Thrips tabaci Lindeman is an extensively distributed pest insect that injures a wide range of crops. To investigate the intra-specific genetic diversity of this species, we analyzed an 810 bp region of the mitochondrial cytochrome oxidase gene subunit I (COI). Eight populations from six foreign countries and 18 Japanese populations were tested, and 17 different haplotypes were identified. Apparent differences were found between arrhenotokous and thelytokous strains in their COI sequences. A phylogenetic tree of the COI gene shows two distinct groups. We assume that these two groups correspond respectively to the arrhenotokous strain and the thelytokous strain. Japanese thelytokous types consisted of five haplotypes. Two haplotypes were identified from problematic populations in terms of the greater amount of damage they caused and the development of insecticide resistance. Both haplotypes were also found overseas, suggesting that some strains from overseas may have caused the above-mentioned problems in Japan.

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The objective of this study was to identify the aggregation pheromone of the melon thrips Thrips palmi, a major pest of vegetable and ornamental plants around the world. The species causes damage both through feeding activities and as a vector of tospoviruses, and is a threat to world trade and European horticulture. Improved methods of detecting and controlling this species are needed and the identification of an aggregation pheromone will contribute to this requirement. Bioassays with a Y-tube olfactometer showed that virgin female T. palmi were attracted to the odour of live males, but not to that of live females, and that mixed-age adults of both sexes were attracted to the odour of live males, indicating the presence of a male-produced aggregation pheromone. Examination of the headspace volatiles of adult male T. palmi revealed only one compound that was not found in adult females. It was identified by comparison of its mass spectrum and chromatographic details with those of similar compounds. This compound had a structure like that of the previously identified male-produced aggregation pheromone of the western flower thrips Frankliniella occidentalis. The compound was synthesised and tested in eggplant crops infested with T. palmi in Japan. Significantly greater numbers of both males and females were attracted to traps baited with the putative aggregation pheromone compared to unbaited traps. The aggregation pheromone of T. palmi is thus identified as (R)-lavandulyl 3-methyl-3-butenoate by spectroscopic, chromatographic and behavioural analysis.

Improved laboratory methods are described in detail for mass rearing of various thrips species, such as Frankliniella occidentalis, Frankliniella intonsa, Thrips palmi, Thrips tabaci (Thysanoptera: Thripidae) and a thrips parasitoid, Ceranisus menes (Hymenoptera: Eulophidae), using various foods. In one method, plant pollen and honey solution are used as food sources. In a second method, germinated broad bean seeds are used. Eggs, produced in large numbers in water, are collected by a suction funnel onto a filter paper and incubated in a Petri dish. Large numbers of larvae that hatch are collected by using food traps (plant pollen). Larvae can be reared on pollen or on germinated broad bean seeds until adult emergence without additional water and food. This method has been found useful for producing even‐aged thrips at different densities (up to 500 larvae in a cage of 80 mm diameter) with relatively low mortality rates. Evaluation of this rearing method for F. intonsa, shows that during 2 weeks at 20 °C per 100 females more than 4000 females could be produced in the next generation. About 5 min per day is required to achieve this productivity of mass production. The method is also suitable for producing large numbers of the solitary endoparasitoid of thrips larvae, C. menes.

Flower thrips were reared on pollens and honey solution through thin membranes in glass vessels. Both sides of the glass vessels were covered with stretched Sealonfilm(R) membranes on which the thrips and pollens (of tea, pear, strawberry, tulip and pine) were placed. A drop of 10% honey solution was placed on the membrane and covered with another membrane to allow the insects to feed on the solution and lay eggs in it. Without pollen, young larvae of Frankliniella intonsa were unable to grow and adult females laid only a few eggs. The larval and pupal growth by artificial rearing was better than that on strawberry leaves and tomato fruits. The rate of emergence was higher than 85%. Thrips hawaiiensis could be also reared by the same method. Owing to the presence of pollens, flower thrips could lay large numbers of eggs and complete their whole life cycle. Mass rearing of flower thrips is practically possible by this method. Fig. 1. Rearing apparatus for flower thrips.