Kalmia Latifolia Research Articles

A common ericoid shrub modulates the diversity and structure of fungal communities across an arbuscular to ectomycorrhizal tree dominance gradient.

Differences between arbuscular (AM) and ectomycorrhizal (EcM) trees strongly influence forest ecosystem processes, in part through their impact on saprotrophic fungal communities. Ericoid mycorrhizal (ErM) shrubs likely also impact saprotrophic communities given that they can shape nutrient cycling by slowing decomposition rates and intensifying nitrogen limitation. We investigated the depth distributions of saprotrophic and EcM fungal communities in paired subplots with and without a common understory ErM shrub, mountain laurel (Kalmia latifolia L.), across an AM to EcM tree dominance gradient in a temperate forest by analyzing soils from the organic, upper mineral (0-10cm), and lower mineral (cumulative depth of 30cm) horizons. The presence of K. latifolia was strongly associated with the taxonomic and functional composition of saprotrophic and EcM communities. Saprotrophic richness was consistently lower in the Oa horizon when this ErM shrub species was present. However, in AM tree-dominated plots, the presence of the ErM shrub was associated with a higher relative abundance of saprotrophs. Given that EcM trees suppress both the diversity and relative abundance of saprotrophic communities, our results suggest that separate consideration of ErM shrubs and EcM trees may be necessary when assessing the impacts of plant mycorrhizal associations on belowground communities.

Over the river and through the woods: Multi-scale habitat associations of two at-risk bird species in riparian forests of the Central Appalachians

Several species-specific habitat management guidelines have been created over the past decade to help recover declining populations of forest birds in eastern North America. Conserving eastern forest birds through forest management requires understanding the factors driving species occurrence patterns and how the needs of various species complement or contrast with each other. Our study assessed and compared occupancy patterns of two at-risk species associated with riparian forests: the Wood Thrush (Hylocichla mustelina) and the Canada Warbler (Cardellina canadensis). We conducted point-count surveys and vegetation sampling at 304 unique locations along 33 stream sections in central and southwestern Pennsylvania from May – June 2018 and 2019. We used single-season occupancy models to examine the influence of vegetation composition (i.e., microhabitat conditions), forest structure (i.e., from Light Detection and Ranging data, “LiDAR”), and other factors (i.e., stream order and elevation) on focal species occurrence patterns. Wood Thrush occupancy (mean ᴪˆ: 0.57) was best explained by the presence of mountain laurel (Kalmia latifolia; negative effect), elevation (negative effect), canopy height (positive effect), and canopy structural heterogeneity (positive effect). Canada Warbler occupancy (mean ᴪˆ: 0.55) was best explained by the presence of mountain laurel (positive effect), stream order (positive effect), elevation (positive effect), density of understory vegetation (positive effect), and canopy structural heterogeneity (negative effect). While both bird species occurred relatively frequently in riparian forests, our results indicate that habitat factors at multiple spatial scales play a role in regulating their occurrence patterns. Moreover, the two species exhibited contrasting habitat associations. Specifically, Canada Warblers preferred sites supporting dense mountain laurel, typically at elevations >600 m, and with a largely intact canopy. These patterns were reversed for Wood Thrushes. These contrasting associations will limit opportunities to manage riparian forests in a manner that conveys co-benefits for our two focal species. As a general rule, forest managers in our study region can target habitat management for Canada Warblers in riparian areas above 600 m and in areas below 600 m for Wood Thrushes. Given our focal species’ use of other (non-riparian) forest types as breeding habitat and broad geographic distributions, it is important to recognize that our findings may not apply outside of riparian forests or beyond the Central Appalachian Mountains.

