About 70 insects and five mites regularly or occasionally infest the cotton crop in subtropical Africa. The economic importance of these pests varies according to the climate and cropping pattern in the region. Cotton aphid, Aphis gossypii Glover and yellow tea mite, Polyphagotarsonemus latus (Banks) as foliage feeders and three bollworms, Pectinophora gossypiella Saunders, Diparopsis watersi Roths, and Heliothis armigera Hbn., during boll formation and development, are major pests. Pesticides have been used extensively to suppress the pest populations and infestation levels in the crop. Natural enemies of certain pests occur in the region, nevertheless, their effectiveness in pest control is not well-known or fully exploited. Research on yield loss evaluation, pest ecology, varietal resistance and cultural practices is underway in several countries. Therefore, a global pest management in cotton is discussed in the context of local conditions and perspectives are highlighted.

Studies were conducted on the biology of the recently described Goniozus sensorius Gordh (Hymenoptera: Bethylidae), a gregarious ectoparasitoid of Diaphania indica (Saunders) (Lepidoptera: Pyralidae). Eggs are laid after temporarily paralyzing the host. Mean development time from egg to adult is 11.96 days at 26.43 and 65.08% r.h. The female lays an average of 50.1 eggs during its life time and parasitizes 7.26 hosts on average. The sex ratio is 1:3.91, males:females. Mean adult longevity is almost similar for males (8.55 days) and females (9.81 days). Aphanogmus fijiensis (Ferriere) (Hymenoptera: Ceraphronidae) was recorded as a hyperparasitoid through G. sensorius.

Biological control efforts on Parthenium hysterophorus L. (Asteraceae) in India have gained momentum after the limitations of other methods were realized. Native surveys revealed a large number of insects, but none of them was host specific. Although the introduced beetle Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae) has established at the sites of initial releases, its real impact on the weed and performance in different parts of the country need further evaluation. Fungal pathogens of the weed hold promise for classical as well as microherbicidal control. The use of parthenium phyllody MLO as a biocontrol agent requires establishment of host and vector specificity. Mycotoxins are a potential group of herbicides on which serious studies are yet to begin. Studies on control of the weed through interference and allelopathy by Cassia uniflora Mill. (= C. sericea Sw.) (Leguminosae) have produced promising results. Toxic leachates of C. uniflora and autotoxic principles of the weed deserve attention. Integrated biocontrol strategies envisaged for wastelands using introduced insects and pathogens, allelopathic plants, and agroecosystems using native pathogens, mycotoxins and autotoxic principles, will help combat this apparently invincible weed.

Investigations were conducted on dried fish samples purchased from Faku and Sabo markets (in the Kainji Lake Area) and stored for 6 months. The most abundant insect pest was Dermestes maculatus particularly the larvae. At 3 months of storage, weight losses were 13% for S. galilaeus, 17% for T. niloticus and 19% for Alestes sp. respectively, with the products reduced to powder mixed with insect exuviae and dead larvae. An analysis of the salt content of the samples showed no significant difference between salt composition at the beginning and end of the experiment. A relationship between salt content and the degree of infestation by insect pest could not be established, possibly because of the low percentage salt composition observed on all samples. A suggestion is made as to the possible areas of research to combat the menace of insect pest infestation of dried fish.

The study of the population dynamics of Helicoverpa armigera (Hübner) in Cicer arietinum (chickpea), Lycopersicon esculentum (tomato), Abelmeschus esculentus (okra) and Zea mays (maize) crops revealed that the insect passed through five overlapping generations in a year. The growth of the population of H. armigera and its generation survival were maximum in second generation followed by fourth, third, fifth and first generations. Parasitoids, predators, fungal and viral diseases and abiotic factors were among the various observed mortality factors, although the role of predation was not specifically investigated. The key mortality factor within generation was an unidentified pupal parasitoid. The key mortality factor operating between generations was the variation in natality (log of ratio of maximum potential natality and actual eggs). In spite of the biotic mortality factors operating on H. armigera populations, the number of eggs laid is the most important factor that governs the trend of the population growth in all generations. Therefore, a powerful control measure is necessary by either trapping the adult moths or by cultivating trap crop to distract egg laying for those crops to be protected.

