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Invasive plants, which cause substantial economic and ecological impacts, acquire both pathogens and beneficial microbes in their introduced ranges. Communities of fungal endophytes are known to mediate impacts of pathogens on plant fitness but few studies have examined the temporal dynamics of fungal communities on invasive plants. The annual grass Microstegium vimineum, an invader of forests and riparian areas throughout the eastern United States, experiences annual epidemics of disease caused by Bipolaris pathogens. Our objective was to characterize the dynamics of foliar fungal communities on M. vimineum over a growing season during a foliar disease epidemic. First, we asked how the fungal community in the phyllosphere changed over 2 months that corresponded with increasing disease severity. Second, we experimentally suppressed disease with fungicide in half of the plots and asked how the treatment affected fungal community diversity and composition. We found increasingly diverse foliar fungal communities and substantial changes in community composition between timepoints using high-throughput amplicon sequencing of the internal transcribed spacer 2 region. Monthly fungicide application caused shifts in fungal community composition relative to control samples. Fungicide application increased diversity at the late-season timepoint, suggesting that it suppressed dominant fungicide sensitive taxa and allowed other fungal taxa to flourish. These results raise new questions regarding the roles of putative endophytes found in the phyllosphere given the limited number of pathogens known to cause disease on M. vimineum in its invasive range.

Watermelon is an important crop in Florida, representing $88.2 million in cash receipts in 2015 (USDA/NASS 2017). In April and May 2021, the UF/IFAS Plant Diagnostic Center in Gainesville, Florida received eight diseased watermelon leaf samples from Alachua, Gilcrest, Levy, and Suwannee counties in Florida. Lesions were round to oblong, light gray to tan with reddish brown margins and white to light gray center, and some were coalescing resulting in about 15% disease severity. Symptomatic leaf tissue (0.5 cm2) was surface sterilized in 0.6% sodium hypochlorite for one minute, rinsed with sterile tap water, plated onto water agar media plates, and incubated at 27°C under 12-h light/dark cycle for 7 days. Characteristic Bipolaris conidia with gray to black brownish cottony mycelial growth were consistently found growing from plated lesions. The pathogen was isolated from two of the eight samples using a 0.5 mm diameter sterile metal needle to transfer a single conidium onto DifcoTM Potato Dextrose Agar (PDA) plates. Three isolates were designated G21-562 from Levy and G21-599a and G21-599b from Alachua County. All three isolates produced curved or straight, cylindrical, obclavate, distoseptate brownish gray conidia with 3 to 8 septa, mostly tapering towards ends with dark brownish to black hilum, that ranged from averaged 62um x 25um (n=30, SD=8 for length and 3 for width). Conidiophores were brownish, septate, smooth, and straight, single or in small groups, simple or branched, and swollen at the upper tip. Internal transcribed spacer region (ITS) and partial glyceraldehyde-3-phosphate dehydrogenase (GPDH) gene sequences were amplified using primers ITS1/ITS4 and GPD-1/GPD-2 (Berbee et al. 1999). Reference sequences (Adhikari et al. 2020 and Manamgoda et al. 2014) were aligned using MUSCLE and trimmed to consistent length. Using concatenated sequence alignments of both loci, a maximum likelihood phylogenetic tree was constructed based on K2+G substitution model selected by BIC using Mega X (Kumar et al. 2018) with 1,000 bootstrap. The ITS and GPDG sequences of G21_599b, G21_599a and G21_562 (GenBank accessions OK614094 to 96, OP297398 to 400) showed 100% identity across 888 nucleotides across both loci to B. sorokiniana isolates CBS_110.14 and CBS_ 120.24 and were distinct from other reference isolates. To fulfill Koch’s postulates, all three isolates were grown on PDA at 27°C and 12-h light/dark cycle. After a week, conidia were harvested in sterile water, and the conidial suspensions were adjusted to 105 conidia/ml using a hemocytometer. Each conidial suspension and Tween 20 water control was sprayed onto three seedlings of ‘Sugar Baby’ watermelon until runoff, and inoculated seedlings were sealed in a plastic bag for 24 hrs. The experiment was done in a greenhouse (20- 25°C) and repeated once. After a week of incubation, the same leaf lesion symptoms described above were observed on seedlings inoculated with conidia, whereas seedlings sprayed with the control were asymptomatic. Isolations from symptomatic tissue produced gray to black mycelia with conidia that were the same as described from field samples. To our knowledge, this is the first report of leaf spot on watermelon caused by B. sorokiniana. B. sorokiniana is a common pathogen of grasses and agronomic crops (Farr and Rossman 2020). The extent to which this emerging disease of Florida watermelon may negatively impact production is unknown and should be the subject of future observation and research.

The weather conditions favoring Blueberry anthracnose fruit rot disease incidence and development can be difficult to predict, and it can significantly impact yield under conducive weather patterns. For that reason, the authors of this new 6-page publication of the UF/IFAS Plant Pathology Department developed and validated a web-based disease alert system for blueberry AFR, the Blueberry Advisory System (BAS), to help blueberry growers in Florida identify weather conditions favorable for the disease and improve disease management. Written by André B. Gama, Douglas A. Phillips, Vinícius A. Cerbaro, Phillip F. Harmon, Clyde W. Fraisse, and Natalia A. Peres.https://edis.ifas.ufl.edu/pp366

Environmentally damaging invasive plants can also serve as reservoir hosts for agricultural pathogens. Microstegium vimineum is an invasive C4 annual grass that is present throughout the midwestern and eastern United States. It can reach high densities in disturbed areas such as crop-forest interfaces, which creates the potential for pathogen spillover from M. vimineum to agricultural crops and native plants. A previous study that surveyed disease on M. vimineum found a large-spored Bipolaris species that was widespread on M. vimineum and also isolated from co-occurring native grasses. Here, we report that the large-spored fungus isolated from M. vimineum and the native grass Elymus virginicus is Drechslera gigantea, based on comparison with published descriptions of morphological traits, and establish that D. gigantea is a pathogen of M. vimineum and E. virginicus. We review the phylogenetic placement and taxonomic history of D. gigantea and propose that it be reassigned to the genus Bipolaris as Bipolaris gigantea.

Vaccinium arboreum Marsh is a small tree adapted to low-organic matter soils and is one of the few ericaceous species that tolerates soil pH greater than 6.0. It has a deep root system and is more drought tolerant than cultivated blueberry. The use of V. arboreum as a rootstock for commercial blueberry production has been studied previously in young blueberry plantings. The objective of the current study was to expand on earlier work and evaluate growth, productivity, and tolerance to bacterial leaf scorch (Xylella fastidiosa) in established plantings of own-rooted vs. grafted southern highbush blueberry (SHB). Two field plantings of grafted and own-rooted ‘Meadowlark’ and ‘Farthing’ SHB were established in May 2011: one at the University of Florida–Institute of Food and Agricultural Sciences (UF-IFAS) Plant Science Research and Education Unit in Citra, FL, and the other at a commercial blueberry farm in Archer, FL. At both sites, four rootstock–scion combinations were grown in either pine bark-amended or nonamended soil. Canopy volume was greater in grafted compared with own-rooted ‘Meadowlark’ at both locations throughout the 4 years of the study (2015–18), whereas canopy volume in ‘Farthing’ was not consistently different. For both cultivars and both locations, canopy volume was greater on amended compared with nonamended soil. Although canopy growth was not consistently increased in the grafted compared with own-rooted plants, yield was greater in grafted plants of both cultivars at both locations. Cumulative yield over the 4 years was similar between grafted plants grown on both amended and nonamended soil, and was significantly greater than yield of own-rooted plants on nonamended soil, suggesting the use of this rootstock may decrease the requirement for pine bark amendment. In general, grafted plants produced larger berries, with no negative impacts on fruit soluble solids, titratable acidity, or firmness. ‘Meadowlark’—an SHB cultivar that exhibits high sensitivity to bacterial leaf scorch—displayed decreased development of bacterial leaf scorch symptoms when grafted onto V. arboreum compared with own-rooted plants. These results indicate the potential benefits of grafting SHB onto V. arboreum rootstock, particularly under marginal soil conditions. However, a complete economic analysis that also takes into account any differences in longevity between the two systems must be done to determine whether the benefits of using grafting are feasible financially for the grower.

