsequently changed in 1970 to the International Red Locust Control Organisation for Central and Southern Africa (IRLCO-CSA), but retained the same objectives. Over the years, IRLCO-CSA has experienced changes in membership and locations of its Headquarters and operational centres. Its principle mandate has remained the same even though it has been modified and rationalised from time to time. The organisation carried out investigations that led to the identification of the red locust outbreak areas and the development of various control technologies. Control methods developed from the original physical ones which were laborious and inefficient; to insecticide dusting and baiting; to the spraying by aircraft. In its history of locust control programmes, IRLCO-CSA has used arsenic compounds, BHC, DNOC, dieldrin and fenitrothion as insecticides. The success that IRLCO-CSA has enjoyed in its 50 years history has been thanks to the cooperation of countries in eastern, central and southern Africa which are vulnerable to attack by the red locust, and the international community.

This paper gives an account of the activities of the International Red Locust Control Organisation for Central and Southern Africa (IRLCO-CSA) in the management of the red locust, other locust species and non-locust migratory pests in the 1980s and 1990s. It also analyses the advances made by IRLCO-CSA in implementing a preventive control strategy so as to avoid future plagues and outlines the activities of IRLCO-CSA during periods of locust recession.

There were widespread upsurges throughout the 1980s into the 1990s, with outbreaks being recorded throughout the period 1985–1997. Without doubt, the period 1981 to the present, was the most active since the suppression of the last plague in the 1940s. It is concluded that the threat of red locust plagues is not yet over and that the continued existence of IRLCO-CSA remains key to the food security needs of the region.

Aphis gossypii is one of the major pests of cucumber grown in greenhouses in the coastal areas of Morocco. A population dynamics study showed that A. gossypii populations might reach very high levels in June, causing economic damage to cucumber. The proliferation of A. gossypii on cucumber arises mainly from infestations by flying winged adults. Factors regulating the fluctuation of population of the species 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.

The host plant spectrum of Aphis gossypii Glover (Hemiptera:Aphididae) was assessed from 1991 to 1994 in the cotton-growing zone of northern Cameroon. The aphid is generally present on cotton (Gossypium hirsutum L.) and okra (Abelmoschus esculentus (L.) Moench) during the rainy season. During the dry season on the other hand, A. gossypii is observed on a very wide range of plants (63 families, 192 genera and 302 species). During this season, all types of plants, especially legumes, dry-season crops and various types of trees, are colonised. From the representativeness of the sampled plant species within the cotton zone of Cameroon, it is concluded that a part of the A. gossypii population survives the dry season in the Sudano-Sahelian African zone, thus forming numerous reservoirs scattered among plants and in very varied habitats.

The red locust, Nomadacris septemfasciata (Serville) is one of the major plague locust species of serious potential threat to agriculture in Zambia. Two of its eight outbreak areas, Mweru wa Ntipa plains and the Kafue Flats, are found in Zambia. The Kafue Flats have now become more important because of high levels of locust activity, occasionally forming swarms. Locust control in Zambia has been mandated to the International Red Locust Control Organisation for Central and Southern Africa (IRLCO-CSA), a regional cooperative effort of 8 member countries. Regional cooperation for locust control has proved practical and economical for Zambia.

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).

Gregarious swarms of red locust, Nomadacris septemfasciata (Serville) capable of causing loss to agriculture originate from specific breeding areas in eastern and central Africa often referred to as outbreak areas. Typically these areas are poorly drained grassland plains that flood during the wet season and then dry out, creating sites for egg laying and stimulating growth of specific types of vegetation necessary for nymphal survival. During 1996, a significant upsurge of red locust occurred throughout central and western Tanzania. Populations also appeared in the Bahi Plains west of Dodoma, an area where significant infestations of red locust had not been recorded since the major plague of 1930–1944. Aerial spraying controlled 13,700 ha of nymphal bands and swarms. The 1996 upsurge could have been caused by a number of contributing factors: a prolonged drought leading to changes in vegetation; possible changes to flood water levels through diversion for irrigation; and either an undetected movement of red locust into the area from outside or localised breeding over several seasons. As a result of this outbreak the Bahi is likely to remain as a possible source of red locust swarms in the future and should be monitored closely.

The termite species Psammotermes hybosloma Desneux and Anacanthotermes vagans (Hagen) foraging in the desert ecosystem of Kuwait preferred to consume dried leaves of Tamarix aphylla (L.) and Rhanterium epapposium Oliv. over the other plant species tested. This preference varied with season. The termites consumed more food during summer than winter, with the highest consumption being recorded in September, the time of the year when the food plants dry up and can be readily cut into fragments which are carried by workers to the underground nest. These results indicate that the contribution of termites to the removal of desert vegetation is less than that of other soil fauna.

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 development of a regional control strategy for the red locust, Nomadacris septemfasciata (Serville) began in the 1920s during a period when red, desert and African migratory locust swarms were widespread in Africa. The strategy involved controlling locusts in their permanent breeding areas to prevent swarms escaping over a much larger invasion area and damaging crops and pasture. Mapping and analysis of reports at the Imperial Institute of Entomology in London and field research in the Rukwa and Mweru wa Ntipa areas confirmed the location of two important red locust outbreak areas, and by the mid-1930s implementation of a preventative control strategy became a practical proposition. Regional control against red locusts formally came into being in 1941 under impetus from the Belgian and British Governments and collaborative surveying and control work continued despite the Second World War. Locust swarm activity intensified in the mid 1940s and other outbreak areas were found, raising the profile of the threat red locusts posed to food security. As a result, international collaboration in research, control and information dissemination was formalised in 1945 through the formation of the IRLCO-CSA.

Termite damage to annual crops on smallscale farms was surveyed in eight areas in southern Malawi during 1989/90 to 1991/92. The most frequently grown crop was maize, followed by pigeonpeas, Phaseolus beans, cotton, cowpea and groundnuts. Twenty-seven species of termites were found attacking crops. The most numerous and widely distributed were several species of the Macrotermitinae, including Ancistrotermes latinotus, four species of Macrotermes, four species of Microtermes, three species of Odontotermes and Pseudacanthotermes militaris. All species damaged maize but only a few damaged bambara, cassava and banana. The damage appeared to be more frequent in dry areas than in wet ones.

A survey for laccase, an enzyme involved in phenol oxidation, was carried out in 23 termite species from three different feeding guilds. In soil-feeding (6 species) and wood-feeding (7 species) termites, laccase activity was not detected. In contrast, all the fungus-growing termites (10 species) tested showed laccase activity. The symbiotic fungi (conidia) and fungus combs showed higher activity than the termites themselves in 6 species: Macrotermes bellicosiis, M. miilleri, Odontotermes sp., O. sp. aff. interveniens, Pseudacanthotermes spiniger and P. militaris. Fungus combs always had the highest laccase activity. The absence of laccase activity in soil-feeding and wood-feeding termites is discussed. The presence of laccase activity in both termites and Termitomyces constitutes novel information relevant to the degradation of phenols.

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.