Applied Entomology and Zoology最新文献

The effects of oviposition season on embryonic development and hatching in Phraortes elongatus (Thunberg) (Phasmatodea: Phasmatidae) were studied. Nymphs collected from spring through early summer in Okayama, Japan, were reared under outdoor conditions or under constant conditions in the laboratory. After adult emergence, their eggs were used for experimentation. Eggs laid in early summer hatched in the spring of the following year, whereas those laid in autumn hatched in the spring of the second year after oviposition. Dissection revealed that eggs laid in early summer had completed their embryonic development before the first winter, while those laid in autumn were in the early embryonic development stage. Eggs that did not hatch during the first spring completed their embryonic development during autumn. These findings suggest that P. elongatus eggs enter diapause to pass the first winter in an early or late embryonic developmental stage depending on the timing of oviposition. If eggs pass the first winter in an early embryonic developmental stage, diapause is also induced before the second winter in a late embryonic stage. At a constant 25 °C, most eggs completed embryonic development 8 weeks after oviposition and entered diapause. This suggests that warm temperatures during early embryonic development avert the diapause of early-stage embryos. Thus, P. elongatus has a univoltine life cycle when eggs are laid early in the reproductive season, and semivoltine when laid late.

Sugar beet cyst nematode (SBCN) is a serious pest of beet and Brassicaceae crops and was first detected in Japan in 2017. Two varieties of SBCN-resistant radish (‘Kobuberi-daikon’ and ‘KGM1804’) were selected for trap cropping based on pot experiments. However, their effect on the SBCN population was not confirmed under field conditions. In this study, field experiments were conducted to investigate the efficacy of these radishes on the SBCN population along with chemical treatment (1,3-dichloropropene and dazomet) and fallowing. Trap cropping using ‘Kobuberi-daikon’ and ‘KGM1804’ reduced the population density of SBCN to the same level (55–60% reduction in unhatched eggs) and was superior to fallowing, whereas the anti-nematode effect of both nematicides were higher than that of trap cropping (1,3-dichloropropene: 82% and dazomet: 66%). Considering the other advantages of trap cropping such as lower cost, environmentally friendliness and mitigating soil erosion, trap cropping using radish varieties tested in this study is a useful option for nematode management.

Early detection of insect pest outbreaks is critical for effective pest control. However, this is challenging, especially for pest species such as the Japanese orange fly, Bactrocera tsuneonis (Miyake) (Diptera: Tephritidae), whose larvae grow inside fruits. B. tsuneonis is a univoltine citrus pest, with females laying their eggs directly into the fruits during summer, and larvae develop inside the fruits until pupation in early winter. To monitor B. tsuneonis outbreaks, we developed and validated methods for the detection of environmental DNA (eDNA) in immature fruits collected during summer using quantitative real-time PCR. eDNA samples were prepared from individual fruits with oviposition pinholes left by gravid females during ovipositor probing and oviposition. By immersing the fruits in distilled water for 1 h to extract eDNA, B. tsuneonis eDNA was detected in 20% of the fruits. In addition, B. tsuneonis eDNA was detected in a fruit without oviposition pinholes, albeit at a low rate, suggesting that residual eDNA on fruit surfaces during mating and searching for oviposition sites can be detected. While there remains a possibility of cross-contamination between infected and uninfected fruits due to the lack of negative controls during eDNA extraction, we conducted preliminary field examination in several orchards where B. tsuneonis was either visually observed or not. B. tsuneonis eDNA was detected even at a location where adults were not observed visually, but were captured using plastic-tub traps, indicating a low population density. Thus, our method has practical applicability in various areas, regardless of B. tsuneonis population density.

The ectoparasitoid Dastarcus longulus Sharp (Coleoptera:Bothrideridae) is considered a potent natural enemy of Monochamus alternatus Hope (Coleoptera:Cerambycidae) and other cerambycid beetles. Our previous study highlighted the effectiveness of using once-frozen Zophobas atratus (Coleoptera:Tenebrionidae) pupae as a substitute host for mass rearing of D. longulus, although problems such as low parasitic success rates and small offspring size persist. To address these problems, our study focused on determining the optimal inoculation density of D. longulus larvae for rearing on pupae of Z. atratus. When 5, 10, 20, and 30 D. longulus larvae were inoculated per host, the rate of successful parasitism and pupal body size decreased with higher larval densities. Furthermore, intraspecific competition did not affect the fresh weight of D. longulus pupae and the maximum pupal size was achieved when five larvae were used for inoculation. Based on these results, we conclude that inoculating a single Z. atratus pupa with approximately five D. longulus first instar larvae is the most suitable propagation method.

