Microplitis manilae is new to Japan, and has been found to parasitize the larvae of Spodoptera litura in Okinawa Island, one of the southernmost islands of Japan. The parasitoids showed solitary endoparasitism and arrhenotokous parthenogenesis. They parasitized S. litura larvae from the first to antepenultimate instar, and greatly suppressed the feeding of host larvae, but they failed to parasitize penultimate and final instars, and eggs. Based on the developmental rates of M. manilae reared at constant temperatures between 15 and 30°C, developmental zero was calculated as 11.5°C and effective accumulative temperature from egg to adult emergence as 217.4 degree days. Oviposition and adult emergence of M. manilae were greatly suppressed when parasitoids were reared at a constant 15°C, while such suppression did not appear when they were reared at 15°C on average but at two different temperatures within a day. A female laid more than 300 eggs during 2 weeks of adult life at 20–30°C and survived for 60 days without egg laying at 15°C. The temperature dependency of development and fecundity in this species was compared with those of Meteorus pulchricornis, which is a well-known parasitoid of S. litura.

View full abstract

Five populations of mealybug, Planococcus kraunhiae (Kuwana), were collected from commercial persimmon orchards in Wakayama Prefecture: four populations including the Katsuragi population from four orchards with conventional insecticide spraying, and the Hashimoto population from an insecticide-free orchard. First instar nymphs were transferred onto a kidney bean leaf on 0.5% agar gel in a plastic Petri dish. A Petri dish which contained 20–40 nymphs was sprayed once with 6 ml of insecticide through a spraying tower on day 2 (1st instar), day 9 (2nd instar), day 16 (3rd instar) or day 25 (adult), and examined for susceptibility to insecticide. LC₅₀ of the 1st instar Hashimoto population and the resistance ratio at LC₅₀ of the other populations collected from conventional spraying orchards to that of the Hashimoto population were, respectively, 0.637 ppm and 8.0–12.2 for cypermethrin, 1.15 ppm and 6.0–7.8 for methidathion, and 0.029 and 15.4–20.2 for acetamiprid. Neonicotinoids were the most toxic to the Katsuragi population, followed by organophosphates, while the synthetic pyrethroids were less effective. The susceptibility to prothiofos and methidathion decreased as the growth stage advanced whereas susceptibility to acetamiprid remained high.

View full abstract

We evaluated entomopathogenic nematodes (Steinernematidae) as potential biocontrol agents to suppress the wild population of the sweet potato weevil, Cylas formicarius (Fabricius) as part of its eradication program. The pathogenicity of Steinernema carpocapsae (‘All’ strain), S. feltiae, S. riobrave and S. glaseri (‘326’, ‘328’, ‘Mungyeong’ and ‘Dongrae’ strains) was checked against the sweet potato weevil under laboratory conditions. S. carpocapsae induced the highest mortality in both sexes of the adult sweet potato weevil (90%<). About 30–60% of pupae and larvae in the root of sweet potatoes were killed by S. riobrave, S. glaseri (‘Mungyeong’ strain) and S. glaseri (‘Dongrae’ strain). The efficacy of S. carpocapsae (‘All’ strain) on the suppression of the weevil population was then tested in a sweet potato field. Application of S. carpocapsae (‘All’ strain) successfully reduced the root damage rate and root damage index by approximately 60% and 40%, respectively, as compared with root damage in the control fields. These results suggested that S. carpocapsae (‘All’ strain) would be an appropriate and effective biocontrol agent for suppressing the weevil population.

View full abstract

The age at which the rice leaf bug, Trigonotylus caelestialium, starts to copulate after adult emergence was determined by mating experiments. Females started to copulate 30 h after emergence and all females copulated after 102 h, when maintained under 16L:8D conditions at 25°C. After copulating once females were individually caged with a male 3, 24, 48 h after the initial copulation to determine if females copulate more than once. Multiple copulations were observed in 17 females among 22 females examined. To determine the effect of multiple mating on the reproductive performance of the bugs, fecundity, longevity and fertility of the eggs laid were investigated under different mating conditions. Newly emerged females were divided into three groups: virgin females, females constantly with a male and females with a male until the first oviposition was observed. There was no significant difference in the preoviposition period and total number of eggs laid between the three female groups. Although the longevity of virgin females was significantly longer than mated females, no significant difference in longevity was observed between the two groups of mated females. The fertility of eggs laid by females constantly with a male and females with a male until the first oviposition was 92.9% and 94.4%, respectively, and was not significantly different. These results suggest that mating(s) during the preoviposition period is sufficient for reproduction of the female rice leaf bug.

