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.

The distribution and existing control measures for three important Chilo spp. (C. partellus, C. orichalcocilliellus and C. sacchariphagus) to cereal crop production in 10 east African countries and their neighbouring Indian Ocean Islands are reviewed. Various cultural, biological, host-plant resistance/tolerance and chemical control methods developed in the past 30 years of cereal research programmes are discussed. Cultural methods are very effective on Chilo spp. control, but are not widely practised. Although several effective natural enemies have been identified for Chilo spp., very few systematic programmes of their utilization have been effected. Several resistant/tolerant maize and sorghum lines have been reported, but they are not yet fully used. Chemical control though effective, has proved rather unsuccessful in traditional agriculture. Suggestions to incorporate these control methods in Integrated Pest Management (IPM) programmes for Chilo spp. in different places in the region are given.

In southern Asia, Chilo auricilius Dudgeon, Chilo infuscatellus Snellen, Chilo partellus (Swinhoe), Chilo polychrysus (Meyrick), Chilo suppressalis (Walker), Chilo suppressalis simplex (Butler), Chilo sacchariphagus indicus (Kapur), Chilo supermain and Chilo tumidicostalis Hampson are recorded as pests of cereal crops. Chilo partellus causes severe losses in maize, sorghum and rice; Chilo suppressalis, Chilo polychrysus and Chilo supermain are major pests of rice; Chilo auricilius causes damage on both rice and sugar-cane; and Chilo infuscatellus and Chilo sacchariphagus indicus are serious pests of sugar-cane. Chilo suppressalis simplex and Chilo tumidicostalis are minor pests of maize and sugar-cane, respectively. Some of these pyralid borers are minor pests of other cereal crops. The life and seasonal histories of these stem borers and various control measures against them practised in various countries of southern Asia are discussed. The natural enemies of various Chilo species in this region are also listed.

From the literature review and available information on Chilo in the seven Oceanian countries, only six species of Chilo have been recorded as pests of graminaceous crops. C. terrenellus Pag. is one of major sugar-cane pests, in Papua New Guinea and a minor sugar-cane pest on Saibai, Torres Strait Islands, Australia, respectively. In the former country, the damage assessment, host plants, life cycle, phenology and natural enemies of the stem borer have been studied. Since 1981, two larval parasites, Apanteles flavipes Cam. (Indian strain) and Bracon chinensis (Szep.), have been introduced against the stem borer from India, propagated and released but have failed to become established. The search for additional parasites continues. C. influscatellus Sn. is a minor sugar-cane pest also in Papua New Guinea; C. suppressalis (Walk.), C. polychrysa (Meyr.), C. auricilia Dudg. and Chilo sp. are minor pests of rice in Papua New Guinea; the former two species are also minor rice pests in the Northern Territory, Australia where integration of cultural, chemical and biological control measures have been applied against the major white rice borer, Scirpophaga innotata (Walk.), in conjunction with C. suppressalis and C. polychrysa.

Since the introduction of irrigation in the early 1950s major changes in the crop regime have taken place in Israel. These changes had greatly influenced the populations of the four species of corn borers found in Israel. Chilo agamemnon, which was the main pest during the 1960s decreased and the numbers of Sesamia nonagrioides increased. The reduction in the sorghum acreage, caused a decrease in the numbers of Sesamia cretica. In 1981 an increase in the numbers of the European corn borer, Ostrinia nubilalis, was observed. At present S. nonagrioides and O. nubilalis are the main corn pests in Israel.

Chilo agamemnon was first recorded in Israel in 1959 near the Gaza strip. In the course of 2–3 years it became a very serious pest in the southern parts of the country. Later, the spread of the pest continued throughout the country. Since 1973 a drastic decrease in the populations of C. agamemnon was recorded. The probable reasons for the decrease in the populations of this pest in Israel are:

(1) The relative increase of the areas of sweet corn, which is not its preferable host plant.

(2) Rice and sugar-cane, which are very important host plants in Egypt, are not grown in Israel.

Field experiments against C. agamemnon, carried out when populations were high, showed that dust applications were more effective than sprays.

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.

