A pitfall trap baited with sweet potato, Ipomoea batatas (L.), was developed to collect adults of the West Indian sweet potato weevil, Euscepes postfasciatus (FAIRMAIRE) in the field. Addition of 20 males or 20 females to the baited trap did not increase the trap efficiency. The number of captured weevils per trap decreased with days after planting sweet potato plants, suggesting that the nearby presence of potato tubers and stems affects the trap attractiveness. Few weevils were captured in fields where sweet potato plants had been transplanted more than one month earlier. The rate of weevils escaping from the traps after capture was higher in sweet potato fields than in grassland. The recapture rate after marking was 80% when captured weevils were released 1m from the trap, 13% at 10m, and 0% at 25m. In conclusion, the pitfall trap is effective for estimating the abundance and movement of this weevil in sweet potato fields soon after transplanting.

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We developed a computer simulation model predicting the efficiency of Phytoseiulus persimilis ATHIASHENRIOT as a biological control agent of Tetranychus urticae KOCH. This model consisted of two main sets of 17 state variables, one for the predator and the other for the prey. The changes of these variables were calculated by difference equations using various rate variables which had appeared in the reports of many authors. Two particular components in the present model were a dispersal (or cannibalism) rate of the predator depending upon female prey density and a coefficient which decreases predation rate depending upon the features of the plant. These were thought to be important to predict actual state of biological control by computer simulation and should be evaluated by experimental and simulation studies in the future.

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Validity tests of the simulation model developed in the previous report (SAITO et al., 1996) using two sets of experiments under two different greenhouse conditions revealed that the model was able to precisely predict the dynamics of predator-prey interactions with minor changes in a few variables: On strawberry plants in a well regulated glasshouse, when the predator searching efficiency was decreased to 87% of the standard value and the ratio of prey female and predator female at which the predators begin to disperse was ca. 7:1, the dynamics of predator-prey populations were well simulated. On cucumber plants in a vinyl-house under free-ranging temperature conditions, 30% decrease in searching efficiency and 20% decrease in sedentary rate were necessary to simulate the most fitting pattern of predator-prey dynamics. These changes in rate variables were thought to be reasonable considering the differences in features and sizes of the plants. Therefore, the present model appears to be useful in demonstrating the controlling process and predicting the result of biological control. Several environmental and biological factors which should be determined before biological control is implemented were also discussed.

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The developmental period, fecundity and diapause attribute of a synthetic pyrethroids-organophosphate-carbamate resistant strain (SEL10) of the predatory mites, Amblyseius womersleyi SCHICHA were compared with several indigenous strains. There was little difference in the developmental periods at 25°C between four strains. The fecundity was compared between five strains using the number of eggs oviposited for 3 days by ten females at 5-6 days after adult emergence. The fecundity of the SEL10 strain was significantly higher than that of the HK and FL94 strains. There was a large variation in the diapausing rate at 18°C under 9L-15D between strains. The strains (OKI and ISHI) originating from Okinawa Prefecture showed a very low diapausing rate. Hatchability and survival rates were more than 90% and 85%, respectively, regardless of the crossing. No reproductive incompatibility was observed at inter-strain crossing. This indicates the possibility of breeding a new resistant strain of A. womersleyi by hybridization and selection for release into deciduous fruit trees or into glasshouses with short day length.

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Liriomyza trifolii and its hymenopterous parasitoids emerging from collected leaves of vegetables and ornamental crops in Shizuoka Prefecture, Japan, were examined. The parasitoid complex was abundant both in open fields and greenhouses. However, few or no parasitoids emerged from crops treated with some pesticides some time before the survey. The parasitoid complex was composed of 16 species: three braconids, nine eulophids, two pteromalids, one eucoilid and one aphelinid. Four eulophid species, Hemiptarsenus varicornis, Chrysocharis pentheus, Neochrysocharis okazakii and N. formosa, were predominant. H. varicornis seemed to be the most important parasitoid species in greenhouses. In a greenhouse, applications of the selective pesticides, buprofezin, pyridaben, dicofol, fenyroximate, fenbutatin oxide and flufenoxuron, conserved the parasitoid complex and the leafminer population was suppressed subsequently. Applications of the nonselective pesticides, permethrin, methomyl, ethophenprox and prothiofos, destroyed the parasitoid complex and an outbreak of the leafminer followed. One month or more was needed for recovery of high parasitism by the parasitoids after application of nonselective pesticides.

