In view of the losses of harvested grain incurred due to problems related to storage, marketing, transport, and handling, this paper reviews the situation on storage of food grains in developing countries. It lists the insect pests that frequently attack stored food grains in these countries and discusses strategies that would minimise the damage caused by the pests.

It is evident that our environment has been flooded with pesticides and that some of these have had effects other than those intended. There is no doubt that indiscriminate use of pesticides has the potential to upset temporarily many ecological patterns. Whether this is significant in the long run remains to be seen.

It is sincerely hoped that the experience of the past (especially in the first world) will ensure wiser use of the pesticides in the future (primarily in the third world). It is likely that new pesticides will be developed and that they will bring new problems. Some of these problems may have far-reaching environmental implications in terms of their potential benefits and their propensity for damage. These problems will be compounded by residues of pesticides and a host of other contaminants already present. Therefore, it should and must be everyone's responsibility that the potential benefits from pesticides are maximised. However, such maximisation will be realised only if the environmental implications of their use is understood, and if they are applied with discretion to minimise their side effects.

Food consumption and utilization of a bivoltine silkworm hybrid was studied to understand the efficiency of food conversion into larval body, cocoon and cocoon shell during the life cycle. The ingesta, digesta, excreta, reference ratio, mean daily food ingested and digested in different larval instars were recorded. All these parameters differed from one larval instar to another. The AD and ECI were inversely correlated with the larval age. The ECI and ECD for body, cocoon and cocoon shell were 23.63, 17.59, 9.496 and 55.12, 46.65 and 25.23% respectively. Ingesta and digesta required to produce a gram body weight, progressively increased from first to fifth instar. Ingesta and digesta for one gram body, cocoon and cocoon shell production were 4.402, 5.762, 10.649 g and 1.840, 2.184 and 4.047 g respectively.

Rather than a true adaptive process, laboratory colonization is proposed to depend on the plasticity of the tolerance limits in insect species. Insects will establish successfully in captivity if the magnitude of environmental variables are within the insects' ranges of colonization. Optimum physiological and behavioural responses are obtained when the variables are within the smaller preferred range of colonization. Other concomitant processes at colonization are selection, acclimatization and domestication. Definition of the terms “adaptation”, “acclimatization” and “domestication”, commonly misused in describing processes during laboratory colonization are proposed.

When reared in the greenhouse, the rice skipper, Pelopidas mathias (F.) (Lepidoptera: Hesperiidae), laid 2–3 times fewer eggs than Held collected females held under the same conditions. Adult-emergence and mating/oviposition cages may have to be placed in environmental chambers with controlled temperature and photoperiod to achieve normal mating and oviposition. Rearing required a mating'oviposition-cage at least 3 m3 in volume and honey as sustenance. Eggs and larvae were held in larval rearing cages and pupae were removed and held in adult emergence cages. Maximum oviposition occurred at dawn. The total developmental period from egg to adult was 34.7 days. P. mathias demonstrated a greater oviposition preference for rice and Paspalum conjugatum Berg, than for Dactyloctenium aegyptium (L.) Willd. P. mathias successfully developed to adulthood on all 24 species of Poaceae tested, exclusive of rice, but did not survive on the six species of Cyperaceae tested. Low populations of P. mathias in rice can be attributed to its low fecundity, wide host range, and equal adaptability to upland and lowland environments, thus diluting its number.

Field studies were conducted to characterise the effects of infestations by adult and nymphal stages of cowpea aphid, Aphis craccivora Koch, on the growth and yield of cowpea, Vigna unguiculata (L.) Walp. Seedling, flowering, and podding stage plants of aphid-resistant (cv. ICV-12) and aphid-susceptible (cv. ICV-1) cowpea cultivars were used in the studies. Four treatments (consisting of infestations with adult and nymphal aphids, caged controls and uncaged controls) were administered on plants for 22 days post-treatment. Eight parameters of crop success were measured: extended leaf heights (ELH); plant mortality; incidence of sooty mould; incidence and abundance of natural enemy species; crop growth parameters (net assimilation rate, [NAR] in g/ dm2/day, and crop growth rate [CGR] in g/dm2 land surface/day); and plant yields (seeds per pod, weight per seed). Data were analysed using analysis of variance (ANOVA), orthogonal contrasts and 95% confidence intervals (C.I.). There were no significant (P > 0.05) differences between adult and nymphal infestations or between caged and uncaged controls, so the respective sets of data were combined for comparisons of aphid infestations with control treatments. Infestations caused severe plant stunting and other growth deformities, drastic yield reductions, higher plant mortality, greater incidence of natural enemies and abundance of Cheilomenes spp. on cv. ICV-1 than on cv. ICV-12, and on infested and uninfested plants. Aphid infestations did not significantly affect the incidence of sooty mould on plants of cv. ICV-12 or cv. ICV-1.

