Search Results (28)

A possible tactic to survey and control Pine Wilt Disease is the use of semiochemical-baited traps to capture the insect-vector, the pine sawyer Monochamus galloprovincialis (Olivier) (Coleoptera: Cerambycidae). The most common chemical lure used is the Galloprotect Pack, which includes the aggregation pheromone ([2-undecyloxy] ethanol), a host monoterpene (α-pinene), and bark-beetle pheromones (ipsenol and 2-methyl-3-buten-1-ol). This lure also attracts non-target species, including bark beetles (Coleoptera: Curculionidae: Scolytinae) that use ipsenol (Ips sexdentatus (Boerner)) and 2-methyl-3-buten-1-ol (Orthotomicus erosus (Wollaston)) as pheromones, but also large numbers of their natural enemies, Temnoscheila caerulea (Olivier) (Coleoptera: Trogossitidae), Aulonium ruficorne (Olivier) (Coleoptera: Colydiidae), and Thanasimus formicarius (L.) (Coleoptera: Cleridae), and other saproxylic insects (Coleoptera: Cerambycidae). These catches cause a decrease in biodiversity of the forest insect communities, and the removal of predatory insects may favour bark beetle outbreaks. Thus, our project objective was to test trap modifications to try to reduce catches of non-target insects. Modifying the multifunnel trap’s collection cup by placing a 0.5 cm mesh in the drainage hole allowed the escape of all predator beetles (Cleridae, Trogossitidae, Colydiidae, and Histeridae) in 2020, and retained only two Trogossitidae in 2021, against 249 specimens caught in the non-modified collection cup. This simple modification thus allowed the escape of almost all predators, while maintaining the traps’ efficiency at catching the target species, M. galloprovincialis. Full article

Pine wilt disease, caused by the nematode Bursaphelenchus xylophilus, poses a significant threat to pine forests worldwide. Understanding the dynamics of its spread is crucial for effective disease management. In this study, we investigated the involvement of asymptomatic carrier trees in the expansion of pine wilt disease through a series of experiments. Cage-releasing experiments revealed that sexually immature Japanese pine sawyer beetles, Monochamus alternatus, feeding on healthy pine branches drops only a minimal number of nematodes (primary infection). However, sexually mature beetles, still harboring numerous nematodes, fly to weakened trees for breeding and extend their feeding activities to healthy pines around weakened trees, infecting them with nematodes and thus spreading the disease further. Inoculation experiments on field-planted black pine seedlings demonstrated that even a small number of nematodes can lead to a high occurrence of asymptomatic carrier trees. Our findings suggest that nematode infections transmitted by sexually mature Monochamus beetles significantly contribute to the expansion of pine wilt damage and play a crucial role in the persistence of asymptomatic carrier trees. This conclusion is based on cage-release experiments demonstrating nematode transmission by mature beetles and inoculation experiments highlighting the conditions leading to asymptomatic carrier trees. Full article

To understand the spread of the pine wood nematode Bursaphelenchus xylophilus (Steiner and Buhrer, 1934; Nickle, 1970) and identify infected trees, the dispersal ability of insects was examined. In this study, the effects of sex, adult age, and morphological traits on the flight performance (such as flight distance, time, and speed) of Monochamus alternatus (Hope, 1843) were investigated using flight mills. Over a period of 8 weeks, a total of 42 newly emerged adult beetles were tethered to flight mills once a week. Flight distance and time were recorded for 2 h during each session. The total flight distance of individuals that flew more than 100 m during each session was calculated. The results showed that females flew an average of 6.65 km, for 59.6 min, while males flew an average of 9.89 km, for 85.8 min. In a single flight experimental session, both sexes could fly up to approximately 2 km and were found to fly at an average speed of 1.9 m s⁻¹. In our principal component analysis (PCA), the first and second principal components were found to be highly correlated with the sex, morphological traits, and flight performances of M. alternatus. This study demonstrates that the flight ability of M. alternatus varies significantly according to body size and sex, which is fundamental and crucial for understanding the dispersal patterns of pine wilt disease. Full article

