Food consumption and utilization of a bivoltine silkworm hybrid was studied to understand the efficiency of food conversion into larval body, cocoon and cocoon shell during the life cycle. The ingesta, digesta, excreta, reference ratio, mean daily food ingested and digested in different larval instars were recorded. All these parameters differed from one larval instar to another. The AD and ECI were inversely correlated with the larval age. The ECI and ECD for body, cocoon and cocoon shell were 23.63, 17.59, 9.496 and 55.12, 46.65 and 25.23% respectively. Ingesta and digesta required to produce a gram body weight, progressively increased from first to fifth instar. Ingesta and digesta for one gram body, cocoon and cocoon shell production were 4.402, 5.762, 10.649 g and 1.840, 2.184 and 4.047 g respectively.

Gas Liquid Chromatography was used to obtain profiles of cuticular hydrocarbons from single larvae of two species belonging to the Anopheles gambiae complex: A. gambiae and A. arabiensis. By applying discriminant analysis of hydrocarbons it was possible to separate the two populations with a 95% success rate.

The same analysis was used to achieve an average of 94% segregation among their strains. This analysis does not require preservation of specimen by liquid nitrogen or refrigeration and further identification by other procedures can be carried out on the specimens after cuticular hydrocarbon analysis. More importantly the technique permits analysis of single rather than pooled specimens used by earlier investigators.

The larval critical weight (Lcw) in the spotted stem borer, Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae) was 54.6 ± 1.0 mg for average sized male and female final instar larvae and was 63 and 39% of the larval maximum weight (Lmw) of males and females, respectively. There was a consistent decrease in weight from Lmw to pupal weight of 35% in both males and females over successive generations of rearing two laboratory populations. The adult weight was consistently about 37 and 22% lower than the pupal weight for males and females, respectively. During starvation, 25% of the final instar larvae produced a supernumerary moult. A positive correlation was derived between female pupal weight and fecundity. The results were similar to those derived from a study on the progeny of a wild population. A model representing the various fresh weight changes in relation to the Lmw has been suggested for this species. The model is similar to that proposed for other Lepidoptera. The results of this study are largely consistent with those carried out on other species of Lepidoptera and underline the value of using stable standards in assessing the quality of laboratory reared insects.

The photoperiodic regimes [24L, 13L 11D (natural condition), 18L6D, 12L12D, 6L18D and 24D] played a vital role on nucleic acid, protein content of fat body and larval-pupal characters of silkworm, Bombyx mori. Prolonged larval duration with a significant increase in weight of the larvae, silkgland, cocoon, pupa and shell was noted in the larvae exposed to 24L period. A significant positive correlation (r = 0.97, P < 0.01) between larval weight and egg production was noted. The DNA, RNA and protein contents increased at 24L over that of 13L11D group as well as other photicregimes.

A survey of planthopper and leafhopper assemblages and insect predators was conducted in the rice fields of Kaluvanchikudi in Batticaloa District and Kohabana and Central Camp in Amparai District during the dry (yala) season in 1989. Nilaparvata lugens (Stål) was the predominant planthopper species in these rice fields; Sogatella furcifera (Horvath) comprised less than 10% of the sample in any field. The leafhopper species collected included Nephotettix nigropictus (Stål), Nephotettix virescens (Distant), Recilia dorsalis (Motschulsky), and Cofana (= Tettigella) spectra (Distant). Nephotettix species were predominant in Kaluvanchikudi and Kohabana, while R. dorsalis was dominant in Central Camp. Insect predators included the mirid, Cyrtorhinus lividipennis Reuter, an anthocorid, Onus tantillus (Motschulsky) and two coccinellids, Harmonia octomaculata (Fabricius) and Micrapsis discolor (Fabricius). Application of furadan granules reduced the planthopper and leafhopper populations drastically, but did not appreciably reduce the insect predator population.

Studies were commenced to collect and identify the phlebotomine sandflies found in Nairobi. These studies were also aimed at determining their numbers as well as assessing the effects of seasonal changes on the sandfly population. Four trapping methods, namely, light traps, sticky traps, aspiration and human bait were employed. Eight species and one undescribed species were recorded over a period of 6 months. The identified species included Phlebotomus guggisbergi (Kirk and Lewis), P. rodhaini (Parrot), Sergentomyia adleri (Theodor), S. harveyi (Heisch, Guggisberg and Teesdale) and S. bedfordi (Newstead) and an undescribed species. Most of the sandfly species trapped showed seasonal prevalence. The seasonal variation was closely related to the weather conditions. Sandflies were found in termite mounds, animal burrows, caves and dugouts some of which were near human habitations. Termite mounds and animal burrows were the most preferred habitats.

