The effects of ten major fungicides commonly used in paddy fields to control hyphal growth and spore germination of Erynia delphacis were examined. All fungicides inhibited both hyphal growth and spore germination of the fungus on the medium. Isoprothiolane inhibited hyphal growth and secondary spore formation even at low concentrations. Spraying isoprothiolane directly onto the green rice leafhopper (Neophotettix cincticeps) inhibited fungal growth, but spraying the fungicide onto rice plants, did not inhibit fungal growth. When the fungicide was sprayed on paddy fields, the population of diseased insects decreased. However, the population of the green rice leafhopper increased.

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Establishment and maintenance of high resistance to Bacillus thuringiensis formulations (BT) in the diamondback moth, Plutella xylostella were investigated using the diet incorporation method. Before beginning the selection, a field BT-resistant colony (ROO) collected from watercress in Kishiwada City (Osaka) was crossed with a susceptible colony (KUS) adapted to artificial diet, because the ROO colony could not be reared on the diet. Progenies from the reciprocal crosses of the ROO and KUS colonies were used for laboratory selection. Two BT formulations, Toarow^®-CT and one with Cry1Ac toxin were used independently for selection by incorporation into the diet. An extremely high level of resistance to each BT formulation was obtained within 10 generations by increasing the selection pressure. The resistance ratios of resistant colonies selected by Toarow^®-CT and Cry1Ac were >30, 000 and >45, 000, respectively, when compared to the KUS colony. When these two BT-resistant colonies were maintained without selection pressure, the resistance level was maintained for 20 generations, and then decreased gradually.

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To clarify the life cycle of Microcephalothrips abdominalis, the abundance of adults, the ovarian development of females, and the relative wing length of males captured both on flower heads of three species of Compositae in the field, and by water traps in Cosmos fields in Kyoto, were examined from 1991 to 1994. The effects of pollen-feeding and photoperiod on preoviposition period and fertility were investigated. Female adults were collected on flower heads throughout the year, but male adults were never found in winter. Most females had well developed ovaries from April to early October, but ovaries of almost all females were immature from late October to March. Females reared under short day length entered reproductive diapause. Macropterous, brachypterous, and intermediate forms were recognized in male adults. Macropterous females and males were collected by water traps, but brachypterous and intermediate males were never collected by the traps. Changes in male wing form composition showed no seasonal pattern. The wing form composition of males, the number of adults, and the adult sex ratio were different on different bloom stages. Female adults fed both leaf tissue and pollen had higher fertility and shorter preoviposition period than female adults reared without pollen.

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Microcephalothrips abdominalis lives on Compositae flower heads throughout its life. Males exhibit wing polymorphism. The relationships between wing form of males and the adult sex ratio, and the number of male and female adults on Cosmos flower heads were investigated. Furthermore, the effects of pollen-feeding on survival, development, and wing form determination, were examined under controlled conditions. In general, the proportion of brachypterous males was negatively correlated with the number of female adults, the number of female and male adults, and the proportion of female adults to male adults. The number of female adults, number of female and male adults, adult sex ratio, and proportion of brachypterous males depended on bloom states. Pollen-feeding had no effect on survival, developmental period, and wing form of males. The mean developmental period from egg to adult eclosion of males was 19 days at 18°C, 13 days at 25°C, and 10 days at 29°C. In females, the mean developmental period was 14 days at 25°C. At 25°C and 29°C, the preoviposition period and longevity of female adults were below 1 day and about 10 days, respectively. The relationship between wing polymorphism in males and resource utilization is discussed. It seems that wing polymorphism of males is closely related to mating strategies.

