Severe Dieback Research Articles

Distribucion, incidencia y severidad de la muerte descendente (Lasiodiplodia spp.) en lima persa en Morelos, Mexico

Se determinó la distribución, incidencia y severidad de la muerte descendente (<em>Lasiodiplodia</em> spp.) en lima persa (<em>Citrus latifolia</em>) en 46 huertos de seis años de edad, 25 árboles por huerto en los municipios de Amacuzac (7 huertos), Ayala (4), Coatlán del Río (9), Cuautla (1), Jantetelco (5), Jonacatepec (1), Puente de Ixtla (5), Tepalcingo (3) y Tlaltizapán de Zapata (11), del estado de Morelos, México. La incidencia fue determinada con base al número de plantas enfermas y la severidad mediante escala de daño de cuatro clases: 0= árbol sano, 1= exudación de goma, 2= agrietamiento con exposición de tejidos internos y 3= cancro bien definido y muerte descendente de ramas. La severidad fue transformada a porcentaje de infección con la fórmula de Townsend y Heuberger, analizados por Kruskal Wallis y separados por la comparación de medias, prueba de Tukey (?= 0.05) y p< 0.0001 en incidencia y severidad. La enfermedad se registró en el 78% de los huertos, con incidencias de 31.8 a 100% y severidades de 30.0 al 100%. Los huertos con menor incidencia y severidad fueron los ubicados en Amacuzac, Ayala, Coatlán del Río y Tlaltizapán de Zapata.

Phytophthora species associated with dieback of sweet chestnut in Western Turkey

AbstractSweet chestnut (Castanea sativa) is an important tree species in the Marmara and Aegean regions of Turkey as these two regions produce the great majority of edible nuts, especially those used for marron glacé production. Chestnut forests and orchards in these regions showing severe dieback symptoms not associated with chestnut blight were investigated to determine the role of Phytophthora spp. in the decline syndrome. Soil samples were collected from around 108 symptomatic chestnut trees at 29 sites and Phytophthora spp. isolated using soil baiting technique and selective medium. Species isolated were identified by cultural characteristics and ITS sequencing. Phytophthora x cambivora was the dominant species detected in 13 sites, followed by P. cinnamomi (5 sites), P. plurivora (3 sites) and P. cryptogea (1 site). Phytophthora x cambivora was present in both regions, while P. cinnamomi was found only in the Marmara region in coastal areas around Istanbul. When inoculated at the stem bases of 3‐year‐old chestnut saplings, P. cinnamomi produced significantly longer necrotic lesions (7.8–12.0 cm) than P. x cambivora (2.6–6.3 cm) by 12 days after inoculation. Phytophthora plurivora was the least aggressive species causing only small lesions. Phytophthora cryptogea, which represents the first record on chestnut in Turkey, produced intermediate sized lesions in between P. x cambivora and P. plurivora. These results indicate that P. x cambivora and in some areas P. cinnamomi play major roles in the observed dieback of sweet chestnut in western Turkey.

Cytospora elaeagnicola sp. nov. Associated with Narrow-leaved Oleaster Canker Disease in China

Cytospora is a genus including important phytopathogens causing severe dieback and canker diseases distributed worldwide with a wide host range. However, identification of Cytospora species is difficult since the currently available DNA sequence data are insufficient. Aside the limited availability of ex-type sequence data, most of the genetic work is only based on the ITS region DNA marker which lacks the resolution to delineate to the species level in Cytospora. In this study, three fresh strains were isolated from the symptomatic branches of Elaeagnus angustifolia in Xinjiang Uygur Autonomous Region, China. Morphological observation and multi-locus phylogenetic analyses (ITS, LSU, ACT and RPB2) support these specimens are best accommodated as a distinct novel species of Cytospora. Cytospora elaeagnicola sp. nov. is introduced, having discoid, nearly flat, pycnidial conidiomata with hyaline, allantoid conidia, and differs from its relatives genetically and by host association.

