Anatomical features of cowpea (Vigna unguiculata) associated with stem and pod wall resistance to the legume pod borer, Manica testulalis, were studied. The anatomical microenvironment of the area immediately post the stem epidermis seems to impose severe limitation to larval movement and feeding within the tissue. Collenchyma cells in both 21-day old TVu 946 and IT82D-716 stems form a network of closely knit interlocking cells with a few intercellular spaces. Significant differences (P < 0.05) were observed in the distance between the epidermis and collenchyma cells of the slightly raised (convex) and concave portions of TVu 946 and IT82D-716 stems. TVu 946 had a smaller stem diameter than IT82D-716 stem. Distance between epicarp and mesocarp tissues of 7-day old TVu 946 and IT82D-716 pod wall did not show any significant difference. Similarity in cell and tissue arrangement and the absence of strengthening tissues in pod wall could be some of the most important constraints responsible for their vulnerability to larval damage.

Stem anatomy is considered to be an important factor in stem resistance to M. testulalis, but this does not appear to be the case in pod wall resistance.

The effects of intercropping groundnut with sunnhemp on termite incidence and damage were studied in the rainy and post-rainy season at ICRISAT Center in central India. Termite incidence in different cropping systems was determined by baiting with bamboo stakes. Damage to groundnut plants and pods was evaluated at harvest.

Intercropping groundnut with sunnhemp did not affect termite abundance or damage to groundnut. These results contrast with a Colombian intercropping study in which sunnhemp exudates repelled cassava burrowing bugs. Termite biology, including recruitment of foragers and construction of protected runways, may have reduced exposure to sunnhemp, thereby minimizing effects.

Most germplasm lines and improved sorghum genotypes identified as resistant to shoot fly (Atherigona soccata Rond.), stem borer (Chilo partellus Swin.), midge (Contarinia sorghicola Coq.) and head bugs (Calocoris angustatus Leth.) are resistant to only one of these insects which usually will infest the same crop during the same season. At ICRISAT Center, India, a technique was developed in which entries were subjected to an array of combinations of pest infestations for identifying and separating genotypes with resistance to one or more insects.

Using this technique, 220 resistance sources and breeding lines were evaluated for multiple insect resistance. Less than 10% of shoot fly resistance sources had acceptable resistance (< 3 on a scale of 1–9) to shoot fly, but over 50% showed good resistance (scores of 1–3) to stem borer. IS 18551 and IS 2195 were the best entries with resistance to both shoot fly and stem borer. However, the majority (80–90%) of shoot fly and stem borer resistant sources were highly susceptible to midge with scores > 8. Similarly, all midge resistant sources were highly susceptible to shoot fly but less so to stem borer where seven midge lines had scores < 5. IS 22464 was the best midge line with a score of 3 for stem borer resistance. Advanced breeding lines showed a wider range of resistance to shoot fly, stem borer and midge with a higher frequency for resistance to stem borer, PS 28060−3 and PM 14388−1 were the most promising breeding lines.

Four soybean genotypes, PI 227687, PI 229358, Davis and Hardee were tested for their antixenosis and antibiosis to the soybean hairy caterpillar, Spilarctia casignata Koll. PI 227687 and PI 229358 showed greater antixenosis and strong antibiosis (high larval and pupal mortalities, reduced pupal weight, and a low growth index). Davis and Hardee were the favoured hosts as indicated by high larval preference based on increased feeding and low larval and pupal mortalities, increased pupal weight and a high growth index.

The effects of cowpea, Vigna unguiculata (L.) Walp. canopy structure and pod position in relation to infestation and damage by the legume pod borer, Maruca testulalis Geyer were investigated. Defoliated cultivars sustained significantly less infestation and damage (P < 0.05) than those undefoliated. Relative humidity measured under the canopy was lower in defoliated cultivars, while soil and ambient temperatures were higher. Percentage pod damage and larval infestation by M. testulalis in flowers were positively correlated with relative humidity, and negatively correlated with temperature. Both correlations were significant (P < 0.01).