Invasive species impact ecosystems through their large abundances and strong per capita effects. Enemies can regulate abundances and per capita effects, but are notably absent for many new invaders. However, invaders acquire enemies over time and as they spread; processes hypothesized to mitigate negative invader impacts by reducing abundance or per capita effects. Alternatively, properties of invaders or acquired enemies, such as an enemy’s ability to attack multiple species, may hinder enemy mitigation of invader impacts. We used field experiments to evaluate disease mitigation of invader impacts using the invasive grass Microstegium vimineum, which hosts an emerging fungal disease, and a native grass competitor, Elymus virginicus. We manipulated competition through density gradients of each plant species, and we reduced ambient foliar diseases with fungicide and autoclaving. We then modeled long-term population dynamics with field-estimated parameters. In the field, disease did not reduce invader abundance or per capita effects. The invader amplified disease on itself and the competitor, and disease reduced invader and competitor fitness components (e.g., germination). The dynamical model predicted that disease impacts on the competitor are greater than on the invader, such that disease will reduce invader abundance by 18%, and competitor abundance by 88%, over time. Our study suggests that enemies acquired by invaders will not necessarily mitigate invader impacts if the invader amplifies the enemy and the enemy attacks and suppresses competitor species.

Plant litter can alter ecosystems and promote plant invasions by altering resource availability, depositing phytotoxins, and transmitting microorganisms to living plants. Transmission of microorganisms from invasive plant litter to live plants may gain importance as invasive plants, which often escape pathogens upon introduction to a new range, acquire new pathogens over time. It is unclear, however, if invasive plant litter affects native plant communities by promoting disease. Microstegium vimineum is an invasive grass that suppresses native populations, in part through litter production, and has acquired new fungal leaf spot diseases since its introduction to the United States. In a greenhouse experiment, we evaluated how M. vimineum litter and its pathogens mediated competition with the native grass Elymus virginicus. M. vimineum litter promoted disease on E. virginicus and suppressed establishment and biomass of both species. Litter had stronger negative effects on E. virginicus than M. vimineum, increasing the relative biomass of M. vimineum. Live plant competition reduced biomass of both species and live M. vimineum increased disease incidence on E. virginicus. Altogether, invasive grass litter suppressed both species, ultimately favoring the invasive species in competition, and increased disease incidence on the native species.

Bark inclusions are an understudied structural defect in trees and shrubs. They consist of areas of bark on adjacent parts of stems or scaffolds, typically on the inner faces of a narrow fork, which become overgrown and internalized to occupy part of the wood between the stems. Here, bark inclusions are described for the first time to occur in cane unions at the crown of southern highbush blueberry (Vaccinium corymbosum interspecific hybrids) cultivars ‘Farthing’ and ‘Meadowlark’, both of which are characterized by a narrow, vase-shaped architecture at the base of the plant, leading to crowding of the canes. When affected canes were dissected at their bases, bark inclusions were visible internally as a line of compressed bark within the wood of adjoining canes, or as bark invaginations and fissures across part of or the entire cross-section of the cane. Externally, blueberry crowns with included bark were characterized by either an inward ridgeline of bark between canes of similar diameters emerging from the crown at a narrow angle from each other, or by the presence of girdling roots. Bark inclusions were observed in plants of all ages, from the nursery to mature production fields. The internal length of the bark inclusion correlated strongly with the external length of the inward stem bark ridgeline symptom as measured by destructive sampling in the field (r = 0.916, p < 0.0001, n = 20). When plants with and without bark inclusions were subjected to a winch test in the field, the probability of breakage for canes without included bark was significantly lower (p < 0.0002) than for those with included bark, and at the maximum applied force of 972.4 N, 95.2% of the canes with bark inclusions failed (i.e., broke at the crown), compared with only 52.6% for canes without included bark. In a survey across three fields, the number of bark inclusions per plant was significantly associated with an index of cane crowding (r = 0.286. p = 0.0267, n = 60), suggesting that plants with tight, crowded bases had more bark inclusions. In addition, there was a significant association (p < 0.0001) between the presence or length of bark inclusions and the intensity of Botryosphaeria stem blight in these fields. This study showed that bark inclusions occur commonly in certain southern highbush blueberry cultivars in the production conditions of Georgia and Florida, with negative implications for cane integrity and plant health.

Stem blight is a major disease of blueberry caused by Botryosphaeriaceae fungi. Chemical and cultural management options are limited, putting emphasis on breeding efforts to identify sources of resistance. The efficacy and durability of host resistance could be impacted by the species composition of the pathogen population in a region and by the isolates employed in the screenings used to identify the resistance. Samples (365) were collected from southern highbush (SHB) and rabbiteye blueberry (REB) cultivars from 28 sites in the southeastern US (AL, FL, GA, NC, and SC). Colony morphology identified 86% of the isolates as Botryosphaeriaceae. Conidia morphology and Maximum Likelihood analysis of the Internal Transcribed Spacer rDNA regions (ITS), translation elongation factor one alpha (tef1-α), and β-tubulin were used to identify isolates at genera or species level. A PCR-restriction fragment length polymorphism (PCR-RFLP) test was used to identify isolates to genus. Neofusicoccum and Lasiodiplodia were the predominant genera. N. kwambonambiense, N. ribis, L. theobromae and L. pseudotheobromae were the most common species isolated. Phylogenies conducted with a limited number of isolates indicated non-clonal and potentially diverse populations occur on blueberry that warrant additional study. Botryosphaeria corticis, B. dothidea, and Diplodia seriata were isolated infrequently.

There is a growing market in the United States and globally for fresh fruits and vegetables with reported health-enhancing properties. This includes blueberries, which are high in antioxidants and have been reported to improve heart health and contain anticancer properties. Fresh-market blueberry sales (conventional and organic) increased by 27% between 2013 and 2017, and that trend is expected to continue. In addition, there is an increasing level of consumer interest in organically grown produce (for environmental conservation, taste, and other perceived benefits), for which some consumers are willing to pay a premium over the price for a conventionally produced crop. This new 8-page publication of the UF/IFAS Horticultural Sciences Department discusses various aspects of organic blueberry production in Florida and is intended for use by those currently using or interested in pursuing organic production. Written by Douglas A. Phillips, Peter J. Dittmar, Philip F. Harmon, Oscar E. Liburd, Danielle D. Treadwell, and Jeffrey G. Williamson.https://edis.ifas.ufl.edu/hs1400

Plant-pathogen interactions occur throughout the process of plant invasion: pathogens can acutely influence plant survival and reproduction, while the large densities and spatial distributions of invasive plant species can influence pathogen communities. However, interactions between invasive plants and pathogens are often overlooked during the early stages of invasion. As with introductions of invasive plants, the introduction of agricultural crops to new areas can also generate novel host-pathogen interactions. The close monitoring of agricultural plants and resulting insights can inform hypotheses for invasive plants where research on pathogen interactions is lacking. This chapter reviews the known and hypothesized effects of pathogens on the invasion process and the effects of plant invasion on pathogens and infectious disease dynamics throughout the process of invasion. Initially, pathogens may inhibit the transport of potentially invasive plants. After arrival in a new range, pathogens can facilitate or inhibit establishment success of introduced plants depending on their relative impacts on the introduced plants and resident species. As invasive plants spread, they may encounter novel pathogens and alter the abundance and geographic range of pathogens. Pathogens can mediate interactions between invasive plants and resident species and may influence the long-term impacts of invasive plants on ecosystems. As invasive plants shift the composition of pathogen communities, resident species could be subject to higher disease risk. We highlight gaps in invasion biology research by providing examples from the agricultural literature and propose topics that have received little attention from either field.

