Cowpea, Vigna unguiculata (Walp) and beans, Phaseolus vulgaris are attacked by several insect pests worldwide. The pests include economically important borers, the control of which often requires the use of more than one tactic. In Africa, the major borer species of cowpea is Manica vitrata Fab. (syn. M. testulalis [Geyer]); in Southeast Asia and eastern Africa the beanfly or bean stem maggot complex, Ophiomyia spp., is important on beans. The bean borer, Etiella zinckenella (Treitschke), is also of considerable importance in Asia. In South America Epinotia apotema (Wals) and Cydia fabivora (Meyrick) are the most important borers on beans, while Helicoverpa armigera (Hïbner) and M. vitrata to a lesser degree are important on beans in some parts of Africa. Presently, only chemical control provides complete protection against crop borers, but despite its usually favourable cost-to-benefit ratio, insecticide use is not a sustainable option. Other tactics such as cultural control, host plant resistance and the use of beneficial organisms are more dependable in the long-term. They form the core of the new vision for environmentally friendly pest management, or bio-intensive pest management, which minimises the use of synthetic insecticides. In recent times, research efforts directed at these measures have been intensified. This paper discusses the various interventions and presents different IPM models on how they can be combined to optimise the control of borers. Suggestions are made on the future outlook of IPM on cowpea and beans.

Populations of larvae and pupae of the African rice gall midge, Orseolia oryzivora Harris & Gagne (Diptera: Cecidomyiidae), and two parasitoids, Platygaster diplosisae Risbec and Aprostocetus procerae (Risbec)[= Tetrastichus pachy diplosisae Risbec], were recorded in replicated experiments on farmers' fields at Karfiguéla, Burkina Faso in the 1992 wet season and the 1993 dry season. In each season, four plantings were made at 14-day intervals and samples taken at weekly intervals for 10 weeks. Gall midge populations in the wet season developed through three distinct phases: an initial slow increase, followed by a period of rapid increase coinciding with maximum tillering, and then a final decline. On average, the highest midge populations and highest levels of parasitism developed in the later plantings. During the dry season midge infestations were low and no parasites were detected.

Pesticide spray thresholds, as a component of Integrated Pest Management, must be integrated with the world of smallscale farmers if they are to be useful to them. The capacity and desire to spray have specific features of significance for threshold control. Threshold use may be encouraged by maximising the divisibility of pesticide technology. Farmers' perception of thresholds, often subjective and personal, may be enhanced by information learned from outsiders, as complementing, rather than supplanting, their existing knowledge and experience.

Crop protection problems of smallholders farming maize in the Chokwe Irrigation Scheme in southern Mozambique were investigated in a long-term field study programme during 1984–1990. Downy mildew, Peronosclerospora sorghi (Weston & Uppal) C.G. Shaw, maize streak virus, stemborers (mainly Chilo partellus Swinhoe) and the multimammate rat (Praomys natalensis Smith) were the most important, with the first three showing highest incidence in the warm rainy season (October-March). Average percentage infestation of maize at 30 days after emergence in four successive rainy seasons were 11% for maize streak virus, 16% for downy mildew and 26% for stemborers. The multimammate rat was most abundant at the beginning of the cool, dry season (April-May). Maize streak virus attacks were aggravated when there was rainfall in the preceding cool, dry season. High rainfall in the early part of the warm season increased the likelihood of outbreaks of the multimammate rat in the subsequent cool season. Early sowing decreased the intensity of downy mildew and stemborers, but not of maize streak virus. In on-farm trials involving varieties with combined tolerance to maize streak virus and downy mildew, ESR-DMR-W from IITA (Nigeria) produced 32% more grain while CW-1, a locally bred improved variety, produced 31% more than the local unimproved variety.

