Efficacy of synthetic lures for pine bark beetle monitoring

The Scots pine (Pinus sylvestris) plantations in central Europe are currently damaged by a large-scale infestation by bark beetles (Scolytinae). Ips acuminatus and Ips sexdentatus are among the most aggressive species causing infestations of pine trees that are currently simultaneously attacked by Ips typographus. In pine plantations prone to damage, it is therefore necessary to carry out the bark beetle monitoring. One of the used methods is the pheromone bark beetle trapping using synthetic lures. The efficacy of synthetic lures differs. We tested the efficacy of commercially available lures used in the protection of pine trees. In total, we deployed 10 trap series, each consisting of traps with eight different lures and two unbaited traps (controls). Ips acuminatus and I. sexdentatus were most abundantly captured in Pheagr-IAC- and Sexowit-baited traps. Interestingly, the spruce species I. typographus was also captured and most often found in traps with Pheagr-IAC and Erosowit Tube lures. The number of captured beetles was consistent with the gradation phase of bark beetles. Our results suggest the suitability of pheromone traps for bark beetle monitoring. The use of Sexowit can be recommended especially in southwestern Moravia, where I. sexdentatus occurs in high numbers in the long run. In other parts of the Czech Republic, Pheagr-IAC alone can be used with sufficient efficacy. The use of the Erosowit Tube lure is also suitable for I. typographus and I. sexdentatus monitoring.

Fungal Communities Vectored by Ips sexdentatus in Declining Pinus sylvestris in Ukraine: Focus on Occurrence and Pathogenicity of Ophiostomatoid Species

Drought-induced stress and attacks by bark beetle Ips sexdentatus currently result in a massive dieback of Pinus sylvestris in eastern Ukraine. Limited and fragmented knowledge is available on fungi vectored by the beetle and their roles in tree dieback. The aim was to investigate the fungal community vectored by I. sexdentatus and to test the pathogenicity of potentially aggressive species to P. sylvestris. Analysis of the fungal community was accomplished by combining different methods using insect, plant, and fungal material. The material consisted of 576 beetles and 96 infested wood samples collected from six sample plots within a 300 km radius in eastern Ukraine and subjected to fungal isolations and (beetles only) direct sequencing of ITS rDNA. Pathogenicity tests were undertaken by artificially inoculating three-to-four-year-old pine saplings with fungi. For the vector test, pine logs were exposed to pre-inoculated beetles. In all, 56 fungal taxa were detected, 8 exclusively by isolation, and 13 exclusively by direct sequencing. Those included nine ophiostomatoids, five of which are newly reported as I. sexdentatus associates. Two ophiostomatoid fungi, which exhibited the highest pathogenicity, causing 100% dieback and mortality, represented genera Graphium and Leptographium. Exposure of logs to beetles resulted in ophiostomatoid infections. In conclusion, the study revealed numerous I. sexdentatus-vectored fungi, several of which include aggressive tree pathogens.

Reference Gene Selection for Normalizing Gene Expression in Ips Sexdentatus (Coleoptera: Curculionidae: Scolytinae) Under Different Experimental Conditions

Ips sexdentatus (Coleoptera: Curculionidae: Scolytinae) is one of the most destructive and economically important forest pests. A better understanding of molecular mechanisms underlying its adaptation to toxic host compounds may unleash the potential for future management of this pest. Gene expression studies could be considered as one of the key experimental approaches for such purposes. A suitable reference gene selection is fundamental for quantitative gene expression analysis and functional genomics studies in I. sexdentatus. Twelve commonly used reference genes in Coleopterans were screened under different experimental conditions to obtain accurate and reliable normalization of gene expression data. The majority of the 12 reference genes showed a relatively stable expression pattern among developmental stages, tissue-specific, and sex-specific stages; however, some variabilities were observed during varied temperature incubation. Under developmental conditions, the Tubulin beta-1 chain (β-Tubulin) was the most stable reference gene, followed by translation elongation factor (eEF2) and ribosomal protein S3 (RPS3). In sex-specific conditions, RPS3, β-Tubulin, and eEF2 were the most stable reference genes. In contrast, different sets of genes were shown higher stability in terms of expression under tissue-specific conditions, i.e., RPS3 and eEF2 in head tissue, V-ATPase-A and eEF2 in the fat body, V-ATPase-A and eEF2 in the gut. Under varied temperatures, β-Tubulin and V-ATPase-A were most stable, whereas ubiquitin (UbiQ) and V-ATPase-A displayed the highest expression stability after Juvenile Hormone III treatment. The findings were validated further using real-time quantitative reverse transcription PCR (RT-qPCR)-based target gene expression analysis. Nevertheless, the present study delivers a catalog of reference genes under varied experimental conditions for the coleopteran forest pest I. sexdentatus and paves the way for future gene expression and functional genomic studies on this species.

Evaluation of insect pest occurrence in areas of calamitous mortality of Scots pine

Pinus sylvestris is an important production tree. In recent years, there has been a sharp increase in the mortality of pine trees due to insect pests. It is obvious that some pests profit from climatic changes, increase their aggressiveness and spread to new localities. The study aimed to investigate the spectrum of more abundant insect pest species in pine plantations of Czechia. The occurrence of species and intensity of their infestation were studied at 77 localities situated in six regions. Any abundant foliophagous insect species were noticed. Bark beetles and wood-boring insects were found to be prevalent. Namely, Ips acuminatus, Ips sexdentatus, Phaenops cyanea and Sirex noctilio seem to be the most dangerous. These species are now better competitors than species previously considered as main pests. Their aggressiveness, expansion to new areas and interspecies co-occurrence are alarming. Due to the advancing climate change, pine mortality due to bark beetles and wood-boring pests will probably continue to increase.

