Coryneum Twig Canker on Southern Live Oak in Florida

In May 2001, following several years of severe drought, a depressed twig canker was observed on southern live oak (Quercus virginiana) in central Florida. Disease symptoms included twig and branch canker and dieback, distortion of young leaves, and premature leaf drop. Observation of conidia from sporulating acervuli revealed that Coryneum japonicum was associated with the cankers (1,2). The fungus produced abundant, subepidermal, dark brown, linearly arranged acervuli on affected tissues. Conidia were light brown, narrowly fusiform, often curved, and tapered toward an obtuse apex. The conidia had truncate bases and were five to seven distoseptate. Septa were medium to dark brown and sometimes prominent. The length to width ratio of conidia was >4:1. Under normal weather conditions, twig elongation of live oak trees is usually 30 to 60 cm per growing season; however, only 7 to 10 cm was observed on trees affected by C. japonicum. The fungus has been reported on bark and dead twigs of Quercus macrocarpa, Q. gambelii, Q. dilatata, and other species of Quercus in Canada, Pakistan, and the United States (2). To our knowledge, this is the first report of C. japonicum in Florida and on southern live oak trees. A specimen has been deposited in the U.S. National Fungus Collections (BPI number 841441). References: (1) B. C. Sutton. Mycol. Pap. 138:33, 1975. (2) B. C. Sutton. The Coelomycetes, CMI, Kew, England, 1980.

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The Efficacy of Paclobutrazol Soil Application as it Relates to the Timing of Utility Right-of-Way Pruning

Arboriculture & Urban Forestry ◽

10.48044/jauf.2016.008 ◽

2016 ◽

Vol 42 (2) ◽

Author(s):

Chris Haugen ◽

Kevin Tucker ◽

Alex Smalling ◽

Emily Bick ◽

Steve Hoover ◽

...

Keyword(s):

Plant Growth Regulator ◽

Growth Response ◽

Power Lines ◽

Time Data ◽

Application Timing ◽

Right Of Way ◽

Quercus Virginiana ◽

Live Oak ◽

Oak Trees ◽

The Ideal

The plant growth regulator paclobutrazol’s effect on live oak trees (Quercus virginiana) was evaluated to determine optimum timing of application and pruning time in Louisiana. Variables considered included length of branch regrowth, branch distance to conductor, pruning time and biomass chipping time. Data were evaluated to determine the ideal application timing of paclobutrazol relative to time of pruning. Live oak trees treated with paclobutrazol had significantly reduced branch regrowth, pruning time and chipping time, as compared to control trees regardless of application timing. Paclobutrazol application on live oak trees was idealized within 90 days pre- to 90 days post-prune. Economically, significant gains were found by utilizing this tool ranging from 180 days pre- to 180 days post-prune, allowing for application timing flexibility to reduce the growth of trees near power lines. Paclobutrazol treated live oak trees demonstrated significantly less re-growth response.

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Water Stress and Osmotic Adjustment during Post-digging Acclimatization of Quercus virginiana Produced in Fabric Containers

Journal of Environmental Horticulture ◽

10.24266/0738-2898-10.4.208 ◽

1992 ◽

Vol 10 (4) ◽

pp. 208-214

Author(s):

R.C. Beeson ◽

E.F. Gilman

Keyword(s):

Water Stress ◽

Osmotic Adjustment ◽

Fine Root ◽

Early Summer ◽

Root Weight ◽

Quercus Virginiana ◽

Water Potentials ◽

Live Oak ◽

Oak Trees ◽

Osmotic Potentials

Abstract Quercus virginiana Mill. (live oak) trees produced in in-ground 61 cm (24 in) diameter fabric containers were overhead misted and given root ball irrigation after harvesting during early summer. Duration and frequency of overhead misting was reduced to zero over a 3 week period. Water potentials (ΨT) were measured diurnally and osmotic potentials measured from leaves at midday. Intermittent overhead misting was as effective as continuous overhead misting in maintenance of ΨT above −1.0 MPa. Water potentials of −1.5 to −2.0 MPa were measured when the period between overhead misting was expanded from 30 min to 45 min. Osmotic adjustment occurred only in trees receiving overhead misting. Trees receiving only root ball irrigation developed ΨT below −2.5 MPa within 5 days after harvesting. After 3 weeks, ΨT and osmotic potentials were the same for all treatments. In a second experiment, trees were root pruned inside the fabric container 11 weeks before harvest. All root pruned trees survived acclimatization, but only 50% of unpruned trees survived. Water relations were similar to trees in Experiment 1. Surviving trees, both pruned and unpruned, had a significantly higher percentage of fine root weight (roots < 2 mm diameter) than trees that did not survive.

