Kei Kawazu

Geographical variation in female sex pheromones of the rice leaffolder moth, Cnaphalocrocis medinalis: identification of pheromone components in Japan

Sex pheromone components of the Japanese rice leaffolder moth, Cnaphalocrocis medinalis Guenée (Lepidoptera: Pyralidae) were identified from ovipositor extracts of virgin females as (Z)‐11‐octadecenal, (Z)‐13‐octadecenal, (Z)‐11‐octadecen‐1‐ol and (Z)‐13‐octadecen‐1‐ol at a ratio of 11:100:24:36 by GC‐EAD, GC, GC‐MS. The total amount was estimated to be ca.0.9 ng/female. Field bioassays in Kagoshima, Japan, showed that the two aldehydes are essential for male attraction and the alcohols may have a synergistic effect on the aldehydes. A rubber septum containing 0.9 mg of the four components at the natural ratio was shown to be an effective lure for monitoring this pest in Japan. The above four components are quite different from the sex pheromone components reported previously for the same species of either Philippine or Indian origin; components were shown to be (Z)‐11‐hexadecenyl acetate and (Z)‐13‐octadecenyl acetate at a ratio of 98:2 in the Philippine blend and 1:10 in the Indian blend. Furthermore, in the field tests in Japan, neither the Philippine blend nor the Indian blend showed any attractive activity, while the Japanese blend attracted significant numbers of male moths. These results suggest that there are remarkable geographical variations in the sex pheromone composition of this species or there are several distinct species using different sex pheromone blends.

Tobacco MAP Kinase Phosphatase (NtMKP1) Negatively Regulates Wound Response and Induced Resistance Against Necrotrophic Pathogens and Lepidopteran Herbivores

Mitogen-activated protein kinase (MAPK) cascades are universal signal transduction pathways in eukaryotic cells. In tobacco, two MAPK, wound-induced protein kinase (WIPK) and salicylic acid (SA)-induced protein kinase (SIPK), are activated by biotic and abiotic stresses. Both WIPK and SIPK positively regulate the biosynthesis of jasmonic acid (JA) or ethylene (ET) while negatively regulating SA accumulation. We showed previously that recombinant tobacco MAPK phosphatase (NtMKP1) protein dephosphorylates and inactivates SIPK in vitro, and overexpression of NtMKP1 repressed wound-induced activation of both SIPK and WIPK. To elucidate the role of NtMKP1 in response to biotic and abiotic stresses, we generated transgenic tobacco plants in which NtMKP1 expression was suppressed. Suppression of NtMKP1 expression resulted in enhanced activation of WIPK and SIPK and production of both JA and ET upon wounding. Wound-induced expression of JA- or ET-inducible genes, basic PR-1 and PI-II, was also significantly enhanced in these plants. Furthermore, NtMKP1-suppressed plants exhibited enhanced resistance against a necrotrophic pathogen, Botrytis cinerea, and lepidopteran herbivores, Mamestra brassicae and Spodoptera litura. These results suggest that NtMKP1 negatively regulates wound response and resistance against both necrotrophic pathogens and herbivorous insects through suppression of JA or ET pathways via inactivation of MAPK.

Comparison of attractiveness in Japan and China of three synthetic pheromone blends based on geographic variations in the rice leaffolder, Cnaphalocrocis medinalis (Lepidoptera: Pyralidae)

Field bioassays using three different synthetic sex pheromone blends (Indian, Philippine and Japanese) based on geographic variations of Cnaphalocrocis medinalis Guenée were carried out at 11 sites in Japan and in Hangzhou, China. In all of the tests, only the Japanese pheromone blend attracted a significant number of male moths, while the Indian and Philippine pheromone blends showed no marked activity. The findings in Japan showed no evidence that moths of Philippine or Indian origin were able to migrate to Japan. The results from China also showed that most populations of C. medinalisin the Hangzhou region responded to the Japanese blend. This is consistent with the current hypothesis that most populations of C. medinalisin Japan are migrants from areas to the south of the Yangzhe Valley, including the region surrounding Hangzhou, China. Furthermore, populations in the Hangzhou region can not hibernate, but are considered migrants from the southernmost parts of China and southeast Asian countries such as Vietnam where they breed continuously. Consequently, at least some populations in these areas may respond to the Japanese pheromone blend.