Infectious diseases and invasive species are strong drivers of biological systems that may interact to shift plant community composition. Disease and invasion can each directly suppress native populations, but variation in responses among native species to disease, invasion, and their combined effects are not well characterized. Here, we quantified the responses of three native North American grass species to experimental inoculation with the fungal pathogen Bipolaris gigantea, which has recently emerged in populations of the invasive grass Microstegium vimineum, causing leaf spot disease. In a greenhouse experiment, we examined the direct effects of disease on the native species and the indirect effects of disease on the native species through altered competition with M. vimineum, which was planted at a range of densities. Pathogen inoculation directly affected each of the three native species in unique ways, by increasing, decreasing, or not changing their biomass relative to mock inoculation. Higher M. vimineum densities, however, reduced the biomass of all three native species, regardless of inoculation treatment, suggesting that disease had no indirect effects through altered competition. In addition, competition with M. vimineum suppressed native plant biomass to a greater extent than disease. The differential impacts of B. gigantea and the consistent impacts of M. vimineum on native species biomass suggest that disease may modify native plant community composition while plant invasion may suppress multiple native plant species in systems where these drivers co-occur.

Environmentally damaging invasive plants can also serve as reservoir hosts for agricultural pathogens.

Non-native invasive plants can establish in natural areas, where they can be ecologically damaging and costly to manage. Like cultivated plants, invasive plants can experience a relatively disease-free period upon introduction and accumulate pathogens over time. Diseases of invasive plant populations are infrequently studied compared to diseases of agriculture, forestry, and even native plant populations. We evaluated similarities and differences in the processes that are likely to affect pathogen accumulation and disease in invasive plants compared to cultivated plants, which are the dominant focus of the field of plant pathology. Invasive plants experience more genetic, biotic, and abiotic variation across space and over time than cultivated plants, which is expected to stabilize the ecological and evolutionary dynamics of interactions with pathogens and possibly weaken the efficacy of infectious disease in their control. Although disease is expected to be context dependent, the widespread distribution of invasive plants makes them important pathogen reservoirs. Research on invasive plant diseases can both protect crops and help manage invasive plant populations.

Brown rot, caused by Monilinia spp., is one of the most economically harmful fungal diseases for peach and other stone fruit growers worldwide. Under the right conditions, the entire tree’s crop can be completely rotted. Fruit susceptibility fluctuates with the various stages of development; mature fruits are highly susceptible to disease, and fruit infection has the greatest impact on production. This new 7-page publication of the UF/IFAS Horticultural Sciences Department describes the disease cycle, symptoms, and management options available for brown rot in Florida peaches. Written by Ali Sarkhosh, Shirin Shahkoomahally, Logan Marie Richmond-Cosie, and Philip Harmon. https://edis.ifas.ufl.edu/hs1357

‘Flicker’ is a southern highbush blueberry (SHB, Vaccinium corymbosum) cultivar frequently selected by growers in Central and South Florida. In 2014, several growers in Central Florida experienced issues with anthracnose stem lesions and twig dieback on ‘Flicker’, resulting in a reduction in new plantings and the removal of many existing plantings. The objective of this study was to determine the level of anthracnose susceptibility of certain commercially available SHB cultivars, which information can be used to limit further use of susceptible cultivars in the University of Florida blueberry breeding program. The screening was performed using a spray inoculation of a virulent Colletotrichum gloeosporioides isolate onto whole V. corymbosum plants, followed by measurement of incidence and severity of disease over time. In repeated experiments, ‘Flicker’ and two other cultivars had a significantly higher mean number of lesions and area under the disease progress curve (AUDPC) than any other tested cultivar, and in both experiments, the observed lesions were similar in many respects to those previously reported on northern highbush blueberry (also V. corymbosum). Although the results of these experiments may ultimately indicate that Flicker has a unique genetic susceptibility to this form of anthracnose among SHB cultivars commercially grown in Florida, screening of additional cultivars must be performed for confirmation.

International trade in live plant materials has increased worldwide over the last four decades. This has led to a dramatic increase in the introduction, establishment and spread of non-native plant pathogens. Regulatory authorities need advice on measures that may mitigate these adverse consequences of trade. Risk models may be used to underpin such advice. In this review, we give a systematic overview of the data needed for a quantitative risk model for Phomopsis vaccinii, which causes stem and fruit infections on Vaccinium species, and sometimes death, potentially also on native wild Vaccinium species in the EU. P. vaccinii is a quarantine organism worldwide, except for North America, where it is endemic. Despite extensive knowledge of the aetiology of the diseases caused by this pathogen and its taxonomy, quantitative data on transportation and detection of infected plants for planting and berries are scarce, and quantitative assessment of the future introduction, establishment and spread of P. vaccinii is difficult. Estimation of the potential impact of this pathogen in production fields and wild Vaccinium stands is even more difficult. P. vaccinii is not unique in this respect, and this review indicates the need for more and better quantitative data for assessment of the risks posed by newly introduced plant pathogens in areas where they are not endemic.

Southern highbush blueberry (SHB) cultivars are commercially grown throughout much of Florida, in both deciduous and evergreen production systems. In both systems, leaves can be damaged by many factors including environmental conditions, chemical applications, insects, and diseases. This new 12-page publication of the UF/IFAS Plant Pathology Department includes basic information to assist growers in determining 1) the likely cause (fungal, viral, algal, or bacterial) of leaf symptoms, 2) when specific leaf spots are likely to occur, 3) characteristic symptoms of common leaf problems, and 4) some of the management options that are available. Written by Douglas A. Phillips, Norma C. Flor, and Philip F. Harmon. http://edis.ifas.ufl.edu/pp348

Botryosphaeria stem blight is the most common and damaging fungal vascular disease on southern highbush blueberry in the southern United States, causing stem and cane dieback and reductions in yield. Advanced stages of this disease may cause premature plant death, which results in significant replanting costs for growers. Biotic or abiotic stresses from a variety of sources can make plants more susceptible to infection by stem blight pathogens. This new 5-page publication is intended for Florida blueberry growers to use as a guide in the identification and management of Botryosphaeria stem blight on southern highbush blueberry. Written by Norma C. Flor, Douglas A. Phillips, and Philip F. Harmon and published by the UF/IFAS Plant Pathology Department. http://edis.ifas.ufl.edu/pp347

Winter survival of Magnaporthe oryzae in north central Indiana was investigated in response to reports and observations of sporadic disease incidence. Survival of the fungus in perennial ryegrass residue was assessed. Time course studies were designed to assess the conidia production potential of infested perennial ryegrass residue exposed to ambient and predetermined treatments. Approximately 50,000 conidia per gram dry weight were produced initially on infested residue. In all years of the study, ambient winter conditions in Lafayette, IN, reduced conidia production on residue to fewer than 60 conidia per gram by spring. Unless residue was dried prior to treatment, storage of residue at all temperatures tested reduced conidia production potential. Airborne M. oryzae conidia, over the plot of perennial ryegrass where the winter survival studies were conducted, were estimated from particles collected with a volumetric air sampler. The stand of perennial ryegrass was inoculated with residue infested with M. oryzae in the summer of 2000 and late fall of 2000 and 2001. The stand of ryegrass was not inoculated in the summers of 200l or 2002. Conidia were captured with the air sampler each year in early July, before outbreaks had been observed in north central Indiana, but capture peaked in September when outbreaks most often occur. Cumulative conidia capture followed disease severity in 2000; however, no disease was observed in 2001 or 2002. Results of this study suggest poor survival of M. oryzae, and inadequate populations of viable pathogen limit disease development in north central Indiana. Disease risk assessment in north central Indiana should include an estimate of viable inoculum.

