In this study, the basic biology of and artificial rearing techniques for Bactrocera pyrifoliae (Drew and Hancock), a pest of peaches and plums in high-elevation areas of northern Vietnam and Thailand, were investigated for 5 years. Bactrocera pyrifoliae was found only between elevations of 1000 and 1500 m, heavily infesting peaches and plums from early June to harvest in mid-July. The durations of the egg, larval and pupal stages were determined under controlled environmental conditions in the laboratory, indicating that B. pyrifoliae is a multivoltine species. Larvae were successfully reared on a carrot and corn powder-based diet. Determinations of the appropriate adult density in colony cages, and also optimal temperature conditions for holding adults, were made. Bactrocera pyrifoliae performed better when the temperature was lowered during the night, as would be expected for a species adapted to temperate-like environments. Interestingly, adults originating from field-collected pupae emerged with a 3:1 female-biased sex ratio. Laboratory colonies, by generation seven, appeared to exhibit signs of inbreeding depression and required periodic incorporation of wild insects to restore egg hatch. To develop sound management techniques for populations of B. pyrifoliae infesting peaches, alternate commercial and native hosts infested outside the peach and plum fruiting season must be identified or some form of overwintering mechanism such as reproductive diapause be discovered. Documentation of mating behaviour in the field (a key to developing efficient traps), improvement in fertility in laboratory colonies, and eventually sterile insect technique-based integrated pest management for pest population management in the expanding low-chill temperate fruit-growing areas of northern Vietnam are also needed.

Experiments carried out in a coffee plantation to determine the developmental period of Icerya paltersoni (Newst.) showed that the female and male scales lasted 157 and 129 days on average, respectively. The different stages of I. pattersoni females were found to be recognizable by the number of antennal segments. The antenna of the stage I nymphal instar is six segmented, stage II is nine segmented and stage III is eleven segmented. The antenna of adult males is eighteen segmented. Females are neotenic but the males possess a pair of grey wings and atrophied mouthparts. In the field the I. pattersoni pest population size is highest in the heavy rainfall months of April and May.

Field studies revealed the nettle caterpillar, Latoia ( = Parasa) viridissima, to be multivoltine with four discrete generations a year. The maximum egg (1800/100 fronds) and larval (1500/100 fronds) densities were attained in April/May 1980. The pupal population was generally low; the highest recorded density of 54/100 fronds was attained in March 1980 during the first generation.

Samples of larvae and pupae from the field were attacked by parasitoids in the families Bombyliidae, Braconidae, Chalcididae, Chrysididae, Eulophidae, Ichneumonidae and Tachinidae. These contributed to mortalities ranging from 6 to 30%, but their combined action with microorganisms (bacteria and fungi) accounted for 28–65% mortality of the insect.

The immature stages of the predaceous mite Typhlodromus talbii Athias-Henriot are described. The mite was reared on different prey species and pollen in the laboratory, and its developmental parameters calculated. Tydeus californicus (Banks) was found to be the most suitable and nourishing diet, giving a shorter life cycle and higher female fecundity (8.8 days and 33.4 eggs respectively), than the scale insect Coccus acuminatum (Gennadius) (10.0 days and 24.8 eggs respectively) at 25 °C. Other associates of Typ. talbii, the eriophyid Cesaberoptus kenyae Keifer, the tetranychid Oligonychus mangiferus (R. & S.) as well as date palm and castor oil pollen, were unsuitable diet. When reared on moving stages of Tyd. californicus (Banks) at 70 ± 5 % RH, 16:8 (L:D) h photoperiod and temperatures of 15,20,25,28,30,32 and 35 °C, the total developmental time of Typ. talbii averaged 21.3, 12.4, 8.8, 7.6, 7.1, 5.8 and 11.6 days respectively. The intrinsic rate of natural increase (rm) and the net reproduction (Ro) reached maximum values of 0.299 individuals per female per day and 28.06 times respectively, at 32 °C.

Parasitization of P. brassicae L. by A. glomeratus L. was found to be between 63.79 and 76.52% in Farm 1 and 92.68 and 93.43% in Farm 2. Population density of the parasitoids ranged between 35.16 ± 6.05 and 57.76 ± 13.20. The developmental period of the parasitoids within the host was 21 days and the pupal period 9 to 10 days. The population of the parasitoid showed a steady increase during November–December. The rate of pupation of P. brassicae showed a decline from 36.21% in mid-November to 23.48% in later November in Farm 1 with an early crop. In Farm 2 with a late crop the pupation rate dwindled from an already low 7.32 to 6.57% by late December.

