Fulya Baysal

Boxwood (Buxus sp. L.) is a very popular evergreen shrub in the United States which is widely used as landscape plant and fresh greenery. Boxwood ‘Green velvet’ (B. sinica var. insularis x B. sempervirens) plants grown in field condition exhibiting Volutella blight symptoms were found in a commercial nursery in Warren Co., Tennessee in May 2019. Leaves appeared red, brown or tan color on affected plants. Waxy, salmon pink colored fruiting bodies (sporodochia) were observed underneath the affected leaves using a hand lens (Figure 1). Leaf drop was also observed on plants. Black lesions under the bark were observed in some of the plants. The disease severity (percentage leaf area diseased) was nearly 40% and the disease incidence was nearly 30% of 1,000 plants. Infected leaf and stem tissues collected from four symptomatic plants were surface sterilized with 70% ethanol and washed with sterile distilled water. Culturing the infected leaf and stem pieces, 5-mm in size, on potato dextro...

Soilborne diseases caused by pathogens such as Phytophthora, Rhizoctonia, Fusarium, Verticillium, and Pythium species are the most important diseases of woody ornamentals. Ginkgo (Ginkgo biloba) and red maple (Acer rubrum) ‘October Glory’ plants grown in containers and fields in Tennessee have shown root and crown rot symptoms with dark brown to black lesions in 2017 and 2018. The objective of this research was to isolate and identify pathogens affecting ginkgo and red maple plants in nurseries of Tennessee and develop fungicide/biofungicide management recommendations for nursery producers. Isolations were made from the infected roots. Several Phytophthora-like colonies with spherical zoospores, filamentous to globose oogoni, and whitish mycelium, were isolated on V8-PARPH medium. For confirming identity, total genomic DNA was extracted followed by the sequence analysis of the internal transcribed spacer (ITS) regions, and large subunit (LSU) of the nuclear ribosomal RNA (rRNA) as w...

Volkamer lemon (Citrus volkameriana Ten. & Pasq., Rutaceae family) is the most commonly used rootstock for some ornamental citrus (oval kumquat and calamondin), improving the aesthetic quality of the plants and their marketable value. During the winter of 2011, symptoms of stem blight were observed on approximately 10% of 12,000 1-year-old potted C. volkameriana seedlings grown in different blocks in a commercial nursery near Catania (eastern Sicily, Italy). In the same nursery, only 1% of 15,000 older seedlings (2-year-old) showed disease symptoms. Initial symptoms included gray lesions on stems and occasionally on twigs. Later, buff lesions and gum exude appeared. Symptomatic stems and twigs were usually girdled and killed. In the lesions, irregular, dark gray sclerotia (1.0 to 5 × 1.0 to 7.0 mm, average 2.5 × 3.9 mm) were produced. In high relative humidity, cottony, white mycelia on the bark surface of infected tissues were also observed. Isolations were performed by transferrin...

Impatiens downy mildew (Plasmopara obducens (J. Schröt.) J. Schröt. (syn Peronospora obducens) was first reported in the United States in 2004, but widespread outbreaks were observed throughout North America in 2011 (5). In June 2012, symptoms, including severe defoliation while plants retained upright stems, were observed on approximately 100 landscape impatiens (Impatiens walleriana Hook.f.) in Franklin County in central Kentucky. All plants in the landscape were affected. Plants were primarily defoliated and remaining leaves were stunted, mottled, and chlorotic with edges curled downward; no flowers were present. Under examination with a dissecting microscope, white downy fungal growth was observed. Closer examination confirmed that the growth consisted of colorless sporangiophores that were mainly unbranched, straight, and rigid (1,3). Sporangiophores consisted of apical branches attached at right angles to main axes, ranging from 67.2 to 89.9 μm long (1). Sporangia were ovoid a...

Jute (Corchorus olitorius L.) is the second most important fiber crop after cotton in terms of global production (3). In November 2011, symptoms suggestive of bacterial infection were observed on a seed crop of jute at the CRIJAF research farm, Barrackpore, West Bengal, India. The disease appeared as small, brown, circular spots, usually less than 5 mm in diameter on the leaves and some of the spots were surrounded by a yellow halo. The lesions on the stems were elongated and in some cases were found to girdle the stem. In the later stages of disease, brown sunken spots were found on the green capsules. Disease incidence varied from about 20% to 90% of the total plants in different affected fields at the CRIJAF research farm. Bacterial leaf spot of jute with similar symptoms was reported in 1957 from Sudan (4). Five symptomatic and three asymptomatic leaf samples were collected from different jute fields. Bacterial colonies isolated on nutrient agar medium from infected young leaves...

Spilanthes oleracea L., popularly known as toothache plant, belongs to the family Asteraceae and is a South American native plant. Fresh leaves can be eaten for their medicinal properties or used by the cosmetics industry for their spilol contents. Plants showing leaf deformation that were collected in a field in São Paulo State, Brazil in March 2005 were suspected to be infected by a virus. Electron microscopy of leaf dip preparations of symptomatic plants revealed pleiomorphic particles typical of tospoviruses. Extracts from these plants prepared with 0.01 M sodium phosphate buffer, pH 7.0, containing 1% sodium sulfite were mechanically inoculated to indicator plants. Chenopodium amaranticolor and Gomphrena globosa were symptomless. Necrotic local lesions were observed on C. quinoa. Necrotic local lesions followed by a systemic necrosis that caused the death of the plants were observed on Datura stramonium, Nicotiana glutinosa, and N. tabacum ‘TNN’ and ‘Turkish’. Concentric rings ...

