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A Mycena species new to science was obtained from moist chamber cultures of trunk bark of a living American elm tree (Ulmus americana) located in the Fort Worth Botanic Garden, Tarrant County, Texas. This discovery was part of an ongoing study of corticolous myxomycetes on larger American elm trees occurring in Fort Worth nature parks. More than 15 American elm trees were sampled for trunk bark but only a single tree yielded Mycena basidiomes. Collections of bark began in the summer of 2017 and continued until the beginning of 2020. Bark samples from the north, south and west side of the tree yielded fruit bodies of the mushroom in moist chamber culture. No fruit bodies were observed in nature nor were early formation stages on the underside of the bark. Crystals previously described in another study were present on the bark surfaces, edges, and undersides. Habit and morphological development were photographed using light microscopy applying multifocal imaging and computer stacking to increase depth of field. Basidiome development was observed and photographed from the earliest primordial beginning stage, the button stage, intermediate stage and the final emerging stalk elongation and mature cap formation stage. Mature mushroom development took from 9 to 21 days after wetting the bark in moist chamber cultures. Scanning electron microscopy was used to illustrate development of the button stage, emerging stalk and pileus stage, and the fully mature pileus, lamellae, and pseudocollarium. Morphological features and DNA sequence data confirmed that this Mycena species was undescribed and distinct from other Mycena taxa. Morphological features suggest placement of the novel taxon in Mycena sect. Viscipelles, distinct from other members based on morphological characters and phylogenetic analysis.

Fungicide injection is regularly performed to prevent and manage Dutch elm disease (DED) of American elm (Ulmus americana). In an effort to better understand the effects of long-term fungicide injection on tree health, sonic tomography (SoT) and electrical-resistance tomography (ERT) were used to nondestructively determine the incidence and severity of internal decay in the lower trunk of American elms in suburban and urban settings. Overall, 253 sonic and electrical-resistance tomograms were generated from 210 American elms. Sampled trees were partitioned into two fungicide injection groups: (1) regular injection; and (2) irregular injection or no known history of injection. Among all American elms, the incidence of internal decay in the lower trunk was 30% (63/210) with a mean percent decay, as determined by SoT, of 39%. Based on Chi-square analysis, there were no significant differences in the frequency of elms with decay by injection history (P = 0.799). Mean percent decay was significantly different by dbh class (P = 0.005) and while linear regression demonstrated a positive correlation between percent decay and dbh, most of the variability went unexplained (R2 = 0.182). For elms with decay, there was a significantly higher frequency of trees in the lowest decay class (< 25% of the cross section) compared to the highest decay class (> 75% of the cross section). The results suggest that the wounding associated with regular fungicide injection does not increase the likelihood of internal decay and that American elms exhibit a low frequency and severity of internal decay.

The apple tree is affected by a large variety of phytophagous plants. Woolly apple aphid in apple trees, Eriosoma lanigerum (Hausmann) (Hemiptera: Aphididae) are from North America. The main host of this insect is the plant Ulmus americana L. and the secondary host is the apple tree, where it develops throughout the year. Collects were carried out in pioneer municipalities in the planting of apple trees in the state of Espirito Santo, being cultivated Eva, Gala and Fuji varieties. The collections took place in the municipality of Santa Teresa, Santa Maria de Jetiba and Mantenopolis. Samples were taken at the stages of vegetative development and apple production. In this study, the occurrence of this insect was recorded in apple orchards in the state of Espirito Santo, where the presence of E. lanigerum was observed in all the samples, attacking the trunk, new shoots, roots, shoots and fruits between the planting lines.

A Licea species new to science is described on the bark surface of living American elm (Ulmus americana L.) cultured in moist chambers. It is characterized by an iridescent peridium on the sides of the sporangium, a black apical circular patch of globular debris, and dark reddish black spores that are smooth over half the surface and ridged-reticulate over the other half with the paler thinner wall collapsing into a coffee-bean shape. This combination of morphological characters is distinct and separates this taxon from all other species of Licea. The history of moist chamber culture use and field collection of corticolous myxomycetes is reviewed. The discovery of crystals of unknown origin on the bark surface of American elms associated with Licea species are illustrated with light microscope photography and scanning electron microscopy. Light microscope images and habit photographs were made using multi-focus imaging and computer stacking to increase depth of field and provide illustrations in color of sporangial structures of the new Licea species. This tiny short-stalked Licea approximately 100 um in height, and with distinctive external and internal morphological characters, was photographed using scanning electron microscopy. Dark-spored versus light-spored species of Licea are reviewed and compared with the most recent molecular analysis as this relates to the genus Licea. This paper is the first in a series that will document the discovery of Licea fruiting bodies of four new species on American elms in nature parks near Fort Worth, Texas.

American elm,Ulmus americanaL., was cultivated widely in USA and Canada as a landscape tree, but the genome of this important species is poorly characterized. For the first time, we describe the sequencing and assembly of the chloroplast genomes of two American elm genotypes (RV16 and Am57845). The complete chloroplast genome ofU. americanaranged from 158,935-158,993 bp. The genome contains 127 genes, including 85 protein-coding genes, 34 tRNA genes and 8 rRNA genes. Between the two American elm chloroplasts we sequenced, we identified 240 sequence variants (SNPs and indels). To evaluate the phylogeny of American elm, we compared the chloroplast genomes of two American elms along with seven Asian elm species and twelve other chloroplast genomes available through the NCBI database. As expected,Ulmuswas closely related toMorusandCannabis, as all three genera are assigned to the Urticales. Comparison of American elm with Asian elms revealed thattrnH was absent from the chloroplast of American elm but not most Asian elms; conversely,petB,petD,psbL,trnK, andrps16 are present in the American elm but absent from all Asian elms. The complete chloroplast genome ofU. americanawill provide useful genetic resources for characterizing the genetic diversity ofU. americanaand potentially help to conserve natural populations of American elm.

