So far, seven species of Rhyacionia Hübner have been recorded in Japan. Among them, five species, R. dativa Heinrich, R. washiyai (Kôno and Sawamoto), sp. rev., R. pinivorana (Lienig and Zeller), R. simulata Heinrich, stat. rev. and R. vernalis Nasu and Kawahara, were really found in Japan, but the occurrence records of the remaining two, R. pinicolana (Doubleday) and R. buoliana ([Denis and Schiffermüller]), were expunged, because they were elucidated to be based on the misidentification of R. washiyai and R. dativa, respectively. R. washiyai types were discovered, and the lectotype was designated here and preserved in the National Science Museum, Tokyo, Japan. The species was treated as a junior synonym of R. dativa; however, they are quite different species. R. washiyai is externally similar to R. pinicolana distributed in Europe and Russia, but it is distinguishable from the latter in having a cucullus without a ventral process in the male genitalia. R. simulata was treated as a subspecies of R. duplana (Hübner); however, it is regarded as an independent species in having peltate signa instead of horn-shaped ones in R. duplana in the female genitalia. Matsumura treated Evetria buoliana in his book published in 1917, but he used another name, E. japoniella Matsumura, in the figure legend of the species. The name japoniella was treated as a junior synonym of R. dativa; however, the name was unavailable as per articles 11.6 and 11.6.1 of the International Code of Zoological Nomenclature (4th edition) because it was originally published as a junior synonym of buoliana and was not adopted as the name of a taxon before 1961. The adults and genitalia of the Japanese species were illustrated, and the distinguishing characteristics among the species and keys to species based on external and genitalic characteristics were given.
The laboratory choice test demonstrated that adult Trigonotylus caelestialium preferred panicles of Poa annua to rice panicles. Females showed a clearer preference in food plants than males. Field-cage experiments showed that adult T. caelestialium produced fewer pecky rice grains when rice plants were placed among vegetation containing food plants than when placed among vegetation without food plants and that the number of pecky grains produced decreased as the rice-growing stage proceeded regardless of the presence or absence of the food plant. P. annua was continuously in heading from late May to early September under field conditions in Sapporo. When the weed was mowed during this period, it regrew and heads developed 2–3 weeks after being trimmed. Food plant management and control of P. annua to reduce the damage of pecky rice grains caused by T. caelestialium were discussed.
The stomach contents of the Japanese tree frog, Hyla japonica, captured in soybean fields, were analyzed to examine whether this frog species is a beneficial natural enemy. From 101 frog stomachs, 1,545 prey items were identified. The diet consisted of a wide variety of arthropods. Aphids predominated in the diet, making up 67.2% of total prey. Leaf beetles and catarpillars were also found frequently in stomach contents. These insects are probably pest species, although most prey items were not identified at the level of species; therefore, H. japonica could be considered a beneficial natural enemy of various soybean pest species. In order to increase the density of H. japonica and enhance the effect of pest control by predation, soybean fields should be placed near rice fields where H. japonica spawns, to attract the frog after spawning and metamorphosis.
To examine the effects of ripening stage and the occurrence of split-hull paddies of rice plants on the development of Trigonotylus caelestialium nymphs, the nymphs were reared on two rice cultivars, Wasejiman and Koshihikari, that exhibit a high and low rate of split-hull paddies, respectively. The nymphs were released on a caged ear with stem and leaf at each of the four rice stages, i.e., at heading and 10, 20 or 30 days after heading, and 10 days after release, the numbers of surviving nymphs, split-hull paddies and injured rice grains were counted. Numbers of split-hull paddies were 0 at the stage of heading and few at 10 days after heading. Survival rates of nymphs were high at the stage of heading and low at 10 days after heading. At 20 and 30 days after heading, Wasejiman exhibited larger numbers of split-hull paddies and supported higher survival rates of T. caelestialium nymphs than Koshihikari, although these values varied yearly. There is significant positive correlation between the number of injured rice grains and survival rates of nymphs at these ripening stages, indicating that nymphal development certainly depends on feeding on the rice grains. Most injured grains were found in split-hull paddies, and the survival rates of nymphs were significantly correlated with the number of split-hull paddies. It is considered that nymphs primarily feed on rice grains from the split part of paddies. It is suggested that the occurrence time and the number of split-hull paddies cause fluctuation in the density of T. caelestialium nymphs in paddy fields.