Monochamus alternatus Hope and Arhopalus rusticus (L.) are important stem-boring pests that co-occur on weakened Pinus spp. Their larvae damage the xylem and phloem of the trunks and branches. At present, the consequences of the interspecific relationship between two longicorn beetles on the same host of Pinus trees are unclear. The population dynamics and spatial distribution of these two species on Pinus thunbergii trees were investigated to clarify the ecological niches and interspecific relationship of two longicorn beetles on the different degrees of decline in P. thunbergii trees. The results showed temporal niche overlap values from 0.02 ± 0.01 to 0.05 ± 0.02, suggesting a very high degree of temporal ecological niche segregation and no competition in temporal niche resources. There is significant interspecific competition between the two longicorn beetles in spatial distribution, and the spatial niche overlap values are 0.67 ± 0.11 and 0.61 ± 0.09 in the middle and late stages of the decline in P. thunbergii trees, respectively. Full article

In this study, methods are proposed for analyzing the susceptibility of forest stands to attacks by forest insects on the basis of Earth remote sensing data. As an indicator of the state of forest stands, we proposed to use a parameter of the sensitivity of a vegetation index (normalized difference vegetation index; NDVI) during a vegetative period to changes in the radiative temperature of the territory (land surface temperature; LST) determined from satellite data of the Terra/Aqua system. The indicator was calculated as a spectrum of a response function in an integral equation linking changes of NDVI to those of LST. Backtesting was carried out using data from two outbreaks of the Siberian silk moth Dendrolimus sibiricus Tschetv. and outbreaks of the white mottled sawyer Monochamus urussovi Fischer and of the four-eyed fir bark beetle Polygraphus proximus Blandford in taiga forests of Krasnoyarsk Territory in Russia. In addition, the state of fir stands in the year 2023 was examined when damage to the forest stands was not yet noticeable, but Siberian silk moth adults were found in pheromone traps. It was shown that the proposed indicator of susceptibility of forest stands changed significantly 2–3 years before the pest outbreak in outbreak foci of the studied areas. Thus, the proposed indicator can be used to predict outbreaks of insect pests. The proposed approach differs from commonly used remote sensing methods in that, rather than using absolute values of remote indicators (such as, for example, NDVI), it focuses on indicators of the susceptibility of these remote indicators to the characteristics of the natural environment. Since any given point on the planet is characterized by a seasonally varying temperature, it is always possible to determine the sensitivity of a remote sensing indicator to changes in the environment that are not directly related to the absolute value of the indicator. Future studies are expected to examine susceptibility indices as a function of forest stand location and species, and to examine the length of spatial correlation of susceptibility indices, which may provide information on the possible extent of future insect outbreaks. Full article

The pine wood nematode (PWN) uses several Monochamus species as vehicles, through a temporary hitchhiking process known as phoresy, enabling it to access new host plant resources. Monochamus saltuarius acts as a new and major vector of the PWN in Northeastern China, showing lower PWN carrying capacity and a shorter transmission cycle compared to established vectors. The apparently altered symbiotic relationship offers an interesting area for researching the costs and adaptions involved in nematode–beetle, a specialized phoresy. We analyzed the response and fitness costs of M. saltuarius through physiological measurements and transcriptomics. The PWN exerted adverse repercussions on the growth and development of M. saltuarius. The PWN accelerated larval development into pupae, while beetle adults carrying the PWN exhibited an elevated abnormality rate and mortality, and reduced starvation resistance. During the pupal stage, the expression of growth-related genes, including ecdysone-inducible genes (E74EA), cuticle proteins, and chitin genes (CHTs), markedly increased. Meanwhile, the induced immune response, mainly by the IMD and Toll signaling pathways, could be a contributing factor to adult abnormality and mortality. Adult gonads and trachea exhibited enrichment in pathways related to fatty acid elongation, biosynthesis, and metabolism. FASN, ELOVL, and SCD possibly contributed to resistance against PWN. Our research indicated that phoretic interactions between vector beetles and PWN vary throughout the vector’s lifespan, particularly before and after entry into the trachea. This study highlighted the fitness costs of immunity and metabolism on the vector beetle, indicating the adaptation mechanisms and evolutionary trade-offs to PWN. Full article

