The expression patterns of Cry1Ac protein and the resistance to striped stem borer Chilo suppressalis (Walker) of cry1Ac/CpTI transgenic rice (Oryza sativa L.) were investigated by ELISA and laboratory bioassay. ELISA results showed that Cry1Ac protein could be detected in all organs during the development process of cry1Ac/CpTI transgenic rice. The content of Cry1Ac protein varied markedly in different tissues at different stages: it was higher in the earlier stage than in the later stage. The highest level of Cry1Ac protein in terminal leaves of the main stem was found at the jointing stage. Thereafter, it decreased at the booting stage, and a gradual reduction to the lowest level was recorded from the flowering to the filling stage, before a slight increase was shown at the maturing stage. In addition, higher concentrations of this protein were detected in the main stem at the seedling, jointing and flowering stages than at other stages. Relatively lower levels of Cry1Ac protein were found in seeds. The results from laboratory bioassay showed high resistance of terminal leaves of the main stem in all developmental stages to C. suppressalis larvae. Corrected mortality values of C. suppressalis at 4 days after feeding on the detached leaves of cry1Ac/CpTI transgenic rice reached 90% before the filling stage and decreased to nearly 60% after the filling stage. Interestingly, results of whole plant bioassay coincided with those obtained in the detached leaf bioassay. The tendency of larval morality in the detached leaf bioassay and whole plant bioassay was consistent with that of Cry1Ac protein content in the different growing periods and organs.

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.

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.

A binary mixture of (Z)-ll-hexadecenal and (Z)-13-octadecenal was first identified as the sex pheromone components of female Chilo suppressalis. Later, an additional component was identified as (Z)-9-hexadecenal, which markedly enhanced the attractiveness to males when it was mixed to the binary mixture. Rubber septa containing ca. 0.3–1.0 mg of a mixture of the above three components in the natural ratio have been shown to keep up significantly higher attractiveness than virgin females for at least one month. It has also been shown that the pheromone trap is much more effective than a light trap, where both traps usually showed similar trap catch patterns. Several factors affecting trap catch, such as trap type, trap placement, etc., have been examined. Feasibility of the population monitoring with the synthetic pheromone was discussed.

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.

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.

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.

About 20 species of borers are rice pests. Of these, five—yellow borer, striped borer, white borer, dark-headed borer, and pink borer—are of economic importance. Yellow borer and striped borer occur most widely in Asia and cause serious yield losses.

Varietal resistance to these two species has been investigated during the last 30 years. Field and greenhouse screening techniques have been developed and numerous germplasm entries have been evaluated for resistance. Several hundred varieties with low to moderate levels of resistance have been identified. Except for several wild species of Oryza, germplasm with a high level of resistance has not been found.

Information available to date indicates that the resistance is under polygenic control. Moderate levels of resistance from several donor parents have been incorporated into improved varieties. Some of these moderately resistant varieties, for example, IR20, IR36, IR50, Ratna and Chandina, are widely grown and play an important role in integrated pest management programs for stem-borer control. Efforts to develop cultivars with levels of resistance higher than presently grown varieties are under way using the diallel selective mating system and the male sterile facilitated recurrent selection schemes.