Three severe outbreaks of cassava mealybug (CM), Phenacoccus manihoti, have occurred in Zaire. Two were associated with droughts. The third occurred in the driest part of the country and ended only when nearly all cassava plants had been killed. Native coccinellid predators sometimes greatly reduced CM populations, but only after the cassava crop had been heavily damaged. The exotic coccinellid Diomus sp. may be an effective biological control agent in Kinshasa, where CM on a hybrid form of cassava remained common during the rainy season. CM populations in Kinshasa declined greatly in the second year after the release of the exotic parasitoid Epidinocarsis lopezi. In one study the number of mummies with E. lopezi increased with host densities up to 20 CM per shoot tip. Since CM populations remained low after the releases of E. lopezi it is tentatively concluded that E. lopezi, despite considerable rates of hyperparasitism, prevents CM outbreaks over the whole area of its distribution (130,000 km2) in western Zaire.

Cassava is one of the most important staple crops in Ghana. Losses from the cassava mealybug (CM), Phenacoccus manihoti, and cassava green mite (CGM), Mononychellus tanajoa, infestations in 1983 were estimated at 0.8 m metric tons of tubers. An integrated control programme with biological control playing a key role has been established within the Plant Protection and Quarantine Unit of the Ministry of Agriculture. Of the five beneficial insect species released, only the parasitoid, Epidinocarsis lopezi has so far been established against the CM over the greater part of Ghana. Damage caused by the CM has been reduced quite remarkably, largely due to E. lopezi, with local beneficial insects playing some contributory role. The activity of hyperparasitoids is high and reduces the overall efficiency of E. lopezi.

The effect of CGM is prominent now, perhaps because of the reduction in CM. Exotic phytoseiid mite species were released but no establishment could be documented.

A regional programme, involving seven national programmes and three international agencies, has been launched in East Africa to promote research on the biological control of cassava green mite, Mononychellus tanajoa (Bondar) sensu lato. The organization and objectives of the programme are described and outline results of the first 2 years of work are reported. Trials to assess losses due to mites were carried out at 10 sites, using acaricides to protect split plots of two to five varieties in each trial; at 6 sites, significant losses of tuber yield were recorded on one or more varieties. Surveys of indigenous natural enemies indicated that the predator complex is similar throughout the region and does not provide adequate green mite control. Two Neotropical phytoseiid predators have so far been introduced for local evaluation. One of these, Neoseiulus idaeus, has been released at 12 sites in three countries; recoveries were made at several sites, but no impact on the pest population was detectable. Plans for further collaborative work are discussed.

The purpose of the Africa-wide Biological Control Programme (ABCP) training programme is to develop a biological control capability in Africa. The establishment of National Biological Control Programmes (NBCPs) will be done in two phases—the initiation phase of 2 years during which specialists will be trained on a short-term basis to enable them to carry out releases of natural enemies of cassava pests as well as pre- and post-release surveys, and the establishment of full-fledged NBCPs run by personnel trained at M.Sc. and Ph.D. levels. Anticipated difficulties in establishing and maintaining NBCPs and possible solutions are discussed.

A systems model is described for cassava, Manihot esculenta Crantz, two of its introduced herbivores, the cassava green mite (CGM), Mononychellus tanajoa (Bondar), sensu lato, and the cassava mealybug (CM), Phenacoccus manihoti Mat.-Ferr., the introduced CM parasitoid, Epidinocarsis lopezi (DeSantis) and coccinellid predator of the genus Hyperaspis. The systems model includes the effects of weather, soil nitrogen and water levels on the interactions of the system's components.

The model simulates the distribution of developmental times of cohorts initated at the same time, as well as the number and biomass (energy) dynamics of all populations over time. Biomass acquisition and allocation at the population and organism subunit levels (e.g. leaves, fruit, ova) were also simulated. A common acquisition (i.e. functional response) submodel was used to estimate daily photosynthetic as well as nitrogen and water uptake rates in cassava, in addition to herbivory, parasitism and predation rates for the arthropod species.

This paper presents an overview of the systems model. Simulation results for the plant under pest free conditions were compared to field data. In addition, the model was used to estimate tuber yield losses due to CM and CGM feeding, and to examine the beneficial effects of introduced CM natural enemies as measured by reductions in tuber yield losses.

University training of entomologists, especially taxonomists in tropical Africa is examined. It is concluded that generally the education of entomologists in the subregion is very poor. Teachers with correct training and orientation are either lacking or when available do not receive the necessary incentives for effective teaching. Supporting facilities for academic work are either missing or where present have deteriorated to the extent of being almost useless. The situation is thought unlikely to improve in the foreseeable future. It has been suggested that international institutions in Africa concerned with the proper progress and development of Insect Science should take steps to organize a comprehensive master's degree programme in entomology along the Rivers State University of Science and Technology curriculum pattern. Alternatively, the duration of the Ph.D. course work may be increased to 9 months as suggested in the paper. This should help to produce at least some educated entomologists and hopefully some taxonomists for the continent.

