The pour-through (PT) method is used in greenhouse and nursery production to monitor nutrient availability in soilless substrates. Efficacy of this method is based on the assumption that chemical properties of extracted solutions remain stable from the moment of collection until analysis. Extracted substrate solution can be analyzed directly in the greenhouse or sent to laboratories for complete nutritional analysis; thus, proper sample preservation methods (e.g., filtration and low temperatures) are critical for reducing sample contamination or degradation during storage. However, evidence of how these preservation methods affect chemical characteristics of PT samples is limited. The objective of this study was to evaluate the effect of storage time, storage temperature, and filtration of PT samples on pH, electrical conductivity (EC), and nutrient concentrations from pine bark– and peat-based substrates. PT extracts were obtained from liquid-fertilized fallow pots of either 100% milled pine bark (Expt. 1) or a 4 sphagnum peat: 1 perlite (by volume) substrate (Expt. 2). Aliquots of PT extract were either filtered or nonfiltered and then stored in plastic bottles at −22, 4, or 20 °C. EC, pH, and nutrient concentrations were analyzed at 0, 1, 7, and 30 days after PT sample collection. EC and pH in PT extracts of peat and pine bark, respectively, changed 1 day after collection. Storage time had the greatest effect on nutrient concentrations of samples stored at 20 °C. However, at day 30, nutrient concentrations had also changed in samples stored at 4 and −22 °C. Analytes that fluctuated most in both experiments and across all preservation treatments were dissolved organic carbon, total dissolved nitrogen, NO ₃ ⁻ -N, and PO ₄ ³⁻ -P, whereas Ca ²⁺ , Mg ²⁺ , and SO ₄ ²⁻ -S were more stable in PT samples. This research suggests EC and pH should be analyzed immediately, whereas samples requiring nutrient analysis should be filtered immediately after collection, stored at 4 or −22 °C (preferably −22 °C), and analyzed within 7 days of collection.

Scrub titi (Cyrilla arida), broadleaf semi-evergreen shrub, is endemic to central Florida. However, its smaller stature, lustrous, dark-green leaves and abundance of white racemes in late spring make it a potential candidate for future use in Southeastern U.S. landscapes. Three-years-old container grown C. arida plants maintained in a shade house at the Nursery Research Center, McMinnville, TN exhibited black leaf lesions and brown stem lesions (Fig. 1a) in April 2023. The disease severity was 25% of the shoot area and the disease incidence was 10% out of 60 plants. Symptomatic stem and leaf tissues were surface sterilized with 0.525% NaOCl for 1 min. Bacterial colonies were white-colored, opaque, round with smooth edges on lysogen broth agar medium after 2 days of incubation at 28°C. Bacteria were gram-negative and non-fluorescent on King's B. Esculin, catalase, and oxidase tests were positive but arginine dihydrolase and gelatine hydrolysis were negative. Bacterial identity was confirmed by sequencing of DNA from pure cultures (strains FBG5290 and FBG5294). The 16S ribosomal RNA, RNA polymerase sigma factor (rpoD), enolase (eno), and NADH-quinone oxidoreductase subunit L (nuoL) genes were amplified and sequenced using the primers 8F/1492R (Galkiewicz et al. 2008), rpoDpF/R (Sarkar and Guttman 2004), enoP1/P2 and nuoLP1/P2 (Spilker et al. 2012), respectively. The sequences were deposited in GenBank with acc. nos.: OR689356, OR689357 (16S); OR751366, OR751367 (rpoD); OR792456, OR792457 (eno); and OR792458, OR792459 (nuoL). The closest identified species to our two identical strains was Achromobacter xylosoxidans (CP054571), showing 99.6%, 95.2%, 96.2%, and 95.0% identity with >99% coverage to the above mentioned gene sequences, respectively. Phylogenetic analysis, using concatenated sequences along with the genome sequences of other closely related taxa (Fig. 2), suggest that A. xylosoxidans is presently the identified species, but given the results of the MLST, it may be that this organism will be classified as new species in the future. The pathogenicity of the strains was confirmed on 1-year-old C. arida by inoculating five plants per strain. Stems were inoculated by depositing 15 µl of bacterial suspension (1x10⁸ CFU/mL) into the stem wounded using a scalpel. The inoculation sites were covered with moist cotton and wrapped with Parafilm. Inoculation was also performed on three leaves per plant by using a needleless syringe to infiltrate bacteria into the intercellular spaces (1x10⁸ CFU/mL). Sterile water was used for five control plants. Plants were kept in a greenhouse at 21-23°C, 70% RH, and 16-h photoperiod. All inoculated plants showed brown lesions in stems (Fig. 1b and 1c) and leaves (Fig. 1d) 7-10 days after inoculation, while control plants remained asymptomatic (Fig. 1e and 1f). The bacteria were re-isolated from inoculated plants and confirmed as A. xylosoxidans using morphological and molecular methods. Achromobacter spp. are commonly known as human pathogens, and cross-kingdom pathogenic bacterium in animal (mice) and fungi (Coprinus comatus) (Ye et al. 2018). However, A. xylosoxidans was recently reported as the causal agent of stem rot of Amorphophallus konjac in China (Wei et al. 2023). To our knowledge, this is the first report of A. xylosoxidans causing bacterial stem and leaf blight of C. arida in Tennessee and the U.S. Identification of this novel disease lays the foundation development of effective management strategies.

