The development of Helicoverpa (= Heliothis) armigera (Hb.) (Lepidoptera: Noctuidae) on foliage, squares and bolls of four cotton cultivare [G 27, HD 167 (Gossypium arboreum), H 777 and H 974 (G. hirsutum)] and one hybrid (HHH 81) was studied under controlled conditions. The results indicated that some biological parameters were influenced only by plant parts and not by cultivar/hybrid. The larvae died as first instars when reared on the foliage of cv. G 27 and HD 167. Irrespective of cultivar, the larvae and pupae weighed more when the larvae were reared on cotton bolls than on squares and foliage. The larval and pupal periods were shortest for larvae reared on bolls, followed by squares and foliage. The fecundity of the female was highest when the insect was reared on bolls, followed by foliage and squares. The longevity of the female moth was highest in insects reared on bolls, followed by insects reared on squares, and on foliage. The longevity of the male moth was not influenced by rearing on the different plant parts. The duration of the life cycle was shortest for insects reared on bolls, followed by squares and foliage.

The factors effecting establishment of salivarian trypanosomes in Glossina (tsetse flies) are reviewed. Recent observations on host–parasite relationships are outlined in the trypanosome-Glossma system. These include, in Trypanozoon, the penetration of the peritrophic membrane; the infection of the midgut cells; the finding of cyst-like multinucleate forms in midgut cells; and the observations on haemocoelic stages in laboratory and field studies. The implications of haemocoelic infection are discussed in relation to work on other Trypanosomatidae in insects and the importance of studies on the possible immune mechanisms of tsetse are outlined.

The interaction between trypanosome parasites and the surfaces of Glossina are briefly reviewed. Recent studies on the relationship between salivarian trypanosomes and LC1 and LC2 mechanoreceptors in the labrum are presented, which indicate that trypanosomes could impair receptor activity in different ways which would result in increased probing. The epidemiological and epizootological implications of these suggestions are outlined. The relevance and importance of trypanosome infection rates in Glossina are discussed.

To study the effect of temperature on the development and predatory behaviour of Culex (Lutzia) tigripes, immature stages of the predatory mosquito Culex (Lutzia) tigripes were reared at temperatures ranging from 12–37°C and provided Culex quinquefasciatus larvae as prey. Larval developmental duration decreased with an increase in rearing temperature until an optimum temperature of 30°C was reached. Above this temperature, the immatures developed slower. In contrast, pupal developmental duration decreased at temperatures above 30°C, being shortest at 32°C. The lower and upper threshold temperatures for larval development were around 12°C and 34°C respectively. Fourth instars were the most voracious and had the longest developmental time. The daily rate of predation increased with temperature, with more prey larvae being consumed at 30°C. Although they consumed more prey, Cx. tigripes larvae and pupae were smaller at high temperature. The increase in prey consumption during the entire larval developmental period at 20°C was attributed to a longer larval duration at this temperature. Developmental period and growth of male and female larvae reared at a particular temperature were not significantly different. Depending on temperature, each larva consumed between 160 and 229 Cx. quinquefasciatus larvae during its development. The implications of these findings to the possible use of Cx. tigripes for mosquito control are discussed.

The predacious mite, Pachylaelaps aegyptiacus Hafez & Nasr completed life cycle when fed on eggs of housefly, Musca domestica (L.) at 25 ± 2°C and 70–80% r.h. in the laboratory. The durations of the immature stages and of the adult stage were determined. Immature stages of P. aegyptiacus consumed in total an average of 16 eggs of housefly, whereas each day throughout her life, the adult female consumed an average of 7.6 eggs of housefly. Daily rate of single and multiple mating was 0.93 and 1.0 eggs/female respectively. Description of immature stages of the predatory mite was given.

The inheritance of resistance in grain sorghum to the spotted stemborer, Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae) was studied in F3 plants derived from crosses between nine locally adapted inbred lines and two sources of resistance. Antibiosis resistance was measured as the relative growth rate of larvae in the whorls of 6-week-old plants. Most F3 plants were either as resistant as, or more resistant than, the resistant parent. This indicated dominance of resistance over susceptibility and the occurrence of transgressive segregation. The segregation pattern in the F3 generation suggested the presence of at least four dominant genes. Two families homozygous for these genes were identified.

