Surveys were conducted in 1981, 1983 and 1984 across the island of Puerto Rico to determine the effects of patch characteristics of the tropical herbaceous legume, Crotalaria pallida Ait. on the herbivore and its parasitoids. The mean number of flower racemes per plant and mature pods per raceme varied from year to year and appeared to be influenced by rainfall patterns, but were independent of patch size or plant density. Low larval parasitism was also observed during dry seasons. Proportion of plant patches colonized by Etiella zinckenella was smallest during dry seasons. Local extinction of C. pallida patches was found commonly, with a 77.4% extinction rate during a 6-month period. Patch extinction, which was caused mainly by human activity, was independent of patch size.

Pods of C. pallida within patches were inspected for lima bean pod borer, E. zinckenella (Lepidoptera: Phycitidae) injury. The number of pods bored per mature raceme, and the per cent of bored pods were positively correlated with the number of host-plants per patch and the (surface) area of the patch. No correlation was found between per cent parasitism and pod borer larval density. However, per cent parasitism was influenced directly by C. pallida plant density and patch surface area. Given the transient nature of C. pallida patches and the changes that occur over a season, these positive responses of parasitoids to plant density and patch surface area are important components for their successful exploitation of larval hosts.

As part of an extensive and systematic programme to find genetic sources of resistance to Aphis craccivora, a major pest of cowpea, Vigna unguiculata, a total of 181 accessions from the germpiasm collection at the International Institute of Tropical Agriculture were screened in glasshouse tests using a simple visual damage scale. Twenty-four accessions showed considerably reduced damage. To confirm these results on IS selected accessions, aphid population growth over 10 days was recorded. Zero aphids were found on three accessions (310,408-P2 and 801); another six accessions had populations of less than 30, compared with 200–400 on susceptible varieties. The other accessions showed only partial antibiosis and/or tolerance.

Experiments were conducted in 1989 to evaluate converted sorghum accessions for preflowering extended panicle and soft-dough stage panicle feeding resistance to fall armyworm, Spodoptera frugiperda (J. E. Smith), by incorporating plant tissue into artificial insect diet. Spodoptera frugiperda biological parameters measured were larval and pupal weights, mean duration of the larval stage, time to adult eclosion, survivorship, fecundity, net reproductive rate, intrinsic rate of increase, and relative fitness. The converted lines IS 2246C, IS 2403C, IS 2825C, IS 7007C, IS 8337C, IS 12592C, IS 12612C, IS 12657C, IS 12666C, and IS 12681C were more resistant to both preflowering and soft-dough stage panicle feeding by S. frugiperda than the resistant check NK Savanna 5. The genotypes IS 1340C, IS 2553C, IS 2569C, IS 6911C, IS 7498C, IS 12219C, IS 12617C, IS 12662C, and IS 12664C were more resistant than the resistant check to S. frugiperda feeding in the soft-dough stage, but not in the preflowering stage of panicle development. Plant antibiosis was the major mechanism of resistance in these lines at both stages of the panicle development.

In many countries in eastern, central and southern Africa, twice-weekly to two-weekly acaricide applications are practised to prevent mortality of exotic cattle from tick-borne diseases. This practice has been extended to areas where only local cattle are present. These measures are very costly, inefficient in controlling diseases and ecologically undesirable.

In view of the many difficulties with the present method of tick control, exploitation of tick-resistant cattle breeds in enzootically stable situations would appear to be a pragmatic, alternative approach to the intensive use of acaricides. This paper reviews studies on host-tick relationships in Africa with a view to understand the role of naturally acquired resistance in limiting tick populations and hence its use in integrated pest management strategies. The levels of information required are outlined such as identification and quantification of resistance, effect of cattle breeds and productivity and economics in relation to host-resistance.

Light and pheromone trap networks were used to monitor and compare moth catches ofHelicoverpa (= Heliothis) armigera (Hubner) in both types of traps at many locations across India. There were obvious changes with latitude in flight patterns and in the correlation between light and pheromone trap catches. At northern locations, the correlation between light and pheromone trap catches were higher as compared to southern locations. The traps located in the central part of India showed correlations, intermediate between those of northern and southern locations. Pheromone traps were thus found suitable for monitoring at northern and central locations. At southern locations, where light and pheromone trap catches differ considerably at different times of the year, both types of traps should be operated simultaneously for better monitoring of this insect. Good correlations were found between larval population and light and pheromone trap catches of H. armigera at Patancheru, one of the southern locations in India.

Competition between Plodia interpunctella (Hubn.) and Ephestia cautella (Wlk.) was studied in groundnuts and in a limited amount of standard medium (maize meal, wheat bran and glycerol at the ratio of 8:8:1) (w/w) when the species were reared separately (conditions PI and EC), when one was added before the other (conditions P+E/2 and E+P/2) and when both were introduced together (condition PI/EC). Separately, each species was well maintained on the standard medium, while E. cautella was the better competitor in groundnuts under conditions E+P/2 and PI/EC. The results offer a possible explanation for the pest status and distribution of the two moths species in groundnuts and where their ranges overlap, especially in the tropics.

