The biosystematics of species in the Cotesia flavipes complex is reviewed with reference to studies conducted on their morphology, morphometrics, enzyme electrophoresis and hybridisation. A survey of 5 morphological characters scored from 17 populations indicated that the scuto-scutellar sulcus and the rugosity on the propodeum could be used to separate the species. The shape of the male genitalia was valid for separating the populations of C. flavipes from those of C. sesamiae and C. chilonis. Canonical variate analysis separated the complex into three distinct clusters with populations from Africa together, populations from Asia and the neotropics forming a second cluster, and material from China and Japan forming the third cluster. Electrophoretic studies showed that esterase, glucosephosphate isomerase, hexokinase, sorbital dehydrogenase and phosphogluconate dehydrogenase, among others, had fixed alelles and could be used to distinguish the species. Cladistic analysis of the allozyme data indicated that allopatric populations currently included in C. flavipes may not be a monophyletic group. Interspecific crosses revealed that males of C. sesamiae could mate with females of C. chilonis and produce viable females.

Laboratory experiments using a glass tube arena were conducted to determine the effects of aggressive behaviour of the stemborer, Chilo partellus Swinhoe (Lepidoptera: Pyralidae), on oviposition success and mortality of the parasitoid, Cotesia flavipes Cameron (Hymenoptera: Braconidae). On contacting unparasitised hosts, female parasitoids rapidly oviposited and then retreated from the experimental arena. Hosts exhibited no aggressive behaviour prior to oviposition. However, soon after being attacked, host larvae became more aggressive, spitting at and biting the parasitoids. When Co. flavipes females were introduced toward the head of the stemborer, the parasitoids stung the host near the head and were frequently bitten and killed by the hosts. Parasitoids that were introduced to the host from the posterior end of the abdomen, stung the abdomen and were often able to escape from the host without being bitten. Regardless of whether parasitoids were introduced near the head or the abdomen, they were more often killed by older hosts than younger hosts. Parasitised hosts were more aggressive than unparasitised hosts one hour after the initial parasitisation, but not after 24 hours. Larval saliva of Chilo partellus was found to reduce survival of adult female parasitoids. The aggressive behaviour of Ch. partellus was not effective as a self-defense against Co. flavipes, but is likely to be an important mortality factor of Co. flavipes in nature.

Studies were conducted on the spatial distribution of the sugarcane shoot borer, Chilo infuscatellus Snellen. Distribution was aggregated and described by the negative binomial model with a fixed mean size. Aggregated distribution probably resulted from environmental heterogeneity. The five quadrants of the field, i.e. north, south, east, west and central did not differ significantly in borer population. The optimum sample size, based on Iwao's formula, was 126 plants of 6 tillers each. The relevance of these findings to the management of C. infuscatellus is discussed.

Progeny production and sex ratios of the parasitoids Cotesia sesamiae (Cameron) (Hymenoptera: Braconidae) and its exotic congener Cotesia flavipes Cameron (Hymenoptera: Braconidae) emerging from three species of field-collected stemborers were compared. There were no significant differences in numbers of progeny of the two parasitoids from the African stemborers, Chilo orichalcociliellus (Strand) (Lepidoptera: Pyralidae) and Sesamia calamistis Hampson (Lepidoptera: Noctuidae). Cotesia flavipes produced more progeny than C. sesamiae on large larvae of its coevolved Asian host, Chilo partellus (Swinhoe). No significant differences in the number of parasitoid progeny were observed for different-sized Ch. orichalcociliellus or S. calamistis larvae. These data suggest that under field conditions, Co. flavipes may be superior to Co. sesamiae as a parasitoid of its co-evolved host, Ch. partellus.

Bioassays were carried out in Petri dishes with body washings of larvae, male and female moths and scale extract of Corcyra cephalonica St. in hexane to observe their kairomonal effect on Trichogramma brasiliensis (Ashmead) and T. japonicum Ashmead. The mean parasitoid activity index (PAI) and mean parasitisation were recorded. Trichogramma brasiliensis and T. japonicum recorded the highest mean parasitisation in the eggs treated with scale extract. Mean parasitisation recorded by T. japonicum in cards treated with female moth and male moth body washings were considerably lower than the corresponding values for T. brasiliensis. Both the parasitoids recorded significantly lower levels of parasitisation in cards treated with larval body washings. Gas chromatographs of host body washings / extract recorded a large number of similar hydrocarbons in the body washings of male and female moths and the scale extract. Pentadecane, heneicosane, eicosane, tetracosane, pentacosane and hexacosane were recorded in scale extracts. Female moth body washings recorded the presence of eicosane, tetracosane and pentacosane while heneicosane and eicosane were indicated in the male moth body washings.

Field trials in Kenya demonstrated that the forage grass, Sorghum vulgare sudanense (Sudan grass) attracted greater oviposition by stemborers than cultivated maize, resulting in significant increase in maize yield. On the other hand, the non-host forage plant, Melinis minutiflora (molasses grass), when inter-cropped with maize, repelled gravid stemborer females from ovipositing on maize, resulting in significant reduction in stemborer infestation. Using these trap- and repellent gramineous plants, a novel pest management approach based on a ‘push-pull’ or stimulo-deterrent diversionary strategy is being developed where stemborers are repelled from the food crop and are simultaneously attracted to a discard or trap crop. The plant composition and permanence of habitat surrounding maize fields also influence the abundance of natural enemies that invade agroecosy stems once a pest population is present. It may be advantageous to promote the growth of native Gramineae and other wild plants which minimise, or even suppress, population growth of pests during non-cropping seasons, but still provide a suitable habitat for natural enemies.

