The effectiveness of Bacillus thuringiensis var. galleriae HD-129 against the moths and egg masses of the cotton leafworm, Spodoptera littoralis, has been demonstrated in laboratory experiments. The longevity and egg production were significantly affected when the moths were fed on a sucrose diet containing 17.2 × 103 IU of the tested formulation/mg or higher rates. At lower concentrations (4.4−8.7 × 103 IU/mg), the females gave normal egg production, but the longevity was adversely affected. Investigations show that a formulation with spores alone affects the egg production and hatching, while a formulation with active crystals alone had no effect on egg production. Sprays of B. thuringiensis combined with sucrose on flowering cotton plants seem to affect the biology of the moths released on it. Egg masses sprayed with B. thuringiensis hatched normally, but the survival of the hatched larvae was reduced when treatment was made shortly before egg hatching. Based on the results obtained, B. thuringiensis showed a promising effect in the control of the moth S. littoralis as well as an ovicide larvicide agent.

Tropical African ticks are found on their hosts throughout the year, but at varying infestation levels. These population changes, for most of the time, have been associated with climatic changes. Their development is inversely related to temperature. Several workers reported that development failed for a number of tick species at temperatures below 15°C, suggesting a possible lower temperature threshold for tick development. The upper development limit for most of the tropical rhipicephalids appear to be 37°C.

Ticks are particularly susceptible to attack during lethargic pre-moulting and the weak post-moulting period. Many biological features enable them, however, to survive especially well. They lay numerous eggs and withstand a comparatively wide temperature and humidity range with greater ease. They survive for months or years without food.

Their degree of host specificity varies from genus to genus or within subgroups of various genera. The requirement of two or more kinds of hosts often with divergent habits, limits their distribution to certain faunal areas.

This paper reviews our current knowledge on development and survival of ixodid ticks under tropical field conditions including some laboratory studies.

In a survey carried out in 1979–1982 in Sudan, 5830 tick immature stages were collected from cattle, sheep and camels and identified. Hyalomma anatolicum anatolicum, Rhipicephalus evertsi and Amblyomma lepidum immatures were feeding on cattle and sheep. Amblyomma variegatum immatures were collected from cattle. H. impeltatum nymphs were found, for the first time, to feed on camels and sheep, while H. dromedarii nymphs were recorded from camels.

Feeding H. a. anatolicum larvae on rabbits, 53.4% of the ticks behaved as three-host feeding cycle.

The sorghum shootfly, Atherigona seccata Rondani, is the main species of Atherigona attacking cultivated and wild species of Sorghum in Africa and Asia. The past 55 years' research on the pest has produced means for its management. The bionomics of A. soccata are well known and are being applied for its cultural control by adjusting planting dates. Natural enemies of the shootfly are few and their biology little known. The systemic insecticide carbofuran as a seed and seed furrow treatment provides effective fly control where the cost-benefit is favorable. Sources of host plant resistance to shootfly have been recognized for about 35 years. Incorporation of this resistance in high yielding varieties through plant breeding should be more rapid now that the mechanisms of resistance and their inheritance, through additive gene action, are better understood. These resistance factors include non-preference for oviposition, antibiosis and recovery through tillering.

The International Red Locust Control Service (IRLCS) was formally established in 1949 with the primary objective of controlling locusts in their outbreak areas, thereby preventing the recurrence of plagues. The name of IRLCS was subsequently changed in 1970 to the International Red Locust Control Organisation for Central and Southern Africa (IRLCO-CSA), but retained the same objectives. Over the years, IRLCO-CSA has experienced changes in membership and locations of its Headquarters and operational centres. Its principle mandate has remained the same even though it has been modified and rationalised from time to time. The organisation carried out investigations that led to the identification of the red locust outbreak areas and the development of various control technologies. Control methods developed from the original physical ones which were laborious and inefficient; to insecticide dusting and baiting; to the spraying by aircraft. In its history of locust control programmes, IRLCO-CSA has used arsenic compounds, BHC, DNOC, dieldrin and fenitrothion as insecticides. The success that IRLCO-CSA has enjoyed in its 50 years history has been thanks to the cooperation of countries in eastern, central and southern Africa which are vulnerable to attack by the red locust, and the international community.

Trials using deltamethrin impregnated odour-baited targets for control of tsetse, have been running in Galana Ranch on the coastal hitherland since 1986. In July 1988, a similar trial was started in Lambwe Valley, Western Kenya. Glossina pallidipes is the sole vector in the valley and is present in very high densities.

In Galana Ranch trial, octenol and acetone are used as odours while in Lambwe Valley, natural cow urine is used in addition to acetone and octenol. Tsetse population densities were assessed weekly for 3 weeks, before deployment of targets and thereafter at monthly intervals. A herd of cattle is used to monitor the effect of the control measures on disease incidence.

On Galana Ranch, the block where the initial trial began has remained free of G. pallidipes for a period of 3 years. In a period of 9 months in the second year of the trial, the berenil index in a herd of cattle was 0.07 in the controlled area compared to 2.5 in the uncontrolled area.

