For the last three years, CIRAD (Centre de Coopération Internationale en Recherche Agronomique pour le Développement, France) and the University of Pretoria led field research to evaluate the impact of transgenic Bt cotton, expressing the Cry1Ac toxin, on arthropod biodiversity in South Africa. The diversity and the density of insect populations were estimated at different crop development stages using traps, sweep-nets, and direct observations on the cotton plants. In untreated plots, the insect diversity in Bt cotton did not show major changes. The toxin was efficient in controlling one of the major bollworm species, Helicoverpa armigera (Hübner), and reduced the population density of specific larval parasitoids. Predators were present in comparable numbers in both cotton types, except for ladybirds. The toxin did not affect pollinators. In small-scale farming fields, where pesticides are still sprayed for controlling sucking insects, the introduction of Bt cotton did not help meet the expected reduction in insecticide use.

The intensity of diapause of field-collected diapausing larvae of Olilo partellus (Swinhoe) and Chilo orichalcociliellus Strand (Lepidoptera: Pyralidae) was compared in the laboratory at 28 ± 0.5°C under a photoperiod of 12:12 (L:D)h. Chilo partellus terminated diapause faster than C. orichalcociliellus. Mean time to diapause termination was 9.7 days for C. partellus and 14.4 days for C. orichalcociliellus. Male and female C. partellus larvae terminated diapause and adults emerged at the same time, while significant differences were found in diapause termination and in emergence times between male and female C. orichalcociliellus.

An additive effect was obtained after treatment of Spodoptera littoralis (Boisd.) larvae with a combination of Bacillus thuringiensis and nuclear polyhedrosis virus (NPVs). The NPVs was the more pathogenic followed by B. t., cytopathologically. Simultaneous application of B. t. and NPVs affected the midgut cells by causing a very specific appearance of cell hypertrophy with some deposits of B. t. crystals on the fourth day of infection as shown by scanning electron microscopy. Transmission electron microscopy showed that the vegetative cells and spores of B. t. entered the midgut epithelial cells followed by the virus. It is possible that the initial destruction caused by the B. t. toxin facilitated penetration and entry of the virus.

Recent studies on the chemical ecology of the desert locust, Schistocerca gregaria, have unravelled a rich and complex system of pheromonal and other semiochemical-mediated communication in this insect. The key pheromones associated with such behavioural processes as social cohesion and communal egg-laying have been characterised. The semiochemical bases of such physiological processes as maturation of solitarious insects before the arrival of seasonal rains, development of gregarious traits in crowded solitarious insects, development of maturation synchrony in gregarious insects, and maternal transfer of gregarious characters to the offspring are better understood. Desert locust semiochemicals are finding two principal uses: as tools for studying the processes associated with gregarisation and, therefore, for elucidating the eco-physiological mechanisms underlying the development of locust outbreaks; and as agents for interfering or reversing the process of gregarisation. The status of this research and its implication for the development of novel ecologically friendly tactics for the management of different locust species are highlighted.

The African armyworm is a migrant moth which, in its larval form, can cause severe plagues which destroy cereal crops, sugarcane and pastures in many parts of Africa. This paper reviews the relevant aspects of a multidisciplinary study into the dispersal behaviour and re-concentration of moths, migratory flight, source areas, population upsurges and the seasonal movement of moths. It introduces the new concepts of primary and critical outbreaks.

Reserpine (a pharmacological agent of plant origin) injected into females of Glossina morsitans morsitans was highly effective in preventing ovulation when injected 1–2 days before the egg is normally ovulated. In contrast, reserpine was only modestly effective in blocking parturition, thus suggesting that these two closely related temporal events may be independently regulated. Males injected with reserpine frequently initiated copulation, but sperm and accessory reproductive gland secretions were never transferred to the female. Reserpine, which presumably acts by depleting stores of amines in the nervous system, may have considerable utility in probing the neuroendocrine regulation of tsetse reproduction.

The effect of visual and olfactory stimuli from leaves of two maize cultivars, Basilocal (susceptible) and Kisan (resistant), in eliciting orientational responses by first instar Chilo partellus (Swinhoe) larvae was investigated in the laboratory. The polar and non-polar chemical constituents of these cultivars were extracted in methanol and hexane, respectively. Orientational preference of the larvae for the leaf whorls and hexane extracts of Basilocal leaves was significantly greater than that for Kisan. The methanol extracts of the two cultivars were, however, equally effective in eliciting larval attraction. These observations imply that the non-polar fraction of maize leaves is more effective than the polar fraction in eliciting larval orientation in C. partellus. Moreover, certain chemicals of Kisan leaves, extractable in hexane, elicited larval repulsion whereas those of Basilocal leaves elicited larval attraction. Identification of the chemicals eliciting attraction or repulsion would be valuable in a management programme for this economically important insect pest of gramineous crops.

