International trade in plants and climate change are two of the main factors causing damaging tree pests (i.e. fungi and insects) to spread into new areas. To mitigate these risks, a large-scale assessment of tree-associated fungi and insects is needed. We present records of endophytic fungi and insects in twigs of 17 angiosperm and gymnosperm genera, from 51 locations in 32 countries worldwide. Endophytic fungi were characterized by high-throughput sequencing of 352 samples from 145 tree species in 28 countries. Insects were reared from 227 samples of 109 tree species in 18 countries and sorted into taxonomic orders and feeding guilds. Herbivorous insects were grouped into morphospecies and were identified using molecular and morphological approaches. This dataset reveals the diversity of tree-associated taxa, as it contains 12,721 fungal Amplicon Sequence Variants and 208 herbivorous insect morphospecies, sampled across broad geographic and climatic gradients and for many tree species. This dataset will facilitate applied and fundamental studies on the distribution of fungal endophytes and insects in trees.
Summary Twenty‐six commercial formulations of fungicides at six concentrations were evaluated in vitro for their efficacy on mycelial growth of Hymenoscyphus fraxineus (anamorph Chalara fraxinea). The results are presented as EC50, EC90 and minimal inhibitory concentration values; the comparisons with the recommended application concentrations showed that 10 of the 26 fungicides were highly effective in their ability to inhibit the mycelial growth of the pathogen. The eight most effective fungicides identified based on multiple comparisons analysis were azoxystrobin, bitertanol, captan (in two‐component preparation with trifloxystrobin), difenoconazole, kresoxim‐methyl, spiroxamine (in multicomponent preparation with tebuconazole and triadimenol), tebuconazole and trifloxystrobin. Azoxystrobin, difenoconazole, kresoxim‐methyl, mancozeb, myclobutanil, pyrimethanil, tebuconazole and trifloxystrobin were selected to verify their effectiveness in in planta tests. During two field tests in nurseries, it was found out that tebuconazole (triazole), trifloxystrobin and kresoxim‐methyl (strobilurins) and mancozeb (dithiocarbamate) were significantly effective against H. fraxineus. The best results were gained with tebuconazole, when mean percentage of diseased saplings was 16.3%, whereas in the control, it was 63.6%. The combination and alternation of fungicides from the triazole, strobilurine and dithiocarbamate chemical groups should be an effective tool for protecting ash saplings in forest nurseries. Moreover, exact timing of the treatment reflecting rainfall and development of first symptoms in the foliage will be also important.
Due to its high tolerance to acid rain, the North American Colorado blue spruce (Picea pungens) has been among the most frequent substitute tree species used in reforestation programmes in spruce mountain forests in the Ore and Sudeten Mountains in the Czech Republic after destruction by sulphur dioxide pollution in the second half of the last century. This species was planted on more than 8800 ha of destroyed mountain forest stands in the Ore Mountains alone. New plantations prospered until a massive outbreak of the gemmamyces bud blight, first identified in 2009. The causal agent, Gemmamyces piceae, induced massive bud blight in infected trees -bud loss progressively increased to 70-80% or more, and because the trees were not able to replace the natural loss of older needles, they quickly withered and died. Many plantations disrupted by the pathogen had to be cut down. Although several resistant genotypes have been identified, the cultivation of this species in forest stands has no future in this area. Because this disease was also identified in several ornamental plantations in the area, the bud blight epidemic haunts public green space administrators and nursery and Christmas tree plantation owners. Other pathogens and pests, such as Lophodermium piceae, Sirococcus conigenus and Elatobium abietinum, have also been identified as involved in the damage to P. pungens.
