Applied Entomology and Zoology最新文献

The brown planthopper, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) and the green rice leafhopper, Nephotettix cincticeps Uhler (Hemiptera: Cicadellidae) feed by sucking phloem sap from rice plants and excreting honeydew containing glucose. It is known that there are resistant rice cultivars against Ni. lugens or Ne. cincticeps, from which insects are unable to suck phloem sap. Here, we developed a simple method using a glucometer to measure glucose concentration in honeydew and use it to evaluate rice resistance against sucking insects. In case of Ni. lugens, the honeydew excreted by sucking a susceptible rice line was large in volume and glucose content. In contrast, the honeydew excreted by sucking a resistant rice line was low in volume and glucose content. In case of Ne. cincticeps, no glucose was detected in the honeydew excreted by sucking a resistant rice line, although more honeydew was excreted from the resistant rice line than the susceptible rice line. Therefore, it was suggested that Ne. cincticeps could not suck phloem sap of the resistant cultivar. Glucose analysis of honeydew using a glucometer would be useful for evaluating sucking inhibition of rice cultivars against Ni. lugens and Ne. cincticeps.

Real-time quantitative polymerase chain reaction (qPCR) is used to estimate the population densities of the potato cyst nematodes Globodera pallida Stone and Globodera rostochiensis (Wollenweber) Skarbilovich (Tylenchida: Heteroderidae). Since it is difficult to extract nematode DNA from large amounts of soil (≥ 100 g, enough for quantification of cyst nematodes), cyst isolation is required before DNA extraction. However, when isolating cysts from the soil, various impurities are simultaneously isolated, and separating the cysts from these impurities is laborious. Although previous studies have reported methods for extracting DNA from mixtures of cysts and impurities, it is unclear whether such DNA can be used to estimate nematode densities using qPCR. To examine the effects of impurities on the accuracy of qPCR quantification, we extracted DNA from nematode eggs (G. pallida and G. rostochiensis) mixed with impurities and performed qPCR. The results suggested that the differences in the fields affected the quantification accuracy. Therefore, field-specific standard curves should be set, which are impractical for routine diagnosis. To propose a more practical method, we determined a fixed standard curve for each species and estimated the population densities in field soil samples by qPCR using the standard curves. The estimated population densities significantly correlated with those determined using conventional microscopic inspections. This study revealed that the population densities of G. pallida and G. rostochiensis can be estimated from large amounts of soil, probably only approximately, but efficiently, by qPCR using DNA extracted from mixtures of cysts and impurities.

The West Indian sweetpotato weevil, Euscepes postfasciatus, a serious pest of sweet potatoes, is being eradicated by sterile insect technique (SIT) in the south-western islands of Japan. Information on the diurnal movement of the target pests on host plants and where mating and egg-laying behavior occurs on the host is important for the application of SIT, which eradicates the target pest through mating of released sterile males and wild females. However, little such information is available on this species. In this study, male and female adults were released on host plants to examine the diurnal distribution on seedlings according to sex, as well as the sites where mounting behavior and egg laying occurs. The results showed that females left the host plant more frequently at night, whereas males were more likely to remain on the host plant at night. Both males and females stayed on the nodes of the host plant during the daytime. Mounting behavior also tended to occur more often at nodes. Furthermore, compared to unmated females, mated females stayed at the vertical top of the seedlings. However, it was found that eggs were often laid close to the roots rather than at the top of the vertical stems, even when the seedlings were placed upside down. The results of previous studies and this study will be discussed from the perspective of the application of SIT against E. postfasciatus.

Insects with positive phototaxis fly to artificial light sources at night, stay there for a certain amount of time, and then fly away. Although many studies have been conducted on the arrival time of flying insects at artificial light sources, little is known about the time at which they fly away (departure time), duration of stay, and staying time zone. This information is important to protect phototactic insects from the fatal attraction to light that is known as a serious ecological light pollution. In this study, we aimed to identify the duration of stay and staying time zone for various insect species by marking them with light traps. Among the 63 species belonging to 11 orders observed at the study site, cluster analysis focused on 27 species for which 5 or more data points were obtained, highlighting three predominant stay patterns. Type 1 species arrived approximately 1.3 h and flew away approximately 4.1 h after sunset and stayed for a short period of approximately 2.6 h. Type 2 species arrived at approximately 1.2 h and flew away for approximately 9.6 h, with an 8.4 h stay. Type 3 species arrived later than Types 1 and 2, were attracted for 5.4 h, and flew away approximately 13.5 h with an 8.2 h stay. These results suggest that conservation biological countermeasures against light-attracted flying insects need to consider the stay patterns of insects that remain under outdoor lighting.

Reemergence and sister broods (second broods) are commonly observed in bark beetles (Coleoptera: Curculionidae: Scolytinae), particularly in species with male-initiated polygyny and female-initiated monogyny. Polygraphus proximus Blandford, a male-initiated monogynous bark beetle, is a quarantine species in the EU, which has been introduced from east Asia into both Siberia and central European Russia, causing mortality of trees across large areas of Abies sibirica forests. To clear whether P. proximus females reemerge to lay additional broods (sister broods), we observed the reproduction of reemerged females under laboratory conditions. We prepared 25 females reproducing in galleries collected by peeling the infested logs and 25 females reemerged from such logs. These females were put into the tubes vertically attached onto the surfaces of logs. Consequently, approximately 40% of both the reproducing females in galleries and the reemerged females bored into the logs and established sister broods without repeated mating. Moreover, 21% of these reproducing females established sister broods again using the same procedures, suggesting that the females can establish sister broods more than once. Our results indicated that the fecundity of P. proximus is higher than previously assumed, suggesting that its population levels can rapidly increase in weakened or dead trees, ultimately leading to the ability to attack healthy trees during the epidemic phase.