The Japanese pine sawyer Monochamus alternatus serves as the primary vector for pine wilt disease, a devastating pine disease that poses a significant threat to the sustainable development of forestry in the Eurasian region. Currently, trap devices based on informational compounds have played a crucial role in monitoring and controlling the M. alternatus population. However, the specific proteins within M. alternatus involved in recognizing the aforementioned informational compounds remain largely unclear. To elucidate the spatiotemporal distribution of M. alternatus chemosensory-related genes, this study conducted neural transcriptome analyses to investigate gene expression patterns in different body parts during the feeding and mating stages of both male and female beetles. The results revealed that 15 genes in the gustatory receptor (GR) gene family exhibited high expression in the mouthparts, most genes in the odorant binding protein (OBP) gene family exhibited high expression across all body parts, 22 genes in the odorant receptor (OR) gene family exhibited high expression in the antennae, a significant number of genes in the chemosensory protein (CSP) and sensory neuron membrane protein (SNMP) gene families exhibited high expression in both the mouthparts and antennae, and 30 genes in the ionotropic receptors (IR) gene family were expressed in the antennae. Through co-expression analyses, it was observed that 34 genes in the IR gene family were co-expressed across the four developmental stages. The Antenna IR subfamily and IR8a/Ir25a subfamily exhibited relatively high expression levels in the antennae, while the Kainate subfamily, NMDA subfamily, and Divergent subfamily exhibited predominantly high expression in the facial region. MalIR33 is expressed only during the feeding stage of M. alternatus, the MalIR37 gene exhibits specific expression in male beetles, the MalIR34 gene exhibits specific expression during the feeding stage in male beetles, the MalIR8 and MalIR39 genes exhibit specific expression during the feeding stage in female beetles, and MalIR8 is expressed only during two developmental stages in male beetles and during the mating stage in female beetles. The IR gene family exhibits gene-specific expression in different spatiotemporal contexts, laying the foundation for the subsequent selection of functional genes and facilitating the full utilization of host plant volatiles and insect sex pheromones, thereby enabling the development of more efficient attractants. Full article

The longicorn beetle Monochamus saltuarius (Coleoptera; Cerambycidae) is an insect vector that transmits the pine wood nematode Bursaphelenchus xylophilus, a serious issue in pine forests in China, Japan, and South Korea. Dastarcus helophoroides and Scleroderma guani are effective in controlling M. saltuarius. However, the application of these parasites for the direct control of vector insects requires detailed analyses of the suitability of the selected natural enemies in potential pest areas, particularly under climate change. Based on species distribution records as well as the current and projected climate change trends up to 2050, we utilized an optimized Maxent algorithm to predict the potential distribution patterns of M. saltuarius and its natural enemies in China. Furthermore, we estimated Schoener’s D to quantify the overlap in adaptability between M. saltuarius and its natural enemies. The potentially suitable areas predicted under the current climate conditions were concentrated mainly in northeast and north China. Additional suitable areas were detected in central, eastern, northwestern, and southwestern China. Under future climate conditions, the suitable range of M. saltuarius gradually shifted southward, with a tendency to expand into high-altitude and colder regions, such as Sichuan, Qinghai, and Tibet. The potential distribution of the natural enemies D. helophoroides and S. guani continued to expand under climate change. A comparison of the appropriate habitats of M. saltuarius and natural enemy insects indicated that D. helophoroides is more suitable for initial biological control in north, northeast, and central China as well as certain northwest and coastal regions. S. guani could be prioritized for nationwide release, while joint control using both species may be effective in Liaoning, Hebei, and Tianjin provinces. These analyses demonstrate that future climate change is likely to exert adverse effects on the potential distribution of M. saltuarius but is favorable for the potential distributions of natural enemies. This study offers important insights into the effective control of M. saltuarius and provides an experimental basis for the utilization of natural enemies according to the characteristics of different regions. Full article

Monochamus alternatus Hope (Coleoptera: Cerambycidae), an invasive beetle that has caused billions of dollars in economic losses, is a serious pest of Pinus massoniana in many Asian countries. Clarifying the eye pigment gene and its knockdown phenotype of M. alternatus can provide functional gene identification and a marker for screening of gene editing, as well as help develop new control ideas. In this study, we first screened the transcriptome and found one homologous gene of tryptophan 2,3-dioxygenase (TDO) and one of kynurenine-3-monooxygenase (KMO). By measuring the expression levels of TDO and KMO in different developmental periods, it was indicated that TDO and KMO were expressed in various stages of M. alternatus. The gene expression of MaKMO was higher than MaTDO, showing high expression after pupation and decreasing at the beginning of eclosion. MaTDO and MaKMO were knocked down using RNA interference technology in different periods of expression, and the temporal expression changes were obtained using RT-qPCR technology. The results showed that the expressions of MaTDO and MaKMO were significantly inhibited by the injection of dsRNA; the expressions of MaTDO at 48 h, 96 h and after pupation were 21.9%, 32.3% and 59.2%, respectively, meanwhile, those of KMO were 23.4%, 25.0% and 69.7%, respectively. There was a significant change in eye color, and the beetles were able to pupate normally without their activity being affected. Therefore, both MaTDO and MaKMO can be used as tag genes for M. alternatus. A dominant marker system based on eye color can be developed for the genetic manipulation and control of M. alternatus. Full article

