Special Issue "Forest Pathology and Entomology"

A special issue of Forests (ISSN 1999-4907). This special issue belongs to the section "Forest Ecology and Management".

Deadline for manuscript submissions: closed (30 June 2021).

Special Issue Editors

Prof. Dr. Salvatore Moricca
E-Mail Website
Guest Editor
Department of Agricultural, Food, Environmental and Forestry Science and Technology (DAGRI), Plant Pathology and Entomology Section, University of Florence
Interests: Tree Pathology; Ecology of Invasive Species; Quarantine Organisms; Climate Change Impact; Fungal Endophytes; Rust Fungi; Oomycetes; Plant Protection; Biological Control
Prof. Dr. Tiziana Panzavolta
E-Mail Website
Guest Editor
Department of Agricultural, Food, Environmental and Forestry Science and Technology (DAGRI), Plant Pathology and Entomology Section, University of Florence
Interests: Invasive Insect Pests; Bark-Beetles; Forest Entomology

Special Issue Information

Dear Colleauges,

Forest protection has now become an important global priority. The arrival of new diseases and pests in uncontaminated territories and the resurgence of old, known agents of damage pose serious threats to trees in natural ecosystems as well as in urban forests, impacting ecosystem services. Climate change further exacerbates the problem, weakening forest trees and creating conditions for the range expansion of invasive diseases and pests. Furthermore, the growing trade of seedlings and other propagation material (seeds, cuttings, etc.) is boosting the spread of plant and animal parasites, seriously compromising forest and ornamental nursery activities. With the globalization of trade, the development of diagnostic tools for the early detection of latent pathogens and pests has become crucial. In this context, forest pathology and entomology have become more relevant than ever. We encourage studies from all these fields, including monitoring, epidemiology, ecology, diagnostics, and pest and disease management and control to contribute to this Special Issue to promote the dissemination of knowledge in forest protection for the preservation of structure, diversity, and resilience of natural and urban ecosystems.

Prof. Dr. Salvatore Moricca
Prof. Dr. Tiziana Panzavolta
Guest Editors

Manuscript Submission Information

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Keywords

  • Disease and pest outbreaks
  • Plant health
  • Disturbances
  • Global warming
  • Biodiversity
  • Ecosystem services
  • Forest management

Published Papers (17 papers)

