Currently, the systematics of the African noctuid stem borers of the subtribe Sesamiina, which include major pests of cereals, is confused. In addition, their ecology is poorly known, as are the factors influencing their evolution. In this paper, we address these shortcomings for two genera of the Sesamiina, Sciomesa Tams & Bowden and Carelis Bowden. Mixed Bayesian phylogenetic analysis, which included their host plants and two mitochondrial genes, showed the genus Sciomesa to be polyphyletic. Two new genera were created, Pirateolea and Feraxinia. The genus Carelis proved to be paraphyletic and was subdivided into two sub-genera. The genera Sciomesa, Carelis and Pirateolea (named the ‘Sciomesa genus group’) share morphological traits, and the phylogenetic analysis showed that they had a common ancestor living on Cyperaceae and that they were distant from the genus Feraxinia belonging to another clade which had an ancestor living on Poaceae. Seven new species were described: Sciomesa gnosia sp. n., Sciomesia bua sp. n., Pirateolea nola gen. n, sp. n., Feraxinia serena gen. n., sp. n., Carelis australis sp. n., Carelis transversa sp. n. and Carelis agnae sp. n. Ten species were sunk as synonyms: Sciomesa mesoscia (Hampson) syn. n., Sciomesa mirifica Laporte syn. n., Sciomesa constantini Laporte syn. n. and Sciomesa etchecopari Laporte syn. n. are synonyms of Sciomesa mesophaea (Aurivillius); Acrapex sparsipucta Laporte syn. n. is a synonym of Sciomesa excelsa (Laporte) comb. n.; Acrapex congitae Laporte syn. n., Sesamia minuta Laporte syn. n. and Sesamia minuscula Laporte syn. n. are synonyms of Sciomesa boulardi (Laporte) comb. n.; Acrapex bryae Laporte syn. n. and Acrapex fayei Laporte syn. n. are synonyms of Feraxinia jemjemensis (Laporte) comb. n. Eleven new combinations were created: Sciomesa excelsa (Laporte) comb. n., Sciomesa boulardi (Laporte) comb. n., Sciomesa punctipennis (Krüger) comb. n., Pirateolea piscator (Fletcher) comb. n., Pirateolea argocyma (Fletcher) comb. n., Pirateolea cyclophora (Fletcher) comb. n., Pirateolea ochroneura (Fletcher) comb. n., Pirateolea funebris (Krüger) comb. n., Feraxinia nyei (Fletcher) comb. n., Feraxinia jemjemensis (Laporte) comb. n. and Carelis biluma (Nye) comb. n.

Surveys were completed in Eritrea, Ethiopia, Kenya, Madagascar, Mozambique, Tanzania, Uganda and Zanzibar to assess the lepidopteran stem borer species diversity on wild host plants. A total of 24,674 larvae belonging to 135 species were collected from 75 species of wild host plants belonging to the Poaceae, Cyperaceae and Typhaceae. Amongst them were 44 noctuid species belonging to at least nine genera, 33 crambids, 15 pyralids, 16 Pyraloidea species not yet identified, 25 tortricids and three cossids. The noctuid larvae represented 73.6% of the total number of larvae collected, with 66.3, 3.5 and 3.8% found on Poaceae, Cyperaceae and Typhaceae, respectively. The Crambidae, Pyralidae, Tortricidae and Cossidae represented 19.8, 1.9, 2.5 and 0.1% of the total larvae collected, respectively, with 90.4% of the Crambidae and Pyralidae collected from Poaceae, and 99.7% of the Tortricidae collected from Cyperaceae. The lepidopteran stem borer species diversity in the wild host plants was far more diverse than previously reported.

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.

The current phenological study in sorghum fields has shown that Busseola fusca is bivoltine in eastern Ethiopia. The first generation begins at the end of April, while early August marks the beginning of the second (Diapause) generation. The second generation passes through the dry season in stalks and stubble as diapause larvae, of which a considerable proportion survive in the stubble until the next crop. The onset of pupation of the diapause larvae is in the middle of April. A progressive increase in the mortality of the larvae of both generations is observed towards the later stages. Five hymenopterous parasitoids, Bracon sesamiae (Cameron), Cotesia (= Apanteles sensu lato) sesamiae (Cameron), Dolichogenidea (= Apanteles sensu lato) sp. near laevigatus, Pediobius furvus (Gahan) and Procerochasmias nigromaculatus (Cameron) and one dipterous parasitoid (Sarcophaga sp.), attacking larvae and pupae of B. fusca at Alemaya, eastern Ethiopia, were identified.

A light trap was operated in Samaru, Nigeria between 1973 and 1980 to monitor populations of Coniesta ignefusalis. Two generations of the insect/year were represented by two adult peaks in July and September. In 1974, an early peak in May resulted in three generations. In cages in the field, eggs were laid between the leaf sheath and the stem in batches of 20 to 70 with a mean of 47.5 eggs/batch. Laboratory studies conducted at 25–28°C and 75–85% r.h. showed an average developmental period of 35.5 days. The average duration of the egg, larval and pupal stages were 4.5, 21.9 and 9.2 days, respectively. Unfed adults lived for 5.3 days.