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First Report of Powdery Mildew of Platanus occidentalis Caused by Erysiphe platani in Korea

Plant Disease ◽

10.1094/pdis-10-12-0982-pdn ◽

2013 ◽

Vol 97 (6) ◽

pp. 843-843 ◽

Cited By ~ 2

Author(s):

Y. J. La ◽

S. E. Cho ◽

H. D. Shin

Keyword(s):

North America ◽

Powdery Mildew ◽

Its Region ◽

The United States ◽

Control Measures ◽

Base Substitution ◽

Width Ratio ◽

First Report ◽

Platanus Occidentalis ◽

Young Leaves

Platanus occidentalis L., called American sycamore or American plane, is native to North America. The trees are commonly planted throughout the world on the sides of roads and in parks. In June 2012, diseased leaves exhibiting signs of powdery mildew from a park in Daegu City of Korea were sent to Plant Clinic of Seoul National University for diagnosis. Our observations in Daegu City during September and October 2012 showed that nearly 99% of the approximately 1,000 trees surveyed were infected with a powdery mildew. Voucher specimens (n = 6) were deposited at the Korea University Herbarium (KUS). Symptoms were characterized by chlorosis, distortion, or cupping of young leaves. White superficial colonies developed amphigenously on leaves. Hyphae were flexuous to straight, branched, septate, 4 to 7 μm wide, and had lobed appressoria. Conidiophores were 120 to 350 × 5 to 7.5 μm and produced conidia singly. Foot-cells of conidiophores were straight, cylindric, and 115 to 200 μm long. Conidia were hyaline, ellipsoid-ovoid, measured 33 to 47.5 × 17.5 to 29 μm with a length/width ratio of 1.5 to 2.0, lacked distinct fibrosin bodies, and showed reticulate wrinkling of the outer walls. Germ tubes were produced on the subterminal position of conidia. No chasmothecia were observed. The structures and measurements were compatible with those of the anamorphic state of Erysiphe platani (Howe) U. Braun & S. Takam. (1). To confirm the identification, the complete internal transcribed spacer (ITS) region of the rDNA from isolate KUS-F26959 was amplified with nested PCR and sequenced. The resulting sequence of 625 bp was deposited in GenBank (Accession No. JX997805). A GenBank BLAST search of this sequence showed only one base substitution with the four sequences (JQ365940 to JQ365943) of E. platani on Platanus spp. Pathogenicity was confirmed through inoculation tests by gently pressing diseased leaves onto young leaves of three 2-year-old disease-free seedlings. Three non-inoculated plants were used as control. Plants were maintained in a greenhouse at 24 to 30°C. Inoculated leaves developed symptoms after 7 days, whereas the control plants remained symptomless. The fungus present on the inoculated leaves was morphologically identical to that observed on the original diseased leaves, fulfilling Koch's postulates. Since E. platani first was recorded in the United States in 1874, it has been regarded as endemic in North America. From the second half of the 20th century, introduction and expansion of the range of this fungus to South America, South Africa, Australia and New Zealand, Europe, and Asia have been reported (1,2). To our knowledge, this is the first report of E. platani infections of P. occidentalis in Korea. This species was recorded on P.× hispanica from Japan in 1999 (4) and on P. orientalis from China in 2006 (3), suggesting invasive spread of the sycamore powdery mildew in East Asia. Since American sycamores are widely planted in Korea, control measures should be made to prevent further spread of the disease. References: (1) U. Braun and R. T. A. Cook. Taxonomic Manual of the Erysiphales (Powdery Mildews), CBS Biodiversity Series No.11. CBS, Utrecht, 2012. (2) D. F. Farr and A. Y. Rossman. Fungal Databases. Syst. Mycol. Microbiol. Lab., Online publication, ARS, USDA, Retrieved October 22, 2012. (3) C. Liang et al. Plant Pathol. 57:375, 2008. (4) S, Tanda. J. Agric. Sci., Tokyo Univ. Agric. 43:253, 1999.