The phenotypic stability of resistance to the stemborer, Chilo partellus and grain yield in 10 newly developed sorghum hybrids namely HYD-1, HYD-2, HYD-3, HYD-4, HYD-5, HYD-6, HYD-7, HYD-8, HYD-9 and HYD-10, and two local checks, Serena (tolerant) and IS-1044 (resistant), were evaluated for seven seasons at the International Centre of Insect Physiology and Ecology (ICIPE) Mbita Point Field Station and Ungoye Field Site in western Kenya. Two stability parameters were determined: (1) The linear regression (b1) of an entry mean on an environmental index, and (2) the deviation from regression (S2d). The significance found for the linear component of environment implies that the variation over the different environments is adequate to test for cultivar stability. Hybrids HYD-1, HYD-5, HYD-8 and HYD-10 were identified as the most suitable genotypes for future commercial production.

Studies on losses in yield of rapeseed, Brassica campestris cv. Brown Sarson, caused by the mustard aphid, Lipaphis erysimi (Kalt.) were conducted under natural and artificial conditions. Based on the experiments on the influence of aphid exposure to the crop on aphid number and seed yield and the effect of varied aphid population at flowering/pod initiation stage and artificial release of aphids at 10-day intervals starting from 40 days of sowing on the plant height, number of siliquae per plant, number of primary branches, seed yield per plant and 1000-grain weight, a positive correlation between length of aphid exposure to the crop and aphid population was found. A negative relationship between aphid population, length of aphid exposure and seed yield was observed. An inverse and significant relationship existed between parameters contributing to yield loss and losses in seed yield. However, this relationship was not significant in siliquae per plant and 1000-grain weight. A similar relationship was observed in artificial infestation.

The effect of maternal crowding on the offspring sex ratio of a cereal aphid parasitoid Lysiphlebus delhiensis (Subba Rao & Sharma) (Hymenoptera: Braconidae) was examined. Increasing the number of mothers per host-patch always increased the proportion of males in the population (p). The extent of variations in p at different levels of maternal crowding was compared with the prediction of the Hamiltonian LMC model, i.e. p = (n-1)/2n, where n = number of mothers/host-patch. The perception of trace odours of conspecific females induced haploid oviposition. Differential mortality of the larvae by sex in superparasitised hosts, shifting the p towards sons has been discussed. The inversely parasitoid-density-dependent p indicates that for obtaining maximum number of female progeny, the ratio of female parasitoid to the host in mass breeding should not be less than 1:100 at a time.

Larval growth of the two main maize stemborers, Busseola fusca (Fuller) (Lepidoptera, Noctuidae) and Eldana saccharina Walker (Lepidoptera, Pyralidae), in Côte d'Ivoire was studied as a function of temperature sums. Tunnelling by unit weight was similar for both species. Early attacks by B. fusca (infestation until 17 days after maize emergence) resulted in deadhearts or in growth reduction. A relation combining the date of infestation, the level of attack and the development stage of maize explains the observed damage. Later attacks by both borers result in differences in damage, which are related to the larval distribution in the stem, the compensation between maize yield components, and also to the presence of a more or less active larva in the cavity.

Dormancy is described for adults of the stalk-eyed fly, Diopsis longicornis Macquart (Diopsidae: Diptera) in the tropical savanna of coastal Guinée, West Africa. Populations of diopsids maintained themselves within each chosen refugium throughout the dry season unless the site dried up. Sex ratio within the populations at each refugium remained constant throughout the dry period. Slightly more females than males were found (56%), and of these only 0.8% were gravid. Movement of stalk-eyed fly adults from the rice field to the refugia corresponded with the end of the rice cropping period (stage of ripening and harvest) at the end of the wet season (late October to November), whereas movement from the refugia to the rice field occurred towards the end of the dry season Gate (May/early June), but well in advance of the rice crop planting (July and August) of the following wet season. Insects retained their state of reproductive arrest in the dry season even when offered suitable oviposition sites, i.e. rice plants. Secondary host plants were investigated as possible oviposition sites and food sources for adult flies.

The fecundity and duration of oviposition in three strains of Callosobruchus rhodesianus from the highveld, middleveld and lowveld regions of Zimbabwe and a laboratory strain were recorded on cowpea and greengram. Within-legume variability for both parameters was high among the four strains. The lowveld strain was the least fecund and had the longest duration of oviposition. The middleveld strain showed the highest fecundity on cowpea, but did not differ significantly from the other three strains on greengram.