Risk minimization is a main objective for the farmer in the Sahel, as the probability of insufficient and erratic rainfall is high. Considering the precarious situation of the Sahelian farmer, any development and implementation of integrated pest management (IPM) should be based on traditional farming systems. The need is emphasized for training of personnel dealing directly with farmers. Pesticide use is common in the Sahel and these chemicals are often available free of charge. Therefore, considerable attention should be given to training of personnel of crop protection services, in management of pesticides and environmental toxicology. The research institutes, crop protection services, extension services, and the training centres are all in need of personnel with higher, middle and lower levels of training and have great difficulty in satisfying these needs. In national agricultural schools and universities the development of adequate and locally applicable curricula should be stressed, that includes crop protection; lecturers should be trained for this purpose. Regional training centres may have an important function in providing high standard training at different levels, and in generating IPM information. In the Sahel, the regional training centre for crop protection is based in Niger as an integral part of a large crop protection programme of CILSS (Permanent Interstate Committee for Drought Control in the Sahel). The activities planned for the near future are described.

Developing countries lack the indigenous scientists necessary to achieve a critical mass of manpower for the effective implementation of research and development policies. The need to train research scientists in the insect sciences is discussed and it is concluded that to provide training on relevant topics, given in the appropriate teaching and learning environment, more training must be available in developing countries. The resources for teaching and research in these countries are inadequate, but although they are scattered they are not absent. It is proposed that regional collaborative training programmes will combine the facilities of universities, for their academic tradition and for teaching, with those of research centres, for research and supervision. The structure and experiences of the African Regional Postgraduate Programme in Insect Science (ARPPIS) are presented as a model for a regional graduate training programme in developing countries. ARPPIS is a collaborative venture between 12 African universities and the International Centre of Insect Physiology and Ecology, leading to the award of the Ph.D. degree.

The paper attempts to assess the current status of books and other resource materials for training tropical entomologists and to suggest ways and means of developing appropriate materials. Attention is drawn to the increasing importance of the study of insects in the tropics and hence the need to train more and more entomologists of all categories and specialization.

Noting the fact that most textbooks used at all levels of university teaching mainly concentrate on describing temperate situations, it is suggested that entomologists in the tropics should make special effort to write books that discuss and give examples of situations obtaining in tropical areas.

In recognition of the close link existing between theoretical and practical work, writing of clear and detailed manuals and guides to help students in the practical aspects of entomology should also be encouraged. Related to this aspect of training, engineering workshops where equipment necessary for practical exercises or research can be designed and constructed should be developed so as to minimise problems caused by inability to import such equipment.

The shortage of insect taxonomists is highlighted and a number of measures to overcome this problem are suggested.

Individualized instruction has been demonstrated to result in higher student comprehension and retention. There is a need in pest management training programmes for better quality visual materials which may take many forms. This paper reviews the development of a cadre of slide/text, slide, slide/tape, and computer aided pest management instructional materials currently in use at the University of Florida (USA) and the Pan American School of Agriculture (Honduras, Central America). The teaching philosophy under which they were developed, and problems with the media and their usage, are discussed.

Data is provided on available short courses in plant protection and on FAO's training activities. FAO's findings on training needs of manpower for agriculture and rural development in Africa are briefly discussed. The need for a national plan for plant protection which can be implemented gradually is stressed. Such plans should be the basis for identifying realistic training needs. Regional co-operation for providing post-graduate training in plant protection is required. Training is especially needed in developing and in introducing safe, economic and effective plant protection measures at farm level. To achieve this, a multi-disciplinary approach is required and relevant training should be given to administrators, researchers, extension personnel and farmers. Of the various subject matters of entomology, in particular, more training is needed in biological control, being one of the cornerstones of the IPM strategy.

In the major breeding areas of tropical migratory locust, Locusta migratoria migratorioides (R. & F.) in Mali, Chad, Sudan and Madagascar, man has played a vital role in maintaining locust numbers above the levels found in undisturbed environments, through his agricultural and pastoral activities. Recent rapid agricultural development, particularly broad-acre cultivation of mono-cotyledonous summer crops in areas climatically suitable for migratory locust, has caused population upsurges in new areas, which have occasionally led to outbreaks and plagues. Some outbreaks appear to have been a reaction to the initial disturbance and have never recurred while others recur when meteorological conditions are favourable. Continued agricultural development in tropical and sub-tropical areas of the Old World will bring the risk of further upsurges of tropical migratory locust.

Several Arthropod pests have been collected and identified on coffee, Coffea arabica. L. in Ethiopia, but only a few are economically important. Based on the plant part the pests feed on, they can be categorized as flower and flower bud feeders, leaf feeders, berry (fruit) feeders, twig and branch feeders borers and stem (trunk) borers.

Antestia, Antestiopsis intricata (Ghesquiere) Carayon and blotch leafminer, Leucoptera Caffeina (Washbourn) are the two most important pests feeding mainly on young fruits and leaves respectively.

Studies made regarding biology, feeding habits, population dynamics and natural enemies (parasitoids and predators) of Antestia are described. The buildup of this insect starts in March and reaches its peak around May/June although slight variations have been observed in various coffee growing areas. Young berries are the most preferred part of the plant. Antestia eggs 45–50% are attacked mainly by three species of parasistoids of which Asolcus suranus (Nixon) was found to be the most important.