The amount of phosphorus (P) conventionally recommended and applied to container nursery crops commonly exceeds plant requirements, resulting in unused P leaching from containers and potentially contributing to surface water impairment. An experiment was replicated in the Middle Atlantic Coastal Plain (MACP) and Ridge and Valley ecoregions of Virginia to compare the effect of a low-P controlled-release fertilizer (CRF, 0.9% or 1.4% P depending on species) vs. a conventional CRF formulation (control, 1.7% P) on plant shoot growth, crop quality, and substrate nutrient concentrations of four species: ‘Natchez’ crape myrtle ( Lagerstroemia indica × Lagerstroemia fauriei ), ‘Roblec’ Encore azalea ( Rhododendron hybrid), ‘Radrazz’ Knock Out rose ( Rosa hybrid), and ‘Green Giant’ arborvitae ( Thuja plicata × Thuja standishii ). In both ecoregions, the low-P CRF resulted in 9% to 26% lower shoot dry weight in all four species compared with those given the conventional formulation, but quality ratings for two economically important species, ‘Radrazz’ Knock Out rose and ‘Green Giant’ arborvitae, were similar between treatments. When fertilized with the low-P CRF, ‘Roblec’ Encore azalea and ‘Natchez’ crape myrtle in both ecoregions, and ‘Green Giant’ arborvitae in the MACP ecoregion had ∼56% to 75% lower substrate pore-water P concentrations than those that received the control CRF. Nitrate-nitrogen (N) concentrations in substrate pore water at week 5 were more than six times greater in control-fertilized plants than in those that received a low-P CRF, which may have been a result of the greater urea-N content or the heterogeneous nature of the low-P CRFs. Lower water-extractable pore-water P and N indicate less environmental risk and potentially increased crop efficiency. Our results suggest low-P CRFs can be used to produce certain economically important ornamental nursery crops successfully without sacrificing quality; however, early adopters will need to evaluate the effect of low-P CRFs on crop quality of specific species before implementing on a large scale.

Phosphorus (P) fertilizers applied to container-grown nursery crops readily leach through pine bark-based substrates and can subsequently runoff and contribute to surface water contamination. The objectives of this research were to determine the effect of adding a layer of FeSO₄·7H₂O-amended pine bark (FSB) to the bottoms of nursery containers on P leaching characteristics. Phosphorus and iron (Fe) leaching in response to FSB layer height (4 or 7.5 cm), FeSO₄·7H₂O rate (0.3, 0.6, or 1.2 kg·m⁻³ Fe), and form (i.e., granular versus liquid) used to formulate the FSB layer, and the inclusion of dolomite in the FSB layer were also investigated. Greenhouse studies lasting 15 and 19 weeks were conducted, in which 2.5 L nursery containers containing the FSB layer treatments below non-amended pine bark substrate were fertilized with 199 or 117 mg P from a soluble or controlled-release fertilizer, respectively. Leachate resulting from daily irrigation was collected and analyzed for P and Fe weekly. All FSB treatments leached less P than the control (non-amended pine bark only), with P reductions ranging from 22% (4 cm FSB with 0.3 kg·m⁻³ Fe) to 73% (7.5 cm FSB with 1.2 kg·m⁻³ Fe). Phosphorus leaching decreased linearly with an increase in Fe rate or layer height. The amount of Fe that leached from containers with FSB was <5% of that applied, regardless of the Fe rate. Granular- and liquid-applied FeSO₄·7H₂O with or without dolomite were equally effective at reducing P leaching. Adding 0.6 kg·m⁻³ Fe to the bottom 500 cm³ of pine bark increased P adsorption by 0.053 mg·cm⁻³ P, which equates to 17.9 mg P adsorbed per gram of FeSO₄·7H₂O added. Results from this research suggest that including an FSB layer in the bottom of nursery containers is an effective strategy for reducing P runoff from container-based nursery production sites.

