Initial findings are reported from a study of Exhyalanthrax spp. (Diptera, Bombyliidae) and Chrestomutilla spp. (Hymenoptera, Mutillidae) parasitic on tsetse pupae, with a view to their use as control agents. The behaviour of bombyliids in the field and in cages is described and related to problems encountered in laboratory rearing. Limited progress is also reported in the breeding of mutillids. Prospects for the application of pupal parasites in biological and integrated control of tsetse are discussed.

Urine from the buffalo, Syncerus caffer, a natural host of the tsetse, has been shown previously to be a potent olfactory attractant for tsetse in the field. The attractant compounds have been found to be extractable into dichloromethane. Fractionation of the extracts by liquid flash chromatography yielded four fractions one of which gave a seven-fold increase in trap catches in the field compared to the control traps. Gas Chromatographie and gas chromatography–mass spectrometric analysis of this fraction revealed the presence of seven simple phenols including phenol itself.

Entomological investigations in Dubai showed that, irrespective of whether they had been fed on water or 10% sugar solution, about 47% of Aedes caspius females matured eggs autogenously during their first ovarian cycle. Several blood-fed females were trapped in cages, and precipitin tests showed that some had fed on birds and camels as well as man.

Absence of autogeny combined with an examination of male terminalia showed that adults of the Culex pipiens complex were in fact Culex quinquefasciatus. The population was unusual because females were not inseminated when kept in cages, and appeared only weakly anthropophagie. CDC light traps and out of door resting cages proved useful in sampling adults. Precipitin tests showed 31.7% to have fed on birds, 7.9% on camels and only 3.2% on humans.

The number of eggs matured by Ae. caspius and Cx. quinquefasciatus were determined, and studies were made on the hatching pattern of Ae. caspius eggs. Larval habitats of Ae. caspius were unusual in having high concentrations of calcium chloride. Breeding places of Cx. quinquefasciatus comprised very polluted waters. Collections of the immature stages allowed the construction of stage-specific age-frequency histograms for both species, and survivorship curves to be plotted.

Dosage–mortality responses of F1 progeny of treated rice weevils, Sitophilus oryzae, indicated that the weevil is highly tolerant to R-20458. However, the ability of the insect growth regulator (IGR) to suppress F2 progeny production, demonstrated that R-20458 could be used as a protectant for grains.

Field trials were conducted to assess the effectiveness of a parasitic nematode, the DD136 strain of Neoaplectana carpocapsae Weiser in controlling Heliothis zea (Boddie) on naturally infested sweetcorn.

Nematode suspensions at concentrations of 0, 4 × 103, 4 × 104, 4 × 103 (applied twice) and 4 × 104 (applied twice), nematodes/ml respectively, were sprayed on the ears at early silking stage.

Treatments with 4 × 104 nematodes/ml sprayed twice at 3 days interval gave significantly better control (55%) than the rest. The mean number of surviving H. zea larvae was also significantly reduced with increasing concentrations of nematodes. Economic damage was not prevented but damage to treated ears was significantly lower than that of the untreated plots.

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.

The repellent ‘Simno’, which is made in Ghana from edible plant products, was tested in two forms as base-oil and a cream. Biting catches were made by bait subjects with one leg only smeared with a measured amount of ‘Simno’. The catches from each leg were then compared. The base-oil was only tested against Simulium damnosum s.l. It was found to be 100% effective for over 10 hr even after 2 years storage. The repellent cream worked well against a biting midge and various mosquitoes as well as S. damnosum s.l, but was seldom completely effective and the potency varied between samples. Nevertheless, one sample retained its full potency after 2 years storage. ‘Simno’ repellent is convenient to use (especially the cream) and is well accepted by the local people. The active ingredients of'Simno’ need to be identified.

Investigations on sandfly breeding sites in Marigat, Baringo District, in Kenya were carried out using a soil incubation technique. Soil samples from natural resting sites were collected, incubated and observed daily for emerging adult phlebotomine sandflies. This technique proved to be the best in the recovery of phlebotomine sandflies from known resting sites. Ten sandfly species were recovered from soil collected from animal burrows and termite hills.

Studies of outer chorionic sculpturing of eggs of four species of sandflies were carried out by the use of scanning electron microscope. Two species, P. martini and S. garnhami, which utilize similar resting sites, termite hill ventilation shafts, had similar chorionic sculpturing, while two other species (S. bedfordi and S. kirki) which use several resting sites, i.e. rock crevices, tree holes and termite ventilation shafts, had chorionic sculpturings which were dissimilar.

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.

Descriptions and morphometrics of the eggs and waxen structures on the nymphs and adults of Orthezia insignis are given. Architecturally, the waxen designs are similar throughout the nymphal instars but vary in the construction details. On the newly hatched (issued) nymphs only structural outlines are visible under a binocular microscope and on older instars, wax secretions become progressively more copious and conspicuous. At adult stage, the greatest amount of wax is used to construct the ovisacs. Reproduction was parthenogenetic and embryogenesis was characterized by three colour changes of the eggs: the white, newly laid eggs successively turn light yellow; bright yellow and then brown before eclosion. The frequency of nymphal issuance was influenced by the relative positions of the egg batches inside the sac. Nymphs hatching from eggs laid late in life, took longer to scramble out of the sac. Evidence deduced from the rate of nymphal issuance and the mean number of light yellow eggs at any given time, suggested that ovulation, embryogenesis and eclosion are probably synchronized biological activities in Orthezia.