Cassava is one of the most important staple crops in Ghana. Losses from the cassava mealybug (CM), Phenacoccus manihoti, and cassava green mite (CGM), Mononychellus tanajoa, infestations in 1983 were estimated at 0.8 m metric tons of tubers. An integrated control programme with biological control playing a key role has been established within the Plant Protection and Quarantine Unit of the Ministry of Agriculture. Of the five beneficial insect species released, only the parasitoid, Epidinocarsis lopezi has so far been established against the CM over the greater part of Ghana. Damage caused by the CM has been reduced quite remarkably, largely due to E. lopezi, with local beneficial insects playing some contributory role. The activity of hyperparasitoids is high and reduces the overall efficiency of E. lopezi.

The effect of CGM is prominent now, perhaps because of the reduction in CM. Exotic phytoseiid mite species were released but no establishment could be documented.

Investigations have been made to evaluate the development of Spodoptera littoralis as affected by feeding on a standard artificial diet containing powder of some plant species known to be resistant to the infestation of this insect. Trials were also made to find out whether the effect of these plants facilitate the potency of Bacillus thuringiensis var entomocidus HD-635 vs. the target insect. The results revealed that powders of pomegranate peel, guava leaves and lemon grass, greatly affected the insect development in terms of larval duration, larval and pupal weights, deformities in pupae and moths, percentage of emergence, egg production and hatching. This may be correlated to the chemical constituents of these plants. A marked increase was observed in the potency of B. thuringiensis endotoxin preparation vs. S. littoralis when combined with some of the tested powdered plants or its extracts but in varying degrees.

Storage method encompasses the patterns and periods of storage as well as particular storage techniques. Storage management is therefore a major determinant of post-harvest losses in stored cereals: affecting the magnitude of losses and their susceptibility to reduction. Key issues are the location and scale of grain storage which, in most developing countries, involves both rural domestic storage and larger seal “buffer” storage at district centres, commonly near towns.

Various storage techniques are described and discussed against the background of available informatio on storage losses and with regard to the common patterns and periods of storage in Africa at the farr level and in “centralized” storage. The importance of long-term development planning for cereal crop production and utilization is stressed as a major factor in storage pest management and the reduction of storage losses.

The handling of imported food grains is discussed with regard to storage management problems arising from moisture content/relative humidity equilibria as affected by grain temperature.

Greenhouse studies were conducted by artificially infesting potted rice plants with first instar larvae of Maliarpha separatella and Sesamia botanephaga Tarns and Bowden at two stages of plant growth, namely: early tillering stage and at the booting stage. Early infestation by M. separatella resulted in reduction of plant height and the number of filled grains. At the booting stage, the number of filled grains and their weight were higher in uninfested plants. Infestation by S. botanephaga at both stages of plant growth mainly affected the number of productive tillers. Grain weight was unaffected. Field studies on individual hills gave erratic results and there were instances when hills containing tillers bored by M. separatella produced higher yields than unattacked hills.

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.

Between May 1984 and December 1985, the population of immature stages of Anopheles arabiensis was sampled by the dip method at sites close to two villages in Mwea Irrigation Scheme, Kenya. Larval presence corresponded to rainy seasons and the flooding phase of the rice cycle. No larvae were found during the postharvest dry season. The instar composition, age distribution and survivorship curves for the different stages were determined. Pupal productivity for Mwea rice fields was estimated to be 1% of the total immature population.

Most germplasm lines and improved sorghum genotypes identified as resistant to shoot fly (Atherigona soccata Rond.), stem borer (Chilo partellus Swin.), midge (Contarinia sorghicola Coq.) and head bugs (Calocoris angustatus Leth.) are resistant to only one of these insects which usually will infest the same crop during the same season. At ICRISAT Center, India, a technique was developed in which entries were subjected to an array of combinations of pest infestations for identifying and separating genotypes with resistance to one or more insects.

Using this technique, 220 resistance sources and breeding lines were evaluated for multiple insect resistance. Less than 10% of shoot fly resistance sources had acceptable resistance (< 3 on a scale of 1–9) to shoot fly, but over 50% showed good resistance (scores of 1–3) to stem borer. IS 18551 and IS 2195 were the best entries with resistance to both shoot fly and stem borer. However, the majority (80–90%) of shoot fly and stem borer resistant sources were highly susceptible to midge with scores > 8. Similarly, all midge resistant sources were highly susceptible to shoot fly but less so to stem borer where seven midge lines had scores < 5. IS 22464 was the best midge line with a score of 3 for stem borer resistance. Advanced breeding lines showed a wider range of resistance to shoot fly, stem borer and midge with a higher frequency for resistance to stem borer, PS 28060−3 and PM 14388−1 were the most promising breeding lines.

