The impact of a new design of permethrin-impregnated wall cloth (“Mbu” (mosquito) cloth) on mosquito populations was assessed in Marigat area of Baringo District, Kenya. The cloth was fitted in 2000 houses. Mosquito relative density, species composition and the proportion of blood-fed females before and during the use of the Mbu cloth were monitored by hand catch, exit trap and CDC light trap catches. The common mosquito species were Culex quinquefasciatus, Mansonia uniformis, Anopheles gambiae sensu lato and An. funestus. A statistically significant decline in the mosquito population was observed following the introduction of the cloth. The decline was particularly high during the first and second six month impregnation cycles when it ranged between 43 and 94% indoors. C. quinquefasciatus was less affected by the cloth than other species, while M. uniformis apparently avoided treated houses. An. gambiae s.I. and An. funestus were collected in extremely low numbers during the post-treatment period. The Mbu cloth and other permethrin impregnated wall-hanging fabrics constitute a novel way Of controlling mosquitoes and malaria in rural communities.

Life tables of Earias vittella reared on Abelmoschus esculentus L., (okra) Gossypium hirsutum L., (cotton) and Abutilon indicum G. Den. in the laboratory at 27 ± 1°C were constructed. The pest population increased at the rate of 0.124, 0.106 and 0.082 females/female/day, respectively on these seeds. A significant correlation between fecundity and body weight of females raised on these seeds was obtained. The shorter generation time and higher intrinsic rate of population increase on okra seeds shortened the population doubling time of E. vittella to 5.67 days, while the doubling time was 6.64 or 9.00 days on cotton or A. indicum seeds. In a larval period of 16–17 days E. vittella consumed okra, cotton and A. indicum seeds at the rate of 463. 6,493.3 and 382.8 J/g/day. E. vittella fed on okra displayed the highest efficiencies of assimilation (74%), gross (49%) and net production (66%). The efficiencies were comparatively low for the insects fed on A. indicum seeds.

The correct title of the paper by Virendra K. Gupta, published in Vol. 12 No. 1/2/3, pp. 9–18,1991, is as follows:

THE PARASITIC HYMENOPTERA AND BIOLOGICAL CONTROL AND OUR KNOWLEDGE OF THE AFRICAN ICHNEUMONIDAE

Ovlposition and development of the ichneumonid Trathala flavoorbitalis (Cam.) a parasitoid of the brinjal shoot and fruit borer, Leucinodes orbonalis Guen., was investigated. The parasitoid responded to a host larva by inserting its ovipositor (stinging) into the larva, whichever instar (first to fifth) it was. All the first and about 50% of the second instars that were stung and oviposited in, were mutilated and died as a result. Successful parasitization and parasitoid development up to adult emergence occurred in 53% of the third, 57% of the fourth and 41% of the fifth instar host larvae. When given a choice of instars for oviposition, the parasitoid avoided all first instar and most second instar larvae, while third to fifth instars were equally accepted. The total developmental time of the parasitoid was much the same (about 20–24 days) whichever larval instar (second to fifth) was parasitized. The parasitized host at pupation contained different developmental stages of the parasitoid, differing in this respect from most other species of larval-pupal parasitoids.

Earias vittella (Fabricius) feeds on some malvaceous plant species, but has never been reported to attack Thespesia populnea Cav., even though this plant belongs to the same family. The factors responsible for the failure of E. vittella to establish on T. populnea were, therefore, studied. When whole fruits or fruit pericarps of this plant were provided as larval food, larvae failed to develop and none of them pupated. However, on developing seeds of these fruits, larval growth and development were normal and comparable to those of larvae reared on developing seeds of the most favoured host plant, Abelmoschus esculentus Moench. Ether extracts from fruit pericarps exhibited antifeedant and antibiosis activity against this insect. Ether as well as ethanol extracts affected oviposition to some extent. In a choice situation, significantly less eggs were laid on treated than on untreated okra fruits. However, in a no-choice situation most of the eggs were laid on treated okra fruits.

The biological activity of pirimiphos-methyl (20% e.c.) and a chlorpyriphos-methyl/deltamethrin (20/1% e.c.) formulation applied at different concentrations to glass, jute, plywood and mud surfaees against Prostephanus truncatus (Horn) and Sitophilus zeamais (Motsch.), was compared over a period of 18 weeks. The bioassays were conducted at 28°C and 70% r.h., 1, 4, 7, 14 and 18 weeks after treatment. Insect mortality was significantly influenced by the type of surface, the insecticide concentration, the age of the insecticide deposit and the interactions between these factors. P. truncatus was more susceptible to chlorpyriphos-methyl/deltamethrln deposits than S. zeamais. Amongst the different surfaces, glass retained the highest persistence, followed by jute, plywood and mud against P. truncatus. The insecticide deposits on jute were the most effective in controlling S. zeamais.

