The host plant spectrum of Aphis gossypii Glover (Hemiptera:Aphididae) was assessed from 1991 to 1994 in the cotton-growing zone of northern Cameroon. The aphid is generally present on cotton (Gossypium hirsutum L.) and okra (Abelmoschus esculentus (L.) Moench) during the rainy season. During the dry season on the other hand, A. gossypii is observed on a very wide range of plants (63 families, 192 genera and 302 species). During this season, all types of plants, especially legumes, dry-season crops and various types of trees, are colonised. From the representativeness of the sampled plant species within the cotton zone of Cameroon, it is concluded that a part of the A. gossypii population survives the dry season in the Sudano-Sahelian African zone, thus forming numerous reservoirs scattered among plants and in very varied habitats.

The development of a mass-rearing technique of Mantea testulalis by the ICIPE has allowed us to start extensive work on cowpea resistance to the legume pod-borer. A preliminary field observation showed that the cowpea resistance is on the low level. Therefore, our effort initially concentrated on the development of new methods and techniques which were sufficiently sensitive to separate lines possessing small differences of resistance. Eight different treatments were used to develop the methodology of cowpea screening under artificial infestation with Maruca larvae and eggs in the screenhouses and seven treatments in the field.

Plant growing stage has modified the expression of cowpea resistance to Maruca larvae. Five-seven shoots stage (not younger) was found to be most suitable for screening for resistance in pre-flowering period. By using five eggs/plant in pre-flowering stage on cowpea plants grown on the ground, it was possible to differentiate between the resistant and susceptible lines. The standard error between plants treated with 10 eggs/plant treatment was lower than those with five eggs/plant treatment. Therefore, if laboratory colony allows the higher infestation of 10 eggs/plant, it is recommended. Using 10 or 20 eggs/plant in flowering stage correctly segregated cowpea lines for resistance and susceptibility based on larval survival and damage level of flower buds, flowers and pods.

Laboratory experiments on the role of humidity, density and species of prey were conducted in order to better understand the ecology of Teretriosoma nigrescens Lewis (Coleoptera: Histeridae), a predator introduced into West Africa to control the larger grain borer, Prostephanus truncatus. Developmental time of T. nigrescens was very similar among individuals exposed to 30,40, 70 and 90% relative humidity at 30°C, although survivorship varied. At optimal temperature and humidity larvae fed only first-instar Sitophilus zeamais as prey took longer to develop and weighed less at emergence, than those raised on first-instar P. truncatus. Larvae feeding on Tribolium castaneum took longer to develop with only 10% surviving to the adult stage. None of the larvae offered Gnatocerus maxillosus as prey survived. In an analysis of prey consumption rates, no T. nigrescens larvae survived on one P. truncatus first-instar larva per day; 50% survived on two per day, and almost 90% survived on five larvae per day. In an analysis of density effects on T. nigrescens reproduction and survivorship, there was no difference in the number of Fl offspring at T. nigrescens:P. truncatus ratios of 15:300,30:300,60:300 or 90:300, suggesting that the lowest predator: prey production ratio was the most efficient one.

Results of a field survey of certain host-related and off-the-shelf compounds as possible attractants for the black fly, Simulium arcticum (Malloch) (IIS-10.11) (Diptera: Simuliidae), are reported. Silhouette traps were baited with carbon dioxide and candidate attractants in an incomplete randomised block design. Carbon dioxide alone exerted a strong attractant effect on this species. Both acetone and crude whole body odour of cattle (tested in combination with carbon dioxide) were significantly more attractive than carbon dioxide alone (control). Although bovine urine produced larger catches than control (carbon dioxide only) traps, the effect was not statistically significant. Other odours tested in combination with carbon dioxide, including fractions of the crude bovine odour and l-octen-3-ol (a potent tsetse fly attractant), were without apparent attractant effect when compared to the carbon dioxide-only control.

