The biological activity of pirimiphos-methyl (20% e.c.) and a chlorpyriphos-methyl/deltamethrin (20/1% e.c.) formulation applied at different concentrations to glass, jute, plywood and mud surfaees against Prostephanus truncatus (Horn) and Sitophilus zeamais (Motsch.), was compared over a period of 18 weeks. The bioassays were conducted at 28°C and 70% r.h., 1, 4, 7, 14 and 18 weeks after treatment. Insect mortality was significantly influenced by the type of surface, the insecticide concentration, the age of the insecticide deposit and the interactions between these factors. P. truncatus was more susceptible to chlorpyriphos-methyl/deltamethrln deposits than S. zeamais. Amongst the different surfaces, glass retained the highest persistence, followed by jute, plywood and mud against P. truncatus. The insecticide deposits on jute were the most effective in controlling S. zeamais.

Larvae of the Mediterranean flour moth (Anagasta kuehniella Zeller) cause major losses in stored grains throughout the world. In this study, pouterin, a lectin-like protein isolated from Pouteria torta (Mart.) Radlk. seeds, was tested for activity against A. kuehniella larvae. Pouterin did not produce significant effects on survival; however, at c. 1% w/w concentration in artificial diet, it produced a 71.4% reduction in average weight of the larvae. A dietary utilisation assay showed a reduction in efficiency of conversion of ingested food, efficiency of conversion of digested food and approximate digestibility, as well as an increase in metabolic cost. Pouterin increased the level of trypsin in the midgut and faeces of larvae. We conclude that pouterin possesses an insecticidal effect against A. kuehniella larvae and this effect may be mediated by the binding of pouterin to chitin components of the peritrophic membrane, or glycosylated proteins in the insect midgut.

The citrus leafminer (CLM), Phyllocnistis citrella Stainton causes injury to citrus and related species in the Rutaceae family. The damage that the CLM larvae can cause is significant in citrus plantations. We tested two citrus cultivars — ‘Kinnow’ (Citrus reticulata Blanco) and ‘Fairchild’ (a hybrid of Citrus reticulata Clementine x Orlando Tangelo) — to quantify CLM larvae infestation and effect on the physiology of the citrus cultivars. We then compared the CLM larval weight with its associated damage. To calculate infestation level, mine area and total leaf area, we used the image analysis technique. The infestation level of CLM was higher in ‘Fairchild’ than in ‘Kinnow’ cultivar of citrus. For both cultivars, larval weight of CLM was directly proportional to the amount of mines generated. Taken together, the results of this study suggest that the mines that CLM larvae generate pose significant effect on the net photosynthetic rates and water use efficiency of citrus nursery plants. These results will help improve our understanding of the interaction between CLM and citrus nursery plants and effect of the pest on the yield potential of the crop.

The penetration of adult Sitophilus zeamais Motschulsky through maize grain bulks (0.75 m deep), treated with Protect-It®, a diatomaceous earth (DE) at 0, 0.05, 0.1 and 0.2% (w/w), was determined 12 weeks after weevils were released at the upper surface of the grain. Maize was stored in columns in polyvinyl chloride (PVC) pipes, under controlled conditions of 26±2°C and 70±10% RH. Grain samples were collected from various pre-determined depths and the numbers of S. zeamais adults counted. Differences in insect numbers between treatments and at different depths from which samples were collected were highly significant (P<0.001). The bottom 2–3 layers (0.65–0.75 m deep) had significantly more insects than the upper layers for all the DE concentrations. No significant differences in total insect numbers (live+dead) were found between the DE concentrations. Dead S. zeamais weevils were found at the bottom of grain treated with Protect-It®, indicating that insects can penetrate through DE-treated grain 0.75 m deep but then subsequently die. There was no strong evidence that DEs admixed with bulk grain restrict S. zeamais movement within the grain.

Local West African strains of Sitophilus oryzae (L.) and Tribolium castaneum (Herbst) were placed in 200 g of wheat samples, one species after the other, during 6 weeks. The rate of infestation for S. oryzae was 6, 12, 24 or 48 pairs of adults, while it was fixed to 20 for T. castaneum. The generation of S. oryzae was killed by fumigation before T. castaneum infestation of the grain samples. The loss in dry weight and the frass production were recorded at the end of each rearing period of time for each species.

The dry matter loss caused by S. oryzae was highly correlated with the rate of adult infestation and measured as high as 600 mg per infesting pair of weevils. The frass production for both S. oryzae and T. castaneum was highly correlated with the rate of infestation by weevils only. For S. oryzae, the average frass production was about 60 mg per adult pair, while for T. castaneum it was variable from 27 to 44 mg per pair of the primary infestation level by the weevils.

