Research

15 pages, 4497 KiB

Open AccessEditor’s ChoiceArticle

Botryosphaeriaceae Species Associated with Stem Canker, Shoot Blight and Dieback of Fraxinus ornus in Italy

by Alessandra Benigno, Chiara Aglietti, Giovanni Rossetto, Carlo Bregant, Benedetto Teodoro Linaldeddu and Salvatore Moricca

Forests 2024, 15(1), 51; https://0-doi-org.brum.beds.ac.uk/10.3390/f15010051 - 26 Dec 2023

Viewed by 1073

Abstract

A severe dieback of flowering ash (Fraxinus ornus L.) has been observed in north-central Italy in the last decades. Symptoms include typical sunken, light-brown cankers on the stem and branches; vascular discoloration; tip and shoot dieback; and foliage necroses. The disease was [...] Read more.

A severe dieback of flowering ash (Fraxinus ornus L.) has been observed in north-central Italy in the last decades. Symptoms include typical sunken, light-brown cankers on the stem and branches; vascular discoloration; tip and shoot dieback; and foliage necroses. The disease was more evident at the beginning of the growing season, and more severe on young regeneration. Six Botryosphaeriaceae species were consistently isolated from symptomatic plant tissues: Botryosphaeria dothidea, Diplodia fraxini, Diplodia subglobosa, Dothiorella iberica, Dothiorella omnivora and Neofusicoccum parvum. B. dothidea and D. fraxini expressed higher aggressiveness and showed a widespread incidence, being the species most frequently associated with cankers; the other four species were less virulent and more erratic, occurring mainly on succulent branch tips and foliage. Isolates were characterized using morphological and molecular approaches (colony/conidial phenotyping and rDNA-ITS genotyping). Phylogenetic analysis provided congruent phylogenies depicting the relationships of the six taxa with the most closely related conspecifics. Pathogenicity tests on 2-year-old seedlings confirmed the higher virulence of B. dothidea and D. fraxini. Extensive, multi-year field surveys at different sites supported the hypothesis that climatic vagaries, mainly heat, water and drought stresses, impaired tree health and vigor, facilitating infection and pervasive colonization by these Botryosphaeriaceae species. Environmental stressors are thus the key factor bringing the six fungal pathogens together in a multitrophic interaction with F. ornus in a novel, lethal fashion. Full article

(This article belongs to the Special Issue Forest Pathology and Entomology—Series II)

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24 pages, 6892 KiB

Open AccessEditor’s ChoiceArticle

Diversity of Phytophthora Species Involved in New Diseases of Mountain Vegetation in Europe with the Description of Phytophthora pseudogregata sp. nov.

by Carlo Bregant, Giovanni Rossetto, Letizia Meli, Nicolò Sasso, Lucio Montecchio, Ana Brglez, Barbara Piškur, Nikica Ogris, Lucia Maddau and Benedetto Teodoro Linaldeddu

Forests 2023, 14(8), 1515; https://0-doi-org.brum.beds.ac.uk/10.3390/f14081515 - 25 Jul 2023

Cited by 5 | Viewed by 1593

Abstract

New and emerging Phytophthora-related diseases in small trees, shrubs and herbaceous plants typical of subalpine vegetation have recently been observed in Italy and Slovenia. Diseased plants showed a complex symptomatology including foliar necrosis, fruit rot, shoot blight and branch bleeding cankers. Since [...] Read more.

New and emerging Phytophthora-related diseases in small trees, shrubs and herbaceous plants typical of subalpine vegetation have recently been observed in Italy and Slovenia. Diseased plants showed a complex symptomatology including foliar necrosis, fruit rot, shoot blight and branch bleeding cankers. Since little information is available about the aetiology of these aerial Phytophthora diseases, from 2019 to 2022, field surveys were conducted in 54 sites to define the occurrence, distribution and impact of the Phytophthora species on mountain vegetation. A total of 360 Phytophthora isolates were obtained from 397 samples collected from 33 herbaceous and woody host species. Based on phylogenetic analysis and morphometric data, 17 Phytophthora species were identified: P. pseudosyringae (201 isolates), P. plurivora (54), P. gonapodyides (21), P. ilicis (20), P. alpina (17), P. acerina (11), P. cactorum (7), P. pseudocryptogea (6), P. cambivora (5), P. idaei (4), P. psychrophila (3), P. bilorbang (2), P. chlamydospora (2), P. hedraiandra (1), P. kelmanii (1), P. rosacearum (1) and P. syringae (1). In addition, three isolates of a new putative Phytophthora species obtained from Alnus viridis, Juniperus communis and Rhododendron ferrugineum are described here as Phytophthora pseudogregata sp. nov. Overall, the results highlighted an unexpectedly high diversity of Phytophthora species in mountain areas, with many species able to cause aerial infections due to the production of caducous sporangia. Full article