Agrometeorological Analysis on the Freeze Damage Occurrence of Yuzu Trees in Goheung, Jeonnam Province in 2018

In 2018, severe diebacks have occurred on yuzu trees cultivated in Goheung, Jeonnam Province. On-farm surveys at 18 randomly selected orchards revealed the dieback incidence ranged from 7.5% to 100% with an average of 43.6%, and 56.6% of the affected yuzu trees were eventually killed. In order to find the reason for this sudden epidemic, we investigated the weather conditions that are exclusively distinct from previous years, hypothesizing that certain weather extremes might have caused the dieback epidemic on yuzu trees. Since different temperatures can cause freeze damage to plants depending on their dormancy stages, we investigated both periods when yuzu becomes hardy under deep dormancy (January-February) and when yuzu loses its cold hardiness (March-April). First, we found that daily minimum air temperatures below -10°C were recorded for 7 days in Goheung for January and February in 2018, while no occasions in 2017. In particular, there were two extreme temperature drops (-12.6°C and -11.5°C) beyond the yuzu cold hardiness limit in 2018. In addition, another occasion of two sudden temperature drops to nearly 0°C were occurred right after abnormally-warm-temperature-rises to 13°C of daily minimum air temperatures in mid-March and early April. In conclusion, we estimated that the possible damages by several extreme freeze events during the winter of 2018 could be a major cause of severe diebacks and subsequently killed the severely affected yuzu trees.

Predicting ash dieback severity and environmental suitability for the disease in forest stands

ABSTRACTAsh dieback, caused by the ascomycete fungus Hymenoscyphus fraxineus, has been rapidly expanding across Europe during the last two decades, posing a considerable threat to native ash populations. In this study, we applied regression-based models trained by field data, in conjunction with geographic information systems, to produce spatial predictions of ash dieback severity and environmental suitability for the disease in Czech forests. A model of actual ash dieback severity relates disease extent to silvicultural and environmental characteristics of forest stands and their neighbourhood, while a model of environmental suitability for the disease quantifies the relative susceptibility of sites to the disease, independent of the current silvicultural characteristics. The final predictive maps suggested that fertile lowlands and humid areas bordering Poland and Slovakia were the most endangered regions. Areas at the lowest risk of damage were concentrated in dry areas and in highland and mountain areas in the western part of the country, usually with poor soils on acid bedrock. Predictions of actual disease severity are an effective tool for guiding the current management of infested stands whereas predicting environmental suitability is useful for making long-term strategic decisions, e.g. identifying areas where future ash regeneration and cultivation may be unsuccessful.

Investigation on Zagros forests cover changes under the recent droughts using satellite imagery

Oak decline phenomenon has recently led to considerable dieback within Zagros forests, western Iran. In the present study, Landsat imagery (2005 to 2016) and synoptic station data were used to study the forest dieback in Dorood, Lorestan province. Sixteen vegetation indices were calculated and values in each year were obtained. The correlations between the index and climatic parameters of rainfall, temperature and relative humidity were investigated. Results showed that the correlation of some indices with rainfall and the correlation of other indices with temperature were more than 70%. Optimized soil adjusted vegetation index had 80% correlation with annual rainfall and the modification of normalized difference water index was correlated with average annual temperature by 75%. Using the numerical value changes of the indices, a map of forest cover change was prepared in four classes; healthy, weak, moderate and severe dieback and the process of its change were compared with the trend of variations in regard with rainfall values in the study period. There was a close relationship between changes in the area of forest cover dieback and rainfall and temperature values.

Fusarium equiseti is associated with the wilt and dieback of Aquilaria malaccensis in Northeast India

AbstractAquilaria malaccensis, categorized by IUCN as globally vulnerable, is in high demand in the Middle East and Asian markets for its unique resinous agarwood. In August 2015, symptoms of dieback were observed on A. malaccensis trees planted in the Medicinal and Aromatic Plant Garden, Panbari, Golaghat of the Assam Forest Department. The entire crowns of 70 trees showed complete leaf loss and severe dieback. Rotting at the collar region and of roots was also observed. Isolation from the infected roots consistently yielded Fusarium equiseti identified following standard laboratory procedures and analysis of the internal transcribed spacer (ITS) sequence of the ribosomal DNA. Symptoms of wilt, dieback and root rot were observed on 5‐month‐old Aquilaria seedlings 25 days after inoculation with the isolated fungus. This paper is the first report of F. equiseti causing wilt and dieback of A. malaccensis.