Garlic (Allium sativum L.) can be affected by a virus complex (1) consisting of two potyviruses, Onion yellow dwarf virus (OYDV) and Leek yellow stripe virus (LYSV), and two carlaviruses, Garlic common latent virus (GCLV) and Shallot latent virus (SLV) (1). To identify the components of the virus complex that could be present in garlic plants in Guanajuato State, which is the second largest garlic producer in the country and where presumptive viral symptoms were initially observed in December 2004, a survey was carried out in six locations: San Miguel de Allende and San Luis de la Paz in northern Guanajuato; Irapuato and Villagrán in the central region; and Salamanca and Valle de Santiago in the southern part of the state. Enzyme-linked immunosorbent assay (ELISA) was carried out to detect LYSV, OYDV, GCLV, and SLV in 195 garlic leaf samples collected during January 2005 from plants with leaf yellow stripe, mosaic, enation, deformation, or dwarfism symptoms. A set of primers, previo...

Transitioning farmland to certified organic vegetable production can take many paths, each varying in their costs and benefits. Here, the effects of four organic transition strategies (i.e., tilled fallowing, mixed-species hay, low-intensity vegetables, and intensive vegetable production under high tunnels), each with and without annual compost applications for 3 years prior to assessment, were characterized. Although transition cropping strategies differed in soil chemistry (P < 0.05), the magnitude of the changes typically were marginal and pairwise comparisons were rarely significant. In contrast, the compost amendment had a much greater impact on soil chemistry regardless of cropping strategy. For example, percent C and total P increased by 2- to 5-fold and K increased from 6- to 12-fold. Under controlled conditions, damping-off of both edamame soybean (cv. Sayamusume) and tomato (cv. Tiny Tim) was reduced from 2 to 30% in soils from the mixed-hay transition. In the field, da...

Pseudomonas fluorescens strains Wayne1R and Wood1R have proven capacities to improve plant health. Here we report the draft genome sequences and automatic annotations of both strains. Genome comparisons reveal similarities with P. fluorescens strain Pf-5, reveal the novelty of Wood1R, and indicate some genes that may be related to biocontrol.

Pseudomonas syringae pv. syringae (Pss), which causes bacterial canker, is the most polyphagous bacterium in the P. syringae complex due to its broad host range. This pathogen is considered the major bacterial disease in cherry orchards. In this study, several samples were collected from infected sweet cherry trees in different locations of the Marmara region in Turkey between 2016-2018. Sixty-three isolates were identified as Pss by pathogenicity, LOPAT, GATTa, and MALDI-TOF MS tests. Total genomic DNA was extracted to confirm identity, followed by PCR amplification of syrB and cfl genes. Out of 63 isolates, 12 were randomly selected for Repetitive Element Sequence-based PCR (rep-PCR) and Multilocus Sequence Typing (MLST) analysis to gain insight into the relationships of those isolates. The cluster analysis of rep-PCR (ERIC-, REP- and BOX-PCR) could classify the isolates into two distinct clusters. Phylogenetic analysis was carried out to obtain the relation between isolates and t...

Boxwood blight caused by Calonectria pseudonaviculata and C. henricotiae is destroying cultivated and native boxwood worldwide, with profound negative economic impacts on the horticulture industry. First documented in the United States in 2011, the disease has now occurred in 30 states. Previous research showed that global C. pseudonaviculata populations prior to 2014 had a clonal structure, and only the MAT1-2 idiomorph was observed. In this study, we examined C. pseudonaviculata genetic diversity and population structure in the United States after 2014, following the expansion of the disease across the country over the past 5 years. Two hundred eighteen isolates from 21 states were genotyped by sequencing 11 simple sequence repeat (SSR) loci and by MAT1 idiomorph typing. All isolates presented C. pseudonaviculata-specific alleles, indicating that C. henricotiae is still absent in the U.S. states sampled. The presence of only the MAT1-2 idiomorph and gametic linkage disequilibrium ...

Phytophthora nicotianae is the most common pathogen in nurseries and gardens, infecting both woody and herbaceous ornamental plants. Phytophthora aerial blight symptoms such dull water-soaked lesions on shoot tips and leaf petioles, girdling on the main stem, necrosis, and wilting of annual vinca were observed in a commercial greenhouse in Warren Co., Tennessee, USA in May 2016. The objective of this study was to identify the causal agent of Phytophthora aerial blight and develop a fungicide management recommendation for ornamental producers. Attempts to isolate the pathogen from symptomatic leaf tissue were conducted and excised leaf pieces were embedded in the V8 agar medium. Morphological characterization, polymerase chain reaction (PCR), sequencing, and pathogenicity test of the isolate FBG2016_444 were conducted to confirm the pathogen identification. The sequence identity was 100% identical to Phytophthora nicotianae, and a combined phylogenetic tree (internal transcribed spac...

