Chromosomal inversion polymorphism was investigated in samples of Anopheles gambiae sensu lato collected from different localities of Tanzania. An. merus was found monomorphic, while two widespread inversion polymorphisms were recorded in both An. gambiae sensu stricto (2Rb/+ and 2La/+) and An. arabiensis (2Rb/+ and 3Ra/+). Two additional polymorphic inversions (2 Rbr and 2Rq), generally associated, were observed in An. arabiensis from the Rift Valley. Observed karyotype frequencies were in agreement with those expected according to the Hardy-Weinberg equilibrium suggesting conditions of panmixia in both An. gambiae s.s. and An. arabiensis in the studied areas.

An artificial diet was developed for mass rearing of the spotted bollworm Earias vittella (Fabricius) in environmentally controlled conditions (27±1°C, 65±5% R. H. and 16:8 h scoto/photophase). The ingredients for 1 l of diet consisted of soybean (Glycine max) flour (60.0 g), chickpea (Cicer arietinum var. kabuli) flour (58.0 g), wheatgerm (16.0 g), dried yeast powder (16.0 g), casein (8.0 g), l-ascorbic acid (2.4 g), cholesterol (0.4 g), methyl-p-hydroxybenzoate (0.4 g), sorbic acid (2.4 g), streptomycin sulphate (0.4 g), agar–agar (16.0 g) and distilled water (820 ml). The artificial diet developed showed a higher development index (3.58) and a higher survival rate (83.4%) compared to the most preferred natural food (okra pods), for which these parameters were 3.09 and 65.0%, respectively. All the ingredients of the diet are easily available and inexpensive. The cost of 1 l of the diet, on which 400 larvae can be reared, is approximately US$ 2.00.

Several Vigna species were used to determine the role of pod trichomes and pod toughness in the resistance of cowpea to feeding damage by the coreid bug Clavigralla tomentosicollis Stal. The scanning electron microscopy study revealed the presence of glandular and non-glandular trichomes on the pod wall of all test genotypes. The cultivated genotypes TVu 1890, TVu 3354 and IT84S-2246 of the V. unguiculata ssp. unguiculata showed significantly lower (P<0.05) densities of glandular trichomes than accessions of the wild Vigna species (TVnu 72, TVnu 151, and TVnu 707). All pods were similar with respect to the density and length of non-glandular trichomes. The two wild accessions TVnu 151 and TVnu 707 of the V. unguiculata ssp. dekindtiana had low pod, strength similar to that of the susceptible genotype IT84S-2246, and also showed high seed damage levels comparable to that of this susceptible genotype. These accessions of the subspecies dekindtiana contrasted with the wild and resistant accession TVnu 72 of the V. vexillata species which suffered minor seed damage in spite of its low pod strength. The association between high pod strength and low seed damage was found only in the two cultivated genotypes TVu 1890 and TVu 3354. Our results suggest that tough pod wall and high density of glandular trichomes can be combined to achieve enhanced resistance to C. tomentosicollis in cultivated Vigna genotypes.

After field screening local germplasm for stem-borer (Chilo partellus, Swin.) resistance for four seasons in two years we identified two sources of resistance, Katumani and Kitale. A cross between them performed better than either of the parents. When exotic lines from CIMMYT, Mexico, reported to be resistant to South and Central American stem-borers were screened at Mbita Point Field Station, to test and confirm their resistance to East African stem-borers, a number of them were found to be resistant to Chilo. It was also noted that the level of their resistance was higher and more broadly based than the local source. This shows that the source of origin is always full of genetic variability. This finding now suggests that a cross between the local and exotic sources should offer a wide scope in the multiple resistance or the multiline approach towards pest management.

Responses of tsetse Glossina morsitans morsitans and Glossina pallidipes (Diptera: Glossinidae) to host-derived phenolic kairomones were investigated using a wind tunnel. Activation behaviour of G. m. morsitans depended on the mixture of the phenols but not on the dose or ratio of the blend used. Up wind orientation behaviour and actual contact with the odour source depended on both the phenolic mixture and on the ratio of the phenols in the blend. In the present studies, a 4:1 blend of 4-cresol and 3-n-propylphenol, respectively, consistently induced more of the flies to fly upwind and contact the odour source as compared to any other combination of the phenols or even when these two crucial phenols were mixed in a ratio of 9:1; the ratio in which they are found in a typical sample of buffalo urine.

Comparison of the responses of the two species indicate that significantly fewer G. m. morsitans fly upwind and contact the odour source on stimulation with a blend of 4-cresol and 3-n-propylphenol as compared to G. pallidipes. This may explain why phenols only produce small improvements in the catches of G. m. morsitans as compared to G. pallidipes.

The simple wind tunnel developed, not only provides a useful tool for rapidly screening candidate attractants, but also a means to investigate how various compounds alone or in various combinations affect tsetse behaviour.

In field conditions in South Australia hatching of eggs of Ectropis excursaria showed a morning and an afternoon peak. In the laboratory, hatching coincided with “lights-on” stimulus at 20°C, 10:14 and 12:12 L:D. Increase or decrease of temperature by 5°C shifted the start of hatching to late scotophase while increasing photoperiod shifted a substantial proportion of hatching to later in photophase. Survival of first instars was linearly related to saturation-deficit of the atmosphere.

