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Boxwood (Buxus spp.) is the most commonly cultivated woody ornamental shrubs in landscape settings and nursery production. Boxwood is grown for its attractive evergreen foliage and versatility in both formal and informal gardens. Meeting the high demand for boxwood plants worldwide has become challenging in recent years as the boxwood industry has been negatively impacted by a growing number of serious diseases and arthropod pests. Globally, the most common arthropods of concern are boxwood leafminer (Monarthropalpus flavus, Diptera: Cecidomyiidae), boxwood psyllid (Psylla buxi; Hemiptera; Psyllidae), Eurytetranychus buxi (Acari: Tetranychidae) and the invasive moth, Cydalima perspectalis (Lepidoptera: Crambidae). Moreover, major diseases of boxwood include boxwood blight (Calonectria pseudonaviculata , Hypocreales: Nectriaceae), Volutella blight (Pseudonectria buxi , Hypocreales: Nectriaceae), and Phytophthora root and crown rot (Phytophthora spp. Peronosporales: Peronosporaceae). These pests and diseases can lead to significant economic losses to growers and can decimate plants in landscape settings. Here we have reviewed recent research advances focused on the description and management of boxwood arthropod pests and diseases. Boxwood arthropod pests and diseases can be managed by implementing integrated arthropod pest and disease management strategies such as sanitary and cultural practices, genetic resistant cultivars, biological and chemical control methods. This information is provided to aid nursery producers, landscape industry professionals, and other stakeholders in developing integrated arthropod pest and disease management plans for boxwood. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 severely affect 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 CoppertinaVR' 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 progress [area under disease progress curve (AUDPC)] compared with the nontreated control. The treatments, such as azoxystrobin + benzovindiflupyr at 0.17 and 0.23 g·L-1 total active ingredients (a.i.) applied, chlorothalonil + propiconazole at 1.12 mL·L-1 total a.i. applied, azoxystrobin + tebuconazole at 0.11 and 0.16 g·L-1 total a.i. applied, and giant knotweed extract [Reynoutria sachalinensis (0.5 mL·L-1 total a.i. applied)] were the most effective treatments in reducing disease severity and disease progress in both trials. The treatments had no significant effects on the plant growth parameters such as height and width. In Expt. 2, azoxystrobin + benzovindiflupyr and hydrogen peroxide + peroxyacetic acid treated plants showed the low level of phytotoxic symptoms. The phytotoxicity of these two treatments in Expt. 2 could be related to higher environmental temperature during the experimental period. [ABSTRACT FROM AUTHOR]

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 County, TN, U.S.A., 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 V8 agar medium. Morphological characterization, PCR, sequencing, and pathogenicity test of the isolate FBG2016_444 were conducted to confirm the pathogen identification. The sequence identity was 100% identical to P. nicotianae , and a combined phylogenetic tree (internal transcribed spacer, large subunit of rDNA, and ras-related protein gene) grouped isolate FBG2016_444 within the clade of P. nicotianae . In the pathogenicity study, all inoculated annual vinca plant showed Phytophthora aerial blight symptoms, and P. nicotianae was reisolated, whereas noninoculated annual vinca plant remained symptomless. These findings confirmed P. nicotianae as the causal agent of Phytophthora aerial blight of annual vinca. In addition, two rates (0.078 and 0.156 ml·liter -1 ) and three application intervals (7, 14, and 21 days before inoculation [DBI]) of oxathiapiprolin (Segovis) were evaluated for their ability to reduce the Phytophthora aerial blight severity on annual vinca plants. The control groups were positive (nontreated inoculated) and negative (nontreated noninoculated) plants. Both rates and application timings of oxathiapiprolin significantly reduced Phytophthora aerial blight severity and disease progress (area under disease progress curve [AUDPC]) on annual vinca plants compared with the positive control. However, 0.078 and 0.156 ml·liter -1 of oxathiapiprolin applied at 7 or 14 DBI were the most effective treatments in reducing the disease severity and AUDPC on annual vinca plants. The plant growth parameters such as increase in height and width, total plant weight, and root weight were not influenced by the application of oxathiapiprolin. The findings reported in this study will help ornamental producers with better management of Phytophthora aerial blight of annual vinca.