Volutella blight is a common disease of species in the plant family Buxaceae, specifically boxwood, pachysandra, and sarcococca. Even though the disease has been consistently found over the past 150 years in all continents except for Antarctica, there are numerous complications in its etiology, signs and symptoms, and taxonomy, morphology, isolation, and preservation methods of its causal pathogens. For example, one of the two pathogens causing Volutella blight on boxwood, Pseudonectria buxi, has gone by at least 25 names including Volutella buxi and P. rousseliana, since its original description in 1815. The other Volutella blight pathogen on boxwood, P. foliicola, was not described until 2015. Although Coccinonectria pachysandricola, previously named as V. pachysandricola, has been known as a pathogen of pachysandra since 1944, it is only recently found in 2019 that the same pathogen can infect sarcococca. In this diagnostic guide, we provide a comprehensive review on the taxonomy...

Management of plant diseases is a subject of concern for researchers as well as growers. Different management practices are being developed and used to combat the rising number of plant pathogens, which threaten nursery crop production. Use of cover crops for sustainable management of soilborne diseases is being explored as an alternative strategy to the chemicals. However, the potential threat of these cover crops acting as a secondary host of these devastating soilborne pathogens has not been described. We studied the response of the major cover crops being used by woody ornamental growers in the Southeastern United States to Phytopythium vexans, Phytophthora nicotianae, and Rhizoctonia solani in greenhouse conditions to identify the effective cover crops that can be used in a nursery field production system. Data related to post-emergence damping-off and plant growth parameters (plant height increase and fresh weight) were recorded. Similarly, cover crop roots were assessed for r...

Calonectria pseudonaviculata and Pseudonectria foliicola causing the infamous “boxwood blight” and “Volutella blight,” respectively, are a constant threat to the boxwood production and cut boxwood greenery market. Both pathogens cause significant economic loss to all parties (growers, retailer, and customers) in the horticultural chain. The objective of this study was to evaluate efficacy of disinfesting chemicals (quaternary ammonium compound [QAC], peroxy, acid, alcohol, chlorine, and cleaner) in preventing plant-to-plant transfer of C. pseudonaviculata and P. foliicola via cutting tools, as well as reduction of postharvest boxwood blight and Volutella blight disease severity in harvested boxwood greenery. First, an in vitro study was conducted to select products and doses that completely or near-completely inhibited conidial germination of C. pseudonaviculata and P. foliicola. The selected treatments were also tested for their ability to reduce plant-to-plant transfer of C. pseud...

The purpose of this study was to evaluate fire ant venom alkaloids and an alarm pheromone analog against several plant pathogens, including Botrytis cinerea, Fusarium oxysporum, Phytophthora nicotianae, P. cryptogea, Pseudomonas syringae, Phytopythium citrinum, Rhizoctonia solani, Sclerotonia rolfsii, Xanthomonas axonopodis, and X. campestris. All pathogens were tested against red imported fire ant venom alkaloid extract and alarm pheromone compound for growth inhibition in in vitro assay. The venom alkaloid extract inhibited fungal and oomycete pathogens. Neither of the treatments were effective against bacterial pathogens. Three soilborne pathogens, P. nicotianae, R. solani, F. oxysporum, and one foliar pathogen, B. cinerea were selected for further in-vivo assays on impatiens (Impatiens walleriana ‘Super Elfin XP violet’). Total plant and root weight were higher in venom alkaloid treated plants compared to an inoculated control. The venom alkaloid treatment reduced damping-off, r...

Disease diagnosis is one of the major tasks for increasing food production in agriculture. Although precision agriculture (PA) takes less time and provides a more precise application of agricultural activities, the detection of disease using an Unmanned Aerial System (UAS) is a challenging task. Several Unmanned Aerial Vehicles (UAVs) and sensors have been used for this purpose. The UAVs’ platforms and their peripherals have their own limitations in accurately diagnosing plant diseases. Several types of image processing software are available for vignetting and orthorectification. The training and validation of datasets are important characteristics of data analysis. Currently, different algorithms and architectures of machine learning models are used to classify and detect plant diseases. These models help in image segmentation and feature extractions to interpret results. Researchers also use the values of vegetative indices, such as Normalized Difference Vegetative Index (NDVI), ...

The cut flower growers of the eastern and southern United States are threatened with postharvest meltdown of zinnia (Zinnia elegans), which reduces yield and income as well as limiting opportunities for production expansion. Disease symptoms such as bending of the stem just below the flower were visually apparent on zinnia cut flowers. The objective of this study was to identify the causal agent related to zinnia meltdown. A total of 20 symptomatic zinnia cut flower stems were collected from Tennessee. Several Fusarium-like colonies with micro and macroconidia were isolated from the base and bend area of stems on potato dextrose agar (PDA) and Fusarium-selective media. Morphological characterization, polymerase chain reaction, and sequencing of three representative isolates, FBG2020_198, FBG2020_199, and FBG2020_201, were conducted to confirm pathogen identification. The sequence identity of the isolates was >99% identical to Fusarium commune, and a combined phylogenetic tree gro...

