Introduction. L’acarien Oligonychus afrasiaticus, localement appelé « Boufaroua », est un ravageur des palmeraies algériennes. Pour se nourrir, il pique les dattes qui se dessèchent ensuite en fin de maturité et deviennent impropres à la commercialisation et à la consommation humaine. Des pertes économiques importantes sont alors enregistrées. Les dégâts les plus spectaculaires ont été notés sur la variété Deglet-Nour à haute valeur marchande. Matériel et méthodes. Le taux d’infestation des arbres d’une palmeraie de la région d’Ouargla a été évalué. Quatre stades phénologiques ont été considérés. Une coccinelle très vorace, Stethorus punctillum, a été récoltée dans six palmeraies puis lâchée sur des arbres expérimentaux afin de vérifier son efficacité prédatrice sur le « Boufaroua ». Résultats. L’infestation des arbres a été très variable et a augmenté au fur et à mesure de la maturité des dattes. L’efficacité de la coccinelle lâchée a été significative, et cela a été d’autant plus constaté que les arbres étaient fortement infestés. Discussion et conclusion. Stethorus punctillum joue un rôle important dans le contrôle de l’acarien O. afrasiaticus. D’autres prédateurs seraient toutefois présents en Algérie ; ils devront être testés afin d’établir une méthode de lutte biologique apte à protéger suffisamment les palmeraies contre O. afrasiaticus.

The influence of temperature on the age-specific fecundity of an aphidophagous ladybeetle, Micraspis discolor (Fabricius) (Coleoptera: Coccinellidae) feeding on the cowpea aphid, Aphis craccivora Koch (Homoptera: Aphididae) at four different temperatures, viz. 20, 25, 27 and 30 °C, was investigated. The age-specific fecundity function was triangular and oviposition rate (no. of eggs/ day) increased with increase in reproductive age of the ladybeetle, attaining a peak then gradually decreasing before finally ceasing. Young adults were more efficient at converting aphid biomass into eggs than older ones. The oviposition peak tended to shift towards younger females and the oviposition rate increased with increase in temperature from 20 to 27 °C. The maximum fecundity and percent egg viability was 750 eggs and 95 % at 27 °C and minimum 385 eggs and 65 % at 20 °C, respectively.

The developmental, oviposition, and mortality rates for the polyphagous earwig Diaperasticus eryihrocephala Olivier feeding on pollen and Ephestia kuehniella Zeller eggs were measured at constant temperatures of 18, 25 and 32 °C. The developmental period for D. erythrocephala required 533 degree-days (DD) above a threshold of 6.7 °C. Egg and larval development rates increased with increasing temperature, with the shortest developmental period being recorded at 32 °C. However, egg and larval mortality and larval malformation rates were significantly higher at 32 than at 25 and 18 °C. Over a period of 60 days, females laid an average of 26.5 eggs at 25 °C and none at 18 °C. Based on the results obtained, it is concluded that of the three temperatures, 25 °C is the most suitable for the laboratory mass rearing of D. erythrocephala.

A wide variety of Hemiptera species are found on the leaves of palms in humid tropical zones. Many of them are highly polyphagous, and generally once adult, only accidentally end up on palm leaves, on which they can nevertheless feed. Other hemipterans spend the whole of their developmental cycle on palms, and some seem to live on palms alone. Most of the Hemiptera have no economic impact on their hosts, since their population levels are rarely high enough to cause significant damage. However, some Heteroptera: Coreoidea and Homoptera: Coccoidea species can be very damaging primary pests. Others amongst the Homoptera: Fulgoroidea, Cicadelloidea and Heteroptera: Pentatomoidea transmit serious diseases that have decimated oil palm and coconut plantations, for example coconut lethal yellowing in Africa and the Caribbean, and oil palm and coconut trypanosome diseases in Latin America. Lastly, some Heteroptera: Pentatomoidea and Reduvioidea species are natural enemies of lepidopteran caterpillars.

The stemborers Busseola fusca (Fuller) (Lepidoptera: Noctuidae) and Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae), are the most important pests of maize and grain sorghum in South Africa. Parasitoids, pathogens and predators curtailed populations of B. fusca and C. partellus on the crops but their activity was not enough to reduce pest populations to below-economic-damage levels. They also could not prevent the dispersal and subsequent widespread distribution of C. partellus after its introduction into South Africa. Nine parasitoids and hyperparasitoids have been recorded attacking both borer species. These parasitoids are probably more habitat-specific with regard to foraging for hosts than they are host-specific, as they appear to have moved from their indigenous hosts to use C. partellus as a new alternative host. Between 1977 and 1993 three braconids, one eulophid, three ichneumonids, two trichogrammatids and four tachinids were introduced into South Africa from 11 countries for biological control of stemborers. Recoveries of parasitoids were made only short periods after releases and in the vicinity of the release sites. Cold and dry winters, with night temperatures often falling to below freezing, prevail in the Highveld Region which is the major summer-grain-producing area of South Africa. These conditions, and the fact that borers enter diapause in the dry stalks for 7 months in winter, when the crops or other alternative host plants such as grasses do not grow, hamper the establishment of exotic natural enemies in the Highveld Region.

In order to develop suitable sampling methods for the arthropods of four mint species, namely Japanese mint (Mentha arvensis L.- var. Hybrid 77), peppermint (M. piperitaL.-var. MP-1), bergamot mint (M. citrata Ehrhrt- var. Kiran) and spearmint (M. spicata L.- var. MSS-5), six general sampling methods viz. ground cloth, sticker, sweep net, water trap, whole plant observation (WPO) and whole plant harvest (WPH) were evaluated under field conditions at the Research Farm of Central Institute of Medicinal and Aromatic Plants, Lucknow, India. The mint pest complex on all the mint species included Aphis craccivora, Chrotogonus trachypterus, Leptocorisa varicornis, Coccinella septempunctata, Bemisia tabaci, an unidentified lygeid bug, Brumoides suturalis, Propylea dissecta, Crysolina exanthematica, Dysdercus cingulatus and Plusia orichalcea. Overall, the ground cloth, sweep net, water trap and sticker methods were found to be more efficient and successful for sampling the arthropods of mint crops than the WPO and WPH methods. The shortest sampling time was required when using the sticker (3–6 seconds per sweep) and the sweep net (7–8 seconds per sweep) methods. This information may be useful in developing an integrated pest management programme for mint.

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 main effects of gall midges in tropical agriculture are as primary pests of cultivated plants; as predators on pests, especially mealybugs, scale insects and mites; as potential biocontrol agents of weeds and as pollinators of cocoa. Published information is briefly reviewed under these main headings, with particular emphasis on the sorghum midge, Contarinia sorghicola (Coquillett), on the Asian and African rice gall midges, Orseolia oryzae (Wood-Mason) and O. oryzivora Harris & Gagné and on cecidomyiid predators on mealybugs and scale insects.