Antixenosis resistance to Helicoverpa armigera (Lepidoptera: Noctuidae) was studied in 10 tomato accessions selected from a germplasm of 321 at Tamil Nadu, India, using free-choice and no-choice laboratory experiments. The foliage and fruits of two accessions, namely PT 4287 and Varushanadu Local were the least preferred for feeding in both tests. In the no-choice (confinement) test, Seijima Jeisei, Varushanadu Local and PT 4287 were the most preferred for oviposition, but had low egg hatch rates. In the free-choice test, these accessions were the least preferred for oviposition. The first and second instars preferred to feed on the foliage of 30- and 45-day-old plants, respectively than 60- and 75-day-old plants, whereas ovipositional preference was insignificant among the various plant ages.

The survival of female Anopheles gambiae s.s. mosquitoes inside two village house types (grass-thatched and iron-roofed) was studied in relation to diet and ambient indoor microclimatic conditions. Two batches of 20–30, 1-day-old laboratory-bred mosquitoes were maintained inside cages in the grass-thatched (n=2) and iron-roofed (n=2) houses and fed daily, one group on 10% glucose and the other on human blood. Throughout the experiments, indoor temperature and relative humidity of the houses were recorded, and mortality of mosquitoes monitored daily until all had died. The experiments were replicated thrice. There was no significant variation in the overall mean temperature (P=0.93) or relative humidity profiles (P=0.099) between the two house types, although the iron-roofed houses recorded higher temperature peaks. A Kaplan–Meier survival analysis showed that the mean survival times of mosquitoes were 8 and 10 days in the two grass-thatched huts and 7 and 10 days in the two iron-roof houses for mosquitoes feeding on blood and sugar meals, respectively. The mean survival times of mosquitoes maintained inside similar house types differed only due to diet. In the proportionality of hazards model (Cox regression), the dietary regimes significantly influenced the probability of survival (P=0.0001), with mosquitoes surviving longer on sugar meals than on blood. Microclimatic factors inside houses also significantly influenced mosquito survival. Although higher peak temperatures were recorded in corrugated iron-roofed houses, the survival of the mosquitoes resting in them did not differ significantly from that in grass-thatched houses. However, the impact of these temperatures on the development of malaria parasites inside the vector needs to be investigated.

Trioza erytreae Del Guercio (Hemiptera: Triozidae) has been reported to be a major vector of the African huanglongbing, a form of citrus greening disease. In the tropical regions of Africa, factors regulating population changes of the pest within citrus orchards and plantations are almost unknown. This study carried out in an experimental plot of citrus orchard in Yaoundé, Cameroon, aimed at monitoring some climate and edaphic factors, which regulate the population changes of the pest. From January 1992 to December 1993, psyllids were counted weekly on flushing shoots and buds from 65 ten-year-old citrus trees. In 1992, the psyllid population changes revealed eight generations with three main peaks (January–March, April–September and September–December), and only three generations with one peak in 1993 (October–December). Among climate factors studied, higher maximum temperatures and saturation deficit index were negatively correlated with psyllid population. The shoot flushing rhythm within citrus trees was also highly correlated with psyllid population. In 1993, citrus trees were not weeded and no fertilizer was applied, and this led to disappearance of the pest from the plot and to a decreased number of annual generations from eight recorded in 1992 to three in 1993. Results from this study represent an important step towards the citrus psyllid ecology and the development of an integrated pest management programme for its control, with regard to weather conditions, cultural practices and host plant relationships.

Phytoplasmas are insect-vectored pathogens that cause characteristic and destructive diseases in carrots and other vegetables. A phytoplasma disease was first observed in Israeli carrot fields in 1995. Analysis of infected carrots showed the presence of aster yellows and western-X phytoplasmas. In this study, commercial and experimental fields in the western Negev region of Israel were monitored for three years using yellow sticky traps and vacuum sampling. Potential vectors of leafhoppers and planthoppers were analysed by PCR for the presence of phytoplasma DNA. Infected plants were also assayed for phytoplasma DNA. Extracted phytoplasma DNA was subjected to RFLP analysis to determine groups to which the phytoplasmas belonged. It was determined that carrots and leafhoppers from the experimental station were infected with a phytoplasma belonging to the Elm Yellows (EY) group; this is the first report of EY infecting carrots. Based on our findings, the two most probable insect vectors are Circulifer haematoceps complex (Mulsant & Rey) and Neoaliturus fenestratus (Herrich-Schäffer).