In Lambwe Valley a 99.9% reduction in trap catches has been observed in most parts of the park at the end of the first year. The berenil index in the cattle has dropped from 6.3 to 0 and there is a general improvementin the health of the animals. Observations are continuing at both sites.

Survey and experiments were conducted to investigate the distribution and bionomics of the rice stem-borers in Kenya. Stem-borers collected and identified included: Maliarpha separatella Rag., Diopsis thoracica West, Sesamia calamistis Hmps. and Chilo partellus Swin. Maliarpha separatella were most abundant and infested throughout the crop season, D. thoracica infested during vegetative phase. S. calamistis frequently occurred at the onset of flowering stage toward harvest. C. partellus occurred more frequently in upland than lowland rice and was at low population. Assessment of crop loss caused by M. separatella was carried out under field, caged condition. It was observed that the per cent of empty grains was affected by Maliarpha infestation. Calculated yield loss based on percentage empty grains and number of ‘whiteheads’ was higher than the actual differences between grain weight of uninvested and infested crops.

Studies were conducted on components of resistance to sorghum midge on four resistant (DJ 6514, AF 28, TAM 2566 and IS 15107) and two susceptible (CSH 1 and Swarna) cultivars. Short floral parts, faster rate of grain development and high tannin content of grain were apparently associated with resistance to sorghum midge, Contarinia sorghicola Coq. Genotypic and phenotypic correlations between the factors associated with resistance to sorghum midge were in the same direction (positive or negative) as their association with resistance to this insect. Glume g2, lemma 12, anther and lodicule length, rate of grain development based on dry weight (except oviposition), and tannin content of mature grain showed correlation and path coefficients (direct effects) in the same direction. These characters can serve as a useful criteria to select for resistance to sorghum midge.

Using D2 and canonical cluster analysis, AF 28 was found to be distinct from other sources of midge resistance. However, based on larvae/100 florets, DJ 6514 was also placed distantly from TAM 2566 and IS 15107. Based on egg numbers, adults emerged and grain damage, DJ 6514 was grouped with TAM 2566 and IS 15107. Susceptible hybrid check, CSH 1 was generally placed distantly from the self pollinated susceptible variety, Swarna. These results indicate that the sources of resistance to sorghum midge are diverse, and there is a distinct possibility of increasing the levels and diversity of resistance to this insect.

Glossina tachinoides and G. morsitans submorsitans in Niger and G. morsitans morsitans in Mozambique conform to the general pattern of Glossina resting behaviour in that they rest on the woody parts of the vegetation during the day and on the foliage at night. G. m. submorsitans and G. m. morsitans both prefer low horizontal branches as their main day-resting sites, while G. tachinoides rests mainly on the bases of trunks. G. m. morsitans was found to exhibit a 3-phase pattern of resting behaviour: on foliage at night; low down on trunks for a short period after dawn; and on branches higher up for the remainder of the day. No relationship between temperature or relative humidity on the choice and vertical distribution of night resting sites could be found. For G. tachinoides, the microclimatic conditions of its resting sites were more favourable than ambient conditions during the middle of the day.

The various methods of controlling tick infestation on livestock are reviewed, highlighting their strengths and weaknesses. A framework for developing an IPM approach including socioeconomic considerations for ticks control is proposed. Efforts at practising IPM on ticks are highlighted.

Population studies of the whitefly, Bemisia tabaci, carried out in the field indicated that whiteflies were present in cassava all year round and that there were marked seasonal fluctuations in the population levels. Possible explanations for these fluctuations are discussed. It was found that the interaction of atmospheric temperature and relative humidity was highly correlated (r = 0.924) with the development of the whitefly. Results of the studies suggested that rainfall has an indirect effect on whitefly population. Whether B. tabaci behaves in the same way in mixed cropping system has not yet been established.

A study was carried out for four years in the forest area of Daloa in Côte d'Ivoire to assess the rate of trypanosome infection in tsetse, and thereby the trypanosomiasis infection risk. In different Glossina biotopes, 18,908 Glossina palpalis palpalis were caught with Vavoua traps and were dissected. The most widespread species of trypanosomes infecting the Glossina was Trypanosoma congolense (7.63%) followed by T. vivax (4.50%). Trypanosoma brucei, the trypanosome responsible for animal and human African trypanosomiasis (HAT), was found only in 34 of the tsetse flies collected, and it had a very low infection rate (0.18%). Although infected tsetse flies were captured in all habitats examined, the infection rate was relatively higher along footpaths (0.44%), in farms (0.20%) and around forested water springs (0.27%) compared to the edge of villages (0.06%) and forest borders (0.05%). Among the 34 tsetse flies infected with T. brucei, only 0.05% had parasites exclusively in their salivary glands. Our results suggest that footpaths, plantations of coffee and cocoa and forested water springs are potential biotopes where the risk of infection by T. brucei is most important. The anthropophily of Glossina associated with the high number of parasites in these sites could be the reason for the disease is endemic in Daloa today. In our study, female Glossina were infected more frequently with trypanosomes (0.14%) than males (0.04%) and generally, females lived longer than males. It is likely that the longevity of females, which carry parasites, is the major cause for the endemicity of HAT in this locality.