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Water Relations of Field-grown Quercus virginiana Mill. from Preharvest through Containerization and 1 Year into a Landscape

Journal of the American Society for Horticultural Science ◽

10.21273/jashs.119.2.169 ◽

1994 ◽

Vol 119 (2) ◽

pp. 169-174 ◽

Cited By ~ 3

Author(s):

R.C. Beeson

Keyword(s):

Growth Rate ◽

Water Potential ◽

Water Relations ◽

Water Status ◽

Root Pruning ◽

Quercus Virginiana ◽

Live Oak ◽

Transplant Shock ◽

Oak Trees ◽

Landscape Water

Large (≈5 m high) Quercus virginiana Mill. (live oak) trees produced in 0.64-m-diameter in-ground fabric containers were root pruned or not root pruned inside containers before harvest. Harvested trees were grown in two sizes of polyethylene containers for 10 months, then transplanted into a landscape. Water potential (ψT) of small branches (<4 mm in diameter) was measured diurnally during containerization and for 1 year in the landscape. Root pruning had no influence on postharvest survival. Neither root pruning nor container size affected tree water status during containerization or in the landscape. All surviving trees recovered from transplant shock following harvest after 16 weeks in a container, independent of treatment. In the landscape, 35 weeks of daily irrigation were required before dusk ψT declined to within 0.1 MPa of predawn values, a result indicating alleviation of transplant shock. Trunk growth rate during containerization was highest in larger containers. However, in the landscape, root pruning and small containers were associated with higher trunk growth rate. Tree water status during containerization and in the landscape is discussed.

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Human-mediated disturbance in multitrophic interactions results in outbreak levels of North America's most venomous caterpillar

Biology Letters ◽

10.1098/rsbl.2019.0470 ◽

2019 ◽

Vol 15 (9) ◽

pp. 20190470 ◽

Cited By ~ 2

Author(s):

Glen R. Hood ◽

Mattheau Comerford ◽

Amanda K. Weaver ◽

Patricia M. Morton ◽

Scott P. Egan

Keyword(s):

Species Interactions ◽

Large Scale ◽

Population Level ◽

Multitrophic Interactions ◽

Enemy Release ◽

Ecological Disturbance ◽

Quercus Virginiana ◽

Avian Predators ◽

Live Oak ◽

Oak Trees

Anthropogenic environmental change is predicted to disrupt multitrophic interactions, which may have drastic consequences for population-level processes. Here, we investigate how a large-scale human-mediated disturbance affects the abundance of North America's most venomous caterpillar species, Megalopyge opercularis . Specifically, we used a natural experiment where netting was deployed to cover the entire canopies of a subset of mature southern live oak trees ( Quercus virginiana ) to exclude urban pest birds (grackles and pigeons), throughout an 8.1 km 2 area encompassing a medical centre in Houston, Texas. We used this experimental exclusion to test the following hypothesis: release from avian predators increases caterpillar abundance to outbreak levels, which increases the risk to human health. Results from a multi-year survey show that caterpillar abundance increased, on average, more than 7300% on netted versus non-netted trees. Thus, increases in caterpillar abundance due to anthropogenic enemy release increase human exposure to this venomous pest, and should be considered a health threat in the area. This study emphasizes the unforeseen consequences of ecological disturbance for species interactions and highlights the importance of considering ecology in urban planning.