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Research

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Article
Molecular-Based Reappraisal of a Historical Record of Dothistroma Needle Blight in the Centre of the Mediterranean Region
Forests 2021, 12(8), 983; https://doi.org/10.3390/f12080983 - 24 Jul 2021
Viewed by 251
Abstract
In this work, we rechecked, using species-specific Loop mediated isothermal AMPlification (LAMP) diagnostic assays followed by sequencing of fungal isolates at the beta-2-tubulin (tub2) gene region, a historical and never confirmed report of Dothistroma needle blight (DNB) in the introduced Monterey pine ( [...] Read more.
In this work, we rechecked, using species-specific Loop mediated isothermal AMPlification (LAMP) diagnostic assays followed by sequencing of fungal isolates at the beta-2-tubulin (tub2) gene region, a historical and never confirmed report of Dothistroma needle blight (DNB) in the introduced Monterey pine (Pinus radiata D. Don) in the mountains in the extreme tip of southern Italy. The report dates back to the mid-1970s, and predates the molecular-based taxonomic revision of the genus Dothistroma that defined the species accepted today. In the fall of 2019, symptomatic needles of Monterey pine and Corsican pine (Pinus nigra subsp. laricio (Poir.) Palib. ex Maire) were sampled in the area of the first finding. The applied diagnostic methods revealed the presence of Dothistroma septosporum (Dorogin) M. Morelet on both pine species. In this way, we: (i) confirmed the presence of the disease; (ii) clarified the taxonomic identity of the causal agent now occurring at that site; (iii) validated the species-specific LAMP diagnostic protocol we recently developed for Dothistroma for use on a portable field instrument, and (iv) showed that the pathogen now also attacks the native P. nigra subsp. laricio, a species particularly susceptible to the disease, indigenous to the mountains of Calabria, which is one of the very few areas where the species’ genetic resources are conserved. Comparative genetic analysis of the rare populations of D. septosporum found in the central Mediterranean region and in the native range of P. nigra subsp. laricio could help to clarify the history of the spread of the pathogen in southern Europe and better evaluate the risk it poses to the conservation of native pine species. Full article
(This article belongs to the Special Issue Forest Pathology and Entomology)
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Article
Inferences on the Susceptibility of Wood of Different Tree Species to Heterobasidion annosum Sensu Lato Primary Infections and on the Range of Pathogen Spores Dispersal
Forests 2021, 12(7), 854; https://doi.org/10.3390/f12070854 - 28 Jun 2021
Viewed by 398
Abstract
Stumps play a pivotal role in the epidemiology of the fungal forest pathogens Heterobasidion spp. because they are the main courts of primary airborne infections. The aims of this study were (i) to determine the susceptibility of seven tree species (i.e., Larix sibirica [...] Read more.
Stumps play a pivotal role in the epidemiology of the fungal forest pathogens Heterobasidion spp. because they are the main courts of primary airborne infections. The aims of this study were (i) to determine the susceptibility of seven tree species (i.e., Larix sibirica, Picea abies, Picea sitchensis, Pinus contorta, Pinus strobus, Pinus sylvestris and Pseudotsuga menziesii) to primary infection by H. annosum and H. parviporum through comparative inoculation experiments of conidia on wood discs in controlled conditions; (ii) to compare the susceptibility of wood discs of the same tree species to natural airborne infections in two Latvian Norway spruce forest stands infested either by H. annosum or H. parviporum; (iii) to explore the rates of infection of wood discs at increasing distances from spore sources in these two forests to make inferences on the range of spores dispersal. Results obtained by spraying wood discs with conidial suspensions in controlled conditions are in agreement with those obtained by exposing wood discs to the natural airborne inoculum in the forests, as clearly supported by the significant correlation (r = 0.79; p < 0.05) between the two sets of data. Susceptibility was highest in Pinus species, followed by P. abies and P. sitchensis. Susceptibility was lowest for L. sibirica and P. menziesii. The area colonized by Heterobasidion spp. in the sapwood of wood discs was much greater than that colonized in the heartwood. A sharp decrease in the rate of infection of wood discs with distance from spore sources (i.e., fruiting bodies) was observed, further confirming the importance of local spore sources in the epidemiology of Heterobasidion spp. Taken together, these findings could help designing tactics to manage these fungal forest pathogens. Full article
(This article belongs to the Special Issue Forest Pathology and Entomology)
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Article
Gypsy Moth Management with LdMNPV Baculovirus in Cork Oak Forest
Forests 2021, 12(4), 495; https://doi.org/10.3390/f12040495 - 16 Apr 2021
Cited by 1 | Viewed by 497
Abstract
(1) Research Highlights: Applications of a species-specific baculovirus is a promising method to control the gypsy moth and regulate its population dynamics in forest ecosystems. (2) Background and Objectives: Cork oak protection against the Lepidopteran defoliator Lymantria dispar requires an appropriate forest ecosystem [...] Read more.