Population trends of Chilo suppressalis during the past 20–35 years in Japan, Korea and Taiwan were compared in terms of light trap records and the area infested by Chilo. In all three countries, Chilo showed a declining population trend, first observed in the late 1950s in Japan, followed by the same pattern in Taiwan and Korea, successively. Among the contributing factors, the early planting of rice was suggested as one common factor. This early planting of rice is also followed by, or associated with, various agronomic practices, e.g. the use of varieties with a larger number of tillers, more intensive pesticide control, early harvesting, the mechanization of agricultural practices, etc. An integrated technology system based on early planting was considered the primary factor responsible for the recent decrease in Chilo. The increased utilization of machinery in rice production will encourage a further decline in Chilo in this region. Local and small scale outbreaks of Chilo were observed in all three countries, due to the widespread use of straw for the culture of special crops. However, so long as the current production system remains the same, there is no scope for Chilo's revival.

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.

The main thrust of the article is to present the historical development of the idea of Integrated Pest Management (IPM) from the heyday of “pestophobia” (the insistence of elimination of any vestige of insect interference with the cosmetic appearance of our crops), which leads to the misuse and abuse of insecticides, to the era of employing IPM concepts, which leads to pest interventions which are necessarily knowledge-intensive. Illustrations are given using ICIPE's research experience in developing an IPM approach to the control of Chilo through adaptation of relevant intercropping patterns, plant resistant cultivars and biological control agents. In this task, the IPM specialist needs to have three assets to be successful in the tropics: he needs to be a first-class natural historian; he requires to build his new knowledge on the traditional knowledge of the rural farmer, and to rationalize it scientifically, and he needs to be able to manipulate new innovations—both technical and social.

The effects of endogenous and exogenous factors on mating behaviour were investigated to clarify the mechanisms of mating initiation, as one of the fundamental studies on the rice stem borer, Chilo suppressalis. The periodicity of mating behaviour is controlled basically by an endogenous circadian rhythm, and it is further affected by exogenous factors, such as temperature, day length, light intensity, light wave length and so on. Seasonal variations of mating behaviour can be observed under field conditions. The time of the onset of mating behaviour in August was delayed about 2 hours compared with that of June. Such variation of mating periodicity can be ascribed to the change in the hours of female calling and male pheromone response under different conditions among the seasons. Some of the important behavioural and physiological phenomena concerning mating initiation of Chilo suppressalis are discussed.

Like most other insects, Chilo partellus requires sterols such as cholesterol in the diet. Freshly hatched larvae grown on a chemically defined diet take about 27 days to become adults. However, when an azasteroid, 25-azacholesterol is added to the diet in concentrations ranging from 0.5 ppm to 25 ppm, the time taken to become adults became 41 days at 5 ppm azasteroid. The maximum larval weight decreased to 76 mg from 140 mg as compared to the control insects. In larvae reared on a diet with 10 ppm azacholesterol, about 60% larvae died. The mortality was almost complete at a dose of 25 ppm. The larvae, pupae and adults reared on the chemically defined diet contained sitosterol, stigmasterol, cholesterol, compesterol and isofucosterol. No desmosterol was, however, detected in these insects. Inclusion of 25-azacholesterol in the diet led to the detection of desmosterol in these insects. It was observed that the cholesterol concentration decreased greatly, whereas sitosterol and stigmasterol concentration increased. This showed that the azacholesterol inhibited the dealkylation of C29 plant sterols to cholesterol, probably at the level of Δ-24-sterol reductase as evidenced by the accumulation of desmosterol. In some cases the adults were unable to separate themselves completely from the pupal cases. Some larval-pupal intermediates were also noted. It was further observed that the spermatogenesis was disturbed due to azacholesterol treatment. This may indicate that ecdysone biosynthesis is probably impaired. These results indicate that inhibition of steroid utilization may have the potential of being developed into a method for integrated pest management.

When 1, 2-dibenzoyl-1-tert-butylhydrazine was added to the diet at concentrations varying from 1 to 10 ppm, all the larvae died in all the concentrations tested, except 1 ppm. The larval weight was reduced to almost half due to the treatment and the larval duration increased as in case of 25-azacholesterol. However, the sterol composition of the insects did not change greatly.