The possibility of the involvement of pod wall toughness in the resistance of cowpea, Vigna unguiculata (L.) Walp., to the legume pod borer, Maruca testulalis was studied. The toughness of non-intact and intact pod wall increased with age, but the rate varied at different growth stages of the pod as well as between cultivars. There was a positive and significant correlation (r = 0.82**) between pod age and pressure required to penetrate pod wall. No significant differences (P > 0.05) were observed in non-intact pod wall toughness between TVu 946 (resistant) and IT82D-716 (susceptible) at all the growth stages tested. However, significant differences (P < 0.05) were observed between these two cultivars for only 6-day-old intact pods where IT82D-716 recorded a higher value than TVu 946. Correlation between pod damage severity by M. testulalis and toughness of non-intact and intact pod wall of these cultivars at different growth stages were not significant.

While pod wall toughness would be a desirable trait, it is concluded from this study that pod walls of the cultivars studied did not play any appreciable role on cowpea resistance to the larvae of M. testulalis.

The inheritance of phosphoglucomutase (PGM) was studied electrophoretically in four strains of fig moth, Ephestia cautella. Individual zymograms exhibited one zone of activity with a two-banded pattern in strain A, and one-banded pattern with slow migrating mobility in strains B, C and D. Segregation of banding patterns between parents and progeny in strain A, and chi-square analysis of segregating alleles indicated that the PGM isozymes were regulated by two codominant alleles segregating at a single autosomal locus. No sex linkage was observed in reciprocal crosses. The data also suggest mendelian segregation, and that the PGM isozymes are monomeric in structure. The results of this study indicate that the PGM locus can be a useful marker for studies of E. cautella population dynamics.

An experiment was undertaken at two locations in Nigeria to identify the major insect pests of cowpea, assess the yield losses caused by them and recommend profitable control packages. Various combinations of insecticidal applications were tested at four crop growth stages, in conjunction with varieties possessing moderate levels of resistance to one or two insect pests. Flower thrips were the most important pests, followed by pod sucking bugs and foliage pests. The resistance levels of the varieties did not contribute much to reducing yield losses. Yield losses of upto 75% were caused by insects attacking cowpea during the flower bud and flowering stages, and of 23% by insects attacking during pod development. Insects attacking during the foliage growth stage had little effect on yields. Profitable spray schedules which increased yields by about 50–200% were: three sprays at flower budding, flowering and podding (the optimum), the sprays at either flower budding and flowering or flower budding and podding depending on the location, and one spray at either flower budding or flowering stage. Other spray combinations were also viable, but less profitable. Appropriate recommendations for various categories of farmers are given.

There were significant differences in the level of susceptibility among the 12 varieties which were screened for resistance to A. lycopersici Pronounced tolerance to leaf damage was recorded on varieties Early Stone Improved and Beauty. Oxheart and Bonny Best both of which had comparatively lower mite densities were highly susceptible. Flower bud formation was not significantly affected by the mite damage. However, the number of dead flowers and flower buds on infested plants was significantly more than on protected ones.

Russetting of young fruits due to mite damage differed significantly among the varieties tested, and was positively correlated with moisture content of young fruits. The least and most affected varieties were Beauty and Red Cloud respectively. The percentage yield loss was highest on Hybrid Beefmaster and Oxheart and lowest on Roma and Money Maker.

Risk-benefit considerations have stimulated efforts to develop technology to overcome the limitations of procedures that place excessive reliance on the use of acaricides for the control of ticks affecting cattle. One of the alternatives to acaricides is the selection and use of breeds of cattle with a natural propensity for developing acquired resistance to ticks. The literature on aspects of the modes of expression and mechanisms of resistance of cattle to ticks, is reviewed along with information on the successful efforts in Australia to develop productive Bos indicus ï Bos taurus breeds with the ability to develop high levels of resistance. The use of cattle resistant to ticks is discussed in relation to other factors that should be considered in the design of a programme for tick control.

Two indigenous maize cuitivars, Inbred A and Nyamula, were evaluated in a field trial for their susceptibility/resistance to Chilo partellus at the artificial infestation levels of 10 larvae/plant and 20 larvae/plant. Foliar damage was caused predominantly by C. partellus, but stem-tunnelling was caused not only by C. partellus but also by another species of borer, Eldana saccharina, which invaded the crop during the tassel emergence stage and persisted during harvest. In the 10-week old crop, the number of C. partellus recorded on Nyamula was greater than on Inbred A, but the incidence of injury to foliage and stem-tunnelling on the two cuitivars was the same. At harvest the degree of damage to the two cuitivars varied. At the infestation level of 20 larvae/plant, the cuitivars suffered equal stem-tunnelling. There was a significant negative correlation between stem-tunnelling and yield for Inbred A, but the correlation was not significant for Nyamula. At the infestation level of 10 larvae/plant, the correlation between stem-tunnelling and yield was not significant for either of the cuitivars, perhaps, due to excessive activity of E. saccharina in the stalks of Inbred A.