View full abstract

Non-target species trapped by synthetic pheromone-baited sticky traps for six lepidopterous pests on apple trees, Carposina sasakii, Adoxophyes orana fasciata, Archips breviplicanus, Archips fuscocupreanus, Grapholita molesta and Phyllonorycter ringoniella, were studied in central Hokkaido from 1984 to 1985 and in northern Hokkaido in 2004. In northern Hokkaido, surveys were conducted not only in a conventional pesticide-application orchard but in a communication disruption orchard. The following species were numerous comparatively; Meridarchis excisa in traps for C. sasakii, Archips audax and Neocalyptis angustilineata in traps for A. orana fasciata, A. audax, Homonopsis foederatana and Pandemis monticolana in traps for A. breviplicanus, and Cnephasia stephensiana stolidana in traps for G. molesta. Although the distinction of these non-target species from the target species was generally easy, it was difficult to distinguish Grapholita spp. (e.g. G. dimorpha, G. tenebrosana) from G. molesta in the same trap. It was considered that most of the non-target moths caught by traps had invaded from the orchard surroundings and trap specificity was influenced largely by the flora of the orchard periphery.

View full abstract

Eggs, larvae and pupae of Narathura bazalus (Hewitson) were reared at constant (17, 20, 23, 25 or 28°C) or fluctuating (14–20, 17–23, 20–26, 22–28 or 25–31°C) temperatures superimposed on a photoperiod of 12L : 12D (12 h light : 12 h dark) and 15L : 9D. When insects were reared under lower temperature conditions (mean temperature of 17, 20, 23 and 25°C under 12L : 12D, and 17°C under 15L : 9D), the developmental period (egg to adult emergence) was significantly shorter than that at constant temperatures corresponding to the mean of fluctuating temperatures. This mechanism permits rapid development completion even at low temperatures during autumn, helping to increase the number of adults in the overwintering stage in this species. Based on the developmental zero and the total effective temperature for development obtained in this study, the number of generations per year in N. bazalus in Tsukuba, central Japan, was estimated to be four on the assumption that oviposition by overwintered females takes place in early April.

View full abstract

The insecticide susceptibility of yellow tea thrips, Scirtothrips dorsalis and its natural enemy mite, Euseius sojaensis was evaluated at 25°C under 16L8D. Imidacloprid was highly effective against S. dorsalis second instar larvae. Permethrin was effective at 100–200 ppm and marginally effective at 25–50 ppm. Imidacloprid was not harmful to E. sojaensis female adults, while permethrin was seriously harmful. The effect of insecticide application on the population of S. dorsalis and E. sojaensis was investigated in a Delaware vineyard in Osaka Prefecture. With the application of imidacloprid, the density of S. dorsalis was effectively reduced, and E. sojaensis was found to survive on the grapes. In contrast, the density of S. dorsalis was slightly reduced, and E. sojaensis was not found on the grapes with the application of permethrin. Injury to fruit by S. dorsalis was significantly lower on grapes with imidacloprid application. The results suggest that imidacloprid did not seriously affect the population of E. sojaensis but shows good control against S. dorsalis on grapes.

View full abstract

The effects of several pesticides on the survival of spiderlings of Pardosa astrigera L. Koch, which is regarded as a promising natural enemy against the diamondback moth in cabbage fields, were examined using a spraying tower in the laboratory. Most organophosphates, pyrethroids and carbamates were determined to be highly toxic to the spiderlings, but 11 insecticides (Chlorfluazuron, Teflubenzuron, Lufenuron, Flufenoxuron, Chromafenozide, three BT-insecticides, Pyridalyl, Thiamethoxiam, Indoxacarb) were harmless or very weakly toxic. The use of insecticides that are less toxic to spiderlings should be recommended in IPM programs to control cabbage pests.

View full abstract