(1) Research Highlights: Applications of a species-specific baculovirus is a promising method to control the gypsy moth and regulate its population dynamics in forest ecosystems. (2) Background and Objectives: Cork oak protection against the Lepidopteran defoliator Lymantria dispar requires an appropriate forest ecosystem management program, involving the application of eco-sustainable microbial products during population outbreaks. The species-specific multicapsid nucleopolyhedrovirus (LdMNPV), agent of natural epizootics in gypsy moth populations, represents an option that was investigated in a multi-year field study, involving viral applications either from the ground or by aerial treatment. (3) Materials and Methods: Efficacy trials against L. dispar populations were conducted in 2018 and 2019 in Sardinia, according to a randomized block design. Each year, two trials were conducted, applying a baculovirus commercial formulation with an atomizer from the ground and assessing the effects of different doses and application timing, respectively. An aerial application trial distributing LdMNPV at ultra-low volumes (2 L/ha) was also conducted in 2019 to assess the virus efficacy at a larger field scale. (4) Results: In both years, a significant increase in larval mortality was detected in plots treated with higher viral occlusion body (OB) doses and with an earlier application targeting younger larvae, in comparison with untreated controls. Due to an observed retrogradation phase of the target pest in 2019, no significant differences in larval density between areas treated from a helicopter and control were detected, but in the few weeks following application, a meaningful vitality decrease in larval samples from treated plots was observed. (5) Conclusions: Based on the results of this study, the use of LdMNPV in forest protection programs against gypsy moth can be worth consideration in multi-year integrated program strategies to modulate population dynamics. Full article
(This article belongs to the Special Issue Forest Pathology and Entomology)
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Article
Effects of Temperature on Anoplophora chinensis (Coleoptera: Cerambycidae) Adult Survival, Reproduction, and Egg Hatch
Forests 2021, 12(4), 432; https://doi.org/10.3390/f12040432 - 03 Apr 2021
Cited by 1 | Viewed by 383
Abstract
Anoplophora chinensis (Forster) is an invasive species that can damage many tree species in orchard, urban, and forested habitats. Adult survival, reproduction, and egg hatch of A. chinensis from Italy and China are evaluated at eight constant temperatures (5, 10, 15, 20, 25, [...] Read more.
Anoplophora chinensis (Forster) is an invasive species that can damage many tree species in orchard, urban, and forested habitats. Adult survival, reproduction, and egg hatch of A. chinensis from Italy and China are evaluated at eight constant temperatures (5, 10, 15, 20, 25, 30, 35, and 40 °C) under laboratory conditions. The estimated Tmax for longevity was 42 and 33 °C for females and 42 and 39 °C for males from China and Italy, respectively. The estimated Tmax, Tmin, and optimum temperature for fecundity were 35, 9, and 29 °C, respectively. Females laid eggs at 15–30 °C and eggs hatched at 15–35 °C. Days to first oviposition increased exponentially from 13 days at 30 °C to >300 days near 10 °C. The estimated Tmin for egg hatch was 13 °C, the Tmax at 38 °C, and the optimum 29 °C. Percentage hatch was estimated to be highest at 26 °C and have a Tmax of 31 °C and Tmin of 10 °C. These results indicate that summer temperatures over a wide range of latitudes should support beetle survival and reproduction, but at temperatures ≥35 °C, oviposition ceases, and adult survivorship declines. In addition, females may survive into the fall, but lay fewer eggs that may not hatch. These responses of A. chinensis to temperature can be used for developing phenological models to predict the timing of stages for management or eradication efforts. Full article
(This article belongs to the Special Issue Forest Pathology and Entomology)
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Article
Development of a Rapid Loop-Mediated Isothermal Amplification Assay for the Detection of Dothistroma septosporum
Forests 2021, 12(3), 362; https://doi.org/10.3390/f12030362 - 19 Mar 2021
Cited by 1 | Viewed by 721
Abstract
A Loop-Mediated Isothermal Amplification (LAMP) assay was developed for the detection of the pine pathogen Dothistroma septosporum (G. Dorog.) M. Morelet. The specificity of the LAMP assay was tested using a selection of pine needle fungi, including Dothistroma pini Hulbary, and Lecanosticta acicola [...] Read more.
A Loop-Mediated Isothermal Amplification (LAMP) assay was developed for the detection of the pine pathogen Dothistroma septosporum (G. Dorog.) M. Morelet. The specificity of the LAMP assay was tested using a selection of pine needle fungi, including Dothistroma pini Hulbary, and Lecanosticta acicola (Thüm.) Syd.; only D. septosporum DNA was amplified by the test. In terms of sensitivity, the assay was able to detect as little as 1 pg of total D. septosporum DNA. This assay enables DNA extracted from diseased host needles to be rapidly tested for the presence of D. septosporum using relatively simple to operate equipment away from a fully equipped molecular biology laboratory. Full article
(This article belongs to the Special Issue Forest Pathology and Entomology)
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Article
Captures of Emerald Ash Borer (Agrilus planipennis) Adults in Post-Invasion White Ash Sites with Varying Amounts of Live Phloem
Forests 2021, 12(3), 262; https://doi.org/10.3390/f12030262 - 25 Feb 2021
Cited by 1 | Viewed by 476
Abstract
Emerald ash borer (EAB), (Agrilus planipennis Fairmaire), first identified in 2002 in southeast Michigan, has caused catastrophic ash (Fraxinus spp.) mortality in forests within the core of the invasion and has spread to 35 states and five Canadian provinces. Little is [...] Read more.