Field infestation of millet by Sitotroga cerealella (initial infestation) has been studied in two cropping systems and in three locations in Senegal. In all cases, ears were attacked since harvest, but the level of damage was 10 times higher on ears from fields close to dwelling houses than on those away from dwelling houses. In this way, the author discusses the problematic conservation of millet seeds in farm conditions, depending on that initial infestation in one hand and on the other hand on storage method of millet ears in traditional granaries.

An ecological study was conducted in two pools, one temporary and one semi-permanent at the Kenya coast to determine the relationship between infection levels of Coelomomyces indicus Iyengar in larvae of Anopheles gambiae Giles, and the species and density of copepods found in these sites. Microcyclops minutus Claus, an intermediate host of Coelomomyces indicus, was the predominant species in both pools. Other species were, Mesocyclops leuckarti Claus, Mesocyclops leuckarti pilosa Kiefer, and Mesocyclops (Thermocyclops) decipiens Kiefer. Infections occurred during the periods when M. minutus densities were above 12 cyclops per 250 ml of water. A positive relationship was shown between M. minutus density and infection levels in An. gambiae with C. indicus. The r-value for this relationship in the temporary pool was 0.726, and in the semi-permanent pool, 0.639.

Cowpea, until recently the major food legume in Ghana (in terms of area under cultivation) has been witnessing a decline in production at the expense of groundnuts. Among the factors leading to the decline are the havocs caused by insect pests and diseases with the former being of major importance.

The paper presents some of the systematic screening and testing procedures of both exotic and indigenous materials with the aim of evolving varieties that are not only high yielding but also resistant to a broad spectrum of these prevalent insect pests.

Experiments were conducted in the laboratory to screen the leaf extract of Dracaena arborea (Willd.) Link for the presence of chemical groups with insecticidal activity against Sitophilus zeamais (Motsch.) and Callosobruchus maculatus (Fab.). The plant materials were collected, dried, ground to fine powder and extracted with 90% ethanol. Phytochemical screening involved the use of thin layer chromatography analysis for chemical compounds such as alkaloids, tannins, saponins, anthraquinones, flavonoids and terpenes. Partitioning of the extract was carried out by dissolving the extract in water to obtain the aqueous phase, which was partitioned between equal volumes of chloroform, n-hexane, n-butanol and ethyl acetate. The different fractions were screened for insecticidal activity against S. zeamais and C. maculatus. Some fractions of the leaf extract such as ethyl acetate and aqueous fractions demonstrated 100% mortality, offered protection to grains, reduced progeny development and repelled the insects compared with the control. Based on the activity of some fractions, the leaf extract of D.arborea has the potential for development as a botanical insecticide against S. zeamais and C. maculatus.

Experiments were conducted to elucidate the effect of host density on sex ratio of parasitoid offspring, using Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) and its endoparasitoid Campoletis chlorideae Uchida (Hymenoptera: Ichneumonidae). The sex ratio of Campoletis chlorideae was female-biased showing a linear decrease with increasing parasitoid density at fixed host densities. However, with more hosts available, the number of parasitoids emerging increased, stabilising after a density of 32 hosts per parasitoid. To obtain a female-biased sex ratio, a low density of parasitoids should be released at a recommended site.

Riverine tsetse, which are vectors of human and animal vectors, are very difficult to control because of the specific nature of their habitat and behaviour. The problem, however, is not technical, because nowadays entomologists have at their disposal a wide range of efficient methods to eradicate them. The problem is therefore practical, and it is related to the way in which these methods are used.

In fact, the entomologist is faced with several intractable problems that reduce his scope of action. First of all, because he has to pay due regard to the environment, he is obliged to refrain from taking any action that may be fatal for the tsetse, but harmful for the environment such as cutting down woody, scrub and shrub vegetation, setting bush fires, etc. Furthermore, he is not allowed to tamper with wildlife which is the nutritional source of the tsetse, but is also an important source of foreign exchange through tourism. He also must respect the non-target fauna, especially the aquatic fauna, with the result that this limits: (1) the choice of pesticides that can be used in one way or the other, affecting the chain in the biological cycle, invertebrates, fish, birds, mammals and (2) the method of application of chemical, because he cannot use residual sprays or aerial aerosols everywhere.

