A study was conducted at Katumani, Kiboko and Ithookwe, in the semi-arid Eastern Province of Kenya for four seasons (short rains 1996-long rains 1998), to confirm the major stemborers of maize, and to introduce and monitor the colonisation of Cotesia flavipes Cameron (Hymenoptera: Braconidae) in these stemborers. About 6750 adults of Cotesia flavipes were released at each site, from ‘release stations’, starting one week after plant emergence and repeated fortnightly up to harvest. Pre-release parasitism of the stemborers was determined, for two seasons prior to release of Co. flavipes, during the season of release and one season after the release of this parasitoid. Parasitism was assessed from developmental stages of the stemborers recovered through destructive sampling of 100 plants, starting one week after plant emergence. This was repeated weekly at Katumani, and fortnightly at Kiboko and Ithookwe until harvest. The stemborers recovered from maize were Chilo partellus, Sesamia calamistis, Cryptophlebia leucotreta and Busseola fusca in descending order of abundance, with Ch. partellus being the most widespread stemborer. Cotesia flavipes parasitised and successfully colonised Ch. partellus and S. calamistis in the three sites during the season of release and one season post-release of the parasitoid. Parasitism by Co. flavipes ranged from 7.14–25.80 %. The colonisation rate of Co. flavipes in the two major stemborers in the semi-arid Eastern Province of Kenya suggests the high potential of this parasitoid in regulating populations of stemborers that attack maize in this region.

Spraying of diflubenzuron at 100 g a.i./ha after spike emergence (10–15 cm from flag leaf) was more effective against early larval stages of millet spike worm, Heliocheilus (=Raghuva) albipunctella De Joannis, than spraying the crop at female flowering or at the milky grain stage.

Insects have evolved a potpourri of mechanisms for manipulating the allelochemicals that fortify their preferred host plants. A concatenation of physiological and biochemical events frequently follows the ingestion of a toxic natural product and can eventuate in a variety of fates for the compound. A particular allelochemical may be absorbed, metabolized, and sequestered, whereas the fates of concomitant natural products may be very different. Some compounds may be directly excreted in the faeces and their concentration will thus mirror that in the plant. In other cases, selective absorption and sequestration combine to biomagnify minor constituents so that the concentration of these sequestered compounds in insect tissues diners drastically from their concentrations in the host plants.

The acridid Romalea guttata is utilized in this paper as a paradigmatic insect which eclectically processes ingested allelochemicals from a wide range of host plants. This generalist herbivore is eminently suitable as a model because it feeds on plants containing a veritable pharmacopoeia of toxic compounds. The proven sequestrative potential of its defensive glands further qualifies R. guttata as an excellent candidate for determining the fates of toxic phytochemicals. An analysis of this insect's processing strategies for the compounds ingested after feeding on catnip (Nepeta cataria) reveals that for R. guttata variety is the spice of herbivorous life. The results of this investigation persuasively demonstrate that each insect species—and the phytochemical mixture that it ingests—must be regarded as a unique evolutionary case that constitutes a distinctively idiosyncratic phenomenon.

In intertropical Africa, various haematophagous Diptera are considered responsible for the maintenance and spread of cases of cattle trypanosomiasis in regions where tsetse flies are absent. In comparing early observations with the results of two recent tsetse control campaigns, this paper raises the question of whether the role of machanical vectors is as important as that normally attributed to them, and stresses the insufficiency and impressive nature of available information on this important epidemiological problem, which requires much more intensive research.

The reasons for assessing crop losses due to pests of cereals are reviewed; for making decisions in pest management based on costs and benefits, for allocating resources on the most important pests, and as a guide to how yield is lost. Crop yield is seen as a balanced system, with inputs and output. The methods of quantifying pest attack, measuring losses and the difficulties met are discussed: the interaction of losses, interplot interference, mixed crops, loss distribution and crop compensation. Surveys of loss are described, with examples.

The geographical distribution and the biology of the different species of tsetse fly are closely connected with the vegetation. Any modification in the vegetation cover may therefore change, in one way or another, the dynamics of tsetse populations and, consequently, influence the transmission of trypanosamiasis. Irrigation and rural development programmes which often drastically change the natural vegetation of vast areas will therefore result in major changes in the incidence, epidemiology and epizootiology of trypanosomiasis.