Between 1984 and 1988, a survey of fruit-infesting ceratitid fruitflies was conducted in 11 agricultural districts in Kenya. Samples of up to 18 different fruit crops were examined for infestation. The four species of fruitfly found were Ceratitis capitata, C. rosa (Pterandrus rosa), C. nigra (Trirhithrum coffeae) and C. cosyra (Pardalaspis cosyra). The first three were sympatric infestants of coffee, while the latter was exclusively found in mangoes. In addition, C. rosaalso infested loquat, guava and custard apple. C. capitata infested commercial orange cultivars. This species was predominant in the main arabica coffee growing areas in the central highlands. C. rosa and C. nigra were more widespread, occurring in high proportions in most parts of the country. Generally, the proportions of the three species per coffee sample, and the mean number of each species per kg of coffee, tended to vary considerably over time and space.

The morphology of immature stages of a species of Glyptapanteles was studied. Measurements of the egg, larval and pupal stages are presented. The head sclerites of the three larval instars are also described.

Surveys were conducted in farmers' fields in Zambia during the 1987/88, 1988/89 and 1989/90 cropping seasons, to evaluate the extent of attack on maize by stalk borers and their distribution in some selected maize growing areas in three agroecological regions. Infestation levels varied from season to season. Infestations were low (0.5–13%) in the Southern province: Gwembe Valley and Livingstone in region I and Choma and Kalomo in region II. Infestation levels in other areas ranged from 21–75%. Three species of stalk borers, Busseola fusca, Chilo partellus and Sesamia calamistis were recorded. Their composition and proportion in the complex differed from place to place. C. partellus occurred at an altitude range of 350–1170m, B. fusca occurred at 1032 to >1300m above sea level. B. fusca was the most widely distributed and predominant.

Studies were conducted to compare adult longevity, number of host eggs parasitized and temporal pattern of oviposition of four species of Trichogramma, T. brasiliensis Ashmead, T. chilonis Ishii, T. minutum Riley and T. japonicum Ashmead. Parasitoids were reared on eggs of Corcyra cephalonica St. at 27 ± 2°C and 60 ± 5% r.h. With the exception of T. chilonis, females lived longer than males. The only thelytokous species, T. brasiliensis had the highest longevity and fecundity. However, T. chilonis was observed to lay more than 50% of its eggs on its first day of emergence. Of the four species, T. japonicum exhibited the shortest longevity and lowest fecundity.

The current phenological study in sorghum fields has shown that Busseola fusca is bivoltine in eastern Ethiopia. The first generation begins at the end of April, while early August marks the beginning of the second (Diapause) generation. The second generation passes through the dry season in stalks and stubble as diapause larvae, of which a considerable proportion survive in the stubble until the next crop. The onset of pupation of the diapause larvae is in the middle of April. A progressive increase in the mortality of the larvae of both generations is observed towards the later stages. Five hymenopterous parasitoids, Bracon sesamiae (Cameron), Cotesia (= Apanteles sensu lato) sesamiae (Cameron), Dolichogenidea (= Apanteles sensu lato) sp. near laevigatus, Pediobius furvus (Gahan) and Procerochasmias nigromaculatus (Cameron) and one dipterous parasitoid (Sarcophaga sp.), attacking larvae and pupae of B. fusca at Alemaya, eastern Ethiopia, were identified.

The suitability of some plant products (leaf powders and volatile oils) in protecting cowpea seeds from attack by Callosobruchus maculatus F. during storage was evaluated at a range of 0.5–4 g powder and 0.5–30μ1 for oils. Oils of the plants studied: Lantana camara L., Cymbopogon citratus (DC) Stapf., Eugenia uniflora L. and Lippia adoensis Hoschst. were more potent than their respective powders in reducing or inhibiting oviposition and adult emergence. Effectiveness of the oils as protectants for stored cowpea in decreasing order is: L. adoensis = C. citratus > L. camara and E. uniflora. Only the powdered leaves of E. uniflora and L. adoensis were effective in providing a high level of bruchid control. However, dressing with all the oils and powder of E. uniflora left the seeds fresh at 54 days after treatment. The significance of these findings in protecting cowpea against the storage pest is discussed.

