The efficacy of insecticide-incorporated nets(permethrin-incorporated nets and etofenprox-incorporated nets)against the red-necked longhorn beetle, Aromia bungii(Faldermann)(Coleoptera: Cerambycidae), was evaluated. Choice tests and forced contact trials were conducted to assess adult settlement inhibition, oviposition deterrence, larval boring inhibition, and adult mortality rates. After installation, permethrin-incorporated nets showed 97.7% settlement inhibition and 92.4% oviposition deterrence, demonstrating significantly superior performance to the control nets. Etofenprox-incorporated nets achieved 91.3% settlement inhibition and 84.9% oviposition deterrence efficacy, with oviposition deterrence being significantly higher than the control nets and complete inhibition of larval boring. After three months of weathering, permethrin-incorporated nets maintained 90.0% oviposition deterrence, remaining significantly superior to the control nets. Conversely, etofenprox-incorporated nets showed reduced oviposition deterrence (48.9%), performing inferiorly to the control nets. In forced contact trials, permethrin-incorporated nets exhibited high adult mortality rates both initially after installation and after three months, whereas etofenprox-incorporated nets showed diminished effectiveness after three months. Overall, these results demonstrate that insecticide-incorporated nets constitute an effective control material that combines the advantages of both physical and chemical control methods, with permethrin-incorporated nets in particular providing long-term residual effectiveness.
The red-necked longhorn beetle, Aromia bungii(Faldermann)(Coleoptera: Cerambycidae), is an invasive species with a high reproductive capacity that causes severe damage to Prunus trees(Rosaceae ). In this study, we developed an oviposition substrate combining a black net with 0.4-mm mesh and filter paper, enabling efficient egg collection by utilizing the scent of peach branches. The peach branch scent increased egg production by approximately 3.4 times compared with that in the untreated controls. Using eggs collected with this method, we evaluated the ovicidal effects of various insecticides. Malathion/MEP emulsion and cartap hydrochloride showed 100% ovicidal efficacy, while diazinon wettable powder demonstrated a high efficacy of 70.7%. When assessing differences in effectiveness across the egg developmental stages, diazinon wettable powder showed consistent efficacy, maintaining high overall control effectiveness in the late developmental stages by exhibiting an insecticidal effect on hatched larvae, despite reduced direct egg mortality. Cartap hydrochloride exhibited high efficacy against the early to middle developmental stages. Additionally, Beauveria bassiana Vuillemin(Hypocreales: Cordycipitaceae)wettable powder demonstrated high efficacy against hatched larvae. These findings contribute to the development of efficient pest control strategies.
Laboratory experiments were conducted to assess the potential of Dastarcus longulus(Coleoptera: Bothrideridae), a coleopterous parasitoid of cerambycid beetles, as a biocontrol agent of Aromia bungii(Coleoptera: Cerambycidae). When first-instar parasitoid larvae were released onto A. bungii larvae and pupae in plastic containers, parasitism rates generally exceeded 80%. When parasitoid eggs were released onto wood infested with A. bungii, parasitism rates on larvae, pupae, and adults ranged from 57.1% to 70.6%. A parasitism rate of 66.7% was observed when eggs were released onto wood inoculated with host larvae. These findings indicate the ability of D. longulus as a biological control agent against A. bungii. The lower parasitism rates observed in infested wood compared with plastic containers are likely due to differences in host larval mobility and the behavioral traits of first-instar D. longulus larvae. In inoculated wood, the decay of host larvae beneath the bark resulted in few incidences of D. longulus adult emergence. Therefore, in field releases of D. longulus, which exhibits low host specificity, when the target is A. bungii larvae under bark, the likelihood of next-generation adults emerging and affecting non-target species is expected to be low.
The rusty-spotted longhorn beetle, Apriona swainsoni (Hope)(Coleoptera: Cerambycidae), is an invasive longhorn beetle species first detected in Japan in 2021. It infests the legume tree, Maackia amurensis, and other host trees, causing a severe decline in tree vigor and even tree collapse. Due to its ecological impact, the species has been designated as a "Designated Invasive Alien Species" under the Invasive Alien Species Act, and urgent control measures are required. However, no effective chemical control method has been established to date. In this study, we evaluated the larvicidal efficacy of trunk-injection using a dinotefuran 8% solution at a plantation site in Koriyama City, Fukushima Prefecture. Twenty infested M. amurensis trees were selected, with ten assigned to a treatment group and ten to a control group. The number of frass-extrusion sites was recorded before treatment and again eight months later. In the control group, an average of 53.9% of frass-extrusion holes ceased activity by the following spring. In contrast, the treatment group showed an average cessation rate of 86.5%, indicating a significant insecticidal effect of dinotefuran. Further investigation is needed to assess its efficacy against adult beetles and the duration of residual activity, toward establishing an integrated management strategy.