Cultivars with pods held within the canopy suffered significantly more damage (P < 0.05) than cultivars whose pods were held in the normal position. Canopy structure and pod position acting together or independently, exerted profound effects on cowpea resistance to M. testulalis. Selection and breeding cowpea cultivars with less dense foliage (= open canopies) and long peduncles holding the reproductive structures above the canopy, should increase cowpea resistance to M. testulalis.

Consumption indices and apparent digestibility are measured for seven species of grasshoppers from Lamto (Ivory Coast), representative of different trophic specialization steps (Le Gall and Gillon, 1989), The consumption indices vary from 0.11 to 0.34 and the apparent digestibility from 30 to 65%. Specialists are not more efficient on their host plant than are generalists on convenient host plants, but some specialists fed on plants which are not convenient for generalists. Anthermus granosus and Eucoptacra spathulacauda feeding on Lippia multiflora is not convenient for a generalist like Eucoptera anguliflava. If feeding efficiency does not seem to be a real selective pressure, it can be an important step in specialization processes, when there is an adaptation to an unusable host plant for polyphagous species.

Differences in the constitution of plant parts eaten by the grasshopper play an important role in the digestibility. The differences in the efficiency observed between the two specialists of Lippia are from their differences in feeding behaviour.

Mussidia nigrivenella Ragonot is the main cob borer of maize in Ivory Coast. An accurate description of male and female genitalia is given. Rearing in the laboratory has permitted determination of the number and duration of the pre-imaginal instars, fecundity of adults and fertility of eggs as also the sex-ratio. An artificial diet has been elaborated which provides conditions of similar development to those observed in the field: The insect has 5 to 6 larval instars and the total duration of development from the egg-laying to the adult emergence is 46 days for the male and 49 days for the female.

The larvae of Mussidia nigrivenella Ragonot, attack various fruits; it is the main maize cob borer in Ivory Coast. The development of attack during the cultivation, the behaviour of larvae in the field, the spatial distribution of eggs and larvae, the mortality of pre-imaginal instars and the annual fluctuations of populations are considered in this paper. This insect may represent an economical problem for seed producers in the south of the savannah area of Ivory Coast where its density exceeded 14 insects per cob, at harvest in 1984, whereas the risk of cob damaging by Mussidia nigrivenella appears to be very weak in the north and west of this region.

Intensive investigations of genetic variation within and among populations of the whitefly, Bemisia tabaci, are under way in Israel and in Colombia. A polymorphic esterase (EST), which seems to be controlled by a Mendelian locus, has two alleles in sufficiently high frequencies to be useful as a genetic marker. The analysis of more than 10,000 individual adult whiteflies shows genetic differences among localities in the frequencies of the fast (F) and slow (S) alleles. These differences seem to be related to the intensity of insecticide use against the whitefly. The frequency of F is high in unsprayed areas and in control laboratory populations, but is close to zero in heavily-sprayed agricultural areas. The frequency of Fon cotton in agricultural areas is high in winter and spring, but decreases dramatically in the summer (coincidental with the onset of pest-control activities on cotton). A similar temporal pattern on untreated Lantana may be due to migration of adults from agricultural fields. There was no indication of differentiation of populations on different host plants. In Colombia, the difference in EST patterns in different States are very pronounced, suggestive of geographical races. Small samples from Florida, California and Kenya indicate that B. tabaci in different countries may be genetically distinct.

The elegant grasshopper, Zonocerus elegans Thunberg, occurs in large numbers in Kilosa district during the dry season June to January and attacks a wide range of wild and crop plants. Its impact as a pest of crop plants becomes more noticeable from the middle of the dry season when the hoppers are well advanced and the only alternative food available are vegetables in backyard gardens and river valleys. The grasshopper damage continues throughout the vuli (short) rains until the end of the oviposition period in January, thus limiting the production of green vegetables in the district. A study on the biology and ecology of the pest in Kilosa district with emphasis on short term control strategies was started in 1987. Spot spraying with insecticides to kill the early instars was found to be effective, but area-wide implementation was necessary to prevent re-invasion of cleared areas.

