First Report of Phytopythium litorale Causing Root Rot on Kousa Dogwood in Tennessee and the United States.

Kousa dogwood (Cornus kousa) is an economically important woody ornamental crop that exhibits creamy, white, pointed bracts in late spring, and reddish to pink drupe fruits in late summer and fall. It bears shiny dark green leaves that become reddish-purple to scarlet in the fall. In August of 2023, 3-year-old container grown C. kousa var. chinensis plants in a commercial nursery in Warren Co., Tennessee, exhibited severe yellowing, dieback and root rot symptoms (Fig. 1a and 1b). Dark brown to black lesions were observed in the root and crown region of the plants. Disease severity was 40% to 60% of root area affected, and disease incidence was approximately 40% of 1,000 plants. Surface-sterilized (10% NaOCl: 1 min) symptomatic root tissues were plated on V8-PARPH and incubated at 25°C. Sparse aerial mycelium, showing a distinct rosette or faint radiate to chrysanthemum colony pattern, was observed within four days of incubation (Fig. 2). All isolates produced ovoid or subglose, papillate, and proliferating sporangia in grass blade water cultures (Dervis et al. 2020). Sporangia measured as 19.18 to 24.80 µm X 18.08 to 22.16 µm (n = 50) with a length/width ratio of 1.06 to 1.11. Zoospores observed were between 7.07 to 9.98 µm in diameter (n = 50). Oogonia and oospores were not produced. The ribosomal internal transcribed spacer (ITS) and large subunit (LSU), as well as mitochondrial cytochrome oxidase subunit II (COX-II) genetic markers were amplified and sequenced using primer pairs ITS1/ITS4 (White et al. 1990), NL1/NL4 (Baten et al. 2014), and cox2-F/cox2-RC4 (Choi et al. 2015), respectively. The ITS, LSU, and COX-II sequences of isolates FBG6343, FBG6344 (ITS: PP458373 and PP461387; LSU: PP461390 and PP461391; COXII: PP477112 and PP477113) were 100% identical to those of MN306118, HQ643386, and MN206732, respectively. Based on the morphology (Nechwatal and Mendgen 2006) and sequence data, the isolates were identified as Phytopythium litorale (Nechw.) Abad, De Cock, Bala, Robideau, Lodhi & Lévesque. The pathogenicity test was performed on 3-year-old C. kousa var. chinensis plants grown in a 3-gal container to fulfill Koch's postulates. Kousa dogwood plants were drench inoculated (800 ml/plant) with a pathogen slurry (two plates of 7-day-old culture/liter) of isolates FBG6343 and FBG6364 (five plants per isolate). Control plants were drenched with agar slurry without the pathogen. The study was conducted in a greenhouse maintained at 21 to 23°C and 70% relative humidity with a 16-h photoperiod and irrigated twice a day for 2 min using an overhead irrigation system. Forty-five days after inoculation, plants showed dieback symptoms, and dark brown lesions developed in the roots of all inoculated plants. Isolates with morphology and sequences identical to those of FBG6343 and FBG6364 were recovered from root tissues of all inoculated plants. All control plants remained symptom-free, and P. litorale was not isolated from the root tissue. Previously, P. litorale was reported to cause disease on apple, kiwi, planatus, and rhododendron (Dervis et al. 2020; Li et al. 2021; Mert et al. 2020; Polat et al. 2023). To our knowledge, this is the first report of P. litorale causing root rot of kousa dogwood in Tennessee and the United States. Identification of this pathogen as the causal agent is crucial to developing timely management practices.

Identification and Chemical and Biological Management of Fusarium Root and Crown Rot Disease of Oakleaf Hydrangea.