Changes in Mortality, Heart Rate, and Gene Response in Daphnia magna Exposed to Concentrated and Homeopathic Kalmia latifolia Distillates

Changes in Mortality, Heart Rate, and Gene Response in Daphnia magna Exposed to Concentrated and Homeopathic Kalmia latifolia Distillates

Soil Respiration and Related Abiotic and Remotely Sensed Variables in Different Overstories and Understories in a High-Elevation Southern Appalachian Forest

Accurately predicting soil respiration (Rs) has received considerable attention recently due to its importance as a significant carbon flux back to the atmosphere. Even small changes in Rs can have a significant impact on the net ecosystem productivity of forests. Variations in Rs have been related to both spatial and temporal variation due to changes in both abiotic and biotic factors. This study focused on soil temperature and moisture and changes in the species composition of the overstory and understory and how these variables impact Rs. Sample plots consisted of four vegetation types: eastern hemlock (Tsuga canadensis L. Carriere)-dominated overstory, mountain laurel (Kalmia latifolia L.)-dominated understory, hardwood-dominated overstory, and cinnamon fern (Osmundastrum cinnamomeum (L.) C. Presl)-dominated understory, with four replications of each. Remotely sensed data collected for each plot, light detection and ranging, and hyperspectral data, were compiled from the National Ecological Observatory Network (NEON) to determine if they could improve predictions of Rs. Soil temperature and soil moisture explained 82% of the variation in Rs. There were no statistically significant differences between the average annual Rs rates among the vegetation types. However, when looking at monthly Rs, cinnamon fern plots had statistically higher rates in the summer when it was abundant and hemlock had significantly higher rates in the dormant months. At the same soil temperature, the vegetation types’ Rs rates were not statistically different. However, the cinnamon fern plots showed the most sensitivity to soil moisture changes and were the wettest sites. Normalized Difference Lignin Index (NDLI) was the only vegetation index (VI) to vary between the vegetation types. It also correlated with Rs for the months of August and September. Photochemical reflectance index (PRI), normalized difference vegetation index (NDVI), and normalized difference nitrogen index (NDNI) also correlated with September’s Rs. In the future, further research into the accuracy and the spatial scale of VIs could provide us with more information on the capability of VIs to estimate Rs at these fine scales. The differences we found in monthly Rs rates among the vegetation types might have been driven by varying litter quality and quantity, litter decomposition rates, and root respiration rates. Future efforts to understand carbon dynamics on a broader scale should consider the temporal and finer-scale differences we observed.

Characteristics of Dry-Mesic Old-Growth Oak Forests in the Eastern United States

Dry-mesic old-growth oak forests are widely distributed remnants across the eastern U.S. and are expected to increase in number and extent as second-growth forests mature. In this study, we synthesize published and unpublished information to better define the species, structure and extent of these forests. Mean site tree density for trees ≥10 cm dbh ranged from 341–620 trees ha−1. In the eastern part of the region, most stand basal areas were >23 m2 ha−1, compared to ≤23 m2 ha−1 in the westernmost stands. Overall, woody species diversity was relatively low compared to old-growth oak forests on moister sites, with tree species per forest ranging from 5–18. The most common species among the stands were white oak (Quercus alba), northern red oak (Quercus rubra), and black oak (Quercus velutina). Shrub and vine species per forest ranged from 1–10, with common species or genera including Virginia creeper (Parthenocissus quinquefolia), poison ivy (Toxicodendron radicans), Vaccinium spp., and grapevines (Vitis spp.). Within the southern Appalachian Mountains, rosebay rhododendron (Rhododendron maximum) and mountain laurel (Kalmia latifolia L.) were common. Herbaceous species per stand ranged from 4–51, with the highest richness occurring in a southern Appalachian oak-hickory forest. The maximum within-stand age of the large trees ranged from 170 to over 365 years. The mean density of standing dead trees ≥10 cm dbh ranged from 31–78 ha−1 and the volume of coarse woody debris ≥10 cm in diameter averaged 52 m3 ha−1. We more fully describe the characteristics of these forests and fill gaps in the collective knowledge of this increasingly important forest type. However, over the past 20 years, there has been scant research on these forests, and older research studies have used a variety of research plots and methods. A uniform approach to surveying these sites is needed to gain a better understanding of these forests before we are faced with caring for an increase in old-growth forest areas.