The importance of these results is discussed in relation to standard loss assessment methods when there are several infesting species and particularly when there is a preponderance of secondary species over primary species.

Okra, Abelmoschus esculentus (L.) Moench, is an important vegetable crop grown throughout the tropical and temperate regions of the world. Spotted bollworm, Earias vittella (Fab.), is one of the most important insect pests of okra. The effects of insecticides (cypermethrin, imidacloprid, carbaryl and neem oil) were studied on the fitness of the F1 generation of E. vittella by a demographic method. Life table was constructed from the eggs obtained by the surviving individuals that had ingested insecticides. Survivorship and expectancy was highest with the commencement of age and gradually decreased with the progression of age in the treatment groups and control. However, it was reduced in the treatment groups in comparison to control groups. Highest numbers of unhatched eggs (17%) were recorded with imidacloprid and cypermethrin treatments, whereas all the eggs hatched in control groups. Larval mortality was high in the initial instars as compared to late instars. Potential fecundity was significantly reduced to 94 females/female/generation treated with cypermethrin as compared to 256 in the untreated females. Developmental time of pre-pupa and pupa was significantly decreased with cypermethrin treatment. The intrinsic rate of increase was reduced to 0.0201 females/female/day in cypermethrin groups as compared to 0.046 in the control groups. The generation time was 33.27 days in the control, which was reduced to 26.78 days with carbaryl treatment and was increased to 37.5 days with neem oil. Insecticides cause adverse effect on the surviving generation of E. vittella, and may be incorporated as a valuable component in the integrated management of E. vittella on okra.

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.

Since it was first reported in Tanzania in 1981 the Larger Grain Borer (LGB) has spread from a small area in the northwest of the country to 17 of the 20 regions. Only in the extreme south, along the Mozambique border, has the pest not been found. It has also become established in Kenya, Burundi, Togo and Benin.

LGB can cause very high weight loss in farm stored maize and dried cassava, commodities on which it is able to breed. After 5 months storage during the dry season in western Tanzania, mean losses of 9% were found, a much higher level than losses of less than 1% which would be expected in LGB-free areas in East/Central Africa.

Application of 0.5% permethrin dust at 2.8 ppm provides excellent protection against LGB when applied to loose maize grain for 1 year. However, the storage of shelled maize predisposes towards the development of Sitophilus species which can result in high losses being sustained. A “cocktail” of permethrin and pirimiphos-methyl, applied at 3.3 and 17.7 ppm respectively, successfully controls all storage pests and is currently being used in an extensive control campaign in Tanzania.

A multi-donor funded control and containment campaign, co-ordinated by FAO, has been in operation in Tanzania since 1984. The programme is comprised of a training element for agricultural staff and several field extension campaigns which assist with insecticide distribution and with dissemination of information to farmers. The primary objectives of the programme are to reduce farm storage losses and to contain LGB within the areas it is now found. In some regions, where LGB is relatively isolated, attempts are being made to eradicate it.

In situ field level mass production of Amsacta albistriga nucleopolyhedrovirus (AmalNPV) was achieved at Pavagada (Karnataka, India) during September 2004. The yield of virus mass produced in situ in the field was 5.05 times greater than that when produced in the laboratory. This technique is farmer-friendly, easy to execute and much cheaper than laboratory production, having the potential to be used for the mass production of NPV of gregarious pests that occur in large numbers.

Despite considerable efforts in developing sweetpotato cultivare resistant to two species of sweetpotato weevils, Cylas formicarius and C. puncticollis, no cultivar has yet been bred, utilizing previously identified sources of resistance, and cultivated in any appreciable area for weevil control. Escape, nonpreference, tolerance, and antibiosis, and the possible mechanisms involved do not seem to exist in the sweetpotato plant or cannot be utilized because of the peculiarities of ecology and host plant relationship of the weevils. Since weevil infestation of roots does not adversely affect the growth and reproduction of sweetpotato plants, it is possible that weevil resistance to root infestation does not exist in this crop.

The development of resistance to insecticides in insect pests is an important and increasing problem. As insecticide use increases in tropical areas, the numbers of resistant insect strains will increase.

The adverse effects of insecticide resistance include crop losses, increased production costs, increased environmental hazards, and socio-economic problems. The increasing difficulties and costs of discovering and developing new insecticides together with the widespread occurrence of resistant strains of insect pests means that insecticides are a limited resource that must be conserved. Methods of conserving insecticides include sensible management of their use and the implementation of IPM programmes.