Evening Grosbeak (Coccothraustes vespertinus) populations have been hypothesized to be in steep decline across North America. Data characterizing long-term changes are needed to quantify the magnitude of the declines. We surveyed grosbeaks at a spring migratory stop-over site in Corvallis, Oregon, USA, where birds gather annually during April and May to feast on elm (Ulmus spp.) seeds before departing to breeding sites. An estimate produced by a statistics professor in the 1970s indicated peak numbers were 150,000 to 250,000 birds. Our surveys in 2013–2015 found annually variable numbers, from a few hundred grosbeaks in the lowest year to less than five thousand birds in the highest year. If the original estimate is approximately true, Evening Grosbeak numbers have experienced dramatic declines, averaging −2.6%/year, over the last four decades. Our local observation of declines during spring aligns with declines documented in winter across North America by bird feeder studies and in summer by the Breeding Bird Survey. We explore potential explanations for the changes in population size, such as influences of spruce budworm outbreaks, disease, and decreased structural diversity of forests owing to harvest practices. We also consider the challenges of interpreting changes in abundance of species with exceptionally variable populations, especially if population fluctuations or cycles may have long periodicities. Finally, we call for additional planned surveys to track the numbers of this enigmatic and charismatic species.

Past research has shown that plants possess the capacity to alter their instantaneous response of photosynthesis to temperature in response to a longer-term change in temperature (i.e. acclimate). This acclimation is typically the result of processes that influence net photosynthesis (Anet), including leaf biochemical processes such as the maximum rate of Rubisco carboxylation (Vcmax) and the maximum rate of photosynthetic electron transport (Jmax), stomatal conductance (gs) and dark respiration (Rd). However, these processes are rarely examined in the field or in concert with other environmental factors, such as precipitation amount. Here, we use a fully factorial warming (active heating up to +4 °C; mean = +3.1 °C) by precipitation (−50 % ambient to 150 % ambient) manipulation experiment in an old-field ecosystem in the north-eastern USA to examine the degree to which Ulmus americana saplings acclimate through biochemical and stomatal adjustments. We found that rates of Anet at ambient CO2 levels of 400 µmol mol−1 (A400) did not differ across climate treatments or with leaf temperatures from 20 to 30 °C. Canopy temperatures rarely reached above 30 °C in any treatment, suggesting that seasonal carbon assimilation was relatively homeostatic across all treatments. Assessments of the component processes of A400 revealed that decreases in gs with leaf temperature from 20 to 30 °C were balanced by increases in Vcmax, resulting in stable A400 rates despite concurrent increases in Rd. Photosynthesis was not affected by precipitation treatments, likely because the relatively dry year led to small treatment effects on soil moisture. As temperature acclimation is likely to come at a cost to the plant via resource reallocation, it may not benefit plants to acclimate to warming in cases where warming would not otherwise reduce assimilation. These results suggest that photosynthetic temperature acclimation to future warming will be context-specific and that it is important to consider assimilatory benefit when assessing acclimation responses.

The EFSA Panel on Plant Health (PLHP) performed a pest categorisation of Saperda tridentata (Coleoptera: Cerambycidae) for the EU. S. tridentata (elm borer) occurs in eastern North America. Ulmus americana and U. rubra are almost exclusively reported as hosts, apart from two 19th century records from the USA of larvae from Acer sp. and Populus sp. The Panel does not exclude the possibility of a post-entry shift in host range to European Ulmus or Acer and Populus. S. tridentata infests trees that are already weakened, and severe infestations can result in tree death. S. tridentata occurs across a range of climate types in North America that occur also in Europe. Between 2016 and 2019, S. tridentata larvae were intercepted with North American Ulmus logs imported into the EU. In the EU, American Ulmus species are mainly found in arboreta and as ornamental specimen trees. If only North American Ulmus are hosts, establishment is unlikely. However, if European Ulmus, Populus or Acer species become hosts, establishment is much more likely, with impact confined to already weakened trees. The information currently available on geographical distribution, biology, impact and potential entry pathways of S. tridentata has been evaluated against the criteria for it to qualify as potential Union quarantine pest or as Union regulated non-quarantine pest (RNQP). Since the pest is not reported in EU, it does not meet the criteria assessed by EFSA to qualify as potential Union RNQP. S. tridentata satisfies the criterion for quarantine pest regarding entry into the EU territory. Due to the scarcity of data, the Panel is unable to conclude if S. tridentata meets the post-entry criteria of establishment, spread and potential impact.

Ideally, variants of single-tree, group, and patch selection create new, spatially aggregated age classes and maintain a diversity of tree species and sizes in multiaged, mixed-species forests. We explored this notion in northern hardwood forests on the Menominee Nation, a forest ecosystem without the exploitive cutting history of most forests in the western Great Lakes region. Although the outcomes suggested a lack of relationship between gap characteristics and tree density, the expectations for tree regeneration were largely met: gap tree densities were >600 stems/ac and predominantly composed of sugar maple (Acer saccharum), American elm (Ulmus americana), and yellow birch (Betula alleghaniensis). Examination of stand diameter distributions indicate that gaps may not be necessary to establish regeneration on Menominee forests. To deepen the interpretation of our results, we include field and office discussions regarding the practicality of group openings when managing this forest.