Invasive longhorn beetles are serious pests of tree stands worldwide. The rusty-spotted longhorn beetle, Apriona swainsoni (Hope) (Coleoptera: Cerambycidae: Lamiinae), is native to continental Asia, where it is a significant pest of legume trees. Its invasion into non-native ranges and damage to the local legume tree, Maackia amurensis, were first reported from Fukushima Prefecture, Japan, in 2021. This study investigated the biology of A. swainsoni in relation to adult emergence in Japan. Preliminary observations confirmed that A. swainsoni larvae create planned emergence holes on the host surface in late May. By exploiting these planned emergence holes, the adult emergence period was investigated in a field promenade of M. amurensis during the summer of 2022 and 2023. The researchers plugged the holes and recorded plug removal, resulting in the observation of 60 and 227 putative emergence events in respective years, with the majority occurring in early to mid-July. Further, during the summer of 2022, a periodic field survey of adult emergence was conducted, obtaining eight adults. Furthermore, a supplementary survey using infested logs maintained in a field cage demonstrated that the emergence period does not differ between sexes and the male-to-female ratio is one:one. Our results suggest that control efforts to suppress A. swainsoni adults in the field, such as insecticide spraying, should be prioritized in the relatively short, peak emergence period. This work indicates that the plug survey is useful for detecting the emergence period.

Three Japanese conifer-infesting gall midges (Diptera: Cecidomyiidae), Aschistonyx eppoi Inouye on Juniperus chinensis var. globosa, Dasineura nipponica Inouye on Larix kaempferi, and Janetiella kimurai Inouye on Pinus parviflora are redescribed based on specimens kept in the collection of Naturalis Biodiversity Center, The Netherlands, in the collection of Kyushu University, Japan, and those newly obtained in 2021 and 2022 from their type localities in Japan. In the redescriptions, we refer mainly to morphological features not sufficiently given in the original descriptions. For A. eppoi, a genus Byakushincecis is created. We provide genetic data of the three species for future taxonomic and phylogenetic studies. In addition, we identified Byakushincecis eppoi infesting bonsai of Juniperus chinensis var. sargentii at a nursery garden in Saitama, Japan. These trees were intended for export to the EU.

To optimize operating conditions and the selection of pesticides suitable for spraying from UAVs, we evaluated the coverage of sprayed droplets in the range of 0.001–100% coverage by constructing an indoor spraying device. With the device, the coverage rate decreased with the horizontal distance from the nozzle, and the complementary log–log transformed value of the coverage was approximated by a quadratic function of the distance. The natural logarithm of the deposited pesticide amount could be linearly expressed by the complementary log–log transformed value of the coverage. Different probit regression equations were obtained between the coverage rate of sprayed droplets and egg mortality of Panonychus citri due to four acaricides: spiromesifen, etoxazole, milbemectin, and acynonapyr. From the probit regressions, conventional spraying achieved 90% egg mortality with 150 mg/L spiromesifen (19–23% coverage rate), 50 mg/L etoxazole (14%), 10 mg/L milbemectin (98%), and 67 mg/L acynonapyr (92%). Ultra-low-volume concentrate spraying for UAVs achieved the same with 15,000 mg/L spiromesifen (0.017%), 5000 mg/L etoxazole (1.116%), 1000 mg/L milbemectin (1.339%), and 6667 mg/L acynonapyr (8.868%).

The Mexican soybean weevil, Rhyssomatus nigerrimus Fahraeus (Coleoptera: Curculionidae), is a pest of soybeans. In this study we evaluate the volatiles of the soybean flower of the varieties FT-Cristalina-RCH and Flores as possible attractants for R. nigerrimus. Behavioral bioassays using an “Y” tube olfactometer and Electroantennography tests were performed to evaluate the responses of R. nigerrimus to the soybean flowers and their volatile extracts, in addition the volatiles were collected by dynamic aeration and identified using gas chromatography coupled with mass spectrometry (GC–MS). Bioassays showed that females and males were attracted by the flowers and volatile extracts of flowers of both varieties. However, females exhibited stronger antennal response than males to the volatile extracts of flowers of both varieties and their synthetic blends. The volatile extracts analysis showed the presence of 1-octen-3-one, 2-ethyl-1-hexanol, limonene, α-copaene, α-pinene, undecane, nonanal, octyl hexanoate, trans-α-bergamotene and calamanene. Quantitative differences in 1-octen-3-one, 2-ethyl-1-hexanol, α-pinene and limonene between the varieties were observed. In bioassays, males and females were attracted by α-copaene, 1-octen-3-ol α-pinene, and both synthetic blends. Females exhibited stronger antennal response than males to the synthetic compounds α-pinene, α-copaene, 1-octen-3-ol, nonanal and limonene.

Trunk injection with imidacloprid is used to reduce the infestation rate of trees by pests. However, further research is needed to determine the insecticide persistence in trees. Here, we present a case study in which we evaluated horse chestnut trees for imidacloprid residues and the invasive leaf miner Cameraria ohridella (Lepidoptera: Gracillariidae) infestation 14 years after a single injection (5 mL of pesticide per tree). We detected residues of imidacloprid (on average 0.648 μg/kg in leaves) and its metabolites: imidacloprid-guanidine in leaves and inflorescences and imidacloprid-urea in the leaves of treated trees. In addition, imidacloprid residues in inflorescences were at much lower concentrations (on average 0.07 μg/kg) compared to those found in leaves. Tree infestation by leaf miners was significantly lower in injected trees (0.035 mines/cm²) than in control trees (0.091 mines/cm²). Our research thus indicates for the first time that, once applied, imidacloprid may affect the target and non-target species for a long time owing to its persistence in plant tissues.