One of the critical factors in assessing maize lines for resistance to Sesamia calamistis is the number of larvae/plant used for infestation. Artificial infestation of maize plants with two and five larvae/plant resulted in 29.1 and 39.5% stand loss (dead hearts and stalk breakage), while 10 and 15 larvae/plant resulted in 52 and 72.9% stand loss, respectively. For a satisfactory artificial infestation in maize screening trials against the maize stem borer in Nigeria, a population level of 10–15 larvae/plant is recommended.

Two indigenous maize cuitivars, Inbred A and Nyamula, were evaluated in a field trial for their susceptibility/resistance to Chilo partellus at the artificial infestation levels of 10 larvae/plant and 20 larvae/plant. Foliar damage was caused predominantly by C. partellus, but stem-tunnelling was caused not only by C. partellus but also by another species of borer, Eldana saccharina, which invaded the crop during the tassel emergence stage and persisted during harvest. In the 10-week old crop, the number of C. partellus recorded on Nyamula was greater than on Inbred A, but the incidence of injury to foliage and stem-tunnelling on the two cuitivars was the same. At harvest the degree of damage to the two cuitivars varied. At the infestation level of 20 larvae/plant, the cuitivars suffered equal stem-tunnelling. There was a significant negative correlation between stem-tunnelling and yield for Inbred A, but the correlation was not significant for Nyamula. At the infestation level of 10 larvae/plant, the correlation between stem-tunnelling and yield was not significant for either of the cuitivars, perhaps, due to excessive activity of E. saccharina in the stalks of Inbred A.

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.

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.

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 paper reviews the work done on the population patterns of Chilo spp. in relation to the phenological stages of sorghum, maize and millets. The stem borer Chilo partellus entered sorghum and maize crops at 2–3 weeks after emergence and continued till harvest. There were 3–4 peaks of larval population during a cropping season. Such studies not only reveal the relationship between the larval population density and the phenological stage of the plants at infestation time, but are also helpful in scheduling and timing pest management strategies.

The stem borer Chilo spp. is a significant limiting factor of tropical cereal production. Consequently, international co-operation in research, education and training and resource sharing, including information exchange is essential for the Chilo problem to be minimized. Networking is likely to be the most beneficial mechanism for co-operation, for it has proved effective in bringing together faculties and establishing fora for exchange of experiences. The sustenance of co-operation and strategic devolution of appropriate responsibilities to national institutions are key considerations for enlisting national support and continued international co-operation.

A review of the losses caused by various species of Chilo, methodologies adopted for the assessment of losses and information generated on the models for the effect of Chilo species on the yield of graminaceous crops is given.

Sources of information on the biology and ecology of Chilo species are reviewed on a world-wide basis, with emphasis on the major pest species which are stem borers of rice, maize, sugar-cane, sorghum and other cereal crops and grasses. Information on geographical distribution, host plants, general biology, ecology and population dynamics is summarized for the main species, especially for C. partellus (Swinhoe), C. suppressalis (Walker), C. infuscatellus (Snellen), C. sacchariphagus (Bojer), C. auricilius (Dudgeon), C. zacconius Bleszynski and C. agamemnon Bleszynski. Other species are also noted, including C. diffusilineus (de Joannis), C. panici Wang and Sung, C. terrenellus Pagenstecher, C. polychrysus (Meyrick), C. plejadellus Zincken, C. niponella (Thunberg) and C. orichalcociliellus (Strand). Requirements for additional and better organized information are identified.

Lepidopterous stem borers constitute one of the major constraints to cereal crop production in southern Africa. Chilo partellus Swinhoe, is an economically important stem borer of maize and sorghum. Current research status on C. partellus is reviewed and substantial advances in the distribution, bioecology and control strategies are discussed. Present work on the assessment of crop losses, elucidation of mechanisms of resistance, development of resistant crop cultivare, feasibility of biological control measures and the implementation of other stem borer management methods are reported. Further areas of research into the management of C. partellus are identified.

Twenty-seven species of Chilo which infest graminaceous crops are listed. The effects of various cultural practices such as time of planting, plant density, field sanitation, tillage, mulching, intercropping, proper fertilizer and water management on field populations of Chilo spp. are discussed. These practices have great potential as components of IPM for resource-limited farmers in the tropics.

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.

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.

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.

The biology of Chilo partellus (Swinhoe) was studied on two resistant, IS 2205, IS 5469 and two susceptible, HC 136, ICSV1 sorghum genotypes. Significant differences were observed between resistant and susceptible genotypes in regards to larval mortality in whorl, larval period, larval weight, larval length, per cent pupation, pupal weight, fecundity per female and total life span of this pest. Growth index was also influenced by the resistant genotypes. It has been concluded that high mortality of larvae on resistant lines is due to antibiosis.

The correlations between the characters of the pest biology have been worked out and larval stage was the most important parameter influencing the total pest survival and population build-up in the succeeding generations.