The combined use of entomopathogenic fungi and neonicotinoids was examined. A combination of six types of neonicotinoids, acetamiprid, imidacloprid, clothianidin, nitenpyram, dinotefuran, and thiacloprid, and two fungal species, Beauveria bassiana (Balsamo-Crivelli) Vuillemin (Hypocreales: Cordycipitaceae) and Metarhizium sp. (Hypocreales: Clavicipitaceae), were administered to adult red flour beetles, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). The mortality of test beetles caused by the combined treatment was compared to those caused solely by neonicotinoids or a solvent control. Significantly enhanced mortality was observed when B. bassiana was used in combination with imidacloprid, thiacloprid, or clothianidin. Combination index (CI) analyses revealed that the enhanced insecticidal effects were synergistic and stronger for imidacloprid and thiacloprid. The effect of neonicotinoids on the beetle’s humoral as well as cellular innate immune responses were investigated. The mRNA levels of the Toll pathway-dependent antimicrobial peptide (AMP) gene, cecropin3, due to exposure to B. bassiana were slightly suppressed by the concurrent application of imidacloprid and thiacloprid. Encapsulation responses with melanin deposition against abiotic material tended to be suppressed by neonicotinoid treatment. These results collectively suggest that the synergistic effects of certain neonicotinoids co-used with B. bassiana might be associated with adverse impact of the neonicotinoids on the beetle’s antifungal immune defense. In addition, RNA interference-mediated silencing of crucial genes for the normal Toll pathway signaling rendered the knockdown beetles more susceptible to B. bassiana infection.

Life history theory suggests that females should allocate greater resources to immune function than males to increase their lifetime fitness. Although higher immune responses in adult females compared to males have been reported across various insect species, sexual differences in immunity during juvenile stages have been less explored. We investigated sexual differences in haemocyte density and phenoloxidase (PO) activiy in two species of rhinoceros beetles, Trypoxylus dichotomus (Linnaeus) (Coleoptera: Scarabaeidae) and Oryctes rhinoceros (Linnaeus) (Coleoptera: Scarabaeidae), during their larval stages. We found that male T. dichotomus larvae consistently displayed lower haemocyte densities than females, and this sexual difference persisted until adulthood. The sexual difference in immunity across life stages may be associated with sex-specific resource allocation patterns throughout lifetime. However, the less sexually-dimorphic species, O. rhinoceros, did not exhibit sexual differences in haemocyte densities during immature stages. PO activities did not exhibit sexual differences in larvae of either species. Additionally, we observed an increase in haemocyte densities with larval developmental stages in both species. However, while T. dichotomus exhibited lower PO activities in later stages, PO activities in O. rhinoceros did not largely change throughout development. Path analysis revealed that the ontogenetic changes in constitutive immune parameters were primarily driven by direct effects of body size rather than age. The species- and parameter-specific ontogenetic trends in immunity could be associated with allocation to other life history traits or tradeoffs among immunity parameters.

A new pest of tomato, the South American tomato pinworm, Tuta absoluta (Meyrick, 1917) (Lepidoptera: Gelechiidae), was found in Kumamoto Prefecture, Japan in 2021. We examined the genetic variation in the DNA sequences of the mitochondrial cytochrome c oxidase subunit I (mtCOI) gene in 1039 individuals belonging to 39 countries including Japan. In the maximum likelihood phylogenetic tree and haplotype network, 19 haplotypes were detected in the world. Of those haplotypes, only one haplotype (Ta1) was detected from all 39 countries including neighboring countries and Japan. These results and some other information suggest that this species migrated from neighboring countries to Japan. Furthermore, we developed a Multiplex PCR using species-specific primers to discriminate T. absoluta from other gelechiid moth, Phthorimaea operculella (Zeller, 1873) (Lepidoptera: Gelechiidae). We could successfully identify the first instar larvae, fourth instar larvae, pupae, and adults of both species based on the differences in the length of amplicon bands. In addition, we were able to identify adults of both species collected from various prefectures. These results indicated that the Multiplex PCR developed in this study is useful to identify all developmental stages of both species collected in the fields.

