Forest Pathology最新文献

During the summer of 2019, spots were detected on the leaves of black olive (Bucida buceras L.) trees distributed in urban areas in Los Mochis, Sinaloa, Mexico. Two single-spore isolates were obtained and identified as Colletotrichum siamense by phylogenetic analyses of concatenated sequences of the ITS, gapdh, tub2, act, chs-1 and gs genes. The pathogenicity of the isolates was demonstrated through inoculations under controlled conditions. This is the first report of C. siamense causing leaf spot of black olive in Mexico and worldwide.

Erysiphe species infecting oaks in North America are common and widespread, but compared to Asia and Europe, the taxonomy and phylogeny of North American species is unknown. The present study addresses this dispairity. Comprehensive multilocus phylogenetic analyses, including CAM, GAPDH, GS, ITS, RPB2 and TUB, revealed a high degree of co-evolution between North American oaks and the Erysiphe spp. that infect them. A concatenated multilocus tree and individual trees based on single loci revealed many highly supported species clades. The clades are formally named to conform with the current taxonomic classification. Available names, such as E. abbreviata, E. calocladophora and E. extensa, are associated with corresponding clades, and are newly circumscribed supported by ex-type sequences or, if not available, by the designation of epitypes with ex-epitype sequences. Erysiphe densissima is reintroduced for a clade that corresponds to the old name ‘E. extensa var. curta’. Eight new species are described, including Erysiphe carolinensis, E. gambelii, E. occidentalis, E. phellos, E. pseudoextensa, E. quercophila, E. quercus-laurifoliae and E. schweinitziana. A new diagnostically and taxonomically relevant trait associated with the anamorphs of North American Erysiphe species on oaks has been assssed. This is a special conidiophore-like lateral outgrowth of the superficial hyphae, comparable to ‘aerial hyphae,’ which are also known for species of the powdery mildew genus Cystotheca which also infect Quercus species.

Scotch broom (Cytisus scoparius) and French broom (Genista monspessulana) are two woody legumes native to Europe and North Africa that have become invasive in different countries around the world. In Chile, they are among the most serious invasive plants of the central southern regions, where they cause severe negative impacts to natural environments, and have become a serious problem in plantation forestry. Numerous studies have sought biological control agents for both species, however, this approach has not been explored in Chile. The aim of this study was to prospect for pathogens and diseases occurring in these weeds in invaded areas of Chile and explore these as potential biocontrol agents. Surveys were conducted in 13 invaded areas between the Biobio and Araucanía regions, and diseased plants of both species were collected for isolation. The putative pathogens isolated from each broom species were inoculated into healthy plants, and isolates producing symptoms identified by DNA sequencing. These isolates were used in pathogenicity tests on both weed species and on Pinus radiata and Eucalyptus globulus plants. The most aggressive pathogens were Fusarium sambucinum, F. solani and Phytophthora multivora on C. scoparius; Neofusicoccum parvum and Chondrostereum purpureum on both weeds, and F. tricinctum s.l. on G. monspessulana. Except for F. trincinctum s.l., all isolates caused lesions on both weeds, and except for P. multivora, all isolates caused lesions on E. globulus and/or P. radiata. Most pathogens on C. scoparius had been reported previously on this host elsewhere, while most pathogens on G. monspessulana represent novel associations.

Fine structures were investigated on Pinus thunbergii needles in the coastal area of Seocheon, Korea. Both asymptomatic and necrotised needles were collected and subjected to electron microscopy and X-ray microanalysis. Particles of varying sizes and shapes covered both the asymptomatic and necrotised needles. The ratio of clogged stomata to open stomata was significantly higher in necrotised needles. X-ray microanalysis revealed particles composed of aluminium, calcium and silicon. However, sodium chloride crystals were rarely observed. These results suggest that needle necrosis in pine species may be associated with stomatal clogging by aerosol particles.

Bacterial tree diseases have been mainly studied in agriculture and horticulture. For forest trees, damage due to bacterial diseases is understudied. Moreover, bacterial tree diseases often appear in the context of so-called complex diseases, which are dependent on other factors, such as multiple microorganisms, insects or abiotic factors which weaken the host. In recent years, outbreaks of bacterial tree diseases, such as Xylella fastidiosa in the Mediterranean region or acute oak decline (AOD) in the United Kingdom, raised the awareness of bacterial diseases on forest trees. In this review, we aim to summarise the current issues and available knowledge about bacterial diseases of forest trees in Central Europe. Furthermore, we identify potential bacterial pathogens that could gain importance in the future for central European forests. The methods used were a systematic literature search and the analysis of the data collected over the last 10 years on bacterial diseases by the Swiss forest protection service. We conclude that, on one side, complex bacterial diseases could increase in importance, especially considering ongoing climate change. Therefore, the bacterial community of diseased trees (the pathobiome) needs to be studied more in depth to understand the emergence of complex bacterial diseases. On the other side, host ranges of highly pathogenic invasive genera and species, such as Xylella, need to be investigated experimentally for common central European tree species and varieties, to implement proactive risk management strategies against bacterial diseases in forest trees. Finally, urban trees and green spaces should be monitored more closely, as they could serve as starting points for bacterial disease outbreaks in forests, similarly to other emerging diseases and pathogens.

