Japanese Journal of Applied Entomology and Zoology Vol. 61(2017) No. 2

Lepidopteran larvae damage to the branches of cultivated kiwifruit is a serious problem in the southwest part of Ehime Prefecture, Japan. We reared these larvae using seedlings of kiwifruit, and found that this species was a clearwing moth, Nokona feralis（Leech）. After emergence, the 1st instar larvae bored into the current shoots from the base of the petiole, and almost all of the leaves near the positions where the larvae bored were withered. Larvae moved to 30–40 mm diameter branches and bored into them, and expelled a large amount of frass from the site the larvae attacked. The puparia were observed mainly on 20–50 mm diameter branches. One to five eggs were laid, mainly on the petiole base. Ovipositions by females were observed until the middle of October. Eggs overwintered and then larvae hatched the next April. The hatching rate was 30.4% and 39.2% of eggs were attacked by a parasitoid wasp. Males were captured by pheromone traps from early September to the middle of October, and a peak of male capture was observed from late September to early October. Of 28 pheromone traps placed across Ehime Prefecture, only 4 traps in the southwest region（Ainan Town, Uwajima City, and Yawatahama City）captured males. To suppress larval attack, some insecticides were carried out in the season of larval hatch. Cypermethrin, methidathion（DMTP）, and cartap effectively prevented the larval attack to kiwifruit.

Although biological interactions have been studied intensively to account for population dynamics and community structure, little is known of the aquatic organisms that inhabit paddy fields, despite their high biodiversity. We conducted field research and an experiment to elucidate direct and indirect interactions among micro- and filamentous algae, their consumers（fingernail clams and water fleas consume the former and chironomids the latter）, and loaches that prey on water fleas and chironomids. The experiment examined the effects loaches and fingernail clams have on algae biomass. Fingernail clams reduced microalgae biomass by filter feeding, while loaches increased it by feeding on water fleas. Loach predation on water fleas increased the biomass of microalgae indirectly, which might have led to an increased density of fingernail clams. Filter feeding on microalgae by fingernail clams increased the density of filamentous algae, a potential competitor of microalgae, suggesting that fingernail clams increase the density of chironomids by enhancing their diet, which may then increase the density of the loaches that prey on chironomids. Field research revealed a positive spatial association between loaches and fingernail clams, attributable to their mutual food resource facilitation.

The skipper butterfly Parnara guttata guttata（Bremer et Grey）utilizes temperature as an important cue for producing the optimal reproductive allocation between size and number of eggs in each generation. Reciprocal transfers were made by switching the thermal conditions between a low temperature condition（20°C）, which induces smaller sized eggs, and a high temperature condition（25°C）, which induces larger sized eggs, to investigate the critical period for the regulation of egg size by P. g. guttata in response to temperature. Females laid larger eggs when a high temperature was present during all larval stages or when a low temperature was present only during the fifth（final）instar larval stage. In contrast, smaller eggs occurred in response to any other thermal condition. There was a high correlation between egg size and temperature during the total developmental period of the first and fourth instar larval stages. These results suggest that this species has a mechanism for monitoring thermal conditions twice, i.e., at the first and fourth instar larval stages. The adaptive significance of the response of egg size of P. g. guttata to thermal conditions experienced at the early and middle immature stages was discussed.

We investigated the efficacy of insecticides to control the tea leaf roller, Caloptilia theivora, which is a major pest of tea fields throughout Kagoshima Prefecture. Benzoylurea analog insect growth regulator insecticides（IGRs）exhibited low efficacy against the tea leaf roller in the Nansatsu region（Makurazaki City, Minamikyushu City）. In a subsequent investigation on the sensitivity of different tea leaf roller populations in different regions of Kagoshima Prefecture, the LC₅₀ for flufenoxuron in the Nansatsu population was found to range from 21.5 to 57.0 ppm（resistance ratio of 239- to 356-fold）, confirming the population’s reduced sensitivity. We speculate that this is due to the continuous use of this chemical to control a range of insects, including the tea leaf roller, for more than ten years. In addition, benzoylurea analog IGRs exhibited high efficacy in all other populations outside the Nansatsu region. Meanwhile, diacylhydrazine analog IGRs（methoxyfenozide）, neonicotinoid（dinotefuran）, and diamide（chlorantraniliprole）were confirmed to be effective against the tea leaf roller in all regions of the prefecture. In the future, it will be important to implement integrated pest management using insecticides with different modes of action depending on the region.