A rapid and accurate method to detect the common strain of elm yellows (EY) phytoplasma in elm and insect samples was developed using a real-time polymerase chain reaction (PCR) procedure based on the TaqMan minor-groove-binder probe. Primers and probe were designed based on the EY phytoplasma-specific translocation protein secY gene DNA sequence. Success of the DNA extraction procedure was evaluated by amplifying the chloroplast trnL gene of Ulmus americana. The real-time PCR assay reacted positively with EY and EY phytoplasma strain ULW DNA, an isolate which occurs in Europe. It did not cross-react with Illinois EY or aster yellows phytoplasma DNA, both of which are known to occur in elm trees in the United States, nor did it amplify several other phytoplasmas belonging to the 16SrV and other phylogenetic groups. The real-time PCR protocol was used to identify 30 EY-positive elm trees on The Pennsylvania State University, University Park campus. Threshold cycle (CT) values obtained from the EY phytoplasma-infected elm trees ranged from 15 to 37. EY phytoplasma was detected in several leafhopper taxa. This real-time PCR method can be used for the diagnostic screening of elm trees and for the identification of possible insect vectors of EY phytoplasma.

A survey of urban trees affected by bacterial leaf scorch (BLS) caused by Xylella fastidiosa was conducted in the District of Columbia during 2011 and 2012. Over 20 species of urban trees were evaluated at 95 sites. Symptomatic and asymptomatic foliage from trees with BLS symptoms and foliage from neighboring asymptomatic trees were sampled. An X. fastidiosa-specific enzyme-linked immunosorbent assay (ELISA) and a polymerase chain reaction assay were used to detect and identify the strains from environmental samples. Symptomatic trees testing ELISA-positive for X. fastidiosa occurred most frequently with Quercus palustris, Q. rubra, Ulmus americana, and Platanus occidentalis. The bacterium was also less frequently identified on eight other symptomatic and five asymptomatic tree species. On infected trees, the bacterium was also detected on the asymptomatic portion of seven tree species. All strains were identified as the X. fastidiosa subsp. multiplex genotype ALSII except on Morus alba, where the genotype ALSI and the subsp. sandyi were detected. The occurrence of crown dieback was found significantly associated with X. fastidiosa-infection on Q. palustris, Q. rubra, U. americana, and P. occidentalis. Because this pathogen continues to perpetuate uncontrolled in urban environments, there is a pressing need to identify long-term management strategies that abate disease.

The Wabash and Erie Canal system was an important transportation network in the early 1800s prior to the dominance of trains and later automotive transportation. In this work, timbers from Culvert 151 were examined, after they were exhumed during construction of Hwy 641 on the south side of Terre Haute, Indiana. Cross-sections were taken from each of 22 beams and allowed to air dry to determine the stability of the timbers. We examined the wood to determine the genera or species of each sample that was used in this construction project and developed a floating chronology from our white oak group samples. The mix of species present included 11 beams of American beech (Fagus grandifolia), five white oak group (Quercus subgenus Lepidobalanus), and one each of American elm (Ulmus americana), winged elm (Ulmus alata), sugar maple (Acer saccharum), shagbark hickory (Carya ovata), white ash (Fraxinus americana), and black walnut (Juglans nigra). This suggests that the timbers were cut from the available...

The American elm (Ulmus americana) is a highly desirable deciduous shade tree with moderately dense foliage and a symmetrical broad or upright vase-shaped crown. This plant is susceptible to various diseases because of rapid terminal growth when new springwood vessels are fully functional. The American elm, along with many other shade tree species, can be affected by Xylella fastidiosa (Hearon et al. 1980), and X. fastidiosa has been previously confirmed on American elm in Ontario (Goodwin and Zhang 1997), Washington, D.C. (Harris and Balci 2015), Oklahoma (Olson et al. 2006), and Alabama (Parker et al. 2012). X. fastidiosa colonizes the xylem vessels of plant hosts and can cause bacterial leaf scorch disease (Pearson et al. 1998). On elm, X. fastidiosa causes leaf discoloration and browning, marginal scorching, and dieback. In the summer of 2019, chlorosis and marginal leaf scorch symptoms consistent with those of bacterial leaf scorch disease were observed on an American elm tree in a nursery in Pulaski County, Georgia. This elm tree was propagated from cuttings taken from a mature tree in Houston County, Georgia. Initial identification of the disease was performed by assessing characteristic symptoms of infection like leaf scorch, dieback signs, and so on, as described in Hernandez-Martinez et al. (2006). X. fastidiosa was verified via molecular and serological methods. Genomic DNA was extracted from the petioles and midribs of symptomatic leaves using the DNeasy Plant Kit (Qiagen, Valencia, CA), and real-time PCR was performed in a Cepheid smart cycler II (Sunnyvale, CA) using iQ SYBR Green Supermix (BioRad Laboratories, Hercules, CA). A 25-µl reaction was prepared according to the manufacturer’s protocol with primers XF-F/XF-R, which target the 16s rRNA processing protein (Harper et al. 2010). Real-time PCR results confirmed the presence of X. fastidiosa in all symptomatic leaves. The recombinase-polymerase-amplification technology-based AmplifyRP Acceler8 end-point detection assay (Agdia, Elkhart, IN) was carried out on symptomatic tissue using according to the manufacturer’s instructions, and this assay also confirmed the presence of X. fastidiosa in all symptomatic leaves (Waliullah et al. 2019). For further confirmation, the remaining petiole tissue was tested for X. fastidiosa using the DAS-ELISA Reagent Set for X. fastidiosa (Agdia) with minor modifications to the manufacturer’s protocol. In addition to tests of the symptomatic plant, testing of leaves from five additional young elm trees from the same nursery was also carried out according to the same procedures. These five visually healthy young elms tested negative for X. fastidiosa based upon all three testing methods. In total, three independent tests confirmed the presence of X. fastidiosa in symptomatic elm tissues, whereas asymptomatic elm trees from the same nursery tested negative. Attempts to isolate the bacteria from symptomatic leaf tissue on periwinkle wilt media (Davis et al. 1981) were not successful; however, the strong association of symptoms with the thrice-confirmed presence of X. fastidiosa in symptomatic tissue clearly indicates the role of X. fastidiosa in the observed symptoms. Although X. fastidiosa is most commonly transmitted by xylem-feeding insects, cuttings taken from infected hosts can produce infected plants; however, the mature tree used for propagation in this case could not be located for testing. To the best of our knowledge, this is the first report of X. fastidiosa associated with the American elm in Georgia. The presence of X. fastidiosa in American elm has the potential to impact homeowners, landscapers, and nursery producers within Georgia, and our findings suggest that Georgia tree nursery growers should monitor their nursery stock for bacterial leaf scorch disease.