Oakleaf hydrangea (Hydrangea quercifolia) is an important ornamental plant grown in Tennessee. In May 2018, after late spring frost, cultivars Pee Wee and Queen of Hearts showed root and crown rot symptoms and identification and management of the disease was a major concern. The objective of this research was to identify the causal organism of this disease and develop management recommendations for nursery growers. Isolates from the infected root and crown parts were subjected to microscopy, and the morphology of fungi resembled Fusarium. Molecular analysis was conducted by amplifying the internal transcribed spacer of ribosomal DNA, ß-tubulin, and translation elongation factor 1-α regions. Fusarium oxysporum was identified as a causal organism based on molecular analysis. A pathogenicity test was done to complete the Koch's postulates by drenching containerized oakleaf hydrangea with a conidial suspension. Experiments were conducted to evaluate different chemical fungicides and biological products with different rates for Fusarium root and crown rot management in container-grown Queen of Hearts. Plants were inoculated by drenching containerized oakleaf hydrangea with 150-ml conidial suspensions of F. oxysporum, maintaining the concentration of 1 × 106 conidia/ml. Root and crown rot were assessed using a scale of 0 to 100%. Recovery of F. oxysporum was recorded by plating root and crown sections. Chemical fungicides such as mefentrifluconazole (BAS75002F), the low rate (1.09 ml/liter) of difenoconazole + pydiflumetofen (Postiva), and the high rate (1.32 ml/liter) of isofetamid (Astun) and biopesticide were applied; the high rate (1.64 g/liter) of ningnanmycin (SP2700 WP) effectively reduced Fusarium root rot severity and pyraclostrobin effectively reduced Fusarium crown rot severity in both trials.

First Report of Root Rot of Redbud Caused by Phytopythium vexans in Tennessee and the United States.

The eastern redbud (Cercis canadensis L.) is an esthetically and economically important landscape tree with vibrant blossoms and attractive heart-shaped leaves. One-year-old eastern redbud seedlings grown in field condition in two commercial nurseries in Warren Co., Tennessee exhibited severe root rot in October 2021. Dark brown to black lesions and rot were observed in the affected roots (Fig. 1a). Disease severity was 50-75% of root area and disease incidence was approximately 30-40% of 10,000 plants. Surface sterilized (10% NaOCl; 1 min) symptomatic tissues were plated on V8-PARPH and incubated at 25°C. Whitish cottony mycelia with radiate and chrysanthemum flower-like growth patterns were observed within 4 days of incubation. Subglobose papillate sporangia (10.24 to 20.98 µm, n=50), filamentous to globose smooth oogonia, bell-shaped antheridia and spherical zoospores that are characteristic of Phytopythium vexans (de Cock et al. 2015) were observed in older cultures that were subjected to specific growth conditions as previously described by Ghimire & Baysal-Gurel (2023). Pathogen identification was confirmed by extracting total DNA using the DNeasy PowerLyzer Microbial Kit from 7-day-old cultures of isolates FBG0874, FBG1998, FBG2009 grown on V8-PARPH. P. vexans specific LAMP assay was conducted for the rapid molecular screening and confirmation of the isolates (Ghimire et al. 2023). Primer pairs ITS1/ITS4 (White et al. 1990), NL1/NL4 (Baten et al. 2014), Levup and Fm85mod (Robideau et al. 2011) were used to amplify and sequence the internal transcribed spacer (ITS), 28S large subunit (LSU) of ribosomal RNA and the cytochrome c oxidase subunit I (CoxI) of mitochondrial DNA genetic markers, respectively. The sequences (GenBank accession nos. OR204701, OR205212, OR205213: ITS; OR205214, OR205215, OR205216: LSU; OR220805, OR220806, OR220807: CoxI) were 100% similar to ITS, LSU, and CoxI genetic markers of P. vexans isolates in the NCBI database (MK011121: ITS, KX092469: LSU and KT692908: CoxI). Pathogenicity tests were performed on one-year-old eastern redbud seedlings grown in 1 gal containers to fulfill Koch's postulate. Eastern redbud seedlings were drench inoculated (150 ml/plant) with pathogen slurry (two plates of 7-day-old culture/liter) (Panth et al. 2021) of isolates FBG0874, FBG1998, and FBG2009 (five plants/isolate). Control plants were drenched with agar slurry without pathogen. The study was conducted in a greenhouse maintained at 21 to 23°C, 70%RH, with 16-h photoperiod and irrigated twice a day for 2 min using an overhead irrigation system. Fourteen days after inoculation dark brown to black lesions developed in the root of all inoculated plants that were identical to the symptoms observed in the original samples (Fig. 1b), while the roots of non-inoculated plants remained asymptomatic (Fig. 1c). Isolates resembling P. vexans morphological characteristics were recovered from inoculated plants, and their identity was confirmed as P. vexans using LAMP assay. P. vexans has been previously reported to cause root and crown rot in flowering cherry, ginkgo, and red maple in Tennessee (Baysal-Gurel et al. 2021, Panth et al. 2021). To our knowledge, this is the first report of P. vexans causing root rot of eastern redbud in Tennessee and the United States. Identification of this pathogen as the causal agent is important in designing and implementing effective management practices to mitigate this threat to redbud production.