Simple methods for production of all life stages of the banana weevil on its natural diet, banana rhizome and pseudostem are presented. Their effectiveness, labour demands and applicability for different purposes are discussed. The most effective method for the production of eggs, pupae and adults is the utilization of the rhizome part of suckers, whereas larvae are easier to recover from pseudostem. The hatchability of the eggs produced is high.

Postembryonic development and adult emergence of Tribolium castaneum (Herbst) were adversely affected in varying degrees when its larval stage was reared on wheat flour treated separately (at concentrations of 0.001–1.0%) with one of the following commercially available extracts: roots of both sweet flag, Acorus calamus Linn. and Java devil pep per, Rauwolfia serpentina Benth ex Kurz, fruit cortex of soap nut, Sapindus trifoliatus Linn. and gum of Indian Myrrh Commiphora mukul Jacq. A marked decline in the reproductive potential, in terms of female fecundity and egg hatchability was observed when the extracts were applied topically or administered orally through diet.

Bioactivity of Melia azedarach L. was tested against diamondback moth (DBM), Plutella xylostella L. in the laboratory. The adult of DBM laid significantly lesser number (upto 71%) of eggs on the surfaces treated with methanolic extracts of M. azedarach than on those treated with solvent only. When larvae derived from above eggs were reared on fresh food, the mortality in the larval stage was upto 22.8% and that in pupal stage was upto 29.6%. The methanolic extracts also reduced feeding among the larvae significantly, when methanolic extract-treated food was offered to second instar larvae in a different set of experiment, thus, indicating an antifeedant effect.

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.

Ticks and tick-borne diseases of cattle have been and still are a threat to the development of the cattle industry in Zambia. Other control methods of ticks and tick-borne diseases appear to have been used elsewhere in the world in addition to chemical control. In Zambia, chemical control of ticks appears to have been and still remains the most practical method of controlling ticks and tickborne diseases. This paper looks at chemical control from the time it was first used to present and future.

In view of the present environmental awareness, the reduction of spray wastage, which in turn lessens environmental contamination, can be achieved by reducing spray volumes and improvement on spray efficiency through the use of correct ranges of spray droplet sizes. Published data on droplets collected by some insects consistently suggest that the optimum droplet sizes lie below 60 μm.

An experiment was conducted in a wind-tunnel to assess the locust collection efficiency when subjected to a spectrum of droplet size ranges with a view to determine the optimum droplet size.

Locusts were induced to fly in a wind-tunnel and then exposed to spray droplets which were produced by a spinning disc atomiser. Droplets collected on antennae, head, abdomen, legs and wings were sized and counted. The collection efficiency at wind-speeds ranging from 2 m/sec to 6 m/sec was calculated for the different body parts in the droplet size range 10–40, 40–60 and 60–80 μm. The calculated collection efficiency for the 10–40 μm size range was comparatively higher for all locust body parts.

Food production in Africa is declining, while her population is increasing rapidly. Some factors responsible for low food productivity are mentioned; special attention is given to the problem of agricultural pests. The hazards of overuse of pesticides in developed countries are cited to caution farmers in developing countries from getting drawn into a similar situation when attempting to solve pest problems. Integrated pest management (IPM), which aims to increase food productivity and profitability without endangering the environment, is recommended as a sustainable solution to the pesticide problem. The role of biological control agents, i.e., introduction, augmentation and preservation of natural enemies is emphasized. In developing sustainable agriculture through IPM, the importance of incorporating farmers' traditional methods of farming into an IPM package and of identifying farmers' overriding concerns, is recommended as a prerequisite to the acceptability and success of such packages.

Rodent flea control to prevent spread of diseases of which rodents are reservoirs has often been carried out using insecticides. The insecticides are either dusted or sprayed in the entire area affected or placed in baiting boxes sometimes with rodenticides to control rodents and fleas, simultaneously. Systemic insecticides to control rodent fleas though found efficient, easy to apply and less hazardous to the environment, have only been demonstrated in the laboratory and field, but have not been commercially available.

It is suggested that using novel pesticide formulation techniques such as microencapsulation, tableting, employing bait attractants and additives and synthesis of metabolites of effective systemic insecticide could lead to the use of baits containing systemic insecticide to control rodents and fleas simultaneously and avoid undue expenses and hazards.