Container production systems are critical for the horticulture industry but are particularly vulnerable to temperature extremes. This study investigated the effects of pot color (black vs. white) and irrigation frequency (single vs. cyclic) on root zone temperature and the growth of Hydrangea paniculata ‘Limelight’, one of the most popular and widely grown container-grown perennial shrubs in North America. The experiment was conducted at the North Willamette Research and Extension Center in Aurora, Oregon, USA (45°16′51″ N, 122°45′04″ W). A total of 160 Hydrangea paniculata ‘Limelight’ plants were divided into two groups of 80 and potted in black or white 11.4 L nursery containers filled with a bark-based potting mix. Pots were randomly assigned to one of two irrigation treatments based on irrigation frequency: single or cyclic. In the single irrigation treatment, pots received one irrigation event at 07:00 h. In the cyclic irrigation treatment, the same total irrigation volume was divided into three equal applications delivered at 08:00, 12:00, and 16:00 h. Results showed that black pots reached significantly higher root zone temperatures than white pots. Cyclic irrigation effectively reduced the peak root zone temperatures in black pots, cooling by as much as 6 °C during hot afternoons compared with single irrigation. Plants in black pots experienced 6×–7× more hours above critical root-zone temperature thresholds (>38 °C) compared with those in white pots. Although the literature indicates that prolonged exposure above 35–38 °C can inhibit photosynthesis and slow growth, and that root growth may cease at ~38 °C, in our study, plant growth was not significantly affected by pot color, irrigation regime, or their interaction (all p > 0.05). This study emphasizes the importance of optimizing pot color and irrigation practices to address vulnerabilities to extreme temperatures in container production systems.

Incense cedar (Calocedrus decurrens) is a conifer native to the western United States, valued for its low maintenance and aesthetic appeal in ornamental landscapes. In May 2024, field and container grown incense cedar exhibited canker and dieback in a USDA research plot at the Nursery Research Center, McMinnville, TN (Fig. 1a). Disease incidence was 60% of a total 100 plants. For isolation of the causal agent, small pieces (∼0.3 mm²) of the branch and stem cankers were excised, surface sterilized with 1% sodium hypochlorite for 1 minute, followed by 70% ethanol for 30 seconds, and washed twice with sterile water. The pieces were placed on potato dextrose agar (PDA) and incubated at 25°C under 12-hour light/dark conditions. Colonies initially appeared white, and after four to six days, they gradually turned dark gray with dense aerial mycelia (Fig. 1b). Conidia produced within pycnidia after 3 weeks were hyaline, fusiform, and aseptate, with dimensions of 21.1 to 25.8 μm (avg. 24.35 ± 1.049 μm) in length and 5.7 to 8.2 μm (avg. 6.1 ± 0.687 μm) in width (n = 50) (Fig. 1c). Pathogen identity was confirmed by extracting total genomic DNA using the DNeasy PowerLyzer Microbial Kit from 7-day-old pure cultures (isolates FBG7412 and FBG7413). The primer pairs ITS1/ITS4 (White et al. 1990), T1F/Bt2b (Glass and Donaldson 1995; O'Donnell and Cigelnik 1997), and EF1-728F/EF2 (Carbone and Kohn 1999) were used to amplify the ribosomal internal transcribed spacer (ITS), and nuclear beta-tubulin (TUB) and translation elongation factors 1-α (EF1-α) genetic markers, respectively. The sequences of the two isolates (FBG7412 and FBG7413) were deposited in GenBank with accession numbers PQ482605 and PQ482606 (ITS); PQ493369 and PQ493370 (TUB); and PQ493366 and PQ493367 (EF1-α), respectively. GenBank BLAST search of sequences using the core nt database showed 100% identity (100% coverage) of ITS, TUB, and EF1-α sequences to Botryosphaeria dothidea isolates IS2116-1 (OR958722), MEND-F-0379 (OQ994765), and IRNBS19 (MN633962), respectively. Phylogenetic analysis of concatenated ITS, TUB, and EF1-α sequences confirmed the pathogen as B. dothidea (Fig. 2). Two same two fungal isolates FBG7412 and FBG7413 were used to inoculate incense cedar cuttings grown in 3.8L pots with each plant measuring 12-15 cm in height. The inoculum was prepared by growing each isolate on PDA for one week at 25°C. For inoculation, a thin slice of bark (4 mm²) was removed from the stem of each cutting, and a 4-mm-diameter plug colonized by the fungal isolate was placed on the wound which was then covered with Parafilm. Negative controls were mock inoculated with sterile PDA plugs. There were five replications for each isolate and control. The study was conducted in a greenhouse maintained at 23-25°C and 70% relative humidity, with a 16-hour photoperiod. Six weeks post-inoculation, the branches inoculated with B. dothidea exhibited browning and dieback while the controls remained green and healthy (Fig. 1d-f). A dark, necrotic lesion that extended up and down from the inoculation point gradually spread to kill the main stem. Fungal isolate (FBG7703) with the same morphology and DNA sequences as FBG7412 and FBG7413 were recovered from the symptomatic stems of the inoculated plants. Control plants remained symptomless, and B. dothidea was not isolated from them. B. dothidea was previously isolated from incense cedar in California (Ma and Michailides 2002). To our knowledge, this is the first report of B. dothidea causing canker disease in incense cedar in Tennessee. Accurately identifying this pathogen as the causal agent is important for developing effective and timely management strategies.