Only very limited studies have been carried out on this important problem and it is very difficult, if not impossible, to make a review of this subject as the data available are very fragmentary and often relate to specific situations.

The main purpose of this article is not only to review the data and information available at present, but also to identify and stress our lack of knowledge and the need for further research.

The problems created by establishment of irrigation and rural development programmes, industrial scale plantations, irrigated cultivations, livestock rearing centres are highlighted without neglecting the sociological and medical aspects of population transfers connected with these development programmes.

The conclusions attempt to identify the research which should be carried out in the field and propose some recommendations drawing attention to both the health services and to those responsible for planning and establishing irrigation and rural development programmes.

The population and distribution pattern of the black parlatoria scale, Parlatorio zizyphus (Lucas) have been investigated. This scale had two annual peaks of abundance in September and May. It passed through three annual generations, the first in September–October, the second in March–April and the third in June–July on grape fruit trees. The build up of insect population on different zones of grape fruit trees in different seasons of the year was studied. The insect distribution of different insect items were significantly affected at different heights and directions of the trees. The highest population tended to be accumulated on the lower and middle shady zones of the trees in different seasons. With regard to directions the central core of the tree harboured the highest population followed by the west direction and the lowest population was accumulated on the north or south direction in the fall and spring. In summer, the highest population settled on the south direction in contrast to the east or north directions, which harboured the lowest population. The mode of insect distribution is discussed in correlation with the environmental conditions.

Loss estimates for wheat insects in Africa and Asia have not received adequate attention. However, in PDR of Yemen, pests including insects, diseases, weeds and birds can cause 10™70% loss of wheat crop. Aphids are considered to be the major insect pests of wheat in the country. A survey of indigenous natural enemies has shown that they may contribute to overall aphid control. Sowing date experiments have shown that sowing in November led to higher yields and lower insect infestation than sowing in October and December. The insecticides tested achieved a significant control of aphids and higher yields when compared with unsprayed plots. A single application of malathion or dimethoate before mid-January was recommended for chemical control.

Once a minor pest, the pea aphid, Acyrthosiphon pisum (Harris) has recently become a major pest of field pea (Pisum sativum L.) in Ethiopia, particularly in the northwestern region. To determine the population dynamics of the pest, field experiments were carried out at Adet and Zema in northwestern Ethiopia in 1994, 1995 and 1996. Treatments were planting dates at 15-day intervals in May, June and July and sampling was carried out weekly until crop maturity. Combined ANOVA, over seasons and locations, showed significant effects of sowing dates, seasons and locations. Pea aphid populations increased and decreased with delay in planting at Adet and Zema, respectively. At Adet, peaks of weekly counts of aphid numbers were observed in August and seasonal totals of aphids on individual planting dates increased as planting was delayed. At Zema, peaks of weekly counts of aphid numbers were observed in mid-July (1996), late August and early September (1995) and mid-September (1994); peas planted on June 16 gave the lowest seasonal totals of aphids. Natural enemies (predators and parasitoids) appeared in considerable numbers in 1996 and these tended to increase as planting date was delayed. For most planting dates and years, weekly aphid populations showed positive correlation with maximum temperature, and negative correlation with minimum temperature and relative humidity. Increasing maximum temperature promoted the buildup of aphid populations while increased minimum temperature, rainfall and relative humidity suppressed it. Grain yield increased and decreased as planting date was delayed at Adet and Zema, respectively. From these results, it is recommended that planting of field peas should take place from mid- to late June at Adet and during the first week of June at Zema to obtain higher yields; by doing so a mean of 0.32 t/ha and 0.50 t/ha higher yield was obtained, respectively.

The pupal parasitoid Xanthopimpla stemmator Thunberg oviposits in the pupae of the spotted stalk borer (or sorghum stem borer) Chilo partellus (Swin). The adult parasitoid emerges from the pupal case, killing it in the process. Ten mated females of the parasitoid had an average longevity of 30 days (maximum 37 days and minimum 22 days). The number of progeny produced ranged from 71 to 115, with an average of 84.5. The male:female sex-ratio of their progeny averaged 1.14:1. The maximum mean progeny production per day (mx) was 1.9. The innate capacity for increase was 0.131 per female per day; and the population multiplied 43.43 times in the generation time of 28.78 days.

