The spotted stem borer, Chilo partellus (Swinhoe) is an economically important pest in many sorghum growing areas of Asia and Africa. A chronological progress made in Indian and other programmes on natural and artificial screening techniques is reviewed. Numerous germpiasm accessions were evaluated and resistant sources identified and documented for various parameters of resistance such as foliar damage, “dead hearts” and stem tunnelling.

Studies on the mechanisms of resistance showed predominance of tolerance, variable degrees of antibiosis and antixenosis as only a factor for oviposition. The morphological characters and biochemical factors associated with resistance are discussed. The nature of resistance is polygenic and partially dominant over susceptibility. The inheritance patterns of resistance to foliar damage and/or “dead hearts”, and stem (stalk and peduncle) tunnelling damage are different and independent. Pedigree breeding with single and multiple crosses has been useful to transfer resistance in more economic background. Continuous screening for stem tunnelling over several generations improves the level of resistance. Recurrent selection was suggested alternatively with and without infestation for resistance and yield, respectively to increase the level of tolerance. The resistant sources utilized in developing commercially released high yielding varieties, hybrids and derivatives with low to moderate levels of resistance are listed. Efforts to develop cultivars with levels of resistance higher than presently grown cultivars and combining cross resistance to stem borers and shootfly are under way. Current progress has been reviewed and future strategies are suggested.

Sorghum, maize and cowpea serve as staple food for people in Africa and are grown mostly by small-scale farmers. A major constraint on the production of these crops is attack by insect pests among which crop borers are most important, causing 30–80% yield losses. Use of pesticides to control these pests is hazardous and not feasible for the farmers. Alternative strategies for the integrated pest management (IPM) are being developed at the International Centre of Insect Physiology and Ecology (ICIPE) and include the following components: (1) Intercropping and other cultural practices, (2) Plant resistance to insect pests, and (3) Biological control. These IPM components have now been developed to a stage where they can be taken for on-farm trials under farmers' management for subsequent use by them. But, adoption and diffusion of agricultural innovations requires a prior knowledge of the farming systems and the socio-economic circumstances in which the target farmers operate, and their bearing on the use of innovations. Information on these aspects has therefore been obtained through a survey of farming households in Kendu Bay and Oyugis Divisions in western Kenya during April—August 1986. The survey was conducted jointly with UNECA and Ministry of Agriculture, Kenya, under a project funded by the Royal Government of Belgium.

The survey involved interview with 150 farmers, (75 in each Division. In Kendu Bay 27 were men and 48 women whereas in Oyugis 40 were men and 35 women.) and was based on a questionnaire which comprised six sections. Five sections covered the farmers' background, farming practices, pest problems and their control, socio-economic conditions, and accessibility/willingness of the farmers to participate in the project. The last section included field observations on the insect pests of sorghum, maize and cowpea.

On the basis of the information obtained on above-mentioned aspects, criteria were defined and assigned appropriate weigh tage for selecting 25 farmers in each Division for on-farm trials. The selected farmers included 12 men and 13 women in Kendu Bay while in Oyugis 13 men and 12 women were selected.

The measures that need to be taken to counter these limitations and thereby assist the farmers in increasing food production have been recommended.

Four pest control models which combine sterile releases with trapping are analyzed. The traps are baited with either female sex pheromone or food and may contain either insecticides or sterilants. The efficiency for control or eradication is greater when control methods are used in combination than when either control method is used in isolation. The most efficient combination for pest species with high fertility rates is the release of steriles together with the use of pheromone traps containing sterilant. For pest species with very low fertility rates and high survivorship, such as tsetse, sterile releases combined with food traps containing insecticides are most efficient.

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).

Light and pheromone traps were compared for their relative efficiecy and importance in monitoring the Heliothis armigera (Hubner) moths at the farm of Rajasthan Agriculture University, Udaipur, Rajasthan, India, during the years 1984/85 (4 June 1984 to 3 June 1985) and 1985/86 (4 June 1985 to 3 June 1986). Both kinds of traps showed three periods of moth activity during both the cropping years. Both types of traps showed almost a similar trend in population fluctuation during the cropping years and there were significant positive correlations between light and pheromone trap catches, (r=0.87 for 1984/85 and r=0.93 for 1985/86). However, pheromone traps had many advantages over light trap in monitoring the Heliothis armigera moths.

Investigations of the phlebotomine sandflies fauna in a visceral leishmaniasis focus of Aba Roba in Ethiopia were carried out. This resulted in finding Phlebotomus celiae for the first time in the country. Previously, this species was incriminated as a vector of visceral leishmaniasis in Kitui, Kenya where the disease is endemic. It is possible that P. celiae has a wide distribution covering areas of similar ecological niches as those of its first description.