Development of nymphs in the laboratory took approx. 42 days and was marked by three stadial stages. Morphometrics of the right metathoracic femurs from dead nymphs and exuviae reliably confirmed a similar developmental pattern in wild population.

Simultaneously or selectively, nymphs and adults of Orthezia insignis used physiological age of the host-units, the relative sizes of sap pathways and the concentration of photosynthates to choose feeding and/or oviposition sites, depending on the state of the host plant. On the non-flowering plants, physiological age and relative sizes of pathways were the principal determinants, while on flowering food plants all the three criteria were used although the sink-photosynthate-concentration factor had a decidedly dominant influence on Orthezia than otherwise.

The cotton whitefly, Bemisia tabaci (Genn.), is parasitized by four Aphelinid species: Eretmocerus diversiciliatus Silv., E. mundus Merc., Encarsia lutea Masi. and an unidentified Encarsia sp Whitefly adults move from field weeds onto cotton during the period September–November. The application of broad-spectrum insecticides to control other cotton pests early in the season prevents the establishment of the host-stage of B. tabaci needed by the parasitoids within cotton fields during September and October. The rate of parasitism is consequently decelerated to peak in January towards the end of the season. Peak per cent parasitism for treated cotton fields was 36.7 as compared to 76.8 in untreated fields. This has promoted B. tabaci to an all season pest instead of an early and mid-season occasional pest. Alternative control strategies for early season pests are discussed.

Five barley varieties, viz. Proctor, Kenya Research, Tumaini, MPYT 169-2Y and Can B35/2, were tested in the field to evaluate their resistance traits to D. flavibasis. Can B35/2 was identified as a moderately resistant variety useful for reference in further work. The varieties were observed to recover their growth after the infestation. Visual growth recovery scores in the field experiments suggested the tolerance type of resistance.

A forest ecosystem was divided into four zones: the original primary rain forest, secondary forest of short trees and bushes, tertiary Lantana thickets, and fallow plots. Tsetse, Glossina pallidipes Austen, were trapped in the four zones, dissected and the incidence of infection by the non-occluded virus determined. Tsetse density was relatively higher in the fallow land, and lowest in the primary forest. Virus infection was highest in the tsetse trapped in the primary forest (7%), and decreased progressively towards the fallow plots (1.8%). There were more young tsetse (less than 40-days-old) in the primary and secondary forests, whereas the Lantana thicket and fallow land had older flies (more than 40-days-old). Possible explanations of these observations are discussed.

Five types of haemocytes were identified in Poecilocerus pictus (Fab.) and their ultrastructural details and differential counts were studied. The types identified are the prohaemocyte, plasmatocyte, granular haemocyte, oenocytoid and coagulocyte. In response to the injection of yeast cells into the haemocoel, changes in haemocyte morphology and differential counts occurred. The predominant cell involved in phagocytosis is the plasmatocyte, followed by granular haemocyte.

Studies were conducted with Ugandan isolate of Coelomomyces stegomyiae against mosquito larvae. Aedes aegypti first instar larvae was most susceptible (99.8%) within 6 days, and the fourth instar was least susceptible (44.4%). Culex quinquefasciatus suffered 70% mortality within 10 days. Mortality rates were 92.5% for Culex tigripes, 70% for Culex duttoni, 89.5% for Aedes africanus, 89.9% for Anopheles gambiase and 97.3% for Aedes simpsoni. There was no infection when two species of the predatory mosquito Toxorhynchites were exposed to infection. A few adults emerging from an infected larval population were found infected when dissected. Other mosquitoes that pupated died and the pupae were found infected. Infected females were produced by 19.2% of the fresh pupae exposed. The importance of the results in biological control is discussed.

A millet farm was divided into five treatment plots of three replicates. The population of the grasshoppers was assessed by flushing and the percentage leaf damage on the millet was estimated by visual grading of the defoliated area. Weeding discouraged oviposition and reduced the vegetative shelter and the population of the grasshoppers. The unweeded plots had high levels of defoliation and low grain yield of millet relative to the weeded plots. Oedaleus spp were the most numerous grasshoppers and probably caused the greatest damage on pearl millet. The common weeds on the farm were Brachiaria xantholeuca, Cenchrus biflorus, Ipomoea vagans and Mitracarpus scaber.

Larval dispersal and establishment of Chilo partellus (Swinhoe) was studied on different maize cultivar combinations at the whorl stage. Dispersal was increased 2-fold when the infested cultivar ICZ2-CM (resistant) was surrounded by the more susceptible Inbred A, and decreased when Inbred A plants were surrounded by ICZ2-CM. A negative relationship (r = 0.89) was found between the proportions of larvae establishing on infested plants and those unaccounted for. The influence of a cultivar on increased larval dispersal could be exploited in resistance breeding strategies. The possible role of such an effect in pest management strategies is discussed.

A comparison was made of the relative abundance of three species of black-fly pupae colonising three natural substrates in the River Assob, in central Nigeria. Simulium hargreavesi, S. squamosum and S. vorax preferred trailing roots, whereas S. cervicomutum, S. unicomutum and S. impukane preferred dead leaves and to a lesser extent, rocks.

In order to see whether this was a preference between cylindrical and flat surfaces, polythene strips were compared with polythene strings and a smooth surface was compared with a rough one. Results are presented for the three most abundant species S. squamosum, S. hargreavesi and S. cervicomutum. All markedly avoided the rough string. S. squamosum and S. hargreavesi preferred smooth strings, whereas S. cervicomutum had no significant preference between smooth strips and strings (although slightly preferring strips). These findings are discussed in relation to natural habitats and sampling bias.