Population of Spodoptera litura F. were monitored through pheromone-baited traps during the rainy season 1988 and 1989 in groundnut fields in relation to oviposition on leaves. Four peaks of adult catches were recorded. First and second peaks were smaller and caused no threat to crop. Third peak was observed at the pegging and pod-initiation stage during first week of September and coincided with the greatest oviposition on leaves. The fourth peak was greatest and occurred between 40th and 43rd standard week. However, no oviposition was recorded on groundnut during this period. The moths possibly dispersed and/or migrated to other areas with crops at an appropriate stage of susceptibility.

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.

A regional programme, involving seven national programmes and three international agencies, has been launched in East Africa to promote research on the biological control of cassava green mite, Mononychellus tanajoa (Bondar) sensu lato. The organization and objectives of the programme are described and outline results of the first 2 years of work are reported. Trials to assess losses due to mites were carried out at 10 sites, using acaricides to protect split plots of two to five varieties in each trial; at 6 sites, significant losses of tuber yield were recorded on one or more varieties. Surveys of indigenous natural enemies indicated that the predator complex is similar throughout the region and does not provide adequate green mite control. Two Neotropical phytoseiid predators have so far been introduced for local evaluation. One of these, Neoseiulus idaeus, has been released at 12 sites in three countries; recoveries were made at several sites, but no impact on the pest population was detectable. Plans for further collaborative work are discussed.

The relative resistance of rice varieties to Maliarpha separatella was studied during 1981 and 1982 long rain seasons. The observations covered the laying of egg masses, tiller infestation, incidence of “whiteheads” and, in some cases, the grain yield.

The results indicated that the varieties BG 34™8 and BG 90™2 received the highest egg masses per plot which apparently caused “whiteheads”. The remaining 10 varieties only indicated moderate response. The 1982 long rain season under no control and carbofuran 5G application regimes showed reduced tiller infestation only in BG 90™2 and Basmati 217. The five tested varieties did not show any marked difference in tiller infestation under the two regimes. Hence, BG 90™2 and Basmati 217 showed some susceptibility of M. separatella, while the rest of the varieties remained moderately resistant.

Moth population varied according to the growth stages of the rice crop in the field, with the peak occurring during the booting to maturation stages.

Two new cost-effective trap designs for capturing arthropod flower visitors are described. Small flower visitors such as Thysanoptera and Diptera, hardly noticeable during direct flower observations, were dominant in trap catches. These trapping techniques combined with direct observations allow a more comprehensive picture of the flower visitors.

The potential of plant genetics in the overall context of integrated pest control could be viewed simply as the potential of plant resistance in pest management. Genetic resistance in plants is one of the most effective and economic means of controlling plant pests. Resistant plants are the first line defence against pests. Successes in breeding for pest resistance depend upon the sound knowledge of the plant genes controlling resistance to pests.

Recent report on the existence of two nonatlelic and independent genes, Rac1 and Rac2 in cowpea cultivars ICV 10 and TVu 310, and ICV 11 and ICV 12, respectively, from the ICIPE has broadened the scope of cowpea breeding against aphid biotypes. Use of biotechnology as a plant breeding tool in transferring resistance genes into agronomically suitable cultivars appears to hold good promise for the future.

We selected 50 crystal (Cry) toxins specific to lepidopteran insects. Phylogenetic relationships of whole toxins as well as individual domains revealed that Cry1Jb and Cry1Ac are distantly placed but related to reduced cross-resistance in Helicoverpa armigera. Multiple alignments of Cry1Jb and Cry1Ac amino acid sequences showed significant differences in the composition and length of the loops of domains II and III. This was further confirmed by the superpositioning of 3D structures. cry1Jb and cry1Ac genes cloned in expression vectors were overexpressed in Escherichia coli Castellani & Chalmers, and proteins were harvested. Insect bioassays revealed that the wild-type Cry1Jb and Cry1Ac proteins showed differential specificity to H. armigera (Hübner), Spodoptera litura (Fab.) and Earias vittella F. Chimeric genes were constructed by exchanging the domains between cry1Jb and cry1Ac and overexpressed in BL21(DE3). Substitution of domain III of Cry1Jb with that of Cry1Ac enhanced its activity against H. armigera 7.8-fold. Bioassay of the parental and chimeric toxins against S. litura revealed no activity even at the discriminative dose of 100 μg/ml, but a significant difference in growth was observed. The present results, along with previous domain swapping experiments, suggest that protein engineering not only reveals the mechanism by which endotoxins work, but also generates novel toxins with enhanced toxicity/broader specificity.

A preliminary survey was conducted in coastal Kenya to assess the hosts of economically important tick species (Acari: Ixodidae) of domestic animals, as part of a training course for tick scientists from African research institutions. Ticks were collected from domestic animals in Kilifi and Kwale districts.