Impact of fungal diseases on common box (Buxus sempervirens L.) vegetation in Turkey

In recent years, severe dieback of boxwood (Buxus sempervirens) has been observed in the many forests in Turkey. In this study, boxwood diseases were investigated in the forests and nurseries in the Marmara and Black Sea regions of Turkey. Nurseries and boxwood forests in the above-mentioned regions were visited and leaf, branch, and soil samples were collected from symptomatic plants. Eleven fungal genera were isolated from the samples and identified based on morphological characteristics and sequencing of the ITS region and other barcoding loci. The box blight pathogen, Calonectria pseudonaviculata sensu stricto was most frequently isolated from declining boxwood both in the forest and nurseries. When tested on detached box shoots, C. pseudonaviculata was also the most aggressive pathogen on both wounded and intact leaves. Pseudonectria buxi (anamorph Volutella buxi) caused weak symptoms but only on wounded leaves. Pestalotiopsis asiatica and Gnomoniopsis smitovilgyi also caused necrosis on young shoots and yellowing on leaves. Phytophthora nicotianae was detected in one nursery while P. plurivora in two and P. occultans in one locations in the forests in the Black Sea region. The findings show that the boxwood decline in Black Sea region of Turkey is mainly caused by C. pseudonaviculata but other pathogens may also play a role in the decline. Commonly grown boxwood varieties; B. sempervirens ‘Osmanli’, B. microphylla ‘Variegata’ and B. microphylla ‘Faulkner’ were found susceptible against box blight alone and mixed infections with Volutella blight while B. sempervirens ‘Rotundifolia’ was tolerant. These box varieties showed similar reactions against Phytophthora spp.

Molecular phylogeny of Cytospora species associated with canker diseases of fruit and nut crops in California, with the descriptions of ten new species and one new combination

Cytospora species are destructive canker and dieback pathogens of woody hosts in natural and agroecosystems around the world. In this genus, molecular identification has been limited due to the paucity of multi-locus sequence typing studies and the lack of sequence data from type specimens in public repositories, stalling robust phylogenetic reconstructions. In most cases a morphological species concept could not be applied due to the plasticity of characters and significant overlap of morphological features such as spore dimensions and fruiting body characters. In this study, we employed a molecular phylogenetic framework with the inclusion of four nuclear loci (ITS, translation elongation factor 1-alpha, actin, and beta-tubulin) to unveil the biodiversity and taxonomy of this understudied important genus of plant pathogens. Phylogenetic inferences based on 150 Californian isolates revealed 15 Cytospora species associated with branch and twig cankers and dieback of almond, apricot, cherry, cottonwood, olive, peach, pistachio, plum, pomegranate, and walnut trees in California. Of the 15 species recovered in this study, 10 are newly described and typified, in addition to one new combination. The pathogenic status of the newly described Cytospora species requires further investigation as most species were associated with severe dieback and decline of diverse and economically important fruit and nut crops in California.

Drought-Affected Populus simonii Carr. Show Lower Growth and Long-Term Increases in Intrinsic Water-Use Efficiency Prior to Tree Mortality

The Three-North Shelter Forest (TNSF) is a critical ecological barrier against sandstorms in northern China, but has shown extensive decline and death in Populus simonii Carr. in the last decade. We investigated the characteristics—tree-ring width, basal area increment (BAI), carbon isotope signature (13Ccor), and intrinsic water-use efficiency (iWUE)—of now-dead, dieback, and non-dieback trees in TNSF shelterbelts of Zhangbei County. Results from the three groups were compared to understand the long-term process of preceding drought-induced death and to identify potential early-warning proxies of drought-triggered damage. The diameter at breast height (DBH) was found to decrease with the severity of dieback, showing an inverse relationship. In all three groups, both tree-ring width and BAI showed quadratic relationships with age, and peaks earlier in the now-dead and dieback groups than in the non-dieback group. The tree-ring width and BAI became significantly lower in the now-dead and dieback groups than in the non-dieback group from 17 to 26 years before death, thus, these parameters can serve as early-warning signals for future drought-induced death. The now-dead and dieback groups had significantly higher δ13Ccor and iWUEs than the non-dieback group at 7–16 years prior to the mortality, indicating a more conservative water-use strategy under drought stress compared with non-dieback trees, possibly at the cost of canopy defoliation and long-term shoot dieback. The iWUE became significantly higher in the now-dead group than in the dieback group at 0–7 years before death, about 10 years later than the divergence of BAI. After the iWUE became significantly different among the groups, the now-dead trees showed lower growth and died over the next few years. This indicates that, for the TNSF shelterbelts studied, an abrupt iWUE increase can be used as a warning signal for acceleration of impending drought-induced tree death. In general, we found that long-term drought decreased growth and increased iWUE of poplar tree. Successive droughts could drive dieback and now-dead trees to their physiological limits of drought tolerance, potentially leading to decline and mortality episodes.

