This study was conducted on both station and farmers' fields during the 2010 dry cropping season in the Vallée du Kou rice scheme. We investigated the effect of three rice-transplanting periods (8–10 days) on the population dynamics, damage and parasitism associated with rice stem borers. The on-station experiment was designed as a randomized complete block with three treatments (planting dates) and four replications. Regular intervals of 14 days were observed between subsequent planting dates. Weekly agronomic and entomological assessments were performed from the 21st day after transplanting (DAT) to the 84th DAT. The on-farm experiment covered 1200 ha divided into two zones in which 48 farmers' fields were selected according to the periods of rice transplanting (resulting in 16 fields per period). On-station results indicated 10.1% of deadhearts and 7.5% of whiteheads due to stem borers in the first transplanting period, resulting in the lowest yield (2 metric tons/ha). In farmers' fields, the genus Chilo was found to be the most injurious rice stem borer in Vallée du Kou. The highest larval parasitism (38.5%) was recorded in the third treatment. These results provide important data that can be used in the development of an integrated management strategy for rice insect pests in Vallée du Kou.

In order to predict host accessibility by the pupal parasitoid Xanthopimpla stemmator (Thunberg), four grass species (Sorghum bicolor, Pennisetum purpureum, Sorghum arundinaceum and Zea mays) were sampled for stemborer pupae in Kwale, in the low altitudes of southern Kenya, and in Trans-Nzoia, in the high altitudes of western Kenya. The pupal position of Chilo orichalcociliellus (Strand), Chilo partellus (Swinhoe), Sesamia calamistis Hampson, Sesamia sp. nr oriaula (Tams and Bowden) and Busseola fusca (Fuller) in the plant were determined in relation to (a) the distance of pupae from the edge of the stem (depth), (b) the distance between the moth-exit hole and the head of the pupa (location) and (c) the length of the tunnel from the moth-exit hole to the base of the tunnel. Pupal depth and location for C. partellus and B. fusca varied significantly in the different plant species tested, and the pupae tended to be embedded deeper in cultivated than wild hosts. On all host species, the borers were located at a depth less than 0.35 cm. Most C. orichalcociliellus and S. calamistis pupae were found pupating in the ears of maize or the upper part of the wild hosts' stem. Sesamia sp. nr oriaula was only collected from the lower parts of P. purpureum. For B. fusca, tunnel length varied significantly among plant species and was longer in cultivated hosts. Xanthopimpla stemmator has an ovipositor length of about 0.52 cm, thus it is anticipated that the parasitoid could easily reach and parasitize the pupae in these host species.

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.

Chilo species are the most important stem borers of sugar-cane. They cause heavy losses to sugar-cane crop and continue to suppress yield in the sugar industry. The control of these borer species through insecticides has been difficult as the damaging larvae spend most of their life-cycle within the cane plant. The breeding of borer resistant varieties is an ideal approach for controlling the damage as it does not cost the grower anything extra, is effective at all levels of pest infestation and its effects are cumulative and long lasting in reducing the pest population. Many plant characters such as leaf surface, rind hardness, leaf sheath tightness, fibre content, stalk pith and diameter and plant vigour have been associated with borer resistance. In sugar-cane breeding, the inclusion of borer resistance characters, in addition to many other agronomic characters required of a commercial variety, is rather difficult due to the segregating nature of this plant. Therefore, it is better to use, as parent varieties the few varieties showing marked resistance without knowing the actual reasons of resistance. The joint efforts of sugar-cane breeders and entomologists in production and selection of a large number of seedlings for desired characters can help to solve this problem to a greater extent.

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.

Knowledge on the natural enemies of graminaceous stem borers is outlined, with special reference to mortality of Chilo spp. as crop pests in Africa. The quantitative scanty information available suggests that over 90% mortality of eggs and larvae takes place before the larvae become established as borers in the crop and that mortality of the older larvae and pupae is much lower. Possible manipulations of natural enemies to increase mortality further are reviewed. In view of the largely negative results of past classical biological control introductions the prospects do not appear very promising. However, the results do indicate some possibilities which should be investigated, notably trials with Apanteles spp. (Braconidae) and intra-continental redistribution of important species with restricted distributions. For short-term biological control, development of microbial biopesticides seems a more promising strategy than augmentation of insect parasitoids by breeding and release, particularly on small farms. A third possibility, enhancement of the action of native natural enemies by environmental manipulation, merits more attention as part of an integrated crop production approach to the improvement of the quantity and reliability of yields for the small farmer.