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First Report of Powdery Mildew Caused by Podosphaera leucotricha on Photinia serrulata in China

Plant Disease ◽

10.1094/pdis-05-12-0473-pdn ◽

2012 ◽

Vol 96 (11) ◽

pp. 1695-1695 ◽

Cited By ~ 3

Author(s):

C. Liang ◽

H. H. Xing ◽

S. E. Cho ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Its Region ◽

The United States ◽

The Philippines ◽

Control Treatment ◽

Width Ratio ◽

Podosphaera Leucotricha ◽

Potential Threat ◽

Young Leaves ◽

Qingdao City

Photinia serrulata Franch. & Sav. (syn. P. serratifolia (Desf.) Kalkman), called Chinese photinia, is native to China, Taiwan, Japan, Indonesia, the Philippines, and India. The plants are evergreen shrubs to small trees belonging in the Rosaceae, and are widely cultivated throughout the world for ornamental purposes. Since 2005, severe powdery mildew infection has been observed on this plant in the Chengyang District of Qingdao City in Shandong Province, China. Powdery mildew colonies were circular to irregular white patches on both sides of the leaves and on young stems. As the disease progressed, white mycelial growth covered the entire shoot portion, causing leaf distortion. Voucher specimens (n= 7) were deposited in the herbarium of Qingdao Agricultural University, China. Hyphae were flexuous to straight, branched, septate, 4 to 6 μm wide, and had nipple-shaped appressoria. Conidiophores arising from the upper part of the hyphae were 110 to 185 × 9 to 12 μm and produced two to six immature conidia in chains with a crenate outline. Foot cells of conidiophores were straight, 30 to 40 μm long, and cylindric to somewhat attenuated toward the base. Conidia were hyaline, ellipsoid-ovoid, 22 to 32 × 13.5 to 20 μm (length/width ratio = 1.5 to 1.9), and had distinct fibrosin bodies. No chasmothecia were observed. The structures and measurements were compatible with those of the anamorphic state of Podosphaera leucotricha (Ellis & Everh.) E.S. Salmon as described by Braun (2). To confirm the identification, the complete internal transcribed spacer (ITS) region of the rDNA was amplified with nested PCR (4) and sequenced. The resulting sequence of 562 bp was deposited in GenBank (Accession No. JQ999954). A GenBank BLAST search of this sequence revealed 100% identity with that of seven isolates of P. leucotricha on rosaceous plants. Pathogenicity was confirmed through inoculation tests by gently pressing diseased leaves onto young leaves of three asymptomatic, potted 3-year-old photinia plants. Three non-inoculated plants were used for a control treatment. Plants were maintained in a greenhouse at 22 ± 2°C. Inoculated leaves developed symptoms after 5 days, whereas the control plants remained symptomless. The fungus present on the inoculated leaves was morphologically identical to that observed on the original diseased leaves, fulfilling Koch's postulates. The powdery mildew infections of P. serrulata associated with P. leucotricha have been recorded in New Zealand, Ukraine, Italy, and the United States (1,3). To our knowledge, P. leucotricha on P. serrulata has not been reported in Asia except for a record of a Podosphaera sp. on P. serratifolia in Japan (3). Since this ornamental shrub is native to China and nearby countries, occurrence of powdery mildew in China poses a potential threat to the health of photinia in other places. References: (1) E. Baldacci. Rev. Appl. Mycol. 16:358, 1937. (2) U. Braun. Beih. Nova Hedw. 89:1, 1987. (3) D. F. Farr and A. Y. Rossman. Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from , May 14, 2012. (4) Y. Matsuda et al. Phytopathology 95:1137, 2005.

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Tree selection by the broad-headed skink, Eumeces laticeps: size, holes, and cover

Amphibia-Reptilia ◽

10.1163/156853893x00480 ◽

1993 ◽

Vol 14 (3) ◽

pp. 285-294 ◽

Cited By ~ 8

Author(s):

William E. Cooper

Keyword(s):

Nearest Neighbor ◽

Nearest Neighbors ◽

Significant Preference ◽

Quercus Virginiana ◽

Large Size ◽

Live Oak ◽

Oak Trees ◽

Large Trees ◽

Eumeces Laticeps ◽

Limit Detection

AbstractBroad-headed skinks (Eumeces laticeps) are semiarboreallizards that are strongly associated with live oak trees (Quercus virginiana). Examination of the frequencies with which lizards occupied the largest of four nearest-neighbor trees and those having holes revealed a strong preference for large trees having holes. The presence of holes large enough for entry was a more important factor than tree size per se, as indicated by consistent occupation of smaller trees having holes when the largest of the four nearest neighbors lacked holes, although a significant preference for large size was demonstrated by the significantly greater than chance occupation of the largest of four nearest neighbor trees among those having holes. Large adults occupied significantly larger trees than did smaller adults, suggesting that larger individuals aggressively exclude smaller ones from preferred trees. Pairs consisting of an adult female and the male guarding her preferred trees surrounded by dense bushes, presumably because bushes limit detection and attack by predators and possibly because they harbor prey. Broad-headed skinks thus prefer large live oaks having holes and a fringe of dense cover.

