Field surveys carried out in Mozambique showed that two indigenous cereal stemborers, Busseola fusca Fuller (Lepidoptera: Noctuidae), Sesamia calamistis Hampson (Lepidoptera: Noctuidae) and one exotic stemborer, Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae), are the main pests of maize and sorghum in the country. Busseola fusca was abundant at high altitudes (> 800 m) and Ch. partellus was abundant at low altitudes (< 800 m). Sesamia calamistis occurred at all elevations but in low numbers. Of the three stemborers, Ch. partellus was the most widespread and abundant pest of maize followed by B. fusca. Therefore, a programme was initiated to introduce the exotic parasitoid Cotesia flavipes Cameron (Hymenoptera: Braconidae) to increase natural suppression of Ch. partellus populations. Cotesia flavipes was introduced into southern Mozambique for the first time in November 1996. Additional releases were subsequently carried out in several places in southern and central Moz imbique from 1998–2000. The parasitoid was recovered from all localities sampled 1 to 3 years after its introduction, indicating that this exotic parasitoid had established in the southern and central regions of Mozambique.

Hand-stinging and mass exposure methods of rearing the parasitoid Cotesia flavipes Cameron (Hymenoptera:Braconidae) on the stem borer host, Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae), were compared. The proportion of hosts successfully parasitised, progeny production, proportion of female progeny, and host mortality did not differ between the two methods. However, there was evidence of superparasitism of mass-exposed hosts. Releases of C. flavipes as adults and as cocoons were both effective methods for field colonisation of the parasitoid. A device for the release of C. flavipes in the cocoon stage is described.

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 millet stem borer, Acigona ignefusalis Hampson, can cause total crop failures when severe infestations occur such as happened in northern Nigeria in 1984. Research at the Institute for Agricultural Research at Samaru has shown that various millet types and varieties exhibit different levels of susceptibility to the stem borer, although no resistant varieties are yet available. Infestation and damage by the stem borer are strongly influenced by date of planting and rate and time of nitrogen fertilizer. The effect of mixed cropping with sorghum depends on the spatial arrangement of the component crops in the mixture as well as on the insect population pressure. Systemic insecticides, particularly granular carbofuran, have been found to control the stem borer more effectively than contact insecticides like carbaryl. Seed dressing with carbofuran has been found to be ineffective. Some natural enemies of the stem borer have been identified but their role in lowering damage to millet is minimal. The destruction of infested stems before the beginning of the rainy season is a very important control measure against the insect. The possibilities of integrating these various methods for stem borer control are discussed.

Thirty-five pearl millet cultivars of short, medium and long maturity cycle were screened in Senegal during 1985–1986 crop seasons to study field reaction to the attack of stalk borer, Coniesta (Acigona) ignefusalis Hmps.; spike worm, Heliocheilus (Raghuva) albipunctella De Joannis; millet midge, Geromyia penniseti Felt; head smut, Tolysporium penicillariae Bref; and ergot, Claviceps fusiformis Lov. Insect and disease incidence varied considerably depending upon cultivar maturity cycle. Least susceptible cultivars were IBV-8001 and P8 against spike worm; Zalla, NKK, P8 and M2D2 against head smut, and Ex-Darou against ergot. Cultivation of IBV-8001 has been suggested in northern and central Senegal. However, studies on identification and utilization of resistance sources of wide genetic diversity and multilocational tests may be necessary.

Effects of nitrogen on stem borer damage in a sorghum/millet m ixture were investigated in Nigeria. Millet and sorghum grain yield as well as stem borer infestation were not significantly influenced by rate and time of nitrogen application. Borer (Acigona ignefusalis) infestation on millet was very severe in 1984, resulting in total crop failure. In 1985, millet produced grains because of lower borer infestation and damage; the yield of sole millet was thrice that of millet in mixture, whereas the sole crop density was twice that in the mixture. Unlike millet, sorghum produced grains in 1984 despite severe damage by Busseola fusca. Sole sorghum yielded five times the mixture in 1984 but two and a half times in 1985. Borer damage was generally more severe in the mixture.

Combining ability analysis for three stem borer resistance parameters, i.e. “dead hearts”, leaf injury and stem tunnelling, revealed that both additive and non-additive types of gene effects were involved in the inheritance of these attributes. The specific combining ability (sca)/general combining ability (gca) variance ratios further indicated predominance of additive gene effects for stem tunnelling and non-additive effects for “dead hearts” and leaf injury. The genotypes, IS 2123 and IS 5469 are good general combiners for all the three parameters. Among F1 hybrids, IS 1054 × IS 5469 and IS 18551 × IS 2123 expressed good sca for all the parameters of stem borer resistance. The use of IS 2123 and IS 5469 parental genotypes in the future breeding programmes is suggested.