Mika Murata

Different expression profiles of jasmonic acid and salicylic acid inducible genes in the tomato plant against herbivores with various feeding modes

We compared the expression profiles of jasmonic acid (JA)-inducible genes (Pin2 and LapA1) and salicylic acid (SA)-inducible genes (PRb-1b and GluB) in the tomato (Solanum lycopersicum cv. Micro-Tom) against herbivores using differing feeding modes: the leaf-chewing larvae of the insects Spodoptera litura and S. exigua; the western flower thrips (Frankliniella occidentalis) and the two-spotted spider mite (Tetranychus urticae) as cell-content feeders; and the leaf miner fly (Liriomyza sativae). Feeding by larvae of both S. litura and S. exigua chiefly activated JA-inducible genes, similar to the response to wound stimuli. Feeding by the thrips F. occidentalis also activated JA-inducible genes, as previously reported in Arabidopsis. Feeding by the spider mite T. urticae activated a JA-inducible LapA1 gene but did not activate a JA-inducible Pin2 gene and additionally activated SA-inducible genes, which were accompanied by the accumulation of SA. This may be a strain that represses induction of the JA signaling pathway. One day after oviposition by the leaf miner fly, L. sativae, JA-inducible genes were activated. However, after the L. sativae larvae hatched and began eating within the leaf tissues, JA-inducible gene expression decreased and SA-inducible gene expression increased. Activation of SA-inducible genes (PRb-1b and GluB) by L. sativae larval feeding seems to suppress JA-mediated plant defense but appears to be unrelated to SA accumulation.

Parasitisation of Tetrastichus brontispae (Hymenoptera: Eulophidae), a biological control agent of the coconut hispine beetle Brontispa longissima (Coleoptera: Chrysomelidae)

Abstract The gregarious endoparasitoids Tetrastichus brontispae Ferrière is one of the important natural enemies of the coconut hispine beetle Brontispa longissima (Gestro), a serious invasive pest on coconut palm plants (Cocos nucifera L.) in Southeast Asia. Development at different temperatures, effect of host and female ages, effect of food and oviposition frequency and superparasitism were investigated in the laboratory. Females were allowed only one attack against one host in all experiments. The wasp developed in a host between 19 and 30°C, whilst no wasp completed its immature development at 16 and 31°C. Host and female ages affected parasitisation. Parasitoid emergence was high on day 0 and day 1 pupal hosts, and younger females produced more offspring than older females. The longevity of the female was affected not only by food supply, but also by oviposition frequency. The female survived longer when oviposition frequency was low. However, the total number of hosts parasitised by the female during her lifetime did not differ at different oviposition frequencies. In superparasitism, although the percentage of adult emergence and body size of offspring decreased with an increasing number of attacks per host, a host parasitised by up to four females could produce parasitoid offspring.

Comparative developmental and reproductive biology of geographical populations from two cryptic species in Brontispa longissima (Coleoptera: Chrysomelidae)

Brontispa longissima is a serious pest of the coconut palm Cocos nucifera, presumed to have originated in Papua New Guinea and Indonesia. It recently invaded Southeast and East Asia, where outbreaks have been reported. Mitochondrial DNA analysis reveals two cryptic species in B. longissima: one is distributed over a wide area including Asia and the Pacific region (the Asian clade) and the other in a limited area in the Pacific region (the Pacific clade). Recent invasions and outbreaks have been reported only from the area where the Asian clade has been found, suggesting that this clade has become a pest in Asia. To infer if the Asian clade has the ability to establish, spread and outbreak in novel habitats more effectively than the Pacific clade, we compared life‐history traits between the two populations of different clades. The net reproduction rate (R0) was 130.0 and 94.0, the mean length of a generation (T) was 57.7 and 54.7 days, and the intrinsic rate of natural increase (r) was 0.084 and 0.083 per day for the population from Ishigaki Island, Japan (ISH) (the Asian clade) and for the population from Papua New Guinea (PNG) (the Pacific clade), respectively. Although the difference in r was little, the simulated population growth showed that the ISH population can be 1.6 times larger than that of the PNG after ten generations. The rapid population growth of the Asian clade would be partly responsible for its establishment, spread and frequent outbreaks in Asia.