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(168) Long-term Growth of Live Oak from Seed or Cutting

HortScience ◽

10.21273/hortsci.40.4.1000e ◽

2005 ◽

Vol 40 (4) ◽

pp. 1000E-1001

Author(s):

Yin-Tung Wang ◽

Genhua Niu

Keyword(s):

Growth Habit ◽

Production Systems ◽

Cross Sectional ◽

Single Tree ◽

Quercus Virginiana ◽

Live Oak ◽

Oak Trees ◽

Polypropylene Fabric ◽

Surrounding Soil

Live oak trees raised from acorns are highly non-uniform and many produce numerous undesirable rhizomic shoots. The objectives of this study were to 1) compare the growth rates between (Quercus virginiana Mill.) trees from seed and cutting in four production systems and 2) determine if trees from cuttings produce rhizomic shoots. Rhizomic shoot cuttings 25–30 cm long were taken from a single tree about 50 years old in late Aug. 1990, rooted, and planted in 2.6-L pots after 2 months. During the same week, acorns were collected from the same tree and germinated. All trees were planted into 13-L pots in July 1991 and then to a field in July 1992. Trees from both sources were planted either directly in the ground, in 36.6- or 45.7-cm-diameter polypropylene fabric bags buried in the ground, or in 13-L pots on the ground. Trunk circumference 10 cm above the soil line was roughly measured yearly between 1992 and 1999. Initially, trees from cuttings grew slightly slower than seedlings, having a smaller trunk circumference, diameter, and cross-sectional area. These differences diminished and all trees had similar circumferences after 1996. In 1992, trees in 36.6-cm bags and pots had more growth than trees in the ground. In 1993, trees in pots had better growth than those in the ground. After 1993, all trees had similar circumferences until the end of this study, probably due to roots extending beyond the bags and pots into the surrounding soil. About one-third of the seedling trees produced rhizomic shoots, whereas none of the trees from cuttings did. The rhizomic shoots of trees in pots were contained within the pot and none from the ground. Another significance of this research is that the cloned trees from cuttings were extremely uniform in growth habit and form.

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First Report of Diplodia quercivora Causing Shoot Dieback and Branch Cankers on Live Oak (Quercus virginiana) in the United States

Plant Disease ◽

10.1094/pdis-07-13-0736-pdn ◽

2014 ◽

Vol 98 (2) ◽

pp. 282-282 ◽

Cited By ~ 7

Author(s):

T. J. Dreaden ◽

A. W. Black ◽

S. Mullerin ◽

J. A. Smith

Keyword(s):