The longhorn beetle Monochamus alternatus is an important conifer stem-boring pest and the main vector in Asia of the invasive pine wood nematode Bursaphelenchus xylophilus, which causes a devastating pine disease. Field experiments were carried out to evaluate the effect of coating black panel traps with different concentrations of an anti-adhesive material, Teflon, on Monochamus captures. Tests were also conducted to look at the possible decrease in the Teflon effect with exposure duration as well as the effect of the implementation of an anti-escape ring on the trap. The three tested Teflon concentrations significantly improved the captures of M. alternatus with regard to those with uncoated traps. The beetle captures increased by 108.3% in traps coated with a 4x Teflon dilution, but no significant differences in captures were observed when the traps were coated with either a Teflon stock solution or a 8x dilution. The trapping efficiency gradually decreased with the duration of exposure of the coated traps. No significant difference was observed after one year of exposure, but the trapping efficiency significantly decreased by 36.6% after 2 years and by 72.0% after 3 years. Two-year old, coated traps equipped with an anti-escape ring were nearly three times more efficient than those without an anti-escape ring, but the captures were still lower than those obtained with newly coated traps. The present study provides valuable information for the future development of environmentally friendly prevention methods. Attractants combined with Teflon coating and an anti-escape ring could significantly improve the trapping efficiency of M. alternatus adults, which may allow for the reduction of the population density of M. alternatus and transmission probability of pine wilt disease. Full article

Monochamus alternatus Hope (Coleoptera: Cerambycidae), an invasive beetle that has caused billions of dollars of economic losses, is a serious pest of Pinus massoniana in many Asian countries. An efficient RNAi system is helpful for functional genomics research on M. alternatus. In this study, a tryptophan 2,3-dioxygenase (TDO) related to the ommochrome synthesis in insects was identified. Using RNAi technology, the M. alternatus TDO gene was silenced by injecting dsRNA into pupae, and individuals were analyzed by phenotype and expression of the TDO gene by RT-qPCR. The results show that TDO is expressed in different developmental stages of M. alternatus, having its peak expression during the prepupal stage. White-eye phenotypes were observed in the pupal and adult stages after dsRNA injection, and a significant 81% decrease in TDO mRNA levels 48 h after injection was determined by RT-qPCR. This gene can be used as a genetic marker and is an important discovery for future genetic engineering tools to control M. alternatus populations. Full article

Pine wilt disease (PWD) caused by the pine wood nematode (PWN) is China’s most serious forest disease in recent decades. Its complex disease system with unclear pathogenesis and differentiated pathogenicity makes it challenging to manage and control. PWD has spread rapidly in Northeast and Northwest China in recent years, exceeding previous predictions and the traditional understanding of its potential distribution. This paper reviewed the comprehensive risk of PWD in Northeast and Northwest China through the occurrence of influencing factors. Regarding PWN’s temperature resistance, all regions of China are suitable for PWD. In terms of altitude, the PWD system is mainly distributed below 1000 m. In China, Pinus and Larix species are confirmed host trees of PWN, while Monochamus alternatus and M. saltuarius are confirmed vector insects of PWN. In this case, PWD may occur in all low-altitude pine forests in China. Northeast China has a higher risk than Northwest China due to its distribution of suitable host trees and vector beetles at low altitudes. To confront the threat, two scientific bottlenecks are required to be demonstrated. The first is the pathogenicity of Chinese PWN strains to Chinese Picea and Abies species. The other is the geographical distribution and highest altitude distribution of other Monochamus species in the Palaearctic region of China and their PWN transmission ability. We also suggest strengthening plant quarantining in Northeast China. In conclusion, this review comprehensively analyzes the risk of PWD in Northeast and Northwest China in terms of temperature, altitude, host trees, and vector insects. It provides a new perspective and reference for the management and research of PWD in China. Full article