Lipids were extracted from the plasma and gonads of fourth and fifth instars and adults of Dysdercus koenigii (Heteroptera: Pyrrhocoridae). Thin layer chromatography of the extracts revealed fractions of free fatty acids (FFA), monoglycerides (MG), diglycerides (DG), triglycerides (TG), phospholipids (PL), free cholesterol (FC) and esterified cholesterol (EC). There were distinct differences in the lipid profiles within sexes for both tissues during development. Phospholipid from female plasma showed significant fluctuation during development, while that from males remained constant. In female gonads, PL levels increased significantly from the fouth instar to the fifth instar. Monoglycerides were detected only in adult male plasma and adult female gonads, at very low levels. Plasma DG in males was found to increase significantly during development. Maximum gonadal DG was recorded in male fourth instars and female fifth instars. Triglycerides in female plasma declined from the fourth instar to the adult stage. In contrast, TG in gonads increased significantly in the fifth instar of both sexes. Plasma FFA of both sexes fluctuated during development. Free cholesterol was detected only in adult male plasma. Plasma EC increased from the fourth instar to the adult stage in males, and it was highest in gonads of fifth instars of both sexes.

The banana weevil, Cosmopolites sordidus (Germar), is a nocturnal insect that is not readily observed in banana fields. Knowledge on its distribution is essential for the design of management strategies that target the adult stage. Marked weevils were released into seven-year-old banana plots. Ten days later the plots were systematically sampled for adult weevils by first removing the banana leaf mulch and residues, searching subsections of the soil to depths of 3 and 25 cm and, finally, removal and dissection of the banana mats. Of the marked weevils, 62, 56 and 82% respectively, were recovered in three trials. Most weevils were found in close association with either the banana mat (46–66%) or with cut residues lying on the ground between the mats (24–31%). Lesser numbers were found in the leaf mulch and in the top 3 cm of soil away from the mat. The distribution of weevils is likely to be influenced by crop management practices and the availability of residues and by the presence of mulch. Implications for banana weevil IPM are discussed.

Glasshouse studies were conducted to determine mechanisms of resistance of five genotypes of lentil Lens culinaris (Medikus) previously identified as resistant and moderately resistant to the pea aphid Acyrthosiphon pisum (Harris). A susceptible standard, ILL 8127, was also included. French Indigo had high levels of antibiosis, demonstrated by reduced reproductive period, fecundity and longevity, while Spanish Brown had high levels of antixenotic and tolerance components of resistance. Based on overall resistance, French Indigo was the most resistant genotype followed by Spanish Brown. These genotypes could be a source for resistance to A. pisum. All five genotypes had varying levels of antibiosis, antixenosis and tolerance components of resistance compared with ILL 8127.

Anthesizing male inflorescences of oil palms were randomly sampled for the oil palm-pollinating weevil Elaeidobius kamerunicus at the Nigerian Institute for Oil Palm Research (NIFOR) (field 56) in Benin City, Nigeria from March to September 2002. The weevils were counted and later examined for nematodes. There were no significant differences in the mean number of adult weevils sampled from various positions on the inflorescences, but there were significant differences in their mean numbers sampled on the various dates (P=0.001). Microscopic examination of adult weevils indicated that nematodes are associated with the weevils and the spikelets. This preliminary survey indicates that E. kamerunicus is a major insect pollinator of the oil palm in NIFOR oil palm plantations. Its association with parasitic nematodes may have a bearing on the weevil's pollination efficiency. These findings will help in understanding further the factors that govern pollination efficiency, percent fruit set and the occurrence of seasonal peaks in yields of fresh fruit from Nigerian oil palms.

Laboratory studies were carried out to investigate the role of larval habitat-derived microorganisms in the production of semiochemicals for oviposition site selection by Anopheles gambiae Giles sensu stricto mosquitoes. Dual-choice bioassays with gravid females were conducted in standard mosquito cages. Field-collected or laboratory-reared mosquitoes, individually or in groups, were offered a choice between unmodified (water or soil from a natural breeding site) or modified substrates (filtered water, autoclaved soil or sterile media to which bacterial suspensions had been added). Egg counts were used to assess oviposition preferences. Mosquitoes preferred to oviposit on unmodified substrates from natural larval habitats containing live microorganisms rather than on sterilized ones. Variable responses were observed when sterile substrates were inoculated with bacteria isolated from water and soil from natural habitats. We conclude that microbial populations in breeding sites produce volatiles that serve as semiochemicals for gravid An. gambiae. These signals, in conjunction with other (non-olfactory) chemical and physical cues, may be used by the female to assess the suitability of potential larval habitats in order to maximize the fitness of her offspring.

A modified technique to extract intact DNA from Aedes aegypti and Anopheles darlingi mosquitoes is presented. The samples were treated initially with proteinase K to digest all proteinaceous matter. For both vectors, the optimum temperature for the protease treatment was 55°C and the best pre-incubation time was 4 h. RNA contamination was eliminated with RNAse treatment. The purity of the DNA was high since the A260/A280 ratio averaged >1.80 for all samples and the quantity of DNA extracted was >1.6 times higher than that using the unmodified procedure. The DNA obtained displayed clear random amplified polymorphic DNA (RAPD) profiles, which indicates that it can be used for polymerase chain reaction (PCR)-based techniques.