Japanese Oak Wilt Research Articles

Characteristics of Initial Damage Sites of Japanese Oak Wilt Disease Vectored by Platypus quercivorus (Murayama).

Characteristics of Initial Damage Sites of Japanese Oak Wilt Disease Vectored by <i>Platypus quercivorus</i> (Murayama).

Mortality due to Japanese oak wilt disease and surrounding forest compositions.

Japanese oak wilt (Raffaelea quercivora) is a vector-borne disease transmitted by the flying ambrosia beetle, Platypus quercivorus, and causes mass mortality in the fagaceous species of Japan. The data described in this article are available in Mendeley Data, DOI: 10.17632/xwj98nb39r.1 [1] and include the mortality status of 1089 Quercus crispula and 846 Quercus serrata trees and surrounding forest conditions. The findings using this dataset were published in M. Oguro, S. Imahiro, S. Saito, T. Nakashizuka, Relative importance of multiple scale factors to oak tree mortality due to Japanese oak wilt disease, For. Ecol. Manag. (2015) doi:10.1016/j.foreco.2015.07.016 [2].

Relative importance of multiple scale factors to oak tree mortality due to Japanese oak wilt disease

Although landscape structure is known to affect the transmission and occurrence of tree diseases, relatively little is known about the scale dependency of these relationships. Japanese oak wilt (Raffaelea quercivora) is a vector-borne disease transmitted by the flying ambrosia beetle, Platypus quercivorus, and causes mass mortality in the fagaceous species of Japan. In this study, we examined the impact of stand and landscape factors on the mortality of Quercus crispula and Quercus serrata trees at a radius of up to 1000m, to evaluate the relative importance of these factors that operate at different spatial scales. Of the factors considered, stand-level density, i.e., the total basal area of the host species within a 10m radius, had the highest importance values for mortality. However, other stand-level factors such as the density of non-host species and individual tree size did not have substantial effects on mortality. In addition, landscape factors assessed within a 1000m radius of target trees had a greater impact on mortality than those assessed within a 100m radius. These patterns might be a reflection of the transmission mode of the disease. Because the spatial scale at which a disease responds differs among diseases, studies examining the relationship between landscape factors and diseases must take multiple spatial scales into consideration.

살균제 나무주사를 이용한 참나무 시들음병 방제 효과

참나무 시들음병(병원균 Raffaelea quercus-mongolicae)은 2004년 국내에 처음 발견되어 그 피해가 증가하고 있는 추세이다. 이번 연구에서는 참나무 시들음병 방제를 위한 나무주사용 살균제를 선발하기 위해 실내시험과 포장시험을 실시하였다. 실내검정에서는 10종의 살균제와 1종의 항생제를 이용하여 국내균주 R. quercus-mongolicae와 일본균주 R. quercivora에 대한 생육억제효과를 조사하였다. 국내균주에 대해서는 chlorothalonil, benomyl, propiconazole 순으로 생육억제효과가 높게 나타났으며, 일본균주에 대해서는 propiconazole, benomyl, bitertanol 순으로 나타났다. 국내균주와 일본균주에 대하여 실내 항균효과가 우수하였던 약제 중 침투이행성이 우수한 propiconazole을 이용하여 약제방제 포장시험을 실시하였다. 그 결과 나무주사 처리 당해 연도 방제효과는 87.5%, 처리 다음 연도 방제효과는 66.7%까지 나타나 약제처리 효과는 적어도 1년 이상이었다. Oak wilt caused by Raffaelea quercus-mongolicae was first noticed in South Korea in 2004 and, ever since, its distribution and damage have been increasing. To screen a fungicide effective for oak wilt control by tree injection, laboratory and field experiments were conducted. Ten fungicides and one antibiotic were examined in vivo for their effectiveness in restricting the growth of R. quercus-mongolicae and R. quercivora (Japanese oak wilt pathogen) isolates. To the Korean isolates of R. quercus-mongolicae, chlorothalonil showed the highest fungicidal effects, followed by benomyl and propiconazole. To the Japanese one, propiconazole was highest in the fungicidal effectiveness, followed by benomyl and bitertanol. Propiconazole was selected for field-testing of its control efficacy because it showed good fungicidal effects in vitro and systemic activity. The control efficacy in the field was 87.5% in the first year of injection and 66.7% in the second year, indicating the fungicidal effects last at least over one year.