The flight phenology of the stem borer, Chilo partellus (Swinhoe) at the ICIPE's Mbita Point Field Station (MPFS) and on a nearby farmer's field was monitored using pheromone traps. The relation between pheromone trap catches of males and sorghum plant age, infestation, larval/pupal population density and sorghum cultivars used was examined. At MPFS C. partellus males were caught throughout the year in pheromone traps. Fluctuations of trap catches indicated that the pest completes two main generations on each of the long and short rain sorghum crops. On farmers' fields, males continued to be caught in large numbers after harvest, implying that the pest continues to breed on the sorghum stalks and tillers. Significantly lower observed catches of males occurred only on one (MB-3) of the eight different sorghum cultivars, during the period of 2–6 weeks after plant emergence. In general, positive correlations were observed between the number of males caught in pheromone traps and larval pupal population density, males and percentage plants infested, and males and plant age. However, the pheromone trap appeared to be less effective under high population density, particularly during the flight of the second generation moths, due to competition between pheromone trap and wild females. But the flight phenology as monitored by pheromone traps appeared to reflect major events in population development of C. partellus. Pheromone traps would be useful in detecting C. partellus and for monitoring its flight phenology.

Three species of Chilo, namely C. auricilius, C. suppressalis, and C. polychrysus are predominant in Asia; and the other three, C. zacconius, C. partellus, and C. diffusilineus are predominant in Africa on rice crop. Various screening methods to identify resistance donors in cultivated as well as wild rices have been used over the last 30 years. The level of resistance in available donors of cultivated species is moderate, except in some accessions of Oryza nivara/O. rufipogon, O. officinalis, O. brachyartha and O. minuta. Genetics of resistance is complex as appears from the review. Efforts to incorporate the resistance into new developing breeding lines have been sporadic and discontinuous in African countries. At IRRI and in many Asian countries, systematic approaches have been undertaken. Once donors with superior levels of resistance become available, systematic breeding approach has to be made with the help of multidisciplinary teams at suitable test sites. African breeding programmes need close linkage with IRRI's stem borer programme and International Rice Stem Borer Nursery.

The information available on the genetics, breeding, and utilization of host plant resistance to 14 of the most important species of maize stem-borers complex, their biology, and the damage done to the crop is presented.

The components necessary for implementing a programme for breeding for resistance to stem-borers in maize include: a colony of the pest(s), the capability to mass rear them, uniform artificial infestation methods, an array of the available maize germplasm or related species, rating scales and evaluation methods that permit identification of genetic resistance, knowledge of screening and breeding methods, and the personnel and resources to execute the programme.

The paper having emphasized the importance of each component, concludes with a discussion of several HPR programmes and the breeding methods being used in various areas of the world, to develop and utilize resistance to one or more maize pests, as a proven method for gaining increased management control over these pests.

Graminaceous crops are attacked by lepidopterous stem-borers all over the world causing severe crop loss. Chemical control of stem-borers is difficult and biological control is preferable for peasant farming systems. The most important genera are Diatraea, Chilo, Eldana, Sesamia and Busseola. Their natural enemies include egg, larval and pupal parasites and predators. The parasites are cued by different stimuli, some to host plant, others to borer tunnels or frass. Biocontrol was first attempted against Diatraea spp. in the New World where D. saccharalis is now under fair control in several countries. In the Old World attempts have been made to control C. sacchariphagus and E. saccharina without much success. In East Africa releases of exotic parasites against B. fusca, S. calamistis, C. partellus and E. saccharina have not been very successful and further work is suggested. Leguminous crops suffer from attacks of lepidopterous pod-borers. The most damaging species are Etiella zinckenelia, Maruca testulalis, Cydia spp. and Lampides hoeticus. There are relatively few records of important parasites and fewer still of predators, however, large parts of the world are still unsurveyed for natural enemies. Successful control using introduced parasites has been reported from Canada against C. nigricana and Mauritius against E. zinckenelia and M. testulalis. There appears to be scope for introductions of Caribbean parasites into Africa.