Scanning electron microscope (SEM) micrographs of aedeagi and pygofer processes of some Cicadulina spp. are presented for the first time. They should assist in the identification of Cicadulina spp. by entomologists who are not trained in taxonomy, and who work in national research programmes in Africa without access to well-equipped libraries and reprint collections, that offer ready access to the original descriptions of Cicadulina spp. A number of national maize research programmes recently initiated studies on Cicadulina leafhopper biology, behaviour, ecology and mass rearing for resistance screening to streak virus and all of them face the problem of species identification. This report summarizes widely scattered publications and provides new illustrative information to assist in the identification of Cicadulina spp. by national scientists in Africa.

Regular field surveys were carried out in 2 week intervals in 1986 and 1987 to determine population density, species composition, migration activity of Cicadulina leafhoppers and their infectivity with maize streak virus (MSV) in different ecological locations of southeastern Nigeria: mangrove swamp forest (IITA and RIART station at Onne), deltaic swamp forest (RSUST, Port Harcourt), seasonal swamp forest (Iriebe) and high forest zone (NCRI, Amakama near Umuahia).

Population density was always low during dry season, significantly lower in the rain forest zone and higher in the swamp forest, rapidly rising in the second rainy season in all ecological zones and reaching its maximum before the rains finally stopped. Sharp increase in the population density in Nov. and Dec. may indicate mass migration activity of Cicadulina leafhoppers from already dry areas of adjacent Guinea savanna at that period.

Six species of Cicadulina were collected from most of sampled areas. C. ghaurii was the predominant species in 1986 and 1987, averaging 55.9% for all locations and periods. Its portion was higher in the mangrove swamp forest (Onne) than in the high forest zone (Amakama). The predominance of other species declined in the order: C. triangula (18.2%), C. mbila (17.2%), C. arachidis (5.9%), C. similis (2.8%) and C. hartmansi (0.1%). In absolute values, the portion of individuals out of the total number of leafhoppers collected was for C. triangula 53.7%, C. ghaurii 25.5%, C. mbila 17.3%, C. arachidis 2.3%, C. similis 1.1% and C. hartmansi0.1%. A high population of C. triangula occurred only in the relatively short period in Nov.-Dec, especially in Iriebe and was correlated with the rapid increase of Cicadulina densities in all sampled areas; a high migration activity of C. triangula and C. mbila was confirmed.

Incidence of MSV in the surveyed farmers' field varied between 0–22% in the first rainy season (1987) and 12–25% in the second rainy season (1986). The portion of Cicadulina adults already infected with MSV under field conditions and capable of transmitting MSV to the susceptible maize seedlings varied from 3.3 to 23.3%, with higher values for leafhoppers collected at the end of the second rainy season.

By means of the GM (1, 1) modelling of grey system theory, the authors built the predicting models of Tryporyza incertulas (Walk) occurrence tendency with a computer, based on the insect pests occurrence data accumulated for 26 years from Feng Cheng county:

model I x(t + 1) = 71.2131e0.1136t - 68.2131

model II x(t + 1) = 58.2206e0.1254t - 55.2206

Tests indicated that the two models are valid, and if we use the models to predict the damage by Tryporyza incertulas in the year in which the damage by Tryporyza incertulas is serious, the results would contribute to the control of borers in the area in practice.