Genotype distribution of Raffaelea quercivora in the oak galleries and its composition in the mycangia of Platypus quercivorus

SummaryRaffaelea quercivora is the pathogenic fungus that causes Japanese oak wilt. The female monogynous ambrosia beetle, Platypus quercivorus, carries this fungus in mycangia on the pronotum. These beetles bore galleries in oak trees with their partners to produce offspring, and they deposit fungus on the gallery walls from their mycangia. The offspring mature in the gallery, before loading the fungal pathogen and flying from the gallery to other healthy trees. To investigate the unloading and loading modes of the fungus within the gallery, we developed four polymorphic microsatellite markers for R. quercivora and identified the fungal genotypes in the galleries and mycangia of the beetles. Small wood chips were sampled at 5–10‐mm intervals from the walls of five galleries in a dead Quercus serrata tree. The pronota were also sampled from five female adult beetles. The genotypes of the R. quercivora isolates from the wood chips and pronota were identified using the microsatellite makers. The genotypic analysis showed that each gallery was inhabited patchily by 5–10 genotypes of R. quercivora, and the mycangia of each beetle contained 3–6 genotypes. These results indicate that diverse R. quercivora genotypes are unloaded repeatedly from the mycangia of female beetles onto the gallery wall, which results in their patchy distribution on the walls. When the offspring leave the host tree, the fungal clones that proliferate in the walls are also loaded repeatedly into the mycangia of the mature beetles.

Decline of Quercus crispula in abandoned coppice forests caused by secondary succession and Japanese oak wilt disease: Stand dynamics over twenty years

Most coppice forests in Japan were abandoned in the 1960s for socio-economic reasons. In the last two decades, Quercus crispula and Quercus serrata, the main species in Japanese coppice forests, have suffered mortality from Japanese oak wilt disease (JOW) vectored by the ambrosia beetle Platypus quercivorus. To clarify forest changes due to secondary succession and JOW in abandoned coppice forests, stand dynamics over 23–26years in 16 permanent plots in Toyama Prefecture, central Japan, were analyzed. Seven plots were beech–oak stands dominated by Fagus crenata and Q. crispula, and nine were oak stands dominated by Q. crispula (in five plots) and/or Q. serrata (in six plots). In beech–oak stands before the appearance of JOW, dominance of shade-tolerant F. crenata increased and that of less shade-tolerant Q. crispula decreased in all seven plots, as expected from process of secondary succession. Since 2005 when the incidence of JOW became noticeable, Q. crispula suffered high mortality rates, and basal area in 2013 decreased compared with the first measurement (1987–1990) in all 12 plots. In contrast, JOW had less impact on Q. serrata because of its low mortality rates with JOW. In beech–oak stands, F. crenata expanded in dominance because of secondary succession and subsequent JOW, and stands will develop into old-growth beech forests over the long term. In oak stands, shade-tolerant canopy species under dead oak trees, such as Acer sieboldianum, are expected to replace dead oak trees, but understory species might also increase and slow the growth of saplings and seedlings of canopy tree species. Regeneration of oak was inferred to be difficult. JOW had a large negative impact on Q. crispula dynamics in abandoned coppice forests at a regional scale, and severely damaged oak stands will become heterogeneous forests composed of various species and ages, unlike the even-aged and rather monospecific oak coppice stands.

Discoloration induced by Raffaelea quercivora isolates in Quercus serrata logs and its relation to phylogeny: a comparison among isolates with and without the Japanese oak wilt incidence including outside of Japan

Japanese oak wilt (JOW) has been prevalent in Japan since the late 1980s. Infections of the fungus, Raffaelea quercivora Kubono et Shin. Ito, which is transmitted by an ambrosia beetle [Platypus quercivorus (Murayama)], can cause JOW. Although R. quercivora, P. quercivorus, and oak trees are distributed in other Asia–Pacific countries, the incidence of JOW has not been reported outside Japan. In this study, we collected R. quercivora isolates from 5 Asian countries, including Japan, and compared their ability to induce sapwood discoloration by inoculating Q. serrata logs. The tangential widths of the discoloration in sapwoods inoculated with non-Japanese isolates were equivalent to or greater than those of the 2 Japanese isolates. This indicates that a lack of JOW incidence outside Japan is not because of the lowered ability of R. quercivora to spread discoloration compared with the Japanese isolates. Statistical analyses of the relationship between discoloration and phylogeny based on DNA sequences of actin and chitin synthase showed that the discoloration width was independent of phylogenetic relatedness among the isolates. To discuss why the occurrence of JOW has not been reported outside Japan, further studies (e.g., on host susceptibility and P. quercivorus aggression) throughout Asia are needed.