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. pseudonaviculata and P. foliicola and manage postharvest boxwood blight and Volutella blight in boxwood cuttings. For the plant-to-plant transfer study, Felco 19 shears were used as a tool for mechanical transfer of fungal conidia. The blades of Felco 19 shears were exposed to a conidial suspension of C. pseudonaviculata or P. foliicola by cutting a 1-cm-diameter cotton roll that had been dipped into a fungal suspension. Disease-free boxwood rooted cuttings (10-cm height) were pruned with the contaminated shears. The Felco 19 shears were equipped with a mounted miniature sprayer connected to a pressurized reservoir of treatment solution that automatically sprayed the blade and plant surface while cutting. The influence of accumulated sap on the shear blade was studied through 1- or 10-cut pruning variable on test plants and screened for the efficacy of treatments. Then, the boxwood rooted cuttings were transplanted and incubated in room conditions (21°C, 60% RH) with 12 h of fluorescent light; data evaluation on disease severity was done weekly for a month. Disease progress (area under disease progress curve [AUDPC]) was calculated. In another study, postharvest dip application treatments were used for the management of postharvest boxwood blight or Volutella blight on boxwood cuttings. The harvested boxwood cuttings were inoculated with a conidial suspension of C. pseudonaviculata or P. foliicola and then dipped into treatment solution 3 days afterward. The treated boxwood cuttings were kept in room conditions, and boxwood blight or Volutella blight disease severity as well as marketability (postharvest shelf life) was assessed every 2 days for 1 week. A significant difference between treatments was observed for reduction of boxwood blight or Volutella blight severity and AUDPC. The treatments [Octyl decyl dimethyl (ODD) + dioctyl dimethyl (DoD) + didecyl dimethyl (DdD) + dimethyl benzyl (DB)] ammonium chloride (AC) (Simple Green D Pro 5), 2-propanol + didecyl dimethyl ammonium chloride (DDAC) (0.12%; KleenGrow), and dimethyl benzyl ammonium chloride (DBAC) + dimethyl ethylbenzyl ammonium chloride (DEAC) (GreenShield) were the most effective in reducing the plant-to-plant transfer of boxwood blight and Volutella blight when pruned with contaminated Felco 19 shears. In addition to the three effective treatments above, acetic acid (2.5%; vinegar), 2-propanol + DDAC (0.06%), sodium hypochlorite (Clorox), and potassium peroxymonosulfate + NaCl (2%; Virkon) were effective in reducing postharvest boxwood blight, whereas DBAC + DBAC (Lysol all-purpose cleaner), ethanol (70% [ethyl alcohol]), and DDAC + DBAC (Simple Green D Pro 3 plus) were effective in reducing Volutella blight disease severity and AUDPC, and they also maintained better quality and longer postharvest shelf life of boxwood cuttings when applied as a dip treatment. The longer postharvest shelf life of boxwood cuttings noted may be attributed to reduced disease severity and AUDPC resulting in healthy boxwood cuttings.

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 dextrose agar (PDA) consistently yielded white fluffy aerial mycelium growth with scattered salmon-color slimy masses of conidia forming from sporodochia after 10 days incubation at 25°C in a 12-h fluorescent light and dark cycle. A total of two isolates (FBG2020_396 and FBG2020_405) were hyphal tip purified on PDA. The conidia (n = 50) were hyaline, aseptate, fusiform to ellipsoidal measuring average of 7.8 × 3.3 μm (range: 4.84 to 13.2 μm × 2.2 to 4.64 μm). To confirm the pathogen identity, total DNA was extracted using UltraClean Microbial DNA Isolation Kit (MO BIO Laboratories, Inc., Carlsbad, CA) directly from a 5-day old culture of isolates (FBG2020_396 and FBG2020_405) on PDA. The ribosomal DNA internal transcribed spacer region (ITS), β-tubulin (tub2) and part of 28S large ribosomal subunit (LSU) regions were amplified by PCR using the primer pairs ITS 5/ITS 4, T1/BTb2 and LR0R/LR5, respectively (Glass and Donaldson 1995; O'Donnell and Cigelnik 1997; Rehner and Samuels 1994; Vilgalys and Hester 1990; White et al. 1990). Newly generated sequences - GenBank/NCBI acc. nos. MW459251, MW465902 (ITS), MW464656, MW464657 (tub2) and