The insect growth inhibitor Alsystin (SIR 8514) was tested for its effects against the immature and adult stages of Culex quinquefasciatus Say under laboratory conditions. A linear correlation was revealed between concentration and larval and pupal mortality. Larval mortality increased from 5% at 0.005 ppm to 74.4% at 0.1 ppm of Alsystin. Complete inhibition of adult emergence resulted after larval exposure to 0.05 ppm. Exposure of eggs (at 0 hr of age) to 0.1 ppm and 10.0 ppm of Alsystin, resulted in considerable decrease of hatching from 87.0% in the control to 61.0% at 1.0 ppm and to 48.0% at 10.0 ppm. The adults of C. quinquefasciatus were seen attracted to the bowls containing 50.0 ppm and 100.0 ppm of Alsystin. However, landing adults died within a short period of time. The different types of deformation in the larva, pupa and adult as a result of exposure to Alsystin are illustrated.

Partial sterility induced by gamma irradiation of Ephestia cautella adult males was studied in five laboratory strains (A,B,C,D and E) which exhibit conspicuous genetic variation in the adult forewing pigmentation. Four of these strains had been reared in the laboratory for more than 80 generations, while the fifth strain has been reared for only 10 generations. When males irradiated with 0.2 kGy were crossed with untreated females, the per cent egg hatch was reduced significantly as compared to the unirradiated control crosses. Strain C showed the highest reduction in the per cent egg hatch followed by a gradual decrease in radiation sensitivity in strains A,E,D and B, respectively. Fecundity and mating frequency appeared not to be affected but the sex ratios were clearly distorted (about two males to one female) in all strains. F1 progeny of all strains were either sterile when mated together (per cent egg hatch = 0.0%), but semi sterile when F1 males were mated to normal females (per cent egg hatch = 0.03–3.95 %). Low fertility was observed when F1 females were mated with normal males (per cent egg hatch = 1.30–15.04%). The cytogenetical investigations showed spermatogenesis to proceed normally in the F1 males, whose fathers had been irradiated (0.2 kGy). However, the primary spermatocyte cells carried multiple chromosomal translocations which were the main cause of the sterility in the F1 males.

Isolation of vitellin from mature eggs of the palo verde beetle, Derobracus geminatus, was achieved by a combination of gel permeation and anion-exchange chromatography. It is a phosphoglycolipoprotein (Mr ˜250,000) that contains 8% lipids, 4% carbohydrates and 0.2% protein-bound phosphorus. The vitellin is composed of three apoproteins designated I (Mr ˜160,000), II (Mr ˜140,000) and III (Mr ˜50,000). The carbohydrate moiety is composed exclusively of mannose and N-acetylglucosamine. All three apoproteins are glycosylated as shown by flourescein isothiocyanate-conjugated concanavalin A and periodate-Schiff (PAS) staining suggesting the presence of a high mannose structure. Further evidence for the high mannose structure was obtained by the ability of endo-β-N-acetylglucosaminidase H treatment to remove the carbohydrate moieties on the apoproteins.

A comprehensive review of the major investigations on the biology and ecology of ticks of Africa reported in scientific journals in the decade 1980–1989 is undertaken. While there have been remarkable advances within the decade on research on feeding habits and patterns of ticks as well as diurnal and seasonal activities, many important areas of research were neglected. These include tick embryogenesis, development and survival under natural conditions, tick modelling, the phenomenon of host's natural resistance to tick infestation, pheromone and biochemical studies and field sampling of ticks. The review also shows that laboratory studies on tick biological systems are scanty in East Africa and the need for greater tick ecological research in West Africa is stressed.

The review shows that in the decade 1980–1989, exotic Bos taurus breeds were predominantly used for experimentation on African ticks and the need to change focus to indigenous B. indicus cattle breeds for experimentation is highlighted. Attention is also drawn to the importance of researchers on African ticks to undertake long term sustainable research with clearly defined goals which can have quantifiable impact on tick control in Africa.

Adding a dye, Calco Oil Red N-1700, to the larval diet of Chilo partellus has been shown to be a useful method for marking the moths for mark and recapture experiments. The method is time-saving and the dye is safe to handle; marked insects and their egg batches are easy to detect. Insects reared on dyed diet did not show any differences in development time or pupal weight compared with insects reared on normal diet.

Role of trichome density in cassava resistance to mealybug, Phenacoccus manihoti Matile-Ferrero was evaluated on the apex, the first expanded leaf and the stem in pubescent and glabrous cassava varieties. Pubescence significantly retarded the rate of settling and establishment of P. manihoti. The weight of the developing larvae was also affected becoming more pronounced at the pre-ovipositing adult stage. However, the relationship between pubescence and P. manihoti weight was not significant. Moreover, the significant differences in weight at the preovipositing adult stage was not reflected in the corresponding fecundity on the glabrous and pubescent varieties. Pubescence accounted for only 18% of the differences in observed fecundity. There was also no significant difference in the development period of the mealybug on glabrous and pubescent varieties. Pubescence appeared to be a mechanical irritant only.