A New Cytosporone Derivative from the Endophytic Fungus Cytospora sp

Japanese oak wilt (JOW) is a tree disease caused by the fungus Raffaelea quercivora, which is vectored by the ambrosia beetle, Platypus quercivorus. In a screening study of the inhibitory active compounds from fungi, a new cytosporone analogue, compound 1, was isolated from the endophytic fungus Cytospora sp. TT-10 isolated from Japanese oak, together with the known compounds, integracin A (2), cytosporones N (3) and A (4). Their structures were determined by extensive 1D- and 2D-NMR spectroscopic and mass spectral analyses. Compound 1 was identified as 4,5-dihydroxy-3-heptylphthalide and named cytosporone E. Compounds 2 and 3 showed antimicrobial activity against Raffaelea quercivora.

Detection of ambrosia beetles using a pan-sharpened image generated from ALOS/AVNIR-2 and ALOS/PRISM imagery

Aim of study: The ambrosia beetle, Platypus quercivorus, is a vector of Japanese oak wilt, which causes massive mortality of oak trees in Japan. ALOS/AVNIR-2 true color images can be used to help detect areas of oak wilt, although such detection by inventory surveys is not realistic. Applying pan-sharpening techniques, a higher spatial resolution multispectral image can be generated from lower-resolution multispectral images and higher-resolution panchromatic images. In this study, some pan-sharpening algorithms were considered and evaluated for the detection of damage points.Area of study: The oak forests in Kanazawa prefecture, Japan.Materials and methods: The ALOS/AVNIR-2 and ALOS/PRISM sensors were used. The pan-sharpening algorithms adopted were: Brovey transformation, Modified IHS transformation, Wavelet transformation, Ehlers fusion and High Pass Filter Resolution Merge. Four types of quantitative spectral analyses and visual detection were conducted to evaluate these algorithms.Main results: The Brovey transformation was the most useful algorithm to detect damage points, although it had an issue with the preservation of spectral characteristics.Research highlights: The detection rate of damage points was improved in 50% by applying the Brovey algorithm to a 10 m panchromatic image and 62.5 m multispectral image.Key words: ambrosia beetle; oak wilt; pan-sharpening; satellite imagery; visual detection.

The effect of modified prevention methods against Japanese oak wilt and the spreading of wilt-affected area in Chita Peninsula

The effect of modified prevention methods against Japanese oak wilt and the spreading of wilt-affected area in Chita Peninsula

The effect of stem density on the probability of attack by the ambrosia beetlePlatypus quercivorusvaries with spatial scale

The ambrosia beetle Platypus quercivorus uses fagaceous tree species as its hosts, and causes Japanese oak wilt by transporting and introducing the pathogenic fungus Raffaelea quercivora into the host tree. To protect fagaceous trees, it is necessary to understand the host selection process used by the beetle in heterogeneous forests. The occurrence of beetle attack on Quercus crispula and Castanea crenata was monitored from 2008 to 2011 in two 1-ha and one 0.5-ha plots established in a secondary forest. The stem and crown densities of each fagaceous tree species were calculated at 11 different spatial scales for each individual tree. Model application and selection were performed to clarify factors affecting the probability of attack by P. quercivorus. As shown in previous studies, a higher probability of attack was predicted for Q. crispula than for C. crenata, and the predicted probability of attack was lower for trees attacked in the previous year. The effect of stem density on the probability of attack was positive at a small (radius 5 m) spatial scale and negative at larger (radius 5–17.5 m) scales. We interpreted this to indicate that a dense distribution of fagaceous trees in a small area had a higher probability of attack, and that this probability decreased with an increasing density of fagaceous trees in a surrounding concentric area. A positive effect of crown density was detected, suggesting that P. quercivorus has a means of detecting host trees in areas with high crown densities of fagaceous species.

A hybrid pansharpening approach and multiscale object-based image analysis for mapping diseased pine and oak trees

We developed a multiscale object-based classification method for detecting diseased trees (Japanese Oak Wilt and Japanese Pine Wilt) in high-resolution multispectral satellite imagery. The proposed method involved (1) a hybrid intensity–hue–saturation smoothing filter-based intensity modulation (IHS-SFIM) pansharpening approach to obtain more spatially and spectrally accurate image segments; (2) synthetically oversampling the training data of the ‘Diseased tree’ class using the Synthetic Minority Over-sampling Technique (SMOTE); and (3) using a multiscale object-based image classification approach. Using the proposed method, we were able to map diseased trees in the study area with a user's accuracy of 96.6% and a producer's accuracy of 92.5%. For comparison, the diseased trees were mapped at a user's accuracy of 84.0% and a producer's accuracy of 70.1% when IHS pansharpening was used alone and a single-scale classification approach was implemented without oversampling the ‘Diseased tree’ class.