Flowering cherry (Prunus serrulata Lindl. 'Kwanzan') rooted cuttings grown in propagation beds containing 40% coarse sand and 60% ground pine bark in a commercial propagation nursery in Warren County, Tennessee were exhibiting root and crown rot in December 2016. Dark brown to black soft lesions were observed in the roots as well as the crown region of flowering cherry rooted cuttings and those rooted cuttings were non-marketable due to lesions. Disease incidence was approximately 60% of 10,000 plants. Phytophthora ImmunoStrip test (Agdia Inc., Elkhart, IN, USA) was performed and the test result was positive. Diseased plant tissues were surface sterilized with 70% ethanol and washed twice with distilled water. Culturing the affected root and crown parts (1 cm pieces) on V8-PARPH, an oomycete-selective medium consistently yielded whitish radiate mycelial growth pattern with spherical zoospores, filamentous to globose oogoni, elongated, and cylindrical antheridia with constrictions (De Cock et al., 2015) after 7 days of incubation at 25°C in a 12-h fluorescent light and dark cycle, which is the typical morphology of Phytopythium vexans (de Bary) Abad, de Cock, Bala, Robideau, Lodhi & Lévesque. To confirm pathogen identity, total DNA was extracted using the UltraClean Microbial DNA Isolation Kit (MO BIO Laboratories, Inc., Carlsbad, CA, USA) directly from a 3-day old culture of isolate (FBG2017010) on V8 medium. The internal transcribed spacer (ITS) and 28S large subunit of ribosomal RNA, and cytochrome c oxidase subunit I (CoxI) of mitochondrial DNA (mtDNA) genes/ region were amplified by PCR using the primer pairs ITS1/ ITS4 (White et al., 1990), NL1/ NL4 (Baten et al., 2014), and Levup and Fm85mod (Robideau et al., 2011), respectively. The PCR products were sequenced and the sequences (GenBank accession nos. MT533275, MT533451, and MT547980) were compared to the voucher specimens. They were 99.23, 99.60, and 98.92% similar to those of P. vexans isolates in the NCBI database (HQ643400, KR092144, and HQ708996, respectively). To complete Koch's postulates, 'Kwanzan' flowering cherry rooted cuttings grown on propagation substrate (10 cm pot containing 1 kg sterilized 40% coarse sand and 60% ground pine bark) were inoculated with identified pathogen and observations were taken on root rot disease symptoms. Five plants were inoculated with 100 ml of pathogen agar-slurry (1 plate of a 7-day old culture of isolate FBG2017010/1 L of sterilized water), and five control plants were drenched with agar slurry. The plants were maintained in the greenhouse condition (day/night temperature of 26/24°C), and irrigated twice a day for 2 min by overhead irrigation system. After 2 weeks, dark brown to black necrotic root lesions developed on all inoculated cuttings and P. vexans was consistently re-isolated from the inoculated plants. The morphology of the pathogen isolated on the V8-PARPH medium was identical to the original isolate. All control plants remained symptom-free and P. vexans was not isolated from the root tissue. To our knowledge, this is the first report of P. vexans causing root and crown rot in 'Kwanzan' flowering cherry in Tennessee, which can be a potential threat for the nursery crop production. The identification of P. vexans, the causal agent of Phytopythium root and crown rot is important in determination and implementation of effective management strategies.

Ninebark (Physocarpus opulifolius) is a popular ornamental shrub and considered a hardy and tough plant that can thrive in different environmental conditions and resist diseases. However, powdery mildew, caused by Podosphaera physocarpi, can severelyaffect ninebark, deteriorating the ornamental value and making them unmarketable. Only a few studies have been done in managing powdery mildew of ninebark. The current study focuses on evaluating and identifying effective products (sanitizers, biorational products, and fungicides) for the management of powdery mildew disease of ninebark. A total of 12 treatments, including nontreated control, were studied. The experiment was arranged in randomized complete block design with four-single ‘Mindia Coppertina®’ ninebark plant per treatment and repeated twice. Powdery mildew disease severity, growth parameters, and phytotoxicity were assessed in the study. All treatments significantly reduced the powdery mildew disease severity and disease pro...

Phytophthora cinnamomi is considered one of the most destructive pathogens of ornamental crops. Different fungicides and host plant defense inducers were tested for their efficacy in managing Phytophthora root rot in drought conditions. In this study, the drought conditions were maintained by evaluating the moisture holding capacity of the pine bark in a 10.2 cm nursery container. Four controls and nine different treatments were used in two trials for this greenhouse study. All treatments were drench applied as a preventative or curative treatment. Seedlings were artificially inoculated with P. cinnamomi. Regular irrigation was carried out using overhead irrigation for one month after inoculation. Irrigation was regulated by drip irrigation after the first month. A moisture level of 15-18% of total moisture holding capacity was maintained using the gravimetric method throughout the drought period. Physiological parameters of the seedlings were recorded a week after seedlings were dr...

Magnolia trees (Magnolia sp.) are a popular choice for consumers when choosing flowering woody plants for landscapes. Magnolia species grow in a wide variety of both temperate and tropical locations. Southern magnolia (Magnolia grandiflora) is one of the more popular magnolias due to its pleasing aesthetics: large showy flowers in a range of colors and evergreen foliage. However, magnolias can be affected by algal leaf spot. Algal leaf spot is caused by Cephaleuros virescens, which is a widespread plant parasitic green alga. There has been little research on how to treat algal leaf spot on magnolia plants. This study focuses on identifying effective biological- and chemical-based fungicides for the management of algal leaf spot disease of magnolia plants. Two experiments were conducted in a randomized complete block design with six replications per treatment and a total of 12 treatments, including a nontreated control. The first experiment (Expt. 1) was conducted in a shade house (5...