The entomologist must also take into account economic considerations. The world economic crisis has considerably reduced the availability of potential sources of donor funds, and most African countries afflicted by sleeping sickness and animal trypanosomiasis cannot individually undertake large-scale eradication campaigns for lack of funds, adequate equipment and trained manpower. Using aeroplanes or hordes of workers is therefore out of question. Similarly, controlling the tsetse through the use of sterile male release technique, which is a complementary control method to attain the 0 density, seems now to be unachievable because of the huge investments that are required.

Finally, many scientists, economists and ecologists have recently begun to wonder if controlling the tsetse is after all a good solution, since their disappearance would lead to the overexploitationofthe land freed, resulting in the destruction of the vegetation and bio-climatic changes and finally total desertification. The challenge therefore is how to control the tsetse under these conditions.

The use of traps seems to be a good solution. Experiments conducted in Africa (and since the discovery of certain olfactive attractants) have shown that it is effective, safe for the environment, easy to use, and especially very cheap, when it is used by the rural communities. But even with trapping, a number of questions are being asked: Is it better to kill the tsetse than to sterilize it? Is impregnating it with an insecticide indispensable? Is there no risk of selecting a “trap resistant strain” of tsetse? Can the use of traps lead to eradication?

In fact, in most cases, eradication is wishful thinking and controlling the fly is the only realistic thing to do; the entomologist has to control, but cheaply and with a less harmful technique. Besides, because of its numerous qualities, trapping is the only method that can be used nowadays as long as it is used wisely.

The purpose of this study is to elucidate the production dynamics, growth characteristics and trends of African trypanosomiasis research (ATREP) literature between 1900 and 1985 through graphical methods.

The data analysed comprised 5139 articles from Tropical Diseases Bulletin and Tsetse and Trypanosomiasis Information Quarterly. Counting technique was employed in sorting the articles according to yearly production and respective subject disciplines. The bibliometric ranks of the disciplines were determined based on (1) the total output and (2) the average decennial relative changes (Rc) in publications between 1936 and 1985 using 1936/45 as the base decade.

The results show that the growth is neither linear nor logistic but exponential with an average 39.5-year doubling time. A marked feature is the occurrence of high “epidemic” peaks between 1910–1914 and 1979–1985, a state in which publications were produced at relatively high level probably due to new discoveries or research orientation; and hence capable of quickly infecting a large number of scientists enhancing productivity. There was also a low level of activity from 1914 which lasted for about 22 years.

The foundation disciplines for African Trypanosomiasis Research Programme (ATREP) are entomology and parasitology. Entomology had the highest bibliometric rank followed by parasitology. However, the Refactors indicate that greater attention, as depicted by publication outburst, was given to physiology, immunology, biochemistry, and epidemiology between 1976–1985 than had been before.

In spite of its consistently higher output, entomology exhibited the greatest fluctuating growth trend than all the other components. A possible explanation for this behaviour was ventured.

Different ages of the two spotted spider mite Tetranychus urticae Koch and the predacious mite Amblyseius gossipi El-Badry eggs were exposed to selected concentrations of cypermethrin (500 ppm), flucythrinate (200 ppm), cyfluthrin (100 ppm), fenvalerate (200 ppm), Pyridaphenthion (25 ppm), dicofol (250 ppm), avermectin (10 ppm), and dimilin (50 ppm). Generally, the synthetic pyrethroids were effective on eggs especially those of A. gossipi. Dicofol was rather toxic to T. urticae eggs, while avermectin was only effective on older eggs of both species. Eggs treated with different pesticides at late stages took longer to hatch, particularly in the case of A. gossipi.

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.

An experiment to examine the effects of four agrometeorological factors on population fluctuations in legume pod borer, Monica testulalis (Geyer) in two cowpea varieties was carried out under field conditions in Ibadan, Nigeria. Plots, 5 x 10 m each, of cowpea varieties IT84S-2246–4 and Dan ilan were planted fortnightly between 5 May and 5 October 1988 (12 plantings in all for each variety). Three peaks of the pod borer populations were observed on the cowpeas. There were smaller peaks on crops planted between 5 May and 1 June and again between 29 June and 13 July and a larger one on those planted between 24 August and 7 September. These two peaks coincided with the peaks of the rainfall.