(This article belongs to the Special Issue Forest Pathology and Entomology—Series II)

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17 pages, 2153 KiB

Open AccessArticle

The Impact of Predation of Laricobius nigrinus (Coleoptera: Derodontidae) on Adelges tsugae (Hemiptera: Adelgidae) and Tsuga canadensis (Pinales: Pinaceae) Tree Health

by Carrie E. Preston, Alicia Arneson, John R. Seiler and Scott M. Salom

Forests 2023, 14(4), 698; https://0-doi-org.brum.beds.ac.uk/10.3390/f14040698 - 29 Mar 2023

Cited by 4 | Viewed by 1202

Abstract

The hemlock woolly adelgid (HWA), Adelges tsugae, has threatened the sustainable management of Tsuga canadensis in the eastern United States. Biological control efforts have led to the establishment of Laricobius nigrinus, a specialist predator of HWA. Although L. nigrinus has a [...] Read more.

The hemlock woolly adelgid (HWA), Adelges tsugae, has threatened the sustainable management of Tsuga canadensis in the eastern United States. Biological control efforts have led to the establishment of Laricobius nigrinus, a specialist predator of HWA. Although L. nigrinus has a significant impact on HWA populations, its effect on the health of HWA’s host is unknown. In 2020, 14 eastern hemlocks at one site in Virginia were selected to determine whether predation of L. nigrinus at different densities on HWA populations had an effect on tree health. Laricobius nigrinus predation significantly impacted the HWA sistens generation, resulting in significantly more new shoots produced on treatment branches with the greatest density of L. nigrinus adults. Final HWA density was lowest on treatment branches with L. nigrinus, followed by the negative control, and the treatment without L. nigrinus. In June, the photosynthetic rate was significantly greater for the negative control, followed by L. nigrinus treatments. There were no statistical differences among measured tree physiological parameters in July and October, indicating a temporary effect from L. nigrinus predation on hemlock tree physiology. Full article

(This article belongs to the Special Issue Forest Pathology and Entomology—Series II)

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9 pages, 3630 KiB

Open AccessArticle

Enzyme-Mediated Amplification (EMA) for Detection of the Pinewood Nematode Bursaphelenchus xylophilus

by Li-Chao Wang, Min Li, Ruo-Cheng Sheng and Feng-Mao Chen

Forests 2022, 13(9), 1419; https://0-doi-org.brum.beds.ac.uk/10.3390/f13091419 - 03 Sep 2022

Cited by 2 | Viewed by 1168

Abstract

The pinewood nematode (PWN), Bursaphelenchus xylophilus, is a notorious parasitic nematode of pine trees that causes pine wilt disease (PWD), leading to extensive mortality of different pine species around the world and considerable economic losses, thus posing a threat to healthy pines [...] Read more.

The pinewood nematode (PWN), Bursaphelenchus xylophilus, is a notorious parasitic nematode of pine trees that causes pine wilt disease (PWD), leading to extensive mortality of different pine species around the world and considerable economic losses, thus posing a threat to healthy pines worldwide. Fast and accurate detection technology is necessary for the management of PWD spread. This study describes the development of a new DNA extraction method and detection technology, enzyme-mediated amplification (EMA), using primers and a newly designed probe according to the rRNA internal transcribed spacer gene ITS2. The detection process can be completed within 40 min, including DNA extraction for 10 min and detection for 30 min, by exploiting the synergistic action of multiple enzymes. This method can detect PWNs from different geographic areas quickly and accurately at all life stages, singly or in a mixture, and can distinguish PWNs from other species of the Bursaphelenchus group, showing that it is not only reliable but also rapid, greatly improving the efficiency and speed of PWN detection. Therefore, the technology is expected to be highly beneficial in PWN quarantine testing. Full article

(This article belongs to the Special Issue Forest Pathology and Entomology—Series II)

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14 pages, 1295 KiB

Open AccessArticle

Suitability of Turkey Oak, European Beech, and Hornbeam to Gypsy Moth Feeding

by Slobodan Milanović, Zoran Miletić, Čedomir Marković, Darka Šešlija Jovanović, Zoran Trailović, Libor Jankovský and Jelica Lazarević

Forests 2022, 13(7), 1006; https://0-doi-org.brum.beds.ac.uk/10.3390/f13071006 - 26 Jun 2022

Cited by 2 | Viewed by 1613

Abstract

Pest resistance of trees should be taken into account in future forest strategy planning and predicting risks of defoliation. The gypsy moth (GM) (Lymantria dispar L.) is a serious forest pest with outbreaking population dynamics. To estimate defoliation risk of the most [...] Read more.