Over a 9-month period, samples of maize and sorghum seeds were purchased monthly from markets located in three contiguous climatic zones of Nigeria; the grain samples were examined and insect pests found on them were recorded. Species of Sitophilus, Rhizopertha and Sitolroga accounted for 57–84% of all insect pests collected from the two grain types. Significantly more insect pests were recorded on grains obtained from the southern guinea savannah zone than from the northern guinea and sudan savannah zones. The relative incidence of the insect pests in the three zones is related to moisture availability reflected in grain moisture content.

In North Africa, the potato tubermoth Phthorimaea operculella (Zeller) is an important pest in traditional, non-refrigerated potato stores. A collaborative research programme of the Institut National de la Recherche Agronomique de Tunisie (INRAT) and the International Potato Center (CIP) investigates the relationships between, (a) the dynamics of the field populations, (b) the harvest date, (c) the economic damage in the field, and (d) the subsequent damage in stores under Tunisian conditions. Emphasis was given to the identification of cultural practices that allowed reduction of pesticide applications and to the replacement of the commonly used parathion with less toxic products.

Potato tubermoth control was achieved by applying a synthetic pyrethroid (permethrin) or Bacillus thuringiensis at the beginning of the storage period. The latter, however, seemed to be less effective on tubers with a high initial infestation (over 20%). The studies showed that tuber damage could be avoided by an early harvest and insecticide applications in the field were not indicated.

An integrated control approach including an early harvest date (to reduce initial tuber infestation), and the application of B. thuringiensis or a synthetic pyrethroid is being developed.

The life patterns of cassava green spider mite populations were compared using characteristics of spinning behaviour and other associated biological parameters so as to determine the possibility of using these criteria for separating closely related forms or populations of Mononychellus complex of species. These included web structure and density, preferred site for oviposition, feeding, walking, defecation, quiescence, spinning behaviour during walking and type of egg cover. Of these, preferred site for feeding, walking, quiescence and spinning behaviour during walking were found to be consistent and could possibly be used in comparative studies on different mite populations. The surface structure of the leaves i.e. pubescence, and mite population density were found to affect some of the behaviour patterns. Detailed studies on the influence of other factors, such as host plant variety, stage of plant growth, age of leaf colonized, weather, etc. will be necessary to determine the usefulness of these biological criteria in separating sympatric and allopatric populations of the mite.

A random sample of 90 small scale cotton growers was selected and interviewed in three target areas, to investigate the perceptions of farmers towards cotton insect pest management in Zambia. Information is given on farmers control practices, their perceptions of insect damage and the effectiveness of control. All farmers interviewed were knowledgeable about the common insect pests of cotton. The American bollworm (Heliothis armigera), red bollworm (Diparopsis castanea), and aphids (Aphis gossypii) were reported to be the worst pests. Some farmers use more insecticide applications than is locally recommended probably because they overestimate potential losses. Many farmers felt that the insecticides they use (pyrethroids) are very effective against pests. In some cases, the ED formulation of cypermethrin was reported to be more effective than EC formulations. The commonly practised nonchemical methods of insect control are growing cotton in rotation with other crops and destruction of cotton plants after harvest. Only a few farmers were aware of the role of biological control and the significance of weeding in cotton pest management. Many farmers inspected their crops to decide the timing of spray applications but did not follow the recommended scouting methods.

Ninety farmers selected at random from three cotton growing districts of Zambia were interviewed to assess the current status of training and other sources of advice available, to help them in insect pest management of cotton. Training courses and demonstrations on pest control were attended by only about 50% of the farmers interviewed. The training, organized mostly by Government Farm Training Institutes, emphasized general aspects of cotton production. Whereas the demonstrations on chemical control were occasionally organized by multinational companies like ICI, Hoechst, and Shell Chemicals. Ninety-two per cent of the farmers were aware of the extension workers in their respective areas and were visited on an average of 4.8 times per growing season. The ratio of extension workers to small scale cotton farmers is reported and the means of communication are discussed. The other sources of information on cotton pest management available to farmers were radios, field days, leaflets and informal discussions within the farming community. Farmers expressed the need for more advice on methods of insect scouting and application of insecticides on cotton. Farmers generally felt that cotton pest management can be improved by introducing frequent training courses, increased number of extension workers coupled with demonstrations in cotton fields. The average yields of seed cotton obtained by trained farmers was 759.39 kg/ha as compared to untrained farmers who obtained 719 kg/ha.

I am an occasional migrant to the tropics from a colder northern climate and was therefore a little surprised when I received an invitation to present this final plenary lecture of the First International Conference on Tropical Entomology. But, although it is many years since I was a resident tropical entomologist, my contact with tropical agricultural entomology and taxonomy goes back more than 30 years. In 1955 I was appointed to the Nigerian Federal Department of Agricultural Research, Moor Plantation, Ibadan to carry out field research on the biology and control of insect pests on sorghum, bulrush millet, maize and rice.