Soybean rust caused by Phakopsora pachyrhizi H. Sydow & Sydow was first reported in the continental United States during 2004 (2). By 10 November 2005, the disease was confirmed in eight southern states (Florida, Georgia, Alabama, Mississippi, South Carolina, North Carolina, Louisiana, and Texas). Diagnoses have been based on visual observation of uredinia and urediniospores of the pathogen followed by polymerase chain reaction confirmation. On 10 November 2005, uredinia and telia were identified on leaves of kudzu (Pueraria lobata) in central Florida. Telia first were noted as dark brown-to-black flecks on the abaxial leaf surface intermingled with abundant tan-to-light brown uredinia. Of 200 leaves examined, 143 (72%) had telia. The number of telia ranged from a few (1/cm2) that were scattered to many (73/cm2). Telia were approximately the same diameter as uredinia, but were appressed to the leaf surface and pigmented. Twenty telia were excised from host tissue with the aid of a dissecting microscope and a 20 gauge hypodermic needle. Telia averaged 89 × 100 μm (n = 20, σ = 17 and 16 μm, respectively). Four telia were crushed and five teliospores from each averaged 4.3 × 8.3 μm (n = 20, σ = 0.5 and 0.9 μm, respectively). Pale yellowish brown-to-hyaline teliospores were similar in color to urediniospores. Observations matched descriptions by Ono et al. (1). To our knowledge, this is the first report of the telial stage of P. pachyrhizi in the United States. References: (1) Y. Ono et al. Mycol. Res. 96:825, 1992. (2) R. W. Schneider et al. Plant Dis. 89:774, 2005.

Phakopsora pachyrhizi Syd. & P. Syd., the cause of soybean rust, was first observed in the continental United States in November 2004 (2). During the growing season of 2005, P. pachyrhizi was confirmed on soybean (Glycine max) and/or kudzu (Pueraria montana) in nine states in the southern United States. It is known that P. pachyrhizi has a much larger host range within the Fabaceae family. On 29 September 2005 in Quincy, FL, 45 entries of mostly large-seeded legumes were planted next to soybeans that were infected with P. pachyrhizi. Several seeds of each entry were planted on one hill. Soybean plants growing adjacent to these potential hosts had 15 to 25% of the leaf area affected, 95% incidence, and 73% defoliation on 16 November. On 7 December 2005, all the plants of Phaseolus coccineus L. (scarlet runner bean, PI311827), Phaseolus lunatus L. (lima bean, PI583558), and two Phaseolus vulgaris L. (kidney bean) cvs. Red Hawk and California Early Light Red Kidney (CELRK) were found to have leaves with suspected rust lesions. These plants were at physiological maturity but had not senesced. None of the hosts had been inoculated other than from spores produced by the adjacent rust-infected soybean plants or from unknown locations. On the basis of microscopic examination, suspected infected leaves from plants of the Phaseolus spp. had rust pustules characteristic of P. pachyrhizi uredinia. Uredinia were counted within a randomly selected 2-cm2 area of one leaf of each sample. The mean and range of uredinia per lesion for Phaseolus coccineus was 29 uredinia with a range of 0 to 3 uredinia per lesion, Phaseolus lunatus had 2 uredinia with 0 to 1 uredinium per lesion, Phaseolus vulgaris cv. Red Hawk had 22 uredinia with 0 to 5 uredinia per lesion, and Phaseolus vulgaris cv. CELRK had 43 uredinia with 0 to 4 uredinia per lesion. Polymerase chain reactions using two sets of primers (Ppa1/Ppa2 and Pme1/Pme2) were performed on DNA extracted from leaves of the three species with sporulating rust pustules (1). The results of these tests and further tests conducted by the USDA/APHIS confirmed that P. pachyrhizi was the causal organism for the observed rust. References: (1) P. F. Harmon et al. On-line publication. doi:10.1094/PHP-2005-0613-01-RS. Plant Health Progress, 2005. (2) R. W. Schneider et al. Plant Dis. 89:774, 2005.

Soybean rust (SBR), caused by the obligate fungus Phakopsora pachyrhizi Syd. & P. Syd., was initially reported on soybean (Glycine max L.) in Louisiana in 2004 and has since been reported on soybean and/or kudzu (Pueraria lobata (Willd.) Ohwi) in 9 states in 2005, 15 states in 2006, and 19 states in 2007 (1). The host range of P. pachyrhizi includes plants that are all in the Fabaceae or legume family. Six plant species in the United States have been reported as hosts of P. pachyrhizi: soybean, kudzu, Florida beggarweed (Desmodium tortuosum (Sw) DC.), dry bean (Phaseolus vulgaris L.), lima bean (P. lunatus L.), and scarlet runner bean (P. coccineus L.) (4). On 17 April 2008, a rust disease was observed on a weedy legume host with red showy flowers that was growing with kudzu in an overgrown vacant lot in the understory of live oak trees (Quercus virginiana Mill.) in Citra, FL. The discovery was made during routine scouting of this Integrated Pest Management Pest Information Platform for Extension and Education (IPM PIPE) mobile sentinel plot (3). The plant was confirmed by University of Florida botanists to be Erythrina herbaceae L., commonly known as coral bean. Coral bean is native to the southeastern United States and also is planted as a perennial ornamental. A sample of leaves exhibiting rust pustules characteristic of P. pachyrhizi uredinia was collected and examined with a microscope. Brown-to-brick red, angular lesions that were 3 to 11 mm in diameter (average 6.75 mm) were observed on the undersides of the leaves of two trifoliates. Within these lesions, there were several uredinia, some exuding hyaline, echinulate urediniospores (20 × 25 μm). The visual diagnosis and the species of the rust fungus were confirmed to be P. pachyrizi by a real-time PCR protocol (2). The diagnosis on this new host was verified by a USDA, APHIS National Mycologist in Beltsville, MD. Coral bean may serve as an additional overwintering host for P. pachyrhizi in the southeast. To our knowledge, this is the first report of soybean rust caused by P. pachyrhizi on E. herbaceae. References: (1) R. S. C. Christiano and H. Scherm, Phytopathology 97:1428, 2007. (2) R. D. Frederick et al. Phytopathology 92:217, 2002. (3) S. A. Isard et al. Online publication. doi:10.1094/PHP-2006-0915-01-RV. Plant Health Progress, 2006. (4) T. L. Slaminko et al. Plant Dis. 92:767, 2008.

Brown ring patch is a newly described disease of cool-season turfgrass first reported in Japan on creeping bentgrass (Agrostis palustris) (2) and later reported in California on annual bluegrass (Poa annua) (1). The disease is characterized by either patches or rings of discolored to blighted turfgrass that can range from a few centimeters to a meter in diameter. Affected turfgrass plants turn chlorotic and can be blighted from the crown to the leaf tips. Blight symptoms have been associated with fluffy white-to-cream aerial mycelium after extended incubation of the sample. Symptoms including patches of blighted turfgrass approximately 10 cm in diameter were observed on roughstalk bluegrass (Poa trivialis) that had been overseeded onto a dormant ‘Tifdwarf’ bermudagrass (Cynodon dactylon) putting green in Palatka, FL. A sample was submitted by the superintendent in June 2005 because symptoms were confused with dollar spot and a fungicide resistance issue was suspected. The sample produced abundant aerial mycelium after incubation. The pathogen was isolated on potato dextrose agar amended with rifampicin (100 ppm) and streptomycin (100 ppm) from Poa plants surface disinfested with 70% ethanol for 30 s. Colony and sclerotia morphology were consistent with Waitea circinata var. circinata as previously described (1,2). The teleomorph W. circinata var. circinata was not observed on plant material or culture plates. Amplified fragments of rDNA including internal transcribed spacers from the isolate were sequenced bidirectionally from four bacterial clones. The consensus sequences (GenBank Accession Nos. FJ029103, FJ029104, FJ029105, and FJ029106) matched with 99% homology (99% sequence overlap) isolate TRGC1.1 of W. circinata var. circinata described by Wong, NCBI Accession No. DQ900586 (1). Pots of ‘Cypress’ roughstalk bluegrass that were 1 week postemergence were inoculated with the pathogen using 10 infested wheat grains. Plants were incubated at 25°C in a sealed plastic bag with a moist paper towel in the bottom. Hyphae grew from the grains and colonized the grass. Individual plants began to turn chlorotic within 3 days and greater than 90% of the turf in pots was dead after 1 week. The fungus was reisolated from affected plants. Control pots were inoculated with uninfested wheat grains and showed no disease symptoms after 1 week. Inoculations were repeated twice more with the same results. To our knowledge, this is the first report of brown ring patch on P. trivialis in Florida. References: (1) K. A. de la Cerda et al. Plant Dis. 91:791, 2007. (2) T. Toda et al. Plant Dis. 89:536, 2005.