Cytogenetic studies in indoor resting An. gambiae s.l. complex in five selected localities from east, south, and southwestern parts of Ethiopia were conducted. An. arabiensis was the only cyto-species found. Close examination of the inversion polymorphisms revealed the existence of two more polymorphisms in the 2Ra and 2Rd inversions, in addition to those previously reported viz. 2Rb and 3Ra, by Mekuria et al. (1982) and White (1974). The study covered wide ecological and altitudinal ranges and the karyotype frequencies were in agreement with the Hardy-Weinberg expectations. However, it was not possible to correlate the relationship between the 2Rb inversion and altitude as has previously been reported by Mekuria et al. (1982). The adaptive value of the 2Rb to increase in altitude (Mekuria et al., 1982), in view of diverse ecological and climatic conditions in An. arabiensis in Ethiopia is open to question.

The probability of a Glossina pallidipes picking up an infection from a single blood meal in Lambwe Valley was estimated to be 0.0092 for Trypanosoma vivax, 0.0028 for T. congolense, 0.00097 for T. brucei and 0.00024 for the human infective T. brucei. In cattle, the prevalence of blood protozoa was Trypanosoma spp. 5.55%, Babesia spp. 2% and Theileria spp. 33.06%. Thirty-eight point three per cent of the cattle with trypanosomes also had Theileria spp., 2.12% of the cattle with trypanosomes also had Babesia spp. and 88.28% of the cattle with babesia had also Theileria spp.

In the present work, influence of food plants on different life table parameters of the parasitoid Trioxys indicus Subba Rao and Sharma was studied as affected through its host Aphis gossypii Glover. Age-specific survival of T. indicus on aphids bred on Lagenaria vulgaris was greater (7 days) than on Luff a cylindrica and Cucurbita maxima (4 days). The net fecundity rate, total reproductive period, intrinsic rate of natural increase, intrinsic rate of total fecundity and weekly multiplication rate of T. indicus fed on L. vulgaris was higher than on other cucurbit food plants. Doubling time of the parasitoid fed on L. vulgaris was lower than on other food plants, whereas the mean generation time of the parasitoid on L. vulgaris was slightly higher than on L. cylindrica but lower than on Cajanus cajan and C. maxima. All these measurements (considered indices of fitness of the entomophages) indicated that population growth pattern of T. indicus fed on L. vulgaris is faster than those fed on other food plants.

Buprofezin treatment of brown planthopper, Nilaparvata lugens Stal. at sub-lethal doses resulted in the survival of individuals with varying reproductive potentials. From this reproductive potential of different stages, population build up of second generation was calculated. Logistic function was found to fit more closely the data on population growth at different concentrations. It could thus serve as a mathematical model for predicting the second generation population build up in a buprofezin treated population.

Preponderance of Musca spp. and their accessibility to goat feeds and faeces containing Eimeria oocysts prompted an investigation into the role of these flies in the dissemination and/or transmission of goat eoccidiosis. Seventy per cent of the dissected 300 Musca spp. caught in the goat pens where faeces containing Eimeria oocysts were widely scattered, possessed the oocysts in their digestive organs, with the highest number found in the gut. When Musca spp. were induced to feed on faecal solution containing Eimeria oocysts, oocysts were recovered from the flies through regurgitation during subsequent feeding on glucose solution. At low concentrations of 300 and 500 oocysts per g faeces, substantial numbers of oocysts were recovered from the flies only up to 1/2 hr after feeding on the infected faeces; at higher concentrations, oocysts were recovered up to 2 hr. Results of other experiments also showed that the nurriber of flies in which oocysts were found and the number of oocysts recovered were highest when the flies were dissected immediately and 1/2 hr after exposure to infected faeces. The circumstances under which Musca spp, could sustain eoccidiosis and coccidiosis in a goat herd are discussed.