Ulmus americana (American elm) was an important urban tree in North America prior to the introduction of the Dutch elm disease pathogen in 1930. Subsequently, urban and community forests were devastated by the loss of large canopies. Tree improvement programs produced disease tolerant American and Eurasian elm cultivars and introduced them into the nursery industry. However, consumer acceptance was slow. The National Elm Trial was established to evaluate commercially available taxa of elm across the United States. Established at 16 locations, these plantings monitored survival and growth, as well as disease and insect pressure for 7 to 10 years. ‘Morton’ elm had >90% survival, while 13 cultivars averaged 70% to 90%, and five cultivars ranged from 25% to 69% survival. Trunk diameter growth by location ranged from 0.5 cm/year (Colorado, U.S.) to more than 2.0 cm/year (Iowa, U.S.). By taxa, trunk diameter growth ranged from a low, by ‘JFS Bieberich’ elm (0.7 cm/year), to a high by ‘New Horizon’ elm (1.7 cm/year). Scale insects were minor issues at most trial locations, except Colorado, where scales contributed to the death of several cultivars. Performance ratings (scale 1 to 5) ranged from 2.7 for ‘JFS Bieberich’ elm to 4.5 for ‘New Horizon’ elm. Based on the ratings, the preferred cultivars of American elm were ‘New Harmony’ and ‘Princeton’, and the preferred cultivars of Asian elm were The Morton Arboretum introductions and ‘New Horizon’. These findings will help green-industry professionals determine what elm cultivars will perform the best in different regions.

Softwood cuttings of American elm varieties ‘Jefferson’, ‘New Harmony’, ‘Princeton’, ‘R18-2’, ‘Valley Forge’, and a tissue-cultured non-transformed control clone (BP-NT) were rooted using three different treatments to determine which method would be most suitable for small-scale propagation. The treatments included aeroponic chambers, an intermittent-mist bench in a greenhouse, and Grodan rootplugs soaked in a nutrient solution. The rootplug treatment had the highest percentage of rooted shoots (44%) followed by the intermittent-mist bench treatment (20%) and lastly by the aeroponics chambers (10%). The rooted cuttings from the rootplug treatment also looked substantially healthier and had more fresh growth four weeks after potting than the other two treatments. The Grodan rootplug treatment is recommended, but additional testing can be useful to improve the overall rooting percentage.

Five fungal species representing the three major spalting categories were inoculated onto wood of five different urban tree species with low to moderate economic value. Sugar maple (Acer saccharum) was also inoculated to serve as a control. Test samples were evaluated both internally and externally for spalting. The tested fungi had significant preferences for different wood species, and the preferences appeared to be related to sucrose availability. Specifically, zone line producing fungi preferred American elm (Ulmus americana), while Arthrographis cuboidea (pink stain) preferred tree-of-heaven (Ailanthus altissima). Wood species preference was also significant by decay class, with decay fungi preferring American elm, silver maple (Acer saccharinium), and horse chestnut (Aesculus hippocastanum). Staining fungi showed a preference for tree-of-heaven, while both decay classes readily colonized sugar maple and Norway maple (Acer platanoides).

