Several species of Chilo occur on sugar-cane, out of which five have major pest status. Infestation by these pests causes losses in cane yield and sugar recovery. There are constraints involved in the use of cultural, mechanical and chemical control measures on a large scale, but the nature of the crop facilitates adoption of biological control. Many species of natural enemies occur in the sugar-cane agro-ecosystem, which is relatively less disturbed. They play a significant role in maintaining the pest populations at reasonably low level.

In biological control, the egg parasite, Trichogramma spp., has been widely used with varying results. Among the larval parasites, Apanteles flavipes (Cameron) and Sturmiopsis inferens Townsend have been used on a limited scale and need further testing in other countries. The exotic tachinids introduced, failed to establish against Chilo spp. Not much work has been done on the predators, though the native predators play a significant role in reducing the pest densities. Among the entomopathogens, granulosis virus infecting Chilo infuscatellus Snellen has shown promise in the control of this pest and needs further evaluation in other agro-climatic regions. Future thrust for biological control of Chilo spp., in sugar-cane has also been indicated.

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.

Polyculture can help stabilize agroecosystems against frequent and severe pest outbreaks. An overview of the published data highlights ecological relationships among weeds, nematodes, arthropods, sugar-cane mosaic virus (SCMV), and the sugar-cane crop itself. Whereas individual studies commonly depict weeds as being either “good” or “bad”, this review is a synthesis of the variable roles and interactions of weeds in sugar-cane in order to provide a realistic perspective on the possibilities of weed interactions in sugar-cane agroecosystems. Conservation of weeds in Louisiana sugar-cane has resulted in more diversified arthropod fauna, higher natural enemy populations, and reduced damage by the sugar-cane borer, Diatraea saccharalis (F.). Weed competition and SCMV infection have each been associated with altered sugar-cane free amino acid accumulations that appeared to play a role in reducing populations of selected phytophagous nematodes. The combination of both weed and SCMV stress factors, however, have been shown to favour higher sugar-cane nematode populations. Although some weeds are alternate hosts for SCMV and its aphid vectors, and ratoon stunting disease (RSD), weed growth has not been linked with higher phytophagous nematode infestations or incidence of RSD. Weeds, if kept below economically competitive densities, may be ecologically and financially sound assets to sugar-cane pest management tactics.

The sugar-cane borer (SCB), Diatraea saccharalis (F.), and the ratoon stunting disease (RSD) bacterium independently caused significant reductions in stalk weight, cane tonnage and sugar yield. A three-fold difference was found in the comparison of per cent loss of cane tonnage due to RSD alone with that due to the disease in combination with SCB damage in first ratoon sugar-cane. Variance analysis failed to detect interaction between damage by SCB and that by RSD. The data analysed were obtained from an experiment of six replication which evaluated the effects of SCB damage and RSD on sugar-cane yield in Louisiana. We used the randomized complete-block experimental design with split-plot arrangement of treatments. Three schedules of insecticide application to the growing cane, against SCB were the main plots whilst the subplots comprised of RSD inoculation vs. no inoculation of sugar-cane plants grown from seed canes with light vs. severe SCB damage.

Observation on natural enemies of the stem-borer complex on sugar-cane in southern Ghana indicated that Descampsina sesamiae Mensil (Diptera:Tachinidae) is the most important larval parasite of Sesamia species. The relative abundance of this tachinid parasite appeared to vary with the rainfall pattern throughout the year and with the phenology of the sugar-cane plant. The rate of parasitism was found to be higher in the outgrowers fields than in the sugar estate's fields. Differences in cultural practices used as well as the type of vegetation bordering the sugar-cane fields, were believed to be responsible for the difference in the rate of parasitism of D. sesamiae on Sesamia species.

Zea mays L. and Rottboellia exaltata L. were the main graminaceous plant species infested by Eldana saccharina Walker, the major pest of sugar-cane in southern Ghana. Other stem-borers of sugar-cane, Sesamia botanephaga Tams and Bowden, Sesamia penniseti Tams and Bowden, Sesamia calamistis Hampson and Chilo zacconius Bleszynski, were recorded on Zea mays, Echinocloa pyramidalis (Lamk.) et Chase, Rottboellia exaltata, Panicum maximum Jacquin and Oryza sativa L.

All the stem-borer populations except E. saccharina on Rottboellia exaltata increased on their host plants. Sesamia and Chilo species were present from January to December on Echinocloa pyramidalis. It is concluded that these alternative host plants provide a potential source of stem-borer infestation on sugar-cane at Asutsuare in southern Ghana.

Studies on damage by larvae of Eldana saccharina Walker, Chilo zacconius Bleszynski and Sesamia spp. to sugar-cane stands revealed a high degree of correlation between internode damage and stalk damage as well as between internode damage and sugar content of the canes. For every 1% increase in stalk damage there was a corresponding increase of 0.214% in the internode damage. The distribution of larvae inside the internodes was found to depend on the level of infestation. At low field infestation level (below 25 larvae per 100 canes) the distribution was random. As the level of infestation increases, the distribution becomes more aggregated. The distribution of damage in the sugar-cane field was found to depend on the overall stalk damage. The distribution tends to be more contagious when field level of stalk damage was less than 45%. The damage became evenly distributed when stalk damage rose above 60%. An estimation of average loss of sugar caused by stem-borers to the variety NCO 376 (at the field damage rate of 8.6, 10.6 and 3.1% damage for bottom, middle and top parts respectively of the cane) was U.S.S332.10 per ha of field.

Female Eldana saccharina Walker was found to lay 327 ± 17.1 eggs within a period of 4 days and required three surfaces to lay eggs which were mainly deposited on the inner side of leaf sheaths fitting tightly on to the sugar-cane stalk. The mated females laid more eggs per female (327.0 ± 17.1) than virgin females (212.3 ± 5.5). The incubation period of the eggs of E. saccharina was found to be 5.64 ± 0.01 (5–7) days in the laboratory and 5.82 ± 0.03 (5–7) days in the field. The mean larval duration was 31 days and pre-pupal period lasted 2.05 ± 0.05 days. Larvae were found to exude a brownish liquid from their mouth in the direction of the invading predators. The newly hatched larvae spread out in 1–3 days of hatching. The mean growth ratio of the larval instars was 1.54 ± 0.05. Pupae frequently occurred very close to the exit hole (less than 5 cm) and the pupal period varied from 7 to 13 (9.76 ± 0.05) days. The life cycle of E. saccharina was completed in 49 (36–62) days. The pre-oviposition period was 2 days and the female reproductive life lasted 4 days. It takes about 53 days for a succeeding generation to be produced. Adults of E. saccharina survived from 6 to 13 days. Adults reared from field collected larvae snowed a sex ratio of 42:51 which was significantly different from 1:1 in the laboratory bred stock, at the 5% level of probability. A comparison of the life cycle of E. saccharina populations in Ghana and Uganda suggests the existence of two biotypes of the pest.

Population dynamics of the larvae of Eldana saccharina Walker, Chilo zacconius Bleszynski and Sesamia spp. on sugar-cane was studied over a period of 3 years, by regular sampling. Analysis of results indicated that during the first rainy season (March–June) the borer populations were low. However, the larval population increased considerably during the dry season and declined gradually during the second rainy season (September–November). Rainfall in Southern Ghana is typically bimo-dal, but it is occasionally evenly distributed throughout the year. When rainfall was evenly distributed. borer populations remained consistently low throughout the year. Flooding reduced the population of E. saccharina larvae in the field. Though the stem-borers showed preference for relatively younger canes, the type of borers present and their proportions varied with the sugar-cane phenology.