Fuel and vegetation changes in southwestern, unburned portions of Great Smoky Mountains National Park, USA, 2003–2019

Overstory basal area, ericaceous shrub cover (Kalmia latifolia L. and Rhododendron maximum L.), and fuels (i.e., woody fuel loads and depths and O Horizon thickness) were assessed within Great Smoky Mountains National Park, USA, in 2003 − 2004. Due to recent wildfire activity within the southern Appalachian Mountain region (including Great Smoky Mountains National Park), the potential spread and expansion of ericaceous shrubs, and the impacts of the hemlock woolly adelgid (Adelges tsugae Annand) on eastern hemlock (Tsuga canadensis (L.) Carrière), these same ecosystem components were again assessed in 2019. Elevation and moisture regime (xeric, intermediate, and mesic) were included in this assessment as potential influential factors. An evaluation of repeated measurements from 40 plots suggested that O Horizon thickness did not change significantly over the 16-year period, but increased as elevation increased, and moisture regime (xeric O Horizon thickness > mesic O Horizon thickness) was a significant, related factor. The sum of 1-, 10-, and 100-h fuel loads (fuels less < 7.6 cm diameter) increased, whereas woody fuel depth decreased over the 16-year period. No significant changes in 1000-h fuel loads (> 7.6 cm diameter), total woody fuel loads, ericaceous shrub cover, total basal area, or live T. canadensis basal area were observed. Live T. canadensis basal area decreased with increasing elevation. Dead, standing T. canadensis basal area increased from 2003–2019, and that increase was most pronounced as elevation increased on xeric and intermediate sites. Overall, we found that: 1. hypothesized increases in total woody fuel loads and ericaceous shrub cover were not present; and 2. elevation and moisture regime were most related to observed changes in vegetation and fuel condition.

Logging legacies in a plant biodiversity hotspot: Altered distribution and abundance patterns of the shrub layer in the southern Appalachians

Altered disturbance regimes in forest ecosystems can lead to the formation of dense, persistent understory vegetation composed of a small number of dominant species. This understory layer often limits tree seedling recruitment, decreases biodiversity, and can alter forest ecosystem structure and functioning. In the southern Appalachians – one of the most biodiverse regions in North America – pervasive logging in the 19th and early 20th centuries may have contributed to the formation of a dense understory shrub layer that suppresses plant diversity and tree recruitment, but the evidence for this idea has been mixed. To help clarify this issue, we tested whether (a) the two dominant understory shrub taxa (Kalmia latifolia and evergreen Rhododendron species) were more common or more abundant in areas with a history of intense logging than in areas undisturbed by logging, and (b) the relationships between the understory shrub layer and environmental gradients that drive regional biodiversity and plant distributions in the Southern Appalachians (e.g., climate, soils) differ in logged versus undisturbed areas. We used publicly available, extensive, and spatially explicit data on vegetation, climate, topography, soils, solar radiation, and logging history in Great Smoky Mountains National Park to build beta and binomial regression models of shrub frequency and cover as a function of logging history and environmental variables. Contrary to our expectation and speculations in the literature, we found that the dominant shrub taxa were more common (frequent) in areas with no logging history. However, we also found that logging history effects on shrub abundance (cover) varied along environmental gradients. For example, in topographically shaded landscape positions evergreen Rhododendron thickets exhibited greater cover in logged areas than in areas with no logging history. On the other hand, Rhododendron thickets exhibited lower cover in logged areas than in areas with no logging history at low elevations. Thus, conservation planning and forest management in topographically complex regions need to consider both landscape context (e.g., elevation, landscape position) and past logging as important interacting drivers that either facilitate or suppress local formation of dense shrub understories that can ultimately impact tree regeneration patterns, biodiversity, and ecosystem functioning.

Effects of burn season on fire-excluded plant communities in the southern Appalachian Mountains, USA

