Forest Insect Research Articles

Genome-wide markers show continental structuring and mitonuclear discordance in the forest tent caterpillar (Malacosoma disstria Hübner) (Lepidoptera: Lasiocampidae)

Abstract The forest tent caterpillar, Malacosoma disstria Hübner (Lepidoptera: Lasiocampidae), is an irruptive forest pest found throughout North America. Widespread species such as M. disstria are exposed to historical and contemporary processes that are not uniform and can generate regionally distinct genomic variation. Previous analyses used a short mitochondrial fragment to infer broad-scale phylogeographic patterns in M. disstria, whereas nuclear markers have been previously applied only in a smaller geographic region. In this study, we quantified M. disstria population variation with genome-wide single nucleotide polymorphisms and cytochrome c oxidase from mitochondrial DNA. Using highly variable genome-wide markers, we resolved clear genomic differences among populations of M. disstria east of the Rocky Mountains that were not detected using mitochondrial variation alone. We also did not detect host-associated divergence in either our genomic or mitochondrial data. Our results highlight the utility of genome-wide markers to resolve intraspecific population structure within a widespread species and support the need for further biogeographic sampling of this forest insect pest.

Sudden and simultaneous population outbreak of Neoaulacoryssus speciosus in an urban area of 12 municipalities in the Caatinga biome.

The ground beetle, Neoaulacoryssus speciosus (Coleoptera: Carabidae) is of high relevance to field because it has been recorded as a pest of seeds and young plants of vegetables and other crops and a predator in agricultural crops, forest and weeds in Brazil. However, natural habitat changes are increasing agriculture and forest insect outbreaks in urban areas. A N. speciosus population outbreak occurred in October and November 2018 simultaneously in 12 neighboring municipalities at the beginning of the rainy season in the northern region of Minas Gerais State, Brazil. The objectives of this study were to report a sudden and simultaneous population outbreak of N. speciosus and to describe the factors of habitat change that could have contributed to this invasion in 12 municipalities in the northern region of Minas Gerais State in the Caatinga biome of Brazil. In addition, female and male genitals were described and illustrated, the scientific classification revised and common names of N. speciosus listed. Thousands of males and females of N. speciosus agglomerated in shady, humid places during the day and night for about 15 days. Neoaulacoryssus speciosus has been identified and illustrated, its scientific classification revised and four common names listed for this species.

Climate and pest interactions pose a cross-landscape management challenge to soil and water conservation

Climate change and biological invasions by plant pests (weeds), agriculture and forest insect pests (insects), and microbial pests (plant pathogens) are complex interactive components of global environmental change. The influence of pest distribution and prevalence across landscapes are challenging the conservation and sustainability of natural resources, agricultural production, native biological diversity, and the valuable ecosystem services they provide (Huenneke 1997; Vitousek 1997; Juroszek and von Tiedemann 2013; Ziska and Dukes 2014). Since 2000, numerous scientific studies indicate accelerating climate change is posing substantial risks to natural and managed systems in North America (IPPC 2022). Intensified droughts, large-scale wildfires, and increased demands for limited surface and groundwater water supplies in arid regions are threatening the sustainability of irrigated agriculture and contributing to economic losses (Stewart et al. 2020), while extreme rainfall events are contributing to severe riverine and urban flooding across the United States. Climate change affects crops, rangelands, forests, and natural areas directly through the immediate effects of temperature, precipitation, and atmospheric carbon dioxide (CO₂) levels and thereby impacts production and management systems. These effects are amplified by climate-driven increases in weed, insect, and plant pathogen problems that further complicate related factors such as water, nutrient, and pest management (Walthall et al. 2013). Changing climates also alter physiological, ecological, and evolutionary processes that can support increased establishment, invasiveness, local spread, and geographic range changes of weeds, insects, and plant pathogens (Chidawanyika et al. 2019; Gallego-Tevár et al. 2019; Ziska et al. 2019) that have cascading effects on soil and water quality, and human livelihoods. Thus, a need exists for cross-habitat and landscape/watershed-scale perspectives to improve understanding of mechanisms underlying pest fitness and impacts within and across integrated systems.