Identification and Management of Phytophthora Aerial Blight Caused by Phytophthora nicotianae on Catharanthus roseus.

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.

Identification and Chemical and Biological Management of Phytopythium vexans, the Causal Agent of Phytopythium Root and Crown Rot of Woody Ornamentals.

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 showed 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 Tennessee nurseries and to 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. To confirm identity, total genomic DNA was extracted, followed by sequence analysis of the internal transcribed spacer regions, large subunit of nuclear rRNA, and cytochrome c oxidase subunits I and II of mitochondrial DNA. Based on morphological and molecular analysis, Phytopythium vexans was described as a causal agent of crown and root rot from the infected ginkgo and red maple plants. To complete Koch's postulates, a pathogenicity test was performed by drenching 100 ml of V8 agar medium slurry of Phytopythium vexans inoculum on 1-year-old potted ginkgo plant root systems as well as red maple October Glory. Necrotic lesion development was observed in the root system 45 days after inoculation and Phytopythium vexans was reisolated from the roots of both ginkgo and red maple. All control ginkgo and red maple plants remained disease free and no pathogen was reisolated. In addition, the efficacy of fungicides, biofungicides, fertilizer, and host plant defense inducers (traditionally recommended for management of oomycete diseases) for control of Phytopythium crown and root rot was evaluated on ginkgo and red maple October Glory seedlings in greenhouse and field trials. Fungicides such as Empress Intrinsic, Pageant Intrinsic, Segovis, and Subdue MAXX were effective in both greenhouse and field trials, and the biofungicide Stargus reduced disease severity caused by pathogen Phytopythium vexans on ginkgo and red maple plants in greenhouse trials. These results will help nursery producers make proper management decisions for newly reported Phytopythium crown and root rot disease of ginkgo and red maple plants.

Occurrence of Volutella Blight Caused by Pseudonectria foliicola on Boxwood in Tennessee.

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), ß-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 × 105 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.

First Report of Phytopythium vexans Causing Root and Crown Rot on Flowering Cherry in Tennessee.

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.

First Report of Powdery Mildew on Physocarpus opulifolius Caused by Podosphaera physocarpi in Tennessee.

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.

Evaluation of Chemical and Biological Products for Control of Crown Gall on Rose.

Crown gall is a soil-borne bacterial disease caused by Agrobacterium tumefaciens, leading to significant economic losses in many plant species. For the assessment of the biological and chemical products on crown gall, each plant's crown region and roots were wounded, and then were dipped into their respective treatments. After the treatments, the plants were inoculated with a suspension of pathogenic A. tumefaciens isolate FBG1034 and maintained in a greenhouse for six months to assess them for gall formation. A quantitative real-time PCR assay was performed to quantify the A. tumefaciens using the chvE gene. Biological products such as the Agrobacterium radiobacter strain K1026, and strains 1 and 2, resulted in the lowest average root gall diameter and significantly reduced the crown gall diameter to stem diameter ratio, and the chemical product copper octanoate reduced the number of crown and root galls as well as the crown and root gall diameter compared to the inoculated, non-treated control. Moreover, both the A. radiobacter strain K1026 and strain 1 treatments resulted in an approximately 85% and 65% reduction in crown and root gall incidence, respectively, in both of the trials compared to the inoculated, non-treated plants. The findings of this study indicate that the use of biological and chemical products could help to suppress crown and root gall disease in rose plants.

Fire Ant Venom Alkaloids: Possible Control Measure for Soilborne and Foliar Plant Pathogens.

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, root rot severity, and pathogen recovery in soilborne pathogen inoculated plants. Similarly, venom alkaloid reduced Botrytis blight. However, higher venom rates caused foliar phytotoxicity on plants. Therefore, additional work is needed to evaluate rates of venom alkaloids or formulations to eliminate negative impacts on plants. Overall, these results suggest that red imported fire ant venom alkaloids may provide a basis for new products to control soilborne and foliar plant pathogens.