Infestation and Development of Sitophilus spp. in Pouch-Packaged Spaghetti in Japan

Abstract Infestation of pouch-packaged spaghetti by Sitophilus oryzae (L.) (Coleoptera: Curculionidae) was observed in Japan in May 2006. It was suggested that 30% of all shipped pasta products sustain damage to the packages heat-sealed before reaching retail stores. Hence, we investigated the mechanisms by which S. oryzae and Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) adults invade pasta packaged in polypropylene pouches. In the damaged packages, both species entered through the breaks in the seal and laid their eggs on the pasta. However, in the intact packages, the adults of both species bit around air vent holes in the film, but they did not make the holes big enough for entry into the pouch. We also compared each species’ developmental periods from oviposition to emergence in pasta and brown rice (Oryza spp.). The average developmental period of both species at 25°C was shorter in rice than in pasta. The number of individuals emerging from brown rice was significantly higher than that from pasta. Finally, we suggested a measure to prevent infestation by insect pests in pouch-packaged pasta products.

Artificial diets for rearing the coconut hispine beetle, Brontispa longissima (Coleoptera: Chrysomelidae), and their suitability to two specialist parasitoids

Abstract The coconut hispine beetle, Brontispa longissima (Gestro), is a serious invasive pest that infests young unopened fronds of coconut palms (Cocos nucifera L.) in Southeast Asia. We previously developed the first artificial diet for rearing B. longissima larvae, which contained a leaf powder of young coconut fronds. Because the fronds are required for healthy growth of coconut palms, it is necessary to reduce their use for rearing the beetles. In this study, we tested two new artificial diets for the beetle larvae, which contained the leaf powders of mature coconut leaves or orchard grass (Dactylis glomerata L.). Brontispa longissima successfully developed from hatching to adulthood on both the mature coconut leaf diet and orchard grass diet. The beetles reared on the mature coconut leaf diet and orchard grass diet developed faster than those reared on the young coconut leaf diet. Fecundity and egg hatchability of beetles did not differ among the three diet treatments. We then examined the suitability of beetle larvae or pupae reared on each diet as hosts for two specialist endoparasitoids, Asecodes hispinarum Boucek and Tetrastichus brontispae Ferriere. The survival rate from oviposition to adult emergence for A. hispinarum was 43.8% in hosts reared on a young coconut leaf diet, 77.1% on a mature coconut leaf diet, and 85.7% on an orchard grass diet. For T. brontispae, the survival rate was 70.0% in hosts reared on the young coconut leaf diet, 38.1% on the mature coconut leaf diet, and 66.7% on the orchard grass diet. Our results indicate these artificial diets can be useful for rearing B. longissima and its two parasitoids, helping to reduce the costs of mass rearing these insects.

A Comparison of Artificial Diets for Mass Rearing Brontispa longissima (Coleoptera: Chrysomelidae) as Hosts for the Larval and the Pupal Parasitoids

ABSTRACT The coconut hispine beetle, Brontispa longissima (Gestro) (Coleoptera: Chrysomelidae) is a serious pest of coconut palm. In this study, we developed an artificial diet for B. longissima so that the beetle could be used as a host for rearing two of its parasitoids, Asecodes hispinarum Bouček (Hymenoptera: Eulophidae) and Tetrastichus brontispae Ferrière (Hymenoptera: Eulophidae). The new artificial diet represents an improvement of our previous diet, which we used as a control. When beetle larvae were reared on the new diet, which contains cysteine but not cellulose powder and has twice as much coconut leaf powder as in the control, the adult emergence was 71% (≈2 times that in the control). We also examined the suitability of beetles fed on the new diet as hosts for the larval parasitoid A. hispinarum and the pupal parasitoid T. brontispae. The percentage of wasps that emerged from hosts that were fed the new diet was higher than that from the control-fed hosts. The new diet allowed both A. hispinarum and T. brontispae to produce adult wasps of the next generation, whereas the control only allowed T. brontispae to produce the next generation. These results suggest that the new diet is suitable for B. longissima and will facilitate mass-rearing of A. hispinarum and T. brontispae.