Botrytis cinerea is one of the problematic and notorious postharvest pathogens of bigleaf hydrangea (Hydrangea macrophylla) cut flowers. It causes flower blight, leaf blight, and stem rot, reducing the ornamental value (such as longevity, color, and texture) of flowers, ultimately making them unsalable. The objective of this study was to identify effective conventional fungicides and biorational products for botrytis blight management on bigleaf hydrangea cut flowers that can be easily and readily adopted by growers of ornamentals. Preventive preharvest whole-plant spray and postharvest dip treatment applications were used in this study. For the whole-plant spray applications, bigleaf hydrangea plants were sprayed with treatment solution 3 days before harvesting flowers. For the dip applications, cut flowers were dipped in treatment solutions after harvest. For both application types, flowers were inoculated with B. cinerea spores once treatment solutions dried. Flowers were stored ...

Adult ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) bore into ornamental nursery trees resulting in trunk vascular tissue damage, which can potentially kill trees. Ambrosia beetle exposure to surface-applied insecticides is minimal after internal trunk galleries are formed, so effective management requires insecticide treatments to be applied near the time of infestation or to have residual activity on the bark. Tree trunk sections (bolts) were used to determine the effect of field aging or irrigation (i.e., simulated rainfall weathering) on permethrin residual activity against ambrosia beetles. In all experiments, 30-cm-long bolts from Liriodendron tulipifera L. (Magnoliales: Magnoliaceae) were hollowed and filled with 70% ethanol at field deployment to induce ambrosia beetle attacks over a 2-wk period. To evaluate insecticide residual activity, permethrin was sprayed onto tree bolts at 0, 8, 17, or 24 d before ethanol addition, and then bolts were deployed along a woode...

Abstract Ornamental production systems are complicated to manage due to the many species and genera that may be grown and handled together on a single production site. Ornamentals are threatened by various phytopathogenic fungi in greenhouse and field production. Among these, Botrytis cinerea is one of the most notorious pathogens of ornamentals, specifically cut flowers. B. cinerea is responsible for causing Botrytis blight disease in both pre- and post-harvest conditions. The pathogen infects leaves, stems, flowers, etc., and causes petal specking, flower blight, sepal yellowing, and peduncle bending, among other symptoms. The ability of B. cinerea to cause disease in greenhouses and fields, as well as in subsequent handling, storage, and transportation, makes this fungus an important pathogen due to its potential negative economic effects on the cut flower industry. For the management of B. cinerea, the routine application of fungicides is considered a major tool in commercial production. However, fungicide resistance, phytotoxicity, application residues, environmental concerns, and health issues have forced growers to seek alternative management approaches. In this review paper, we discuss the different approaches (classic to novel strategies) used for B. cinerea management, including chemical methods and their modes of action. The integration of new practices with existing management strategies (sanitation, nutrition, plant regulators, botanical extracts, biological control, fungicides) could provide effective results in ornamental production systems. Understanding the ecology of pathosystems, disease epidemiology and the integration of all possible management measures as a system approach may also provide adequate disease suppression in both pre- and post-harvest conditions.

Eastern ninebark (Physocarpus opulifolius (L.) Maxim.) is a popular native perennial plant used in landscapes because of its colorful foliage and spring flower display. Powdery mildew symptoms were observed on container-grown eastern ninebark ‘Mindia’ Coppertina® plants in a commercial nursery in DeKalb County, TN in May 2016. The disease severity was nearly 40% and the disease incidence was nearly 60% of 1,000 plants. Affected plants displayed witches’-brooms with cream to white colored, thickened shoots with stunted, curly leaves as well as patches of white powdery fungal growth on the surface of young and old leaves, inflorescences, infructescences and stems (Figures 1 and 2). Microscopic observation revealed masses of conidia and mycelium covering symptomatic tissues. Conidiophore foot cells measured 19.2 to 66.7 μm (mean = 38.3 μm) × 5.4 to 15.1 μm (mean = 9.7 μm) (n = 30). Conidia were ovoid and measured 11.4 to 28.5 μm (mean = 20.9 μm) (n = 30) in length and 8.2 to 14.8 μm (m...

Diseases caused by soilborne pathogens are a major limitation to field grown nursery production. The application of cover crops for soilborne disease management has not been widely investigated in a woody ornamental nursery production system. The objective of this study was to explore the impact of winter cover crops usage on soilborne disease management in that system. Soils from established field plots of red maple (Acer rubrum L.) with and without winter cover crops (crimson clover (Trifolium incarnatum L.) or triticale (× Triticosecale W.)) were sampled following the senescence of the cover crops. Separate bioassays were performed using red maple cuttings on inoculated (with Phytopythium vexans, Phytophthora nicotianae or Rhizoctonia solani) and non-inoculated field soils. The results indicated that winter cover crop usage was helpful for inducing soil disease suppressiveness. There was lower disease severity and pathogen recovery when the cover crops were used compare to the no...

