Pine Engraver Research Articles

Bottom-up population regulation of Orthotomicus erosus on irrigated and fertilized Pinus eldarica: A comprehensive field study

The Mediterranean pine engraver, Orthotomicus erosus (Wollaston), is a destructive pest that has caused a significant threat to planted pine forests worldwide through feeding on phloem, disrupting sap flow and transmitting phytopathogens. This study investigated the bottom-up effects of different irrigation and fertilization treatments on the mean numbers of O. erosus immature stages (egg, larva and pupa) and adults in the pine forest of western Tehran, Iran. A total of 72 Pinus eldarica Medw. trees were selected in Chitgar Forest Park. The experiment was arranged as a split plot in a randomized complete block design with three replications. The irrigation treatments included non-irrigation, low-irrigation (30 liters of water per month) and high-irrigation (30 liters of water per two weeks) were assigned to main plots. Moreover, fertilizers of nitrogen 100 kg/ha, superphosphate 100 kg/ha and potassium sulfate 65 kg/ha were applied in subplots. Then, the total number of O. erosus life stages was counted under the bark samples (two 10 × 10 cm bark samples) separated from the pine trees. Results showed that irrigation and fertilization significantly affected the mean number of O. erosus from egg to adult stages. Irrigation had a more pronounced effect on the pest population than fertilization. The highest number of different life stages occurred in non-irrigated pines regardless of fertilization. Moreover, fertilizer effects were influenced by irrigation, where high irrigation negatively affected superphosphate + potassium sulfate fertilized pines and significantly increased the mean numbers of different O. erosus life stages compared to low-irrigation treatment. The lowest mean number of egg (11.95 ± 0.17), larva (8.62 ± 0.21), pupa (10.38 ± 0.13) and adult (9.04 ± 0.23) per bark samples occurred in superphosphate + potassium sulfate at low-irrigation plots. Interestingly, nitrogen fertilization increased pest density compared to unfertilized trees. Furthermore, despite the low mean number of different O. erosus life stages in superphosphate + potassium sulfate treatments, the nitrogen combination increased the pest density in both low and high-irrigation plots. These findings highlighted the importance of considering the interaction between irrigation and fertilizer types in the integrated pest management program for O. erosus.

Phoretic mite assemblage of the pinyon pine beetle, Ips confusus (Curculionidae: Scolytinae), in Arizona

Mites are among the most common associates of bark beetles and they can influence the ecology and microbial composition within bark beetle-colonized trees. The pinyon pine engraver, Ips confusus is a common beetle in pinyon trees in the southwestern United States, but the mite composition associated with this beetle has been little studied. In this study, we quantify the abundance, diversity, and attachment locations of phoretic mites on Ips confusus that emerge from naturally infested trees. In total, we observed 342 beetles for mites, 95% of which had at least one mite. We collected a total of 5842 mites, representing seven families and seven species: Cercoleipus coelonotus (Cercomegistidae) Dendrolaelaps quadrisetosimilis (Digamasellidae), Ereynetes propescutulis (Ereynetidae), Iponemus confusus confusus (Tarsonemidae), Mexecheles cf. virginiensis (Cheyletidae), Proctolaelaps subcorticalis (Melicharidae), and Trichouropoda californica (Trematuridae). We calculated the average number of mites per beetle to be 18, with a maximum of 147 mites on a single beetle. The vast majority of mites (98% of total abundance) was represented by three species (I. c. confusus, D. quadrisetosimilis, and T. californica). Attachment locations on the beetle varied across mite species, with mite species exhibiting a preference for specific locations. Mite abundances on emerging host beetles varied over time, with some species occurring mostly on early-emerging beetles, while others occurred on later emerging beetles.

Acetophenone and Green Leaf Volatiles Do Not Enhance the Efficacy of Verbenone for Inhibiting Attraction of Ips pini (Coleoptera: Curculionidae) to Pheromone-baited Traps in Northern Arizona.