Age in relation to copulation, egg development, and multiple mating behavior in the coconut palm pest Brontispa longissima (Coleoptera: Chrysomelidae)

ABSTRACT To clarify the reproductive properties of the coconut palm pest, Brontispa longissima (Gestro) (Coleoptera: Chrysomelidae), we investigated in the laboratory the diel periodicity in copulation, effect of adult age after emergence on copulation and ovarian development, reproductive development in relation to female age, and the possibility of multiple mating. The beetles used in this study were reared in the laboratory and were fed an alternative food plant, narrowleaf cattail, Typha domingensis Pers. (Typhaceae). Copulation occurred throughout the 24-h cycle but mostly occurred in the photophase with two peaks, one at the onset of lights-on and the other 8–12 h after lights-on, indicating that most copulation activity in B. longissima in the field occurs in the early morning and the afternoon. Females could copulate immediately after emergence, whereas males began copulating 3 wk after emergence. Ovaries of females started to develop in the absence of mating and were correlated with adult age. Mature males could copulate with females regardless of ovarian developmental stage, and females with undeveloped ovaries accepted copulation attempts. Our study showed that the timing of copulation during the preoviposition period would not affect numbers of eggs laid, length of preoviposition period, or viability of eggs. B. longissima adults engaged in multiple mating.

Effect of Larval Density on Development of the Coconut Hispine Beetle, Brontispa longissima (Gestro) (Coleoptera: Chrysomelidae)

The coconut hispine beetle, Brontispa longissima shows, aggregation in the field. To elucidate the effect of aggregation on larval developmental aspects, we examined the effects of larval density on various aspects of larval development and on survival rates. Recently we found that B. longissima was divided into two monophyletic clades by genetic analysis. Therefore, we also compared the results between two populations, from Ishigaki, Japan (ISH) and Papua New Guinea (PNG), which were representative of the two monophyletic clades of B. longissima. In both ISH and PNG, the larval developmental period was shorter and the survival rate higher with rearing under high-density conditions than under isolated conditions. Similarly, fewer instars were required before pupation under high-density conditions than under isolated conditions. Brontispa longissima therefore developed better under high-density conditions, and the trends in the density effect were similar between two monophyletic clades.

Suppression of the stored-product pest Sitophilus zeamais (Coleoptera: Curculionidae) by simultaneous release of a predatory bug and a parasitoid wasp

ABSTRACT The control of the maize weevil, Sitophilus zeamais in brown rice was estimated by using a reduviid bug, Amphibolus venator, and a pteromalid wasp, Theocolax elegans. Results showed that the simultaneous release of both species of natural enemies could enhance biological control compared with the release of either species alone.

Effects of constant and fluctuating temperatures on development of the coconut hispine beetle, Brontispa longissima (Coleoptera: Chrysomelidae) and two species of parasitoid

Abstract The larval parasitoid Asecodes hispinarum Bouček has been used to control the coconut hispine beetle, Brontispa longissima (Gestro) in Vietnam. Although A. hispinarum has succeeded in suppressing B. longissima in southern Vietnam, biocontrol has not succeeded in central Vietnam. One factor underlying this failure might be the high temperature during the hot season. In the present work, we examined whether A. hispinarum parasitises the beetles within the range of temperatures that occur during the hot season in central Vietnam and we evaluated the potential use of the pupal parasitoid Tetrastichus brontispae Ferrière. Development of the beetle and two parasitoids was investigated at two constant temperatures (28 and 30°C) and at fluctuating temperatures from 25 to 35°C (corresponding to temperatures during the hot season in central Vietnam). B. longissima reached adulthood in all the temperature treatments. More than 70% of A. hispinarum emerged from hosts at 28°C, but none emerged at 30°C or under fluctuating temperature conditions, indicating that A. hispinarum cannot be used as a biological control agent in central Vietnam. However, T. brontispae could reproduce the next generation at all temperatures. These results suggest that T. brontispae is a potential agent for continuous biological control of B. longissima in central Vietnam.