The sugar beet cyst nematode(SBCN), Heterodera schachtii Schmidt(Rhabditida: Hoplolaimidae), was first detected in Japan in 2017 and has since been officially controlled using chemical nematicides. Resistant cultivars and cultural practices against SBCN have been investigated, and two radish cultivars have been selected as a trap crop available in Japan. However, there is limited information on the ecology of the SBCN population in Japan. Among its various ecological traits, hatching is particularly important because of its direct impact on the effectiveness of cultural control measures and the survival period of the nematode. In this study, we conducted long-term hatching tests using field-collected SBCN cysts to explore the hatching dynamics of the nematode. Hatching of SBCN second-stage juveniles(J2 )con-tinued for 28 weeks, with approximately 85% of J2 emerging within 8 weeks. Our results indicate that the hatching of SBCN under field conditions can continue for a long time.
To clarify the effect of ambient temperature on the abundance of the two pecky rice bug species Niphe elongata and Cletus punctiger in organic rice paddy fields, we studied the relationships between the abundance of these species and temperatures recorded from November to April in Yamaguchi Prefecture, Japan, in 2022 and 2023. The periods during which temperature affected the abundance of both species were determined. Our analyses revealed that the abundance of N. elongata was significantly and positively related to the average minimum temperature in mid-April, suggesting that the low temperatures after the diapause termination may be associated with N. elongata mortality. The abundance of C. punctiger was significantly and positively related to the average maximum temperature in mid-March, suggesting that the higher temperature soon after the diapause termination makes it possible for overwintered C. punctiger adults to feed on host plants from earlier in the season. The heading period of rice was also observed to affect both species' abundance in paddy fields. These results may allow us to estimate the abundance of both species based on the temperature before the start of rice cultivation and the rice heading period.
Paddy grains with a slight gap between the lemma and palea are vulnerable to rice leaf bugs, Stenotus rubrovittatus(Matsumura)and Trigonotylus caelestialium(Kirkaldy)(Hemiptera: Miridae). This study aimed to determine the vulnerable paddy rate that can reduce pecky rice damage. Field data were collected from 2021 to 2023 in Joetsu City, Japan. Logistic models were constructed using data from 76 fields to estimate the probability of damage incidence; a relatively good model was selected. The selected model was used to assess the probability of >0.7% damaged grain incidence with two explanatory variables: percentage of vulnerable paddies and total number of rice leaf bug adults and larvae collected by sweeping at the full-heading stage. Using data from 113 fields, the selected model was evaluated and was reproducible for the <10% and 10-50% grades but not for the 50-90% and >90% grades. The model indicated that low vulnerable paddy incidence(<13.3%)reduces the probability to <10% damage incidence under low bug density conditions(<= 3.4 rice leaf bugs/20 sweepings). Although moderately effective(reducing damage to <= 0.7%), the low incidence of vulnerable paddy may help control damage, especially in late-heading rice fields.
This study investigated flight activity to develop forecasting methods for adult Eysarcoris aeneus(Scopoli) entry into rice fields. We examined the effects of temperature(30 degrees C and 25 degrees C)and food on flight muscle development and flight activity. Flight muscle weights were significantly higher at 25 degrees C than at 30 degrees C. At both temperatures, most males maintained their flight muscles as they aged. Female flight muscle weights decreased at both temperatures due to histolysis, with a more rapid reduction at 30 degrees C than at 25 degrees C in younger females. Oviposition rates showed no significant differences between the two temperatures. The rapid histolysis of female flight muscles at 30 degrees C likely reflects higher maintenance costs at this temperature than at 25 degrees C, thereby influencing the duration of female flight activity. Additionally, given the developmental transition of the flight muscles, flight activity may differ between male and female E. aeneus. Under feeding conditions, the number of flying individuals within 30 days after eclosion was higher at 30 degrees C(16 individuals)than at 25 degrees C(5 individuals)and higher in females(20 individuals)than in males(1 individual). Females began flying an average of 5.7 days after eclosion at 30 degrees C, compared with 11.8 days at 25 degrees C. These findings demonstrate that temperature influences the number of flying individuals and the duration of flight activity in E. aeneus, especially in adult females. Food availability was essential for flight muscle development in adults after eclosion. Under 25 degrees C conditions, removing food significantly increased the number of flying individuals compared with feeding conditions, with no significant differences observed between males and females. This indicates that unfavorable feeding conditions enhance E. aeneus activity. In conclusion, temperature and food interact to influence the flight activity of E. aeneus, affecting the timing and number of adults entering rice fields.
Stem borers are important insect pests that cause serious damage to trees by their larvae boring into the interior of trees. Although chemical control using aerosol spray insecticides is recommended for stem-boring insect pests, the chemicals often do not reach the larvae hidden in complicated pores, thereby reducing their extermination effectiveness. Because the pores are semi-closed spaces, volatile insecticides are expected to reach the larvae hidden deep within the complex pores. Therefore, we conducted a model test to demonstrate the effectiveness of extermination of the stem boring moth larvae, Endoclita excrescens (Butler)(Lepidoptera: Hepialidae), hiding deeply in the holes where the insecticide spray cannot be directly reached using AITC containing agents, which have insecticidal effects and high volatility, and the non volatile insecticide containing clothianidin and fenpropathrin. The results showed that the AITC preparation had a significantly higher extermination effect on moth larvae than the non-volatile insecticidal preparation or the control(no insecticide preparation). This suggested that volatile insecticides could effectively exterminate borer insect pests in areas that cannot be reached by chemical solutions.