Regulatory Processes in Populations of Forest Insects (A Case Study of Insect Species Damaging the Pine Pinus sylvestris L. in Forests of SIBERIA)

The present study addresses the population dynamics of five species of phyllophagous forest insects in five habitats located in the Krasnoturansk pine forest (south Middle Siberia). Based on the data of insect surveys obtained during 1979–2016, autoregressive (AR) models of population dynamics have been proposed, with the current population density being dependent on population densities of the preceding years. Methods of calculation of the autoregression order and coefficients of AR equations have been presented. The study shows that, for different insect species in different habitats, the lags between the current population density and the densities of the previous years are not the same. AR equations characterize positive and negative feedbacks regulating population dynamics. By using AR equations, up to 90% of population density variance can be taken into account. Stability margin, which is calculated from coefficients of AR models, has been proposed as a parameter to assess the stability of population dynamics. A small stability margin indicates a high risk of outbreak of an insect species.

Survey, Consumption Methods and Uses of Edible Forest Insects in Selected Local Government Areas, Cross River State, Nigeria

The survey and consumption methods of edible forest insects was investigated within a period of eight months. Information on respondents’ demography, availability, harvesting methods and uses was collected using questionnaire and field survey. Data generated was analysed using frequency tables, charts and bar diagrams. Females (51%) were higher in number than males (49%) in the collection of edible forest insects, with over 70 percent of the collectors haven’t completed their secondary (46%) and tertiary (32%) education. The main preservation and consumption methods were roasting and frying, with majority of the people utilizing the insects majorly as food ingredients and sweetener. Most of the insects identified were consumed at adult stage, with exception of caterpillar that was consumed at larval stage. In all the locations and with the exception of termites and crickets which were available during the rainy and dry seasons, respectively, all other insects identified were available all year round. There was a strong positive relationship interms of insect availability, collection methods and uses between Akamkpa and Obubra (rs = 0.089), Obubra and Ogoja (rs – 0.689). The was not the same for Ogoja and Akamkpa (rs = 0.352), as well as ogoja and Obubra (rs = 0.102), respectively.

Assessing Molecular Diversity in Native and Introduced Populations of Red Wood Ant Formica paralugubris.

The Formica rufa group comprises several ant species which are collectively referred to as "red wood ants" and play key roles in boreal forest ecosystems, where they are ecologically dominant and greatly influence habitat dynamics. Owing to their intense predatory activity, some of these species are used as biocontrol agents against several forest insect pests and for this aim in Italy, nearly 6000 ant nests were introduced from their native areas in the Alps to several Appeninic sites during the last century. In this work, we assessed and compared the genetic variability and structure of native and introduced populations of F. paralugubris, thus evaluating the extent of genetic drift that may have occurred since the time of introduction, using amplified fragment length polymorphism (AFLP) markers. PCR amplification with a fam_EcoRI-TAC/MseI-ATG primers combination produced a total of 147 scorable bands, with 17 identified as outlier loci. The genetic variation was higher in the introduced population compared to the native ones that, on the other hand, showed a higher diversity between nests. AMOVA results clearly pointed out that the overall genetic structure was dominated by among-worker variation, considering all populations, the Alpine vs. Apennine groups and the comparison among native and related introduced populations (all ranging between 77.84% and 79.84%). Genetic analyses unveiled the existence of six main different groups that do not entirely mirror their geographic subdivision, pointing towards a wide admixture between populations, but, at the same time, rapid diversification of some Apennine populations. Future studies based on high-throughput genomic methods are needed to obtain a thorough understanding of the effects of environmental pressure on the genetic structure and mating system of these populations.

Weather and nest cavity characteristics influence fecundity in mountain chickadees.