Selected studies in chemical ecology are described that have led to the identification of semiochemicals playing key roles in pest behaviour. In some instances, these compounds can provide alternatives to insecticides, but novel integrated control programmes including use of semiochemicals are described which have greater potential for the future. Thus, semiochemicals can be used to increase the efficacy of entomophagous fungi and to manipulate populations of beneficial insects. New strategies are being developed which use both antifeedant and attractant semiochemicals to deter insects from crops and aggregate them in areas where they can be destroyed. For the long term, strategies are described that employ genetic manipulation of crop plants so that pests are controlled by semiochemicals produced directly in the plants.

Key mortality factors of sugar-cane top borer, Scirpophaga excerptalis Wlk. during the third brood were quantified on a susceptible sugar-cane variety, Co 1148 during 1981 and on susceptible CoJ 64, resistant CoJ 67 and collateral hoste, Sorghum halepense Peru, and Saccharum spontaneum L., during 1982 in Haryana (sub-tropical India). As artificial rearing of this borer is not possible, a methodology to have uniform age group at the beginning of the study by tagging the egg masses and the freshly attacked plants was developed. Results showed that parasitization of various stages and failure of neonate larvae to enter the midribs were the key mortality factors common to all the hosts. In S. halepense there was negative trend index (0.104) due to high mortality of larvae in all the instars. This revealed that it is not a suitable host for top borer. No predators were found to feed on any of the sub-imaginal stages of the borer due to the unique habits of the borer.

Adult (2–20 hr old) viviparous Aphis craccivora were treated with 0.5 to 4.0 μg of precocene II. Treatment led to dose-related reduction in the progeny number, survival and life span of the aphid, but wing development was not affected. With 2.0 μg/aphid or more of precocene II, all surviving offsprings shared precocious metamorphosis, but even with 0.5 μg/aphid, about 20% progeny showed such metamorphosis with 1.0 and 1.5 μg/aphid. Early nymphs tend to undergo precocious metamorphosis earlier, in the second moult.

When males of Tribolium castaneum (Herbst) substerilized with 35, 40 or 50 Gy of gamma irradiation (I) were added to untreated (U) pairs of adults at I : U ratios of 1:1, 2:1 and 5:1, the percentage of hatched eggs was increased by increasing the dose administered to males, as not expected, at equal flooding ratio. The calculated degree of competitiveness showed that males irradiated with the lowest dose (35Gy) were more competitive than males irradiated with the highest dose (50 Gy). However, increasing the ratio of irradiated males with 50 Gy to 10 or 20 increased, accordingly, the competitiveness value. The results also indicate that if an equal number of irradiated males and females with 50 Gy, which had given 99.16 % sterility, were placed with untreated pairs of adults at different ratios (1:1, 5:1, 10:1, and 20:1), the effectiveness was more promising. Moreover, the data further suggest that the effectiveness was enhanced when the ratio of irradiated males and females was increased. Thus, the presence of sterile females along with sterile males in the stored products appears to dilute the effectiveness of normal males, which otherwise would mate with normal females.

Laboratory bioassay tests showed that Bacillus thuringiensis (B.t.) (Bactospeine) treatment of second instar larvae of Heliothis armigera (Hbn.) and Spodoptera litura F. increased their susceptibility to endosulfan, monocrotophos, fenvalerate and cypermethrin. The LC50 of these insecticides to both the species of larvae were lowered when treated with B.t. Comparison of susceptibility ratios showed that the increased susceptibility to insecticides was more in H. armigera than in S. litura larvae.

Field studies were conducted with the synthetic pheromone of peach twig borer to determine the effect of trap distance from host plant, pheromone concentration on number of captured males and seasonal flight patterns in plum and apricot orchards. Traps placed in pomegranate plantation and in fallow land caught significantly fewer males than those placed at the centre and border of plum orchard. However, significantly more moths were caught in traps placed in pomegranate orchard than those in fallow ground. Males captured increased as the concentration of synthetic pheromone increased from 2 to 6 mg per septa. Thereafter, males captured decreased as the concentration increased.

Different modes of immune reactions of insect vectors of human and animal diseases to nematode and protozoan parasites, fungi, bacteria, viruses and to other biological materials e.g. xenografts are discussed in this paper. Since most of the insect vectors of diseases are adult dipterans with low numbers of circulating haemocytes, their mode of defence against metazoan parasites and fungal pathogens is primarily by means of humoral encapsulation, with little haemocyte participation. Although earlier workers reported that humoral capsules in dipterans were formed without direct participation by haemocytes, this paper reveals increasing evidence of cellular involvement in the formation of humoral capsules, both at the initial and terminal stages of the encapsulation process. The role of phenoloxidase system in non-self recognition and in the process of melanization of haemolymph and capsules formed around parasites and fungal pathogens is also discussed. Immune defence of insect vectors against bacterial invasion by means of haemocytic reactions e.g. phagocytosis and nodule formation and by synthesis and release of humoral antibacterial factors e.g. lysozyme, attacins and cecropins is described and compared with similar reactions reported to occur in other insects. The role of lectins in defence of insect vectors against the parasites they transmit e.g. sandflies against Leishmania, blackflies against Onchocerca and tsetse against Trypanosomes is discussed and the possible mechanisms by which some parasites evade recognition and attack by the vector immune systems are also briefly discussed.