First Report of Boxwood Blight Caused by Calonectria pseudonaviculata in California.

Samples from 9-year-old boxwood (Buxus sempervirens ‘Suffruticosa’) plantings from a residential estate in San Mateo County were submitted to the California Department of Food and Agriculture Plant Pest Diagnostics Center Lab in December 2016. Partially to nearly completely defoliated plants were found in which many of the leaves had violet brown, water-soaked spots. Green stems that became gray and dry as the disease progressed had narrow, longitudinal black lesions. Within a few months, symptomatic plants were discovered throughout the estate, despite sanitation practices implemented to prevent the spread of disease. Hyaline conidia, which ranged from 47.5 to 62.5 × 4.0 to 6 μm (53.5 × 5.1 μm average), were zero to two septate and produced in slimy masses in the leaf spots and stem lesions. Pieces (4 mm³) of tissue were excised from the margins of the spots and lesions, surface sterilized in 0.6% NaOCl for 2 min, and placed onto one-half-strength acidified potato dextrose agar (APDA). Velvety brown colonies grew from the pieces, eventually producing a tan to reddish margin with a ring of white sporulating conidiophores. The internal transcribed spacer region of rDNA (White et al. 1990) and portions of the translation elongation factor 1-alpha (Hunter et al. 2006) and beta-tubulin genes (Crous et al. 1999) were amplified from extracted DNA from one isolate and the amplicons sequenced (GenBank accession nos. MH078193, MG930486, and MG905088). BLAST analysis of a portion of the beta-tubulin gene was 100% identical with a sequence of the Calonectria pseudonaviculata culture ex-type, isolate STE-U 3399 (KF815124). To confirm pathogenicity, conidia were collected by flooding 15-day-old sporulating cultures with sterile distilled water and inoculating three 3.79-liter potted B. sempervirens plants, approximately 30 cm tall, with 3 ml each of a spore suspension (7 × 10⁵ spores/ml). Plants were placed in a dew chamber at 20°C for 72 h and then in a growth chamber at 20°C with a 12-h photoperiod. After 6 days, gray to purple leaf spots with orange centers were seen on the plants, with a few branches beginning to defoliate. Plants sprayed with water as controls and kept under the same environmental conditions as the inoculated plants remained healthy. After 13 days, leafspots, black stem lesions, severe dieback, and defoliation were observed on all inoculated plants. C. pseudonaviculata was isolated on APDA from symptomatic tissue from all inoculated plants but was not recovered from the control plants. C. pseudonaviculata was first discovered in the United Kingdom in the mid-1990s and has been detected in New Zealand, Europe, Canada, and the United States on the eastern seaboard (Farr and Rossman 2018). Following this detection in San Mateo County, boxwood blight was found at three additional estates in two counties in northern California. The presence of boxwood blight has limited the planting options for affected estates and bordering properties. To date, the disease has not been found in commercial nurseries in California. The above average rainfall in northern California in the fall of 2016 through spring 2017 may have provided optimum conditions for spread of this disease.

First report of leaf blight and twig dieback caused by Mycoleptodiscus indicus on Ixora coccinea