The Murshidabad District of West Bengal, India has practised traditional mulberry sericulture since time immemorial. One of the most important aspects for sustainable development of the sericulture industry is the control and prevention of silkworm diseases. The main objective of this study was to determine silkworm disease incidence over the period 1992–2011 in Murshidabad District and how environmental factors have contributed towards their occurrence. Data were collected from a crop-wise survey of silkworm diseases from 25 farmers (five farmers from five villages), who each had a separate rearing house, were progressive and had a capacity of rearing at least 100 disease free layings (dfls) in each crop. Disease incidence was expressed in percentage and calculated taking into consideration 40,000 larvae per 100 dfls. Crop-wise silkworm disease mortality data were correlated with meteorological data. Data collected from the continuous survey conducted in the district during 1992–2011 revealed that there was no set pattern of occurrence of silkworm diseases. However, maximum mortality (up to 30%) of silkworm due to diseases in all the seasons occurred mainly due to grasserie, as relative humidity remains high for most part of the year in this area. However, other than grasserie, for most of the period, disease incidence was below 10%. This observation of the dominance of grasserie over other diseases in causing silkworm mortality calls for renewed emphasis on the preventive measures and development of disease forecasting models, for disease control. Another observation was that since 1993, pebrine, the deadliest disease of the silkworm, has not been reported from the farmers’ fields.

A large and varied group of insects attack crops of the tropical farmer, and carry various disease-causing organisms to him and his animals. The control of these agricultural pests, and vectors of human and animal diseases relies mostly on chemical pesticides. However, investigations show that alternative methods such as biological control and resistant crop varieties are available, which may be used in the reduction of pest infestation, resulting in an Increase in food production by the African farmer.

Among the eight entomopathogenic fungi tested against the termite, Odontotermes obesus (Rambur), five fungal pathogens viz., Beauveria bassiana (Bals.) Yuil, Metarhizium anisopliae (Metsch.) Sorokin var. anisopliae, M. flavoviride Gams Rozsypal var. minus, Paecilomyces lilacinus (Thom) Samson and P. fumosoroseus (Wize) Brown & Smith, were pathogenic. Three other fungal pathogens viz. Verticillium lecanii Zimm, Paecilomyces farinosus (Holm, ex Gray) and Nomuraea rileyi (Farlow) were not pathogenic. B. bassiana was the most effective pathogen against termites, followed by M. anisopliae, M. flavoviride, P. lilacinus and P. fumosoroseus. Workers minor, of the three morphogenetic forms of O. obesus, were the most susceptible, followed by workers major and soldier caste. Bioassay on isolates of two most virulent termite pathogens, B. bassiana and M. anisopliae revealed that B. bassiana isolate Bapatla was the most effective fungal pathogen with the lowest LC50 (9.98 × 104 conidia/ml)

The differential attraction by 2 pigeonpea cultivars has been tested through the oviposition behaviour of Heliothis armigera females in a standardized laboratory assay. Seedlings of a susceptible variety (PPE-50) are under choice conditions significantly more attractive at a distance, and without contact allowed other than those of the resistant variety (PPE-45). The volatile signal is contained in the hexane extract from PPE-50 leaves, as shown in the oviposition assay, and after vacuum distillation is present in the more volatile fractions of the mono- and sesquiterpenoids. These compounds, which are also contained in the hexane extracts of 2 more pigeonpea cultivars, a check of medium susceptibility (T-21) and a wild relative (Atylosia scarabaeoides), were compared by capillary gas chromatography. The 4 pigeonpea varieties were characterized by their specific aromagrams, a method which may also advantageously be used in pigeonpea breeding programs.