Studies were conducted in farmer's field, Lambwe School of the Deaf, and Mbita Point Field Station of ICIPE (ICIPE-Mbita) in western Kenya during the long rains of 2001 and 2002 to assess the impact of a diversionary stemborer management strategy on the pest's predators. Treatments consisted of a maize monocrop (control) and an intercrop of maize and desmodium, Desmodium uncinatum Jacq., with Napier grass, Pennisetum purpureum (Schumach), as trap crop around the field (‘push-pull’) in the farmer's field and Lambwe School of the Deaf. Sudan grass, Sorghum vulgare sudanense (Pers.), was used in place of Napier on the station. A combination of sticky traps, direct observation and hand-collection methods were employed. Predator groups encountered included 12 families from 7 insect orders and 4 families from one arachnid order, with most of the foregoing represented in both maize monocrop and ‘push-pull’ plots. A Cheilomenes sp. and Chrysopa sp. were, however, recovered from ‘push-pull’ plots only. Ants, earwigs and spiders were the main predators encountered. Both overall and individual group populations of these predators as well as ant diversity were significantly higher in ‘push-pull’ than monocrop plots in all the sites during the vegetative, flowering and mature maize growth stages (P < 0.05, t-test). The results thus indicate a numerical enhancement of stemborer predators by use of this habitat management system.

Plotting the movement of air through typical tsetse habitats in Zimbabwe revealed that it is liable to change direction by over 90° within a few metres. In winds of < 1 m/sec, there was a negative correlation between windspeed and the wind's tendency to meander, whether in thick bush or out in the open. And at the mean windspeed of wet season mopane woodland (0.3 m/sec), the wind changed direction by c. 15°/sec. Accordingly, host odour does not move downwind in simple trajectories that tsetse flies could easily follow. Even 5 m from a source, odour (modelled with smoke) approached a notional tsetse fly for a quarter of the time from >90° away from the true source direction. Also, air turbulence at common tsetse resting sites generates much nonsense information about the “true” direction of any odour-bearing wind. The suggested answer to how tsetse manage to find distant, invisible hosts, in spite of this confusing information from the wind, is that they progress by a biased random walk which is the outcome of their upwind anemotactic responses to odour-bearing wind and the proportion of the time for which the wind does blow in the “correct” direction. Computer simulation shows that this might work in principle.

Aqueous neem seed kernels extracts (NSKE) were used to treat flea-infested goats in Morogoro, Tanzania to determine their efficacy for flea control. Mean population densities of the insects were significantly lower in the treated goats compared to their untreated counterparts (P < 0.05). It was concluded that NSKE has potential in controlling livestock fleas, but further studies are needed to determine the active principals against fleas and their mode of action.

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.

During sporadic outbreaks of S. exempta, population densities sometimes reach extremely high numbers. Monitoring at one such outbreak revealed that a considerable synchrony exists in the developmental processes of such populations, so that at times up to 97% of the population is represented by only one stage of development. Heavy pupal mortality with symptoms of a cytoplasmic virus infection was noted. Flight behaviour of emerging adults revealed observable differences in the flight activity of the moths. Although a great majority of the emerging moths flew away from the area, some stayed back. Eggs layed by the latter produced a second brood but, due to a more or less total depletion of the food source, this subsequent brood did not survive in any appreciable numbers and finally died out.

Eight desi chickpea genotypes of mid-maturity group were screened by using an open-field screening technique. The genotypes ICC-3137, K-850 and ICC-1403 were found to be more susceptible than the others. More eggs were laid and more larvae were recorded on more susceptible genotypes. A low amount of acidity in the leaf extracts of genotypes was found to be associated with susceptibility to gram pod borer, Heliothis armigera (Hubner).

Insect growth regulating properties of petroleum ether extracts of 10 indigenous plants were tested against Culex pipiens fatigans (Wied) and Musca domestica nebulo (Fabr) by continuous exposure and topical application methods. Out of the 10 plants, Acorus calamus and Azadirachta indica demonstrated insect growth regulatory (IGR) activity against C. p. fatigans and also against M. d. nebulo. There was IGR activity, but this was observed only when these extracts were used in higher concentration.

Three years work at Mtwapa Research Station summarises the fluctuation of Chilo spp. and Sesamia spp. Chilo partellus has been been shown to be just as important as C. orichalcociliellus nearer the coast, but Sesamia calamistis becomes important towards the second growing season.

The loss caused by these borers to maize plants in the field has been estimated to be high when no chemical treatment is applied, but such a loss varies with the intensity of infestation. Control of the borers by cultural methods relies on planting maize at the onset of rains. Selected chemical treatment at the appropriate time reduces the loss by about 20%.