Significant relationships were obtained between pod borer counts and (a) cumulative rainfall (R2 = 0.41; P = 0.004) (b) number of rainy days (R2 = 0.17; P = 0.04) from plant emergence to 50% flowering. These results suggest though, the distribution of rainfall over time is more crucial than the total amount in determining the fluctuations of pod borer populations. Thus, the adjustment of planting dates is suggested as an IPM tactic to avoid the development of damaging levels of pod borer infestations.

Termites are important agricultural pests in the semi-arid tropics. Conventional methods of control have relied on persistent organochloride insecticides with accompanying health and environmental problems. In contrast, cultural control methods provide untested, but environmentally sound options to farmers. This study reports results from three experiments on the use of mulches to reduce Microtermes obesi and Odontotermes spp. damage with relevance to groundnut production in India.

Termites scarification of groundnut was 80–90% lower for pods dried in neem cake or Ipomoea fistulosa mulches than for pods dried directly on the soil. Similarly, subterranean attack by termites on bamboo baits was 20–40% lower in mulched plots than in controls. However, mulches were ineffective in protecting bullock manure from removal by termites.

Successful use of mulches in termite control may be related to food source concentration. Termite location of concentrated food sources, such as bullock manure, was followed by recruitment of workers and construction of protected runways. In contrast, termites foraging on limited food sources, such as groundnut pods, did not construct runways and had greater exposure to mulches.

Several species of Chilo occur on sugar-cane, out of which five have major pest status. Infestation by these pests causes losses in cane yield and sugar recovery. There are constraints involved in the use of cultural, mechanical and chemical control measures on a large scale, but the nature of the crop facilitates adoption of biological control. Many species of natural enemies occur in the sugar-cane agro-ecosystem, which is relatively less disturbed. They play a significant role in maintaining the pest populations at reasonably low level.

In biological control, the egg parasite, Trichogramma spp., has been widely used with varying results. Among the larval parasites, Apanteles flavipes (Cameron) and Sturmiopsis inferens Townsend have been used on a limited scale and need further testing in other countries. The exotic tachinids introduced, failed to establish against Chilo spp. Not much work has been done on the predators, though the native predators play a significant role in reducing the pest densities. Among the entomopathogens, granulosis virus infecting Chilo infuscatellus Snellen has shown promise in the control of this pest and needs further evaluation in other agro-climatic regions. Future thrust for biological control of Chilo spp., in sugar-cane has also been indicated.

Most dissected Nezara viridula (91.6%) from night catches had their stomach filled (half-full-full) with food, and females had a higher feeding activity than males. Females outweighed males at the ratio 1.3: 1, and an individual was heavier in October than in May. Ovarian development corresponded closely with decreasing fat body of females, and immature individuals had maximum fat in the abdomen. The spent individuals with empty stomach and fat thinly spread over the venter were relatively abundant in April and May, implicating the possibility of large-scale oviposition during these seasons.

A systems model is described for cassava, Manihot esculenta Crantz, two of its introduced herbivores, the cassava green mite (CGM), Mononychellus tanajoa (Bondar), sensu lato, and the cassava mealybug (CM), Phenacoccus manihoti Mat.-Ferr., the introduced CM parasitoid, Epidinocarsis lopezi (DeSantis) and coccinellid predator of the genus Hyperaspis. The systems model includes the effects of weather, soil nitrogen and water levels on the interactions of the system's components.

The model simulates the distribution of developmental times of cohorts initated at the same time, as well as the number and biomass (energy) dynamics of all populations over time. Biomass acquisition and allocation at the population and organism subunit levels (e.g. leaves, fruit, ova) were also simulated. A common acquisition (i.e. functional response) submodel was used to estimate daily photosynthetic as well as nitrogen and water uptake rates in cassava, in addition to herbivory, parasitism and predation rates for the arthropod species.

This paper presents an overview of the systems model. Simulation results for the plant under pest free conditions were compared to field data. In addition, the model was used to estimate tuber yield losses due to CM and CGM feeding, and to examine the beneficial effects of introduced CM natural enemies as measured by reductions in tuber yield losses.

Recent surveys have shown that ant-Homoptera associations are not limited to cocoa trees only but a large number of other plant species serve as hosts for such associations. It has been observed that some ant species may tend more than one Homopteran species on a number of different host plants. Seasonal abundance of the homopterans and their tending ants was studied on cocoa, mango and pigeon pea.

The populations of the ants tend to synchronize with the populations of the Homopterans which they tend during the season.