Following decades of fire exclusion, managers are increasingly implementing prescribed fire in southern Appalachian forests. To date, the use of prescribed fire in the region has often been focused on reducing hazardous fuel loads and has typically occurred in the dormant season. Understanding the effects of burning in different periods of plant growth may reveal how burn season influences patterns of vegetative succession. In this study, we compared the effects of prescribed burn treatments conducted in the dormant season (January-early April) vs. the early growing season (mid-late April) on changes in plant abundance by understory, midstory, and overstory forest strata. Plant groups were distinguished by growth habit, stem origin, functional characteristics, and species of management interest (red maple (Acer rubrum L.) and mountain laurel (Kalmia latifolia L.)). Burn season had minimal effect on understory cover, density, richness, or diversity. In the midstory, early growing season burns were more effective in reducing shrub density than dormant season burns (−1,585 ± 188 ha−1 vs. −813 ± 240 ha−1, respectively), with greater differences among smaller stems. Early growing season burns also reduced midstory red maple density to a greater degree than dormant season burns (−356 ± 57 ha−1 vs. −219 ± 69 ha−1), a response that was not observed among other mesophytic hardwood species. Burning slightly reduced canopy cover, but neither canopy cover nor overstory density response varied by burn season. Our results demonstrate that managers may find increased opportunities to promote forest restoration objectives in the southern Appalachians by extending the use of prescribed fire into the early growing season.

Predicted Spatial Distribution of the Eastern Spotted Skunk (Spilogale putorius) in Virginia Using Detection and Non-Detection Records

The geographic distribution of a species is a fundamental component in understanding its ecology and is necessary for forming effective conservation plans. For rare and elusive species of conservation concern, accurate maps of predicted occurrence are particularly problematic and often highly subjective. Spilogale putorius (Eastern Spotted Skunk) populations have experienced large declines since the 1940s. Their elusive behavior and perceived rarity result in low detection probability when using conventional methods for sampling small mammals. Low detection probability often causes uncertainty as to where Eastern Spotted Skunks could be a management concern. We modeled the distribution of predicted occurrence of Eastern Spotted Skunks using verifiable occurrence and non-detection records obtained throughout Virginia from 2010 to 2020. Occurrence data consisted of trapping records reported to the Virginia Department of Wildlife Resources, incidental photo-verified reports of sightings and road-killed animals, and remote-camera detections. Non-detections were presumed at baited remote-camera locations following intense survey efforts. We fit predicted occurrence models using generalized linear modeling in an information-theoretic framework using the package ‘stats’ in Program R. Our results incidated a greater probability of presence from the Blue Ridge westward, increasing with slope steepness along northeastern- to southeastern-facing slopes and decreasing with slope steepness along southeastern- to southwestern-facing slopes. Emergent rock outcrops prominent along northeastern slopes offer ample protective rocky cover, whereas mixed Quercus spp. (oak), Kalmia latifolia (Mountain Laurel), and Rhododendron maximum (Rosebay Rhododendron) forest communities along southern-facing slopes provide suitable areas of cover, both of which are critical for spotted skunk survival and reproductive success. Our analysis provides insight into the relationships between landscape features and Eastern Spotted Skunk distributions across Virginia. Understanding these relationships is critical for the effective management and conservation of this vulnerable species.

Den-Site Selection by Eastern Spotted Skunks in the Central Appalachian Mountains of West Virginia

We assessed den-site selection of Spilogale putorius (Eastern Spotted Skunk) in the Appalachian Mountains of West Virginia by radio-tracking 8 individuals to 83 dens from January 2018 to October 2019. We measured local habitat characteristics at den sites and nearby, presumed unused paired sites and compared the habitat predictors via binary logistic regression. Results from the averaged model indicated greater understory cover from stems of Kalmia latifolia (Mountain Laurel) and Vaccinium spp. (Blueberry) and Gaylussacia spp. (Huckleberry), as well as medium to large rocks, and coarse woody debris increased the odds of a den site being used. Medium to large rocks were the most influential predictor of a den site. Our results suggest Eastern Spotted Skunks in this region would likely benefit from management practices that increase density of understory cover and coarse woody debris and preserve rocky outcroppings.

English

As general awareness for using herbal drugs in today&rsquo;s health practice is increasing, the world is endorsing extraordinary increase in the consumption of herbal products. This increase in the demand has led to consumers&rsquo; dissatisfaction due to substandard products, making the herbal market risky. There is need to set standard that will help to evaluate herbal drugs to ensure formulation of high quality products. The present investigation is conducted to evaluate the physiochemical measures of accessible mother tinctures from Aconitum napellus, Kalmia latifolia, Crataegus monogyna, Atropa belladonna and Digitalis purpurea. Mother tinctures were collected from five manufacturers in Pakistan and evaluated for physiochemical parameters, % alcohol contents, weight in dry/ml, % non-volatile matter and pH.&nbsp; World synchronization, following WHO specific guidelines for herbal products standardization is needed. Also, regulation should be endorsed to control herbal market adoption of WHO guideline. Key words: Herbal drugs, standardization, quality control, Aconitum napellus, Kalmia latifolia, Crataegus monogyna, Atropa Belladonna, Digitalis purpurea.