Soybean rust (SBR) survival and host availability (kudzu, Pueraria spp.) were assessed from November 2006 through April 2007 at six sites from the panhandle to southwest Florida. Micro loggers recorded both temperature and relative humidity hourly at each location. Periods of drought and cumulative hours below 0°C correlated with kudzu defoliation. Inoculum potential from detached kudzu leaves was evaluated in vitro under various temperature and relative humidity levels. Kudzu leaves with SBR kept at 4°C produced viable urediniospores with the highest germination at all moisture levels over time. Freezing temperatures (–4 and –20°C) drastically reduced spore germination. However, when leaves were incubated at low (

Stem blight of southern highbush blueberries has been attributed to Botryosphaeria dothidea (2). Symptoms include necrotic branches with attached leaves and brown discoloration of the vasculature extending the length of the affected branch. A 2007 field survey of stem blight in Florida resulted in isolates of the previously reported B. dothidea and Neofusicoccum ribis and isolates of unreported Lasiodiplodia theobromae (2). Isolates of L. theobromae were identified to species level by morphological characterization (3). Identity was confirmed by comparison of rDNA sequences of representative isolates (GenBank Accession No. FJ882072) to reference sequences (99% similarity to Accession No. EF622074) (1). Seven, fresh, pruning wounds on southern highbush blueberries cv. Misty were inoculated with a 10-mm V8 juice agar plug of isolate MixFC-6 taken from the margin of a 3-day-old colony. Seven wounds were inoculated with a sterile agar plug. All plugs were attached to the wounds with Parafilm. Mean lesion length 14 days after inoculation was 8.6 ± 2.4 cm. The pathogen was reisolated from the margin of lesions and identified by colony growth characteristics on potato dextrose agar. No lesions were observed on control plants. To our knowledge, this is the first report that stem blight of southern highbush blueberries in Florida can be caused by L. theobromae. References: (1) A. Alves et al. Fungal Divers. 28:1, 2008. (2) F. L. Caruso and D. C. Ramsdell. Compendium of Blueberry and Cranberry Diseases. The American Phytopathological Society, St. Paul, MN, 1995. (3) P. W. Crous et al. Stud. Mycol. 55:235, 2006.

Soybean rust, caused by Phakopsora pachyrhizi Syd., first was observed in the continental United States during 2004 on soybean (Glycine max (L.) Merr.) in Louisiana (4), and on kudzu (Pueraria montana (Lour.) Merr. var. lobata (Willd.) Maesen & Almeida) in Florida (2). Kudzu is a leguminous weed that is prevalent in the southern United States with its range extending northward into other states including Illinois. In October 2009, a kudzu patch located in Pulaski County in southern Illinois was investigated for the presence of soybean rust. Twenty-five leaflets were collected, and the abaxial sides of leaflets were evaluated visually for the presence of uredinia with a dissecting microscope. Uredinia and urediniospores were found on two leaflets. When viewed with a compound microscope, urediniospores were hyaline, echinulate, and measured 20 × 25 μm. On the basis of uredinia and urediniospores, the disease tentatively was identified as soybean rust caused by P. pachyrhizi. To confirm the identification, one leaflet with pustules was assayed with a Soybean Rust QuickStix Diagnostic Kit (Envirologix, Portland, ME). For the other leaflet, the area of the pustule was excised (approximately 28 mm2) and an area of the leaflet at the margin on the opposite half of the leaflet with no visible pustule (approximately 54 mm2) was excised. DNA was extracted from the excised areas of the leaflet for confirmation by quantitative PCR (Q-PCR) using primers and probe specific to P. pachyrhizi and P. meibomiae (Arthur) Arthur (1). Both the QuickStix Diagnostic Kit and the Q-PCR confirmed the diagnosis as soybean rust caused by P. pachyrhizi. Q-PCR also suggested the presence of a nonsporulating latent rust infection on the same kudzu leaflet at the margin on the opposite side of the midrib. Soybean rust first was confirmed on soybean in Illinois in 2006 (3), but to our knowledge, this is the first observation of the disease on kudzu in the state. This report confirms that at least some kudzu plants in Illinois are susceptible to soybean rust and that latent kudzu infection may exist without outward signs of the fungus. Currently, this is the most northern observation of soybean rust on kudzu in North America. It is unknown what role, if any, Illinois kudzu will play in the epidemiology of soybean rust in the state. Since kudzu tops die after the first frost, there is no expectation of P. pachyrhizi to overwinter in Illinois on kudzu as it does in some states adjacent to the Gulf of Mexico. References: (1) R. D. Frederick et al. Phytopathology 92:217, 2002. (2) P. F. Harmon et al. Online publication. doi:10.1094/PHP-2005-0613-01-RS. Plant Health Progress, 2005. (3) G. L. Hartman et al. Plant Dis. 91:466, 2007. (4) R. W. Schneider et al. Plant Dis. 89:774, 2005.

In May of 2008, samples of southern highbush blueberry (interspecific Vaccinium corymbosum hybrids) exhibiting marginal leaf necrosis were collected at a farm in Interlachen, FL. The cv. Star showed severe leaf scorch, partial defoliation, and a generally unthrifty growth structure of many thin twigs as has been observed in Georgia (1). The block of Star plants was approximately 10 years old and incidence of the disease was 100%. The grower reported the planting had become increasingly unproductive in the most recent 4 to 5 years. Plants of the cv. Windsor also showed scorch symptoms and yellow-to-red discoloration of leaves. Proportionally fewer Windsor plants showed disease symptoms than Star plants and the disease was not as severe on this cultivar on the basis of visual estimates at the time. Each sample consisted of 5 to 10 cuttings of spring wood with attached leaves showing marginal necrosis taken from a single plant. Three samples, two from Star plants and one from a Windsor plant, were divided into two subsamples each. One subsample was submitted to Agdia for Xylella fastidiosa double-antibody sandwich (DAS)-ELISA assay (TSE XF; Agdia Inc., Elkhart IN). All three samples were reported as positive for X. fastidiosa by DAS-ELISA. A number of asymptomatic plants from this farm and other additional farms were tested in the same manner and results were negative. The other subsample was used for isolation of the causal bacterium. Petioles and main veins from symptomatic leaves were surface disinfested in 1% sodium hypochlorite, cut into segments (0.5 cm), and squeezed with forceps or pliers. Sap that exuded from the segment was blotted directly onto periwinkle wilt medium (2). Bacterial colonies consistent in morphology with X. fastidiosa that were DAS-ELISA positive were obtained from all three samples. One isolate from each sample was inoculated into four Star plants each with the pin-pricking method (3). Leaf scorch symptoms were first observed 8 weeks after inoculation. By 12 weeks after inoculation, all plants inoculated with the three isolates had developed symptoms, including defoliation. Plants inoculated without bacteria showed no symptoms. X. fastidiosa was reisolated from symptomatic plants. Bacterial leaf scorch is an important emerging disease that threatens the southern highbush blueberry industry in the south. On certain cultivars like Star, the potential to reduce yield appears to be great. Differences between cultivars are likely, but have not yet been explored. Additional research is needed into the epidemiology of the disease and potential vectors of pathogen transmission. References: (1) C. Chang et al. HortScience 44:413, 2009. (2) M. Davis et al. Curr. Microbiol. 6:309, 1981. (3) D. L. Hopkins et al. Phytopathology 75:713, 1985.

