Are Climates in Canada and the United States Suitable for the European Spruce Bark Beetle, Ips typographus, and Its Fungal Associate, Endoconidiophora polonica?

Invasions of exotic forest insects and pathogens can devastate evolutionarily naïve habitats and could cause irreversible changes to urban and natural ecosystems. Given the ever-increasing volume of trade in wood and plant stock worldwide, establishment of non-native pests under climate change is one of the most important forest health concerns currently. The European spruce bark beetle, Ips typographus, is a damaging, phloem-feeding insect of Norway spruce, Picea abies, in Eurasia. Endoconidiophora polonica is the most virulent ophiostomatoid fungal associate of I. typographus. Spruce species native to North America are susceptible to this insect-pathogen complex. We studied the suitability of ‘current’ (1970–2000) and future climates (2021–2100) in Canada and the United States for these two species via ensemble species distribution models. We also determined overlapping regions favorable to both I. typographus and E. polonica. Our results indicate that, currently, climate is particularly suitable for I. typographus and E. polonica in western Canada and throughout the United States. Northward shifts in climatic suitability are projected to occur in Canada for both species under climate change. By the end of the 21st century, a coast-to-coast corridor of climatic suitability for I. typographus and E. polonica will occur in Canada under high-temperature regimes.

Investigating the Correlation between Multisource Remote Sensing Data for Predicting Potential Spread of Ips typographus L. Spots in Healthy Trees

In the last decade, thousands of hectares of forests have been lost in the Czech Republic, primarily related to European spruce bark beetle (Ips typographus L.), while more than 50% of the remaining Czech forests are in great danger, thus posing severe threats to the resilience, stability, and functionality of those forests. The role of remote sensing in monitoring dynamic structural changes caused by pests is essential to understand and sustainably manage these forests. This study hypothesized a possible correlation between tree health status and multisource time series remote sensing data using different processed layers to predict the potential spread of attack by European spruce bark beetle in healthy trees. For this purpose, we used WorldView-2, Pléiades 1B, and SPOT-6 images for the period of April to September from 2018 to 2020; unmanned aerial vehicle (UAV) imagery data were also collected for use as a reference data source. Our results revealed that spectral resolution is crucial for the early detection of infestation. We observed a significant difference in the reflectance of different health statuses, which can lead to the early detection of infestation as much as two years in advance. More specifically, several bands from two different satellites in 2018 perfectly predicted the health status classes from 2020. This method could be used to evaluate health status classes in the early stage of infestation over large forested areas, which would provide a better understanding of the current situation and information for decision making and planning for the future.

The Effect of Sanitation Felling on the Spread of the European Spruce Bark Beetle—An Individual-Based Modeling Approach

Sanitation felling is considered as the main measure to protect managed forests from damage due to outbreaks of the European Spruce Bark Beetle. In this study, we investigate the effectiveness of sanitation felling on stopping the spread of a bark beetle population from an un-managed to a managed forest area. For this, we advance an individual-based dispersion model of Ips typographus by adding the influence of wind on the beetle dispersion and by importing GIS data to simulate real world forests. To validate the new model version and to find reasonable parameter values, we conduct simulation experiments to reproduce infestation patterns that occurred in 2015, 2016, and 2017 within the national park Saxon Switzerland, Germany. With the then calibrated model IPS-SPREADS (Infestation Pattern Simulation Supporting PREdisposition Assessment DetailS), we investigate the impact of different factors such as the distance between beetle source trees and the forest border on the amount of damage within the managed forest stand and test the effectiveness of different levels of sanitation felling and its point of action on reducing the amount of damaged trees. As expected, the results of the model calibration show that the direction of wind plays an important role for the occurring infestation patterns and that bark beetle energy reserve is reduced during mass outbreaks. The results of the second experiment show that the main drivers for the amount of damaged trees are the primary attractiveness and the distance to beetle source trees. Sanitation felling effectiveness is highest when performed near the beetle source trees, with considerably high felling intensities and if there is at least some distance to the managed forest. IPS-SPREADS can be used in future studies as a tool for testing further management measures (e.g., pheromone traps) or to assess the risk for bark beetle infestations of forest areas near to wind-felled or already infested trees.

Some biological traits of the parasitoid wasp Rhopalicus tutela (Hymenoptera: Pteromalidae) in spruce forests of Moscow Region, Russia

Some biological traits of Rhopalicus tutela (Walker), a parasitoid of the European spruce bark beetle Ips typographus (L.), were studied both in forests of Moscow Region, Russia, and under laboratory conditions. Females of R. tutela have mature eggs after overwintering and thus do not need additional feeding to lay eggs. Under laboratory conditions at 8 °C, the life expectancy of males is 58±44 days and that of females is 36±45 days. An increase of temperature shortens the developmental period of R. tutela, which can proceed without diapause. The duration of one generation in the laboratory at 22–24 °C is 14–16 days. In spruce forests of Moscow Region, R. tutela has two or three generations per year.