Ixora coccinea (Rubiaceae), native to Eastern India is widely cultivated as an ornamental shrub and because its flowers, leaves, roots and stems contain phytochemicals with medicinal properties. In December, 2017, a severe foliar blight and twig dieback was observed in the gardens of Bidhan Chandra Krishi Viswavidyalaya, West Bengal. Disease incidence was up to 100% in some areas. Initial symptoms included small, reddish-brown lesions (Fig. 1a) on the leaf tip and leaf margin. Sporodochia were prevalent on both lower and upper leaf surfaces and occured singly and in clusters (Fig. 1b). The initial reddish-brown lesions enlarged and coalesced into large necrotic areas (Fig. 1c) giving rise to severe dieback due to abscission of infected leaves and flowers. (Fig. 1d). Great numbers of dark brown to black sporodochia were produced on necrotic leaf tissues. Under favourable conditions masses of hyaline, aseptate conidia were produced by conidiogenous cells. Infected leaf and twig samples were surface sterilised with 1.5% sodium hypochlorite for two minutes, plated on 2% (w/v) potato dextrose agar amended with chloramphenicol (0.5 mg/l) and incubated at 25°C under a 12 hr/12 hr light/dark cycle for seven days. Fungal growth from the material was cream coloured but yellowish when viewed from beneath (Fig. 2). Hyphae were septate, branched, brown to dark brown and 3-7.5 μm wide, and formed many clypeate, dark brown sporodochia consisting of compressed phialides which were ampulliform to doliiform or irregular in shape. The number of conidiogenous cells in a sporodochium varied widely and many sporodochia failed to produce conidia. The conidiogenous cells showed non-pigmented, circular, phialidic apertures. Conidia were few and were hyaline, aseptate, often guttulate and curved, with an apical setula measuring up to 3 μm long but rarely with a basal setula. Conidia (n=50) measured 10-16 μm x 4.5-7.0 μm. On the basis of conidial and cultural characteristics, the fungus was identified as Mycoleptodiscus indicus (Sutton, 4; Sutton & Hodges, 5). The identification was confirmed by molecular analysis of the 5.8S subunit and flanking internal transcribed spacers (ITS1 and ITS2) of rDNA amplified from DNA extracted from single-spore cultures with the ITS1/ITS4 primers (White et al., 6) and sequencing. The sequence obtained from present study (GenBank Accession No. MH479058) showed 99% identity with Mycoleptodiscus indicus isolate JSP05-02C3.1 (KR093950). Pathogenicity was tested by spraying a conidial suspension (1 × 106/ml) onto five needle-pricked young leaves and twigs; comparable inoculations were done with sterile water as a control. The procedure was repeated five times and inoculated plants were maintained in a controlled environment (25°C, 80-85% humidity with a 12 hr photoperiod). After 12-15 days all the inoculated leaves developed necrotic symptoms (Fig. 3a) similar to those observed on naturally infected leaves, whereas control leaves remained symptomless. Twig dieback symptoms developed ten days after inoculation (Fig. 3b). Re-isolation from the inoculated leaves and twigs consistently yielded M. indicus. Mycoleptodiscus indicus has previously been recorded as a plant pathogen (Ostazeski, 3; Alfieri et al., 1; El-Gholl & Alfieri, 2) but to the best of our knowledge, this is the first report of disease on I. coccinea caused by M. indicus.

Vulnerability and resilience of the carbon exchange of a subarctic peatland to an extreme winter event

Extreme winter events that damage vegetation are considered an important climatic cause of arctic browning—a reversal of the greening trend of the region—and possibly reduce the carbon uptake of northern ecosystems. Confirmation of a reduction in CO2 uptake due to winter damage, however, remains elusive due to a lack of flux measurements from affected ecosystems. In this study, we report eddy covariance fluxes of CO2 from a peatland in northern Norway and show that vegetation CO2 uptake was delayed and reduced in the summer of 2014 following an extreme winter event earlier that year. Strong frost in the absence of a protective snow cover—its combined intensity unprecedented in the local climate record—caused severe dieback of the dwarf shrub species Calluna vulgaris and Empetrum nigrum. Similar vegetation damage was reported at the time along ~1000 km of coastal Norway, showing the widespread impact of this event. Our results indicate that gross primary production (GPP) exhibited a delayed response to temperature following snowmelt. From snowmelt up to the peak of summer, this reduced carbon uptake by 14 (0–24) g C m−2 (~12% of GPP in that period)—similar to the effect of interannual variations in summer weather. Concurrently, remotely-sensed NDVI dropped to the lowest level in more than a decade. However, bulk photosynthesis was eventually stimulated by the warm and sunny summer, raising total GPP. Species other than the vulnerable shrubs were probably resilient to the extreme winter event. The warm summer also increased ecosystem respiration, which limited net carbon uptake. This study shows that damage from a single extreme winter event can have an ecosystem-wide impact on CO2 uptake, and highlights the importance of including winter-induced shrub damage in terrestrial ecosystem models to accurately predict trends in vegetation productivity and carbon sequestration in the Arctic and sub-Arctic.