Field studies to quantify the effects of shade intensity and duration on soybean rust caused by Phakopsora pachyrhizi were carried out in Florida in 2006 and 2007. Soybean plants at the V4 stage were inoculated with urediniospores at 2100, 0000, and 0200 h. Inoculated plants were either placed in cages that were covered with shade cloths of different mesh sizes allowing 70, 50, or 20% transmission of sunlight or were not covered so that the plants received 100% of sunlight. Plants kept under 20 and 100% sunlight were sampled 12, 18, and 36 h after inoculation to determine the in vivo germination percentage of urediniospores and the percentage of germ tubes that formed appressoria. In separate experiments, inoculated plants were placed under the shade (20% sunlight) and moved to unshaded conditions after 1, 2, and 7 days. For all experiments, soybean rust incidence and severity were rated 12 days after inoculation. Higher levels of disease incidence and severity were detected in plants under shade compared with those under full sunlight. Shade duration greater than 2 days favored disease development. Within 36 h, in vivo germination of urediniospores and formation of appressoria were not significantly affected by the treatments. These results may explain why soybean rust is more severe in the lower canopy and shaded areas in the field.

Stem blight of southern highbush blueberry (SHB) results in premature plant mortality and has been identified by Florida blueberry growers as the economically most important disease for the industry. In 2007, plants with stem blight and dieback symptoms were sampled at 4-month intervals from two farms located in Alachua and Polk Co., FL. In all, 30 cane samples (stem blight) and 30 crown segments (dieback) were collected at each sample date and each location. In total, 360 samples were collected; fungal species in the family Botryosphaeriaceae were isolated from 85% of the samples. Based on morphology and phylogenetic analysis of the internal transcribed spacer region and elongation factor 1-α (EF1-α) sequences, two dominant species recovered from SHB in Florida were identified: Lasiodiplodia theobromae and Neofusicoccum ribis. Species isolation was independent of location, symptom type, and time of year. Additional samplings are needed to investigate population change over multiple years and in the rest of the southeastern United States. Breeding for resistance and management of stem blight and dieback in Florida should focus on these two fungal species.

Camelina sativa (L.) Crantz, Brassicaceae, whose common name is Crantz-large-seeded false flax, is an annual oilseed species. It is grown as a forage and biofuel crop in Europe and North America. False flax is an ideal low-input crop for biodiesel production, because of its low requirements for nitrogen fertilizer and pesticides. Production costs of this crop are substantially lower than those of many other oilseed crops such as rapeseed, corn, and soybean. It is an excellent rotation crop and can reduce disease and insect and weed pressure in wheat fields. During the spring of 2011, commercial and research plantings of C. sativa cultivar Calena in Liberty and Gadsden counties in north Florida developed symptoms typical of downy mildew. In spring of 2012, the same symptoms were observed in experimental plantings of false flax. A white downy mold was observed on the upper third portion of the plants, on the upper stem internodes, and on the developing seed. The affected stems exhibited a twisted growth. Conidiophores had main trunks with dichotomous branches terminating in slender curved tips. Conidia were ovoid and 28 to 45 (mean 36) μm long and 22 to 38 (mean 30) μm wide. Conidiophores were branched (three to four branches, each with six to eight curved tips) and ranged from 107 to 236 μm long and 5 to 14 μm wide. Mycelium was obtained directly from diseased plants for DNA extraction (Qiagen DNeasy Plant Mini Kit, Valencia, CA). Primers ITS1 and ITS4 were used for PCR amplification (4). The PCR product was sequenced bidirectionally with the PCR primers. A consensus nucleotide sequence (Accession JQ997103) was compared to those in the NCBI GenBank database using a BLAST search. The sequence was 99% similar to sequence from Hyaloperonospora camelinae (Gäum.) Göker, Voglmayr, Riethm, M. Weiss & Oberw. (Accession AY198249.1) with a 95% query coverage (1). Pathogenicity was established by applying white conidial masses of downy mildew from field samples to stems of 4-week-old plants grown in pots in a greenhouse maintained at 25 ± 2°C. Noninoculated plants maintained under the similar conditions served as control. Symptoms and signs of downy mildew developed after 14 days only on inoculated plants. Downy mildew constitutes a serious threat to the cultivation of C. sativa in Florida because of the humid climate favoring disease development. Diseased plants may reduce yield and disease management would increase production costs. H. camelinae was previously reported on C. sativa in Oregon, Minnesota, Montana (3), and Nebraska (2). To the best of our knowledge, this is the first report of downy mildew caused by H. camelinae on C. sativa in Florida. References: (1) M. Göker et al. Canad. J. Bot. 81:672, 2003. (2) R. M. Harveson et al. Plant Health Progress. 2011. doi: 10.1094/PHP-2011-1014-01-BR. (3) M. L. Putnam et al. Plant Health Progress. 2009. doi: 10.1094/PHP-2009-0910-01-BR. (4) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, San Diego, 1990.

Guinea grass is an invasive perennial C4 grass and is a common weed around agricultural crops in Louisiana, Texas, and Hawaii, USA (Overholt and Franck 2019). In November 2018, leaf spots were observed on Guinea grass occurring in an organic garden located in Gainesville, Florida, USA. Lesions were oblong to irregular, dark grey to brownish center with pale-yellow to brownish black margin. Lesions had coalesced, forming necrotic margins that spread from the leaf tip, resulting in leaf blight and collapse of the canopy. Pieces of symptomatic leaf blades (5 sq cm) were surface sterilized (1 min), washed with sterile distilled water and plated onto water agar media plates. Plates were incubated at 27°C under 12-h light/dark for 3 to 5 days. Grey to black cottony mycelium was consistent on all plates and produced conidia characteristic of Bipolaris spp. Conidia were transferred to potato dextrose agar (PDA) plates with a 0.5 mm diameter sterile needle. Three isolates GG1, GG2 and GG3 were successfully grown on PDA. Conidia were black to brown colored, distoseptate with 3 to 8 septa and measured from (60.6- )70-105(-139.8) × (16.0-)17-23(-25.9) μm (avg: 93.3 μm, n=35, SD = 20.6; avg = 21.3 μm, n = 35, SD = 2.89). Conidiophores were in groups or single, brown, smooth and straight, septate and swollen at upper tip. Sigma Extract-N-Amp was used for genomic DNA extraction. Primers ITS1/ITS4 and GPD1/GPD2 (Berbee et al. 1999) were used to amplify and sequence the internal transcribed spacer region (ITS) and partial glyceraldehyde-3-phosphate dehydrogenase (GPDH) gene, respectively. Sequences were aligned using MUSCLE and alignment was trimmed for length. Maximum likelihood phylogenetic trees were constructed with 1,000 bootstrap samples based on the K2+G substitution model, selected by BIC for these two loci using Mega X (Kumar et al. 2018). The ITS and GPDH sequences of GG1, GG2 and GG3 (Genbank accessions MT514518-20, MT576654-56), grouped with B. yamadae isolates CPC_28807 and CBS_202.29 in phylogenetic trees (Marin-Felix et al. 2017). All three isolates from Guinea grass were inoculated on Sach's agar (Luttrell 1958) at 27°C under 12-h light/dark for a week, but no sexual morph was observed, and consistent for two repeated inoculations. To fulfill Koch's postulates, one isolate, GG1, was used. Conidia were harvested from a one-week-old colony grown on PDA incubated at 27°C and 12-h light/dark cycle. The concentration of the conidial suspension was adjusted to 105 conidia/ml using a hemocytometer. Using a Passche H-202S airbrush sprayer, five-week-old seedlings of Guinea grass were sprayed until runoff with the conidia suspension or 0.5% tween water only. Each treatment included four replicates and the experiment was repeated. Leaf spot symptoms were observed on the seedlings inoculated with conidia, whereas seedlings sprayed with water were asymptomatic. Cultures with the expected morphology were isolated from symptomatic leaf blades and absent from control plants. To our knowledge, this is the first report of leaf spot on Guinea grass caused by B. yamadae in Florida, USA. B. yamadae was previously reported from Guinea grass in India, and from other Panicum species in the northern USA (Farr and Rossman 2019). B. yamadae was also isolated from sugarcane in Cuba and China, and corn in Japan (Manamgoda et al. 2014, Raza et al. 2019), which suggests that it has the potential to impact agronomic crops in Florida, such as sugarcane and corn.