Cerambycid beetles (Cerambycidae) are major forest pests, posing a serious threat to the security of forest resources worldwide. Extensive research has focused on the control of cerambycid beetles from physiological and biochemical perspectives. Despite the important roles of insect haemolymph in physiological processes, efficient collection methods for Cerambycidae are lacking. For the efficient and easy collection of large amounts of pure haemolymph from adult cerambycid beetles, a new method, named net centrifugation, was developed. Three species of cerambycid beetles with large differences in size, Anoplophora chinensis, Monochamus saltuarius and Saperda populnea, were selected for the study. Haemolymph was collected by the newly developed net centrifugation method—in which an inner nylon net is used during centrifugation under optimised conditions, and a relatively small wound is generated on the insect—as well as the traditional tearing method and double centrifugation method. Among the three methods evaluated, the net centrifugation method caused the least damage to cerambycid beetles during the whole operation. This method resulted in the most haemolymph from a single beetle, with the lowest turbidity, mostly pure haemocytes in the precipitate, the clearest haemolymph smears by microscopy and the highest quality of RNA extracted from haemocytes. The net centrifugation method has a high collection efficiency, providing important technical support for haemolymph extraction and entomological research. Full article

Pine wilt disease (PWD) has caused extensive mortality in pine forests worldwide. The longicorn beetle Monochamus saltuarius, as the vector of the invasive species Bursaphelenchus xylophilus, plays an important role in the infection cycle. Although the gut microbiota and its contribution to health and disease have been extensively documented, it is unclear whether B. xylophilus affects the longicorn gut microbiota because of a lack of understanding of potential temporal changes in the microbial composition of the vector beetles. In this study, we collected beetles at the emergence and mating stages, and divided them into two groups according to whether they carried nematodes. Based on 16S rDNA sequence analysis, 174 bacterial species were identified that belonged to 112 genera, 53 families, and 8 phyla. Bursaphelenchus xylophilus increased the microflora abundance and diversity of the infected M. saltuarius. In addition, Firmicutes and Bacteroidetes were more abundant in infected M. saltuarius at the same developmental stage. Some of the bacteria in these two phyla were the key species in the co-occurrence network of intestinal flora and represented a unique module in the co-occurrence network of infected M. saltuarius. We found some high abundance colonies in the intestinal tract of infected M. saltuarius during the emergence period that were mostly related to metabolism. Compared with the emergence period, there were more similar microorganisms in the intestinal tract of M. saltuarius during the mating period. With the change in growth environment and continuous feeding, the intestinal microorganisms gradually stabilized and became single species. Full article

As a vector of pine wood nematode disease, Monochamus alternatus is wood-boring, cryptic, and extremely difficult to control—features that have made them a disastrous problem. In this study, we present a method of scanning the galleries of Monochamus alternatus using CT (computed tomography) technology to obtain their systematic structure via 3D (three-dimensional) reconstruction, so as to clarify the gallery types and their structural parameters. TLC (thin-layer chromatography) scanning on wood segments damaged by M. alternatus was performed using a 128-row spiral CT GE Revolution EVO to obtain 64-layer CT scanned images. From the scanned images, we were able to clearly identify the beetle larvae and their galleries. The galleries were clearly delineated from the peripheral xylem, except for parts that were blocked by a frass–feces mixture, which were slightly blurred. Three-dimensional reconstruction of the galleries showed that most of the gallery types were C-shaped, and a few were S-shaped or Y-shaped. There was only one larva per gallery, and the galleries were separate. The vicinity of the entrance hole and the anterior part of the pupal chamber were blocked with a frass–feces mixture. There were no significant differences among the galleries’ parameters, such as the width of the entrance holes, tunneling depth, vertical length, blockage length and volume, total length of the galleries, and boring volume. With MIMICS (Materialise’s interactive medical image control system) image processing software, the images of each layer were made into a composite image, providing an effective way to visualize the 3D distribution of galleries. Using the methodology outlined in this study, both a single gallery structure and the spatial distribution of multiple galleries of M. alternatus can be shown, and the specific parameters of galleries can also be accurately calculated, which provides new ideas and methods for carrying out ecological and scientific research and precise prevention and control techniques of M. alternatus. Full article