We assessed attraction of pine engraver, Ips pini (Say) (Coleoptera: Curculionidae; Scolytinae), to pheromone-baited funnel traps treated with repellent semiochemicals in ponderosa pine, Pinus ponderosa var. scopulorum Engelm., forests in northern Arizona. Treatments included: 1) baited control (B, ipsdienol + lanierone), 2) 70 g of SPLAT Verb (a flowable, biodegradable formulation containing 10% verbenone, ISCA Technologies Inc., Riverside, CA, USA) + B, 3) 70 g of SPLAT Verb + (E)-2-hexen-1-ol+(Z)-2-hexen-1-ol + acetophenone + B, 4) 7.84-g verbenone pouch (Product #3413, Synergy Semiochemicals Corp., Delta, British Columbia, Canada) + B, and 5) 7.84-g verbenone pouch + (E)-2-hexen-1-ol+(Z)-2-hexen-1-ol + acetophenone + B. In total, 472 I. pini were collected. Trap catches were highest in baited traps and declined significantly with the addition of both formulations of verbenone. Traps treated with SPLAT Verb caught significantly fewer I. pini and male I. pini than those treated with verbenone pouches. The addition of (E)-2-hexen-1-ol+(Z)-2-hexen-1-ol + acetophenone to SPLAT Verb and the verbenone pouch had no effect on trap catch. Verbenone has potential as an effective tool for protecting P. ponderosa trees and slash from I. pini in northern Arizona, but the addition of (E)-2-hexen-1-ol+(Z)-2-hexen-1-ol + acetophenone to verbenone is unwarranted.

Monitoring studies of habitats of rare species and tree-dwelling insects in the Emerald Network sites

The pine stands of the Vyshcha Dubechnia State Forestry Enterprise in the Emerald Network sites Kyivske Reservoir UA0000094, Kyivske Podesennia UA0000233, Mizhrichynsky Regional Landscape Park UA0000047 are an important reserve that includes species and habitats of insects that are subject to protection. Most of the existing studies in this area were designed to identify and describe individual habitats, while xylophagous insects were not considered. The purpose of the research was to identify rare and endangered species of tree-dwelling insects in unique natural complexes. The research methods included reconnaissance surveys to determine the species composition of insects and their density. The surveys were conducted in 2020-2022, covering 33 plots with a total area of 50.5 hectares. The monitoring was performed through regular surveys of the territories, during which rare species listed in the Red Data Book of Ukraine and the Berne Convention resolution were identified. A desktop analysis of forestry materials was conducted. Rare species of insects subject to protection are encountered, but outside the areas where monitoring observations were conducted. These are mainly water, marsh, meadow lands, etc. Accounting for stem pests such as Scolytinae (small pine engraver Tomicus minor and pine shoot beetle Tomicus piniperda), Buprestidae (steelblue jewel beetle Phaenops cyanea) and Cerambycidae (pine sawyer Monochamus galloprovincialis and timberman beetle Acanthocinus aedilis). The identified populations of xylophagous insects are described as low to medium density, occurring only on very weakened trees, and species such as Chrysobothris affinis, Cerambyx scopolii, and Scolytus ratzeburgi are rare. The results of the study will serve as an informational base for the development of regional biodiversity conservation programs and the implementation of mechanisms for the sustainable use of forest resources

Ophiostomatales Associated with Mediterranean Pine Engraver, Orthotomicus erosus (Coleoptera, Curculionidae) in Dalmatia, Croatia

Mediterranean pine engraver, Orthotomicus erosus was never considered as a significant pest in Croatia and did not appear in high population densities until 2017, when it reached outbreak level in Aleppo pine stands. The beetle was first detected in Marjan Forest Park, Split, and was soon recorded in other parts of the Dalmatian coast. Soon after the outbreak occurred, we observed that all of the attacked trees exhibit severe blue staining in the sapwood which indicated fungal infection caused by the Ophiostomatales group of fungi. This raised the need to investigate their relationship with O. erosus and the pine decline, and the main aim of this study was to isolate and identify them. Isolates were obtained from adult O. erosus beetles, their galleries, and blue-stained sapwood, and identified according to the morphological characteristics and DNA sequencing. A total of six Ophiostomatales (Ophiostoma ips, O. piceae, Graphilbum cf. rectangulosporium, O. floccosum, Sporothrix pseudoabietina and Ceratocystiopsis cf. minuta) were identified in the study. This is the first record of Ophiostomatales as organisms associated with the pest O. erosus and pine species in Croatia.

Tree Mortality following Thinning and Prescribed Burning in Central Oregon, U.S.