We investigated the inheritance of resistance to diamide insecticides, flubendiamide, and chlorantraniliprole in the smaller tea tortrix, Adoxophyes honmai Yasuda, using resistant（R）and susceptible（S）strains obtained from Shizuoka Prefecture, Japan. Lethal concentration 50（LC₅₀）values for flubendiamide in the R and S strains were 129 and 3.26 ppm, respectively. LC₅₀ values for chlorantraniliprole in the R and S strains were 48.2 and 1.33 ppm, respectively. The results of crossing experiments showed that resistance to the two diamides was an autosomal incompletely dominant trait controlled by polygenic factors.

We investigated the occurrence of phytoseiid mites, as indigenous natural enemies of Thrips tabaci Lindeman, in winter-harvested Welsh onion fields in Chiba Prefecture, Japan. Periodic surveys were carried out in five fields, and six species of phytoseiid mites were captured. We assumed the dominant species was Gynaeseius liturivorus（Ehara）, because we captured this species in 8 fields during temporary surveys of 17 fields. Gynaeseius liturivorus populations were higher during October to December in winter-harvested Welsh onion fields receiving lower applications of agrochemicals than conventionally controlled fields. Adult female densities were significantly higher on the insides of leaf folds than on other surface areas of the Welsh onions; all stages of G. liturivorus were frequently observed at peak abundance on the insides of the leaf folds. These results suggest that the insides of Welsh onion leaf folds provide a suitable habitat for G. liturivorus. We identified their predatory potential against T. tabaci in the laboratory（adult females consumed 1.1±0.4 adults or 5.3±1.9 2nd instar larvae per day at 22°C with a 12L:12D photoperiod）, and observed suppression of thrips in the fields at peak abundance of G. liturivorus. However, development of enhanced techniques for insectary plants and evaluation of agrochemical effects on G. liturivorus are needed in order to sustain higher mite densities, because the control of thrips by mites was not sustainable in this study.

The parasitoid Encarsia smithi comprises two phylogenetic groups. Type I is a strain that was introduced from China in 1925 to control the orange spiny whitefly, Aleurocanthus spiniferus, in Japanese citrus orchards. The other strain, type II, was accidentally introduced and has recently been found in tea fields infested with the tea spiny whitefly, A. camelliae. In this report, we describe our developed rearing method for successive generations of the two strains using A. spiniferus-infested citrus seedlings. In rearing experiments, we found these strains to have different ecological characteristics in terms of number of offspring and emergence pattern.

Nesidiocoris tenuis（Reuter）has good potential as a biological control agent for tomato. In this study, we evaluated the within-plant distribution of N. tenuis in greenhouse grown tomatoes under an increasing temperature condition. When the population density of Bemisia tabaci（Gennadius）was low, N. tenuis aggregated on the upper leaves. However, when the population density of B. tabaci was increased on the middle leaves, N. tenuis also increased on the middle leaves. These results suggest that N. tenuis are capable of aggregating in an area where B. tabaci are distributed and preying on them. However, we need to investigate not only the increasing temperature condition but also the decreasing temperature condition to prove N. tenuis changes its within-plant distribution depending on prey density.

To date, in Japan, several species of the genus Morophagoides Petersen are known to be pests of shiitake mushroom, Lentinula edodes（Berk.）Pegler. Due to close similarities in the wing markings of the species, it is sometimes difficult to distinguish each species based only on external appearance. In order to provide useful information for pest management strategies, taxonomic keys are given to distinguish the seven Japanese species of the genus mainly using wing maculation and male and female genitalia. Furthermore, the six species are also distinguished by standard DNA barcoding.