Soybean, Glycine max (L.) Merril, and cowpea, Vigna unguiculta (L.) Walp., were grown in field plots in 1988 and 1989 to compare infestation and damage by pod-sucking bugs (PSBs). Population of PSB was monitored by counting adults and nymphs on rows two and six of each plot from 5 to 14 weeks after planting. Cowpea was infested mainly by Clavigralla tomentosicollis (Stal.), C. shadabi (Germ.), Mirperus jaculus (Thnb.) and Aspavia armigera F., while soybean was infested by M. jaculus, Anoplocnemis curvipes (F.) and Riptortus dentipes F. Soybean had exceedingly low PSB density, ≺ 1 bug/2 m-row, in 1988 and 1989. Four sprays of 400 g a.i./ha. dimethoate had no significant effect on pod and seed damage, yield and germination, compared to the unsprayed control. In contrast, cowpea attracted high populations of PSBs, 30 and 1 bug/2 m-row, in 1988 and 1989, respectively. Dimethoate sprayed against PSBs on cowpea resulted in two- to four-fold reductions (P < 0.05) in pod and seed damage and yield increases of 1500 kg/ha. (P < 0.05) in 1988 and 300 kg/ha. (P < 0.05) in 1989.

Autoradiographic observations using (3H) glycine in the salivary glands of Lethocerus indicus, Laccotrephes rubra and Antilochus coqueberti indicated synthetic activity being performed by the glandular epithelia in all the bugs at short incubation periods. Long incubation periods showed that the site of heavy labelling shifts from outside inwards, with progressive incubation timings, namely from the basal borders and eventually into the lumen. This shifting of the labelling from outside inwards suggests the glandular epithelium is also capable of transporting some of the haemolymph proteins into the gland in all the species and thus indicating heterosynthetic origin of saliva.

The ability of a Kenyan sandfly species, Sergentomyia ingrami, to feed on various species of native or indigenous and exotic or introduced plants of Kenya was investigated using the Anthrone test. Some flies contained more sugar than others when they were tested after exposure to the plants.

Feeding performances of 3509 male and 4838 female sandflies, Sergentomyia ingrami, fed on 46 native or indigenous and exotic or introduced species belonging to 21 families of plants found in Kenya were examined. The results indicated more feeding on certain families than on others. The most used families were Musaceae, Araceae and Compositae, while the least was Alliaceae. A liking for certain species was also detected in families with more than one species investigated. Generally, the most used species were Bidens pilosa (Compositae) and Lycopersicon esculentum (Solanaceae). Interaction between the sex of the sandflies and the tested plants was minimal, suggesting that in most cases males and females had similar species likings. Sergentomyia ingrami fed more on two of the exotic species investigated.

The mosquito C. p. pipiens L. never colonize sewerage water covered with duck weed. The Lemna minor vegetations affected the identification of the oviposition site by the females. The amputation of sensilla made the mosquito incapable of choosing the oviposition site. The immature stages of the mosquito are susceptible to the water borne synomones of the duck weed; the first instar larvae are most susceptible and have high mortality.

The line of contact between G. p. palpalis and G. f. quanzensis passes near Brazzaville, at the south and southwest of the Congolese capital. Observations made between 1948 and 1961 show the advance of G. p. palpalis towards Brazzaville, along the Djoué Valley and the Congo River. Recent captures confirm this spectacular advance of G. p. palpalis to the detriment of G. f. quanzensis along the Djoué Valley. Indeed, G. f. quanzensis is no longer found in a distance of 20 km where it used to co-exist with G. p. palpalis. Ecological competition for food or habitat thus occurs between these two closely related species. It is suggested that both heterospecific copulations and demographic pressure play a crucial part in the exclusion.

ECFXPERT is a microcomputer software tool which can be used to investigate tick populations and the control of East Coast fever. The package contains four simulation models: a model for predicting the abundance and seasonality of Rhipicephalus appendiculatus ticks; a model for predicting East Coast fever prevalence within a herd of cattle; and two models for the study of disease control using either acaricidal dipping strategies or chemotherapy. In this paper, the philosophy of the ECFXPERT package, and the underlying assumptions and mathematical techniques employed are presented, along with the results of a number of computer experiments designed to validate and illustrate potential use of the model.

Sixteen taxa in the genus Vigna were compared for susceptibility to attack by Callosobruchus rhodesianus (Pic.) under laboratory conditions. Ovipositional response, adult emergence and their development periods differed significantly between the species. Although oviposition took place on all the Vigna taxa at varying levels, the bruchid was unable to develop successfully on four of the 16 taxa Investigated. V. vexillata var. angustifolia, V. vexillata var. vexillata, V. oblongifolia and V. luteola were resistant to attack.