Diversity of Phytophthora species in Valdivian rainforests and association with severe dieback symptoms

AbstractThe Valdivian rainforest, one of the global hotspots of biodiversity, is a temperate rainforest originating as a Tertiary relic from the supercontinent Gondwana. In November 2014, a survey of Phytophthora diversity was performed in 13 natural forest stands and 20 forest streams and rivers in two protected areas near Valdivia and in a temperate montane forest in the Concepción area. One planted stand each of the introduced tree species Castanea sativa and Fagus sylvatica were also included. Using baiting assays, eight described species and four previously unknown taxa of Phytophthora were isolated from 86% of the 50 rhizosphere soil samples from seven of the eight tree species sampled in 12 forest stands, and from 20 streams: P. chlamydospora, P. cinnamomi, P. kernoviae, P. lacustris, P. plurivora, P. pseudosyringae, P. ×cambivora, P. ×stagnum, P. valdiviana nom. prov. from Clade 2b, P. madida nom. prov. from Clade 8a, and P. chilensis nom. prov. and P. pseudokernoviae nom. prov. The latter two species are the closest relatives of P. kernoviae from Clade 10. Phytophthora pseudokernoviae nom. prov. was also isolated from necrotic leaves of Drimys winteri. From the Valdivia river, a swarm of three Clade 6 hybrids was recovered. Each hybrid isolate resulted from multiple reticulation events with P. thermophila as maternal and both P. amnicola and P. chlamydospora as paternal parents. In addition, three previously unknown and recently described Nothophytophthora species, N. caduca, N. chlamydospora and N. valdiviana, were isolated from several forest streams. Phytophthora cinnamomi, the most common and widespread species in soils of native forests, was associated with severe dieback of Valdivian rainforest trees, in particular D. winteri, Luma apiculata, Nothofagus dombeyi and the endangered Saxegothaea conspicua. A first pathogenicity test demonstrated high aggressiveness of P. cinnamomi to several native tree species, including N. dombeyi, Blepharocalyx cruckshanksii and Gevuina avellana.

Evidence from mortality dating of Fraxinus excelsior indicates ash dieback (Hymenoscyphus fraxineus) was active in England in 2004–2005

Ash (Fraxinus excelsior L.) planted at six sites over the past 20 years was investigated. Three geographically isolated sites (Northumberland, Leicestershire and Devon) were compared with three sites in established areas of ash dieback in East Anglia, and the causal pathogen, Hymenoscyphus fraxineus, confirmed at all. Dieback severity, the frequency of stem basal lesions and pathogen apothecia, were quantified at all sites but despite high disease levels, tree mortality was low. Some trees had typical H. fraxineus stem cankers but had apparently died between 2001 and 2011, before the earliest UK records of H. fraxineus. Ring counts established beyond doubt the year of death and canker initiation in 27 dead trees. Cankers on the same trees were then tested for H. fraxineus using PCR-based detection, with pathogen presence confirmed as early as 2004/05 in some. This places H. fraxineus in England much earlier than previously thought, even pre-dating its documented arrival in neighbouring European countries. The advanced disease levels at some sites plus confirmation of H. fraxineus in old stem cankers, suggests that planting of infected H. fraxineus tree stock in England could date back to the early 1990s, with affected trees dying in the mid-2000s. Additionally, it raises questions about the origins of the infected plants and uncertainties about plant trade pathways.

Assessment of abiotic and biotic factors associated with eastern white pine (Pinus strobus L.) dieback in the Southern Appalachian Mountains

A novel and emerging eastern white pine (Pinus strobus L.) dieback phenomenon is occurring in the Southern Appalachian Mountains in the eastern United States. Symptomatic eastern white pine trees exhibit canopy thinning, branch dieback, and cankers on the branches and bole. These symptoms are often associated with the presence of a scale insect, Matsucoccus macrocicatrices Richards (Hemiptera: Matsucoccidae), and a fungal pathogen, Caliciopsis pinea Peck (Coryneliales: Coryneliaceae). We determined the extent, range, and severity of dieback of 2,061 eastern white pine trees from 40 sites in Georgia, North Carolina, South Carolina, Tennessee, Virginia, and West Virginia. We also evaluated associations between eastern white pine health and abiotic (aspect, elevation, latitude, precipitation, slope, and temperature) and biotic (eastern white pine basal area and density, relative stand density, and presence of C. pinea and M. macrocicatrices) factors. Our results indicate that trees ≥2.54 cm DBH had an average health rating of 3.57 (1 = healthy tree, 5 = dead tree), with 57% being in the 4–5 health rating groups. Eastern white pine dieback was positively associated with presence of C. pinea, and negatively associated with mean annual temperature and tree size. Sawtimber (≥22.86 cm) were healthier than poletimber (12.70–22.61 cm) and sapling sized trees (2.54–12.45 cm). Further, C. pinea incidence was positively correlated with eastern white pine density and M. macrocicatrices. The insect-pathogen complex was present in all six states and 80% of the sites. If eastern white pine dieback continues, effective management practices will be needed to conserve and maintain this economically and ecologically important pine species in the eastern United States.