The economic injury level (EIL) of the maize stem borer, Chilo partellus (Swinhoe) was determined by artificially infesting maize (cv. Katumani) plants at three different growth stages; viz, 20, 40 and 60 days old plants with varying densities of newly hatched larvae; viz, 2, 4, 6, 8, 10 and 12 per plant constituting the borer population. The grain yield data obtained from the infested and the protected plants showed that maximum yield reduction and stalk damage occurred to the 20-day old crop, while there was insignificant larval effect on yields for the 60-day old crop. Regression analyses gave a significant linear equation (y = a + bx) which estimated the yields per plant at different infestation levels and these were used to calculate the economic injury level at each stage. The resultant EIL was 3.2 and 3.9 larvae/plant for 20- and 40-day old plants, respectively.

The banding patterns of six soluble enzymes of a Sogatella furcifera Horvath population from Sri Lanka, maintained in glass-houses on rice variety TN 1 at University of Wales, Cardiff, were studied. Crude homogenates of macropterous adults of both sexes were analysed, using polyacrylamide electrophoresis. The following enzymes showed activity and were stained: esterase (EST), lactate dehydrogenase (LDH), phosphoglucomutase (PGM), hexokinase (HK), glucose-6-phosphate dehydrogenase (G-6-PDH) and malic enzyme (ME). Number and relative mobility of bands varied between enzyme systems.

During prolonged flight, locusts predominantly utilize lipids for energy generation. Lipid stores are mainly located in the fat body. Flight is accompanied by release of adipokinetic hormones from the corpora cardiaca. Under the influence of these hormones, fat body triacylglycerol is converted to diacylglycerol, which is released into the haemolymph. This release requires the presence of specific lipoproteins. The lipid mobilizing effect of adipokinetic hormone on the fat body is attended by the association of a high density lipophorin and a non-lipid containing protein, both already present in the haemolymph, and the increased amount of released lipid to form a new lipoprotein, low density lipophorin. Upon delivery of the lipid to the flight muscles, participating proteins dissociate again and can be reused for lipid uptake at the fat body (lipoprotein shuttle system). The flight-specific metabolic systems could be starting-points for new devices in control strategies.

This review concentrates on air-borne chemical cues that blood-seeking mosquitoes use to locate a host. A distinction is made between short- and long-range attraction. Carbon dioxide is involved in both processes. It activates and attracts mosquitoes. The latter function is only observed in combination with an odorous organo-chemical. Other olfactory cues are primarily involved in long-range attraction. Bodily emanations from the host that contain olfactory cues can be divided into three groups: Skin emanations, exhaled air and urine. Each of these is attractive to mosquitoes, but there is little knowledge about the chemical compounds that cause the attraction. Lactic acid in the presence of CO2 is attractive, and lactic acid-sensitive neurosensilla are present on the antennae. Other host-produced chemicals are also attractive, but chemical identification and subsequent confirmation of attractiveness for mosquitoes has not been reported. Host preference in mosquitoes is species-specific and varies from highly specific to opportunistic. Attraction is likely to be caused by a mixture of several compounds. Synergism may be an important way of increasing the effect of separate chemical cues.

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.

The CILSS (French acronym for “Permanent Interstate Committee for Drought Control in the Sahel”) regional crop protection training centre in Niger provides a 2-year training programme in crop protection for middle-level field technicians as one of its major activities. The training is open to candidates from all the nine CILSS member countries. It deals with all aspects of plant protection. The success of this training programme depends to a great extent, on a well-formulated and objective-oriented programme catered to the backgrounds and needs of the trainees. As insect pests are an important limiting factor in agricultural production in the Sahel, the entomology subjects constitute an important part of the programme. This paper describes the contents of the entomology programme and strategies and constraints in its delivery. The future role of applied research in supporting and strengthening this programme is also outlined.

In his opening address, Professor Odhiambo referred to the militaristic approach to pest control in which we aim to first know our pest enemies and then destroy them. I would like to take that military analogy further. We certainly need to have good information about our pest enemies, in order to know the weak points that are vulnerable to attack, but we also need good strategies and we need to know our allies in the fight, especially the natural enemies of pest species that operate as a generally unseen resistance force, and our professional allies—the entomologists and other scientists that provide our intelligence reports.