Restriction endonuclease digestion of genomic DNAs from WHO Leishmania reference strains generates prominent kinetoplast DNA (kDNA) fragments ranging from 0.5–2.0 kb. Following fractionation by agarose gel electrophoresis, these DNA fragments were visualized as distinct bands in gels. Using as parameters the presence or absence of the prominent bands and their size and number, the Leishmania reference strains fell into three distinct genomic groups. These genomic groupings were applied to new Leishmania isolates. DNA analysis, involving restriction endonuclease digestion and Southern blot hybridization with probes generated from the prominent DNA bands of reference strains L. major IC-236 and L. major IC-235, cloned in plasmids, showed significant genetic variation within Leishmania and allowed some distinct isolates to be identified.

The major alkanone constituents of the resin of Commiphora rostrata, 2-decanone and 2-undecanone, and a series of structural analogues were bioassayed for their repellency against the maize weevil, Sitophilus zeamais in olfactometric assays. All the aliphatic ketones and aldehydes showed comparable or greater activity than the synthetic commercial insect repellent N, N-diethyl toluamide (DEET). In the 2-alkanone series the C-8 and C-9 compounds demonstrated significantly higher activity than their shorter- and longer-chained congeners. Analogues differing in the relative positions of the carbonyl group, including aldehydes, showed a variable pattern of repellency. Alkanols appeared to be mildly attractive to the weevil. The results support our previous suggestion that the resin constituents may play an allomonal role in the ecosystem where the plant thrives.

—In order to evaluate the effect of permethrin-treated wall cloth against phlebotomine sandflies, a study lasting 26 months (February 1989 to March 1991) was conducted in Marigat Location of Baringo District, Kenya, an endemic focus of both visceral and cutaneous leishmaniases. In six experimental villages, a total of 2000 houses were fitted with cloth made of cotton and impregnated with permethrin EC 20% at a dosage of 0.5 g/m2 diluted in water. Houses in the two control villages were not fitted with cloths and were located 1.5 km away from the experimental area. Traps made of clear polythene sheeting were coated with castor oil and placed inside houses to collect endophilic sandflies. In the experimental villages, the permethrin-treated wall cloth (called Mbu cloth) reduced the population of sandflies found inside houses by 52–73%. Phlebotomus martini and P. duboscqi, vectors of visceral and cutaneous leishmaniases, were reduced by 76 and 85% respectively. In the experimental villages, highly significant differences were observed between the average numbers of sandflies collected before deployment of the treated wall cloth and those observed after thethird treatment of the cloth. No major sandfly reduction was observed however, in the control villages. There was also evidence of feeding reduction due to the permethrin.

The immature stages, preferred oviposition sites, hatching patterns and egg morphology of two important rice pest species, Leptocorisa oratorius (Fabricius) and L. acuta (Thunberg) (Heteroptera: Alydidae) were described. Species specific differences were found in all these features. These differences may be useful for identification in fields where these pests occur together.

Studies were conducted for the first time on the gregarious endoparasitoid, Apanteles taragamae Viereck (Hymenoptera: Braconidae) to determine its biology on Diaphania indica (Saunders) (Lepidoptera: Pyralidae). The mean number of eggs laid per host was 24.63 and these eggs increased greatly in size before hatching. Larva passes through three instars as determined by the shape and size of the mandibles. Mean development time from egg to adult was 15.6 days at 24.26°C and 80–85% r.h. The mean number of adults emerging from each host was 14.61 and the sex ratio was 1:1.31 (males:females). The mean number of eggs laid by each female was 242.6. Mean adult longevity on 20% honey was 9.30 days for males and 10.70 for females.

A quantitative index of resistance to ticks, which had been derived from results of artificial infestation of East African zebu cattle with a Rusinga Island (Lake Victoria) stock of Rhipicephalus appendiculatus, was tested for consistency using three additional tick stocks—from a laboratory (Muguga), Intona (Trans Mara) and Ukunda (Kenya coast). Results from all the stocks gave similar indices when compared with corresponding values for the Rusinga stock, confirming both the validity of the mathematical function and of the use of any local stock of the tick species for assessing the resistance of cattle to R. appendiculatus.