Biological Control of Cryphonectria parasitica in Romanian Protected Sweet Chestnut Forests

Asiatic fungus Cryphonectria parasitica has gradually infected all chestnut habitats, forest and horticulture plantations from the most important natural centres of sweet chestnut distribution in Romania. The objectives of this work were to understand the destruction rate of chestnut habitats under C. parasitica pressure, and to test the efficacy of pathogen control in revitalizing these protected forests. Successive inventories of forest health status were carried out in forest districts of Maramures and Gorj counties. C. parasitica biologic control using CHV1 virus has been tested. The methodology includes standard laboratory and field work techniques: local hipervirulent strain identification and conversion to hipovirulence, field canker inoculation, and treatment efficacy evaluation. The fungus killed all mature chestnut trees in roughly two decades. Field inoculation has been successful on chestnut and sessile oak (fungus secondary host) in experimental plots from both target zones. This is the first time in Romania when a forest habitat is recovered by means of biological control, after a severe dieback of the old forest caused by a lethal invasive pathogen.

<b>Adventitious rooting of mature <I>Cycas micronesica</I> K.D. Hill (Cycadales: Cycadaceae) tree stems reveals moderate success for salvage of an endangered cycad</b>

Mature Cycas micronesica trees were among the forest trees that were destined to be removed from a 2012 construction site in northern Guam. Forty-nine of these trees were cut at the base and transported to nursery conditions to determine if adventitious root development could be stimulated as a means of saving the trees. Fungicide and auxin were applied to the base of each stem, and perlite was used as the container medium. A nursery maintained by an experienced cycad horticulturist yielded 41% survival, but half of the rooted plants exhibited severe stem dieback. A nursery maintained by general plant nursery specialists without cycad experience resulted in 100% mortality. If numerous caveats are acknowledged, whole-tree stem cuttings may yield moderate success for saving C. micronesica trees from construction sites when adequate resources are appropriated to support the nursery phase with experienced cycad biologists.

Ceratocystis platani is killing plane trees in Istanbul (Turkey)

SummaryCeratocystis platani was detected at several locations in the European side of Istanbul, causing severe dieback and mortality, mainly on Platanus × acerifolia imported from Italy approximately 160 years ago, but also on Platanus orientalis. In the work reported here, the causal agent of the dieback and mortality was identified based on morphological characteristics in culture and internal transcribed spacer (ITS) sequencing, confirming the presence of C. platani in Turkey. All analysed C. platani isolates from Istanbul shared the same ITS sequence with European C. platani strains available in the NCBI, but differed from other species previously ascribed to the Ceratocystis fimbriata species complex. Pathogenicity of C. platani was proven by inoculation onto 25‐cm‐long and 4–9 mm diam. P. orientalis twigs and the causal agent reisolated from symptomatic tissues. In a survey of 976 Platanus in streets and parks of Istanbul, 26.5% of trees showed symptoms of C. platani infections, whilst 5.6% were dead. The proportion of symptomatic trees was higher where management interventions, such as topping or pruning and felling infected trees had been carried out.

Quantitative Assessment of Grapevine Wood Colonization by the Dieback Fungus Eutypa lata.

Eutypa lata is a fungal pathogen causing severe dieback in vineyards worldwide. This fungus colonizes vines through pruning wounds, eventually causing a brown sectorial necrosis in wood as well as stunted vegetative growth. Several years may pass between infection and the expression of external symptoms, hindering the rapid evaluation of both grapevine cultivars susceptibility and E. lata variation in aggressiveness. We aimed to develop a rapid quantitative method for the assessment of wood colonization after inoculation of cuttings in controlled conditions. We used several grape cultivars varying in susceptibility in the vineyard and fungal isolates with different levels of aggressiveness to monitor wood colonization during a maximum period of 2 months. Re-isolation allowed demonstration of the effects of both cultivars and fungal isolates on the rate of wood colonization. We also developed a real-time PCR method that was efficient in measuring fungal biomass, which was found to be correlated with isolate aggressiveness based on foliar symptom severity. The real-time PCR approach appears to be a useful technology to evaluate grapevine susceptibility to E. lata, and could be adapted to other pathogens associated with grapevine trunk diseases.