Alternative control measures such as spiracle blockers can reduce the frequency of pest population exposure to pesticides and delay resistance development; however, population decline may in itself cause resistance allele fixation through genetic drift. We conducted a release experiment with two-spotted spider mites, Tetranychus urticae Koch, in strawberry fields in Shizuoka and Nara prefectures to examine the influence of spiracle blockers (sorbitan fatty acid esters) on the frequency of the etoxazole resistance allele (CHS1; I1017F). F2 adult females from resistant and susceptible strains crossed at a 1 : 9 ratio were introduced, followed by two consecutive control rounds using ther a spiracle blocker or etoxazole at their registered concentrations. Resistance allele frequencies were measured quantitative PCR. The resistance allele frequency increased in Shizuoka only after using etoxazole but increased to proximately 80% in Nara after the first round regardless of the control measure used. The population density dropped to one mite per compound leaf after the first round, suggesting a genetic bottleneck. The estimated initial allele frequency in the F2 population was 6%, and etoxazole was effective only once, highlighting the need for risk avoidance (e.g., switching to other control measures) when resistance alleles are still rare.
In recent years, widespread damage caused by biotype B of the stone leek leafminer, Liriomyza chinensis(Kato)(Diptera: Agromyzidae), has become an issue in Welsh onion fields throughout Ibaraki Prefecture. This study aims to evaluate the efficacy of granular insecticides in controlling L. chinensis in Welsh onion fields harvested in early autumn. Specifically, we applied either cyantraniliprole-thiamethoxam granules(6 kg/10 a)or dinotefuran granules(9 kg/10 a)to the base of the plants in late August, and compared their effectiveness to a non-granule control. Although all treatments showed an increase in the number of flies from mid to late September, the percentage of damaged leaves in the groups treated with granules was lower than that in the non-granule control. Furthermore, the effectiveness of dinotefuran was equal to or greater than that of cyantraniliprole-thiamethoxam. These results suggest that dinotefuran is a lower-cost alternative with saved times of usage of insecticide components, in late August on Welsh onions harvested in autumn.
A camera-trapping system developed for photographing perching Sympetrum dragonflies using passive photosensors is expected to support the biodiversity monitoring and evaluation of rice paddy fields. However, considerable time and labor was required in order to visually check the massive number of captured photographs to determine whether the dragonflies were correctly captured in them. In this study, automatic image classification using a deep-learning artificial-intelligence (AI)model was applied to the photographs captured by camera traps set in rice paddy fields in eastern Fukushima prefecture. The results show that the AI model can accurately detect and classify photographs containing a Sympetrum dragonfly, and that the estimated detection frequency based on the AI image classification is associated with the relative density of Sympetrum dragonflies directly observed in the fields. This suggests that automation by combining camera trapping and AI image classification is promising for monitoring Sympetrum dragonflies in the study area.
In August 2023, a male adult tick Dermacentor sp.(Acari: Ixodidae), suspected to be Dermacentor bellulus(Schulze), was collected from a brown bear( Ursus arctos yesoensis(Lydekker) (Carnivora: Ursidae))in Hokkaido, northern Japan. Previous reports from Japan indicate that the northern distribution limit of D. bellulus is Yamagata Prefecture. Thus, this report is possibly an update on the northern distribution limit of D. bellulus.
Ground beetles(Carabidae)have been utilized as bioindicators of environmental changes. In Japan, Synuchus nitidus(Motschulsky )(Coleoptera: Carabidae)is abundant throughout the country, except for the southern islands, northernmost areas, and high-altitude areas. The objective of this study was to assess their potential as an indicator species of global warming by analyzing data on their ecological traits, including flight capability, reproductive strategy, and feeding behavior. The observed low hindwing-to-body-length ratio and absence of flight muscles suggested that they are non-flying and depend on walking for movement and dispersal. This trait is advantageous for precisely monitoring the gradual shifts in latitude and elevation of their distribution resulting from global warming. Dissection findings revealed simultaneous egg development, indicating that variations in egg production can be assessed by examining ovarian eggs. A decrease in egg numbers at the same sites may be attributed to heat stress induced by global warming. Analysis of gut contents through dissection confirmed their carnivorous predatory nature, indicating that they occupy a high trophic level and that changes in their population have a high impact on the ecosystem. These findings support the suitability of this species as an indicator of global warming.
The West Indian sweetpotato weevil( Euscepes postfasciatus (Fairmaire)(Coleoptera: Curculionidae))is a serious pest of sweet potatoes in some countries. To increase the male mating ability of the weevils produced by a mass-rearing facility using the sterile insect technique(SIT ), we examined the effect of the amount of sugar contained in an artificial diet for adults on the mating performance of males and fecundity of females of E. postfasciatus. There was a positive correlation between the amount of sugar in the diet and the mating ability of virgin males;however, under afree-mating condition, the sugar content had a negative effect on the male mating ability. Our results showed that the sugar content in an artificial diet for adults can alter the mating and reproductive performance in the West Indian sweetpotato weevil.