Pygmaeomycetaceae, a new root-associated family in Mucoromycotina from the pygmy pine plains

ABSTRACT A new genus, Pygmaeomyces, and two new species are described based on phylogenetic analyses and phenotypic and ecological characters. The species delimitation was based on concordance of gene genealogies. The Pygmaeomyces cultures were isolated from the roots of mountain laurel (Kalmia latifolia) and pitch pine (Pinus rigida) from the acidic and oligotrophic New Jersey pygmy pine plains; however, they likely have a broader distribution because their internal transcribed spacer (ITS) sequences have high similarity to a number of environmental sequences from multiple independent studies. Based on the phylogeny and phenotypic characters, a new family, Pygmaeomycetaceae, is proposed to accommodate this new lineage in Mucoromycotina. Pygmaeomycetaceae corresponds to Clade GS23, which was identified based on a sequence-only soil fungal survey and was believed to be a distinct new class. Compared with the culture-based methods, we observed that sequence-only analyses tend to overestimate the taxonomic level. Results from this work will facilitate ecological and evolutionary studies on root-associated fungi.

Assessing Genetic Diversity and Population Structure of Kalmia latifolia L. in the Eastern United States: An Essential Step towards Breeding for Adaptability to Southeastern Environmental Conditions

Kalmia latifolia L. (mountain laurel), an attractive flowering shrub, is considered to be a high-value ornamental plant for the eastern United States. Limited information on the genetic diversity and structure of K. latifolia is available, which obstructs efficient germplasm utilization and breeding for adaptability to southeastern environmental conditions. In this study, the genetic diversity of 48 wild K. latifolia plants sampled from eight populations in the eastern U.S. was assessed using eight inter simple sequence repeat (ISSR) markers. A total of 116 bands were amplified, 90.52% of which (105) were polymorphic. A high level of genetic diversity at the species level was determined by Nei’s gene diversity (0.3089) and Shannon’s information index (0.4654), indicating that K. latifolia was able to adapt to environmental changes and thus was able to distribute over a wide latitudinal range. In terms of the distribution of genetic diversity, Nei’s genetic differentiation and analysis of molecular variance (AMOVA) showed 38.09% and 29.54% of diversity existed among populations, respectively, elucidating a low-to-moderate level of among-population genetic differentiation. Although a relatively large proportion of diversity was attributed to within-population variation, low diversity within populations (mean genetic diversity within populations (HS) = 0.19) was observed. Both STRUCTURE and unweighted pair group method with arithmetic mean (UPGMA) dendrograms exhibited the clustering of populations that inhabit the same geographic region, and four clusters correlated with four geographic regions, which might be attributed to insect pollination, small population size, and environmental conditions in different habitats. These results function as an essential step towards better conserving and utilizing wild K. latifolia resources, and hence promoting its genetic improvement and breeding for adaptability to southeastern environmental conditions.

Implementation of Soil Moisture Sensor Based Automated Irrigation in Woody Ornamental Production1