Ornamental plants in the genus Phlox are extensively planted in landscapes and home gardens around the world. A major limitation to a more widespread use of these plants is their susceptibility to powdery mildew (PM). In this study, we used multilocus sequence typing (MLST) analysis to gain insights into the population diversity of 32 Phlox PM pathogen (Golovinomyces magnicellulatus and Podosphaera sp.) isolates collected from the eastern United States and relate it to the ability to overcome host resistance. Low genetic diversity and a lack of structure were found within our population. Whole genome comparison of two isolates was used to support low genetic diversity evidence found with the MLST analysis. Recombination was suggested by the incongruences observed in the six phylogenetic trees generated from the housekeeping genes TEF-1α, CSI, ITS, IGS, H3, and TUB. Contrasting with low genetic diversity, we found high phenotypic diversity when using 10 of the 32 isolates to evaluate...

Soilborne pathogens are a significant economic problem for nursery production in the Southeastern United States. The goal of this study was to determine the impact of cover crops on soilborne disease suppressiveness in such systems. Soils from red maple (Acer rubrum L.) plantation fields grown with and without cover crops were sampled, either while the cover crops were growing (pre-disked) or post-season, following cover crop incorporation into the soil (post-disked). Greenhouse bioassays were conducted using red maple seeds on inoculated (with Rhizoctonia solani (J.G. Kühn) or Phytophthora nicotianae (Breda de Haan)) and non-inoculated field soils. The damping-off, root rot disease severity, percent recovery of Rhizoctonia and Phytophthora, and pseudomonad population were examined during the two years of the experiment. Results showed that cover crop incorporation was beneficial for inducing disease supressiveness characteristics of soil. Cover crop incorporation into the soil sign...

Numerous sensors have been developed over time for precision agriculture; though, only recently have these sensors been incorporated into the new realm of unmanned aircraft systems (UAS). This UAS technology has allowed for a more integrated and optimized approach to various farming tasks such as field mapping, plant stress detection, biomass estimation, weed management, inventory counting, and chemical spraying, among others. These systems can be highly specialized depending on the particular goals of the researcher or farmer, yet many aspects of UAS are similar. All systems require an underlying platform—or unmanned aerial vehicle (UAV)—and one or more peripherals and sensing equipment such as imaging devices (RGB, multispectral, hyperspectral, near infra-red, RGB depth), gripping tools, or spraying equipment. Along with these wide-ranging peripherals and sensing equipment comes a great deal of data processing. Common tools to aid in this processing include vegetation indices, poi...

Flowering dogwood (Cornus florida) is a valuable nursery product typically produced as a field-grown crop. Container-grown flowering dogwood can grow much faster than field-grown plants, thus shortening the production cycle, yet unacceptable crop loss and reduced quality continue to be major issues with container-grown plants. The objective of this research was to evaluate the effects of container size and shade duration on growth of flowering dogwood cultivars Cherokee Brave™ and Cherokee Princess from bare-root liners. In 2015, bare-root liners were transplanted to 23-L (no. 7) containers and placed under shade for 0 months (full sun), 2 months (sun4/shade2), 4 months (sun2/shade4), or 6 months (full shade) during the growing season. In 2016, one-half of the plants remained in no. 7 containers and the other half were transplanted to 50-L (no. 15) containers and assigned to the same four shade treatments. In 2015, plant height was greatest with full shade for both cultivars, wherea...

Abstract Phytophthora root rot is one of the most important diseases in almost all hydrangeas of nursery production. In this study, the efficacy of fungicides and biocontrol products against Phytophthora root rot of hydrangea was assessed in greenhouse and field experiments. Treatments used in field or greenhouse experiments were RootShield PLUS+, MBI110, IT-5103, Grotab, OxiPhos, TerraClean 5.0 + TerraGrow program, Segovis, Pageant Intrinsic, Empress Intrinsic and Subdue Maxx. Pots/plots were inoculated with Phytophthora nicotianae grown on rice grains, sterilised rice grains were used for negative controls. After the trials, plant growth data (total plant weight, root weight, plant height, plant width) were recorded, and roots were assessed for disease severity using a scale of 0–100%. The treatments most effective in reducing Phytophthora root rot severity were Segovis, Empress Intrinsic, Subdue Maxx, TerraClean 5.0 + TerraGrow program in both greenhouse and field experiments. This study will help nursery producers make proper management decisions by using recommended fungicides and biocontrol products of this study in a rotation or alone to manage Phytophthora root rot of hydrangea.

Abstract Phytophthora root rot causes major economic losses in woody ornamental nurseries, especially in plants exposed to flooding. Ambrosia beetles, which attack stressed trees, are also important pests of woody plants. In this study, several products were evaluated for control of Phytophthora root rot and ambrosia beetles on containerized flowering dogwoods (Cornus florida L.) exposed to simulated flood events under field conditions. In two trials, preventive (7 days preflooding) or curative (1 day postflooding) sprench (combination spray and drench) treatments were applied to containerized dogwoods artificially inoculated with Phytophthora cinnamomi Rands. The plants were flooded by maintaining standing water for 1, 3, or 7 days. After the trials, plant growth data (dry shoot weight, dry root weight, plant height, plant width, caliper) were recorded, and roots were assessed for disease severity using a scale of 0–100% roots affected, as well as plated on PARPH-V8 medium to determine the percentage of Phytophthora-infected root samples. Ambrosia beetle attacks were recorded throughout the study. Longer flooding duration increased disease pressure from Phytophthora cinnamomi Rands. Preventive treatment of plants with Subdue MAXX consistently reduced disease severity at tested flooding durations of 1, 3, or 7 days. Preventively- (before flooding) or curatively- (after flooding) applied treatments of Empress Intrinsic, Orkestra Intrinsic, and Pageant Intrinsic reduced disease pressure at 1 and 3 days of flooding. Preventive RootShield Plus+ treatment reduced disease pressure on plants flooded 1 day. Longer flooding periods as well as Phytophthora cinnamomi inoculation increased ambrosia beetle attacks on flooded dogwoods, but preventively- and curatively-applied Orkestra Intrinsic as well as preventively-applied Subdue MAXX reduced ambrosia beetle attacks compared to non-treated, inoculated controls. These treatments were effective at reducing both Phytophthora and ambrosia beetle damage. These results can help nursery producers successfully manage Phytophtora root rot and also reduce the risk of ambrosia beetle attacks during flood events.