Four cultivars of maize, Zea mays L. viz., CM 600, Basilocal, CM 500 and Kisan were examined for their relative resistance to the maize stem borer, chilo partellus (Swinhoe) in relation to nutrition. Freshly hatched larvae of C. partellus were allowed to grow on the leaf whorls of the cultivars in the laboratory at 27 ±.2°C and 70–90% r.h. The rate of growth, food consumption and its utilization, egg laying and egg hatchability were studied. The insects showed better growth when fed CM 600 or Basilocal maize; this was shown by a higher percentage pupation (56.8 and 54.8, respectively on CM 600 and Basilocal) as compared to (24.4 and 5.6 respectively) on CM 500 and Kisan. Pupal weights were higher (40.2, 45.2, 34.4 and 32.8 mg for male pupae and 57.6, 63.7, 51.8 and 35.8 mg for female pupae), when larvae were reared on CM 600, Basilocal, CM 500 and Kisan, respectively. The growth index decreased from 1.65 on CM 600 and 1.49 on Basilocal to 0.40 on CM 500 and 0.09 on Kisan. A better consumption and utilization of the cultivars CM 600 and Basilocal was shown as also expressed by the higher weights attained by larvae grown on these two than on CM 500 and Kisan. Growth rate slowed down to 0.068 on CM 500 from 0.161 on CM 600 maize. A similar trend was observed in egg-laying and hatchability of eggs. Number of eggs laid per female decreased from 290 on CM 600 reared C. partellus to 157 on Kisan reared insects and none of the eggs laid by the latter could hatch. The degree of resistance of the cultivars to C. partellus on the basis of nutritional factors in a decreasing order is: Kisan > CM 500 > Basilocal > CM 600.

Transgenic plants expressing Bacillus thuringiensis δ-endotoxins are now being used commercially in several crop species. These toxins have demonstrated good control of temperate (Ostrinia nubilalis) and tropical (Diatraea grandiosella and D. saccharalis) stemborers in maize. Resistance to B. thuringiensis toxins has been reported in over 11 species in both field and laboratory studies, demonstrating the need for resistance management strategies to prolong the efficacy of this valuable pest management tool within an integrated control programme. Resistance involves reduced binding of toxins to midgut epithelial cells and is generally considered to be a recessive trait. Resistance management will require the use of spatial and temporal refugia which may require unique schemes for each pest complex. Information is presented on the mode of action of cry toxins, resistance mechanisms, interaction of transgenic plants and biocontrol agents, and management/deployment strategies for transgenic maize in tropical ecologies.

Pearl millet, Pennisetum americanum L. occupies a large proportion of the area growing millets in Africa. Consequently the insect pests that attack this species have received attention over other millets. A list of the major species is presented. Actual data on losses due to insect pests on pearl millet are not readily available. Crop loss assessment methods using incidence and damage ratios are discussed. Quantitative losses determined from insecticide trials at research station are also presented.

Preferences of Maruca vitrata (Fabricius) (Lepidoptera: Pyralidae) larvae to flowers, flower buds and pods of three different varieties of cowpea (IT 82E-666, IT 82D-716 and Botokpoyi) were studied in the laboratory using a four-branched olfactometer. For each plant part, fourth instars of M. vitrata were individually exposed to a set of three odours obtained from the cowpea varieties with pure air serving as the control. Movements of the larvae in the exposure chamber were followed at two levels of choice. Results from the first level of choice showed that the attractiveness of a particular plant part to M. vitrata larvae was not significantly influenced by variety. At the second level of choice a weakly significant preference was found for flowers (P = 0.1218) compared to pods (P = 0.7530) and flower buds (P = 0.6172). In all cases, no significant difference was found between the control (pure air) and the varieties.

Available pieces of information on Cicadulina sp. leafhopper biology, with specific references to the suitability of various species for mass rearing and resistance screening for maize streak virus (MSV) are critically reviewed. The following are summarized: (a) effect of distribution pattern and species composition on the efficiency of collection of live specimens for establishing a colony for mass rearing; (b) species biology and fecundity as affected by temperature and humidity; (c) species specificity in MSV transmission; (d) host plant preference and adaptation to mass rearing conditions. All these parameters affect the suitability of various Cicadulina species used as vectors in maize resistance screening and breeding to MSV disease.

Evaluations of toxicity, antifeedant, growth-regulatory activity of the methanol extract of Gliricidia sepium leaves were carried out against Dysdercus koenigii Fabr. (Heteroptera: Pyrrhocoridae), Achaea Janata Linn, and Spodoptera litura Fab., (both Lepidoptera: Noctuidae). Topical application of 100-300 μg of the extract to different stages of the test insects resulted in dose-dependent effects including larval-pupal intermediates and deformed adults. The highest tested dosage (300 μg/ μl) resulted in reduced survival rate and morphological abnormalities. At certain doses a strong antifeedant activity was evident against the lepidopteran insects.

Four species in the genus Amblyseius Berlese are reported from Tanzania, A. serengati sp.n., A. fustis Pritchard and Baker, A. largoensis (Muma) and A. sawaga Pritchard & Baker. Descriptions and comparisons with similar species are provided for the new species.

