Applied Entomology and Zoology最新文献

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.

Population models provide a logical knowledge base before conducting laborious and expensive field experiments. Historically, two types of population models have been developed: highly realistic simulations and simple analytical models. Highly realistic simulations comprise a complicated systems model, whereas simple analytical models comprise various analytical models that focus only on the fundamental structure of the target pest population. Although both approaches have contributed to pest management science, each has limitations, poor predictability, and lacks substantial connections to reality. Assimilation by state-space modeling, in which observation and process models are jointly incorporated, is a good compromise between a simple model and reality in nature. In the big data era, artificial intelligence (AI), specifically aimed at high predictability, has recently become popular. If vital physical and biological records are automatically censored in the field with high precision, AI will produce the most plausible predictions, providing the best practical solution given our current knowledge. AI can be a powerful tool in the contemporary world; however, deductive modeling approaches are still important when considering the behavior of AIs and may also provide important insights to detect deficient information in the data.

Among the hemocytes of Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae), oenocytoids are lysed very quickly after hemolymph collection. We clarified that the lysis of oenocytoids can be greatly inhibited by collecting hemolymph under the introduction of carbon dioxide (CO₂) gas. Since nitrogen and helium gasses were ineffective in inhibiting oenocytoid lysis, it was concluded that CO₂ itself was necessary to inhibit lysis. Insect anesthetization with CO₂ gas before bleeding was not necessary to prevent oenocytoid lysis, but CO₂ gas was required at and after the time of bleeding. When the hemolymph was collected in a Petri dish under CO₂ gas and sealed, oenocytoids remained present without lysis even after an hour at 25 °C. Oenocytoids were not irreversibly fixed since lysis occurred when this hemolymph was exposed to air. When the hemolymph was collected in air, granulocytes adhered to the bottom surface of the Petri dish, and plasmatocytes spread out on the bottom surface. However, when collected under CO₂ gas, both types of hemocytes remained spherical, and few cells were observed to spread out on the bottom surface. Thus, it was suggested that oenocytoid lysis inhibition by CO₂ gas is associated with the suppression of defensive reactions to foreign materials by hemocytes. This hemolymph collection method can be easily performed without special pretreatment of the hemolymph. Accordingly, this method is considered to be advantageous for studying the possible role of oenocytoids associated with host defense mechanisms in insects.

Diapause is a programmed stage-specific arrest or delay in reproduction or development and is commonly used to circumvent an adverse season. Some insect species exhibit maternal regulation of diapause, wherein environmental cues are perceived by the mother and subsequently determine the developmental fate of the offspring. Although maternal regulation of diapause is widespread, its endocrinological mechanisms remain largely unknown. In the band-legged ground cricket Dianemobius nigrofasciatus (Orthoptera: Trigonidiidae), embryonic diapause is maternally determined. Adult females under long-day conditions lay eggs that develop into nymphs without interruption, whereas those under short-day conditions lay diapause-destined eggs that arrest their development and enter diapause at a very early embryonic stage, the cellular blastoderm. How development is arrested at an early stage is a key area of interest. We hypothesized that juvenile hormone III (JH III) and 20-hydroxyecdysone (20E), the major insect hormones that regulate a wide variety of physiological processes, are involved not only in maternal decisions, but also in diapause entry in D. nigrofasciatus. The results showed that the hemolymph concentrations of JH III and 20E in adult females were lower under short-day conditions; however, the application of JH III and 20E to the mothers did not affect the diapause incidence of offspring. No differences were observed in the amounts of 20E between non-diapause and diapause-destined eggs, and JH III was not detected in these eggs. Thus, we found no evidence for the involvement of JH III and 20E in maternal decisions for embryonic diapause and diapause entry in D. nigrofasciatus.

Two stone leek leafminer Liriomyza chinensis (Kato) (Diptera: Agromyzidae) biotypes (A and B) were reared using the Japanese bunching onion Allium fistulosum L. cultivar, ‘Kujou futo’ and subjected to competition under laboratory conditions. Both biotypes were reared in single and mixed cultures in varying proportions. The present study aimed to determine the reproductive behavior of the two L. chinensis biotypes under laboratory conditions of 24.5 °C and a photoperiod of 15 h light: 9 h darkness. Therefore, 12 adult flies, consisting of 3 males and females from each biotype, were reared in mixed cultures. The results indicated that biotype B had a significantly higher number of eggs and more emerged adults in the next generation than those of biotype A. The proportion of F₁ adults was 1.6%. In the second experiment, six males and females from the different biotypes were subjected to inter-biotype mating for 2 days without oviposition substrates. Subsequently, a mature female from each biotype was allowed to lay eggs on A. fistulosum fresh leaves. The results revealed that no larvae hatched from the eggs of both biotypes. The number of eggs per plant from both biotypes was standardized to determine larval competition. The number of eggs and egg survival rates of biotype B were higher than those of biotype A, indicating that under 24.5 °C and 15 h light: 9 h darkness conditions, biotype B outcompetes biotype A.

The broad mite, Polyphagotarsonemus latus (Banks) (Acari: Tarsonemidae), has been a devastating pest of several important agricultural and horticultural crops. Studies on the molecular mechanisms of adaptation to extrinsic conditions, e.g. acaricide exposure and temperature stress could aid in revealing the mite’s xenobiotic metabolism and quick adaptation to rapidly changing environments, respectively. This is best studied by the gene expression patterns, which could be accomplished through real-time quantitative reverse transcription PCR (qRT-PCR). Since real-time qRT-PCR studies require the selection of one or more reference genes whose expression patterns might vary across treatments, it is indispensable to validate their expression stability. In this study, the expression stability of six candidate reference genes viz., actin, elongation factor (EF-1α), glyceraldehyde-3-phosphate-dehydrogenase (GAPDH), ribosomal protein 49 (RP49), ribosomal protein S18 (RPS18) and β-tubulin (TUB) was investigated through real-time qRT-PCR experiments. By integrating the results of geNorm, NormFinder, BestKeeper, comparative ΔCt and RefFinder algorithms, RPS18/RP49 and EF-1α/RPS18 were identified as highly suitable reference genes for acaricide treatment and temperature stress treatments, respectively. RPS18 was recognized as the most suitable reference gene for both treatments which will ensure the accuracy of target gene expressions in studies related to xenobiotic metabolism and stress tolerance in P. latus.