Predacious insects have rarely been implemented for biological pest control in open-field cultivation in Japan, partly because they may be readily dispersed from crops. The Asian lady beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), is an indigenous natural enemy of aphids in Japan. In recent years, technology for establishing lady beetles on plants using an artificial diet has been advanced for greenhouse cultivation. In open-field cultivation, however, there are problems such as deterioration of food quality due to environmental conditions, and this technology has yet to be put to practical use. Flight-controlled adults of the lady beetle are commercially available as ‘Tentrol’ and are utilized for aphid control in Chiba Prefecture. In this study, the effects of a gummies-like diet developed for flight-controlled adults of the lady beetle were examined in laboratory and outdoor experiments. The laboratory findings showed that the gimmies-like diet is more persistent than two commercial diets as food for the beetle. In the outdoor experiment, the diet had a significant effect on retaining the beetles in stocks of eggplants. These results indicate that use of the diet together with flight-controlled lady beetles may be an effective aphid control method in open-field cultivation.

Three major sweet potato pest species, sweet potato weevil Cylas formicarius (Fabricius) (Coleoptera: Brentidae), West Indian sweet potato weevil Euscepes postfasciatus (Fairmaire) (Coleoptera: Curculionidae) and sweet potato vine borer, Omphisa anastomosalis (Guenée) (Lepidoptera: Crambidae), were examined for their utilization patterns and spatial distribution in the wild host plant, blue morning glory, Ipomoea indica ((Burm.) Merr.) (Solanales: Convolvulaceae) in Okinawa, Japan. We investigated 18,720 samples of I. indica and showed that 649 individuals of C. formicarius were found at an infestation rate per 1 m of the vine of 2.44%, which was significantly higher at height levels 0 m than the other levels (0–1 m, 1–2 m and 2–3 m), and tended to be higher at height level >3 m. In the case of E. postfasciatus, 131 individuals were found, and its infestation rate (0.37% on average) was significantly higher at height levels 0–1 m than the other level (2–3 m), and tended to be higher at height level >3 m. In the case of O. anastomosalis, 65 individuals were found and its infestation rate (0.32%) was significantly higher at the 0–3 m height level than at the other level (0 m). The results of analysis of the spatio-temporal dynamics of populations within and across species showed that the pests are randomly distributed across the study area throughout the year. Stochastic simulations showed that E. postfasciatus and the other two species tend to infest the same vines, but C. formicarius and O. anastomosalis tend to infest different vines. We provide valuable information on the distribution patterns of these pests that can their effectively control.

While the fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), has invaded Asia, whether it uses local weeds as alternative hosts remains understudied. This knowledge gap is significant as alternative hosts may facilitate fall armyworm expansion. Here we conducted three experiments to investigate the potential use of Asteraceae weeds (Emilia sonchifolia var. javanica [E. sonchifolia hereafter] and E. praetermissa) by fall armyworm in Taiwan: (1) The feeding experiment examined fall armyworm performance on the two Emilia species against the control (artificial diet). (2) The host-plant shift experiment tested if fall armyworm can survive on the Emilia species after depleting its primary host (maize). (3) Spatial analysis mapped current fall armyworm invasions, maize production areas, and the distribution of Emilia host plants (if confirmed) to demonstrate the potential of Asteraceae weeds as fall armyworm’s untapped resource. The results indicated that fall armyworm could complete its life cycle on E. sonchifolia but not E. praetermissa. Compared to the control, both sexes of fall armyworms on E. sonchifolia performed similarly in survivorship, larval weight, larval and pupal duration, but worse in pupal length and weight. In addition, larvae can switch to E. sonchifolia after depleting maize, reaching adult emergence and producing fertile eggs. The spatial analysis demonstrated hotspots of fall armyworm invasions and a large area of E. sonchifolia as potential food resource for future fall armyworm expansion. Overall, our results raise concerns that overlooking the use of weeds from the Asteraceae family may lead to an underestimation of future fall armyworm expansion.