Suitability of Monocots for Rearing Alien Coconut Pest Brontispa longissima (Coleoptera: Chrysomelidae)

ABSTRACT The suitability for larval development of the alien coconut pest Brontispa longissima (Gestro) (Coleoptera: Chrysomelidae) on the following 15 monocots was investigated. Arecaceae: Cocos nucifera, Trachycarpus wagnerianus; Typhaceae: Sparganium erectum, Typha latifolia; Poaceae: Avena sativa, Echinochloa esculenta, Hordeum vulgare, Oryza sativa, Sorghum bicolor, Zea mays; and Cyperaceae: Carex morrowii, Cyperus alternifolius, Cyperus esculentus, Cyperus serotinus, and Rhynchospora colorata. The larval survival rate to the adult stage was significantly higher when reared on C. esculentus and C. serotinus (95%); however, it was not significantly different compared with C. nucifera (75%). Sixty, 45, 45, and 10% were observed when reared on T. wagnerianus, S. erectum, T. latifolia, and C. alternifolius, respectively. The larval developmental period reared on C. serotinus was as short as on C. esculentus and on C. nucifera up to adult emergence. The fecundity of adults was examined using C. nucifera, T. wagnerianus, T. latifolia, C. esculentus, and C. serotinus as food plants. In these five plants, the females reared on T. wagnerianus started to lay eggs earliest. However, the preoviposition periods on C. esculentus and C. serotinus were not significantly different from those on C. nucifera and T. latifolia. Numbers of eggs laid per female did not differ significantly among these five plants. Our present results suggest that T. wagnerianus, C. esculentus, and C. serotinus can be used as new food plants in addition to C. nucifera and T. latifolia for rearing B. longissima.

Rearing the 28-spotted ladybird beetle, Henosepilachna vigintioctopunctata (Coleoptera : Coccinelidae), with a switchover from host plant leaves to artificial diet

In this study, I tested an artificial diet, Insecta LFS, for rearing the 28-spotted ladybird beetle, Henosepilachna vigintioctopunctata (Fabricius). H. vigintioctopunctata larvae could not be reared through all of the larval stages on the artificial diet. However, initially they could be reared on tomato leaves up to the second or third instar, and thereafter exclusively on the artificial diet. The larval and pupal periods were not significantly different from those reared only on tomato leaves. For females reared by the diet-switching method, the preoviposition period was significantly longer and the number of eggs laid significantly lower than for those on tomato leaves. However, these differences did not become a hindrance to laboratory rearing. This rearing method saves labor involving obtaining fresh plant leaves and produces a reliable supply of the insects.

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.

Effects of mixed cropping on population densities and parasitism rates of the diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae)

Effects of mixed cropping and barrier crops on the population density and parasitism of the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), were evaluated in field plots of cabbage grown in Bali, Indonesia. The densities of P. xylostella at larval and pupal stages, as well as the overall density at larval plus pupal stages, were significantly lower in cabbage/coriander mixed cropping subplots than in cabbage monoculture subplots. Parasitism of P. xylostella by the larval parasitoid Diadegma semiclausum (Hellen) (Hymenoptera: Ichneumonidae) was not significantly different between the mixed and monocultural cropping systems. These results do not support the so-called enemies hypothesis, but suggest that disruption of the host searching behavior of female moths by neighboring non-host plants is the mechanism behind the associational resistance observed in the coriander mixed cropping system. The inclusion of a Napier grass barrier between mixed crop and monoculture subplots did not affect the influence of mixed cropping on larval and pupal densities. Therefore, Napier grass, which is used locally as a fence for preventing livestock invasion of fields, would not obstruct the pest-reducing effect of coriander/cabbage mixed cropping.

