Applied Entomology and Zoology最新文献

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.

Although classical biological controls aim to permanently minimize numbers of invasive pests using exotic natural enemies, few long-term studies have been conducted on this subject. In this study, we investigated the population dynamics of the chestnut gall wasp Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae), and an introduced parasitoid, Torymus sinensis Kamijo (Hymenoptera: Torymidae), over 40 years (1982–2023) at a site at which the parasitoid was first released (Tsukuba City, Ibaraki Prefecture) in Japan. Because the gall formation rate per 100 chestnut buds, an indicator of pest density, had decreased from 42.5 to 0.7% in the first 10 years after the release, the biocontrol program was deemed successful. However, further research showed fluctuations in the pest density over the next 30 years. It usually remained at low levels but occasionally increased dramatically, with three peaks exceeding the economic injury level (30%). Simultaneously, an indicator of parasitoid density (the number of parasitoids emerging from 100 galls × the gall formation rate) also fluctuated, in synchronization with the pest density indicator. These results suggest that T. sinensis has played an important role in suppressing D. kuriphilus at the releasing site over 40 years.

Hydrogel baits are composed of an insecticide and sugar water solution that is sustained by a super-absorbent polymer. This novel bait formulation has been increasingly used for controlling invasive ant species, as they prefer liquid foods and bait stations, which can be both costly and wasteful, are not required. Despite usage trends, the preference of invasive ants for hydrogel baits when compared with other food sources has not yet been widely demonstrated. This study evaluated the recruitment of the invasive Argentine ant Linepithema humile (Mayr) to various food sources, including hydrogel bait formulations containing sugar and insecticides (thiamethoxam, clothianidin), sugar water, tap water, a commercial paste-type fipronil bait, and a shrimp-flavored snack. The hydrogel baits and sugar water had equal recruitment levels for L. humile, irrespective of the sugar and insecticide concentrations (average 100–500 ants to approximately 4 × 4 cm placement). The recruitment levels for the hydrogel baits were also equal to or greater than those for the commercial paste bait (50–150 ants). However, overall, the shrimp-flavored snack was the food source with the highest levels of recruitment (500–800 ants). The results suggest that in the field, L. humile is moderately to highly interested in hydrogel baits. Hydrogel baits may not be the most efficient bait formulation for recruiting L. humile, but they are a powerful control option due to their advantages such as low cost, which enables thorough treatment. The addition of attractants could help to improve this method in the future.

The brown marmorated stink bug Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) is an agricultural pest with a unique odor, aggregating near human habitats during the cold season. In the present study, we evaluated the suitability of H. halys as an edible insect. We observed that the one-time administration of 2000 mg/kg raw stink bugs to female rats via oral gavage did not affect their weight or cause mortality, suggesting that the medium lethal dose of H. halys adults was > 2000 mg/kg for female rats. Moreover, the presence of microorganisms or heavy metals was not observed in heated and raw insects, respectively, except for cadmium, suggesting that they met food hygiene and safety standards. Nutrient composition analysis revealed that the levels of useful compounds in H. halys were comparable to those in general hemipterans. The ratio of polyunsaturated fatty acids in H. halys adults was 44.3%, whereas that of saturated fatty acids was 16.8%. Moreover, H. halys was rich in β-carotene, astaxanthin, lutein, and zeaxanthin. Therefore, H. halys is a potential edible carotenoid source. Consumption of this insect would become a solution to managing the pest and nuisance. Further studies are needed to ensure food safety and human consumption.

Trunk injection is a relatively new, environmentally friendly method to apply insecticides to trees which does not cause insecticide drift and environmental runoff. However, little is known about the effect of insecticide trunk injection on non-target arboreal ants (Hymenoptera: Formicidae) which can act as biological control agents of target tree pests. This study evaluated the effect of trunk injections on arboreal ants found on cherry trees treated with neonicotinoids (dinotefuran and thiamethoxam) for controlling the invasive longhorn beetle Aromia bungii (Faldermann) (Coleoptera: Cerambycidae). Arboreal ants represented by Crematogaster matsumurai Forel can prey on A. bungii eggs. Results of visual sampling 1 and 3 months after injections showed that injections did not reduce the number of ant species occurring on tree trunks. Additionally, injections did not eliminate 3 of 4 most abundant species on tree trunks or extrafloral nectaries including C. matsumurai. However, a decline of Lasius japonicus Santschi was observed on injected trees. Our preliminary short-term survey suggests the possibility that chemical control by trunk injection and biological control by arboreal ants are compatible in A. bungii management. However, further research is needed to clarify the mechanism of L. japonicus decline and long-term consequences of trunk injection on arboreal ant composition.

Originally endemic to Asia, Drosophila suzukii (Matsumura, 1931) is a serious agricultural pest that is spreading rapidly throughout the world. To suppress the growing D. suzukii populations, several pest management programs have been implemented. Researchers have searched for natural enemies, such as predators, parasites, parasitoids, and pathogens. We discovered an obligate ectobiont fungus, Stigmatomyces majewskii H. L. Dainat, Manier & Balazuc, 1974, which is associated with D. suzukii. Our laboratory experiments revealed that S. majewskii infection was successfully transmitted through self-grooming and sexual contact during the courtship behavior of D. suzukii, although non-sexual contact through other behaviors may also be involved. Infected flies lived long enough for S. majewskii to mature on the host. Other fitness traits, such as fecundity, are necessary to evaluate the effect of S. majewskii on D. suzukii.

The gut bacteria of insects are associated with digestion, nutrition, and reproduction. The midgut bacteria of Anopheles mosquitoes have been examined predominantly for their effects on the transmission of Plasmodium parasites. However, the effects of midgut bacteria on Anopheles mosquitoes have not been studied. In this study, we investigated the effects of midgut bacteria on adult female An. stephensi mosquitoes. These mosquitoes were fed antibiotics mixed with 10% sucrose for 2 weeks to alter the composition of their midgut bacteria. The results showed that the mosquitoes fed with streptomycin (ST) or kanamycin (KM) showed inhibited egg maturation 2 days after blood feeding. Methylobacterium sp. was the predominant bacterium in the midgut of mosquitoes fed KM or ST for 2 weeks (ST/2 weeks). Mosquitoes that were fed suspensions of Methylobacterium sp. isolated from the midgut of ST/2 weeks after blood feeding for 3 days showed inhibited egg maturation. Furthermore, egg maturation was inhibited in mosquitoes that were fed supernatant and precipitate obtained by boiling and centrifuging Methylobacterium sp. suspension. Thus, this study demonstrated that Methylobacterium sp. isolated from the midgut of An. stephensi mosquitoes after blood feeding inhibited egg maturation.