Pest resistance of trees should be taken into account in future forest strategy planning and predicting risks of defoliation. The gypsy moth (GM) (Lymantria dispar L.) is a serious forest pest with outbreaking population dynamics. To estimate defoliation risk of the most widely distributed tree species in Balkan Peninsula and Europe (Turkey oak Quercus cerris L., European beech Fagus sylvatica L. and hornbeam Carpinus betulus L.), we carried out laboratory feeding trials and investigated their acceptability and suitability for GM development. We determined morphological and chemical attributes of these hosts as well as larval host preference, growth and nutritional indices. Preference, growth, and efficiency of food conversion into biomass were ranked in the order: Turkey oak ˃ European beech ˃ hornbeam. Hornbeam was the most avoided and showed the lowest conversion efficiency although, comparing to optimal oak host, its leaves were less tough, contained more water and exhibited similar values of nitrogen (index of protein content) and C/N ratio (index of investment into carbon based plant defense). We suggest that hornbeam and beech leaf chemical profiles should be further studied to reveal specific compounds that impose high metabolic cost to GM larvae. Moreover, additional research are needed to understand how intermediate hosts in natural populations affect GM outbreaks. Full article

(This article belongs to the Special Issue Forest Pathology and Entomology—Series II)

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10 pages, 2703 KiB

Open AccessArticle

Outbreak of Pityogenes chalcographus and Pityophthorus pityographus on Spruce Seedlings Resulting from Inappropriate Management in a Forest Nursery

by Tomáš Fiala and Jaroslav Holuša

Forests 2022, 13(7), 987; https://0-doi-org.brum.beds.ac.uk/10.3390/f13070987 - 23 Jun 2022

Cited by 1 | Viewed by 1641

Abstract

In this report, we describe a local outbreak of small bark beetles on 4-year-old seedlings of Picea abies in a forest nursery in Central Europe in 2021. In March 2022, 10–50% of the seedlings were “dry” (i.e., with dry and easily broken twigs [...] Read more.

In this report, we describe a local outbreak of small bark beetles on 4-year-old seedlings of Picea abies in a forest nursery in Central Europe in 2021. In March 2022, 10–50% of the seedlings were “dry” (i.e., with dry and easily broken twigs and with easily peeled bark) in each 4-row bed in the nursery. Half of the dry plants were completely covered by galleries of bark beetles and another 35% of the seedlings were with one or two bark beetle galleries. Almost 90% of the beetles found on the affected seedlings were Pityogenes chalcographus, and only 10% were Pityophthorus pityographus (we studied 100 seedlings in the second bed). The chipping of Picea pungens in previous years had left many felled trunks, branches, and other logging residues in the area. These residues are covered by galleries of both bark beetles. We suggest that, after multiplying on the logging residues, the beetles could not find suitable material for reproduction and were lured to the nursery seedlings, which had been weakened by location (a location that provided inadequate shade and no wind protection) and by repeated replanting. Full article

(This article belongs to the Special Issue Forest Pathology and Entomology—Series II)

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10 pages, 3602 KiB

Open AccessArticle

Promoting Effect of Choline-Phosphate Cytidylyltransferase Gene (pcyt-1) on Departure of Pinewood Nematode from Monochamus alternatus

by Yang Wang, Mingxia Jin, Lichao Wang, Ailin Yu, Guai Xie and Fengmao Chen

Forests 2022, 13(1), 114; https://0-doi-org.brum.beds.ac.uk/10.3390/f13010114 - 13 Jan 2022

Cited by 1 | Viewed by 1676

Abstract

In order to study the key gene in internal causes of pinewood nematode (PWN), Bursaphelenchus xylophilus, a departure from its vector beetle, Monochamus alternatus, we collected PWNs extracted from newly emerged M. alternatus and beetles 7 days after emergence. The total [...] Read more.