The location of olfactory and gustatory sense organs in the larvae of the American bollworm, Heliothis armigera, have been studied using the scanning and transmission electron microscopy. The olfactory chemoreceptors of the larvae are located on the antennae, mostly on the top of the second antennal segment in the form of two trichoid sensilla, two basiconic sensilla, two styloconic sensilla, campaniform sensilla and a uniporous peg sensillum. The third antennal segment bears one basiconic sensillum and two styloconic sensilla. The gustatory sense organs are located on the mouthparts including the labrum, mandibles, hypopharynx, maxillary palps and labium. Trichoid sensilla have been located on the labrum. Epipharyngeal setae as well as long short spines are located in the epipharyngeal membrane. The basal segment of the maxillary palp bears three trichoid sensilla and one campaniform sensilla. The maxillary palp also bears four styloconic sensilla on the distal portion of the lateral protuberance and one styloconic sensillum at the apex of the medial protuberance. Close to the bases of the protuberances, there are three basiconic sensilla and one campaniform sensillum. The third apical segment of the maxillary palp carries three campaniform sensilla on its lateral side, while on its top, eight small basiconic sensilla are distributed.

Sweetpotato weevil, Cylas formicarius formicarius F is the most destructive pest of sweetpotato, Ipomoea batatas in tropical and subtropical regions. The larvae and adults feed on sweetpotato roots and crowns. For the past 12 years we have been screening sweetpotato germplasm for resistance to this pest in order to breed an agronomic cultivar with weevil resistance. Resistance screening is conducted at AVRDC and Penghu island in autumn and summer, respectively. Germplasm is planted between heavily infested source rows maintained in a weevil nursery. Roots are harvested, sliced into thin pieces, and the number of insects (larvae + pupae + adults) per unit weight, as well as the weight of damaged and healthy root slices, are recorded. The resistance rating is based mainly on the number of insects found in the root. Considerable differences in resistance rating are observed from location to location and season to season. Even at one location, tremendous differences are observed in weevil infestation of a particular entry among the replicates. Although over 1000 sweetpotato accessions have been screened, we have not found any that is consistently less damaged over several seasons at either location. Our recent screening of a population of I. trifida × I. batatas crosses show certain hybrids with high yield and low weevil infestation. These hybrids need to be evaluated further to confirm their resistance.

The shootfly, Atherigona soccata Rondani, is a major seedling pest of sorghum in many areas of tropical Asia, Africa and Mediterranean Europe. A chronological review of the progress made in various programmes on the screening techniques (natural and artificial) with artificial diets, sources, stability and mechanisms of resistance, bases (physico-morphological and biochemical factors) of resistance, inheritance and breeding for resistance is made. Many resistant varieties have been identified and sources of resistance utilized in breeding programmes to transfer resistance in high yielding background are listed. In addition, the glossy and trichome traits identified is sorghum cultivars are also reported. Glossy leaf surface and trichomes are frequently associated with shootfly resistance.

Sperm are transferred from male to female tsetse, as in most insect species, within a spermatophore. The spermatophore of the tsetse species, Glossina morsitans morsitans Westwood (Diptera: Glossinidae), is highly organized, and can be visualized as a sac deposited in the uterus of the female tsetse. The wall of the spermatophore comprises two layers, whose components are strikingly similar to those of the secretions made by the male accessory reproductive glands. Dense aggregates of material, matrix filaments, and clusters of granules predominate in both. An ultrastructural study of these components is reported in this paper.

Graminaceous crops are attacked by lepidopterous stem-borers all over the world causing severe crop loss. Chemical control of stem-borers is difficult and biological control is preferable for peasant farming systems. The most important genera are Diatraea, Chilo, Eldana, Sesamia and Busseola. Their natural enemies include egg, larval and pupal parasites and predators. The parasites are cued by different stimuli, some to host plant, others to borer tunnels or frass. Biocontrol was first attempted against Diatraea spp. in the New World where D. saccharalis is now under fair control in several countries. In the Old World attempts have been made to control C. sacchariphagus and E. saccharina without much success. In East Africa releases of exotic parasites against B. fusca, S. calamistis, C. partellus and E. saccharina have not been very successful and further work is suggested. Leguminous crops suffer from attacks of lepidopterous pod-borers. The most damaging species are Etiella zinckenelia, Maruca testulalis, Cydia spp. and Lampides hoeticus. There are relatively few records of important parasites and fewer still of predators, however, large parts of the world are still unsurveyed for natural enemies. Successful control using introduced parasites has been reported from Canada against C. nigricana and Mauritius against E. zinckenelia and M. testulalis. There appears to be scope for introductions of Caribbean parasites into Africa.