The life cycle of Hypsopygia postflava, a moth parasitic on nests of the paper wasp Polistes jokahamae, was studied in Mie, Saitama and Tokyo in 2002 and 2003. The emergence of some overwintered-generation moths was extremely delayed, and some second-generation larvae overwintered without pupation; therefore, it is considered that this nest-parasitic moth typically completes three generations per year, with some completing only one or two generations. The proportion of male adults per nest was 56.4% on average, and ranged from 30.8% to 75.0%, but did not differ significantly with the nests. The head widths of overwintering moth larvae varied greatly between the nests and also within some of the nests. Larvae with a head width of <1.08 mm died during overwintering. Larvae provided with pupae of the paper wasp in glass vessels developed to adults, but those provided only with nest materials or the feces of paper wasps did not.
A laboratory method to evaluate the effectiveness of ultraviolet (UV) protectant for Bacillus thuringiensis (Bt) product (Esmark-DF WDG) was investigated using a commercial fluorescent lamp (FL20S·E, peak 315 nm: ranges 270–370 nm) and bioassay with the silkworm, Bombyx mori. A one-litter solution (1 g/1,000 ml) of Bt product was prepared in a glass beaker and exposed to fluorescent lamps at 5 cm below for 1–4 days. The bioactivity of irradiated Bt solution against the 2nd instar of silkworms was measured based on larval growth inhibition using the diet incorporation method. Percent growth inhibition was calculated by comparing weight gains of survivors at three days between the irradiated and non-irradiated solutions. The bioactivity of Bt solution was clearly decreased according to the exposure periods of fluorescence lamps. UV protective activity of iron oxide black (Fe3O4) for Bt solution was examined in the same manner and confirmed that it possessed effective UV protective activity dose-dependently. When 0.1% iron oxide black was mixed with Bt solution (1 g product/1,000 ml), it could reduce the inactivation from UV irradiation by 1/10 as compared to without it.
Effects of fipronil bait (0.5%) on sugarcane wireworm Melanotus sakishimensis Ohira were evaluated in laboratory and field experiments. A laboratory experiment comparing the efficacy of fipronil bait with 1% fipronil granules indicated that the fipronil bait actually attracts and kills wireworms. In field experiments, the number of damaged sugarcane buds was significantly reduced by application of fipronil bait (6 kg/10 a), as well as by 3.2% carbosulfan granules (9 kg/10 a). The frequency of healthy underground buds after harvest was significantly higher in fipronil bait application (6 kg/10 a and 9 kg/10 a) at the planting compared with the application of 5.0% carbosulfan granules (9 kg/10 a). These results suggest that the fipronil bait is effective for wireworm control and may facilitate higher sugarcane stalk yields and ratoon success rates.
The effect of mating status and adult age of the rice leaf bug, Trigonotylus caelestialium, on the attractiveness of females to males was investigated. A trap baited with virgin females tended to attract more males than one baited with mated females. This result indicates that the sex pheromone emitted by females may decrease after mating. Furthermore, more males tended to be captured in the trap baited with virgin females at three days after emergence compared with those aged six days. This result suggests that the sex pheromone emitted by virgin females may decrease with age.
In 2001 and 2002, dispersal by the flight of adult yellow tea thrips, Scirtothrips dorsalis Hood was studied using yellow sticky traps placed in tea groves and in an adjacent lawn, i.e., an open space. At the peak of the population density for each generation of S. dorsalis adults inhabiting the tea groves, the number of adults captured in each trap reached its peak. The number of S. dorsalis adults captured using the traps decreased with the increase in distance from the tea groves for each generation. These results suggest that S. dorsalis adults actively make shorts flights when their population density increases at their reproduction sites. The sex ratio (number of females/total number of males and females) of the adults captured by the traps was significantly biased toward females as compared to those inhabiting the tea groves.