We examined causes and levels of tree mortality one year after thinning and prescribed burning was completed in ponderosa pine (Pinus ponderosa Dougl. ex Laws.) forests at Pringle Falls Experimental Forest, Oregon, U.S. Four blocks of five experimental units (N = 20) were established. One of each of five treatments was assigned to each experimental unit in each block. Treatments included thinning from below to the upper management zone (UMZ) for the dominant plant association based on stand density index values for ponderosa pine followed by mastication and prescribed burning: (1) 50% UMZ (low density stand), (2) 75% UMZ (medium density stand), (3) 75% UMZ Gap, which involved a regeneration cut, (4) 100% UMZ (high density stand), and (5) an untreated control (high density stand). Experimental units were thinned in 2011 (block 4), 2012 (block 2), and 2013 (blocks 1 and 3); masticated within one year; and prescribed burned two years after thinning (2013–2015). A total of 395,053 trees was inventoried, of which 1.1% (4436) died. Significantly higher levels of tree mortality occurred on 100 UMZ (3.1%) than the untreated control (0.05%). Mortality was attributed to prescribed fire (2706), several species of bark beetles (Coleoptera: Curculionidae) (1592), unknown factors (136), windfall (1 tree), and western gall rust (1 tree). Among bark beetles, tree mortality was attributed to western pine beetle (Dendroctonus brevicomis LeConte) (881 trees), pine engraver (Ips pini (Say)) (385 trees), fir engraver (Scolytus ventralis LeConte) (304 trees), mountain pine beetle (D. ponderosae Hopkins) (20 trees), Ips emarginatus (LeConte) (1 tree), and Pityogenes spp. (1 tree).

Exposure to Fungal Volatiles Can Influence Volatile Emissions From Other Ophiostomatoid Fungi.

Fungal volatile organic compounds (FVOCs) can act as intra- and inter-kingdom communication signals that influence the growth and behaviors of organisms involved in antagonistic or mutualistic relationships with fungi. There is growing evidence suggesting that FVOCs can mediate interactions between organisms within and across different ecological niches. Bark beetles have established mutualistic relationships with ophiostomatoid fungi which can serve as a food source and condition host plant tissues for developing beetle larvae. While the profiles (both composition and concentrations) of volatile emission from ophiostomatoid fungi can be influenced by abiotic factors, whether emissions from a given fungal species can be influenced by those from another is still unknown. Here, we analyzed FVOCs emitted from the two ophiostomatoid fungi, Grosmannia clavigera and Ophiostoma ips, associated with mountain pine beetle and pine engraver beetle, respectively, when each fungus was growing alone or in a shared headspace. We used two isolates of each fungus species. Overall, we detected a total of eight volatiles in both G. clavigera alone or in combination with O. ips including acetoin, ethyl acetate, cis-grandisol, isoamyl alcohol, isobutanol, 2-methyl-1-butanol, phenethyl acetate, and phenethyl alcohol. The profiles of volatiles emitted differed between the two fungal species but not between the two isolates of the same fungus. Six compounds were common between the species, whereas two compounds were detected only when G. clavigera was present. Moreover, the majority of volatiles were detected less frequently and at lower concentrations when the two fungi were grown together in a shared headspace. These results are likely due to reduced volatile emissions from O. ips in the presence of G. clavigera. However, changes in the profiles of fungal volatiles did not correspond with the observed changes in the growth of either species. Overall, these results suggest that the similarities in fungal volatiles among different species of fungi may reflect a common ecological niche and that the differences may correspond to species-specific adaptation to their respective host beetles or genetic factors.

Genome Analysis and Genomic Comparison of the Novel Species Arthrobacter ipsi Reveal Its Potential Protective Role in Its Bark Beetle Host.

The pine engraver beetle, Ips acuminatus Gyll, is a bark beetle that causes important damages in Scots pine (Pinus sylvestris) forests and plantations. As almost all higher organisms, Ips acuminatus harbours a microbiome, although the role of most members of its microbiome is not well understood. As part of a work in which we analysed the bacterial diversity associated to Ips acuminatus, we isolated the strain Arthrobacter sp. IA7. In order to study its potential role within the bark beetle holobiont, we sequenced and explored its genome and performed a pan-genome analysis of the genus Arthrobacter, showing specific genes of strain IA7 that might be related with its particular role in its niche. Based on these investigations, we suggest several potential roles of the bacterium within the beetle. Analysis of genes related to secondary metabolism indicated potential antifungal capability, confirmed by the inhibition of several entomopathogenic fungal strains (Metarhizium anisopliae CCF0966, Lecanicillium muscarium CCF6041, L. muscarium CCF3297, Isaria fumosorosea CCF4401, I. farinosa CCF4808, Beauveria bassiana CCF4422 and B. brongniartii CCF1547). Phylogenetic analyses of the 16S rRNA gene, six concatenated housekeeping genes (tuf-secY-rpoB-recA-fusA-atpD) and genome sequences indicated that strain IA7 is closely related to A. globiformis NBRC 12137T but forms a new species within the genus Arthrobacter; this was confirmed by digital DNA-DNA hybridization (37.10%) and average nucleotide identity (ANIb) (88.9%). Based on phenotypic and genotypic features, we propose strain IA7T as the novel species Arthrobacter ipsi sp. nov. (type strain IA7T = CECT 30100T = LMG 31782T) and suggest its protective role for its host.

