Applied Entomology and Zoology最新文献

Gynnidomorpha gentianae Suzuki and Jinbo sp. nov. (Lepidoptera: Tortricidae: Tortricinae), whose larva causes damage to Gentiana scabra Bunge var. buergeri (Miq.) Maxim. ex Franch. et Sav., is described from Japan (Hokkaido and Honshu). In this paper, we provide diagnoses and descriptions for this species based on the Japanese specimens.

The diamondback moth Plutella xylostella (L.) (Lepidoptera: Plutellidae) is one of the most destructive insect pests worldwide which has developed resistance to many insecticides. Previously, a point mutation (I4790K) in a ryanodine receptor gene, a target gene of diamides, was identified as a major factor of resistance of the diamondback moth to cyantraniliprole in Japan. Although the diamondback moths have not yet widely developed resistance to cyantraniliprole in Japan, increasing resistant diamondback moth populations with the I4790K mutation in the future is a concern. To simply and quickly monitor the frequency of the I4790K mutations in field populations, we developed a multiplex polymerase chain reaction (PCR)-based molecular diagnostic method that can identify a genotype of the I4790K mutation site. We evaluated the sensitivity and specificity of the diagnostic method by comparing its cyantraniliprole-resistant and cyantraniliprole-susceptible allele detection results with those by Illumina MiSeq sequencing data. The results show sufficiently high sensitivity and specificity. Moreover, cyantraniliprole-resistant allele frequencies calculated by the molecular diagnostic method were almost comparable with those by MiSeq sequencing data. The molecular diagnostic method would help in performing continuous monitoring of the cyantraniliprole resistance level of diamondback moth populations in the field.

The chrysanthemum lace bug Corythucha marmorata (Uhler) (Hemiptera: Tingidae) is a North American insect that has become invasive in Japan. While it exclusively feeds on Asteraceae plants in its origin, it has been reported to attack sweet potato, blue daze, eggplant, and pepino in Japan. This study assessed the preferences of C. marmorata on sweet potato cultivars in a field and explored ovipositional responses in the laboratory, i.e., pre-oviposition periods, number of eggs, and egg sizes. A 2-year field survey demonstrated that Caroline Lea, Kyukei 17-3028, and Benisengan were the most preferred cultivars based on adults captured. In the laboratory, females laid a significantly larger number of eggs and had shorter pre-oviposition periods on sweet potato cultivars such as Benisengan and Caroline Lea. When categorized into early- and late-laid egg periods, it was found that females on less preferred cultivars (e.g., Beniazuma) produced significantly larger late-laid eggs compared to females on preferred goldenrod or Benisengan cultivars. It was suggested that sweet potato cultivars with inferior nutritive qualities may encourage C. marmorata females to better provide for their eggs. Thus, host plant quality affected C. marmorata female performance which may, in turn, affect progeny survival and viability.

Hemiptera are the second insect order with the highest proportion of exotic species in Europe. The main disease vectors in vineyards are introduced species of leafhoppers. The Asian two-spotted leafhopper has been recorded once on grapevines, but its relationship to this crop was unknown. More than 90 000 specimens were collected during a 9-year monitoring period with yellow-sticky traps on Madeira Island. This material and visual counts of nymphs on leaves confirm for the first time that grapevine is its host plant and that populations in vineyards are large throughout the grapevine growing season. Additional sampling to determine its current distribution range in Europe shows that it is spreading rapidly in the Macaronesian archipelagos and in the Iberian Peninsula, having already reached the French border. Twenty-four new food plants in Europe are reported with ornamentals being the most likely invasion pathway. Fieldwork observations from science platforms show that it breeds throughout the year between 10º and 38º latitude. These data, together with its good performance in wide environmental conditions and a history of previous successful invasions, strongly suggest that this species is a new threat to European vineyards. Control measures and more studies on plant damage and its potential for pathogen transmission are proposed.

Silkworms and other insects confer innate immunity by expressing antimicrobial peptides (AMPs) through the induction of Toll and IMD pathways. Cecropin B, an AMP from Bombyx mori L. (Lepidoptera: Bombycidae), has a broad range of antibacterial activity against both Gram-positive and -negative bacteria. Bacterial flacherie is one of the severe diseases in silkworms. In an attempt to develop silkworm strains expressing antibacterial properties, a transgenic vector, piggyBac overexpressing the cecropin B gene, was constructed under its promoter. The vector had GFP under the control of the elongation factor (ELFα) promoter as a marker for screening transgenic silkworms. Transgenic silkworms were generated by microinjecting the piggyBac vector along with the helper vector into the silkworm eggs. The mRNA level of cecropin B in the fat body of transgenic lines was higher than the non-transgenic lines in response to Escherichia coli and Staphylococcus aureus infections. The overexpression of cecropin B was confirmed by Western blot analysis. Transgenic lines' mortality was significantly decreased compared to non-transgenic lines’ post-bacterial infections. These results imply that overexpressing an endogenous AMP gene can enhance the resistance of silkworms in response to bacterial infections.