The struggle to control populations of organisms that feed on agricultural crops, livestock, and directly on humans is as old as recorded history, and will continue into the perceivable future. Only 30 years ago, the availability of relatively cheap and highly effective synthetic organic pesticides was thought to be the ultimate solution to pest populations. However, our naïveté regarding the ability of pest populations to rapidly adapt to simplistic man-induced selection pressures has become increasingly apparent, as have the detrimental impacts of pesticides on the environment. The evolution of the integrated pest management paradigm can be traced to these concerns, and it is now accepted that sustainable solutions to the management of pest populations will only be borne out of an increased understanding of the functioning of ecosystems. Knowledge of the population dynamics, and underlying causes of density changes in pest populations, behavioural ecology, and population genetics of pests and natural enemies, are essential elements for designing appropriate biologically intensive strategies for pest management. Progress is being made, and several examples of innovative strategies and promising areas of research, are discussed. Future work must continue to be based on a solid foundation of ecological understanding, to avoid the pitfalls of simple opportunistic solutions.

Gas Liquid Chromatography was used to obtain profiles of cuticular hydrocarbons from single larvae of two species belonging to the Anopheles gambiae complex: A. gambiae and A. arabiensis. By applying discriminant analysis of hydrocarbons it was possible to separate the two populations with a 95% success rate.

The same analysis was used to achieve an average of 94% segregation among their strains. This analysis does not require preservation of specimen by liquid nitrogen or refrigeration and further identification by other procedures can be carried out on the specimens after cuticular hydrocarbon analysis. More importantly the technique permits analysis of single rather than pooled specimens used by earlier investigators.

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.

Time-specific life tables were constructed for the Mexican beetle, Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae), which is a promising biological control agent of the Neotropical weed, Parthenium hysterophorus L. (Asteraceae) in and around Bangalore, India. Infertility of eggs (46.00–71.10%) was found to be the key mortality factor, followed by death during the pupal stage (15.76–21.38%), as confirmed by key mortality factor analysis and construction of survivorship curves. No parasitoids or predators were recorded on this insect, while some of the dead pupae/pre-pupae (2.27–17.24%) were found to be infected by Metarhizium anisopliae (Metchnikoff) Sorokin. The high generation trend values (305.88–557.14), give an indication of the biotic potential of this insect, which was found to cause rapid defoliation of the weed under field conditions.

Significant changes have occurred in the role of pesticides in pest management programmes since the publication of Carson's book Silent Spring in 1962. This discourse addresses the multitude of factors which contributed to these changes including such factors as policy and legislation, the public's perception of associated risks, population pressures, the availability of practical integrated pest management programmes, and perhaps most importantly, the constraints to IPM in Third World countries. While reliable statistics are difficult to obtain, the changing patterns in pesticide use in the tropical regions are also discussed. Finally, the future of pesticide use in developing countries is projected, as is the necessity of their use and expected impacts.

Larval and adult predators comprise the largest component of the natural enemy fauna which attack the semi-aquatic rice caseworm Nymphula depunctalis (Guenée). Spiders, birds, and adult dragonflies/damselflies were the dominant predators of caseworm adults, while aquatic beetle larvae, aquatic bug nymphs and adults, and ants preyed on caseworm larvae. Egg parasitoids are unknown in nature and larval/pupal parasitoids are rare. A nuclear polyhedrosis virus, the only recorded pathogen, occurs but rarely. A ricefield pulmonate snail Lymnaea quadrasi (Mollendorff), which forages on algae, causes limited caseworm egg mortality in a passive and fortuitous manner. Water beetles—the dytiscid Cybister tripunctatus orientals Gschwendtner and hydrophilid Sternolophus rufipes Fabricius—are voracious larval predators. Prey consumption by these water beetles is higher on older caseworm larvae whose larger size creates more movement while the larvae are crossing the water surface. Also, older caseworms are more prone to leave the protection of their cases while under attack. Younger caseworm larvae, however, tend to retract and remain motionless when attacked. The last instar dytiscid preyed on an average of 11.4 caseworm larvae per day while that of the hydrophilid preyed on 6.7 larvae per day.

The larval critical weight (Lcw) in the spotted stem borer, Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae) was 54.6 ± 1.0 mg for average sized male and female final instar larvae and was 63 and 39% of the larval maximum weight (Lmw) of males and females, respectively. There was a consistent decrease in weight from Lmw to pupal weight of 35% in both males and females over successive generations of rearing two laboratory populations. The adult weight was consistently about 37 and 22% lower than the pupal weight for males and females, respectively. During starvation, 25% of the final instar larvae produced a supernumerary moult. A positive correlation was derived between female pupal weight and fecundity. The results were similar to those derived from a study on the progeny of a wild population. A model representing the various fresh weight changes in relation to the Lmw has been suggested for this species. The model is similar to that proposed for other Lepidoptera. The results of this study are largely consistent with those carried out on other species of Lepidoptera and underline the value of using stable standards in assessing the quality of laboratory reared insects.