Electrophoretic studies of Guatemalan blackflies, Simulium ochraceum, the main vector of Central American onchocerciasis, were performed using isozyme patterns. A total of six larval and adult populations originating from four localities (a non-endemic area, Finca La Ruda, a low-endemic area, Finca Rincon, and two high-endemic areas, Finca Brote and Finca Recreo) were analyzed. The enzymes examined were adenylate kinase (AK), alkaline phosphatase (ALP), glucose phosphate isomerase (GPI), hexokinase (HK), isocitrate dehydrogenase (IDH), leucine aminopeptidase (LAP), malic enzyme (ME), and phosphoglucomutase (PGM). Of these, six enzymes, AK, ALP, HK, IDH, LAP, and ME showed no variation either within or among populations. GPI and PGM were found to be highly polymorphic in all of the six populations. χ2-test for fit to Hardy-Weinberg equilibrium (HWE) revealed that the distribution of the phenotypes of the two polymorphic enzymes was not significantly out of the HWE. A verages of values of proportion of polymorphic loci (P) and heterozygosity per individual (H) of the six populations were 0.234 and 0.084, respectively, each of which was similar to the values reported for different groups of organisms (Nei, 1975). Genetic diversity among populations was measured by FST and GST and both parameters showed that the non-endemic population from the Finca La Ruda (Dl) was greatly differentiated genetically from the other five populations. Estimates of genetic distance (Nei, 1975) showed that the Dl population was furthest from the other populations.

Paper discusses five substantive issues affecting farmer participation (FP) in the development of integrated tick management (ITM). These are the concepts, methods, incentives for and constraints to farmer participation (FP), and finally, case study material illustrating how FP has contributed to the research and development of integrated tick management.

Seasonal incidence of the sorghum earhead bug, Calocoris angustatus Lethierry, was studied by sowing the crop once in 10 days, throughout the year during 1978 and 1979, as well as by sowing it at fortnightly intervals from early “kharif” to late “rabi” during 1979. The bug was found throughout the year except for a few weeks during March, April and May. The milky stage of the earhead was the most preferred stage compared to pre-flowering, a third flowering, flowering and ripening stages. The adults dominated during pre-flowering and a third flowering stages whereas nymphs dominated during milky and ripening stages. The computed seasonal indices were higher during August (230), September (222), October (224) and January (215) which coincided with blooming and milky stage of sorghum in general fields. Correlation studies between the bug population at the milky stage and maximum temperature indicated negative and significant (r = -0.2967) relationship, and positive and significant (r = +0.2727) relationship with relative humidity. Low incidence of bugs was observed on the crop sown during June.

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?

The effects of gamma irradiation from a 60Co-source on Glossina palpalis palpalis (Robineau-Desvoidy) were established in laboratory tests. Dose-response data indicated that fecundity was reduced by about 95% following exposure of late stage puparia or young adults to 11–13 krad in air and 15–18 krad in a nitrogen atmosphere. None of the treatments had a detectable influence on the viability, mating behaviour, inseminating capability or competitiveness of the adult males.

When irradiated males were combined in varying ratios with untreated males and females, increasing numbers of sterile males resulted in a considerable reduction in pregnancy stages beyond the egg stage, an increasing proportion of parous females with an empty uterus due to expulsion of a dead embryo after embryonic arrest or due to ovary blockage and an increasing percentage of females with a degenerating egg in utero.

Remating of inseminated females with fertile males during the period when most of them had emptied their uterus (day 14–20) after embryonic arrest, had no noticeable effect on the sterility rate.

A most important consequence of recurring embryonic death was a detectable imbalance between intra-uterine and ovarian development. Some aberrations can be used as additional criteria for monitoring the effectiveness of sterile males released in the field.

Females irradiated in the pupal or adult stage displayed a normal receptivity and insemination rate and survived distinctly longer than untreated controls. Moreover, they built up abnormally abundant fat bodies and showed multiple mating scars (restricted to the palpalis group species) and completely atrophied ovaries.