MW459255, MW465903 (LSU) were 100% identical to Pseudonectria foliicola L. Lombard & Crous ex-type (CBS 123190) sequences KM231776, KM232035 and NG_058095, respectively. To complete Koch's postulates, six boxwood 'Green velvet' plants grown in 10 cm square pots (containing 40% coarse sand and 60% ground pine bark) were inoculated by spraying conidial suspension of P. foliicola [FBG2020_396 (1 × 10 5 conidia/mL)] obtained from 2-wk-old PDA cultures. Plants were covered with clear plastic humidity domes for 3 days and then they were maintained in a growth chamber at 25°C and 60% RH in a 12-h fluorescent light and dark cycle. Six control boxwood plants were maintained in the same environment without pathogen introduction. Pathogenicity test was conducted twice. After 10 days, typical symptoms of Volutella blight developed on the inoculated plants and microscopic examination revealed the same pathogen morphology as the original isolate. Pseudonectria foliicola was consistently re-isolated from leaves and stems. All control boxwood plants remained symptom-free and P. foliicola was not isolated from the leaves or stems. Pseudonectria foliicola causing Volutella blight has been reported on B. sempervirens in Czech Republic (Spetik et al. 2020), New Zealand (Lombard et al. 2015); Buxus sp. in Illinois, Maryland, Massachusetts, North Carolina and Washington (Salgado-Salazar et al. 2019). To our knowledge, this is the first report of Volutella blight of boxwood caused by P. foliicola in Tennessee. Pseudonectria foliicola is an opportunistic pathogen and infects weak, stressed, and injured boxwood plants/cuttings (Rivera et al. 2018). This pathogen could cause a serious economic loss to boxwood nursery growers, as it can significantly affect the ornamental value of boxwood plants and fresh greenery. Integration of sanitation practices with other disease management strategies such as biorational products and reduced-risk fungicides will be necessary for limiting the spread of pathogen and successful management of P. foliicola on boxwood in both field and postharvest 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 (mean = 11.7 μm) (n = 30) in width. Conidiophores produced two to six conidia in chains. Fibrosin bodies were observed after treating conidia with a 3% KOH solution. Chasmothecia were numerous, 60.0 to 85.0 μm (mean = 74.2 μm) (n = 30) in size and contained one ascus [60.0 to 82.0 × 52.0 to 69.0 μm; mean = 73.4 × 59.4 μm (n = 30)] with 8 ascospores [25.2 to 28.0 × 14.8 to 16.0 μm; mean = 26.5 × 15.5 μm (n = 30)]. To confirm pathogen identity, total DNA was extracted directly from plant tissue with the UltraClean Microbial DNA Isolation Kit (MO BIO Laboratories, Inc., Carlsbad, CA) following the manufacturer's instructions. The ITS region of the ribosomal DNA was amplified by PCR using primer pair ITS1 and ITS4 (White et al. 1990). The sequence (GenBank acc. no. MT605142) of the amplicon had 100% coverage and 100% identity to that of Podosphaera physocarpi (U. Braun) U. Braun (= Podosphaera aphanis var. physocarpi (U. Braun) U. Braun & S. Takam.) (GenBank acc. no. MT106654). Pathogenicity was confirmed three times by inoculating leaf surfaces of five eastern ninebark 'Mindia' Coppertina® plants by tapping fungal spores from infected eastern ninebark leaves onto the surfaces of healthy leaves. Inoculated plants were maintained in a greenhouse (21 to 23°C) using drip irrigation system until symptoms developed. Five non-inoculated control plants were maintained in the same greenhouse. After two weeks, typical symptoms of powdery mildew developed on the inoculated plants and microscopic examination revealed the same pathogen morphology as the original isolate. All non-inoculated control plants remained disease-free. To our knowledge, this is the first report of powdery mildew caused by P. physocarpi on P. opulifolius in Tennessee. Powdery mildew is known to be a disease problem on eastern ninebark grown in its native range in landscape plantings. Lubell et al. (2011) reported varying levels of powdery mildew resistance among eastern ninebark cultivars. Timely application of fungicides with no phytotoxic effect will be necessary to manage this disease on susceptible eastern ninebark cultivars in affected nurseries.