The life cycle of the koinobiont endoparasitoid Platygaster diplosisae Risbec was investigated to assess its suitability as a biological control agent of the African rice gall midge Orseolia oryzivora Harris & Gagné. Screen house and laboratory experiments were conducted in 2008 under ambient conditions in Ibadan, Nigeria. Morphological characteristics of the parasitoid's immature stages were observed, and its life cycle parameters were measured. The parasitoid's average egg incubation period was 12.9 days, and on average, 67.3% of eggs hatched. Three instars occurred, with average developmental durations of 2.2, 0.5 and 2.5 days for the 1st, 2nd and 3rd instars, respectively. Pupal development took 6.7 days until adult emergence. Pre-oviposition period averaged 12.1 h, and a female laid on average 95.2 eggs, with a mean oviposition period of 3.5 days. The longevity of males and females was 3.0 and 4.1 days, respectively, without food; longevity was extended when honey and water were provided. Mating and oviposition behaviours were recorded, and a sex ratio of eight females to one male was found in parasitoid progeny. The parasitoid had a total developmental period of 27.3 days, which is about 5 days longer than that of its host. In conclusion, P. diplosisae can play an important role in the biological control of O. oryzivora on rice, and should be conserved in African rice production systems.

A two-year survey was undertaken to determine the trypanosomosis risk of Egbe, a town in Kogi state of Nigeria, and its suitability for cattle raising. Tsetse flies were trapped using biconical traps and examined for trypanosome infection, and blood samples from cattle and goats were examined by blood film and haematocrit centrifugation technique (HCT) for trypanosome parasites. No infection was detected from the 152 Glossina palpalis palpalis and 52 G. tachinoides dissected over the period. Blood film examination of 181 cattle and 14 goats also gave negative results. Examination by HCT of 21 cattle from a local abattoir showed 14.3% Trypanosoma vivax infection, but the 10 resident cattle and 14 goats similarly examined were negative. The average age of the caught flies, determined by mean wing fray values (for males) and ovarian analysis (for females), was between 11 and 14 days, which is too low to sustain an infective population. Coupled with the absence of G. morsitans submorsitans, the most important vector of animal trypanosomosis in Nigeria, and the disappearance of large game from Egbe, our results would point to the area being a low trypanosomosis risk one.

The stemborers Busseola fusca (Fuller) and Chilo partellus (Swinhoe) cause the highest economic damage to maize and sorghum in Zimbabwe. A number of studies on stemborer bioecology and management in Zimbabwe have been conducted, but most are still incomplete. The more important of these are studies on life history, incidence and distribution patterns, host plants, yield losses, chemical control, cultural control, host plant resistance, the use of sex pheromones, and biological control. These are discussed here in detail, and areas where further research is needed are pointed out. As part of an integrated strategy for managing stemborers in Zimbabwe, an exotic braconid larval parasitoid, Cotesia flavipes Cameron, has been released in the lowveld area and prospects for its establishment appear to be good. However, this establishment might be curtailed mainly by the inability of Co. flavipes to adapt to the seasonal carryover mechanisms utilised by the indigenous Cotesia sesamiae (Cameron).

The effect of light on the development of the angoumois grain moth, Sitotroga cerealella, was studied. Three different light conditions, i.e. continuous light (LL), continuous darkness (DD) and antural illumination (LD), were used.

Eggs bred under LL system showed the shortest mean incubation period, 3.27 and 4.66 days after one and four generations, respectively. The light had no effect on egg hatchability. The number of larvae that reached the adult stage under LL was less (33–36%) than under LD (37–40%) or DD (38%). The fertile females begin egg laying within 0.9 to 2.3 days after mating under all light systems. The shortest period (0.9) was shown under continuous light. The least oviposition period 4.4 and 4.5 was obtained under LL, while the longest period (6.4 and 5.7 days) was obtained under LD, after one and four generations, respectively. The light has no effect on the post-oviposition period. The longest life span of adults was recorded under LD and the shortest under LL. The females bred under LL, laid the least number of eggs (85–87 eggs), while those bred under LD and DD laid the highest number (128–130 for LD and 113–146 for DD, respectively).