This paper reports observations made on the sensory biology of Chilo partellus larvae and adults. The larval and adult antennae of this insect have hygro/thermosensitive sensilla equipped with receptor cells sensitive to minute changes in temperature. Inputs through those cells may partly be responsible for the light evasive and other light/temperature-dependent behaviour patterns. The grooved basiconic sensilla especially those found on the male antennae are sensitive to the female sex pheromone components of C. partellus. Host-plant odours are most likely perceived by one or two of the other antennal olfactory sensilla, namely the smooth-surfaced basiconica and coeloconica sensilla. Chilo partellus moths have a limited number of gustatory sensilla on the tarsi, ovipositor, antennae and the proboscis. Electrophysiological bioassays done on the ovipositor and tarsal sensilla are discussed. Similar tests on the larval maxillary styloconica sensilla showed that the lateral and medial sensilla differed in their sensitivity. Their taste receptor cells can detect differences between saps from susceptible and resistant host-plants.

Several species of Chilo are serious pests of cereal crops. The important species attacking cereals are Chilo agamemnon, C. orichalcociliellus and C. partellus on maize and sorghum; C. auricilius and C. zacconius on sugar-cane, and rice; C. suppressalis on rice; and C. sacchariphagus indicus on sugar-cane. Insects are reared in the laboratory on natural and artificial diets for various purposes, namely for insecticide testing, hormone and pheromone manipulation, biological control, host-plant resistance, etc. Rearing of an insect in the laboratory requires rearing facilities, colony establishment, research and development of rearing techniques, resources, and maintenance of insect quality. All these aspects for rearing major Chilo spp. have been discussed. However, detailed information is available only for C. partellus and C. suppressalis. Techniques used for resistance screening and damage evaluation against spotted stem borer, C. partellus using naturally occurring population and artificial infestation are described.

The permanent mass rearing of rice stem borer, Chilo zacconius in West Africa; rice stem borer, Chilo suppressalis, in Asia and Europe; and sugar-cane stalk borer, Chilo sacchariphagus, in Asia and Indian Ocean was perfected in the laboratory to enable us multiply some parasites such as Apanteles spp., Goniozus procerae, Tetrastichus spp., Trichospilus spp. or the tacbinids, Diatraophaga striatalis and Lixophaga diatraeae.

The principal difficulties appear during mating of several hosts and parasites, development of pyralid young larvae or when it is necessary to protect reared insects or artificial medium against pathogens.

Laboratory and field methodologies for screening for resistance against Chilo partellus on sorghum and maize are reviewed in relation to the insect biology, plant phenology and insect-plant interaction. The value of field and laboratory techniques in achieving the goal to produce resistance varieties and hybrids is discussed. Recommendations for future work are made.

Stem borers are major insect pests of rice in Africa. The utilization of varietal resistance in the management of these pests, has great economic potentials, as it involves no extra cost to the farmer and is also free from environmental hazards. Investigations into the sources of resistance to the African rice striped borer, Chilo zacconius, some possible factors associated with host plant resistance and the benefits derived from growing resistant varieties are briefly reviewed.

The feeding behaviour of third-instar larvae of Chilo partellus appear to be mediated by a complex profile of chemicals present in the whorls of sorghum. These chemicals were extracted sequentially into hexane, ethyl acetate and methanol. Methanolic extracts showed greater feeding stimulation than ethyl acetate extracts and these in turn showed greater feeding stimulation than hexane extracts. Extracts derived from a more susceptible cultivar IS 18363 showed greater feeding stimulation than extracts from a less susceptible cultivar IS 2205.

Phagostimulatory compounds present in ethyl acetate and methanolic extracts include phenolics and sugars, respectively. Combinations of these sets of phagostimulants synergize to give enhanced feeding activity of third-instar larvae. Chromatographic examination of extracts of IS 18363 and IS 2205 showed quantitative rather than qualitative differences: the more susceptible cultivar IS 18363 had higher phenolic and sugar contents than the less susceptible cultivar IS 2205. These results suggest that Chromatographic quantification of the different sets of phagostimulants might constitute a basis for resistance screening of different cultivars of sorghum.