Abstract A soil moisture sensor-based automated irrigation system was trialed in a commercial ornamental nursery over the 2014-2015 growing seasons. In both years, use of the sensor-based system resulted in an approximate 50% reduction in irrigation application (volume) when compared to grower-managed irrigation. No differences in growth and equivalent or slightly reduced crop losses were noted when comparing the sensor-based irrigation system to grower-managed irrigation in production of Pieris japonica, Hydrangea quercifolia, and Kalmia latifolia. In 2014, Rhododendron catawbiense had equivalent canopy size and reduced mortality when comparing sensor-based irrigation to grower-managed irrigation. However, in 2015 irrigation control with the sensor-based system resulted in significant (&amp;gt;50%) Rhododendron losses. High mortality was thought to have resulted from use of averaged (across crop species) soil moisture readings to establish irrigation set points. Canopy structure of Rhododendron obstructed water capture to a greater degree than the other three species due to canopy architecture. This effect, combined with precision irrigation applications, resulted in persistent drought conditions within the Rhododendron block. Soil moisture sensor-based automated irrigation can be an effective means of automating irrigation. Support from crop consultants is highly desirable to minimize disruption and maximize adoption during implementation. Index words: Pieris Japonica D. Don ex G. Don ‘Prelude', Hydrangea quercifolia W. Bartram ‘Jet Stream', Rhododendron catawbiense Michx. ‘Roseum Elegans', Kalmia latifolia L. ‘Sarah', irrigation groupings, automation, canopy structure, irrigation capture, technology transfer, outreach, education, precision irrigation Species used in this study: Japanese andromeda ‘Prelude' (Pieris Japonica D. Don ex G. Don); Oakleaf hydrangea ‘Jet Stream' (Hydrangea quercifolia W. Bartram); Rhododendron ‘Roseum Elegans' (Rhododendron catawbiense Michx.); Mountain laurel ‘Sarah' (Kalmia latifolia L.)

Homoeopathic therapy in cervical spondylosis pain management: A randomised, double-blind, placebo-controlled trial

Background: Homoeopathic medicines are known to be effective in alleviating pain and other troublesome symptoms of patients suffering from cervical spondylosis. Objective: The primary objective was to evaluate the effectiveness of predefined homoeopathic medicines in the pain management of cervical spondylosis using the Cervical Spondylosis Pain Management Scale (CSPMS). Methods: A prospective, double-blind randomised placebo-controlled multicentric clinical trial was conducted from April 2012 to May 2013. Results: Sixty-seven cases were enrolled in the Homoeopathy group and 69 in the placebo group. One hundred and thirty-four cases that completed the follow-ups were analysed. The improvement in pain was 56.18% in the Homoeopathy group and 46.45% in the placebo group, as per CSPMS. The mean improvement between the groups was not significant: 60.36% in the Homoeopathy group and 48.66% in the placebo group. The mean score of quality of life, assessed using the 'Patient's Global Impression of Change Scale,' was 2.29 ± 1.90 quality of life in the Homoeopathy group and 2.93 ± 2.28 in the placebo group. There was 27.95% more improvement in the Homoeopathy group, as compared to the placebo group. Among the most used medicines were Rhus toxicodendron (n = 19) 28.8%, Calcarea carbonica (n = 7) 10.6%, Kalmia latifolia (n = 7) 10.6% and Paris quadrifolia (n = 8) 12.1%. Conclusion: Homoeopathic medicines are effective in management of acute pain due to cervical spondylosis.

Comparing Insect Pollinator Visitation for Six Native Shrub Species and Their Cultivars

Interest in native landscape plants to support pollinators has increased. Most native plants sold by nurseries are cultivars, and some consumer and conservation groups question the suitability of native cultivars to support pollinators. In 2017 and 2018, insect pollinator visitation was quantified for six native shrub species and one or more cultivars of each species (Aronia melanocarpa, A. melanocarpa ‘UCONNAM012’ Ground Hog®, A. melanocarpa ‘UCONNAM165’ Low Scape Mound®, Clethra alnifolia, C. alnifolia ‘Hummingbird’, C. alnifolia ‘Ruby Spice’, Dasiphora fruticosa, D. fruticosa ‘Goldfinger’, D. fruticosa ‘Pink Beauty’, Hydrangea arborescens, H. arborescens ‘Annabelle’, Kalmia latifolia, K. latifolia ‘Sarah’, Physocarpus opulifolius, and P. opulifolius ‘Monlo’ Diabolo®). Insects were identified into 12 categories (Apis mellifera, Bombus spp., Andrenidae, Halictidae, Megachilidae, other bees, Lepidoptera, Syrphidae, other flies, wasps, Coleoptera, and other insects). The number of inflorescences and insect visitation was similar for C. alnifolia and its cultivars, and the compact cultivar Hummingbird had the greatest floral density. A. melanocarpa had more total visitors of Andrenidae than both of its compact cultivars because it was larger and produced more inflorescences. Compact Aronia cultivars and the straight species were mostly similar for Andrenidae visitation when compared on a per-inflorescence basis. D. fruticosa had more visitors of Bombus spp. and Megachilidae than both of its cultivars. These insects may have been less attracted to ‘Pink Beauty’ because of its pink flower color and ‘Goldfinger’ because of its wider flowers, which result from it being a tetraploid. H. arborescens ‘Annabelle’ had one-third the number of Bombus spp. visitors as H. arborescens because ‘Annabelle’ produces &gt;50% fewer fertile florets. P. opulifolius ‘Monlo’ attracted more syrphids than P. opulifolius possibly because flowers contrasted more strongly with the reddish purple foliage of ‘Monlo’ than with the green foliage of the straight species. Insect visitation was similar for K. latifolia and K. latifolia ‘Sarah’. Based on this work, we determined that native shrub cultivars are not universally less or more attractive to pollinators and must be evaluated on a case-by-case basis.