The predacious mite, Cydnodromella negevi (Swirski & Amitai) completed life cycle when fed on the tetranychid mites Eutetranychus orientalis (Klein), Tetranychus urticae Koch and pollen grains of Ricinus communis (L.) as an alternative food substance in the laboratory. The duration of the immature stages and adult stage were determined. Immature stages of C. negevi consumed in total an average of 27 E. orientalis and 34 T. urticae, whereas each day throughout her life, the adult female consumed an average of 11 of E. orientalis and T. urticae. While feeding on these prey, C. negevi laid 1.3 and 1.0 eggs per day. The number of eggs deposited per day increased (3.3 eggs/female/day) when fed on eriophyid mites. Females neither fed nor reproduced on liquid nutrients.

The hormetic influence on silkworm, Bombyx mori L. (Lepidoptera: Bombycidae) of the juvenile hormone mimic ω-formyl longifolene oxime propargyl ether (NL13) was assayed. Emulsions containing 2.5, 5.0 and 10.0 ppm of the compound were administered topically as a single dose, to two popular commercial silkworm hybrids, viz. KA × NB4D2 and PM × NB4D2, at 24,48, 72 and 96 h into the 5th instar, and economic characters of the larvae and resultant cocoons measured. A medium and absolute control were maintained in parallel. It was found that administration of 5 ppm of NL13 to 48-h-old 5th instars resulted in the maximum improvement in commercial traits. The possible role of exogenous JH-like compounds in eliciting this response in silkworm is discussed.

Twenty-seven species of Chilo which infest graminaceous crops are listed. The effects of various cultural practices such as time of planting, plant density, field sanitation, tillage, mulching, intercropping, proper fertilizer and water management on field populations of Chilo spp. are discussed. These practices have great potential as components of IPM for resource-limited farmers in the tropics.

In recent years, the serpentine leaf miner Liriomyza trifolii (Burgess) has become a major pest of cotton (Gossypium spp.) in India, with high levels of incidence observed at the seedling stage, particularly in transgenic Bt cotton. We monitored the severity of infestation and damage by L. trifolii to transgenic and non-transgenic genotypes of Gossypium arboreum L. and G. hirsutum L. between 2002 and 2007. Overall, significantly lower L. trifolii damage occurred in G. arboreum varieties than in G. hirsutum varieties and hybrids. Among the G. hirsutum genotypes, damage was significantly lower in varieties than in hybrids. However, no significant differences in damage were observed between Bt and non-Bt cotton hybrids. Abiotic factors had a major influence on the severity of damage; there was a significant and negative association of L. trifolii damage with open pan evaporation (E), maximum temperature, solar radiation and sunshine, and a significant and positive association with relative humidity and rainfall (RF). Multiple stepwise regression analysis indicated that 99% of the variation in L. trifolii damage was accounted for by RF, open pan E and relative humidity.

Grass pea Lathyrus sativus L. plays a major role in the nutrition of many poor people in Ethiopia. However, the crop suffers heavy damage by pea aphids Acyrthosiphon pisum (Hemiptera: Aphididae). To test potentially more sustainable and harmless alternatives to the commonly used insecticides, some botanicals (neem, garlic and hot pepper), soap, kerosene and the aphicide pirimicarb, were tested for their efficacy against A. pisum at Wondata village, close to the town of Bahir Dar, in northwestern Ethiopia, from 1999 to 2002. After pirimicarb, hot pepper was consistently the most effective botanical in controlling the pea aphid in terms of both pea aphid population as well as grain yield. Compared to the untreated control, there was up to 83 and 55% lower aphid population on pirimicarb- and hot pepper-treated plots in the 2000/2001 cropping season, respectively. There was also up to 93 and 54% higher grain yield on plots treated with pirimicarb and hot pepper extract, respectively. Soap was less effective, while kerosene caused phytotoxicity. Infestation levels increased with advancing maturity of the crop, rising exceptionally suddenly and dramatically near crop maturity. Combined ANOVA over years and crop growth stages indicated that aphid populations varied with years and growth stages. In 2001/2002, aphid populations were higher and grain yields were lower compared with the other years. Percentage parasitism of aphids was significantly higher on pirimicarb-treated plots (∼40%) than other treatments (<20%). Parasitism was essentially a late-season occurrence. Predator population, especially of ladybird beetles (Adonia spp.), was especially higher on hot pepper- and garlic-treated plots, and lowest on pirimicarb treated plots. Grain yield was positively correlated with level of aphid parasitism, ladybird beetle population and number of pods per plant, and strongly negatively correlated with aphid population. In conclusion, a fresh extract of hot pepper sprayed at the rate of 70 ml/4 m2 was selected for further research on rate, frequency and cost of application.

Incorporated in this paper were the results of a study made on the quantitative variation of total carbohydrate, protein and lipid in whole body, fat body and integument of the larval and pupal developmental stages in rice moth, Corcyra cephalonica (St.) a storage grain pest. All three macromolecules referred to in case of whole body, exhibited a progressively decreasing trend from larva to pupa. In fat body total carbohydrate and protein contents were more in pupa than larva, while in integument the said nutrients were less in pupa than larva, showing the reverse results. The lowering down of the nutrients' level under stress caused by pyrethrum (a botanical insecticide) was also observed. The physiological and statistical significance of these findings was discussed.