Plant associations and rates of population interchange between two food plant areas for the armoured ground cricket, Acanthoplus speiseri Brancsik were investigated. A. speiseri was associated with 40 species of plants spread over 11 families. The ground cricket had a significantly high frequency of association at P = 0.05 with Rottboelia exaltata Linn. F. and Hyparrhenia nyassae (Rendle) Stapf. The ground cricket preferred members of the Gramineae to those of other families, 69% of the total number of ground crickets collected from the plants in this study were from grasses and among these Zea mays L. and Sorghum vulgare Pers. were opportunistic associations.

The rates of population interchange between two areas dominated, respectively, by Nicandra physaloides (L.) Gaertn. and R. exaltata with several species of Hyparrhenia were unequal. There was net emigration of 76.69 ground crickets to the N. physaloides area in 10 days.

The significance of the findings on plant associations and rates of population interchange between food plant areas of A. speiseri to future sampling and control of the ground cricket is discussed.

Spatial dispersion patterns of Acanthoplus speiseri were inestigated. Four indices of dispersion derived from either Iwao's measure or Taylor's Power Law were used to study spatial dispersion patterns. All indices were in agreement in identifying aggregated dispersion patterns in the cricket populations sampled. Iwao's index of basic contagion revealed that individual crickets formed the basic components in the aggregated dispersion of the populations.

Effect of fluctuating and constant temperatures on different population growth parameters of Chilo partellus (Swinhoe) infesting sorghum was studied in the laboratory. On the basis of intrinsic rate of natural increase (rm) values, the optimum constant and fluctuating temperatures for the multiplication of this pest was 30 ± 1°C and 31.0 to 35.8°C, respectively. But the favourable range of temperature varied from 27.5 to 30.0°C under both constant and fluctuating temperature conditions. Mean length of generation (T) at this range of temperature varied from 38 to 41 days. It seems that Chilo partellus may not persist at or above 40°C and below 20°C, as the rm values at these temperatures were negligible or zero. This information can be used in working out the strategy for controlling Chilo partellus.

Data from regular field samples throughout the life cycle for five generations of the legume pod borer, Maruca testulalis on cowpea crops at one site, and three generations at another, were used to construct life tables and through key factor analysis to determine the key mortality factor. The total mortality from egg to adult was 98.4–98.6% at site 1 and 98.2–99.4% at site 2. At both sites the highest mortality occurred between the eggs and the third instar larvae, whilst the fourth instar larvae suffered the lowest mortality. The commonest cause of mortality was classified as disappearance, followed by disease. Parasitism contributed minimally to M. testulalis mortality. At site 1 disappearance at the egg stage was the key mortality factor and was significantly correlated with the total generation mortality. At site 2, disappearance operating at the larva 1 and 2 stage was tentatively identified as the key mortality factor. The data from site 1 showed no significant correlation between population density and mortality at the same stage. This study provides the first detailed analysis of M. testulalis populations and should contribute towards developing control strategies for this important pest of cowpea.

Grainage parameters, viz. pupal weight, rate of moth emergence, fecundity and hatching were studied among four bivoltine pure races and their five single and four double cross hybrids of silkworm Bombyx mori L. The significant increase in double cross hybrids over pure races was 11.72, 7.43, 19.45 and 12.26% for pupal weight, rate of moth emergence, fecundity and hatching, respectively. The fecundity in double cross hybrids improved significantly over single cross hybrids to the extent of 16.03% whereas pupal weight, rate of moth emergence and hatching increased to the extent of 4.38, 5.90 and 5.76%, respectively.

The extent of standard heterosis and heterobeltiosis was maximum in double cross hybrids and the heterosis was more pronounced for fecundity.