The effect of resettlement programmes and agricultural development projects on the tsetse population in Gambella were investigated. Adult tsetse were collected using biconical traps and moving vehicle catches. The species collected were Glossina pallidipes, G. fuscipes and G. tachinoides. G. pallidipes was the most frequently encountered species. G. morsitans which were reported to be abundant in the area (Balis and Bergeon, 1968; Hutchinson, 1971; Langridge, 1976) were not collected during the present survey.

About 155,000 ha. of land, formerly reported as tsetse infested, is found to be tsetse free. The natural vegetation is being transformed into farmlands and villages, and the wildlife is being hunted out, remaining only in such areas as Demesaye and Gog forest.

Under such circumstances tsetse hosts may change from wild mammals to man and his domestic animals and outbreaks of nagana and sleeping sickness are likely to occur throughout the region.

Worldwide recognition of ticks and subsequent control experiences in USA, Australia and Africa is summarized. The symposium lecture includes three research challenges: (a) reduce the direct and indirect costs of ticks to African animal agriculture, (b) complete critical research required for an effective African tick control programme in spite of stable or reduced research funding, (c) learn to package and market new technology used in control schemes. Three questions are suggested for industry representatives and researchers to ask one another: (a) Is the new technology practical and affordable? (b) Is animal productivity really improved? (c) Are the schemes responsive to broader environmental and animal health concerns of society?

A number of natural and man-made habitats in Marigat area of Kenya were surveyed for sandflies in 1985/86. Of the 98,573 adult sandflies collected, 2.7 % belonged to the genus Phlebotomus and 97.3% to Sergentomyia. Relative abundance of sandflies of the genus Phlebotomus was four times higher in burrows than in termite hills, while sandflies of the genus Sergentomyia collected from termite hills were twice as numerous as those from burrows. Termite hills had the highest sandfly population compared to other sites, followed by tree holes and animal burrows. Fifteen species were identified, of which five belonged to Phlebotomus and 10 to Sergentomyia. The most abundant and widespread species were Sergentomyia antennatus, S. bedfordi, S. ingrami, Phlebotomus martini, S. schwetzi, S. africanus and P. duboscqi. Sandflies of both genera were present for the greater part of the year. Most species of sandflies decreased in numbers during the dry season. High population densities of sandflies were recorded during the wet period. Correlations between relative abundance of sandfly vectors of leishmaniases and rainfall were positive. However, none of the correlation coefficients was statistically significant.

Animal burrows are major habitats for both P. martini and P. duboscqi, vectors of visceral and cutaneous leishmaniases in Kenya. In burrows, both species were collected throughout the year. The highest relative abundance of P. martini and P. duboscqi was recorded in August and in April, respectively. The lowest relative abundance was observed in july for P. martini and in October for P. duboscqi. In termite mounds, P. martini was present all the year round, but P. duboscqi was absent for the greater part of the year. The highest relative abundance of P. martini was observed in November and April, while that of P. duboscqi was seen in March and April. The lowest relative abundance of P. martini was recorded in July. In termite mounds, P. duboscqi showed a significant positive correlation with rainfall, contrary to P. martini which did not afford any significant correlation with any environmental factor. Rainfall, relative humidity and ambient temperature did not correlate with relative sandfly abundance in animal burrows.

The influence of larval diet, body weight at imago, size of blood-meal and age on the fecundity of Culex quinquefasciatus was investigated. The mean weights of mosquitoes at adult emergence varied significantly with larval diet. Larvae reared on liver diet grew into heavier adults, and produced more eggs than those reared on milk. The volume of blood engorged by the female mosquitoes apparently remains constant during each gonotrophic cycle. However, the number of eggs produced is a function of both the blood-meal size and age of the mosquitoes. These results were discussed in relation to the need for full knowledge of the reproductive potential of this species of filaria vectors.

Several strains of Hyphomycetes fungi were assayed in the laboratory to determine their pathogenicity against second instar Chilo partellus Swinhoe larvae and fifth–sixth instar Busseola fusca Fuller larvae. Pathogenic activity to both stem borers was demonstrated with Beauveria bassiana (Balsamo) Vuillemin and Metarhizium anisopliae (Metschnikoff) Sorokin. B. bassiana isolates caused mortality of 3–100% of mortality in C. partellus larvae, and 30–84% in B.fusca. Strains of M.anisopliae showed a high level of virulence for both insect pests, causing mortality levels of 65–100%. Development of fungal infection appeared to take longer in B. fusca larvae (LT50 of 6.2–13.2 days) than in C. partellus (LT50 of 1.9–5.4 days). B. bassiana isolate ICIPE 4, and M. anisopliae isolates ICIPE 18 and 30, which were effective against both stem borers, outperformed the other pathogens tested. They appear to have potential for use asmicrobial agents in the control of C. partellus and B. fusca.