Examining direct and indirect effects on reproduction at multiple scales allows for a broad understanding of species' resilience to environmental change. We examine how the fecundity of the mountain chickadee (Poecile gambeli), a secondary cavity-nesting, insectivorous bird, varied in relation to factors at three scales: regional weather conditions, regional- and site-level food availability, site-level community dynamics, and nest-level cavity characteristics. We hypothesized that earlier laying dates and higher fecundity (clutch size, nest survival, brood size) would be associated with milder climatic conditions, increased food from insect outbreaks, lower densities of conspecifics and nest predators (red squirrel; Tamiasciurus hudsonicus), and safer (smaller, higher) cavities. We collected data on laying date, clutch size, brood size, nest fate (success/failure), and cavity characteristics from 513 mountain chickadee nests in tree cavities in temperate mixed coniferous-broadleaf forest in interior British Columbia, Canada, from 2000 to 2011. We surveyed annual abundances of mountain chickadees and squirrels using repeated point counts, and mountain pine beetle (Dendroctonus ponderosae) and lepidopteran defoliators by monitoring host trees and by using regional-scale aerial overview forest insect survey data. We used weather data (temperature, rain, snow) from a local Environment and Climate Change Canada weather station. We modeled laying date, clutch size, daily nest survival, and brood size as a function of predictors at regional-, site-, and nest-scales. Measures of fecundity varied dramatically across years and spatial scales. At the regional (study-wide) scale, chickadees laid earlier and larger first clutches in warmer springs with minimal storms, and daily nest survival (DSR) increased with a 2-year lag in growing season temperature. Despite a doubling of mountain chickadee density that roughly accompanied the outbreaks of mountain pine beetle and lepidopteran defoliators, we found little evidence at the site scale that fecundity was influenced by insect availability, conspecific density, or predator density. At the nest scale, DSR and brood size increased with clutch size but DSR declined with nest cavity size indicating a positive reproductive effect of small-bodied cavity excavators. Double-brooding, rare in chickadees, occurred frequently in 2005 and 2007, coinciding with early breeding, high food availability from insect outbreaks, and warm spring temperatures with 0-1 spring storms. Our results support the idea that fecundity in secondary cavity-nesting species is impacted directly and indirectly by weather, and indirectly through changes in community dynamics (via cavity resource supply). We stress the importance of adopting holistic, community-level study frameworks to refine our understanding of fecundity in opportunistic and climate-sensitive species in future.

Variation in Larval Thermal Tolerance of Three Saproxylic Beetle Species.

Temperature is a key abiotic condition that limits the distributions of organisms, and forest insects are particularly sensitive to thermal extremes. Whereas winged adult insects generally are able to escape unfavorable temperatures, other less-vagile insects (e.g., larvae) must withstand local microclimatic conditions to survive. Here, we measured the thermal tolerance of the larvae of three saproxylic beetle species that are common inhabitants of coarse woody debris (CWD) in temperate forests of eastern North America: Lucanus elaphus Fabricius (Lucanidae), Dendroides canadensis Latreille (Pyrochroidae), and Odontotaenius disjunctus Illiger (Passalidae). We determined how their critical thermal maxima (CTmax) vary with body size (mass), and measured the thermal profiles of CWD representing the range of microhabitats occupied by these species. Average CTmax differed among the three species and increased with mass intraspecifically. However, mass was not a good predictor of thermal tolerance among species. Temperature ramp rate and time in captivity also influenced larval CTmax, but only for D. canadensis and L. elaphus respectively. Heating profiles within relatively dry CWD sometimes exceeded the CTmax of the beetle larvae, and deeper portions of CWD were generally cooler. Interspecific differences in CTmax were not fully explained by microhabitat association, but the results suggest that the distribution of some species within a forest can be affected by local thermal extremes. Understanding the responses of saproxylic beetle larvae to warming habitats will help predict shifts in community structure and ecosystem functioning in light of climate change and increasing habitat fragmentation.

Diversity and Distribution of Forest Insects

When we ponder or discuss present-day challenges faced by entomology, we focus first of all on climate change, since the warming climate contributes to a dramatic extension in the ranges of many invertebrate species [...]