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The American Tadpole Shrimp, Triops longicaudatus, a possible biological weed control agent, was studied in paddy fields using conventional farming (with pesticides and chemical fertilizer) and organic farming methods at three localities in Hiroshima Prefecture. The results indicate that T. longicaudatus did not occur in six fields using organic farming, but occurred in five of 8 fields using conventional farming. To understand this difference, the seasonal abundance of T. longicaudatus and its predator aquatic insects was investigated. Preliminary results suggested no impact of predator aquatic insects on the abundance of T. longicaudatus in conventional and organic paddy fields. An experimental inoculation of 50 metanauplii of T. longicaudatus was conducted in artificial paddy containers using soil from conventional and organic farming methods. In the organic containers, all metanauplii died within 6 days of inoculation, but about 50% survived in the conventional containers. The water pH in the organic containers was approximately 4.9, much lower than that in the conventional containers, which was more than 6.3. A similar difference in pH was observed between conventional and organic paddy fields at HigashiHiroshima. These results suggest that the low pH of water in paddy fields using organic farming affects the survival of T. longicaudatus, especially young larvae.

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The American Serpentine Leafminer, Liriomyza trifolii (Burgess) was reared at 25°C on kidney bean, pakchoi, tomato, cherry tomato, celery, gerbera, chrysanthemum and melon, and at different temperatures on tomato. The pupation rates at 25°C varied from 56.2% on melon to 97.8% on kidney bean and were significantly different between crops. The adult emergence rates varied from 82.8% on celery to 96.5% on tomato. There were no large differences in the mean generation time between crops. Large differences in the net reproductive rate were found between crops, ranging from 25.21 on tomato to 271.99 on pak-choi. The intrinsic rates of natural increase on kidney bean, pak-choi, tomato, cherry tomato, celery, gerbera, chrysanthemum and melon were 0.2384, 0.2268, 0.1607, 0.1684, 0.2008, 0.1866, 0.1709 and 0.1429, respectively. The reproductive rates per day varied from 1.269 on kidney bean to 1.154 on melon. The hatchabilities on tomato were not significantly different between different temperatures, but the pupation rates and emergence rates were significant different between temperatures. The female fecundity varied from 3.3 at 15°C to 29.4 at 25°C, and female longevity was negatively correlated with temperature. The mean generation times varied from 55.85 at 15°C to 14.27 at 30°C. The net reproductive rate was 25.21 at 25°C, and the intrinsic rates of natural increase at 15°C, 20°C, 25°C and 30°C were -0.0042, 0.0655, 0.1607 and 0.0995, respectively. The population growth rate of L. trifolii was highest at 25°C.

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The dispersal of adults of Liriomyza trifolii in fields was studied using yellow sticky traps placed horizontally and vertically near an eggplant greenhouse severely infested by L. trifolii. The number of adults captured by the traps placed vertically 0.5-5.5m above the ground decreased with increased trap height. The number of adults captured by traps at 5.5m above the ground was from 0% to 0.2% of the total number of adults captured by all vertical traps. The number of adults captured by traps placed horizontally from east to west decreased with distance from the greenhouse. The number of adults captured by traps 48-m east of the greenhouse was from 1.4% to 1.9% of the total number of adults captured by all horizontal east traps. The sex of adults captured by traps was biased to males. The ratio of females was from 9.4% to 31.7% for vertical traps, and was from 9.1% to 29.9% for horizontal traps. Female ratio tended to decrease with the number of captured adults. There was a significant correlation between sex ratio and the number of captured adults.

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A trap for capturing Monochamus alternatus adults alive was devised by adding a plastic funnel to a commercial attraction trap. The funnel was set in a bucket to prevent collected adults from escaping. About 30% of collected beetles escaped from buckets with funnels per day on average under experimental conditions. Twenty-one traps were set in pine stands and captured beetles were collected every 3-4 days. The escape ratio during each census period was estimated at 34-56%, corresponding well to the value estimated from the laboratory experiment. On sunny summer days, the temperature in the buckets reached 45-49°C, which seemed to be lethal to the beetles. The maximum temperature in buckets covered with aluminum foil was about 6°C lower than in the uncovered bucket, but was still too hot to keep captured beetles alive.

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