Aphelenchoides besseyi Christie (Nematoda: Aphelenchoididae) is a seed-borne ectoparasite of Oryza sativa rice and causes ‘white tip’ disease. When seeds are soaked in water, the nematodes emerge from them, arrive at rice plants by swimming in flooded paddy fields, and reproduce on them. Two separate experiments were conducted to determine the relationships of the nematode abundance in water to the arrival (infection) and subsequent multiplication of nematodes, the disease incidence, and the yield of rice grains. Experiment 1 showed that, as the A. besseyi population (Pi) surrounding the seedlings increased, both the disease incidence of plants and the number of nematodes (Pf) in all seeds harvested per plant increased, but the rate of increase in the nematode population (Pf/Pi) decreased. Negative relationships were found between the Pi level and the estimated probability of nematode arrival, although it was extremely difficult to isolate all arrivals from plants (experiments 2 − 5). However, the number of arrivals was estimated to increase with the Pi level. It is considered from these results that the density-dependent decrease in the rate of increase (Pf/Pi) was determined largely by the density-dependent reduction in the rates of nematode establishment (colonization) and/or post-establishment reproduction on plants.

Stenotus rubrovittatus (Matsumura) and Trigonotylus caelestialium (Kirkaldy) (Hemiptera: Miridae) are major rice pests in Japan. Since both species feed on rice grain through the gap between the lemma and palea, the paddy grains with gap (including split-hull) is vulnerable to them. The aim of this study was to develop a staining procedure to identify the vulnerable paddy with gap. The paddy samples were first stained under different conditions to select the optimal staining conditions that could highlight the gap and help sort the split-hull paddy clearly by visual inspection. After optimization experiments, 0.05% aqueous methylene blue solution was selected for staining, and 3 min was set as the staining and pretreatment times. The efficiency of this staining procedure was evaluated by applying it to the paddy harvested from fields to examine how well it could sort the vulnerable paddy. The stained paddy percentages were similar in the five replicates for the staining test, thereby confirming its reliability. The gap detection rate determined by the staining technique was approximately 30% higher than that determined by visual inspection. These results indicate that the staining technique enables the identification of vulnerable paddy, and may be useful for estimating vulnerable product and analyzing potential damage.

Bombyx mori densonucleosis (BmDV), infectious flacherie (BmIFV) and nuclear polyhedrosis (BmNPV) viruses inflict huge losses in sericulture. The study was envisaged to develop productive bivoltine silkworm hybrid, tolerant to these viruses, employing marker-assisted breeding. One hundred and twenty diverse bivoltine silkworm breeds, B. mori L. (Lepidoptera: Bombycidae) in India were screened against BmDV, BmIFV and BmNPV. Eight SSR markers were identified with distinct amplification profiles between virus-tolerant and susceptible populations. Two specific populations derived from the bivoltine silkworm breeds—HBM10 and PAM117—exhibited multi-viral tolerance (PAM117: 36–67%; HBM10: 24–65%) and these lines were designated as PAM117-MVT and HBM10-MVT. The resultant foundation cross (HBM10-MVT × PAM117-MVT) showed 37% enhanced survival (BmDV: 71–75%, BmIFV: 71–74% and BmNPV: 71–72%) over the parental stocks. A productive and multi-viral-tolerant bivoltine double hybrid (RDIN1) was developed by crossing with productive foundation cross (CSR52 × CSR27). The rearing and reeling performance of RDIN1 {(CSR52 × CSR27) × (HBM10-MVT × PAM117-MVT)} was on par with the popular bivoltine double hybrid {(CSR2 × CSR27) × (CSR6 × CSR26)} across the locations. The identified SSR markers could be utilized to develop robust and resilient silkworm hybrids for commercial exploitation.

The red imported fire ant Solenopsis invicta Buren (Hymenoptera: Formicidae) causes serious damage worldwide as an invasive alien species. The species has expanded its range to the Pacific Rim since 2000s and Japan has faced its multiple introductions since 2017. While colony-level control methods are urgently needed, testing living colonies of the unestablished species is challenging especially due to various restrictions under the COVID-19 pandemic. Here, we proposed alternative long-term toxicity assays using artificial colonies of Tetramorium tsushimae Emery (Hymenoptera: Formicidae), a Japanese native species belonging to the same subfamily (Myrmicinae) as S. invicta. We conducted an acute toxicity test to determine if T. tsushimae is a suitable substitute for S. invicta using fipronil and found the LD₅₀ value in T. tsushimae was close to that in S. invicta. Then, we conducted the long-term toxicity test with fipronil and two insect growth regulators (pyriproxyfen and etoxazole) using artificial colonies of T. tsushimae. All workers and larvae in the fipronil-treated colonies died within 3 days of treatment initiation. Emergence of new workers was observed after 18 days in the etoxazole-treated and control colonies, but not in the pyriproxyfen-treated colonies. We concluded that fipronil was the most promising insecticide for post-establishment control, and pyriproxyfen was effective as a toxic-bait agent for colony-level control.

Closely related species often exhibit similar niches and reproductive interactions. As competition for shared resources, reproductive interference, and hybridization may exclude one or the other species, the coexistence of closely related species is one of the main research topics in ecology and evolution. Drosophila biauraria and D. triauraria are closely related species with a broad sympatric distribution in Japan. To understand the mechanism underlying their coexistence, we investigated their habitat-use pattern, seasonal occurrence, and the frequency at which they were collected together in Sugadaira Montane (Nagano Prefecture), where grasslands, young forests, and mature forests are present. Slight differences in habitat-use pattern and seasonal occurrence were found between D. biauraria and D. triauraria. However, both species were sometimes collected together. Especially, D. triauraria females were collected together with heterospecific males, suggesting that D. triauraria females may be at risk of reproductive interference and hybridization. Female mate preference for conspecific males was expected to play an important role in reducing their reproductive interaction; however, abnormal genital structures in a few males found in this study suggest the possibility of their hybridization.