The United States ◽

Negative Control ◽

First Report ◽

Quercus Virginiana ◽

Fungal Isolates ◽

Live Oak ◽

Parking Lot ◽

Internal Necrosis ◽

Tissue Flaps ◽

Control Tree

In September 2010, live oak (Quercus virginiana Mill.) trees in an Alachua County, FL, shopping center parking lot were observed with shoot dieback and cankers on small branches. Isolations were made from canker margins by surface sterilizing tissue in 2.5% sodium hypochlorite and plating on potato dextrose agar (PDA) and incubating at 23°C. Fungi morphologically similar to Diplodia quercivora Linaldeddu & A.J.L. Phillips (mycelium initially velvety and white and later turning pale to dark olivaceous and grayish in reverse) were consistently isolated from symptomatic tissue (2). The two loci used by Linaldeddu et al. (2) in the description of D. quercivora were sequenced to identify a representative isolate (PL1345) as D. quercivora. The internal transcribed spacer (ITS) (GenBank Accession No. KF386635) and translation factor 1-alpha (EF-1α) (KF386636) regions were amplified and sequenced using primers ITS1F/ITS4 (3) and EF1-728F/EF1-986R (1). BLASTn searches of the two sequences resulted in 99% (467 of 469 and 257 of 259, respectively) homology with D. quercivora CBS 133852, confirming the fungal isolates' identity as D. quercivora. In October 2011, Koch's postulates were verified by inoculating, repeated twice, three Q. virginiana saplings (stem diameters, 12 to 14 mm; at inoculation sites approximately 50 mm above soil line) with isolate PL1345. Agar plugs (3 × 3 mm) taken from the margin of a 12-day-old culture on PDA were inserted into flaps in the stems made by a sterile blade with the mycelia facing the cambial tissue. One negative control tree was mock inoculated with a sterile PDA plug. All inoculation sites were sealed with Parafilm and maintained in a greenhouse (19 to 29°C). Trees were assessed for symptoms 90 days after inoculation. External bleeding was noted on all but one tree, and all flaps became necrotic. Pycnidia were observed on the outer surface of the flap on one inoculated tree. Negative controls showed no bleeding and their tissue flaps remained alive. Vertical length of phloem necrosis and percent of stem girdling were measured after removing the bark. Mean necrotic length and percent girdling for inoculated saplings were 48 mm (standard error [SE] = 10.6) and 26.6% (SE = 5.7) for the first inoculation and 46 mm (SE = 17) and 25% (SE = 5) for the second, respectively. Controls showed no internal necrosis and all produced healthy callus tissue at inoculation sites. Two of the pathogen-inoculated trees per inoculation were sampled and the pathogen was re-isolated from each. Recovered fungal isolates were confirmed as D. quercivora based on morphology and 100% ITS sequence homology to PL1345. D. quercivora was first described as causing shoot dieback and cankers on Q. canariensis in Tunisia and was found to be pathogenic to three additional Mediterranean oak species, Q. ilex, Q. pubescens, and Q. suber (2). To our knowledge, this is the first report of D. quercivora causing cankers on Q. virginiana and the first report of the fungus outside of Tunisia. Given the damage this pathogen has caused there, efforts to monitor the spread of this disease would seem warranted. More research is needed to assess the risk this pathogen poses to North American oaks, however. References: (1) I. Carbone et al. Mycologia 91:553, 1999. (2) B. T. Linaldeddu et al. Mycologia 105:1266, 2013. (3) T. J. White et al. PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990.

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Growth of Container-grown Trees Transplanted from the Field or Grow-bags

HortTechnology ◽

10.21273/horttech.2.3.415 ◽

1992 ◽

Vol 2 (3) ◽

pp. 415-417 ◽

Cited By ~ 1

Author(s):

Ken Tilt ◽

Charles Gilliam ◽

John Olive ◽

Emmett Carden

Keyword(s):

Sandy Loam ◽

Field Soil ◽

Fresh Weight ◽

Production Methods ◽

Quercus Virginiana ◽

Live Oak ◽

Oak Trees ◽

Loam Soil ◽

Second Year ◽

Field Production

Crape myrtle (Lagerstroe-mia L. × `Natchez'), live oak (Quercus virginiana Mill.), and Chinese pistachio (Pistacia chinensis Bunge) were planted into a sandy loam soil directly in the field or in grow-bags. Root and top growth were measured in March and July of the second year. Some of the trees were transplanted to 20-gal (76-liter) containers in March or July and grown for 3 months. Chinese pistachio developed a poor root system in field soil and was not ready for harvest in March or July. There was no difference in height, caliper, or top fresh weight for crape myrtle. Caliper and top fresh weight were similar for live oak trees. However, live oaks grown by traditional field production methods were taller than trees produced in grow-bags. With March transplanting, both crape myrtle and live oak trees from traditional field plantings were taller than trees transplanted from grow-bags 3 months after transplanting into containers. Tree top weight, caliper, and root ratings were similar for March-transplanted crape myrtle. Live oak trees transplanted from grow-bags had similar caliper and top weight but a higher root rating. July-transplanted crape myrtle trees had similar values for all variables 3 months later. All live oaks died when transplanted from traditional field plantings to containers in July. All live oaks grown in grow-bags survived transplanting.

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