Investigations of the phlebotomine sandflies fauna in a visceral leishmaniasis focus of Aba Roba in Ethiopia were carried out. This resulted in finding Phlebotomus celiae for the first time in the country. Previously, this species was incriminated as a vector of visceral leishmaniasis in Kitui, Kenya where the disease is endemic. It is possible that P. celiae has a wide distribution covering areas of similar ecological niches as those of its first description.

Mussidia nigrivenella Ragonot is the main cob borer of maize in Ivory Coast. An accurate description of male and female genitalia is given. Rearing in the laboratory has permitted determination of the number and duration of the pre-imaginal instars, fecundity of adults and fertility of eggs as also the sex-ratio. An artificial diet has been elaborated which provides conditions of similar development to those observed in the field: The insect has 5 to 6 larval instars and the total duration of development from the egg-laying to the adult emergence is 46 days for the male and 49 days for the female.

The green cassava mite, Mononychellus tanajoa (Bondar) and the red spider mite, Tetranychus urticae Koch infest all varieties of cassava in Sierra Leone. Both tetranychid species are widely distributed in the country and are causing severe damage to the crop mainly in the major cassava producing areas in the north-western regions. M. tanajoa caused chlorosis and 91° loss in photosynthetic area of the attacked leaves and defoliation of the plant either by acting alone or in concert with T. urticae. Late planted crop was particularly vulnerable to the infestation. M. tanajoa and T. urticae appeared to avoid severe interspecific competition on the plant by habitat stratification.

Investigations were carried out on the seasonal population fluctuations of the moth Cydia ptychora. The population increased from May to September and declined from November to April. Increasing temperatures and decreasing r.h. appeared to be associated with population decline, while the reverse seemed to favour population increase.

From light trap catches, sex ratios of adults showed considerable variation from month to month. The overall ratio was 2:1, in favour of the males, but there was a tendency for adjustment towards an apparently female-biased ratio from March to August.

Bracon (?) hancocki was found to be a major parasite. Other biotic factors contributing to population regulation included 13 hymenopterous parasites and three predators (Philodicus temerarius, Bactria sp. nr. guineensis and Chrysopa sp.)

The effects of various exposure to irradiation from cesium 137 in nitrogen and air on survival and fecundity of Glossina palpalis palpalis were compared. With doses from 3 to 21 krad in nitrogen atmosphere, male fertility was inversely correlated with dose, above 15 krad male survival was inversely correlated with dose. All males subjected to either 21 krad in nitrogen or 15 krad in air were sterilized. Females appeared to be more sensitive to gamma-irradiation than males; a dose of 6 krad in nitrogen resulted in 100% sterility and arrested further development of the ovaries after the ovulation of follicles A1 and C1. In males, this dose caused 70.3% sterility. Approximately 97 and 98% sterility were obtained when males were treated with 15 krad in nitrogen and 12 krad in air respectively. No fly emerged from irradiated puparia younger than 15 days. Irradiation of 15 or 20 days old puparia killed the insect either before or shortly after eclosion, whereas the normal patterns of emergence, survival and reproduction were observed from puparia that were irradiated when 25 days old or older.

The corn earworm damage to seven maize cultivars TZB, TZPB, WYI, 096EP6, Farz 25, ‘Kewesoke’ and Local White, was assessed during the early and late cropping seasons of 1980 and 1981 at Ikenne and Ilora located in the rain-forest and derived savanna zones, respectively. The effectiveness of dimethoate and permethrin in controlling the earworms was evaluated. All the cultivars appeared susceptible to earworm infestation in the two ecological zones. Infestation was consistently and significantly higher in the early season and also in the rain-forest zone. It ranged from 71.5 to 86% in the early and from 28 to 36.8% in the late seasons, respectively, at Ikenne. At Ilora, infestation ranged from 53 to 82% and from 20 to 75% in the early and late seasons, respectively. Mussidia nigrivenella and Heliolhis armigera were the dominant species recorded damaging the grains.

Earworm infestation was significantly lower on plots treated wtih three applications of 0.05 and 0.1% a.i. permethrin at weekly intervals than on plots that received the same dosages and sprays of dimethoate and the control. Maize yields were significantly higher on permethrin-treated plots. The lower dosage of permethrin is recommended to reduce chemical residue on maize grains.

The biophysical characters of the mosquito, Culex quinquefasciatus, a dreaded vector of bancroftian filariasis was investigated. The data represents the “system” in bioaerodynamics which comprises the adult mosquito and induced air, and constitutes “action-reaction pair” for the hovering flight. Hence the static and dynamic parameters of this species are determined. An expression for moment of inertia of the flight surface (wing) is deduced considering wing design and geometry. Further aerodynamic requirements in relation to flight performance of the insect are elaborated. It is concluded that this study provides useful information on the hovering flight behaviour of the mosquito C. quinquefasciatus.