Verbenone Inhibits Attraction of Ips pini (Coleoptera: Curculionidae) to Pheromone-Baited Traps in Northern Arizona.

Recent outbreaks of engraver beetles, Ips spp. De Geer (Coleoptera: Curculionidae; Scolytinae), in ponderosa pine, Pinus ponderosa var. scopulorum Engelm. (Pinales: Pinaceae), forests of northern Arizona have resulted in widespread tree mortality. Current treatment options, such as spraying individual P. ponderosa with insecticides or deep watering of P. ponderosa in urban and periurban settings, are limited in applicability and scale. Thinning stands to increase tree vigor is also recommended, but appropriate timing is crucial. Antiaggregation pheromones, widely used to protect high-value trees or areas against attacks by several species of Dendroctonus Erichson (Coleoptera: Curculionidae; Scolytinae), would provide a feasible alternative with less environmental impacts than current treatments. We evaluated the efficacy of the antiaggregation pheromone verbenone (4,6,6-trimethylbicyclo[3.1.1]hept-3-en-2-one) in reducing attraction of pine engraver, I. pini (Say), to funnel traps baited with their aggregation pheromone in two trapping assays. Treatments included 1) unbaited control, 2) aggregation pheromone (bait), 3) bait with verbenone deployed from a pouch, and 4) bait with verbenone deployed from a flowable and biodegradable formulation (SPLAT Verb, ISCA Technologies Inc., Riverside, CA). Unbaited traps caught no beetles. In both assays, baited traps caught significantly more I. pini than traps with either formulation of verbenone, and no significant difference was observed between the verbenone pouch and SPLAT Verb. In the second assay, we also examined responses of Temnochila chlorodia (Mannerheim) (Coleoptera: Trogositidae), a common bark beetle predator. Traps containing verbenone pouches caught significantly fewer T. chlorodia than the baited control and SPLAT Verb treatments. We conclude that verbenone shows promise for reducing tree mortality from I. pini.

Impacts of mountain pine beetle outbreaks on lodgepole pine forests in the Intermountain West, U.S., 2004–2019

Mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae), is the most important forest insect in western North America. We determined causes and rates of tree mortality and changes in forest structure and composition associated with D. ponderosae outbreaks in the Intermountain West, U.S. during 2004–2019 based on a network of 125 0.081-ha circular plots installed in Colorado, Idaho, Montana, Utah and Wyoming. Incipient populations of D. ponderosae began in 2004; peaked in 2007; and returned to endemic levels in 2011 in Idaho, Montana, Utah and Wyoming. In Colorado, incipient populations began in 2004; peaked in 2009; and returned to endemic levels in 2012. A total of 5107 trees died, 98.6% were lodgepole pine, Pinus contorta Dougl. ex Loud. Fifteen contributing factors were identified, including (in order of importance, highest to lowest) D. ponderosae, unknown causes, pine engraver, Ips pini (Say), wind, breakage and/or adjacent tree fall, Pityogenes knechteli Swaine/Pityopthorus confertus Swaine, suppression, spruce beetle, Dendroctonus rufipennis (Kirby), root disease, western balsam bark beetle, Dryocoetes confusus (Swain), lodgepole pine dwarf mistletoe, Arceuthobium americanum Nutt. ex. Engelm., stem diseases, woodborers, North American porcupine, Erethizon dorsatum (L.), mule deer, Odocoileus hemionus (Rafinesque), and lodgepole pine beetle, Dendroctonus murrayanae Hopkins. Most tree mortality (68.8%) was attributed solely to D. ponderosae, although D. ponderosae also occurred in association with other contributing factors. Overall, significant reductions in mean dbh (by 5.3%), mean quadratic mean diameter (by 8.6%), mean tree height (by 15.9%), mean number of trees (by 40.8%), mean basal area (by 52.9%), and mean stand density index (SDI) (by 51.8%) were observed. Significant reductions in tree density were observed in all diameter classes, except the smallest (midpoint = 10 cm, 5-cm classes). Significant increases in the mean number of snags (by 1324.7%) were observed, and most snags remain standing (71.3%). Pinus contorta remains the dominant tree species, and while significant increases in the number of subalpine fir, Abies lasiocarpa (Hooker) Nuttall, seedlings and saplings were observed, a long-term shift in tree composition is unlikely. Tree mortality (number of trees killed) was positively correlated with the initial number of live trees, basal area of live trees, SDI, and aspect, but not slope or elevation. The implications of these and other results to recovery and management of P. contorta forests in the Intermountain West are discussed.

