Nearly 8 years of intermittent treatments with temephos on the lower Volta River at Senchi Rapids, Ghana, produced no change in the susceptibility of larvae of the S. damnosum complex to temephos [Abate (R)]. In contrast, 14 months of temephos treatment in southern Ivory Coast produced resistance.

This difference can be explained by the relatively weak selection pressure exerted by the intermittent treatments on the Volta River and the frequent changes in the composition of the population as shown by cytotaxonomic identification of the larvae.

A questionnaire survey was conducted to find out the information and knowledge of extension workers on thresholds of cotton bollworms, (Helicoverpa armigera and Diparopsis castanea). A sample of 30 extension officers was interviewed in Southern and Central provinces of Zambia. The results showed crucial deficiencies in extension worker's knowledge on thresholds of key pests and their implementation in cotton IPM. More than 60% extension officers were not aware of the basic information and knowledge such as thresholds of cotton bollworms, the recommended time to start scouting (weeks after germination of cotton) and the number of cotton plants to be examined for pest observance in each field. All extension officers indicated a desperate need for more field oriented practical training on thresholds. The recent increase in the incidence of aphids, Aphis gossypii as reported by 50% extension workers is obviously due to calendar sprays of synthetic pyrethroids and the lack of a suitable aphicide in current spray programme. Demonstrations on the practical aspects of thresholds deserve much more attention at college level and also during the in-service training. More co-operation in cotton IPM training for extension officers within Central and Southern Africa is suggested.

Female sexual receptivity was studied in F1 laboratory-reared Glossina pallidipes Austen, 1903 originating from Nguruman in the Rift Valley of Kenya. Females mated as early as 6 days old but reached peak receptivity at 9–13 days old (60–80%). Females did not immediately mate with more than one male. The mean spermathecal value (MSV) was highest between 7 and 14 days of age, and declined thereafter. The duration of copulation was comparatively short (mean = 24 min), and did not vary significantly with age. High female receptivity corresponded with maturity of ovariole A, which reached maximum length at an age of 10 days. These results are discussed in relation to mass rearing of G. pallidipes.

The corn earworm damage to seven maize cultivars TZB, TZPB, WYI, 096EP6, Farz 25, ‘Kewesoke’ and Local White, was assessed during the early and late cropping seasons of 1980 and 1981 at Ikenne and Ilora located in the rain-forest and derived savanna zones, respectively. The effectiveness of dimethoate and permethrin in controlling the earworms was evaluated. All the cultivars appeared susceptible to earworm infestation in the two ecological zones. Infestation was consistently and significantly higher in the early season and also in the rain-forest zone. It ranged from 71.5 to 86% in the early and from 28 to 36.8% in the late seasons, respectively, at Ikenne. At Ilora, infestation ranged from 53 to 82% and from 20 to 75% in the early and late seasons, respectively. Mussidia nigrivenella and Heliolhis armigera were the dominant species recorded damaging the grains.

Earworm infestation was significantly lower on plots treated wtih three applications of 0.05 and 0.1% a.i. permethrin at weekly intervals than on plots that received the same dosages and sprays of dimethoate and the control. Maize yields were significantly higher on permethrin-treated plots. The lower dosage of permethrin is recommended to reduce chemical residue on maize grains.

Laboratory experiments on the role of humidity, density and species of prey were conducted in order to better understand the ecology of Teretriosoma nigrescens Lewis (Coleoptera: Histeridae), a predator introduced into West Africa to control the larger grain borer, Prostephanus truncatus. Developmental time of T. nigrescens was very similar among individuals exposed to 30,40, 70 and 90% relative humidity at 30°C, although survivorship varied. At optimal temperature and humidity larvae fed only first-instar Sitophilus zeamais as prey took longer to develop and weighed less at emergence, than those raised on first-instar P. truncatus. Larvae feeding on Tribolium castaneum took longer to develop with only 10% surviving to the adult stage. None of the larvae offered Gnatocerus maxillosus as prey survived. In an analysis of prey consumption rates, no T. nigrescens larvae survived on one P. truncatus first-instar larva per day; 50% survived on two per day, and almost 90% survived on five larvae per day. In an analysis of density effects on T. nigrescens reproduction and survivorship, there was no difference in the number of Fl offspring at T. nigrescens:P. truncatus ratios of 15:300,30:300,60:300 or 90:300, suggesting that the lowest predator: prey production ratio was the most efficient one.

Transgenic plants expressing Bacillus thuringiensis δ-endotoxins are now being used commercially in several crop species. These toxins have demonstrated good control of temperate (Ostrinia nubilalis) and tropical (Diatraea grandiosella and D. saccharalis) stemborers in maize. Resistance to B. thuringiensis toxins has been reported in over 11 species in both field and laboratory studies, demonstrating the need for resistance management strategies to prolong the efficacy of this valuable pest management tool within an integrated control programme. Resistance involves reduced binding of toxins to midgut epithelial cells and is generally considered to be a recessive trait. Resistance management will require the use of spatial and temporal refugia which may require unique schemes for each pest complex. Information is presented on the mode of action of cry toxins, resistance mechanisms, interaction of transgenic plants and biocontrol agents, and management/deployment strategies for transgenic maize in tropical ecologies.

