Tamotsu Murai

Evaluation of an improved method for mass-rearing of thrips and a thrips parasitoid

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.

Methyl anthranilate as an attractant for two thrips species and the thrips parasitoid Ceranisus menes.

The role of floral scents in host location by flower-dwelling thrips and a thrips parasitoid was investigated by experiment in the field. The scent of methyl anthranilate significantly increased the catches of Thrips hawaiiensis, Thrips coloratus, and Ceranisus menes, but had no effect on Thrips tabaci. Anisaldehyde increased the catches of T. hawaiiensis and T. tabaci, but had no such effect on T. coloratus and C. menes. Geraniol increased the catches of T. hawaiiensis, but not of T. coloratus, T. tabaci, or C. menes. Seasonal fluctuations of T. hawaiiensis, T. coloratus, and C. menes can be recorded by using methyl anthranilate as a lure for monitoring.

Specificity of accumulation and transmission of tomato spotted wilt virus (TSWV) in two genera, Frankliniella and Thrips (Thysanoptera: Thripidae)

The accumulation and transmission of tomato spotted wilt virus (TSWV) was examined in second instar larvae and adults of two thrips genera, Frankliniella and Thrips. The species tested were F. occidentalis (Pergande), F. intonsa (Trybom), T. tabaciLindeman, T. setosus Moulton, T. palmi Karny and T. hawaiiensis (Morgan). In a standard petunia leaf disc assay, the efficiencies of TSWV transmission by two species of Frankliniella were higher than those of any Thrips species in the adult stage. A triple antibody sandwich enzyme-linked immunosorbent assay (TAS-ELISA) showed that large amounts of the TSWV-nucleocapsid (N) protein were present in the ELISA-positive larvae of each species, with the exception of T. palmi. The ELISA titre of and the proportion of virus-infected individuals of the two Frankliniella species increased or did not significantly change from the larval to the adult stages, whereas those of the four Thrips species decreased significantly. These results show that the specificity of virus transmission by adult thrips is probably affected by the amount of viral N protein accumulation in the adults and that the accumulation pattern from the larval to the adult stages is in between the two genera tested in the present study.

Life history study of Thrips setosus

Development, reproduction and population growth of Thrips setosus Moulton (Thysanoptera, Thripidae), reared on a leaf of kidney bean, was studied under six different constant temperatures, and the effect on reproduction of short photoperiod during immature stages was examined. Survival rates from hatch to adult were more than 67.5% at temperatures between 17.5 and 27.5 °C, but less than 55% at 30 °C. Developmental rates increased linearly as rearing temperature increased. A total of 181.1 degree‐days, above a developmental zero of 12.5 °C, were required to complete development from egg to adult oviposition. These data were related to records of field temperatures in Kurashiki in western Japan, and an estimate produced that, under outdoor conditions, a maximum of between seven and 12 generations could have developed annually between 1990 and 1999. There were no significant differences in mean adult longevity and mean fecundity among three temperatures (20, 22.5 and 25 °C). The intrinsic rate of natural increase (rm) was 0.1997 at 25 °C. Reproductive diapause was induced by a photoperiod less than 12 h at 20 °C.

Host-Parasite Interaction between Frankliniella intonsa , Western Flower Thrips and Ceranisus menes (Hymenoptera: Eulophidae): Development and Reproduction

The life history of the endoparasitoid, Ceranisus menes (Walker) (Hymenoptera: Eulophidae) was studied in the laboratory on Frankliniella intonsa and western flower thrips (WFT). Parasitoid development and reproductive capacity depended on temperature. Development is synchronized with larval development of the host and is faster on WFT than on F. intonsa. There is a marked variation in pupal duration of C. menes at 20 and 25°C. Average longevity of C. menes did not differ between WFT and F. intonsa at 25°C. Fecundity was 2.5 times as high with WFT as hosts than with F. intonsa. The intrinsic rate of increase (r m ) of C. menes on WFT was higher than that on F. intonsa at both temperatures, but was lower than those of the thrips hosts. It is suggested that multiple releases will be needed to control F. intonsa or WFT outbreaks.

Apterous males and holocyclic reproduction of Lipaphis erysimi in Japan

KAZUO KAWADA & TAMOTSU MURAI~: Apterous males and holocyclic reproduction ofLipaphis erysimi in Japan. The turnip aphid, Lipaphis erysimi Kaltenbach is a destructive pest of cruciferous crops. However, the complete life cycle of this aphid has not yet been described. Apterous males, oviparous females and fundatrices of L. erysimi have been reported in Europe (Bodenheimer & Swirski, 1957, Mfiiler, 1955). In India, oviparous females have been recorded from Cherrapunji and Kalimpong (Basu et al., 1970), and a single alate male has been found in the Kashmir region (Verma & Mathur, 1966). In New Zealand, a single oviparous female was discovered in Auckland (Cottier, 1953). In Japan, oviparous females and fundatrices were previously found in Ise (Sorin & Shinohara, 1972) and oviparous females in Kyoto (Takada, 1976). In this paper we report the observation of holocyclic L. erysimi in the field in Japan, and laboratory rearing of all morphs. We also provide the first detailed description of apterous males of this aphid. We started field surveys in October 1975. In the Kurashiki district (34.36°N, 133.43°E) some 250 km W of Ise and Kyoto, turnip aphids were found to reproduce parthenogenetically throughout the year, and even in the cold winter, viviparous females were seen on radish leaves in the field, but no sexual forms were observed. In the Saigo area (36.12°N, 133.19°E) of the Oki Islands about 180 km NW of Kurashiki, oviparous females and apterous males were found on field radish leaves on October 14, 1976. A few days after mating, eggs were found on the leaves usually along veins. Fundatrix larvae hatching from eggs that had overwintered were first observed on April 5, 1977. The fundatrix adults began to produce offspring toward the end of April, and parthenogenetic reproduction lasted until September or in some cases October. In our laboratory fundatrix larvae hatching from eggs that had overwintered in the field in Saigo were first observed on March 3, 1977, and they were used to initiate our laboratory culture. The apterous fundatrigeniae produced by these apterous fundatrices were isolated until birth of the next third generation, their offspring were isolated in turn, and the process repeated until the line ended. Rearing was carried out under a short photoperiod of 8 hr light per diem at a constant temperature of 15 ° with fresh radish leaves every 5th day. Under these conditions a succession of apterous viviparae was reared for eight generations. Alate viviparae were produced in other culture lines in which the aphids were crowded. Apterous sexuparae appeared in the ninth generation, and oviparous

Ceranisus menes (Hymenoptera: Eulophidae) for Control of Western Flower Thrips: Biology and Behavior

The potential of Ceranisus menes (Walker) for control of western flower thrips (WFT) was evaluated in the laboratory. A method is described for rearing thrips and parasitoids, using bean pods as host plants and different Frankliniella species (schultzei, WFT) as hosts. Strains collected worldwide, differed in biology and behavior, according to their phenotypic appearance (color form) and geographical origin. Analysis of behavior showed that host acceptance is related to stage, size and movement of the host larva. As size increased, fewer were attacked and parasitized successfully. First instar WFT were preferred, and yellow strains of the wasp were more effective than brown ones. Yellow types produced more offspring but showed a larger variation in developmental time than brown types.