Seven-day-old seedlings of 22 rice cultivars with dominant Glh1, Glh2, Glh3, Glh5, Glh6 and Glh7 and recessive glh4 genes were evaluated for resistance to the green leafhopper (GLH), Nephotettix virescens (Distant), in a no-choice seedling test under uniform infestation at four nymphs per seedling. “IR29” (gene not identified) was the resistant check, while “Taichung Native 1” (no resistance gene) was the susceptible check. Maximum reproducibility for resistance score was obtained 11 days after infestation. “Pankhari 203” (Glh1), “Kalimekri 77–5” (IRRI Accessions 6613 and 6622) (Glh1), “ASD7” (Glh2), “DNJ97” and “Arai” (Glh3), “ASD8” (Glh5), “PTB18” (Glh6), and “Laki 65” (IRRI Accession 6622) and “Lasane” (Glh7) showed consistently resistant reaction under the no-choice test. The lines could be used for allelic studies of GLH resistance and for gene pyramiding.

Field studies on oviposition site, preference and pattern of Busseola fusca on various stages of maize were conducted at Awassa (southern Ethiopia). The positions of egg masses in terms of leaf sheath and height from the ground were described for different ages of the maize plant. Irrespective of the age of maize plants, eggs were laid on the under side of leaf sheaths. Busseola fusca moths showed ovipositional preference to younger maize plants. Significantly fewer egg masses were laid on older plants (r=.0.98, P <0.001). A strong relationship between maize plant age and position of egg masses was found. During the post-tasselling stage the great majority of the egg masses were found below the primary ear.

Pesticides provide an important component of integrated pest management, but the timing, accuracy of dosage, and method of applying the pesticides need careful consideration to permit harmonisation with other control tactics. Concern about pesticide spray drift has led to categorising the spray quality of nozzles, which is defined by comparing the droplet spectra of selected reference nozzles measured with a laser light diffraction analyser. However, there is a conflict between a need for small droplets for increased biological efficacy and large droplets to reduce downwind drift. Registration authorities tend to favour a coarser spray with large droplets, and an untreated barrier area that can be left around a treated crop to protect sensitive crops downwind that can provide a refuge for natural enemies. In some circumstances, drift can be reduced with small droplets by electrostatically charging a spray. The charged spray needs to be released close to the crop to avoid the upward dispersion of droplets within a spray cloud due to mutual repulsion exacerbated by convective air movement. Increased deposition of charged sprays on the crop foliage is associated with less soil contamination which allows greater survival of ground-dwelling predators. This feature needs to be exploited by growing relatively narrow strips of a range of crops so that if one crop needs a pesticide treatment, natural enemies can be conserved in adjacent untreated crops. By careful selection of insecticides and dosage rates, these predators should be able to recolonise the treated area and thus integrate chemical with biological control. Application of more selective mycopesticides may require special formulations as well as particular droplet spectra. Pesticides can also be applied mixed with attractants such as pheromones, as a ‘lure and kill’ technique.

Margosan-O®, a commercial neem-based insecticide, incorporated into an artificial diet prolonged the development of larvae of Spodoptera littoralis Boisduval. It also affected the rate of adult emergence at the end of pupation. Larvae treated during one stadium continued to show the effects of their previous exposure. The susceptibility to Margosan-O was more pronounced when larvae ate the diets containing Margosan-O for the first time during the fifth or sixth instar. The results indicate that Margosan-O has an activity similar to that of other neem-seed extracts. In the course of this work morphological anomalies were also recorded. The most striking was the appearance of black stripes on the abdominal tergites of the fifth and sixth instar larvae fed on diets containing 0.01, 0.05 or 0.1% of Margosan-O.

The use of incompatible males (IM) of (A) mating type to suppress the Iraqi (B) strain of Ephestia cautella, when the release ratio was 80:1:1 (A males: B males: B females, respectively), brought about a highly successful protection of uncovered loose dates against infestation with (B) strain in a simulated date store. Surprisingly the protection effect of IMs lasted for 230 days which commercially covers almost the whole period of date storage.

Since strain A males are believed to compete poorly against wild strain B males, the competitiveness of F1 males was measured in order to determine if they might be promising candidates for subsequent trials of the control of E. cautella by the release of incompatible males.

The photoperiodic regimes [24L, 13L 11D (natural condition), 18L6D, 12L12D, 6L18D and 24D] played a vital role on nucleic acid, protein content of fat body and larval-pupal characters of silkworm, Bombyx mori. Prolonged larval duration with a significant increase in weight of the larvae, silkgland, cocoon, pupa and shell was noted in the larvae exposed to 24L period. A significant positive correlation (r = 0.97, P < 0.01) between larval weight and egg production was noted. The DNA, RNA and protein contents increased at 24L over that of 13L11D group as well as other photicregimes.