Field studies were conducted with the synthetic pheromone of peach twig borer to determine the effect of trap distance from host plant, pheromone concentration on number of captured males and seasonal flight patterns in plum and apricot orchards. Traps placed in pomegranate plantation and in fallow land caught significantly fewer males than those placed at the centre and border of plum orchard. However, significantly more moths were caught in traps placed in pomegranate orchard than those in fallow ground. Males captured increased as the concentration of synthetic pheromone increased from 2 to 6 mg per septa. Thereafter, males captured decreased as the concentration increased.

The effects of various exposure to irradiation from cesium 137 in nitrogen and air on survival and fecundity of Glossina palpalis palpalis were compared. With doses from 3 to 21 krad in nitrogen atmosphere, male fertility was inversely correlated with dose, above 15 krad male survival was inversely correlated with dose. All males subjected to either 21 krad in nitrogen or 15 krad in air were sterilized. Females appeared to be more sensitive to gamma-irradiation than males; a dose of 6 krad in nitrogen resulted in 100% sterility and arrested further development of the ovaries after the ovulation of follicles A1 and C1. In males, this dose caused 70.3% sterility. Approximately 97 and 98% sterility were obtained when males were treated with 15 krad in nitrogen and 12 krad in air respectively. No fly emerged from irradiated puparia younger than 15 days. Irradiation of 15 or 20 days old puparia killed the insect either before or shortly after eclosion, whereas the normal patterns of emergence, survival and reproduction were observed from puparia that were irradiated when 25 days old or older.

The effects of Decis® (deltamethrin) and Systoate® (dimethoate) were assessed by the number of Megalurothrips sjostedti (Trybom) (Thysanoptera, Thripidae) recorded per cowpea plant at 40, 50, 60 and 70 days after planting (DAP), evaluated by the drop-cloth sampling method. The trial was carried out under natural infestation conditions during the 1985 early cropping season (from April to July). Systoate® was better than Decis® in controlling the flower thrips and its effect was significantly different from the unsprayed control (P = 0.01). The Decis® effect on the flower thrips was also effective in comparison with the control (P = 0.01). The effectiveness of two insecticides used in relation to pest management and the adequacy of the drop-cloth sampling method in relation to other methods are discussed.

Preferences of Maruca vitrata (Fabricius) (Lepidoptera: Pyralidae) larvae to flowers, flower buds and pods of three different varieties of cowpea (IT 82E-666, IT 82D-716 and Botokpoyi) were studied in the laboratory using a four-branched olfactometer. For each plant part, fourth instars of M. vitrata were individually exposed to a set of three odours obtained from the cowpea varieties with pure air serving as the control. Movements of the larvae in the exposure chamber were followed at two levels of choice. Results from the first level of choice showed that the attractiveness of a particular plant part to M. vitrata larvae was not significantly influenced by variety. At the second level of choice a weakly significant preference was found for flowers (P = 0.1218) compared to pods (P = 0.7530) and flower buds (P = 0.6172). In all cases, no significant difference was found between the control (pure air) and the varieties.

Dormancy is described for adults of the stalk-eyed fly, Diopsis longicornis Macquart (Diopsidae: Diptera) in the tropical savanna of coastal Guinée, West Africa. Populations of diopsids maintained themselves within each chosen refugium throughout the dry season unless the site dried up. Sex ratio within the populations at each refugium remained constant throughout the dry period. Slightly more females than males were found (56%), and of these only 0.8% were gravid. Movement of stalk-eyed fly adults from the rice field to the refugia corresponded with the end of the rice cropping period (stage of ripening and harvest) at the end of the wet season (late October to November), whereas movement from the refugia to the rice field occurred towards the end of the dry season Gate (May/early June), but well in advance of the rice crop planting (July and August) of the following wet season. Insects retained their state of reproductive arrest in the dry season even when offered suitable oviposition sites, i.e. rice plants. Secondary host plants were investigated as possible oviposition sites and food sources for adult flies.

Studies on developmental biology and feeding and ovipositional preferences of the pea leaf miner, Chromatomyia horticola (Goureau), were carried out on 11 varieties of field peas, Pisum sativum L. Two varieties, P-200 and P-402, offered maximum resistance to the development of pea leaf miner by inhibiting growth as both larval and puparial development were prolonged, and adult longevity, survival and fecundity reduced. These varieties were also least preferred for feeding and oviposition. Differences between the moderately resistant HFP-4 and highly susceptible varieties HFP-5, HFP-6, HFP-12, PG-3, RAU-21, RAU-25, RAU-37and T-163 were not well marked, as most of these had a relatively high value for the developmental success index, based on indices for larval-puparial development, adult longevity, survival and fecundity, and were also highly preferred by the ovipositing females. Variety PG-3, though offering some resistance to development, was highly preferred for oviposition. The local variety T-163, was the most susceptible variety, as it had the maximum value for the developmental success index, and was highly preferred by ovipositing females. The physiological basis of resistance in the two pea varieties is suggested to be mainly non-preference and antibiosis.