The banded elm bark beetle, Scolytus schevyrewi Semenov (Coleoptera: Scolytidae), native to Asia, was detected in the United States in 2003, and as of 2011 it is known to occur in 28 states and four Canadian provinces. S. schevyrewi infests the same elm (Ulmus spp.) hosts as the long-established invasive, the European elm bark beetle, Scolytus multistriatus (Marsham). Information on the basic biology of S. schevyrewi in its native range is sparse; thus, we conducted laboratory studies and field studies in Colorado and Nevada. Comparisons of flight and behavioral responses were made with co-occurring S. multistriatus. When Siberian elm, Ulmus pumila L., cut logs (bolts) were allowed to be colonized by wild populations in the field, S. schevyrewi did not differ in emergence density from 10- versus 24-cm-diameter bolts. In the laboratory, S. schevyrewi readily colonized bolts of American elm, Ulmus americana L., but not Chinese elm, Ulmus parvifolia Jacq.; Siberian peashrub, Caragana arborescens Lam.; a cherry, Prunus fontanesiana (Spach) C. K. Schneid.; or Russian olive, Elaeagnus angustifolia L. In Colorado, S. schevyrewi often landed on elm bolts between 12:00 p.m. and 4 p.m.; and near large elm trees, they were captured more frequently on sticky traps at 1.8 and 3.7 m aboveground than higher along the main stem. In Colorado/Nevada, S. schevyrewi initiated flight in April/March and ceased in October/September, whereas S. multistriatus initiated flight in April/May and ceased in October/September. In funnel trap flight assays of semiochemicals in Colorado or Nevada, S. schevyrewi had moderate responses, 3–10-fold greater than unbaited control traps, to Multilure (a commercial lure for S. multistriatus), 2-methyl-3-buten-2-ol (MB) + multistriatin, and MB + a plant extract that is included in a commercial formulation of Multilure. In contrast, S. multistriatus had a 226–259-fold greater response to Multilure than to the control. Both Scolytus species showed electroantennographic (EAG) responses to MB, racemic multistriatin, and (+)- and (-)-α-inene, with the greatest sensitivity to multistriatin. S. schevyrewi was more responsive to (-)-α-pinene than was S. multistriatus.

During the investigation of the sudden and early onset of yellowing, followed by mortality of American elm (Ulmus americana L.) trees at the USDA Forest Service Northern Research Station in Delaware, Ohio, a phytoplasma of the clover proliferation group (16SrVI) was detected as the putative causal agent of the disease outbreak. Onset of symptoms was rapid and widespread, occurring in late July 2016 and affecting ∼60 trees across two elm research plantations. Symptoms included a general yellowing of individual tree canopies, epinasty of foliage throughout the canopy, phloem discoloration, and on a subset of trees, a strong odor of methyl salicylate (observed in phloem tissue extracted from the lower stem). Similar symptoms in elms have been attributed to the classic elm yellows ‘Candidatus Phytoplasma ulmi’ (16SrV-A) (Lee et al. 2004) and the Illinois elm yellows phytoplasma (16SrVI-C) (Jacobs et al. 2003). In July 2016, samples were collected from 12 symptomatic and 8 asymptomatic American elm trees. DNA from the leaf midrib and branch phloem was isolated and analyzed for phytoplasma via seminested polymerase chain reactions (PCR). PCRs were first primed by phytoplasma universal primer pair P5/P7 (Jomantiene et al. 1998), followed by P7 and the reverse complement of the universal phytoplasma primer R16R2 for amplification of the phytoplasma 16S-23 ribosomal (r) DNA (16S-23 rRNA gene) sequences as per Gundersen and Lee (1996). The predicted band size of the second PCR product is 487 base pair (bp). The product bands were isolated, purified, and sequenced using primer P7. Sequencing results of the PCR products indicated that nine of the symptomatic and one of the asymptomatic American elm trees tested were infected by a phytoplasma. A BLAST search of the DNA sequences indicated high similarities to members of the ‘Ca. P. trifolii’ group 16SrVI-A. The sequences of all 10 phytoplasma-infected trees were identical to each other. To further confirm that a strain of ‘Ca. P. trifolii’ was infecting the elms, a PCR product was cloned and sequenced. The 1,557 bp band was the product of primers P1a/P7, followed by PCR primers designed from the sequence of ‘Ca. P. trifolii’. This band was cloned into the pMiniT 2.0 vector. Plasmid sequencing used standard sequencing primers (SP6 and T7 promoters), the primers included with the vector, and finally, custom designed phytoplasma primers that eliminate other bacterial DNA from getting amplified. The entire plasmid clone was sequenced in both directions with four to six times of coverage per base. Determination of the phytoplasma classification group was based on the nucleotide sequence within the phytoplasma universal primers F2n/R2 PCR fragment within the 16Sr gene. Using iPhyClassifier, the online tool for phytoplasma classification and taxonomic assignment (https://plantpathology.ba.ars.usda.gov/cgi-bin/resource/iphyclassifier.cgi), the sequence similarity between the Delaware elm phytoplasma and ‘Ca. P. trifolii’ (GenBank accession no. AB279597.1) is 99.9% in the 16Sr region, which places the Delaware elm phytoplasma in the 16SrVI-A group. The sequence of the plasmid was deposited in GenBank under accession number MF385584. Elm decline and yellows diseases in North America have been associated with the Illinois elm yellows phytoplasma (16SrVI-C, GenBank accession no. AF268893.1) (Jacobs et al. 2003), ‘Ca. Phytoplasma ulmi’ (16SrV-A) (Lee et al. 2004), and phytoplasma in the aster yellows group (16SrI-C) (Lee et al. 1995).

Guidelines were developed by the New Brunswick Forest Gene Conservation Working Group for conserving genetic resources of four native tree species in New Brunswick. Gene conservation guidelines for three of these species aim to maintain sufficient gene pools of known or putatively resistant stock to retain or develop the potential for restoration. Natural populations of American beech (Fagus grandifolia) are known to have genotypes resistant to the beech scale at low frequencies. Gene conservation approaches include in situ and ex situ measures, including resistance breeding. White elm (Ulmus americana) demonstrates a degree of resistance to Dutch elm disease (DED), and will benefit from a mixture of in situ and ex situ conservation measures. Resistance to butternut canker has not yet been demonstrated in populations of butternut (Juglans cinerea), but ex situ conservation of putatively resistant genotypes will be of increasing importance as the frequency of butternut canker escalates. Bur oak (Quercus macrocarpa), threatened by small population size, habitat loss, and ongoing development, requires primarily in situ conservation and restoration efforts. Key words: American beech, bur oak, butternut, disease resistance, ex situ, gene conservation guidelines, genetic resources, in situ, restoration, white elm