Forest Landscape Effects on Dispersal of Spruce Budworm Choristoneura fumiferana (Clemens, 1865) (Lepidoptera, Tortricidae) and Forest Tent Caterpillar Malacosoma disstria Hübner, 1820 (Lepidoptera, Lasiocampidae) Female Moths in Alberta, Canada.

Leaf-rollers and tent caterpillars, the families Torticidae and Lasiocampidae, represent a significant component of the Lepidoptera, and are well-represented in the forest insect pest literature of North America. Two species in particular-spruce budworm (Choristoneura fumiferana (Clem.)) and forest tent caterpillar (Malacosoma disstria Hbn.)-are the most significant pests of the Pinaceae and Salicacae, respectively, in the boreal forest of Canada, each exhibiting periodic outbreaks of tremendous extent. Dispersal is thought to play a critical role in the triggering of population eruptions and in the synchronization of outbreak cycling, but formal studies of dispersal, in particular studies of long-range dispersal by egg-bearing adult females, are rare. Here, it is shown in two independent studies that adult females of both species tend to disperse away from sparse or defoliated forest, and toward intact or undefoliated forest, suggesting that long-range dispersal during an outbreak peak is adaptive to the species and an important factor in their population dynamics, and hence their evolutionary biology.

Comparison of Iflavirus Diversity in Agricultural and Forest Pest Lepidoptera

Iflaviridae is a novel and important family of viruses in the Picornavirales order that infects invertebrates. Iflaviruses are non-enveloped, linear, positive single-stranded RNA viruses. The importance of iflaviruses in agriculture and forestry is twofold because these viruses, both cause economic loss by making insects such as honey bees and silkworms ill and prevent economic loss by making agricultural and forest pest insects ill. Therefore, iflaviruses contain highly interesting isolates that infect both beneficial and harmful insects in agriculture. Its genome structure, like most RNA viruses, has a very small genome size (8.8-10 kb), with a single open reading frame in the entire genome. The genomes of 14 infective iflaviruses that infect agricultural and forest pest insects from different countries have been analyzed so far. In this study, the similar relationship between these 14 viruses, whose complete genomes are available, was analyzed according to the complete sequence of the polyprotein. The results showed that the virus isolates obtained from forest pest insects were closely related to each other. Similarly, it was revealed that the iflaviruses obtained from insects that damage agricultural products are more similar to each other. In addition, the results from this study support previous studies on adding a new genus to the Iflaviridae family, which has only one genus.

Management of Forest Pests and Diseases

The occurrence patterns of forest insect pests and diseases have been altered by global events such as climate change. Recent developments in improved monitoring methods and tools for data analyses provide new opportunities to understand the causes and consequences of such changes. Using a variety of management tools, forest pest management programs can mitigate the influence of global changes on forest health. The goal of this Special Issue is to improve our understanding of the root causes of changes that have induced global changes. Fifteen papers are included in this Special Issue, covering several issues in forest pest management. One paper reviews the causes of Korean oak wilt, and another paper discusses fourteen invasive tree pests in Russia. The remaining thirteen papers cover issues related to the monitoring and management of forest pests. These studies provide a better understanding of the causes of change in the patterns of forest pests under the influence of global changes. These reviews also contribute to the development of forest-pest-management strategies to mitigate such impacts on forests due to global changes.

SURVEY OF EDIBLE FOREST INSECTS UTILIZED BY THE PEOPLE IN SOUTH WEST NIGERIA

This study was conducted to take inventory of edible forest insects and evaluate their contributions to the livelihood of the people of southwest Nigeria. Multi-stage sampling technique was used to select three states (Lagos, Ogun and Kwara). Four towns were selected in each of the states while five respondents were randomly selected from each town. Sixty (60) Pre-tested semi-structured questionnaire was administered to selected respondents in the study area. Data collected were analyzed using descriptive statistics. The study showed that majority of the respondents are married (53.4 %), female (61.7 %) with (75 %) having at least secondary education. The study also revealed that 10 different insects were collected and utilized for various purposes by the respondents with Macrotermes bellicosus and Apis mellifera being the most sort after insects, (18.2 %) each, while 66.7 % of the respondents collect/harvest their products during raining season mostly by hunting (30.1 %). Majority (70.7 %) of the respondents generate over ₦20,000 from sales of edible insects annually, while 21.5 % of the respondents opined that seasonal availability and irritating physical structure are the major constraints militating against the consumption of edible insects in the study area. Avoiding deforestation and indiscriminate forest fire were the major conservation measures suggested by the respondents. It was recommended that government should enforce legislation against bush burning and illegal felling of trees.