Peach rust is a fungal disease commonly caused by Tranzchelia discolor (Fuckel) Tranzschel & Litvinov that attacks plants in the genus Prunus, including peach, nectarine, almond, plum, apricot, and cherry. In the Southeastern United State, the fungus is most common on peach orchards during summer and fall. The peach rust severity depends on the climatic conditions (temperature and rainfall), hosts (peach cultivars) and geographic location. Fungus rust is spread by airborne spores, which depend on moisture for infection. Where warm temperatures and high rainfalls usually result in severe peach rust infections. Florida’s summer rainfall provide favorable conditions for peach rust development. Despite, all currently available cultivars of peach in Florida are susceptible to the disease (Adaskaveg et al. 2012). Further studies of subtropical peach cultivars have shown differences for peach rust tolerance, measured by leaf retention, and rust incidence in the orchards (Alves et al. 2014; Citadin et al. 2010)

Peach fungal gummosis (PFG) is a vascular disease that limits the growth and yield of peach orchards in the southeastern United States. This 6-page document discusses the symptoms and management of PFG. Written by Daniel Mancero-Castillo, Ali Sarkhosh, Sara Sherman, Mercy Olmstead, Philip Harmon, and Thomas Beckham and published by the UF/IFAS Horticultural Sciences Department, July 2018. https://edis.ifas.ufl.edu/hs1265

Information contained in this 4-page publication is intended for Florida blueberry growers to use as a guide in the identification of anthracnose, a group of fungal pathogens that affects a wide range of plants, including southern highbush blueberries (SHB). Written by Douglas A. Phillips, Maria C. Velez-Climent, Philip F. Harmon, and Patricio R. Munoz and published by the UF/IFAS Plant Pathology Department, May 2018.https://edis.ifas.ufl.edu/pp337

Species in the fungal family Botryosphaeriaceae are significant pathogens of peach. The climatic conditions in the Southeastern USA are conducive to the development of peach fungal gummosis (PFG) with an estimated yield reduction of up to 40% in severe cases. Genotypes with resistance to this PFG were identified in interspecific crosses and segregating backcross populations generated using Kansu peach (Prunus kansuensis Rehder), almond [Prunus dulcis (Mill.) D.A. Webb], and peach [Prunus persica (L.) Batsch]. Hybrids were evaluated for four consecutive years in field conditions. Data generated was validated in different environments using clonal replicates of the hybrids. The F1 and BC1F1 segregation population data suggest a dominant allele for PFG resistance originating from almond. Segregation and mapping analysis located the PFG resistance locus on a chimeric linkage groups 6–8 near the leaf color locus. The molecular markers identified will facilitate marker-assisted selection (MAS) and introgression of this resistance trait into commercial peach germplasm.

Seed production is a critical component in agricultural systems based on bahiagrass and ergot has been reported to significantly reduce seed quality in tetraploid cultivars. Seed yield and quality are important traits to evaluate in the advanced breeding lines developed at the University of Florida. Resistance to ergot was assessed in seven tetraploid bahiagrass breeding lines and the cultivar Argentine. Tebuconazole and pyraclostrobin also were evaluated for managing ergot and increasing seed quality. Argentine and two tetraploid hybrids (Hyb1 and Hyb2) showed the highest levels of ergot severity and incidence. Three wild-type bahiagrass lines (WT-2, WT-4 and WT-5) performed significantly better than Argentine and could be considered resistant to ergot. Anthesis was the critical stage in relation to ergot infection, and a single application of tebuconazole at anthesis reduced ergot severity; however, neither fungicide was able to reduce ergot incidence. Tebuconazole and pyraclostrobin improved seed set, and reproductive efficiency was 2.4% higher after the application of tebuconazole. The slight increase in reproductive efficiency following fungicide application may not be economically justifiable for seed production in bahiagrass. Three advanced tetraploid breeding lines (Hyb1, WT-3, and WT-5) exhibited adequate seed production to be considered for cultivar release.Accepted for publication 24 February 2015. Published 17 April 2015.

Two diseases of St. Augustinegrass (SAG) [Stenotaphrum secundatum (Walt.). Ktze.] are caused by different anastomosis groups (AGs) of Rhizoctonia solani. Brown patch (BP) is a foliar disease of little economic importance, and large patch (LP) causes leaf sheath rot and death of affected turfgrass shoots and stolons. St. Augustinegrass genotypes were inoculated with an isolate that causes BP and an isolate that causes LP in repeated experiments. Three disease severity parameters were calculated from data recorded from each genotype, including final disease severity (Y), area under the disease progress curve (AUDPC), and the apparent infection rate (r L). The inoculation protocol reliably produced symptoms, and both r L and AUDPC provided statistically significant separations between genotypes for their susceptibility to BP and LP. A significant interaction between isolate and genotype was observed, and some genotypes that were very susceptible to LP were among the least susceptible to BP. These data suggest that differences in resistance to LP can be quantified in SAG genotypes, but genotype response may be isolate dependent.

Field performance of southern highbush blueberry (Vaccinium corymbosum L. interspecific hybrids) cultivars Emerald, Jewel, and Primadonna derived from softwood cuttings (SW) and tissue culture (TC) was evaluated in Citra and Haines City, FL, in 2010–12. Both fields were planted in Apr. 2010 on sandy soil amended with pine bark. Plant height and width were recorded at both locations, from which plant canopy volume was calculated. Additionally, whole plants were harvested at planting and after the first growing season, after the first fruit harvest, and after the second growing season. Average plant height and width, number of major canes, and total shoot number were determined at each sampling date. Dry weights for roots, crowns, canes, shoots, and leaves were obtained. Although propagation method affected plant canopy volume during the first season, no effects were observed by the end of the second growing season. At planting and after the first and second growing seasons, TC plants of the three cultivars had more major canes. Total shoot number per plant was greater for TC ‘Jewel’ at all dates but ‘Emerald’ TC plants had more shoots only at planting and after the first growing and harvest seasons. Tissue culture resulted in increased plant dry weights of ‘Jewel’ and ‘Emerald’ after the first and second growing seasons. There were no significant differences in total number of shoots or plant dry weight between TC and SW-derived ‘Primadonna’ plants at any point during the study.

Florida has been affected by eight hurricanes since 2000. This new 3-page publication discusses the types of hurricane damage that occur in blueberry production operations, the impacts of these damages, and some recommendations on best management practices in the aftermath of a storm. Written by Douglas A. Phillips, Jeffrey G. Williamson, and Philip F. Harmon and published by the UF/IFAS Horticultural Sciences Department. https://edis.ifas.ufl.edu/hs1342

The complete genome of a variant of the multi-segmented (+) RNA virus blueberry necrotic ring blotch virus (BNRBV), which has not been assigned to a genus, was obtained from foliar red lesions on southern highbush blueberries grown in Alachua Co., Florida. The genome organization of this variant, BNRBV-RL, is the same as that of BNRBV: four genomic segments and seven ORFs (one ORF on each of RNA 1, RNA 2, and RNA 4 and as many as four ORFs on RNA 3). BLAST analysis revealed nucleic acid sequence identities of 89 %, 90 %, 90 % and 86 % to BNRBV RNA 1, RNA 2, RNA 3 and RNA 4, respectively. Phylogenetic analysis of the amino acid sequence of the putative RdRp domain indicated that BNRBV-RL was closely related to BNRBV and less related to citrus leprosis virus type C and three other mite-transmitted viruses. The nucleotide and amino acid sequence differences between BNRBV-RL and BNRBV combined with differences in symptom expression in blueberry would suggest that BNRBV-RL is a strain of BNRBV.

Botryosphaeria spp. are ligninolytic ascomyceteous fungi that incite many diseases in economically important woody plant species. Four Botryosphaeria isolates, Botryosphaeria rhodina (Lasiodiplodia theobromae), Botryosphaeria obtusa, Botryosphaeria dothidea and Botryosphaeria ribis (Neofusicoccum ribis) were used in this study. Ten naturally occurring phenolic compounds from plants were tested to evaluate their effect on mycelium growth and the production of ligninolytic and pectinolytic enzymes. The effect of phenolic compounds in vitro varied with the Botryosphaeria isolates. Inhibition of mycelium growth was dose-dependent, and varied from 2 to 100% inhibition in the ten phenolic compounds tested except syringic acid, which has no toxic effect on mycelium of Botryosphaeria isolates. A significant decrease in laccase production occurred when Botryosphaeria isolates were grown on phenolic compounds. Benzoic acid significantly inhibited pectinase activity in all isolates. The percent inhibition of pectinase activity in B. dothidea and B. obtusa was significantly increased in the presence of salicylic acid and syringic acid, respectively.