Limited biological information about Phyllophaga ephilida, a major sweet potato pest in Louisiana, is available. In 2001 and 2002, a study was conducted in the laboratory to investigate the feeding preference of adult Phyllophaga ephilida (Say) (Coleoptera: Scarabaeidae) for the foliage of eight woody plant species: water oak (Quercus nigra L.), live oak (Quercus virginiana Mill.), red maple (Acer rubrum L.), slash pine (Pinus caribaea Morelet), pecan (Carya illinoensis (Wangenh) K. Koch), sweetgum (Liquidambar styraciflua L.), southern magnolia (Magnolia grandiflora L.), and American elm (Ulmus americana L.). Beetles were placed in an arena with the eight host plants and allowed to feed for 24 h (choice test). Leaf area consumed and change in leaf weight were recorded. In 2001 and 2002, host plant had a significant effect on both leaf area and weight consumed. In 2001, mean leaf area (mm2) consumed was pecan (504), followed by elm (314), water oak (237), maple (176), live oak (38.0), and sweetgu...

Rooted stem cuttings of 19 American elm (Ulmus americana L.) cultivars and selections, and rooted cuttings of two non-American elm selections, U. carpinifolia Gleditsch 51 and 970 (U. glabra Huds. x (U. wallichiana Planch. x U. carpinifolia)), along with a group of American elm seedlings, were planted in a randomized block design. When the trees were nine years old, they were inoculated with a mixed spore suspension of Ophiostoma ulmi (Buisman) C. Nannf. and Ophiostoma novo-ulmi Brasier, the causal fungi for Dutch elm disease (DED). Analyses of variance showed highly significant variation among clones in foliar symptoms 4 weeks after inoculation and in crown dieback one and two years after inoculation. After two years, 13 of the American clones showed significantly less dieback than the American elm seedlings, and 18 American clones showed significantly less injury than a randomly chosen, unselected American elm clone, 57845. The American clones with the most DED-tolerance were cultivars ‘Valley Forge,’ ‘Princeton,’ ‘Delaware,’ and ‘New Harmony,’ and selections N3487, R18-2, 290, 190, and GDH. The non-American selections 51 and 970 also exhibited high levels of disease tolerance. Most susceptible were American clones 57845, ‘Augustine,’ Crandall, W590, and the American elm seedlings. The most disease-tolerant American elm selections identified in this study are being evaluated further for possible naming and release to the nursery industry.

Parallel propagation tests of nine elm taxa - 6 species (Ulmus americana L., U. chenmoui Cheng, U. japonica (R) Sarg., U. laciniata (Tr) Mayr, U. laevis Pall. and U. parvifolia Jacq), 2 clones (U. 'Regal', U. 'Sapporo Autumn Gold') and 1 hybrid (U. pumila x japonica), by leaf bud cuttings and standard straignt softwood showed the results which point to the possibility of wider application of leaf bud cuttings. In some elm taxa, leaf bud cuttings can be the main method of propagation, and it can be used as an additional method in other taxa, because the seasonal timing is extended compared to standard cuttings.

Trunk injection of azadirachtin into elm trees (Ulmus americana) using the Ecoject™ Microinjection System to reduce emergence numbers of red elm bark weevil (Magdalis armicollis) was evaluated. Twelve mature trees were each injected with TreeAzin™ in early August 2010 at a rate of 16 ml per 15.2 cm trunk circumference at breast height. The following year, weevil activity was monitored at weekly intervals for four weeks using sticky traps placed in the canopies. There was a significant reduction of 55%–60% in weevil activity in early summer in the treated tree canopies as compared to the control, suggesting that this method may be an effective management tool for this pest.

American Elms were devastated by an outbreak of Dutch Elm Disease is caused by the fungus Ophiostoma novo-ulmi Brasier that originated in Asia and arrived in the early 1900s. In spite of decades of study, the specific mechanisms and disease resistance in some trees is not well understood. the fungus is spread by several species of bark beetles in the genus Scolytus, during their dispersal and feeding. Our objective was to understand elm responses to beetle feeding in the absence of the fungus to identify potential resistance mechanisms. A colony of Scolytus multistriatus was established from wild-caught beetles and beetles were co-incubated with susceptible or resistant American elm varieties in a controlled environment chamber. Beetles burrowed into the auxillary meristems of the young elm shoots. The trees responded to the beetle damage by a series of spikes in the concentration of plant growth regulating compounds, melatonin, serotonin, and jasmonic acid. Spikes in melatonin and serotonin represented a 7,000-fold increase over resting levels. Spikes in jasmonic acid were about 10-fold higher than resting levels with one very large spike observed. Differences were noted between susceptible and resistant elms that provide new understanding of plant defenses.