Bioenergetica, efficiencies of energy transfer and growth of Spodoptera litura larvae reared on mulberry, cabbage, castor and wild hempweed leaves were determined using calorimetrie procedures. Energy contents (J mg−1 ash-free tissue) of castor leaves were higher than those of cabbage, mulberry and wild hempweed. Fresh leaves had slightly higher energy contents than those left over. The rates of ingestion and egestion of food energy increased linearly with the age of larvae. Energy consumption decreased exponentially with larval age, and this decreasing trend showed an intermediate rise at the fifth instar. Assimilation efficiencies were highest and lowest for the first and sixth instar larvae respectively. Efficiencies of gross and net larval production showed linear increases with instar stage, except at the fifth instar which showed dramatic declines in conversion of ingested and assimilated energy into insect biomass. Efficiencies of gross and net productions during early first to third instars were low, but those during the sixth instar were high. The pathways of energy transfer indicated that an average of 58.5% of the total energy ingested was lost directly through faeces, respiration and exuviae, while about 42.2% of the total energy ingested was actually converted into growth of an S. litura larva.

The development time and survival of the castor whitefly, Trialeurodes ricini Misra were measured at four constant temperatures. The duration of the egg stage varied from 15 days at 20°C to 4.6 days at 35°C. No eggs hatched at a constant 40°C. The minimum temperature threshold for egg development was calculated to be 17°C. The total development time from egg to adult ranged from 54.4 days at 20°C to 16.8 days at 30°C. Development of the egg and the first-to fifth-instar larva required 63 and 180 degree-days respectively above the threshold value. Immature survival increased from 64.5% at 20°C to 92.8% at 30°C. Trialeurodes ricini is well adapted to high temperatures and may extend its distribution if mean world temperatures increase as a result of global warming.

In order to develop suitable sampling methods for the arthropods of four mint species, namely Japanese mint (Mentha arvensis L.- var. Hybrid 77), peppermint (M. piperitaL.-var. MP-1), bergamot mint (M. citrata Ehrhrt- var. Kiran) and spearmint (M. spicata L.- var. MSS-5), six general sampling methods viz. ground cloth, sticker, sweep net, water trap, whole plant observation (WPO) and whole plant harvest (WPH) were evaluated under field conditions at the Research Farm of Central Institute of Medicinal and Aromatic Plants, Lucknow, India. The mint pest complex on all the mint species included Aphis craccivora, Chrotogonus trachypterus, Leptocorisa varicornis, Coccinella septempunctata, Bemisia tabaci, an unidentified lygeid bug, Brumoides suturalis, Propylea dissecta, Crysolina exanthematica, Dysdercus cingulatus and Plusia orichalcea. Overall, the ground cloth, sweep net, water trap and sticker methods were found to be more efficient and successful for sampling the arthropods of mint crops than the WPO and WPH methods. The shortest sampling time was required when using the sticker (3–6 seconds per sweep) and the sweep net (7–8 seconds per sweep) methods. This information may be useful in developing an integrated pest management programme for mint.

Organosoluble extracts from 55 Turkish medicinal plants were tested under standardised conditions for biological activity against third-instar larvae of mosquitoes Aedes aegypti and Anopheles gambiae. Eight extracts demonstrated significant larvicidal activity, with An. gambiae being more susceptible than Ae. aegypti in all cases. The possibility of using indigenous plants for mosquito control is discussed.