The problems of insecticide resistance and strategies for minimizing and managing resistance in tropical areas are discussed using examples of insect pests of stored products, cotton, rice and bananas.

Among the important constraints to vegetable production in Africa are the lepidopteran pests, in particular Helicoverpa armigera (Hb.) and Plutella xylostella (L.) which cause direct yield loss as well as cosmetic damage. Egg parasitoids, especially Trichogramma spp., shown promise as biocontrol agents against both species in previous studies. In Africa, surveys have so far recorded 18 species of Trichogramma, eight of Trichogrammatoidea and seven of Telenomus besides one species each of Baryscopus and Oencyrtus. For effective utilisation of egg parasitoids in vegetable ecosystems in Africa, the experience gained elsewhere should be suitably utilised, and complementary research undertaken. This paper examines the scope for use of egg parasitoids in Africa, focusing on five research areas. Firstly, surveys should be undertaken to collect, characterise, and catalogue the different species and strains of egg parasitoids occurring in the region. Secondly, the pest status of target Lepidoptera and the potential demand for use of egg parasitoids in the major ecologies should be assessed. Thirdly, the local and/or exotic species/strains with good potential to control H. armigera and P. xylostella need to be identified, and fourthly, analyses aimed at selecting appropriate mass production and delivery systems for Trichogramma use in major vegetable crops should be undertaken. Finally, optimisation of inundative release strategies should be researched on. The scope for research collaboration within Africa and internationally is discussed.

Culex quinquefasciatus Say, a widely distributed mosquito in tropical and subtropical areas, is the most important vector of the filarial parasite Wuchereria bancrofti, the causative agent of lymphatic filariasis. In India, filariasis is endemic in 17 States and six Union Territories, putting about 553 million people at risk of infection. Vector control, which aims to prevent pathogen transmission through interventions targeting adult mosquito vectors, is a significant component of control of the disease. Chemical-based control represents a chief strategy in the management of mosquito vectors; however, continuous application of insecticides has led to the development of resistance in many mosquito vectors around the world. The current study aims to observe the variability of expression of carboxylesterase isozymes that play a role in detoxifying insecticides into non-toxic compounds, in different life stages of Culex mosquitoes, to understand levels of insecticide susceptibility that may be used in integrated mosquito management for efficient vector control. C. quinquefasciatus were collected from different localities of sub-Himalayan West Bengal, India, and adult and larval bioassays were performed against one organophosphate insecticide (chlorpyrifos) and two synthetic pyrethroid insecticides (deltamethrin and lambda-cyhalothrin). The activity of α- and β-carboxylesterases (quantitative assay) were measured in larvae and adults of C. quinquefasciatus using a microplate assay, and measured qualitative expression by native polyacrylamide gel electrophoresis. The study shows a differential activity of α- and β-carboxylesterases both in quantitative and qualitative assays. The quantitative assay reveals that larvae exhibit a 12.2-fold higher level activity of α-carboxylesterase and about 5.0-fold higher level of activity of β-carboxylesterase than adults. Some carboxylesterase isozymes, i.e., α-Est I-IV, α-Est VII and α-Est XI-XV were exclusively expressed in larvae, whereas α-Est V-VI and α-Est IX were expressed only in adults. In larvae, all β-Est I-IX were expressed, while in adults only β-Est IV-V was expressed. The results of adult and larval insecticide bioassay are also as per the above findings showing an LC90 value of 0.017 ppm, 0.097 ppm and 0.072 ppm in the larva, and LC90 value of 0.0015 ppm, 0.721 ppm, 0.364 ppm in adults against chlorpyrifos, deltamethrin and lambda-cyhalothrin, respectively.

The importance of rice in West Africa and the problem posed by pests were highlighted. Stem-borers are regarded as major insect pests of rice and available information on yield losses attributable to insect pests in general and stem-borers in particular, was reviewed. Damage caused by stem-borers usually results in “dead hearts” and “white heads” though other effects including a synergistic interaction between stem-borers and rice blast have been recorded. Survey methods and sampling of rice stem-borers were discussed and brief descriptions on distribution, behaviour and biology of the major rice stem-borers namely, Chilo spp., Maliarpha separatella, Scirpophaga spp., Sesamia spp. and Diopsis spp. were given. Current control tactics under investigation in West Africa include chemical, cultural and biological methods.