Pine engraver beetle Ips acuminatus as a potential vector of Sphaeropsis sapinea

The pine engraver beetle Ips acuminatus Gyll. is a potential vector of the Sphaeropsis tip blight pathogen according to Leach’s postulates. The specimens of I. acuminatus were associated with numerous fungi species, namely Sphaeropsis sapinea (Fr.) Dyko & B. Sutton and ophiostomatoid species. The association between opportunistic pathogen S. sapinea and I. acuminatus has been confirmed for 62.9 % of all branches (44 % of needle samples and 82 % of wood samples). The presence of S. sapinea in the galleries and on the surface of the beetle indicates that I. acuminatus may transport the pathogen and later introduce it into healthy trees. The bark beetle can transfer pathogenic fungus during maturation feeding on the shoots of healthy pine crowns and into the branches during making galleries.

Parameters of Pinus sylvestris health condition and Ips acuminatus population in pure and mixed stands of Sumy region

Outbreaks of bark beetles have increased in recent years in various regions. Pine engraver beetle (Ips acuminatus (Gyllenhal, 1827); Coleoptera: Curculionidae: Scolytinae) is most common in the pine forests of many European countries. Research on its biology and spread carried out in different natural conditions, phases of pest outbreak and considered various parameters to characterize the population of the pest and forest health condition.
 The aim of the research was to compare the health condition of Scots pine stands and population parameters of I. acuminatus in its two generations in pure and mixed stands in Polissya and Forest-steppe parts of Sumy region. Research was carried out in 2017 in the pure Scots pine stands and mixed stands with Scots pine and other forest species in Polissya (State Enterprise "Seredyno-Budsky Agroforest Economy"; State Enterprise "Seredyno-Budsky Forest Economy") and Forest-steppe parts (State Enterprise "Velykopysarivske Agroforest Economy"; State Enterprise "Okhtyrske Forest Economy") of Sumy region at 26 sample plots. In sample plots, parameters of forest health condition and bark beetle population were assessed in June and in September, after completion of development of spring and summer generation of I. acuminatus. 
 By most of the parameters assessed, significant differences between sample plots in Forest-Steppe and Polissya parts of Sumy region were not found. In pure Scots pine stands the mean area of bark beetles’ foci and bark beetles’ production were larger in Forest-steppe in June, and the density of Ips acuminatus nuptial chambers in June and September. 
 In pure Scots pine stands the area of I. acuminatus focus, the number of colonized trees, the proportion of recently died trees, health condition indices, the density of egg galleries and nuptial chambers as well as young beetle’s production increased from June to September. In mixed stands the focus area, the number of colonized trees and health condition index increased insignificantly, and population parameters of I. acuminatus decreased from June to September. Pure Scots pine stands changed the health condition from "severely weakened" to "drying up" in three months, and mixed ones remained in the "weakened" category.
 In pure pine stands, the density of egg galleries and beetles of the young generation increased for three months from the lower limit of a moderate level to a high level, the density of nuptial chambers – from low to a high level. In mixed stands, all population parameters of I. acuminatus correspond to a low population level. The parameters characterizing the investigated foci of I. acuminatus in the Sumy region significantly correlated with the participation of pine in the stand composition, and in September the correlation is closer than in June. The data obtained indicate the feasibility of creating predominantly mixed pine stands.

Interactions between southern Ips bark beetle outbreaks, prescribed fire, and loblolly pine (Pinus taeda L.) mortality

The southeastern U.S. is considered the “wood-basket” of the world where loblolly pine (Pinus taeda L.) plantations provide tremendous ecological and economic benefits to the region. These plantations are susceptible to various natural and anthropogenic abiotic and biotic stressors and disturbances. The southern pine engravers, Ips avulsus (Eichhoff), I. calligraphus (Germar), and I. grandicollis (Eichhoff), are considered secondary colonizers of stressed, damaged, and dying loblolly pines. However, they may undergo outbreaks and colonize live pine hosts if environmental conditions cause physiological stress to trees. In 2016, >230 concurrent Ips infestations >2 ha in size were documented in Georgia, U.S., reportedly due to severe drought. In these forests, prescribed burning is often conducted every 2–3 years to reduce fuel-loads, improve wildlife habitat, and manage understory vegetation. However, the effects of low-severity prescribed fire on active southern Ips infestations are unknown; fire may exacerbate or alleviate beetle outbreaks. Our objectives were to: (1) compare Ips infestations between burned and unburned sites to determine the short-term effects of prescribed fire on loblolly pine mortality; and (2) determine which site-level and tree-level variables were the best predictors of short-term levels of tree mortality. We monitored 838 pines on ten sites for eight months following prescribed fire in spring 2017. Overall, 69 (8%) trees died with 3.6 times higher tree mortality on unburned sites, and a higher probability of survival on burned sites. At the site-level, binomial logistic regression models including treatment (unburned versus burned) and time since burn were the best predictors of loblolly pine mortality. At the tree-level, model selection showed that treatment, crown mortality level (1–5), Ips activity level (none, low, medium, and high), and tree diameter provided the best predictions of mortality. Prescribed burning may thus help alleviate pest pressure and increase tree resilience in loblolly pine forests in the southeastern U.S.