In Nov 2011, and then recurrently since Sep 2020, an extensive decline has been recorded in boxwood (Buxus sempervirens), sometimes with several dozens of damaged individuals planted in private gardens and public areas and purchased in amateur markets in the Czech Republic. The leaves of the plants first showed orange-bronze discoloration, then dried and fell off, and the affected plants died. The roots, collars and stems of these plants had dark brown to black necrotic lesions. Phytophthora occultans Man in 't Veld & K. Rosend. was consistently isolated on selective medium PARPNH (Jung et al. 1996) directly from segments of symptomatic collar tissues and from rhododendron leaf pieces used to bait excised roots. On 20% V8 agar (V8A) and on carrot agar (CA), colonies had a stellate pattern. Radial growth at 25°C was 9.4 mm/day on V8A and 5.3 mm/day on CA. The cardinal growth temperatures were min. 7°C, optimum 25 to 27°C, and max. 32°C. The isolates were homothallic and produced on CA colorless globose oogonia ranging from 25.4 to 36.4 µm (n = 40) in diam. Oospores were slightly aplerotic and measured (n = 40) 22.5 to 31.9 µm in diam., with a 0.9 to 1.5 µm thick wall. The antheridia were predominantly paragynous and averaged 11.5 × 9.9 µm (height × width, n = 40). Noncaducous sporangia were obpyriform, ovoid, elongated to irregular and semipapillate, sometimes bipapillate and measured (n = 40) 31.4 to 73.4 × 17.8 to 32.1 µm, and the L:B ratio was 1.9 to 2.0. Chlamydospores and hyphal swellings were not observed. The morphological characteristics resembled those described for P. occultans (Man in't Veld et al. 2015). The isolates were deposited in the Czech Collection of Phytopathogenic Oomycetes (CCPO) under accession nos. 551.11, 1158.20, 1176.21, 1201.21, 1218.21, 1236.21 and 1261.22. For molecular identification, the internal transcribed spacer (ITS) region, cytochrome oxidase subunit 1 gene (COX1), and translation elongation factor-1α (EF) gene from all isolates were amplified and sequenced using the primer pairs ITS4/ITS5 (White et al. 1990), COXF-CIT/COXR-CIT (Man in't Veld et al. 2015), and ELONGF1/ELONGR1 (Kroon et al. 2004), respectively. The resulting sequences of representative isolates P1158.20 and P1176.21 were deposited in GenBank (accession nos. MW750576 and OP326036 for ITS, ON862131 and OP313505 for COX1 and MW762616 and ON862132 for EF). BLASTn searches of GenBank, using the partial ITS, COX1, and EF sequences, revealed 100, 100, and 99% sequence identity, respectively, to P. occultans ex-holotype culture CBS101557 accessions JX978155, JX978156 and KF650770 (Man in't Veld et al. 2015). Concatenated sequences of the three genes were used to conduct a phylogenetic analysis using the maximum likelihood method in MEGA 11 (Tamura et al. 2021). The isolates were identified as P. occultans based on morphology and a multigene phylogenetic analysis. Koch´s postulates were confirmed by a soil infestation test. Healthy 2-year-old B. sempervirens plants were inoculated (9 plants per isolate and control, isolates no. 1158.20, 1176.21, 1261.22) with three 5-mm-diam. V8A mycelial plugs by inserting into the substrate near the collar. Control plants were treated with sterile agar plugs. All plants were kept in a greenhouse at 25°C and exposed to 24 h of flooding up to collar once a week. All inoculated plants showed wilting, collar lesions and root rot occurred after 21 days, while control plants remained healthy. The pathogen was reisolated from infected plants and confirmed by molecular identification. P. occultans was found for the first time in 1998 on Buxus sempervirens in the Netherlands and later in Belgium, the United Kingdom, Germany and Romania (Man in´t Veld et al. 2015, Nechwatal et al. 2014), as well as in the USA (Reeser et al. 2015, Gitto et al. 2018). This is the first report of P. occultans in the Czech Republic. This pathogen likely poses another significant threat to boxwood cultivation in addition to the previously invaded Cydalima perspectalis and Calonectria pseudonaviculata.
Summary In 2015 and 2016, the North American maple tree pathogen Eutypella parasitica was identified in Bohemian and Polish Silesia. To date, the pathogen has been recorded in 35 locations over an area of approximately 400 km2. It has been found primarily in natural stands in Silesia in several types of ravine and alluvial forests, in other natural or commercial forests, in riparian stands and in open landscapes. The proportion of diseased maples ranged between approximately 1% and 50% in certain locations. Acer pseudoplatanus was confirmed as the main host but infections were also detected on A. platanoides and A. campestre. E. parasitica damages the most valuable sycamore timber and represents a clear risk for maple cultivation in the region.
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