A new genus and a new species of the parasitoid wasp, Napo townsendi (Hymenoptera: Braconidae: Euphorinae: Dinocampini), is described from the Yanayacu Biological Station in Napo Province, Ecuador. The new genus and species is diagnosed and compared with the most closely related genus Betelgeuse Shaw and other Dinocampini. While first discovered by yellow bowl and Malaise trapping, it has more recently been discovered that males of N. townsendi can be found preferentially perching on the leaves of seedlings of the asteraceous tree Dendrophorbium lloense (Hieron) C. Jeffrey.

The larval Malpighian tubules of Sarcophaga ruficornis Fab. consist of two types of cells, namely principal and stellate cells. The principal cells are characterized by a large euchromatic nucleus, well-developed basal plasma membrane infoldings associated with mitochondria and prominent luminal microvilli containing mitochondria with well-developed cristae. The central cytoplasm of the cells contains clear vacuoles, lysosomes, mineral concretions or spherocrystals, lipid droplets and peroxisomes. The stellate cells are thin with extremely short basal plasma membrane infoldings and luminal microvilli devoid of mitochondria. The ultrastructural features of the principal cells show the characteristic of transporting cells engaged in water and ion transport. The cells are separated by septate junctions. The tubules are richly supplied by the tracheae.

Participatory rural appraisal was undertaken in 70 villages in India and Nepal, covering 1185 farmers to generate baseline information on the current plant protection practices. The study revealed that 93% of the farmers in India and 90% in Nepal had adopted chemical control for the management of various insect pests in different crops; however, less than 20% of the farmers expressed confidence on their efficacy. In India, 52% of farmers get their plant protection advice from pesticide dealers, while in Nepal, the majority of the farmers (69%) make their plant protection decisions through agricultural officers. A majority of the farmers (73% in India and 86% in Nepal) initiate the plant protection based on the first appearance of the pest, irrespective of their population, crop stage and their damage relationships. About 50% of the farmers in India and 20% in Nepal were not using any protective clothing while spraying. Health problems associated with the application of plant protection chemicals were reported by farmers. The cost of plant protection on various crops ranged from 7 to 40% of the total crop production cost. Though integrated pest management (IPM) has been advocated for the past two decades, only 32% in India and 20% in Nepal were aware of IPM practices. IPM implementation in selected villages brought a 20–65% reduction in pesticide use in different crops. The vegetable samples analysed for pesticide residues revealed the presence of residues.

A rearing procedure for the pre-imaginal stages of the flea beetle Podagrica sjostedti (Jac.) was developed in the laboratory at room temperature (24–28 °C) relative humidity of 79–92% and a 12 h photoperiod. Adults were reared in a designed oviposition cage that was developed from a transparent plastic vial, which allowed the eggs to be seen. Eggs were kept in an incubation dish for eclosion, which happened within 7–11 days. One-day-old larvae were used to infest two okra seedlings (4 weeks old each) planted in 200 g sterilized soil and moistened every other day with 16.6 ml of water to half-filled capacity. Larvae were retrieved by washing off infested soil through 3 and 1 mm mesh and then a muslin cloth. Pupae were reared in a jar containing moistened sterilized soil. This procedure and the specially designed medium permitted, for the first time, a study of the pre-imaginal stages of P. sjostedti. Its life cycle consists of an egg stage (mean length and width of 0.10 and 0.05 mm) and three larval stages (mean head-capsule width of 0.21, 0.36 and 0.49 mm for the first, second and third instars, respectively): pre-pupa, pupa and adult. The length of pupae averaged 3.10 mm and the width was 1.40 mm. The mean life cycle was 37 days. The mean pre-oviposition period was 7.7 days, oviposition period was 49.2 days and post-oviposition period was 6.5 days. Females were significantly larger than males and the sex ratio (female: male) was 1.52:1.

This paper describes briefly four different locust species that constitute potential widespread danger to agriculture and pasture in the eastern, central and southern Africa region. Particular reference is made to the red locust, Nomadacris septemfasciata Serville which mostly feeds on monocotyledonous plants. Reference is also made to the African migratory locust, Locusta migratoria migratorioides R&F; the brown locust, Locustana pardalina Walker; and the desert locust, Schistocerca gregaria Forskal. There were frequent reports of damage to cereal crops by the red locust during the most recent plague of the 1930's. However, since that time only a few yield loss data are available owing, primarily, to the fact that locust infestations have mostly been irregular and confined within their natural breeding areas, away from crop land. The paper provides general background information that should enable evaluation of locust incidence in the region and assessment of consequent cereal crop production losses.

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.