Crystals of a local isolate of Bacillus thuringiensis variety israelensis were isolated by centrifugation on a continuous sucrose gradient (40–70%). Analysis of the crystals by SDS-PAGE revealed three major protein subunits of Mr˜25,000, ˜66,000 and Mr˜140,000. The crystals were solubilised using high pH and reducing conditions. Analysis of the soluble (protoxin) and insoluble fractions by SDS-PAGE showed the presence of proteins of Mr˜21,000 and ˜61,000, respectively. Proteolytic treatment of these fractions resulted in no apparent change in the molecular weights of the proteins. The crystals contained carbohydrate moieties as determined by periodic acid Schiff (PAS) and fluorescein isothiocyanate (FITC) Concanavalin A staining. In double radial immunodiffusion experiments, antisera raised against the Mr˜21,000 and ˜66,000 subunits did not react with other B. thuringiensis protoxins known to be active against the tsetse fly, Glossina morsitans morsitans, and the stemborer, Chile partellus.

The agar gel double diffusion test was evaluated for detection of nuclear polyhedrosis virus infecting the silkworm, Bombyx mori L. (BmNPV). The test was successful using alkali-dissolved BmNPV as antigen. The antiserum raised against dissolved BmNPV gave positive results with a wider range of antigenic concentrations compared to antiserum raised against undissolved BmNPV. Gel plates prepared using phosphate buffered-saline as dissolving medium for agarose gave sharper and clearer precipitation bands compared to those made with sodium carbonate-saline as diluent. Sharp bands were obtained when the experiment was carried out at 25°C, whereas at higher temperature (35°C), the bands were diffused. The test was able to detect antigen concentration as low as 2 × 106 OBs/ml (18.9 μg/ml of antigen protein).

The juvenoids fenoxycarb and methoprene were evaluated for morphogenetic activity on last-instar nymphs of the American bird grasshopper, Schistocerca americana (Drury) (Orthoptera: Acrididae). Topical application of fenoxycarb induced supernumerary nymphs, adultoids and adults with curled wings. Methoprene yielded similar morphogenetic effects although at reduced levels of activity. Of particular interest, however, is the discovery that, in addition to its morphogenetic activity, fenoxycarb causes significant mortality in developing fourth-, fifth- and sixth-instar nymphs.

The effect on the larval development of Helicoverpa armigera of caffeoylquinic acids and their structural units, caffeic acid and quinic acid, was evaluated. 5-Caffeoylquinic acid (5CQA) (syn. chlorogenic acid) significantly retarded larval development and increased the number of days to pupation at a concentration of 9 mM in an artificial diet, although final pupal weights were not severely affected. Caffeic acid and quinic acid also inhibited larval development although their effect was less marked. In all cases the effect of the compounds was dose-dependent. A mixture containing 5CQA, 3-caffeoylquinic acid (3CQA) and the novel compound, 1-caffeoyl-4-deosyquinic acid (ICdQA), which were extracted from the wild groundnut species, Arachis paraguariensis (Chod et Hassl.) was also evaluated at a concentration equivalent to that found in the plant (9 mM). This mixture was a potent inhibitor of larval development and more potent than 5CQA alone at the same concentration. The potential role of these substances in host plant resistance of groundnuts and their interaction with other components of pest management strategies are discussed.

Genetic differentiations in natural populations of the tsetse fly, Glossina pallidipes Austen (Diptera: Giossinidae) collected from three ecologically distinct regions of Kenya, namely Lambwe Valley, Shimba Hills and Nguruman were analysed based on two enzymes, phosphoglucomutase (PGM) and phosphoglucose isomerase (GPI). The PGM gene frequencies of allele (a) of male and female flies from Lambwe Valley showed significant differences. A dendrogram of populations collected from different localities showed two clusters: one comprising Shimba Hills, Majimboni and Muhaka Forest and the other comprising Gendo, Homa Hills and Nguruman. This suggests mat different subpopulations of G. pallidipes have adapted to different habitats.

Two phenylpropanoid glucosides, namely acetylmartynoside A and 4”-O-acetylmartynoside, isolated from Aegiphila obducta (Verbenaceae) were studied for insect antifeedant activity against fourth-instar larvae of Chilo partellus (Lepidoptera: Pyralidae). Acetylmartynoside A showed weak antifeedant activity at all the concentrations tested while 4”-O-acetylmartynoside showed strong antifeedant activity, particularly at the higher concentrations of 400 and 500 μg/disk.