Various trap designs were tested in Congo in order to assess their cost vs. effectiveness for the control of human trypanosomiasis vectors. These preliminary trials indicated that it is necessary to compare the different trap designs in several African countries. Furthermore, studies on the attractiveness of locally available fabrics must be carried out in order to make traps taking into account the sizes of locally available fabrics. At present, the ‘Vavoua’ trap is sail the most efficient but further investigations need to be carried out to reduce the cost of new traps without significantly affecting their efficiency. The ‘black/blue/black’ screen can be used successfully by rural communities in Congo for tsetse control.

The biological activity against Boophilus microplus of extracts of the berries, bark, leaves and twigs of Pimenta dioica was examined and compared with that of eugenol, methyl eugenol and four commercial acaricides, namely dimethoate, farnesyl methyl ether, carbaryl and diazinon. The berry essential oil was more effective at inhibiting oviposition and causing mortality of the ticks than all the extracts, the commercial acaricides and methyl eugenol. At a dose of 1.0 mg/g it was 33, 12, 6, and 3 times as effective in inhibiting oviposition as the non-polar extracts of the leaves, bark, twigs and berries, respectively. The potency of the berry essential oil is attributable to eugenol, a phenyl propanoid derivative, which accounts for over 65% of the oil content.

Tannin extracts of two sorghum, Sorghum bicolor (L.) Moench. cultivars, BKS5 and BTX 623 were assessed for their bioactivity against the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) and the angoumois grain moth, Sitotroga cerealella (Olivier) (Lepidoptera: Gelechiidae), in whole wheat flour pellets, and against the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) in whole wheat flour at three treatment levels. The number of adult progeny was reduced and number of days to emergence increased by tannins extracted from both sorghum cultivars at all treatment levels. However, the effects were not significant in all cases. In a short-term (25 days) feeding test using S.oryzae adults, the presence of sorghum tannins from cv. BKS 5 in the pellets significantly reduced feeding by the insects.

In laboratory studies on the nymphal and adult performance of the cotton stainers Dysdercus cardinalis and D. fasciatus (Pyrrhocoridae: Hemiptera) on seeds of five different host plants, two categories of hosts with significantly (P < 0.05) different biological effects were identified. Gossypium hirsutum L., Ceiba pentrandra Gaertn and Sterculia rhynchocarpa (K. Schum) were found to be suitable hosts (category A) while Adansonia digitata L. and Abutilon mauritianum (Jacq. Medic.) were unsuitable (category B). Category A hosts that grew in the wild appear to serve as perennial breeding reservoirs for the cotton stainers and thus play a significant role in initiating and perpetuating their infestation of adjacent cotton crops. The converse appears to be true for category B hosts, whose long-term effect would be to gradually decrease the population of the cotton stainers.

Three field trials were conducted to determine the effect of various levels of resistance of South African sorghum hybrids on follow-up generations of Busseola fusca Fuller (Lepidoptera: Noctuidae) and Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae). In one trial, plants were artificially infested with B. fusca larvae while the other trials were subjected to natural infestation of C. partellus. The number of damaged internodes and moth exit holes per stem were used to calculate a relative survival index which estimates the survival of larvae to the adult stage. A moth production index was calculated to estimate the role of a hybrid in area-wide suppression of stemborer populations. In the B. fusca trial, resistant and susceptible experimental hybrids produced 40 000 and 113 000 moths per hectare respectively, compared to 80 000 and 83 000 moths per hectare produced by the commercial hybrids. Larval damage to whorl leaves, assessed on a 1 to 9 scale, indicated leaf-feeding resistance of commercial hybrids to B. fusca ranging from susceptible to intermediate. Yield losses suffered by the hybrids in the B. fusca trial were greater than that suffered by a susceptible experimental hybrid, indicating susceptibility of South African hybrids to B. fusca. The evaluation of sorghum varieties for their potential to reduce stemborer populations should indicate their usefulness in integrated pest management systems.

Isolates of Beauveria bassiana (Balsamo) Vuillemin, Paecilomyces farinosus (Holm ex SF Gray) Brown and Smith and Verticillium lecanii (Zimmermann) Viegas were evaluated for their pathogenicity to adults, eggs, first and third instars of silverleaf whitefly, Bemisia argentifolli (Bellows and Perring) (Homoptera: Aleyrodidae). Conidial dilutions were prepared in 0.05% Tween® and leaves treated by immersion in these suspensions. Assessments of nymphal infection were made 2, 3, 5, 7, and 10 days post-treatment. Infection rates in adults and eggs were made 14 days post-treatment. All isolates were pathogenic to nymphs and adults. None of the isolates were pathogenic to eggs. Isolates L3444 (P. farinosus) and L3009 (B. bassiana) were the most pathogenic to first instars and adults with LC50 and LC90 values of 7.3 × 104 and 3.1 × 106 conidia/ml, and 1.3 × 106 and 1.0 × 107 conidia/ml, respectively. Isolate FR20 (V. lecanii) was the most pathogenic to third instars with LC50 and LC90 values of 4.8 × 103 and 7.4 × 105 conidia/ml, respectively. Results imply that L3444 and L3009 are the most efficient isolates, based on their pathogenicity to first instars and adults. Results are discussed in relation to using fungi for management of silverleaf whitefly in greenhouses.

