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.

Interspecific competition within larvae of the fall army worm (FAW), Spodoptera frugiperda (J. E. Smith), by the larval parasitoids, Cotesia(= Apanteles) marginiventris Cresson and Microplitis manilae Ashmead, and the egg-larval parasitoid Chelonus insularis Cresson was studied. Chelonus insularis was not able to compete successfully against Cotesia marginiventris, but was a successful competitor against Microplitis manilae. Multiple parasitization of larvae by either Cotesia marginiventris or Microplitis manilae, which as eggs were parasitized by Chelonus insularis, did not result in additional host mortality. Percentage parasitization under greenhouse conditions by Cotesia marginiventris of larvae parasitized previously by Chelonus insularis was two-fold higher in corn compared to sorghum and more than four-fold higher compared to Bermuda grass and itch grass. The host finding and behavioural sequence of oviposition of Cotesia marginiventris in FAW larvae already parasitized by Chelonus insularis consisted of nine steps. Microplitis manilae females changed their behaviour significantly by displaying a reduction of ca. fifty per cent in host examinations, 45% in ovipositor probes, and 55% in apparent ovipositions when Chelonus insularis parasitized larvae were presented. Cotesia marginiventris and Microplitis manilae exhibited no significant behavioural changes in the per cent contacts, examinations and apparent ovipositions when attacking larvae parasitized previously by either Cotesia marginiventris or Microplitis manilae.

Insect rearing and its management is a prerequisite in developing IPM packages for various food crops. Insects reared for the development of these packages should be regularly monitored for quality in order to ensure success. This paper describes various methods of rearing followed at the ICIPE in the process of IPM development. The rearing of Chilo partellus is described as an example of large-scale rearing. Steps in the experimental rearing of Busseola fusca are outlined. The rearing of an egg parasitoid, Trichogramma mwanzai is described as a vital technology in the IPM of maize and sorghum. The value of quality control is emphasized using the rearing of the phytoseiid mite, Neoseiulus teke as an example.

Several insect pests are associated with the sorghum crop, but essentially a few are considered key pests. These include shootfly, several species of stem borers, sorghum midge and a complex of head bugs. Other insect pests which are occasionally devastating and sporadic include leaf feeders and defoliators (Lepidoptera of various genera, locusts, grasshoppers, aphids, beetles, etc.) and also several species of head worms and head beetles. A list of 101 insect pests of sorghum occurring in Africa is presented.

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.

Green marine algae (Codium sp.) was extracted sequentially with different organic solvents on cold. Lima bean leaf discs treated with the different extracts were offered to adult female T. urticae for 96 hr and the corrected percentage mortality of the females was calculated. The toxicity of the different extracts to the eggs was also recorded. Petroleum ether extract of this seaweed was highly toxic to females at 4 g/ml. At 1 g/ml ca. 48% of the individuals were killed. Chloroform and ethyl alcohol extracts were found to be poorly effective against the females even at high concentrations (4 g/ml) where less than 50% of the individuals died after 96 hr. Toxicity of crude extracts to the egg stage was less pronounced and chloroform extract was found to be more efficient than the other extracts tested.

The effects of infection by Trypanosoma brucei and DNA virus on the ultrastructure of the salivary gland cells in Glossina pallidipes Austen were investigated. Cytoplasm of uninfected cells contains a dense ribosomal population and rough endopiasmic reticulum, scattered Golgi areas and mitochondria. In infected ceils of salivary glands the ultrastructural integrity of the cytoplasm is profoundly changed due to cellular proliferation giving rise to a stratified epithelium and gland enlargement; cell degeneration characterized by formation of cytoplasmic vacuoles, chromatin margination, disorganization and elimination of cell organelles and gland hypertrophy. The virus particles are found in the nucleoplasm as well as the cytoplasm of cells. The ultrastructural evidence indicates that the virus are largely assembled in nuclei of cells and virions pass through the nuclear membrane. The trypanosomes are found within the degenerating cytoplasm and lumen of the cell.

The implications of the features observed in the infected cells are discussed, and possible suggestions are made regarding alteration of the metabolic functions due to infection.

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.

Plant essential oils possess diversified insecticidal properties. Under screening programme of survey of bioactive agents for insect control 31 essential oils from different botanicals (2% in acetone), were studied for repellency and direct toxicity (insecticidal) against laboratory bred houseflies, Musca domestica L. The essential oils obtained from Ocimum gratissimum L., Thymus serpyllum L., Illicium verum Hooks, f., Myristica fragrans Houtt., Curcuma amada Roxb. showed 100% repellent activity, and Acorus calamus L. and Thymus serpyllum L. showed about 40% insecticidal activity. Results were compared with N, N-diethyl-meta-toluamide, dimethyl phthalate, malathion, pyrethrum extract, thymol, mineral oil and piperonylbutoxide. Biochemical studies of these promising oils may emerge new leads in developing future pesticides.

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.

Pearl millet, Pennisetum glaucum (L.) R. Br. is attacked by over 100 species of insect pests, but only a few of these are of economic importance. The two major ones, the millet stem borer, Coniesta ignefusalis Hampson and the earhead caterpillar Heliocheilus albipunctella de Joannis have been the subject of research in the Sahel during the last decade. The various methods that have been suggested for the control of these species are briefly discussed. Generally, the control strategy adopted by farmers involves the use of cultural operations that will reduce insect damage. There are no control measures that have been developed for farmers. The more scientific methods that have been suggested are the results from research trials and experiments. These have several limitations. Future perspectives and considerations for developing sound and practical farmer-oriented practices are discussed.

The small scale farming communities own and store much of the cereals they produce. Various aspects of the infestation problem encountered with insect pests of stored cereals have been examined to illustrate the current status of the pest. Reduction of food losses could be effected during producer, consumer and export storage. However, effective management of pest species requires thorough knowledge of the biology and the ecosystem they inhabit. The current management strategies directed against these pests have been examined.

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.

The toxic and repellency effects of four plants Chenopodium procerum, Ocimum canum sinus, Tetradentia riparia and Capsicum frutescens were tested on Acanthoscelides obtectus Say and Zabrotes subfasciatus Boheman. The toxic effect was found on leaves of Ocimum canum sinus and Chenopodium procerum Hochst. The four plants tested did not show any repellency effect on the bruchids.

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.