Outbreak of Orthotomicus erosus (Coleoptera, Curculionidae) on Aleppo Pine in the Mediterranean Region in Croatia

Background and Purpose: Orthotomicus erosus, Mediterranean pine engraver, is widely distributed across the Mediterranean and southern Europe, Asia and North Africa. It is considered as secondary pest found on recently dead or felled trees, but can also attack weakened living trees. In high population levels this species can attack healthy trees and cause their dieback. Severe outbreaks occur after dry periods, or after fire in adjoining stands in warmer parts of the Mediterranean region, while this scenario has never happened in Croatia up to now. Bark beetles are important forest pests which have already been researched and discussed in relation to climate change, indicating that the predicted increase in temperature would lead to higher survival rates and faster development, thus directly influencing their population dynamics. Increase in temperature may stimulate changes in insects’ rate of development, voltinism, population density, size, genetic composition, extent of host plant exploitation, longitudinal and latitudinal distribution. Since climate conditions might have changed in the last few years as predicted in the Mediterranean region, the aim of our research is to document the first outbreak with high population levels of O. erosus in Croatia. Materials and Methods: The extent of dieback was evaluated by counting trees with dieback symptoms on diagonal transects plotted through each of 33 forest management sections of Marjan Forest Park (Split). Trunk sections from several trees with early stage symptoms were collected for further laboratory analysis, which consisted of incubation phase and subsequent morphological identification. During regular yearly surveys in forests of Croatia, the pest was observed on several sites and damages were recorded for both years 2017 and 2018. The records were entered into a map using QGIS version 3.2.1-Bonn. Spatial data was downloaded from DIVA-GIS server. Monitoring efforts were initiated in affected areas where 13 flight barrier pheromone traps (Theyson®) equipped with pheromone lure Erosowit® (Witasek, Austria) were set-up in late March in state-owned and privately owned forests across Dalmatia. Catches in the traps were collected and O. erosus adults were counted on a weekly basis in order to identify the abundance of the pest in monitored sites, as well as to obtain the first information about population dynamics and to assess voltinism. Results: On-site survey and the evaluation of dieback extent included sampling of 5% of all trees in Marjan Forest Park ,and the results showed that 23% of all trees in the forest park were affected by dieback symptoms. Visual examination of trunks, branches and bark showed symptoms of bark beetle infestation, while preliminary on-site examination of the observed adults pointed out to O. erosus. After two weeks in controlled conditions, bark beetle adults started to emerge from trunk sections which were placed in several mesh cages for incubation. Morphological identification by using stereomicroscope and the key for European bark beetles resulted in identification of O. erosus species. Over the course of the year 2017 one more site was reported to be infested with O. erosus, and eight additional sites were reported over the course of year 2018. In total, 446 ha were reported as infested, varying in intensity, in several different management units of state-owned and privately owned forests. The total number of trapped beetles in pheromone traps varied largely among sites. Our data indicate that several generations (at least 5 generations per year) were present in the year 2018. Conclusions: Sudden surge in observed damages, as well as the number of beetles trapped during monitoring, in years 2017 and 2018 throughout Aleppo pine forests in Dalmatia are the first record of O. erosus outbreak in Croatia. O. erosus is native to Croatia and so far it has been considered only as a minor pest whose outbreaks have never been recorded. Drought intensity and frequency and aridification trends in the research area (Dalmatia, Croatia) cause cumulative stress to trees and have increased O. erosus occurrence. O. erosus is expected to exhibit increased voltinism, better overwintering performance and earlier spring flights. Our first results confirm this epidemic stage of O. erosus with high abundances in Dalmatia in 2018 and at least 5 generations per year, which alter the population level of this pest. Finally, with high dispersal abilities of O. erosus through active flight and easy transportation with infested material (logs and branches with bark), O. erosus has the potential to become an important forest pest in Croatia. Thus, extensive studies on its biology, ecology, natural enemies and interaction with ophiostomatoid fungal species are needed in order to predict further spread and suggest viable and effective management measures.