Evaluation of Twenty-one Mountain Laurel Cultivars for Container and Landscape Performance in the Southeastern United States

Mountain laurel (Kalmia latifolia) is an outstanding ornamental shrub due to its attractive foliage and showy inflorescences. Breeding efforts have led to improved selections that have predominantly been developed and evaluated in the northeastern United States. Consequently, most cultivars have largely been dismissed as incompatible for the southeastern U.S. environmental conditions by nursery growers and consumers. This study was conducted over a 4-year period to evaluate 21 popular mountain laurel cultivars, primarily developed in the northeastern United States, for container and field performance in Georgia. All cultivars yielded considerable growth in the first year of container trials, indicating production of mountain laurel as a 1-year container crop is feasible. Cultivars displayed significantly different total growth index throughout the container trial. Fast-growing cultivars such as Bullseye and Ostbo Red yielded more than 100, 150, and 250 cm of growth index in 1, 2, and 4 years, respectively. Conversely, cultivars that grew slower, such as Firecracker and Tinkerbell, had less than 80, 115, and 180 cm in 1, 2, and 4 years, respectively. Cultivars were classified into five groups, using principal component analysis, that included dwarf habit with pink flower, dwarf habit with nonpink flower, nondwarf habit with green stem and white flower, nondwarf habit with pigment-patterned flower, and nondwarf habit with pink flower. In a field study, performance rating of 21 cultivars ranged from 2.0 to 4.8 (out of 5.0) in 2014 and from 2.0 to 5.0 in 2015. Ten cultivars that received the highest ratings over these 2 years were selected for a subsequent field trial in 2016. Cultivars showed overall decreased ratings (1.0–3.3) from the previous 2 years because of late spring planting. ‘Ostbo Red’, ‘Pristine’, and ‘Tinkerbell’ had higher performance ratings, more net growth, and less decrease in maximum quantum yield, which indicated suitable adaptation to southeastern U.S. environmental conditions. Nursery growers and consumers should benefit from regional cultivar trial information derived from this study. ‘Ostbo Red’, ‘Pristine’, and ‘Tinkerbell’ performed well across trials and therefore are recommended for southeastern U.S. landscapes based on superior container and field performance, leaf spot (caused by Mycosphaerella colorata) tolerance, and morphologic distinctions.

A comparison of three foliar-applied herbicides for controlling mountain laurel thickets in the mixed-oak forests of the central Appalachian Mountains, USA

In the Appalachian Mountains of eastern North America, mountain laurel (Kalmia latifolia) thickets in mixed-oak (Quercus spp.) stands can lead to hazardous fuel conditions, forest regeneration problems, and possible forest health concerns. Generally, land managers use mechanical means or prescribed fire to control mountain laurel thickets, but these treatments are expensive, dangerous to implement, or have short-term effectiveness. From 2012 to 2016, we compared the effectiveness of three herbicides applied as broadcast foliar treatments at varying rates and in different months for reducing mountain laurel thickets. Triclopyr (ester formulation) top-killed mountain laurel within a few weeks at most month/rate combinations, but subsequent sprouting reduced overall effectiveness by year 3. Conversely, imazapyr provided little initial control of mountain laurel, but by year 3, the herbicide had killed nearly all the treated shrubs with no subsequent sprouting regardless of the month of application or rate. Glyphosate had limited effectiveness; spraying in August at 8 and 12 L/ha killed the mountain laurel over 3 years with little sprouting while all others treatments had little or no impact. From these results, it appears that several month/rate combinations of all three herbicides have potential for controlling mountain laurel thickets and merit further testing to refine application procedures.