Integrating Multi-Scale Remote-Sensing Data to Monitor Severe Forest Infestation in Response to Pine Wilt Disease

Pine wilt disease (PWD) is one of the most destructive forest diseases that has led to rapid wilting and mortality in susceptible host pine trees. Spatially explicit detection of pine wood nematode (PWN)-induced infestation is important for forest management, policy making, and practices. Previous studies have mapped forest disturbances in response to various forest diseases and/or insects over large areas using remote-sensing techniques, but these efforts were often constrained by the limited availability of ground truth information needed for the calibration and validation of moderate-resolution satellite algorithms in the process of linking plot-scale measurements to satellite data. In this study, we proposed a two-level up-sampling strategy by integrating unmanned aerial vehicle (UAV) surveys and high-resolution Radarsat-2 satellite imagery for expanding the number of training samples at the 30-m resampled Sentinel-1 resolution. Random forest algorithms were separately used in the prediction of the Radarsat-2 and Sentinel-1 infestation map induced by PWN. After data acquisition in Muping District during August and September 2021, we first verified the ability of a deep-learning-based object detection algorithm (i.e., YOLOv5 model) in the detection of infested trees from coregistered UAV-based RGB images (Average Precision (AP) of larger than 70% and R2 of 0.94). A random forest algorithm trained using the up-sampling UAV infestation map reference and corresponding Radarsat-2 pixel values was then used to produce the Radarsat-2 infestation map, resulting in an overall accuracy of 72.57%. Another random forest algorithm trained using the Radarsat-2 infestation pixels with moderate and high severity (i.e., an infestation severity of larger than 0.25, where the value was empirically set based on a trade-off between classification accuracy and infection detectability) and corresponding Sentinel-1 pixel values was subsequently used to predict the Sentinel-1 infestation map, resulting in an overall accuracy of 87.63%, where the validation data are Radarsat-2 references rather than UAV references. The Sentinel-1 map was also validated by independent UAV surveys, with an overall accuracy of 76.30% and a Kappa coefficient of 0.45. We found that the expanded training samples by the integration of UAV and Radarsat-2 strengthened the medium-resolution Sentinel-1-based prediction model of PWD. This study demonstrates that the proposed method enables effective PWN infestation mapping over multiple scales.

A full-length transcriptome and gene expression analysis of three detoxification gene families in a predatory stink bug, Picromerus lewisi.

The predatory stink bug P. Lewisi shows potential for Integrated Pest Management programs for controlling Lepidoptera pest insects in crops and forests. The importance of this insect for biological control has stimulated several studies into its biology and ecology. However, P. lewisi has little genetic information available. In the present study, PacBio single-molecule real-time (SMRT) sequencing and Illumina RNA-seq sequencing technologies were used to reveal the full-length transcriptome profiling and tissue-specific expression patterns of P. lewisi. A total of 12,997 high-quality transcripts with an average length of 2,292 bp were obtained from different stages of P. lewisi using SMRT sequencing. Among these, 12,101 were successfully annotated in seven public databases. A total of 67 genes of cytochrome P450 monooxygenases, 43 carboxylesterase genes, and 18 glutathione S-transferase genes were identified, most of which were obtained with full-length ORFs. Then, tissue-specific expression patterns of 5th instar nymphs were analyzed using Illumina sequencing. Several candidate genes related to detoxification of insecticides and other xenobiotics as well as the degradation of odors, were identified in the guts and antennae of P. lewisi. The current study offered in-depth knowledge to understand the biology and ecology of this beneficial predator and related species.