Emerald ash borer (EAB), (Agrilus planipennis Fairmaire), first identified in 2002 in southeast Michigan, has caused catastrophic ash (Fraxinus spp.) mortality in forests within the core of the invasion and has spread to 35 states and five Canadian provinces. Little is known about persistence and densities of EAB populations in post-invasion sites after most ash trees have died. We monitored EAB populations from 2014 to 2016 using double decker (DD) traps set in the midst of white ash (F. americana) trees in 30 post-invasion sites in southeast and south-central Michigan. Two DD traps were deployed at each site. One trap had a dark green upper prism and light purple lower prism, both baited with cis-3-hexenol lures. The other had two dark purple prisms baited with cis-3-hexenol on the upper prism and Manuka oil on the lower prism. In 2014 and 2016, size and condition of ash trees were recorded and area of live white ash phloem was estimated in an 18-m-radius plot centered around each of the DD traps. Area of live white ash phloem per site ranged from approximately 24 to 421 m2 in 2014 and from 24 to 411 m2 in 2016. Canopy condition of live white ash trees generally improved; 65% and 89% of the trees had healthy canopies (<20% dieback) in 2014 and 2016, respectively. Traps in 28, 29 and 30 of the sites captured a total of 580, 585, and 932 EAB adults in 2014–2016, respectively. Area of live ash phloem explained relatively little of the variation in total EAB captures in all three years. Low trap catches, along with relatively stable canopy conditions and continued abundance of live white ash, indicate that EAB populations remain below the carrying capacity of the sites, and ash phloem availability is not a limiting factor for EAB abundance. Further monitoring to track both EAB dynamics and tree condition is needed to determine the long-term outlook for white ash in these sites. Full article
(This article belongs to the Special Issue Forest Pathology and Entomology)
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Article
Ips sexdentatus Mass-Trapping: Mitigation of Its Negative Effects on Saproxylic Beetles Larger Than the Target
Forests 2021, 12(2), 175; https://doi.org/10.3390/f12020175 - 03 Feb 2021
Viewed by 618
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Forest Pathology and Entomology)
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Communication
Potential Differences and Methods of Determining Gypsy Moth Female Flight Capabilities: Implications for the Establishment and Spread in Novel Habitats
Forests 2021, 12(1), 103; https://doi.org/10.3390/f12010103 - 19 Jan 2021
Cited by 1 | Viewed by 689
Abstract
The introduction of the Asian gypsy moth into novel environments continues with frequent interceptions in North America. There is a concern that these subspecies will pose a greater threat to the forests and urban environments of North America than the established gypsy moths [...] Read more.
The introduction of the Asian gypsy moth into novel environments continues with frequent interceptions in North America. There is a concern that these subspecies will pose a greater threat to the forests and urban environments of North America than the established gypsy moths (Lymantria dispardispar L.), due to their greater capacity for female flight. Asian gypsy moth populations vary in many key traits, including female flight capabilities. The potential impacts of female flight, in combination with the other key traits, on the ecology and spread of this insect are first discussed in this communication. This also provides the first review of most of the current literature on the variations in flight capability and flight distance of gypsy moth populations, as well as variation in other traits of concern and the potential methods of identification, with special attention paid to the Asian subspecies Lymantria dispar japonica Motschulsky and Lymantria dispar asiatica Vinkovskij. There are currently good tools for identifying the general origin of introduced gypsy moth populations, but these do not provide enough information to effectively manage introductions. Gypsy moth key traits differ among populations, even within each subspecies of the gypsy moth, so introduction of gypsy moths from other world areas into locations where the gypsy moth is already present could result in unwanted changes in gypsy moth biology. It also appears that the introduction of flight-capable females could enhance a population’s dispersal capability and require modifications to management protocols used for flightless females. Therefore, rapid tools to assess key traits in introduced populations are needed to adequately plan for, or deal with, new introductions into novel habitats. Full article
(This article belongs to the Special Issue Forest Pathology and Entomology)
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Article
Infection and Spread of Root Rot Caused by Heterobasidion parviporum in Picea abies Stands after Thinning: Case Studies on Former Pasture and Meadow Lands
Forests 2021, 12(1), 70; https://doi.org/10.3390/f12010070 - 09 Jan 2021
Viewed by 577
Abstract
Afforestation of former agricultural lands is a common practice in several countries. This is beneficial for avoiding diseases carry-over from previous forest generations and to expand forest areas. However, several biotic and abiotic risks have been reported in such stands, including a higher [...] Read more.