Rooted stem cuttings of eight American elm (Ulmus americana L.) cultivars or selections, in addition to rooted stem cuttings of two non-American elm cultivars, ‘Prospector’ (U. wilsoniana Schneid.) and ‘Frontier’ (U. carpinifolia Gleditsch x U. parvifolia Jacq.), all planted in a randomized block, split-plot design, were inoculated on either one of two dates in May 1992 with a mixed spore suspension of Ophiostoma ulmi (Buisman) C. Nannf. and Ophiostoma novo-ulmi Brasier, the causal fungi for Dutch elm disease (DED). Crown dieback and survival were recorded once yearly for 7 years following inoculations, and height growth was measured after the sixth growing season. Analyses of variance and regression showed significant differences in disease severity among all clones tested. Among the American elms, crown dieback and mortality over time were least for ‘Valley Forge,’ ‘Princeton,’ and ‘New Harmony; ’ intermediate for ‘Delaware’ and selection R18-2; and greatest for selections 57845 and 11 and the cultivar American Liberty. Dieback and survival of ‘Prospector’ and ‘Frontier,’ the non-American elms, were comparable to that of the more disease-tolerant American elm clones. Height growth on surviving American elms for six years after inoculation was greatest for ‘Valley Forge’ and ‘Princeton’ and least for 57845, 11, and ‘American Liberty.’ Results demonstrate the ability of certain American elm cultivars and selections to respond and then recover from heavy doses of the two fungi which cause DED.

During 1993 and 1994, we radiotracked 11 adult female and juvenile northern bats ( Myotis septentrionalis ) to 32 roost trees: 18 silver maples ( Acer saccharinum ), 1 red maple (A. rubrum ), and 13 green ashes ( Fraxinus pennsylvanica ). Fifty-three percent of the trees were living; 52% of the roosts were in crevices or hollows, and the rest were under exfoliating bark. Northern bats did not use American elms ( Ulmus americana ) in proportion to their abundance, but in general, characteristics of roost trees were similar to a random sample of apparently suitable trees. Northern bats changed roosts every 2 days, and distance between roosts varied from 6 to 2,000 m. As many as 60 adults were found in a single tree, making this the largest summer aggregation ever reported for the species. Compared with Indiana bats ( M. sodalis ) separately studied at the same site, northern bats moved greater distances between roosts and roosted more often in maples, cavities, living trees, and areas with high canopy cover.

Jacobi, W. R., Koski, R. D., Harrington, T. C., and Witcosky, J. J. 2007. Association of Ophiostoma novo-ulmi with Scolytus schevyrewi (Scolytidae) in Colorado. Plant Dis. 91:245-247. The smaller European elm bark beetle, Scolytus multistriatus, has been the primary vector of the Dutch elm disease fungus, Ophiostoma novo-ulmi, in elm trees in Colorado since 1948. An exotic from Asia, the banded elm bark beetle, Scolytus schevyrewi, was found in Siberian elm, Ulmus pumila, in Colorado in April of 2003; this was the first report of S. schevyrewi in North America. S. schevyrewi is now found throughout much of Colorado and in at least 21 other states. The similarities in breeding and feeding habits between S. schevyrewi and S. multistriatus have raised concerns about the ability of S. schevyrewi to serve as a vector for O. novo-ulmi. The objective of this preliminary study was to determine if O. novo-ulmi could be isolated from adult S. schevyrewi emerging from diseased elm trees. S. schevyrewi and S. multistriatus were allowed to infest diseased stem segments of American elm, Ulmus americana. The infested stem segments were caged and isolations were made from the adult brood that emerged. O. novo-ulmi was isolated from most of the adults of both beetle species, showing that S. schevyrewi could acquire the pathogen as effectively as S. multistriatus. Future studies are needed to determine if S. schevyrewi can effectively transmit the pathogen to healthy trees.

Six-week-old half-sib seedlings of Ulmus americana L. were subjected to different amounts of flexure daily for 3 weeks under controlled greenhouse conditions. The daily flexure treatments were: no flexing in a staked stem, minimal flexing in a non-staked stem, and five, 10, 20, 40, and 80 flexures. Seedling height and diameter growth and average leaf area were determined before and after the treatments. The ratio of the change in height growth (DeltaH) to the change in diameter growth (DeltaD; (DeltaH:DeltaD)) before and after the 3-week treatments were calculated. At the end of the 3-week experiment, staked seedlings were significantly taller and had smaller stem diameters than all of the flexed seedlings. Height growth tended to decrease exponentially with increased flexure, with significant differences between the extremes of treatment. All of the flexure treatments significantly increased stem diameter compared to staked seedlings. The DeltaH:DeltaD ratio exhibited an exponential function in response to increased flexure. Average leaf area decreased with increased flexure, and seedlings in the 40x and 80x flexure treatments had significantly less leaf area than seedlings in all of the other treatments. These data are similar to the dose responses previously observed in herbaceous species. The finding that trees exhibit greater sensitivity to low doses of flexure than to high doses of flexure indicates that slight exposure to wind may result in a large initial alteration in stem morphology, producing a thigmomorphogenetic effect. Trees will continue to respond to increasing amounts of mechanical stress, but at an exponentially declining rate. Declining leaf areas in response to increasing amounts of mechanical stress may result in a decrease in available photosynthate, resulting in a tree of smaller stature compared to trees exposed to lower amounts of mechanical loading.

This summary is a project of the Institute for Community Engaged Scholarship (ICES) at the University of Guelph, with project partners: the Catalyst Centre, SPARK Program at the University of Guelph, and Knowledge Mobilization Unit at York University. This project is part of the Pan-Canadian Research Impact Network. http://csahs.uoguelph.ca/pps/Clear_Research Researchers developed a technique for growing clones of mature American elm trees, which may improve conservation of this and other endangered tree species. This method involved optimizing the levels of plant hormones in the growing substrate while blocking the action of naturally occurring growth-regulating hormones called auxins. Project support by Agri-Food and Rural Link, Mobilizing Agri-food and Rural Research Knowledge. A program of the OMAFRA-U of G Partnership. http://www.uoguelph.ca/research/omafra/partnership/KTT_and_IP.shtml

We used randomly amplified polymorphic DNA (RAPD) markers from DNA polymerase chain reactions to differentiate selected American elms. DNA profiles made from leaf DNAs of parental trees were identical to profiles produced by DNA from leaves, roots, vascular tissues, callus or suspension-cultured cells from the same trees or their ramets. In addition, several variations in the technique did not appear to alter the genotype-specific DNA profiles from a given elm selection. RAPD polymorphisms were inherited as dominant Mendelian factors in the progeny of a cross between two American elm selections. We conclude that the construction of RAPD DNA profiles is a reliable and easy method for selection identification, genetic analysis, and the assembly of linkage maps in American elms.