New 1,3-benzodioxin-4-ones from Synnemapestaloides ericacearum sp. nov., a biosynthetic link to remarkable compounds within the Xylariales.

Surveys of foliar endophytes from the Acadian forest region over the past three decades have identified numerous phylogenetically diverse fungi producing natural products toxic to forest pests and diseases. The life histories of some conifer endophytes can be restricted to plant foliage or may include saprotrophic phases on other plants tissues or even alternate hosts. Considering the potentially broad host preferences of conifer endophytes we explored fungi isolated from understory species and their metabolites as part of an ongoing investigation of fungal biodiversity from the Acadian forest. We report a hitherto unidentified Xylariomycetidae species isolated from symptomatic Labrador tea (Rhododendron groenlandicum) leaves and mountain laurel (Kalmia latifolia) collected in coastal southern New Brunswick, Canada. Morphological and phylogenetic evidence demonstrated the unknown species was a novel Synnemapestaloides (Sporocadaceae) species, described here as Syn. ericacearum. A preliminary screening assay indicated that the culture filtrate extract of the new species was potently antifungal towards the biotrophic pathogen Microbotryum violaceum, warranting an investigation of its natural products. Two natural products possessing a rare 1,3-benzodioxin-4-one scaffold, synnemadoxins A-B (1–2), and their postulated precursor, synnemadiacid A (3), were characterized as new structures and assessed for antimicrobial activity. All isolated compounds elicited in vitro inhibitory antifungal activity towards M. violaceum at 2.3 μg mL-1 and moderate antibiotic activity. Further, the characterization of synnemadoxins A-B provided a perspective on the biosynthesis of some related 1,3-benzodioxin-4-ones produced by other fungi within the Xylariales.

In Vitro Seed Germination of Kalmia latifolia L. Hybrids: A Means for Improving Germination and Speeding Up Breeding Cycle

Kalmia latifolia L. (mountain laurel), a member of Ericaceae, is a beautiful ornamental shrub native to the eastern United States. The plant is not common in the southeastern United States landscapes because of the limited heat tolerance of most commercial cultivars. Breeding of heat-tolerant cultivars can be achieved by cross hybridization, but is often challenged by low germination percentage, long germination time, and potential abortion of cross-hybridized seeds. We used in vitro seed germination to enhance germination and shorten germination time and investigated the appropriate collecting time, optimal basal medium, and pH for this approach. Collecting time affected in vitro seed germination, with more mature hybrid seeds [collected 4–5 months after pollination (MAP)] having higher germination rate (90% in 4 weeks) than the less mature seeds collected in 2 MAP (20% in 7 weeks). Seedlings from the mature seeds also produced two true leaves on average after 8 weeks of culture, whereas seedlings from the less mature seeds had no true leaves. Woody Plant Medium (WPM) better enhanced in vitro seed germination compared with Murashige and Skoog (MS) or Gamborg’s B5 (B5) medium. WPM yielded higher germination (98%) than MS (90%) and significantly greater total leaf area per seedling (67 mm3) than MS (50 mm3) and B5 (52 mm3) for seeds of ‘Firecracker’ × ‘Snowdrift’. Similar effects had been observed on seeds from ‘Little Linda’ × ‘Starburst’ and ‘Pristine’ × ‘Peppermint’. The pH ranging from 4.2 to 5.4 did not affect seed germination and seedling development of mountain laurel hybrids. Our protocol enabled early collection of mountain laurel hybrid seeds 1 month before their full maturation and permitted seeds to germinate in 4 weeks on WPM, which shortened the period from crossing to the seedling stage from up to 15 to 6 months and enhanced germination percentage from 30% to more than 90% compared with traditional seed germination. This protocol should be applied to promote the breeding and selection of new mountain laurel cultivars for the southeastern United States landscapes.