Witchhazel (Hamamelis sp.) cultivars are now available in an array of forms and flower colors, including several native, pollinator-friendly cultivars. However, little is known about response of witchhazel cultivars to powdery mildew (Podosphaera biuncinata) or the growth and flowering characteristics of witchhazel cultivars in a nursery field production setting. To provide growth, flowering, and disease incidence data to nursery growers, a cultivar trial including 23 cultivars of witchhazel representing five species was planted Apr. 2016 in McMinnville, TN. Plant growth, flowering density, length of bloom, and foliar disease incidence were evaluated over three growing seasons between May 2016 and Oct. 2018. ‘Zuccariniana’ japanese witchhazel (H. japonica) and ‘Sunglow’ common witchhazel (H. virginiana) showed the greatest height increase during the trial, and ‘Sunglow’ also added the most width during the trial. Cultivars with negative height or width growth included Sweet Sunshine...

Abstract Soil-borne diseases can reduce nursery crop performance and increase costs to nursery producers. In particular, soil-borne diseases caused by Phytophthora nicotianae and Rhizoctonia solani are the most economically important problems of Southeastern United States nursery producers. Methyl bromide was widely used as a standard treatment for management of soil-borne diseases until the implementation of the Montreal protocol. Since then, many chemical and non-chemical soil-borne disease management methods have been tested, but are not yet providing effective and consistent results like methyl bromide. Cover crops that belonged to the Brassicaceae family can be incorporated into the soil to control soil-borne diseases and this process is widely known as biofumigation. But, the use of Brassicaceae cover crops has not been widely explored as a method of controlling soil-borne diseases in woody ornamental nursery production. The objective of this study was to evaluate Brassicaceae cover crops for susceptibility to most destructive soil-borne pathogens of nursery production, P. nicotianae and R. solani, to identify effective cover crops that can be used in the biofumigation process in woody ornamental nursery production. Brassica species intended to be used in the fresh market or biofimigation were screened for their susceptibility to R. solani and P. nicotiane in an environmentally controlled greenhouse. At the end of experiments, plant growth data (plant height, width and fresh weight), total damping-off were recorded, and cover crop root systems were assessed for disease severity using a scale of 0–100% roots affected. Among the tested 15 cover crops in the Brassicaceae family, oilseed radish (Raphanus sativus L.), yellow mustard “White Gold” (Sinapis alba L.), turnip “Purple Top Forage” (Brassica rapa L.), arugula “Astro” (Eruca vesicaria (L.) Cav. ssp. sativa (Mill.) Thell.), mighty mustard® “Pacific Gold” (B. juncea (L.) Czern.), brown mustard “Kodiak” (B. juncea (L.) Czern.), rape “Dwarf Essex” (B. napus L.) and mustard green “Amara” (B. carinata A. Braun) showed numerically lower root rot disease severity and total damping-off in topsoil which had pre-existing populations of R. solani or P. nicotinanae compared to other cover crops. Since these above mentioned Brassicaceae crops shows the ability to withstand the higher disease pressure from R. solani and P. nicotinanae under the greenhouse conditions they can be used in the further experiments to evaluate their ability in biofumigation. Further research is necessary to evaluate the performance of these cover crops under the field conditions.

Abstract Soilborne diseases are the most economically important problem for ornamental nursery producers in the southeastern United States. The use of cover crops selected based on their biofumigant activity to improve soilborne disease management in woody ornamental production was assessed. Replicated pot bioassays were established as greenhouse trials in sterilized clay loam soil which had pre-existing populations of Rhizoctonia solani or Phytophthora nicotianae. Selected Brassica crops were seeded directly into the soil and flowering cover crops were incorporated 15 cm deep into the same pots and covered with polyethylene for 2 or 4 weeks. Volatile compounds released during the biofumigation process were collected at different time intervals. Soil type and moisture affected ITC release. Hydrangea or viburnum rooted cuttings were grown in the biofumigated (2 or 4 weeks) and non-biofumigated control pots and root rot disease severity was evaluated at the end of each bioassay. Yellow mustard (Sinapis alba, ‘White gold’), turnip (Brassica rapa, ‘Purple top forage’), arugula (Eruca vesicaria ssp. sativa, ‘Astro’), Mighty mustard (B. juncea, ‘Pacific gold’), rape (B. napus, ‘Dwarf essex’), mustard green (B. carinata, ‘Amara’) and brown mustard (B. juncea, ‘Kodiak’) cover crops were effective in suppressing R. solani and P. nicotianae. Similar disease suppression was observed whether biofumigation was performed for 2 or 4 weeks. Phytotoxicity was not observed on viburnum and hydrangea woody ornamental plants after either the 2 or 4 weeks biofumigation period with any of the tested cover crops. Viburnum and hydrangea grown in mustard green-, arugula- and turnip-incorporated soil had significantly higher whole plant and root fresh weights compared with the inoculated, non-biofumigated control plants. Although mustard green and arugula are not used currently as commercial biofumigation cover crops, they also showed promise for controlling soilborne pathogens of woody ornamental plants under greenhouse conditions.