In order to study the key gene in internal causes of pinewood nematode (PWN), Bursaphelenchus xylophilus, a departure from its vector beetle, Monochamus alternatus, we collected PWNs extracted from newly emerged M. alternatus and beetles 7 days after emergence. The total RNAs of the two groups of PWNs were extracted, transcriptomes sequencing was performed, and gene expression differences between the two groups of PWN were analyzed. It was found that the expression of the choline-phosphate cytidylyltransferase gene (pcyt-1) was markedly up-regulated. After inhibition of pcyt-1 expression by RNA interference, the rate of lipid degradation in PWN decreased significantly, and the motility of PWN also decreased significantly. The analysis identified that phosphatidylcholine could promote the emulsification and degradation of neutral lipid granules in PWN, which provides sufficient energy for PWN departure from M. alternatus. The up-regulation of the gene pcyt-1 is an important internal factor for PWN departure from its vector. Full article

(This article belongs to the Special Issue Forest Pathology and Entomology—Series II)

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10 pages, 1967 KiB

Open AccessArticle

Morphological and Phylogenetic Analyses Reveal a New Species of Ceratocystiopsis (Ophiostomataceae, Ophiostomatales) Associated with Ips subelongatus in Inner Mongolia (China) with Weak Host Pathogenicity

by Zheng Wang, Ya Liu, Caixia Liu, Zhenyu Liu, Lijun Liang and Quan Lu

Forests 2021, 12(12), 1795; https://0-doi-org.brum.beds.ac.uk/10.3390/f12121795 - 17 Dec 2021

Cited by 3 | Viewed by 2023

Abstract

Ophiostomatoid fungi are known for their associations with bark beetles, and some species are important sources of tree diseases. Ceratocystiopsis is a genus of the ophiostomatoid fungi in order Ophiostomatales. The shortage of DNA barcodes for many species in this genus has [...] Read more.

Ophiostomatoid fungi are known for their associations with bark beetles, and some species are important sources of tree diseases. Ceratocystiopsis is a genus of the ophiostomatoid fungi in order Ophiostomatales. The shortage of DNA barcodes for many species in this genus has resulted in the presence of many unnamed cryptic species. In this study, Ceratocystiopsis subelongati sp. nov. associated with Ips subelongatus infesting Pinus sylvestris var. mongolica in Inner Mongolia, China, was identified and described based on phylogenetic inference of multi-gene DNA sequences and morphological characteristics. The species is characterized by a hyalorhinocladiella- to sporothrix-like asexual state and an optimal growth temperature of 30 °C. Artificial inoculation tests in the field showed that it is mildly pathogenic to five-year-old larch trees, the main host of I. subelongatus. It is also the first described Ceratocystiopsis species associated with I. subelongatus in China. This discovery should provide new avenues for studying the symbiosis between bark beetles and ophiostomatoid fungi. Full article

(This article belongs to the Special Issue Forest Pathology and Entomology—Series II)

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9 pages, 1852 KiB

Open AccessArticle

Fungi from Galleries of the Emerald Ash Borer Produce Cankers in Ash Trees

by Nickolas N. Rajtar, Benjamin W. Held and Robert A. Blanchette

Forests 2021, 12(11), 1509; https://0-doi-org.brum.beds.ac.uk/10.3390/f12111509 - 01 Nov 2021

Cited by 4 | Viewed by 2614

Abstract

The emerald ash borer (EAB, Agrilus planipennis) is a devastating invasive pest that has killed millions of ash trees in the United States and Canada. EAB was discovered in the US in 2002 and first reported in Minnesota in 2009. It attacks [...] Read more.

The emerald ash borer (EAB, Agrilus planipennis) is a devastating invasive pest that has killed millions of ash trees in the United States and Canada. EAB was discovered in the US in 2002 and first reported in Minnesota in 2009. It attacks ash trees that are native to the United States, including Fraxinus americana (white ash), F. nigra (black ash) and F. pennsylvanica (green ash). It also attacks Chionanthus virginicus (white fringe tree). Seven species of fungi isolated and identified only from EAB-infested trees in a previous study as having the potential to cause cankers were used to test their pathogenicity in F. americana (white ash). The fungi used were Cytospora pruinosa, Diplodia mutila, Diplodia seriata, Paraconiothyrium brasiliense, Phaeoacremonium minimum, Phaeoacremonium scolyti, and Thyronectria aurigera. Two field experiments that used F. americana used two inoculation methods: woodchip and agar plug inoculations. Results indicated that all of the fungi tested caused cankers in varying amounts, as compared to the controls. The largest cankers were caused by D. mutila (270 mm²), C. pruinosa (169 mm²), and D. seriata (69 mm²). All fungi except for T. aurigera were re-isolated and sequenced to confirm Kochs’ postulates. Canker-causing fungi found in association with EAB galleries have the potential to contribute to tree dieback and mortality. Full article

(This article belongs to the Special Issue Forest Pathology and Entomology—Series II)

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