Petrifilms are dehydrated agar culture plates that have been used to quantify colony forming units (CFU) mL of either aerobic bacteria (Petrifilm-AC) or fungus (Petrifilm-YM), depending on substrate composition. Microbes in irrigation systems can indicate biofilm risk and potential clogging of irrigation emitters. The research objective was to compare counts on Petrifilms versus traditional, hydrated-agar plates using samples collected from recirculated irrigation waters and cultures of isolated known species. The estimated count (in CFU mL) from a recirculated irrigation sample after 7 d of incubation on Petrifilm-YM was only 5.5% of the count quantified using sabouraud dextrose agar (SDA) with chloramphenicol after 14 d. In a separate experiment with a known species, Petrifilm-YM did not successfully culture zoospores of . Isolates of viable zoospores were cultured successfully on potato-dextrose agar (PDA), with comparable counts with a vegetable juice medium supplemented with the antibiotics pimaricin, ampicillin, rifamycin, pentochloronitrobenzene and hymexazol (PARP-H). The quantification of pv. Begoniaceae on Petrifilm-AC was not significantly different ( < 0.05) than on PDA, but was lower than on Reasoner and Goldrich agar (R2A) or with a hemocytometer. The current formulation of Petrifilm-YM is unlikely to be a useful monitoring method for plant pathogens in irrigation water because of the inability to successfully culture oomycetes. However, Petrifilm-AC was an effective method to quantify bacteria and can provide an easy-to-use on-farm tool to monitor biofilm risk and microbial density.

The objective was to analyze the physical, chemical, and biological water quality in horticulture irrigation systems in 24 ornamental plant greenhouses and nurseries in the United States. At each greenhouse or nursery, water was collected from up to five points (“Sample Types”) which included 1) “Source” from municipal or private well supplies, 2) “Tank” from enclosed storage containers, 3) “Subirrigation” from water applied to crops in ebb-and-flood systems, 4) “Furthest Outlet” that were irrigation emitters most distant from the Source, and 5) “Catchment Basin” from open outdoor retention areas. On average, Source water had the highest physical and microbial quality of Sample Types including the highest ultraviolet (UV) light transmission at 86%, lowest total suspended solids (TSS) at 3.1 mg·L−1, and lowest density of aerobic bacteria with 1108 cfu/mL of water. Average quality of recycled water from Subirrigation or Catchment Basins did not meet recommended levels for horticultural irrigation water for UV transmission (68% to 72% compared with recommended 75%), microbial counts (>100,000 cfu/mL compared with recommended −1 compared with recommended −1). Irrigation water stored in Tanks or applied at Furthest Outlets had lower physical and biological water quality compared with Source water. Level of aerobic bacteria counts highlighted a risk of clogged microirrigation emitters from microbial contaminants, with highest bacteria levels in recirculated irrigation water. The physical, chemical, and microbial water quality results indicate a need for more effective water treatment to improve biological water quality, particularly with recirculated irrigation.

Morphology, vegetative compatibility groups, and molecular characteristics were compared among 47 isolates of the dollar spot pathogen Sclerotinia homoeocarpa. Isolates were collected from cool- and warm-season turfgrasses in Florida and the northern United States. Mycelial pigment accumulation, substratal stromata formation, and symptom development were used to separate the collection into two distinct morphological types: a common-type (C-type) and a Floridian-type (F-type). Phylogenetic relationships estimated from ITS sequences supported the morphological typing. Identification and characterization of the S. homoeocarpa mating-type locus revealed an idiomorphic organization for both C- and F-types with nearly equal frequencies of each mating types present in both groups. These findings suggest heterothallic control of mating and indicate potential for outcrossing in both groups. Dollar spot disease of turfgrass in Florida is caused by two distinct morphological types of S. homoeocarpa which may be cryptic species. These findings could have implications for disease management.

ADDITIONAL INDEX WORDS. Canada, emerging pests and diseases, exports, floriculture, imports, ornamental plants SUMMARY. The purpose of this study was to evaluate the U.S.-Canadian Greenhouse Certification Program (USGCP) that was initiated in 1998. A survey consisting of 34 questions was designed and 43 out of 48 nurseries in Florida participating in the USGCP were visited. Based on the answers to the questionnaire, most of the nurseries were in compliance with the majority of USGCP requirements, growers were satisfied with the program, and there was an economic benefit to participating in the program. The main problems identified were theambiguous wording of some of the requirements and the impracticality of keeping imported and domestic plants completely segregated. Moreover, many of the respondents did not have a written description of a pest management plan. Chi square statistical analysis showed that there was almost no difference between nursery groups in their responses to the majority of the survey questions, indicating that the USGCP is a successful program forbothlarge andsmallnurseries.Thisquantitativeassessment oftheUSGCP isthe first assessment conducted for this program and discussed in a peer-reviewed publication.

Seashore paspalum (Paspalum vaginatum) is a saline-tolerant, warm-season turfgrass species popular for golf course use in tropical and subtropical climates. A new variety of Waitea circinata (proposed as W. circinata var. prodigus) is described as the causal agent of basal leaf blight, a novel disease of seashore paspalum. Foliar necrosis and canopy thinning of seashore paspalum were observed on three different golf course fairways in Florida over an 18-month period. Five isolates with profuse, pink to yellow mycelia and small, salmon-colored or yellow to light-brown sclerotia were cultured from diseased turf foliage. Isolates grew rapidly over a temperature range of 25 to 35°C and were initially identified as an uncharacterized variety of W. circinata. Internal transcribed spacer sequences of rDNA from the isolates were compared with sequences from previously described W. circinata varieties. The paspalum isolates formed a phylogenetic clade that was distinct from the other W. circinata varieties. Pathogenicity was confirmed on ‘SeaDwarf’ and ‘SeaIsle Supreme’ seashore paspalum, ‘Penncross’ creeping bentgrass (Agrostis stolonifera), ‘Senesta’ bermudagrass (Cynodon dactylon), and ‘Dark Horse’ roughstalk bluegrass (Poa trivialis). The geographical distribution and potential impact of basal leaf blight is unknown. However, the range of potential turfgrass hosts and environmental conditions conducive for disease development suggest that the pathogen may infect other species in addition to seashore paspalum.

This 38-page publication provides current information on pest, disease, and weed management, and plant growth regulator use for commercial blueberries in Florida. It is a minor revision written by Jeffrey G. Williamson, Philip F. Harmon, Oscar E. Liburd, and Peter Dittmar, and published by the Horticultural Sciences Department, September 2018. HS1156/HS380: 2022 Florida Blueberry Integrated Pest Management Guide (ufl.edu)

In the fall of 2016 and spring of 2017 Ralstonia solanacearum was isolated from blueberry plants (Vaccinium corymbosum) at seven farms in six counties in Florida. Symptoms were bronzing of leaves, marginal leaf necrosis, and bacterial streaming. The symptomatic plants resembled blueberry plants infected with Xylella fastidiosa. Symptomatic tissue samples were removed, surface sterilized, cut into distilled water, and streaked onto triphenyltetrazolium chloride medium (Kelman, 1954). Mucoid colonies with red pigmented, egg-shaped pattern characteristic of R. solanacearum formed within 48 hr at 28°C. In the fall of 2016, all bacterial strains were isolated from the Southern highbush blueberry cultivar ′Arcadia′, but as we widened our search via extension communications with growers, strains were isolated from other highbush cultivars. Ralstonia strains were characterized into phylotypes and sequevars by sequencing both the Internal Transcribed Spacer (ITS) region of the 16S rRNA gene (AMB013: CATCCACCGCTTGT...