Selected elms Ulmus spp. and their hybrids growing at the Morton Arboretum, Lisle, IL were evaluated in the laboratory for feeding preference by the elm leaf beetle, Pyrrhalta luteola (Muller). Results from the single-choice and multiple-choice feeding studies showed that U. szechuanica was the least suitable for feeding and reproduction by the adult elm leaf beetle. The hybrids U. pumila x U. parvifolia and U. pumila x U. americana, and U. pumila (control) appeared to be highly suitable for feeding and reproduction by the adult elm leaf beetle. Adult longevity and the pre-ovipositional period appeared to be a function of suitability as adults feeding on U. szechuanica had the shortest longevity and the longest pre-ovipositional period. The converse was also true. Results from multiple-choice studies were consistent with the single-choice studies. The intermediately suitable species/hybrids of U. japonicawilsoniana x U. pumila, U. Japonica, U. macrocarpa, and U. wilsoniana show promise for further elm breeding programs. Further studies are needed to evaluate hybrid crosses of the intermediately and least preferred elms as potential sources of shade trees resistant to Dutch elm disease and not preferred by the elm leaf beetle.

The hydraulic resistance of pit membranes was measured directly in earlywood vessels of Fraxinus americana and Ulmus americana. The area-specific resistance of pit membranes (r(mem)) was higher than modeled or measured values obtained previously for hardwood species, with r(mem) of 5.24 × 10(3) MPa·s·m(-1) for Fraxinus and 2.56 × 10(3) MPa·s·m(-1) for Ulmus. The calculated resistance of pit canals was three orders of magnitude below total pit resistance indicating that pit membranes contributed the majority of resistance. Scanning electron microscopy indicated that pit membranes of Ulmus were thinner and more porous than those of Fraxinus, consistent with the difference in r(mem) between the species. Measurements of average vessel diameter and length and area of wall overlap with neighboring vessels were used to partition the vascular resistance between vessel lumen and pit membrane components. Pit membrane resistance accounted for 80% of the total resistance in Fraxinus and 87% in Ulmus in 2-yr-old branch sections. However, measurements of vessel dimensions in the trunk suggest that the division of resistance between pit membrane and lumen components would be closer to co-limiting in older regions of the tree. Thus, pit membrane resistance may be of greater relative importance in small branches than in older regions of mature trees.

PREMISE OF THE STUDY Exotic diseases are threatening many North American tree species, and management of diseases requires understanding the biology of the host as well as the pathogen. Ulmus americana is a widespread dominant tree of eastern North America that has been widely planted as an ornamental and shade tree. Populations of the species have suffered heavy mortality from Dutch elm disease, caused by an introduced fungus. Ulmus americana is generally reported to be tetraploid, but the discovery of triploid trees in cultivation suggested that lower ploidy levels may exist in the wild, so the species was surveyed for nuclear DNA content. METHODS Ploidy level was estimated by flow cytometry for 81 individuals from wild populations of U. americana from throughout the range of the species and for four cultivated trees of interest. KEY RESULTS Most specimens were tetraploid, as previously reported for the species, but 21% of the wild trees sampled were diploid, a ploidy level not previously confirmed for the species. Tetraploids are found throughout the range of the species. Diploids are most common on the Atlantic coastal plain, Cumberland Plateau, and in southern Ohio, but isolated diploids were also found in central Texas, Oklahoma, and eastern Missouri. Diploids and tetraploids grew in proximity in several areas, but no wild triploids were found in the course of this survey. CONCLUSIONS The species is genetically heterogeneous, but further research is needed to understand the origin and relations of the different ploidy levels. Understanding the ploidy situation in U. americana will be important in the search for further genotypes that are resistant to Dutch elm disease.

Leaf breakdown rates of two species of elm (Ulmus) and two of maple (Acer) were investigated in two low order streams located in Western Maryland, U.S.A., and in Northern Appenins, Italy. Within each genus of leaf, one species was Italian and one was American. The role of maeroinverteb rate shredders in leaf processing was also investigated. In both streams within the same genus of leaf the Italian leaves disappeared faster than the American leaves. Within the same species, the leaves were decomposed more rapidly in the Italian stream. Shredder biomass was always signifi­ cantly higher on the leaves retrieved from the Italian stream suggesting that shredders had an important role in detritus processing. On the contrary, the comparison between leaf species showed a poor correlation between shredder biomass and leaf breakdown rate. Three hypotheses are proposed. The fact that native leaves were not processed at a faster rate, compared to the exotic leaves, support the notion that shredders do not specialize on litter of a given leaf species, but rather on appropriately conditioned leaf Utter regardless of the species. Breakdown rates followed the same rank orde­ ring in each stream : Acerpseudoplatanus > Ulmus minor > Ulmus americana > Acer rubrum indicating the existence of the same hierarchy in the availability of food to macroinverteb rates throughout the year.