Eight tick species, namely Amblyomma variegatum, Boophilus decoloratus, B. microplus, R. appendiculatiis, R. evertsi evertsi, R. pulchellus, R. simus and A. gemma were identified. Further, more comprehensive surveys on the hosts, distribution and ecology of ticks of economic importance are recommended.

A keen appreciation of the types and mechanisms of resistance must be attained in order to fully understand and utilize resistant cultivars as effective tools in today's pest management schemes. A historical account of plant resistance terminology is presented. Resistance can be classified as to intensities: immunity; high, moderate and low resistance; or types of resistance: vertical or horizontal resistance. The mechanisms of resistance include: non-preference, antibiosis and tolerance. Examples of the effects of both non-preference and antibiosis resistance on insect numbers are given.

The design and construction of the Nitse trap are described. The materials required are: royal blue cotton, black cotton, mosquito netting, brass pipe, metal rods and galvanised wire. The cutting and joining of the various parts to produce the trap and the method of placement are also described. Finally a rough estimate of the cost of the trap is given.

The effect of exposing 1, 3 and 5 days old pupae to 10°C for periods of 7, 14, 21 and 28 days on the emergence, pre-oviposition and fecundity of Cryptolaemus montrouzieri Mulsant was studied. The emergence was delayed significantly when 1 and 3 days old pupae were subjected to 10°C for 28 days when compared to 5 days old pupae. The initiation of oviposition was delayed with the prolongation of holding time. The fecundity of females emerging from 5 days old pupae subjected to 10°C for 21 days was found to be significantly higher than in any other treatment.

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.

Intensive investigations of genetic variation within and among populations of the whitefly, Bemisia tabaci, are under way in Israel and in Colombia. A polymorphic esterase (EST), which seems to be controlled by a Mendelian locus, has two alleles in sufficiently high frequencies to be useful as a genetic marker. The analysis of more than 10,000 individual adult whiteflies shows genetic differences among localities in the frequencies of the fast (F) and slow (S) alleles. These differences seem to be related to the intensity of insecticide use against the whitefly. The frequency of F is high in unsprayed areas and in control laboratory populations, but is close to zero in heavily-sprayed agricultural areas. The frequency of Fon cotton in agricultural areas is high in winter and spring, but decreases dramatically in the summer (coincidental with the onset of pest-control activities on cotton). A similar temporal pattern on untreated Lantana may be due to migration of adults from agricultural fields. There was no indication of differentiation of populations on different host plants. In Colombia, the difference in EST patterns in different States are very pronounced, suggestive of geographical races. Small samples from Florida, California and Kenya indicate that B. tabaci in different countries may be genetically distinct.

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.

The already known benzoquinone, embelin (mixed with rapanone), and two new benzoquinones, myrsinone and myrsinaquinone, were isolated from the Myrsinaceae plant, Rapanea melanphloes (L), Mez. All the three compounds showed antifeedant activity when bioassayed on nymphs of the desert locust, Schistocerca gregaria (Forsk). They also inhibited growth of second-instar larvae of mosquito Aedes aegypti at low doses, and had acute lethal effects at higher doses.

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.

The effect of artificial infestation of the spiralling whitefly, Aleurodicus dispersus Russell at 0, 1, 2, 3, 4 and 5 pairs on caged potted pepper (Capsicum spp.) plants at 2 weeks after planting (WAP), representing the nursery stage, and 6 WAP, representing the field stage, was studied in a screen house. Increasing insect density resulted in a corresponding increase in damage to the leaves, measured as leaf drop. Yield reduction was inversely proportional to the whitefly population, with highly significant correlation coefficients. For instance, yield reductions were 8.8 and 36.5% with 1 and 5 pairs of adult whitefly respectively at 2 WAP, and 7.5 and 32.1% with 1 and 5 pairs respectively at 6 WAP. The chlorophyll, sugar, ash, protein and crude fibre contents of the leaves decreased with increases in level of infestation, although infestation had no significant effect on the nutrient contents of the fruits. The significant impact of A dispersus on vegetative growth, yields and chemical contents of leaves confirm it as an economic pest of pepper in Nigeria.

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%.

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.

A significant increase in mortality was observed in Glossina morsitans morsitans maintained for approx. 45 days on rabbits immunized with tsetse or bovinetrypsin. Tsetse and bovine trypsin were observed to cross-react when tested with an immunodiffusion technique. A significant decrease in fecundity was observed in flies fed on bovine trypsin-immunized rabbits. Pupae collected from flies maintained on rabbits immunized with tsetse and bovine trypsin were significantly lighter. A significant number of flies maintained on rabbit immunized with thoracic muscles, gut bacteria and bovine trypsin had permanently laterally extended wings.