The xerophytic perennial plant, Agave cantala Roxb. was studied for its biological activity on diamondback moth Plutella xylostella (L.). When cabbage leaves treated with acetone extract of A. cantala leaf were fed to the larvae in all instars, the extract was found to be weakly toxic at the highest concentration of 60 mg/ml, but it prolonged the larval and pupal periods, decreased the percentage of adult emergence and adult longevity. The fecundity and egg hatchability of adults emerging from final instar larvae fed with treated leaves decreased significantly. The eggs laid on treated leaves showed reduced hatchability.

The Integrated Pest Management (IPM) Programme under development at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) calls for a proper monitoring system. Experiments conducted in groundnut fields at ICRISAT Center near Hyderabad, in peninsular India, to establish the optimum height for pheromone traps to monitor Spodoptera lituta (F), indicated that the male flight pattern changes considerably during the cropping period. During the seedling stage (sowing to 6 weeks), most moths were caught at 0.5 and 1.0 m. In the initial growth phase (7–11 weeks), the traps at 4.0 m caught most moths. During the optimum growth phase (12th week to harvest) of the crop the traps at 1.0 m height trapped most moths. After harvest, the traps at 4.0 m again recorded the highest catch. These data are interpreted in terms of the migration pattern of S. litura moths during the crop season. We suggest monitoring this species, using 1 m height traps.

Males were found to be more active around 0300 hr, with a small peak after sunset (2000 hr). Irrespective of season, the peak flight activity of this species was around 0300 hr in groundnut fields.

Seven cowpea cultivars and a susceptible and two resistant checks were evaluated for their preference by Clavigralla tomentosicollis for oviposition and feeding under free-choice condition in the screenhouse and under no-choice in mesh cages. Female bugs had no distinct ovipositional preference for any of the test cultivars than the susceptible check. There was a distinct preference for egg laying on the undersurface of the leaves than on the other plant parts.

The susceptible check was more preferred for feeding by the bug than the other test cultivars. Thus, percentage seed damage was significantly reduced on the test cultivars than the susceptible check. There was no significant difference in percentage seed damage between the free-choice and the no-choice tests among the test cultivars except TVu 1890 (the resistant check) and Ife Brown (the susceptible check). The implications of the results are discussed.

Thirty-six cowpea cultivars were evaluated for their resistance to the pod-sucking bug, Clavigralla tomentosicollis Stål, in the screenhouse and in field experiments. Absolute resistance was not found in any of them, although cultivars with relatively low percentage seed damage were present. Seventeen cultivars were significantly less damaged than the susceptible check in the field experiments. Seven cultivars had less than 60% seed damage. Of these, TVu 3354, TVu 3355, TVu 3372, TVu 8525 and TVu 3199 were the least damaged. Per cent seed damage on cultivars in the field was not consistent with that in the screenhouse, because of the influence of other pod-sucking bug species and environmental factors.

Yield components such as 100 seed weight and the number of pods per plant were related to the resistance of the test cultivars to the bug attack. Cultivars with smaller seeds and more pods per plant were less damaged. The number of seeds per pod was not related to the degree of seed damage. Similarly, morphological parameters of the cultivars were not related to the degree of seed damage.

Seven selected cultivare of common beans Phaseolus vulgaris L. were evaluated for resistance at two sites under different weather and beanfly population pressures in the field. The indices of resistance were the number of leaf punctures, eggs, larvae and puparia and per cent dead plants. Beanfly species, Ophiomyia spencerella (Greathead) and Ophiomyia phaseoli (Tryon) infested the bean plants in the field. There were seasonal differences in the response of the cultivare to beanfly infestation attributed to differences in the level of attack of the bean crop, being highest in the non-cropping season of 1985 and lowest in the long rains of 1985. Despite the variation in results, Gip 1004 and Gip x-92 showed some resistance on the basis of their least plant mortalities and low larvae/puparia surviving on them. When the beanfly population was high enough to cause death of the bean plants, percentage plant mortality was correlated to the numbers of larvae and puparia of beanflies and it may be the best parameter for resistance.