Afforestation of former agricultural lands is a common practice in several countries. This is beneficial for avoiding diseases carry-over from previous forest generations and to expand forest areas. However, several biotic and abiotic risks have been reported in such stands, including a higher risk of Heterobasidion root rot after thinning. Therefore, this study investigates the spread of Heterobasidion root rot in three Picea abies (L.) Karst. plantations in Latvia established on former pasture and meadow lands and subjected to forest management practices. Initially, to determine average infection rate, we sampled all standing trees (157 in total) along transects within sampling areas. On the transects, the proportion of trees suffering from Heterobasidion root rot varied from 16 to 33% among stands. Based on those data and observed dieback over all the stands, we established circular sample plots in disease centres where all trees and stumps were analysed. The average infection rate in the circular plots varied from 34 to 41%. Obtained Heterobasidion isolates were analysed with species-specific primers and were all determined to be Heterobasidion parviporum Niemelä & Korhonen. Isolates were paired to detect the number and size of genotypes. Of 141 genets examined, 99 were isolated from only one tree or stump, while 42 formed genets including two or more trees or stumps indicating spread of infection through root contacts. The total number of Heterobasidion genets per hectare in studied stands varied from 72 to 484. The following conclusions were reached: (i) stands on former non-forest lands (pastures and meadows) can be highly susceptible to Heterobasidion infection after thinning, (ii) the pathogen may form expanding territorial clones in both former pasture and meadows and (iii) stump treatment with biological or chemical control agents is recommended to prevent Heterobasidion infections. Full article
(This article belongs to the Special Issue Forest Pathology and Entomology)
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Communication
A Review of Forest Management Effects on Terrestrial Leaf Litter Inhabiting Arthropods
Forests 2021, 12(1), 23; https://doi.org/10.3390/f12010023 - 28 Dec 2020
Viewed by 653
Abstract
Leaf litter arthropods are some of the most abundant and diverse communities in forests and provide myriad ecosystem services from decomposition and mineralization to pollination and predation. They are important to forest health and management and, in turn, are affected by how we [...] Read more.
Leaf litter arthropods are some of the most abundant and diverse communities in forests and provide myriad ecosystem services from decomposition and mineralization to pollination and predation. They are important to forest health and management and, in turn, are affected by how we manage our forests. Various forest management techniques such as clear cutting, burning, and chemical control of invasive species all have differing effects on ground dwelling arthropods and, despite their importance, a review of the literature on these effects does not currently exist. My objective with this paper is to review the effects of different types of forest management on arthropods in leaf litter systems. Full article
(This article belongs to the Special Issue Forest Pathology and Entomology)
Article
Monitoring and Management of the Pine Processionary Moth in the North-Western Italian Alps
Forests 2020, 11(12), 1253; https://doi.org/10.3390/f11121253 - 26 Nov 2020
Cited by 1 | Viewed by 667
Abstract
The pine processionary moth (PPM), Thaumetopoea pityocampa (Denis and Schiffermüller, 1775) (Lepidoptera, Notodontidae), is considered one of the main insect defoliators of conifers in Southern Europe and North Africa. The species is oligophagous on pines and cedars in Mediterranean countries. This 6-year investigation [...] Read more.
The pine processionary moth (PPM), Thaumetopoea pityocampa (Denis and Schiffermüller, 1775) (Lepidoptera, Notodontidae), is considered one of the main insect defoliators of conifers in Southern Europe and North Africa. The species is oligophagous on pines and cedars in Mediterranean countries. This 6-year investigation (2014–2019), carried out in Aosta Valley (NW Italy), on Pinus sylvestris L. aimed to: (i) Monitor the PPM population with pheromone-baited funnel traps; (ii) assess the infestation index (0–5 classes) according to the degree of defoliation; and (iii) apply control strategies, namely Bacillus thuringiensis var. kurstaki (Btk) and mating disruption (MD). In total, 9618 ha were visually monitored and assigned an infestation index. The percentage of woodland stands that were strongly defoliated by PPM (infestation index ≥ 3) increased progressively between 2015 and 2016, affecting from 8% to 19% of the total area monitored; this area decreased to 16% and 13% in 2017 and 2018, respectively, followed by an abrupt decline to 4% in 2019. Both Btk applications and mating disruption significantly reduced the infestation. Where Btk was applied, the rate of larval mortality ranged from 79.47% to 98.43%; conversely, in the control plots, the larval mortality was, on average, 1.56%. The mean number of PPM males captured in traps was significantly lower in the plots where MD was performed, ranging from 8.36 ± 2.37 to 13.47 ± 4.68. The mean number of males captured in the control plots was, on average, 119.16 ± 12.68. The total number of nests recorded per tree was significantly lower in MD plots, ranging from 0.41 ± 0.05 to 0.94 ± 0.14. In the control plots, there were, on average, 4.37 ± 0.76 nests per tree. As already documented for several defoliating forestry insect pests, both Btk and mating disruption proved effective in controlling PPM infestations, and thus, microbial insecticides should be strongly encouraged and adopted by forest managers. Full article
(This article belongs to the Special Issue Forest Pathology and Entomology)
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Article
Patterns of Diversity in the Symbiotic Mite Assemblage of the Mountain Pine Beetle, Dendroctonus Ponderosae Hopkins
Forests 2020, 11(10), 1102; https://doi.org/10.3390/f11101102 - 17 Oct 2020
Cited by 1 | Viewed by 959
Abstract
The mountain pine beetle, Dendroctonus ponderosae (Coleoptera: Scolytinae), is an economically important bark beetle species with a wide geographic range spanning from the southwestern United States into northern Canada. This beetle causes extensive tree mortality to 13 pine species. Mites (Acari) are [...] Read more.