Ips sexdentatus Mass-Trapping: Mitigation of Its Negative Effects on Saproxylic Beetles Larger Than the Target

Research Highlights: We investigated the negative effects of bark beetle mass trapping, especially non-target catches among the target’s natural enemies. Slot traps modified with mesh screen and escape windows were tested to improve their selectiveness. Background and Objectives: Two of the main natural enemies of bark beetles, Thanasimus formicarius (L.) and Temnoscheila caerulea (Olivier), are frequently trapped in high numbers in Ips sexdentatus (Böerner) pheromone traps, along with other saproxylic insects; this may lead to much larger pest populations in the successive 4–20 beetle generations. From 2016–2019, during I. sexdentatus mass-trapping in a pine forest of Tuscany (Italy), non-target catches were tallied. Trap modifications were evaluated to mitigate non-target catches, especially those concerning bark beetles’ natural enemies. Materials and Methods: A total of 25 bark-beetle slot traps were placed about 75 m apart in a pine stand infested by I. sexdentatus. Traps were baited with I. sexdentatus aggregation pheromone, whose main components are ipsenol, ipsdienol, and 2-methyl-3-buten-2-ol. Catches were collected every 10 days from March to December. In 2019, 13 traps were modified by applying a 6-mm mesh screen on top of the collection container and by providing three 60 mm × 8 mm escape windows immediately above the screen. These “modified traps” and their captures were considered separately from the 12 remaining “standard traps.” All bark beetle species were recorded, as well as all beetle species > 8 mm. Results: Overall, target catches amounted for <10% of the total beetle catches. The most-collected species was the bark beetle Orthotomicus erosus Wollaston. Trap modification allowed the escape of larger species, resulting in the reduction of the average size of caught specimens. Even though non-target catches among predators were still high, the proportion of major predators (T. formicarius and T. caerulea) to bark beetles showed a statistically significant reduction of predator catches in modified traps, an encouraging outcome. Conclusions: Trap modifications may mitigate the problem of non-target catches during mass trapping, especially reducing catches of beetle species larger than the target. However, the key is to schedule mass trapping only during those seasons when the target adults are more active than the main predator adults, thus limiting their catches and, consequently, the negative effects on pest management and biodiversity.

The condition of the epiphytic lichens of dark coniferous forest in the area of the outbreak of ips sexdentatus boern on the Maly Abakan site of Khakassky nature reserve

The study presents data on the condition of the thalli of epiphytic lichens, their occurrence and projective cover on the sample plots located in the area of the outbreak of Ips sexdentatus Boern on the Maly Abakan site of Khakassky Nature Reserve.

Natural and insecticide-free methods for protecting wood piles from bark beetles - using the example of the ash bark beetle (Hylesinus fraxini [Panzer, 1779]) on Common Ash (Fraxinus excelsior [L.])

This paper is investigating the insecticide-free protection of ash wood piles through the use of semiochemical dispensers with allochthonous kairomones to control ash bark beetle populations. For this purpose, borehole counts and brood gallery analyses were carried out on log piles of ash wood stored in the forest. Studies have shown that Hylesinus fraxini is repelled by the attractant dispenser with the substance mixture Sexowit, which was actually developed to catch Ips sexdentatus. In addition, the substance mixture has an aggregating effect on various bark beetle antagonists. This causality should be used to find a form of application to protect freshly stacked ash wood from H. fraxini infestation. A recommended form of application should be transferable to other bark beetle- and tree species and substances. In adaptation to the so-called Island Method of bark beetle traps, the wood piles of the five test variants were also arranged like islands. Commercially available Sexowit pheromone dispensers were used, which were attached to the piles. Besides a control without Sexowit dispenser there were test treatments with one, two, four and nine Sexowit dispensers.Within the scope of the investigation, effects between the tested variants could be determined and a recommended application method derived. Compared to control most effective protection of ash log piles was reached with variants treated with four or nine lures of Sexowit. In relation to control infestation was reduced by 78.1% on 4-dispenser variant Sexowit and 88.9% on 9-dispenser variant Sexowit.

A duplex ddPCR assay for simultaneously detecting Ips sexdentatus and Ips typographus (Coleoptera: Curculionidae) in bulk trap samples

Bark beetles in the family Curculionidae present a growing hazard to forests worldwide. Like native bark beetles, introduced exotic species can pose a serious threat to North American forests. Ips typographus (Boerner) and Ips sexdentatus (Linnaeus), both native to Europe, are two such pests that have caused widespread forest loss in their native ranges. International trade has led to increased interceptions of Scolytine beetles at ports of entry to the United States. Most intercepted individuals are not identified to species due to lack of expert identifiers, poor specimen quality, or incomplete taxonomy. These same problems affect identification for domestic surveys. Therefore, development of molecular methods for identification of potentially invasive Ips species is essential. Because of the need to scrutinize large numbers of beetles in an efficient manner, we describe a duplex droplet digital PCR (ddPCR) assay to identify I. typographus and I. sexdentatus simultaneously in bulk trap samples containing 500 Scolytinae specimens using a scalable, two-step DNA extraction. This ddPCR method is highly effective for processing the entire contents of beetle traps and identifying these potentially invasive species in a timely and definitive manner. We also describe a nondestructive DNA extraction technique that preserves specimens for morphological identification.