Soilborne diseases are the most economically significant problem faced by Southern region nursery producers. The goal of this research was to improve Rhizoctonia root rot disease management through the use of soil solarization alone and in combination with biofumigant cover crops—arugula ‘Astro’ (Eruca vesicaria ssp. sativa), mustard green ‘Amara’ (Brassica carinata), and turnip ‘Purple top forage’ (B. rapa); good quality compost and mustard meal amendment. The experiments were established as on-farm trials in 2016 and 2017 with prevalent Rhizoctonia solani population in propagation beds. All three biofumigant cover crops, arugula ‘Astro’, mustard green ‘Amara’, and turnip ‘Purple top forage’ in combination with solarization were able to reduce the Rhizoctonia root rot in flowering cherry ‘Kwanzan’ plants in nursery propagation beds. Compost amendment increased the flowering cherry rooted cuttings growth (plant weight, root weight, and plant height) compared to other treatments. Soi...

Soilborne diseases reduce crop performance, increase costs to the nursery producers, and can cause potential ecological damage to the natural environment. In particular, soilborne diseases caused by Phytophthora nicotianae and Rhizoctonia solani are the most economically important problems of southeastern U.S. nursery producers. Methyl bromide was widely used as a standard treatment in many parts of the world until the implementation of the Montreal Protocol. Since then, many chemical and nonchemical soilborne disease management methods have been tested but are not yet providing effective and consistent results like methyl bromide. Cover crops that belong to the Brassicaceae family can be incorporated into the soil to control soilborne diseases, and this process is widely known as biofumigation. Glucosinolates that are available inside Brassicaceae plant cells can be hydrolyzed into isothiocyanates, and these compounds are proven to be highly biocidal to many microorganisms (includi...

Flooding can increase tree susceptibility to root rot pathogens as well as attacks by ambrosia beetles attracted to stress-induced ethanol emissions. The objective of this study was to investigate the interaction of a preventative fungicide treatment and root infection with Phytophthora cinnamomi on ambrosia beetle attacks in flood stressed trees. A fungicide (Pageant® Intrinsic®) was evaluated in two flood trials using Eastern redbud and tulip poplar trees with treatments including the fungicide with or without pathogen or no fungicide with or without pathogen. Fungicide treated trees had fewer ambrosia beetle attacks, particularly in trees without P. cinnamomi co-infection. In a follow-up experiment, ethanol content was evaluated in flooded redbuds to determine if the fungicide treatment reduced stress-induced compounds. All flood stressed trees began producing ethanol within 24 h post flooding, regardless of fungicide treatment or P. cinnamomi infection. We conclude that pre-trea...

Putative strains belonging to Xanthomonas spp. causing leaf spot and blight diseases on geranium (Pelargonium peltatum and P. hortorum), begonia (Begonia × tuberhybrida), anthurium (Anthurium andraeanum), Chinese hibiscus (Hibiscus rosa-sinensis), and English ivy (Hedera helix) growing in Turkey were isolated. All bacterial strains were classified as Gram-negative, oxidase negative, catalase, levan and starch hydrolysis positive, with hypersensitive reaction positive on tobacco and pathogenic to host plants. Identification of these strains was further confirmed by serological method using ELISA kits, conventional PCR, carbon utilisation, and FAME. Results of the identification showed that 28, 24, 10, 2, and 1 strains were identified as X. axonopodis pv. begoniae, X. hortorum pv. pelargonii, X. axonopodis pv. dieffenbachiae, X. hortorum pv. hederae, and Xanthomonas sp., respectively. This is the first report of X. hortorum pv. hederae on English ivy in Turkey.

Citrus rootstocks, Carrizo citrange (Citrus sinensis [L.] Osb. × Poncirus trifoliata [L.] Raf.) and sour orange (C. aurantium L.) grown in containers filled with 5 liters of potting mix of 40% peat and 60% volcanic tuff declined in a 0.2-ha commercial nursery in Adana, Turkey, between 2004 and 2007. Seedlings with symptoms of root rot were found with an average disease incidence of 20% among 1,000 Carrizo citrange seedlings and 10% among 15,000 sour orange seedlings. The potting mixture preparation unit was located next to an oak tree (Quercus sp.) showing symptoms of Armillaria root rot. Six- to 12-month-old seedlings of both rootstocks were stunted and the crowns were necrotic with the presence of white mycelium. Mycelial fans were observed beneath the bark of infected roots and they expanded into the crown. The root systems and nearby potting mix contained rhizomorphs. Thus, Armillaria spp. was suspected as a possible causal agent. Three diseased crowns and three rhizomorphs were...