The influence of three cultivars of Sorghum bicolor (L.) on the activity of the fungus Metarhizium anisopliae on the stemborer Chilo partellus was investigated in the field and laboratory. Fungal activity in the field varied with the plant cultivar and the inoculum concentration. Larvae fed on different cultivars and inoculated with the fungus in the laboratory did not vary in their susceptibility to the pathogen. However, time to 50% mortality (LT50) of the larvae was shorter in cultivar IS 1044 than in cultivars ICS 3 and ICS 4. Compatibility of the fungus with cultivars is therefore an important consideration when using fungi for the biological control of stemborers.

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.

Tick populations were monitored between October 1991 and September 1992 at monthly intervals on 10 Boran (Bos indicus) heifers at Didtuyura ranch, Yabelo district, Ethiopia. Twelve different tick species in four genera were identified from a total of 16 026 specimens collected. Of all the ticks collected, Rhipicephalus spp. constituted 84.7%, Amblyomma spp. 9.9%, Boophilus spp. 4.8% and Hyalomma spp. 0.24%. The ventral parts of cattle were found to be the most favoured feeding sites for most of the ticks collected. The size ranges of the standard ticks collected were 4–8 mm; 9–16 mm; 4–8 mm and 8–13 mm for R. pulchellus, A. variegatum, B. decoloratus and A. gemma, respectively, while their respective male to female sex ratios were 2:1; 3.2:1; 1:5.4 and 2.6:1. Packed cell volume (PCV) values of blood samples taken from 600 cattle were monitored monthly during the study period. There was a reduction in PCV during the dry season of the year but generally the values were within the normal range of 32–40%. The parasites causing anaplasmosis, babesiosis and theileriosis (T. mutans) were detected by microscopic examination of blood smears and serologically (ELISA) at seroprevalence rates of 94.68%, 77.19% and 30.9% respectively.

Agromyzidae populations occurring in legumes in Kenya were tested for speciation at host-type level and at the species level using discriminant analysis. Measurements were taken of various morphological characters of five populations of Chromatomyia horticola from five host plants and of seven male and female agromyzid species. The ratio of the proximal to the distal part of the wing vein, (M3+4) provided the best discrimination for five host populations of C. horticola; the species was separated into two distinct groups by this character. Females of Ophiomyia spencerella and O. phaseoli were distinct. However, overlap existed in male O. spencerella, O. phaseoli and C. horticola. In addition, there was overlap in female O. phaseoli, Tropicomyia vigneae and Liriomyza trifolii. The best discrimination in the male populations was obtained using the ratio of the proximal to the distal part of wing vein (M3+4). In the female populations, the best discriminating character was hind tibia length.

Starch gel electrophoresis was used to compare eight loci in six enzymatic systems of 17 samples of the groundnut seed-beetle, Caryedon serratus (Ol.) (Coleoptera: Bruchidae) bred on five different host-plant species: Arachis hypogaea, Bauhinia rufescens, Cassia sieberiana, Piliostigma reticulatum and Tamarindus indica. The rate of polymorphism was 44.8%. The average genetic diversity (Hw) was 0.184. Allozyme variability analysis indicated that seed-beetles associated with P. reticulatum and groundnut, Arachis hypogaea were genetically similar, whereas other samples clustered according to their host plant species. Geographical distances less than 400 km were not decisive for the genetic structuring of samples associated with a given host plant.

In laboratory experiments, pupae of the uzi fly, Exorista sorbillans Wiedemann (Diptera: Tachinidae), an endoparasitoid of the silkworm, Bombyx mori L. (Lepidoptera: Bombycidae) were subjected to UV-irradiation for different durations. Upon adult emergence, irradiated and control flies were crossed in all possible combinations and allowed to parasitise healthy silkworms. Adult emergence, fecundity and longevity of the resulting progeny were recorded. Progeny of irradiated E. sorbillans showed significantly reduced adult emergence, oviposicion period and hatchability. The reduction in fecundity was negatively correlated with the duration of exposure to UV radiation. The longevity of uzi flies of both the sexes was also significantly reduced.