This study investigated the severity of mistletoe infection on junipers and the relationship between tree characteristics, physiographic factors and mistletoe infection. The study was conducted in two protected areas: Parvar and Miankouh Tash in Semnan Province, Iran. A dwarf mistletoe-infested area of 400 ha was sampled by placing a 250 × 250 m grid over a map of each study area. A 20 × 20 m (400 m²) plot was placed at the intersection of grid lines. This resulted in a total of 110 forested plots: 45 plots in Parvar and 65 plots in Miankouh Tash. In each plot, all live junipers were measured for total height, crown area, collar diameter and crown diameter. Mistletoe severity was estimated using the 6-class dwarf mistletoe rating system (DMR). Dead trees were also recorded and examined for evidence of past mistletoe infection. The Boruta algorithm was used for feature selection, and the selected features were utilised for predicting DMR using a random forest (RF) model. Over 40% of junipers in the sample plots were infected and 7.5% were dead. Mortality was greater in severely infested plots compared to uninfested and lightly infested plots. The results of univariate analysis demonstrated that the largest trees across plots were more severely infected. Infection severity was highest on steep terrains (slopes more than 60%) where the largest junipers were growing. Based on Boruta feature selection algorithm, collar diameter, tree height and crown area of junipers have been detected as the most important variables for the explanation of infection severity. Crown diameter, geographical aspect, density of juniper trees, altitude and juniper canopy cover were classified as tentative variables in this model. Slope percentage beside two variables related to stand characteristics including all woody species (basal area and tree density) were the rejected variables. The correlation coefficient (r) and root mean square error (RMSE) between the predictions by RF and the measured DMR were 0.83 and 0.53 respectively. These results indicate that the selected environmental variables can be used for spatial prediction of DMR in both study areas. Because increased mortality was observed for severely infected areas, more efficient management methods are needed to control the dwarf mistletoe populations in the Alborz Mountains.

Oak decline is a major concern in Iran. A literature search with the terms ‘Iran’ AND ‘oak’ OR ‘Quercus’ from 1963 through 2023 resulted in 635 articles with over 200 dealing specifically with oak decline. In Iran, oak decline is most severe in the Zagros forests, followed by the Arasbaran and Hyrcanian forests. Of Iran's 11 native oak species, Quercus brantii is the most affected. Several factors have been identified as contributing to oak decline in Iran. Some economic and social factors include high rural unemployment, livestock overgrazing and uncontrolled cutting of live tree branches with the wood used for firewood and foliage used as food for farm animals. These pruning wounds can serve as entry points for pathogens and attract insects. Important abiotic factors included extended drought, increasing air temperature and wind speed, and increased levels of airborne dust and heavy metals. Important pathogens identified in the early 2000s included Armillaria mellea and charcoal rot fungus (Biscogniauxia mediterranea). More recently, many other fungal pathogens (e.g., Discula quercina, Neoscytalidium dimidiatum, Obolarina persica, Paecilomyces formosus and Phaeoacremonium tuscanicum) and bacterial pathogens (e.g., Bacillus pumilus, Brenneria goodwinii, Gibbsiella quercinecans, Rahnella victoriana and Stenotrophomonas maltophilia) were found in association with declining oaks. Among the insects, severe oak defoliation has resulted from various Lepidoptera in the families Erebidae, Geometridae and Tortricidae. Similarly, several bark- and wood-boring beetles in the families Buprestidae and Cerambycidae were reported from declining oaks, with the buprestid Agrilus hastulifer being one of the most common. It is hoped that this review will improve our understanding of the many factors involved in oak decline in Iran and promote the development of management strategies.

Using an infrared (IR) thermal camera, we evaluated the efficacy of six arboricultural materials for preventing sunscald and frost crack. The trunks of adult Yoshino cherry (Prunus × yedoensis) and Japanese zelkova (Zelkova serrata) were treated with (i–iii) three paint types (white water paint [P–W], white latex paint [P–L], and quicklime [P–Q]), (iv and v) two band wrap types [brown tree wrap (B–B) and white tree wrap (B–W)], and (vi) a wound paste: thiophanate-methyl paste (TP) in the shape of a band 10 cm thick. Outdoor IR thermographs were captured four times a day at 3 h intervals (09:00 a.m., 12:00 p.m., 03:00 p.m. and 06:00 p.m.) over four consecutive days in late October 2019. Bark temperatures recorded for P–W, P–L, P–Q and B–W treatments were consistently lower than those for untreated trunks. The mean temperature difference between B–W and untreated bark (up to 4.57°C) remained pronounced between 09:00 a.m. and 06:00 p.m. for both tree species each day. Conversely, no significant differences in bark temperatures were observed under B–B and TP treatments compared with untreated bark (p = 0.01). Elevated bark temperature was observed on the south side compared with the other three cardinal directions; however, temperatures were similar in all directions at 06:00 p.m. These findings suggest that white tree wrapping may provide a viable approach to prevent sun-induced trunk injuries, leveraging the light reflectivity of the white colour and thermal insulation properties of the wrapping material.