The mountain pine beetle, Dendroctonus ponderosae (Coleoptera: Scolytinae), is an economically important bark beetle species with a wide geographic range spanning from the southwestern United States into northern Canada. This beetle causes extensive tree mortality to 13 pine species. Mites (Acari) are common and abundant symbionts of mountain beetles that may influence their fitness through positive and negative interactions. We present a unique assessment of the mite associates of mountain pine beetles using measures of alpha and beta diversity. We sampled phoretic mites from five beetle populations: Arizona, Colorado, South Dakota, Utah (USA), and Alberta (Canada) that varied in host tree species, local climate, and beetle population level. We collected 4848 mites from 8 genera and 12 species. Fifty to seventy percent of beetles carried mites in flight with the highest mite loads occurring in middle and southern populations; decreasing in northern populations. Mite assemblages (i.e., both richness and composition) varied along a south to north latitudinal gradient and were driven by species turnover (i.e., species replacement). Differences in mite composition increased with distance between populations. We discuss climatic variation, environmental filtering, and host tree differences as factors that could affect differences in mite composition between beetle populations and discuss implications for functional shifts. Our results could represent a model for estimating diversity patterns of mite symbionts associated with other major insect pests in coniferous forest systems. Full article
(This article belongs to the Special Issue Forest Pathology and Entomology)
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Article
Diversity of Phytophthora Communities across Different Types of Mediterranean Vegetation in a Nature Reserve Area
Forests 2020, 11(8), 853; https://doi.org/10.3390/f11080853 - 06 Aug 2020
Viewed by 1277
Abstract
Research Highlights: Protected natural areas are a reservoir of Phytophthora species and represent the most suitable sites to study their ecology, being less disturbed by human activities than other environments. Background and Objectives: The specific objective of this study was to correlate the [...] Read more.
Research Highlights: Protected natural areas are a reservoir of Phytophthora species and represent the most suitable sites to study their ecology, being less disturbed by human activities than other environments. Background and Objectives: The specific objective of this study was to correlate the diversity and distribution of Phytophthora species with the vegetation in aquatic, riparian and terrestrial habitats within a protected area in Eastern Sicily, Southern Italy. Materials and Methods: Environmental samples (water and soil) were sourced from two streams running through the reserve and six different types of vegetation, including Platano-Salicetum pedicellatae, the Sarcopoterium spinosum community, Myrto communis-Pistacietum lentisci, Pistacio-Quercetum ilicis,Oleo-Quercetum virgilianae and a gallery forest dominated by Nerium oleander (Natura 2000 classification of habitats). Phytophthora species were recovered from samples using leaf baiting and were classified on the basis of morphological characteristics and sequencing of internal transcribed spacer (ITS) regions of ribosomal DNA (rDNA). Results: As many as 11 Phytophthora species, within five different ITS clades, were identified, including P. asparagi, P. bilorbang, P. cryptogea, P. gonapodyides, P. lacustris, P. multivora, P. nicotianae, P. oleae, P. parvispora, P. plurivora and P. syringae. No Phytophthora species were found in the Sarcopoterium spinosum comm. Phytophthora asparagi, P. lacustris and P. plurivora were the prevalent species in the other five plant communities, but only P. plurivora was present in all of them. Overall aquatic species from clade 6 (100 out of 228 isolates) were the most common; they were recovered from all five types of vegetation, streams and riparian habitats. Phytophthora populations found in the Platano-Salicetum pedicellatae and Oleo-Quercetum virgilianae show the highest diversity, while no correlation was found with the physicochemical characteristics of the soil. Conclusions: The vegetation type and the aquatic or terrestrial habitat were identified as major environmental factors correlated with the diversity of Phytophthora communities in this reserve. Full article
(This article belongs to the Special Issue Forest Pathology and Entomology)
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Article
Improved Identification and New Records of Dendroctonus Bark Beetles Attacking Pinus contorta in the Subalpine Forest of the Southern Rocky Mountains
Forests 2020, 11(6), 656; https://doi.org/10.3390/f11060656 - 09 Jun 2020
Viewed by 623
Abstract
Research Highlights: Atypical and poorly understood attacks by Dendroctonus rufipennis (Kirby) to Pinus contorta Doug. ex Loudon were detected in the southern Rocky Mountains (SRM). The phenomenon is confirmed across all examined area. Its reproduction is described for the first time as well [...] Read more.
Research Highlights: Atypical and poorly understood attacks by Dendroctonus rufipennis (Kirby) to Pinus contorta Doug. ex Loudon were detected in the southern Rocky Mountains (SRM). The phenomenon is confirmed across all examined area. Its reproduction is described for the first time as well as the first attacks of D. adjunctus Blandf. in that host. Improved detection and diagnostics of D. rufipennis will allow a simpler, and efficient identification of the species. It will improve the detection capacity by pest detection specialists and entomologists, which will increase our understanding of the phenomena within and beyond the known range. Background and Objectives: In addition to D. ponderosae Hopk. other Dendroctonus species, sometimes together, attacked P. contorta that grew intermixed with Picea engelmannii in the SRM’ subalpine forest. The identification of these beetles was difficult. The goal was to improve the detection and identification