Antifungal Activity of a Polyacetylene against the Fungal Pathogen of Japanese Oak from the Liquid Culture of the Edible Mushroom, Hypsizygus marmoreus

Three polyacetylene compounds, 1, 2 and 3, have been isolated from the organic extract of a liquid culture of Hypsizygus marmoreus (Peck.) Bigelow (Japanese name: Bunashimeji). The structures of 1, 2 and 3 were determined by using spectroscopic methods. Compound 3 is new, and was identified as 8(E)-decene-4,6-diyn-1,2,10-triol. Compound 1 exhibits antifungal activity against the pathogenic fungus Raffaelea quercivora responsible for Japanese oak wilt

Extent of Japanese oak wilt damage in the Rokko mountains - Approach to the remote sensing technique to assess the extent of the damage -

Extent of Japanese oak wilt damage in the Rokko mountains - Approach to the remote sensing technique to assess the extent of the damage -

Effects of vaccination to host trees on the behavior and reproduction of the vector insects of Japanese oak wilt

Effects of vaccination to host trees on the behavior and reproduction of the vector insects of Japanese oak wilt

The expanding pattern of Japanese Oak Wilt for 4 years at Mt. Yoshida in Kyoto

The expanding pattern of Japanese Oak Wilt for 4 years at Mt. Yoshida in Kyoto

The effect of prevention activity for Japanese oak wilt in Chita Peninsula (III)

The effect of prevention activity for Japanese oak wilt in Chita Peninsula (III)

Virulence of Raffaelea quercivora isolates inoculated into Quercus serrata logs and Q. crispula saplings

This study was conducted to compare the virulences of various isolates of Raffaelea quercivora—a fungus that causes Japanese oak wilt disease—towards Japanese oak trees. Five isolates were collected from a wide range of Japan and inoculated into Quercus serrata logs and Q. crispula saplings. The tangential length of the discolored sapwood in the Q. serrata logs differed significantly among the isolates. The trend in isolate virulence was similar for the Q. serrata logs and the Q. crispula saplings. This is the first report suggesting that there is variability in virulence among isolates of R. quercivora.

Reestablishing the health of secondary forests Satoyama endangered by Japanese oak wilt: A preliminary report

Japanese oak wilt caused by the fungus Raffaelea quercivora is increasing in secondary forests known as Satoyama that are surrounding rural communities. Oak wilt is occurring in stands that are 40 to 70 years old that have been used for fuel wood and charcoal production and then left unmanaged because those wood fuels were replaced with gas and kerosene since 1950s. An ambrosia beetle, Platypus quercivorus, which vectors the pathogen, can propagate effectively in thicker trunks. Due to the extensive population growth of this beetle in aged “Satoyama” forests, the infested areas are increasing annually. A drastic change occurs in the vegetation after the mass mortality of oak trees. Deterioration of biodiversity and soil erosion are of concern. To reduce oak mortality, rejuvenation of trees will be effective because the vector beetle cannot propagate in thin trunks. We are conducting an experiment to reestablish the health of “Satoyama” forests that are slightly affected by this disease. In this experiment, aged forests were clear-cut to promote sprouting from the oak stumps. This is a coordinated effort among the local governments and researchers. The management of the “Satoyama” combined with the utilization of biomass as fuel wood in the local area is essential for the success of this project. Key words: Oak, wilt, Raffaelea quercivora, biomass, management.

Taxonomic reevaluation of Raffaelea quercivora isolates collected from mass mortality of oak trees in Japan

In this study, we reevaluated isolates of Raffaelea quercivora associated with Japanese oak wilt in Japan to clarify their taxonomy and to help researchers diagnose the cause of the mass mortality of oak trees in Asian countries more accurately. We examined the morphological and molecular characteristics of 15 isolates of R. quercivora, including an ex-holotype strain, obtained from a wide range of areas of Japan. Light microscopy showed that all the isolates had wider ranges of conidial and conidiophore sizes than previously recognized, but that their sizes and shapes did not differ among the isolates. A phylogenetic tree generated from sequences for a partial large subunit of ribosomal DNA showed that the new isolates and the ex-holotype formed a single clade within the Raffaelea clade, with a high bootstrap value. Scanning electron microscopy revealed multimodal conidial development in the isolates: sympodial or annellidic-percurrent proliferation or both, with delayed secession. These results suggest that the isolates examined and the ex-holotype strain have a different genetic identity from other known Raffaelea species. The diverse conidiogenesis and subtle characteristics in the conidium morphology of R. quercivora reflected in the emended description.