Behavioural and electrophysiological (EAG) studies were undertaken to determine the olfactory selectivity of the antennae of Glossina morsitans morsitans Westwood and Glossina pallidipes Austen to phenolic kairomones. Responses of both species to 3-alkylphenols increased as the alkyl chain increased from one carbon atom to three, while the opposite trend was observed with 4-alkylphenols. These results indicated that 4-cresol and 3-n-propylphenol are the most stimulatory of the two respective groups of phenols. However, comparison of the responses indicated differences in the sensitivities of the chemoreceptor systems of the two species. Hence different compositions of the phenols may be required to best attract these species. Probable interactions of the phenols with the binding sites on the receptor surface are discussed.

The influence of resistance or susceptibility of certain maize genotypes on Chilo partellus colonization was studied. The aspects studied were: oviposition in relation to date of planting, plant age and certain morphological and biochemical characteristics. The pattern of oviposition was similar among the maize genotypes and among the different planting dates. However, the intensity of oviposition differed among the maize genotypes and also with plant age. Plants in the whorl stage of development were the most preferred for oviposition. On the whorl-stage plants, ca 92% of all the eggs were deposited on the lower leaves (1–4 from the ground). As the lower leaves senesced with plant age, the upper leaves were selected for oviposition. On all leaves, the lower surfaces were more preferred. The plant characters that appeared to influence oviposition included plant exudates (as the moth diet) and leaf surface trichomes. The quality of exudates from the different genotypes appeared to influence moth fecundity and longevity, while the trichomes appeared to influence the selection of oviposition sites. The possibility of interactions between these factors and oviposition is discussed.

A polytrophic ovariole of the fleshfly, Sarcophaga tibialis Macquart, is composed of two successively maturing egg chambers, each consisting of an oocyte, an interconnected cluster of 15 nurse cells, and an enveloping layer of follicle cells. The oocyte is established at the posterior end of the egg chamber. Nurse cell differentiation is characterized by nucleolar multiplication. At 25°C the first egg generation took approximately 8 days to develop. During this period, the growth rate of the egg chamber increased with time. A dramatic increase occurred during days 4–6, and was associated with the formation of large intercellular spaces between the follicle cells as well as an accumulation of numerous yolk globules. Completion of egg-chamber development was marked by the degeneration of the cluster of nurse cells and that of follicle cells.

The relationship between abundance of the lepidopteran borers Helicoverpa armigera Hubner and Maruca vitrata (Geyer) and damage and yield loss in short-duration pigeonpeas was studied in two multilocation trials in 1995–1996 and 1996–1997 rainy seasons at four locations in India: Patancheru (Andhra Pradesh), Akola (Maharashtra), Sardarkrishi Nagar (Gujarat) and Vamban (Tamil Nadu). Larval populations of Helicoverpa armigera (Hubner) and Maruca vitrata (Geyer) were correlated with pod damage and grain yields. Significant correlation of location, years and genotype on insect population, level of damage and grain yield was obtained. The effect of plant type on lepidopteran pod damage was also observed. The relationships between pod damage, yield and larval population of Helicoverpa and Maruca are discussed.

The damage threshold of the green spider mite, Mononychellus tanajoa (Bondar) on cassava was determined in the greenhouse using four levels of mite infestation namely: 5, 10, 15 and 20 adult mites per cassava plant. Cassava cuttings were planted in plastic buckets in the greenhouse. The plants were artificially infested at 10 weeks old after planting.

Visible symptoms of mite damage appeared on cassava leaves at 4 weeks after infestation and at this period, the average number of mites was found to be eight mites per leaf. The mean number of active stages of M. tanajoa (larvae, nymphs and adults) was highest at the infestation level of 20 mites per plant, followed by that of 15, 10 and 5, in that order. The mean number of eggs was also highest at the infestation level of 20 mites per plant.

Two types of failures of attack by the top borer, Scirpophaga excerptalis Wlk., and their relation to sugarcane resistance to deadheart formation were studied in 164 genotypes of sugarcane for three years at two locations, viz., Karnal (Haryana State) and Chakia (Bihar State) in India. Attacks were unsuccessful either because of failure of neonate larvae in the mid-rib to reach the spindle (Type 1) or failure of older larvae in the spindle to reach the meristem (Type 2). Type 1 failure was frequent (19.2 to 26.7 %) while Type 2 was rare (2.9 to 5.1 %) among the genotypes. Larval dispersal and mortality were influenced by several factors related or unrelated to resistance and occurred concurrently in the same genotypes. This led to variation in larval mortality even among genotypes with the same levels of Type 1 failure. Those genotypes (Co 1223, Co 1224, E 276, Co 7224, Co 745, E 128, Co 62235, E 132, E 50, CoS 767 and CoJ 67) that had high scores of both Type 1 failure (14 to 18) and larval mortality (13 to 17) had the lowest percentages of deadhearts (11.8 to 24.4%).

Type 2 failure was not related to resistance; the highly resistant genotypes, Co 1223, Co 1224, E 276, Co 62235, E 132, CoS 767 and F133, showed no Type 2 failure. Furthermore, genotypes IA 3017 and Co 7322 which had the highest Type 2 failure scores of 9 and 12 respectively, had 61 and 36% deadhearts respectively. It is concluded that Type 2 failure may be caused by larval mortality in the spindles due to diseases and/or asphyxiation by accumulated rain water.