Forest Insect Biosecurity: Processes, Patterns, Predictions, Pitfalls.

The economic and environmental threats posed by non-native forest insects are ever increasing with the continuing globalization of trade and travel; thus, the need for mitigation through effective biosecurity is greater than ever. However, despite decades of research and implementation of preborder, border, and postborder preventative measures, insect invasions continue to occur, with no evidence of saturation, and are even predicted to accelerate. In this article, we review biosecurity measures used to mitigate the arrival, establishment, spread, and impacts of non-native forest insects and possible impediments to the successful implementation of these measures. Biosecurity successes are likely under-recognized because they are difficult to detect and quantify, whereas failures are more evident in the continued establishment of additional non-native species. There are limitations in existing biosecurity systems at global and country scales (for example, inspecting all imports is impossible, no phytosanitary measures are perfect, knownunknowns cannot be regulated against, and noncompliance is an ongoing problem). Biosecurity should be a shared responsibility across countries, governments, stakeholders, and individuals.

A spectral three-dimensional color space model of tree crown health.

Protecting the future of forests in the United States and other countries depends in part on our ability to monitor and map forest health conditions in a timely fashion to facilitate management of emerging threats and disturbances over a multitude of spatial scales. Remote sensing data and technologies have contributed to our ability to meet these needs, but existing methods relying on supervised classification are often limited to specific areas by the availability of imagery or training data, as well as model transferability. Scaling up and operationalizing these methods for general broadscale monitoring and mapping may be promoted by using simple models that are easily trained and projected across space and time with widely available imagery. Here, we describe a new model that classifies high resolution (~1 m2) 3-band red, green, blue (RGB) imagery from a single point in time into one of four color classes corresponding to tree crown condition or health: green healthy crowns, red damaged or dying crowns, gray damaged or dead crowns, and shadowed crowns where the condition status is unknown. These Tree Crown Health (TCH) models trained on data from the United States (US) Department of Agriculture, National Agriculture Imagery Program (NAIP), for all 48 States in the contiguous US and spanning years 2012 to 2019, exhibited high measures of model performance and transferability when evaluated using randomly withheld testing data (n = 122 NAIP state x year combinations; median overall accuracy 0.89–0.90; median Kappa 0.85–0.86). We present examples of how TCH models can detect and map individual tree mortality resulting from a variety of nationally significant native and invasive forest insects and diseases in the US. We conclude with discussion of opportunities and challenges for extending and implementing TCH models in support of broadscale monitoring and mapping of forest health.

Response of cavity nesting birds to Lymantria dispar (Lepidoptera) and aerial spraying – An experimental approach

Eruptive population dynamics of forest insect species regularly attract the interest of ecologists but also often evoke debates among stakeholders concerning impacts that outbreaks or pest control activities have on forest communities including insectivorous birds. Lymantria dispar is the most serious native defoliator in mixed oak-broadleaf forests in Central Europe. To investigate the treatment effects of L. dispar density, aerial application of the insecticide Mimic (tebufenozide) and nest box accessibility for L. dispar caterpillars on nest box success of cavity nesting birds, we deployed 352 nest boxes in a full factorial experimental design with 11 replicates. L. dispar density was predicted by egg mass counts made in the year before the study. The accessibility of nest boxes for L. dispar caterpillars was manipulated in all study sites by placing nest boxes on trunks for easy access to caterpillars and on branches for more difficult access. Successful nest boxes (binary metric that combines failed breeding attempt and empty nest box) and nest productivity (number of fledged chicks in successful boxes) were monitored in the peak year of a L. dispar outbreak, during which half of the plots were treated with Mimic, as well as in the following year when L. dispar populations had widely collapsed, and no further treatments were applied. L. dispar and non-target caterpillar biomass was sampled by canopy fogging to quantify prey abundance. Caterpillar biomass was significantly reduced by Mimic in the treatment year and remained low in the post-treatment year. Despite the reduction of caterpillars, our zero-inflation model found no effect of any tested variables on nest box success of the early brood. However, in the late broods the number of successful nest boxes was reduced in Mimic treated plots in the first year by 42%, while unaffected by initial L. dispar density. The number of successful nest boxes in the second year was lower in areas with initially high L. dispar densities and there was a marginal carry-over effect of insecticide treatment. L. dispar caterpillars entered nest boxes on the trunk in higher numbers than boxes on the branch, but nest box position had no effect on nest box success of birds.We conclude that despite its strong negative impact on caterpillar prey, aerial application of Mimic targeting L. dispar caused an increase in the number of failed boxes in late broods in sprayed plots, particularly in the year of application and to some extent in the year after. We presume this delayed effect of Mimic only on late broods to be caused by Mimic-induced caterpillar shortages during first broods leading to an increased parental effort and a subsequent reduced number of second broods. The generally limited impact of Mimic might be explained by the overall extensive availability of alternate prey in oak forests in May during first broods and the ability of tits to increase their parental effort in times of caterpillar shortage. In unsprayed sites, L. dispar densities can create legacies of impact in following years, but caterpillars do not directly affect birds nest box success despite entering cavities.