of the species from similar Dendroctonus spp. attacking that host and to uncover biological facts about the phenomena. Materials and Methods: Dendroctonus attacking P. contorta were collected along the entire SRM, their attack signs and behavior were recorded. These characteristics were revised from those in the literature and new characters were introduced and tested. Results: The identification of Dendroctonus bark beetles attacking P. contorta in the SRM was improved using revised and new characters including attack signs, attack behavior, and adult beetle characters. An improved identification key couplet is presented to effectively distinguish D. murrayanae from D. rufipennis. Conclusions: Simplified insect identifications that are both accessible to users with different levels of expertise and are based on insect characters, their attack pattern, and signs, like the present, improve detection of insects of interest. Efficient insect detections allow a better understanding of the capabilities they have and the impact they cause to the woodland ecosystems we study, protect, and manage around the globe. Full article
(This article belongs to the Special Issue Forest Pathology and Entomology)
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Article
Phylogenetic Relationships between Phlebiopsis gigantea and Selected Basidiomycota Species Inferred from Partial DNA Sequence of Elongation Factor 1-Alpha Gene
Forests 2020, 11(5), 592; https://doi.org/10.3390/f11050592 - 24 May 2020
Cited by 1 | Viewed by 923
Abstract
Phlebiopsis gigantea (Fr.) Jülich has been successfully used as a biological control fungus for Heterobasidion annosum (Fr.) Bref., an important pathogen of pine and spruce trees. The P. gigantea species has been known for many years, but our understanding of the relationship between [...] Read more.
Phlebiopsis gigantea (Fr.) Jülich has been successfully used as a biological control fungus for Heterobasidion annosum (Fr.) Bref., an important pathogen of pine and spruce trees. The P. gigantea species has been known for many years, but our understanding of the relationship between various isolates of this fungus has been substantially improved through the application of DNA sequence comparisons. In this study, relationships between P. gigantea and selected Basidiomycota species was determined, based on elongation factor 1-alpha (EF1α) partial DNA sequence and in silico data. A total of 12 isolates, representing the most representatives of P. gigantea, with diverse geographic distributions and hosts, were included in this study. Phylogenetic trees generated for sequences obtained in this research, grouped the European taxa of P. gigantea and partial sequence of the genome deposed in NCBI database, in a strongly supported clade, basal to the rest of the strains included in the study. P. gigantea isolates originating from Poland, Finland, Sweden, Great Britain and partial sequence of genome formed a monophyletic group. Within this group, isolates of P. gigantea constituted two subclades, showing their partial difference like the two SNPs (single nucleotide polymorphisms) between one and the rest of isolates. The intron and exon relationships among P. gigantea isolates were moreover resolved. The results obtained using the EF1α region should be useful in the selection of more efficient P. gigantea isolates for limiting forest tree root pathogens. Full article
(This article belongs to the Special Issue Forest Pathology and Entomology)
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Article
PHYCI_587572: An RxLR Effector Gene and New Biomarker in A Recombinase Polymerase Amplification Assay for Rapid Detection of Phytophthora cinnamomi
Forests 2020, 11(3), 306; https://doi.org/10.3390/f11030306 - 11 Mar 2020
Cited by 3 | Viewed by 837
Abstract
Phytophthora cinnamomi is a devastating pathogen causing root and crown rot and dieback diseases of nearly 5000 plant species. Accurate and rapid detection of P. cinnamomi plays a fundamental role within the current disease prevention and management programs. In this study, a novel [...] Read more.
Phytophthora cinnamomi is a devastating pathogen causing root and crown rot and dieback diseases of nearly 5000 plant species. Accurate and rapid detection of P. cinnamomi plays a fundamental role within the current disease prevention and management programs. In this study, a novel effector gene PHYCI_587572 was found as unique to P. cinnamomi based on a comparative genomic analysis of 12 Phytophthora species. Its avirulence homolog protein 87 (Avh87) is characterized by the Arg-Xaa-Leu-Arg (RxLR) motif. Avh87 suppressed the pro-apoptotic protein BAX- and elicitin protein INF1-mediated cell death of Nicotiana benthamiana. Furthermore, a recombinase polymerase amplification-lateral flow dipstick detection assay targeting this P. cinnamomi-specific biomarker was developed. While successfully detected 19 P. cinnamomi isolates of a global distribution, this assay lacked detection of 37 other oomycete and fungal species, including P. parvispora, a sister taxon of P. cinnamomi. In addition, it detected P. cinnamomi from artificially inoculated leaves of Cedrus deodara. Moreover, the RPA-LFD assay was found to be more sensitive than a conventional PCR assay, by detecting as low as 2 pg of genomic DNA in a 50-µL reaction. It detected P. cinnamomi in 13 infested soil samples, while the detection rate was 46.2% using PCR. Results in this study indicated that PHYCI_587572 is a unique biomarker for detecting P. cinnamomi. Although PHYCI_587572 was identified as an effector gene based on the RxLR motif of Avh87 and the avirulence activity on Nicotiana, its exact genetic background and biological function on the natural hosts of P. cinnamomi warrant further investigations. Full article
(This article belongs to the Special Issue Forest Pathology and Entomology)
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Review