Recognition of Anopheles mid-gut molecules interacting with the malaria parasite is important as they can potentially be targeted to interrupt the life cycle of the parasite in the mosquito's body. The mid-gut of mosquitoes is covered with the glycocalyx, which is composed of various glycoproteins. Pieces of evidence show that mucin proteins are one of the most frequent ingredients of the glycocalyx. In the present study, we isolated and identified the sequence of mucin from the mid-gut of Anopheles stephensi, Liston and Kazerun strains. Anopheles stephensi mucin (AsMuc) has two central core repeats with the consensus sequence TTTTVAP flanked with a hydrophobic N-terminus and a C-terminus which it seems are both necessary for cell surface expression. To show if this molecule is expressed on the surface of the cell, we cloned AsMuc in a baculovirus vector and tracked the expression of the protein in Sf9 insect cells. Immune assays showed the surface localization of the recombinant mucin. AsMuc expression on the surface of the cell suggests it could be a potential ligand for Plasmodium spp. attachment to the Anopheles mid-gut.

Studies on larval movement, feeding and development of Chilo partellus Swinhoe were carried out at Mbita, Western Kenya. Larval movement away from the plant was observed during the first and third instars. Plants inoculated at the stems recorded greater larval migration compared to those inoculated at the leaf whorls. Larval feeding was greater on IS 18363 than on IS 2146, but growth rate, weight gain and efficiency of conversion into body substances were greater in IS 2146. Thus it seems that varietal susceptibility to damage by C. partellus is different from varietal suitability for growth of the larvae.

Microscopic examination of stem tissues damaged during larval feeding revealed that feeding was mainly restricted to the pith and that the vascular bundles were hardly affected.

To investigate the existence of inter-strain fecundity in the groundnut beetle Careydon serratus, the fecundity and larval survival of crosses of beetle strains from Bauhinia, Cassia, Piliostigma and Tamarindus were studied. The crosses produced viable eggs, but the fertility of beetles mated within strains was significantly higher than that of inter-strain matings, the former being nearly double the latter. Differences in larval mortality between the various crosses were also observed.

Fourth instar larvae of laboratory-reared, Ctenocephalides felts and Xenopsylla. brasiliensis were exposed to 50% neem seed kernel extract (NSKE) for periods varying from 30 min to 24 hr. Mortality of larvae was observed from exposure periods of 2 hr and above in both species. At 24 hr exposure, 95.3% and 94.7% of C.felis and X. brasiliensis respectively were killed. LT50s were approximately 6 and 10.5 hr for C.felis and X. brasiliensis respectively. It was generally concluded that neem seed kernel extract was potentially larvicidal against the two flea species and that it could be effectively used for controlling the insects by properly dusting the latter's breeding sites with appropriate concentrations of the extract.

We studied the mite complex—consisting of Tetranychus cinnabarinus (Boisduval), T. urticae (Koch) and Aculops spp.—on three varieties of carnation (Finesse, Optima and White Barbara) in a flower farm in Kenya. Over a period of 24 months, those carnations established in a soilless substrate (pumice in gunny bags) harboured on average less than five mites per leaf as compared to over 20 per leaf on plants established on bare soils. This was the case whether the crop was judiciously or prolifically sprayed with acaricides. The study further established that the economic gain was the same when lower volumes of pesticides were used, whether sprayed judiciously or prolifically. The variety White Barbara generally harboured higher mite numbers than Finesse or Optima. Furthermore, there were fewer rejections, and higher market value when plants were established on pumice substrate compared to bare soils. The study further showed that planting in pumice holds promise for mite control in flower farms. Furthermore, predatory natural enemies of the pest mites, including phytoseiid mites and Orius spp., were conserved in plots where pumice was used with minimum spray.

The effect of gamma irradiation on the time-course mortality and radiosensitivity indices in 1- and 10-day-old adult Tribolium anaphe, T. brevicornis, T. castaneum, T destructor and T. freemani, was studied. Longevity was always adversely affected by irradiation, and it was linearly dependent on the dose rate. Except for 10-day-old adults, all the insects died within 12 weeks of γ-irradiation at 4 and 5 krad. In addition, T. destructor was markedly more radioresistant at all dose levels, and lived longer than the other species. The mean survival times of adults were generally shorter in females than in males for all species. The radiosensitivity indices did not vary widely among the species, but decreased as the dose increased in all the species, indicating that the resistance of the species was dose-dependent.

The population of coffee stemborers (Coleoptera: Cerambycidae) was estimated at six sites in south-west China using two capture-recapture models. Two sampling methods (simple and systematic random sampling), each at three sampling intensities (10, 20 and 30%) were employed for two-time capture attempts from which the capture-recapture estimates were calculated. Estimates from the models were compared with that of census data from the fields. When sampling intensity was 20%, satisfactory levels of accuracy were obtained using the two models. The level of accuracy of the estimates increased as damage rate and mean density of the insect increased. Accuracy was also increased with increasing the sampling intensity, when damage rate and density of stemborers in the plots were low.