Haemolymph from the locusts Schistocerca gregaria and Locusta migratoria contains humoral factors such as lectin and phenoloxidase system. In vitro studies demonstrated that phenoloxidase system can be activated by LPS, laminarin, Malamoeba locustae cysts, trypsin and methanol. Haemolymph showed agglutination activity for mammalian erythrocytes and protozoa (M. locustae, Leishmania major and Trypanosoma brucei). A purified lectin was isolated from haemolymph by affinity chromatography. Analysis by SDS-PAGE gave a single band at 80 kD while on native PAGE, it gave a single band at 650 kD. Inhibitors of the two humoral factors were investigated. Lectin activity was inhibited by nitrophenyl a α D-galactopyranoside in both cases and by lectin antiserum. Inhibitors of the phenoloxidase system were found in plasma. Prospects for use of such inhibitors are discussed. They could be incorporated in biopesticide formulations in such a way that they could depress locust immune reaction and stimulate biocide activity.

Acute toxicity tests were conducted to determine the biological effects of partially purified extracts of four different plants on the juveniles of Culex quinquefasciatus. The active ethyl acetate extract of Solarium suratense leaf produced a 24h LC50 of between 23.53 ppm for the second instars and 46.04 ppm for the third instars. This was followed by the defatted methanol fraction of Abrus precatorius seed coat extract with the LC50 values ranging from 59.82 ppm for the second instar to 77.34 ppm for the third instar. The petroleum ether fraction of Solatium trilobatum and the ethyl acetate fraction of Lencas aspera were less toxic to the larvae. The active fractions of the plant extracts disrupted moulting and metamorphosis, induced malformation, extended the larval duration and inhibited adult emergence. At concentrations of less than 37.64 ppm, they inhibited emergence of 50% of the larvae. The insecticidal activity of these extracts persisted for up to four days.

Two field experiments were conducted over two seasons to assess the effect of resistance levels of sorghum varieties on follow-up generations of Chilo partellus. Sorghum varieties, released by the Southern African Development Community/International Crops Research Institute for the Semi-Arid Tropics (SADC/ICRISAT) through the Sorghum and Millet Improvement Program (SMIP) in the southern African region, were evaluated for their ability to provide for larvae to complete development in stalks and emerge as moths. Plants were naturally infested by C. partellus. The number of moth exit holes per stem was used to calculate survival of larvae to the adult stage. A moth production index was calculated to estimate the role of each sorghum variety in area-wide suppression of stemborer abundance. Between 97,500 and 213,125 moths per hectare emerged from the different sorghum varieties in trial 1 while between 0 and 77,500 emerged per hectare in trail 2. Resistant sorghum varieties may help suppress pest population build-up and be of considerable value in development of IPM systems for resource-poor farmers.

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.

The effects of various concentrations of Neem Azal-T and Neem Azal-T/S as natural insecticides on the biology and percentage mortality of adult Aphis craccwora Koch were studied under laboratory conditions. Both extracts had an aphicidal effect against the adults and significantly decreased their fecundities and longevities. Addition of synergists such as ethyl oleate, sesame oil and dimethyl sulphoxide (DMSO) improved the aphicidal effects of both insecticides. The biological activity of Neem Azal-T/S only could be enhanced with suitable additives as they adversely affected the fecundity and longevity in comparison to the extract alone. Addition of CaCO3 to the above extracts had no clear effect on either neem seed extract formulation.

Recent studies on the identification and evaluation of the millet stemborer Contesta ignefusalis female sex pheromone have shown that pheromone technology is promising as a management component. A review of research shows that an effective pheromone trap has been developed and successfully tested in eight countries in West Africa, through the West and Central African Millet Research Network (WCAMRN/ROCAFREMI). A regional wide-scale stemborer monitoring network has been developed and is being implemented. Studies on mass trapping and mating disruption indicate that the two techniques have much potential in C. ignefusalis management. Prospects for the implementation of pheromone technology to manage C. ignefusalis in the context of an IPM scheme are discussed.

Studies were carried out from 1990 to 1993 to identify termite species associated with cocoa and coffee in Ghana. Ten genera/species, belonging to the families Termitidae and Rhinotermitidae, were recorded from cocoa and coffee trees aged from 6 to 36 months. The commonest was Ancistrotermes sp., followed by Amitermes sp., Microtermes subhyalinus, Microtermes sp. and Nasutitermes sp. Others were Macrotermes bellicosus, Pseudacanthotermes sp., Cubitermes sp., Schedorhinotermes putorius and Coptotermes sp. All species except M. bellicosus, Pseudacanthotermes sp. and Cubitermes sp. caused damage to cocoa and/or coffee. The shade tree, Gliricidia sp. was attacked by Pseudacanthotermes sp. whereas Macrotermes bellicosus and Cubitermes sp. were harmless. The relative abundance of these termites is discussed.