A laboratory study of the biology of Corcyra cephalonica (Staint.) was made at 30°C and 70% r.h. on sorghum. The number of eggs laid per female, oviposition period, development time and survival from egg to adult were determined. The data were used to estimate the finite rate of increase and the intrinsic rate of natural increase of the moth. For the finite rate of increase (λ) the estimated value was 18 per lunar month, corresponding to an intrinsic rate of natural increase (r) of 2.9. The results are compared with published data and it is concluded that the pest potential of C. cephalonica has been, hitherto, underestimated.

This paper is based on experiences obtained during a joint enterprise between the Social Science Interface Research Unit, of the Crop Pests Research Programme, and the Livestock Ticks Research Programme at ICIPE. Topics bearing on technology design and development are emphasized.

The resource-poor farmer as conceptualized within ICIPE and reinforced by research experience, is by definition a person who operates a diversified system of production in which food security concerns and cash income intakes are crucial.

The family/household provides most of the labour required in production in African farming communities. For this reason, their labour investment into the adoption of novel activities or technological innovation and their assessment of the value of such innovations requiring changes in their normative practice, is appraised primarily in terms of the returns they would get for the additional labour input.

It is noteworthy that much of the so-called family labour is, in fact, female labour. It is therefore arguable that the perception of the women of technological inputs and innovations as profitable, is crucial for the successful adoption and social acceptance of novel technology.

Although agricultural land is in increasingly short supply, it would appear that the crucial limiting factor in production is not a shortage of land per se, since a good number of households do not fully exploit all the agricultural land at their disposal. Labour, and/or cash income to secure additional labour, appears to be the most important constraint to production. This tends to suggest that for future technological interventions in agricultural systems of the rural poor, consideration will have to be given to inputs which optimize the use of family/household labour.

The escalating population growth suggests that focus on women's health and incomes could significantly and qualitatively improve the prospects for the adoption of new and improved technology in areas such as pest and vector control.

Field experiments at the Msekera Regional Research Station during 1988–1990 and at Masumba (Luangwa Valley) Sub-station during 1989–1990 showed that six groundnut genotypes—ICG.485, ICG.2271, ICG-2306, ICG.5041, ICG.5045 and HyQ (cg) S-10 were distinctly less susceptible to the leafhopper, Empoasca dolichi (Paoli). ICG.2271 also appeared to combine low susceptibility to early leaf spot, Cercospora arachidicola Hori and good yield potential. This genotype as well as ICG.5041 and ICG.5045 also are known to be resistant to thrips and/or termites. The scope for their utilization in exploitation of leafhopper resistance in groundnut improvement programme in Zambia is indicated.

Field studies revealed the nettle caterpillar, Latoia ( = Parasa) viridissima, to be multivoltine with four discrete generations a year. The maximum egg (1800/100 fronds) and larval (1500/100 fronds) densities were attained in April/May 1980. The pupal population was generally low; the highest recorded density of 54/100 fronds was attained in March 1980 during the first generation.

Samples of larvae and pupae from the field were attacked by parasitoids in the families Bombyliidae, Braconidae, Chalcididae, Chrysididae, Eulophidae, Ichneumonidae and Tachinidae. These contributed to mortalities ranging from 6 to 30%, but their combined action with microorganisms (bacteria and fungi) accounted for 28–65% mortality of the insect.

Plumbagin, a napthoquinone from the plant Plumbago zeylanica, delayed pupation when topically applied to newly moulted final instars of the leaf eating caterpillar Opisina arenosella Walker (Lepidoptera: Oecophoridae). Pupae from treated larvae emerged into non-viable adults and had abnormalities such as deformed wings and shrunken abdomens; they also died much before the control insects. The results suggest that plumbagin interferes with the process of development and ecdysis of the insect.

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.

Parasitization of P. brassicae L. by A. glomeratus L. was found to be between 63.79 and 76.52% in Farm 1 and 92.68 and 93.43% in Farm 2. Population density of the parasitoids ranged between 35.16 ± 6.05 and 57.76 ± 13.20. The developmental period of the parasitoids within the host was 21 days and the pupal period 9 to 10 days. The population of the parasitoid showed a steady increase during November–December. The rate of pupation of P. brassicae showed a decline from 36.21% in mid-November to 23.48% in later November in Farm 1 with an early crop. In Farm 2 with a late crop the pupation rate dwindled from an already low 7.32 to 6.57% by late December.

Pearl millet, Pennisetum americanum L. occupies a large proportion of the area growing millets in Africa. Consequently the insect pests that attack this species have received attention over other millets. A list of the major species is presented. Actual data on losses due to insect pests on pearl millet are not readily available. Crop loss assessment methods using incidence and damage ratios are discussed. Quantitative losses determined from insecticide trials at research station are also presented.