Size and location of host‐plant shape the spatial pattern of forest insect

Abstract Insect–host relationships can generate spatial patterns. The effect of plant species has been widely investigated, whereas the effect of plant size was ignored. The authors characterized the spatial pattern of the swift moth Endoclita excrescens Butler by combining spatial analysis by distance indices (SADIE) and spatial point pattern analysis (SPPA). Two contiguous plots of monospecific plantations of Manchurian ash Fraxinus mandshurica with different diameters at breast height (DBH) were sampled, and the position, DBH, and count of attack holes of each ash tree were recorded. The aggregation at the landscape scale is far stronger than those at the stand scale. At the landscape scale, trees with small number of bored holes were close to each other at distances of r < 4 m. None of the significant patterns were found at the stand scale. SADIE results showed a strong association between count of attack holes and DBH at the landscape scale, whereas weak association at the stand scale. SPPA results showed that, either at the landscape or stand scale, the locations of ash trees were randomly distributed at small distance, but aggregated at large distance. The counts of holes are only dependent on the point (tree) at small distances (r < 2.5 m) at the landscape scale. These results provide basic information for sampling and precision‐targeted controlling programs.

Management of overwintering pine sawyer beetle, Monochamus alternatus with colonized Beauveria bassiana ERL836.

Monochamus alternatus is a major forest pest that spreads pine wilt disease in pine trees as a vector of pine wilt nematodes. Chemical insecticides used as fumigants to control overwintering M. alternatus in forests are highly toxic to the environment, so we investigated entomopathogenic fungus Beauveria bassiana ERL836 as an eco-friendly and alternative material to control overwintering M. alternatus. In this work, we evaluated the insecticidal activity of B. bassiana ERL836 against M. alternatus adults, the possibility of fungal colonization on pine tree bark, and finally the control efficacy of fungal pre-treatment on pine tree logs against emerging M. alternatus adults in semi-field and field conditions. M. alternatus adults were killed on the pine tree logs pre-treated with the B. bassiana ERL836. White conidia were observed not only on the surface of the dead adults but also on the pine tree logs, suggesting that the adults were killed by the fungus on the pine. A formulated ERL836 powder treatment on larvae-infested pine logs showed high insecticidal activity against adults, similar to that with the fungal powder suspension treatment, but we demonstrated that using the fungal powder was simpler than using the suspension in field conditions. Even in the field condition, the fungal powder treatment showed high insecticidal activity against M. alternatus adults, which we attribute to its ability to maintain fungal activity for a long time in field conditions by covering the pine tree logs with a film during overwintering. We confirmed that the risk that fungus-infected M. alternatus adults would spread the fungus to other non-target forest insects was low. Thus, even a high-concentration treatment in a specific area is unlikely to transmit the fungus outside that area, so it can be safely used to control this pine wilt nematode vector in forest ecosystems.