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Review
On Some Significant Phytoplasma Diseases of Forest Trees: An Update
Forests 2021, 12(4), 408; https://doi.org/10.3390/f12040408 - 29 Mar 2021
Viewed by 542
Abstract
This paper provides an updating of information of a selected number of major phytoplasma diseases of forest trees, with a focus on the associated phytoplasma taxa. Phytoplasma diseases of forest trees have been less extensively studied than those affecting fruit trees. Research on [...] Read more.
This paper provides an updating of information of a selected number of major phytoplasma diseases of forest trees, with a focus on the associated phytoplasma taxa. Phytoplasma diseases of forest trees have been less extensively studied than those affecting fruit trees. Research on the role of phytoplasmas as the cause of diseases of forest trees has only in the last few years been intensified, after sensitive and specific detection methods greatly based on PCR technology became available. Various phytoplasma taxa have been identified in naturally infected elm, ash, conifer, sandal, and eucalyptus trees, whereas only one phytoplasma taxon has been recorded in naturally infected alder trees. However, for almost all of the reviewed diseases, there is still sparse information about insect vectors, plant host range, strain virulence, pathogenicity, and host tolerance and resistance. Knowledge of these aspects is the basis for appropriate disease management. In particular, further research is required to clarify the role of phytoplasmas in asymptomatic trees. In addition, the etiological role of various “non-specific” phytoplasma taxa, which have been recorded in forest trees, while no data from pathological studies are available, needs to be further investigated. Full article
(This article belongs to the Special Issue Forest Pathology and Entomology)
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