Ophiostomatoid fungi can emit the bark beetle pheromone verbenone and other semiochemicals in media amended with various pine chemicals and beetle-released compounds

Abstract Fungal volatile compounds can mediate fungal-insect interactions. Whether fungi can emit insect pheromones and how volatile chemicals change in response to chemicals the fungi naturally encounter is poorly understood. We analyzed volatiles emitted by Grosmannia clavigera (symbiont of the mountain pine beetle) and Ophiostoma ips (symbiont of the pine engraver beetle) growing in liquid media amended with compounds that the fungi naturally encounter: (−)-α-pinene, (+)-α-pinene, (−)-trans-verbenol, verbenone, or ipsdienol. Nine volatile compounds were identified among the fungal and amendment treatments. Volatiles qualitatively and quantitatively differed between fungal species and among amendment treatments. The bark beetle anti-aggregation pheromone (−)-verbenone was detected from both fungi growing in (−)-trans-verbenol-amended media. G. clavigera and O. ips can emit beetle pheromones and other beetle semiochemicals, suggesting that ophiostomatoid fungi could contribute to the chemical ecology of bark beetles. However, such contributions could be modulated by the presence of other environmental chemicals.

A comparative characteristic of fungal communities associated with Ips acuminatus in different regions of Ukraine

Pine bark beetles are typically associated with complexes of fungi that could reveal different functional interaction. Thus, previously nonaggressive bark beetle Ips acuminatus is considering now to be among the most serious pests of pine forest in Ukraine and other European countries and vectored fungal community is very important to assess total harm of this bark beetle. The aim of this study was to reveal the vectored fungal community associated with the pine engraver beetle, I. acuminatus with special emphasis on pathogenic fungi for further evaluation of harm bark-beetle - fungi association for Ukrainian forest.
 In total, 288 adult beetles were collected from Scots pine trees at six different sites through Ukraine. DNA sequencing as fungal culturing from all beetles resulted in 1681 isolates and amplicons representing 42 fungal taxa. NCBI BLAST search revealed that the overall fungal community was composed of 94 species, of which 80.85% were Ascomycota, followed by Basidiomycota and unidentified fungal group, which accounted for 10.6% and 8.5 % of the total sequences, respectively. Among these, the most commonly detected fungi for pooling dataset were Sphaeropsis sapinea (23.6%), Cladosporium pini-ponderosae (19.44%), Ophiostoma ips (19.1%), Ophiostoma canum (19.1%) and Cladobotryum mycophilum (18.06%). In the pooled dataset of isolates and amplicons for each site, Shannon diversity indices ranged between 1.9 and 2.9 while Simpson diversity index varied between 0.69 and 0.89 indicating rich species diversity.
 In total twelve ophiostomatoid species were detected. All ophiostomatoid fungi were showing varying degrees of virulence and O. minus was the most aggressive fungus in previous studies. It is concluded that I. acuminatus vectors a species-rich fungal community including pathogens such as ophiostomatoid fungi, Sphaeropsis sapinea, different needle pathogens and wood decay fungi that seems to be very important for the assessment of threat of I. acuminatus to the pine forest in Ukraine.

An IDS-Type Sesquiterpene Synthase Produces the Pheromone Precursor (Z)-α-Bisabolene in Nezara viridula.

Insects use a wide range of structurally diverse pheromones for intra-specific communication. Compounds in the class of terpenes are emitted as sex, aggregation, alarm, or trail pheromones. Despite the common occurrence of terpene pheromones in different insect lineages, their origin from dietary host plant precursors or de novo biosynthetic pathways often remains unknown. Several stink bugs (Hemiptera: Pentatomidae) release bisabolene-type sesquiterpenes for aggregation and mating. Here we provide evidence for de novo biosynthesis of the sex pheromone trans-/cis-(Z)-α-bisabolene epoxide of the Southern green stink bug, Nezara viridula. We show that an enzyme (NvTPS) related to isoprenyl diphosphate synthases (IDSs) of the core terpene metabolic pathway functions as a terpene synthase (TPS), which converts the general intermediate (E,E)-farnesyl diphosphate (FPP) to the putative pheromone precursor (+)-(S,Z)-α-bisabolene in vitro and in protein lysates. A second identified IDS-type protein (NvFPPS) makes the TPS substrate (E,E)-FPP and functions as a bona fide FPP synthase. NvTPS is highly expressed in male epidermal tissue associated with the cuticle of ventral sternites, which is in agreement with the male specific release of the pheromone from glandular cells in this tissue. Our study supports findings of the function of similar TPS enzymes in the biosynthesis of aggregation pheromones from the pine engraver beetle Ips pini, the striped flea beetle Phyllotreta striolata, and the harlequin bug Murgantia histrionica, and hence provides growing evidence for the evolution of terpene de novo biosynthesis by IDS-type TPS families in insects.