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The paedogenetic gall midge found in 1984 at a factory for the oyster mushroom in Miyazaki Prefecture was identified as Mycophila speyeri by comparison with six known species of the genus Mycophila in the world. It is a known pest of mushrooms in Europe and Taiwan. To confirm whether or not M. speyeri was naturally distributed in Japan prior to the finding, the unsorted collections of the tribe Micromyini to which Mycophila belongs were examined at Kyushu and Kagoshima Universities. No Mycophila was found in 3, 395 adult specimens collected in 1966-95 from various localities in Japan by sweeping possible habitats. A survey of 40 factories revealed that three indoor mushroom factories in Nagano Prefecture experienced an outbreak of the gall midge in 1983-84 while there was no sign of an attack in outdoor cultivation. The factories had all bought “Nameko” Pholiota nameko spawns from the same source. These results suggest that larvae of M. speyeri reached to the factories in spawn introduced from overseas.

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The infection routes and effect of the entomogenous fungus, Beauveria brongniartii GSES on the yellow spotted longicorn beetle, Psacothea hilaris were investigated using a conidial suspension and nonwoven fabric sheet containing the fungus, in the laboratory and fig tree fields. The conidial suspension was smeared at a density of 7.1×10⁷ conidia/ml on the antennae, ventral abdomen, tarsi and mouth of adult beetles. Irrespective of the treated part, beetles were infected, but, application on the antennae, tarsi and ventral abdomen was more effective (70%-90% mortality) than on the mouth (30% mortality). When adult beetles were allowed to walk for 5 seconds on the fabric sheet containing 10⁸ conidia/cm², the quantity of conidia on the adult beetle was 10⁷ conidia/beetle. Quantities of 10⁷, 10⁵ and 10⁴ conidia/beetle were detected when beetles walked for 60 seconds on sheets containing 10⁸, 10⁶ and 10⁵ conidia/cm², respectively. The mortality of adult beetles walking on sheets was 100% and 85% at densities of 10⁷ conidia/cm² and 10⁶ conidia/cm², respectively. Walking times of 5 or 60 seconds did not affect mortality. The adult longevities were longer after walking on sheets with 10⁶ conidia/cm² than on 10⁷ conidia/cm². Sheets containing the fungus were bound around the trunks of fig trees to control P. hilaris adults in early summer. The conidial concentration on the sheets was 10⁷ conidia/cm² for 20 days after attachment and approximately 80% of the adult beetles were infected and killed by the fungus. However, the conidial density decreased to 10⁶ conidia/cm² after 31 days and the adult beetle mortality fell to 60%.

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Ooencyrtus nezarae females emerging in the laboratory from three major host species were classified into two groups according to their fore-wing length. One group emerged from the eggs of Piezodorus hybneri and Riptortus clavatus, and the other from the eggs of Megacopta punctatissimum. From the discriminant function based on the results from laboratory-reared females, an attempt was made to infer the host species from which females collected in soybean fields had emerged. The validity was evaluated by comparing annual and seasonal changes in the estimated composition with the actual composition of wasps emerging in the fields.

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A bioassay method was established to identify the sex pheromone of the sugarcane shoot borer, Tetramoera schistaceana SNELLEN (Lepidoptera: Olethreutinae), an important sugarcane pest in Okinawa. The bioassay method was based on observation of the mating behavior of male moths in a small glass flight tunnel. Before the experiment, male moths were kept after emergence at 25°C under continuous light. Four hours before the bioassay, the light was switched off and the temperature was decreased to 20°C. Male moths could be used four times for this bioassay. These moths were kept at 25°C under continuous light for 2 days before the next bioassay.

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Many more adults of the West-Indian sweet potato weevil, Euscepes postfasciatus (FAIRMAIRE), were attracted by tubers and stems than by leaves of the sweet potato in a wind tunnel. Tubers damaged by larvae were much less attractive than undamaged tubers.

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The disruption effect of Z11-14: Ac on Pandemis heparana was evaluated in the laboratory. The mating percentage without the chemical was 85%. When 100ng of Z11-14: Ac was used as a disruptant, the mating percentage fell to 24%. Moreover, when 1, 000ng and 10, 000ng were used, the mating percentage was less than 5%. This result indicates that Z11-14: Ac causes mating disruption in P. heparana. This laboratory bioassay method was effective to estimate mating disruption effect.

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Seven primary parasitoids, three facultative secondary parasitoids, and seven secondary parasitoids were recorded from larvae and pupae of the diamondback moth Plutella xylostella in cabbage fields in Morioka, North Japan. Among the parasitoids, Cotesia plutellae, Diadegma niponica, Diadromus subtilicornis, and Oomyzus sokolowskii were dominant. O. sokolowskii was the parasitoid of C. plutellae, i.e. the secondary parasitoid of P. xylostella.

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