Photoperiodic induction of prepupal diapause and its role in synchronization with host phenology in the hibiscus caterpillar, Xanthodes transversa

The hibiscus caterpillar, Xanthodes transversa (Lepidoptera: Noctuidae), is a multivoltine insect that is an important pest of Malvaceae plants such as the okra, Abelmoschus esculentus, and the common rose mallow, Hibiscus mutabilis, in Japan. In the present study, the effects of photoperiod and temperature on the induction of prepupal diapause and the adaptive significance of this diapause were examined in a local population of X. transversa in Miyazaki, Kyushu, southwestern Japan. Larvae showed a long‐day photoperiodic response for controlling the induction of prepupal diapause with a critical day length between 13 and 14 h at 20 to 25°C. Under long‐day conditions larvae rapidly pupated from the sixth instar, but under short‐day conditions they entered diapause in the prepupal stage. Diapause occurrence in the field increased in late September, which was consistent with the laboratory results in terms of the photoperiodic response. Non‐diapause development after this time is maladaptive because most larvae of the next generation could not reach the critical stage (prepupae) before winter and died during early winter in outdoor experiments. Larvae suffered from a high rate of mortality when fed leaves collected late in autumn. The photoperiodic response for controlling the induction of diapause in this insect may play an important role in synchronizing the life cycle with the seasonal changes in food and temperature conditions.

Effect of multiple mating on the reproductive performance of the rice leaffolder moth, Cnaphalocrocis medinalis (Lepidoptera: Crambidae)

To clarify whether multiple mating of females and males affects the reproductive performance of the rice leaffolder moth, Cnaphalocrocis medinalis (Guenée), we examined the effect of the number of matings (once, twice, or three times) for females (female treatment) and males (male treatment) on the incidence of moth mating, number of eggs laid, egg hatchability, and adult longevity. We also compared the effect of multiple mating imposed on males or females separately with the effect of that imposed on both sexes simultaneously (both sexes treatment). The incidence of mating of females and males that mated three times (3-mated females and males) was significantly lower than for females and males that mated twice or once (2-mated or 1-mated females and males). The incidence of mating of 1-mated moths (both sexes) was significantly higher than for 2-mated or 3-mated moths (both sexes). Two-mated or 3-mated females laid significantly more eggs with significantly higher hatchability than 1-mated females. Females that mated with 1-mated males (second male mating) or 2-mated males (third male mating) laid significantly fewer eggs than those that mated with virgin males (first male mating). Females laid significantly more eggs after the second and third matings for moths of both sexes than after the first mating for moths of both sexes. The mechanisms of improvement and decline of female reproductive performance when multiple mating was imposed on males or females are also discussed in relation to the reproductive biology of C. medinalis.

Polyandry increases reproductive performance but does not decrease survival in female Brontispa longissima

The costs and benefits of polyandry are still not well understood. We studied the effects of multiple mating on the reproductive performance of female Brontispa longissima (Coleoptera: Chrysomelidae), one of the most serious pests of the coconut palm, by using three experimental treatments: (1) singly-mated females (single treatment); (2) females that mated 10 times with the same male (repetition treatment); and (3) females that mated once with each of 10 different males (polyandry treatment). Both multiple mating treatments resulted in significantly greater total egg production and the proportion of eggs that successfully hatched (hatching success) than with the single mating treatment. Furthermore, the polyandry treatment resulted in greater total egg production and hatching success than with the repetition treatment. Thus, mate diversity may affect the direct and indirect benefits of multiple mating. Female longevity, the length of the preoviposition period, the length of the period from emergence to termination of oviposition, and the length of the ovipositing period did not differ among treatments. The pronounced fecundity and fertility benefits that females gain from multiple mating, coupled with a lack of longevity costs, apparently explain the extreme polyandry in B. longissima.