ПОШИРЕННЯ ОСЕРЕДКІВ МАСОВОГО РОЗМНОЖЕННЯ КОРОЇДІВ У СОСНОВИХ НАСАДЖЕННЯХ РІВНЕНСЬКОГО ПОЛІССЯ

Досліджено особливості поширення усихання сосни звичайної (Pinus sylvestris L.) в осередках верхівкового (Ips acuminatus (Gyllenhal, 1827)) та шестизубчастого (Ips sexdentatus (Boerner, 1767)) короїдів (Curculionidae, Scolytinae) у лісах Державного підприємства "Володимирецьке лісове господарство" Рівненського обласного управління лісового та мисливського господарства. Встановлено, що площа всихаючих соснових насаджень лісгоспу впродовж 2017 р. збільшилася і перевищила 2000 га на кінець року. Частка площі осередків короїдів у площі всихаючих соснових насаджень зросла від 3,1 % у першому кварталі до 75 % у другому, до 90,8 % у третьому та до 100 % у четвертому. Виявлено, що чисті соснові насадження становлять 50,3 % від площі всіх насаджень лісгоспу, в котрих сосна є головною породою, і 64,6 % від площі осередків короїдів. З'ясовано, що у віковій структурі соснових насаджень лісгоспу на V-VIII класи віку припадає 61,1 % від площі всіх соснових насаджень і 90,9 % від площі осередків короїдів. Розраховано, що середня зважена повнота соснових насаджень лісгоспу становить 0,73 одиниці, а в осередках короїдів – 0,7 одиниці. Статистично підтверджено приуроченість осередків короїдів до чистих середньоповнотних соснових насаджень V-VIII класів віку.

Impact ofBeauveria bassiana(Ascomycota: Hypocreales) on the Small Southern Pine Engraver (Coleoptera: Scolytidae) in a Loblolly Pine Bolt Assay1

Abstract The small southern pine engraver, Ips avulsus Eichhoff (Coleoptera: Scolytidae), is one member of a guild of southern pine bark beetles that causes millions of dollars of losses to southern U.S. pine forests annually. Our objective was to determine the impact of a commercial preparation of the entomopathogenic fungus Beauveria bassiana (Balsamo-Crivelli) Vuillemin (Ascomycota: Hypocreales) in protecting pine host plant tissue from colonization and damage by I. avulsus and on the B. bassiana–induced mortality of I. avulsus adults during the first 2 wk of host attack. The field trials were conducted in the Kisatchie National Forest (Rapides Parish, LA) using a small-bolt technique. Results showed that the I. avulsus adults successfully colonized both the B. bassiana–treated bolts and the control bolts within the first week of field exposure. Although the formulation did not protect bolts from attack, it caused significantly higher mortality of I. avulsus adults in B. bassiana–treated bolts than in ...

Pine Engravers Carry Bacterial Communities Whose Members Reduce Concentrations of Host Monoterpenes With Variable Degrees of Redundancy, Specificity, and Capability.

Bark beetles are eruptive forest insects that have the potential to cause landscape level mortality to conifer forests. The pine engraver, Ips pini (Say) (Coleoptera: Curculionidae), is the predominant pest of mature red pine (Pinus resinosa Aiton) plantations throughout the Great Lakes region of North America. Pine engraver attack elicits a localized response by host trees in which concentrations of terpenes rapidly exceed the tolerance levels of beetles and their fungal associates. We considered how bacterial associates degrade these toxins from the perspective of the symbiont communities of individual beetles. We demonstrate that 1) most pine engravers harbor bacterial communities that reduce monoterpene concentrations in vivo; 2) several individual bacterial isolates can reduce monoterpenes even at high concentrations; and 3) bacteria isolated from pine engravers are similar to those found in other bark beetles. Bacteria isolated from pine engravers decreased concentrations of (-)-α-pinene, myrcene, and 3-carene. Most beetles carried at least one bacterial isolate that reduced concentrations of at least one monoterpene. Different bacteria vary in the uppermost concentrations at which they can degrade monoterpenes. The community of bacteria associated with an individual beetle appears to have some manner of functional redundancy that could collectively increase the likelihood of successful host colonization.