It is postulated that the release-recapture and examination of the reproductive tract of irradiated females during an advanced stage of sterile release vector control operations would give evidence of mating that could expose the existence of relic wild populations, particularly when the natural tsetse population has been reduced to, levels below the threshold detectable by conventional techniques.

Nauclea diderrichii (De Wild and Th. Dür.) (common name Kusia and trade name, Opepe) is an evergreen tree found throughout the tropical rainforests of West Africa. It is heavily exploited for its timber and listed as vulnerable on the IUCN Red List of Threatened Species. The shoot borer Orygmophora mediofoveata Hamps, which attacks the nursery stage, has hampered attempts to establish N. diderrichii plantations in Ghana. This study examined the potential of four insecticides to protect N. diderrichii seedlings from O. mediofoveata attack and damage. Four insecticides–Pyrinex (chlorpyrifos), Dursban (chlorpyrifos), Cerox (dimethoate) and Golan (acetamiprid)–were applied to four-month-old N. diderrichii seedlings growing in full sunlight and under shade (80% of normal light), to evaluate their effects on incidence of attack, survival, severity of damage and growth. Insecticide treatment and light conditions had variable effects on the damage and growth of the seedlings after six months of evaluation. Seedling survival was not significantly influenced by the insecticide treatment. Percent survival of insecticide-treated seedlings did not differ significantly from that of control seedlings in full sun; however, under shade survival of treated seedlings was significantly higher than control seedlings. Nonetheless, control seedlings in full sun had higher survival (92.5%) than those under shade (62.5%). Insecticide-treated seedlings in full sun had lower incidence of shoot borer attack than those under shade. In full sun, dieback incidence following shoot borer attack was significantly lower for insecticide-treated than control seedlings. Growth in height and girth of seedlings was influenced positively by both insecticide and light, with girth especially being significantly lower under shade conditions. Currently, N. diderrichii seedlings are typically raised under shade; however, this study shows that raising seedlings in full sun with insecticide application could result in faster and better growth.

Results of research on biology of Thinophilus guineensis Coul. et Neg. (Diptera, Dolichopodidae) confirm the importance of predaceous feeding behaviour of some other species of Dolichopodidae such as Medetera fisch, Hydrophorus fallen, Sciapus fatten, Diaphorus meigen, etc. Larval mortality of some pests (mosquitoes, blackflies, scolytes, etc.) reach 83 to 99%.

These species, because of their extraodinary ubiquity and their biocoenotical importance, could well be used in biological control programmes of vectors of pathogens affecting man and other animals or pests in agroforestry.

Heliothis armigera (Hubner) completed five generations in the laboratory, as well as in the field, in a year. The first generation was completed from the first week of December to the fourth week of February, the second generation from the second week of February to first week of April. The third generation from third week of August passing through the extreme summer, the fourth generation during monsoon period and the fifth last generation from the third week of September to the fourth week of November. The seasonal variation in generation time is largely due to extreme variations in ecological factors, temperature (10–45°C), photoperiod (10–14 hr), relative humidity (15–95%) and rainfall. These factors also affect the percentage of pupation, emergence and fecundity of the female moths. Males outnumbered the females in the first, second and fifth generation. The females lived longer than males in all generations.

Mites are known to live in a diverse number of habitats, but only recently have they been collected in large quantities from the tropical canopies, where they have a diverse feeding habit.

We studied the canopy oribatid mites from five localities of Mexican oak species. Foggings with a natural pyrethrum in aqueous solution were employed to obtain the arthropods living on the canopy of the oaks. Specimens were taken from two collections made in February and August of 1997.

The total number of mites obtained with the two foggings was 5824 specimens. Most of them (95%) were collected during the rainy season and only about 5% during the dry season. The Mesostigmata were represented by 194 specimens, Prostigmata by 849 and the Cryptostigmata (or oribatids) were by far the most abundant, with a total of 4781 specimens. This group represents only 3% of total mite abundance during the dry season and 97% during the rainy season.

Quercus crassipes harboured more oribatid mites during the dry and rainy seasons, and the most important mites in abundance and frequency were Camisia sp., Phauloppia sp. and Scapheremaeus sp.