Scirtothrips dorsalis Hood is a polyphagous species and an important sucking pest of tea (Camellia sinensis) (Theaceae). The fitness traits of S. dorsalis on two alternative host plants: Capsicum annuum L. (chilli) (Solanaceae) and Ricinus communis (castor oil plant) (Euphorbiaceae) and on C. sinensis and corresponding levels of defence enzymes was studied. The study revealed that C. sinensis is the more suitable host of S. dorsalis based on faster development (13.6 days) compared to the alternative hosts, C. annuum (15.5 days) and R. communis (16.7 days), a higher fecundity (C. sinensis: 11.4 eggs; C. annuum: 9.7 eggs; R. communis: 8.6 eggs), and superior egg hatchability (C. sinensis, 92.6%; C. annuum: 82.5%; and R. communis: 74.6%). The host-based variation in the fitness traits of S. dorsalis corroborated in light of differential activity of three major detoxifying enzymes, such as the general esterases (GEs), glutathione S-transferases (GSTs), and cytochrome P450 mediated monooxygenases (CYPs). Densitometric analysis of GEs showed five esterase isozymes (EST I–V) with retardation factor (Rf) values of 0.17, 0.22, 0.27, 0.35 and 0.52, respectively. The pixel density, and accordingly the profile height, varied in different host-specific S. dorsalis. A significant variation of the quantity of these enzymes was also apparent in the insect when reared on the three hosts. A 2.4 and 2.7, 1.6 and 2.0, and 2.0 and 2.3-fold higher GEs, GSTs and CYPs activity on the two non-tea hosts possibly signify a predisposition of the species for higher tolerance to insecticides, enabling the pest to switch to tea where synthetic insecticides are routinely used.

In this study, Coccinella septenipnnctata was efficient in controlling Aphis gossypii populations on cucumber in the greenhouse. This efficiency was a function of the predator/prey ratio and the initial aphid density at the time of release of the predator. Prey density had a large influence on the fecundity and establishment of this coccinellid in the greenhouse.

In West and Central Africa, panicle-feeding mirid bugs, particularly Eurystylus oldi Poppius (Hemiptera: Miridae), are major pests of improved sorghum cultivars. Population dynamics of panicle-feeding bugs were studied on the sorghum cultivar ICSV 197, sown on eight dates each year from 1992 to 1994 at Samanko, Mali. Relationships between weather factors and abundance of paniclefeeding bugs were examined for the three most commonly found mirids, E. oldi, Campylomma spp. and Creontiades pallidus Rambur (representing on average respectively 58, 39 and 2% of all mirid species). Although only one generation of E. oldi could develop between flowering and grain maturity on a particular panicle, there were three successive generations each year during the extended grainmaturing period in the experiment with eight sowing dates, with a major peak in abundance in early October, followed by a gradual decrease until late November. Abundance of Cr. pallidus peaked in late October, while that of Campylomma spp. showed no relationship with date of sowing.

An increase in abundance of E. oldi nymphs (y1) was favoured by high precipitation, reduced maximum temperature and high minimum relative humidity during and 2–3 weeks before the grainfilling period [a strong negative relationship was found with the number consecutive days without precipitation from 78–88 days after sowing (das) (x1): y1 = −11.7x1 + 149.3 (r2 = 0.67)]. The abundance of Cr. pallidus (y2) was correlated with wide temperature ranges and low precipitation during the same periods (notably precipitation frequency from 75–91 das: x2): y2 = −2.28x2 + 24.6 (r2 = 0.65). The abundance of Campylomma spp. (y3) was negatively correlated with amount of rainfall between 19–32 das (x3): y3 = −3.82x3 + 705.9 (r2 = 0.49). Reasons for these trends are suggested and their possible application for management of panicle-feeding bugs discussed.