Browsing by Author "Stipes, R. Jay"
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- 1976 Virginia plant disease control guideCouch, Houston B.; Drake, Charles R.; Hickey, K. D.; Lambe, Robert C.; Osborne, W. Wyatt; Pristou, Robert; Skelly, John M.; Stipes, R. Jay; Baldwin, Robert E. (Virginia Cooperative Extension Service, 1976-01)Guide is intended to serve as a ready reference to disease control measures for extension agents, growers, custom spray applicators, processors, chemical company representatives, and dealers in Virginia
- Abiotic stressors in the dogwood anthracnose complexCrozier, James Brooks (Virginia Tech, 1994-03-15)Acidic precipitation reportedly enhances disease severity of dogwood anthracnose (DA) caused by Discula destructiva, on Cornus florida, the flowering dogwood. Seedlings were subjected to acidic fog episodes at pHs 2.5, 3.5, 4.5, and 5.5, using a simulated acidic rain solution. Leaf discs from these and non-treated plants were examined by scanning electron microscopy (SEM). Damage was noted at all pH levels. Discula destructiva conidia may germinate at trichome bases where damage may cause the leaching of nutrients. Also, the difference in stomatal damage may account, in part, for differences in disease susceptibility. Cardinal growth temperatures and response to thermal stress regimes were determined for isolates of Discula destructiva. This information may lead to an understanding of possible climatic barriers, and the thermal treatment of plant material.
- Anthracnose: A Fungal Disease of Shade TreesStipes, R. Jay; Hansen, Mary Ann (Virginia Cooperative Extension, 2009-05-01)This publication covers the symptoms, disease cycle, and control of Anthracnose, a fungal disease of shade trees.
- Biological studies of shiitake logs and associated mycoflora in the Virginia highlandsGuevara-Guerrero, Gonzalo (Virginia Tech, 1991-12-05)Shiitake growers in Virginia are experiencing considerable diminution of the fruiting life of oak logs, due primarily to Ascomycetous, competing, wood-rotting, contaminating "weed fungi" that either invade the logs after trees are felled or are present in tree tissues before felling. We surveyed several shiitake farms, and, although the fungal flora differed among them, the predominant colonizing fungi were identified as Graphostroma platystoma (also identified as Diatrype stygma), Eutypa spinosa and Slereum aff. complicatum. Other less frequently observed fungi were Stereum ostrea, Schizophyllum commune, Hymenochaete sp., Poria sp., Hypoxylon atropunctatum and Hypoxylon punctulatum. Site and means of invasion (colonization) of these "weed fungi" were studied by monitoring endophytic fungal populations in stressed and non-stressed oak trees in the Jefferson National Forest Montgomery County, Virginia. Twenty-six samples from Poverty Creek (non-stressed) and 23 from Brush Mountain (stressed) were studied. Fifty percent of the samples from the non-stressed were sterile, 23% yielded Paecilomyces variota., and 27% were colonized by other fungi. On the other hand, 100% of the samples from stressed trees (Brush Mountain) were colonized by fungi; 74% yielded P. variotii and 26% by other fungi. Thirty samples from a pin oak (Quercus paluslris) plot at Virginia Tech (non-stressed) were 74% sterile, 16% colonized by an unidentified yeast, and 10% colonized by other unknown fungi.
- Biology of virulent and hypovirulent Endothia parasitica on American chestnut (Castanea dentata)Hebard, Frederick Vanuxem (Virginia Polytechnic Institute and State University, 1982)Results of inoculations of grafts, seedlings, excised stems, and intact trees of large, surviving American chestnut indicated that some have heritable blight resistance. Some degree of resistance in American chestnut possibly would assist spread of hypovirulence (H) factors. The pathogenicity of the H isolate but not the V (virulent) isolate appeared to influence the size and sporulating characteristics of biocontrolled H+V cankers. The histopathology of canker development on blight-resistant Chinese and blight-resistant and blight-susceptible American chestnut was examined after inoculation with V and H E-parasitica. Rapid formation and continual growth of mycelial fans distinguished chestnut blight cankers incited by V E-parasitica from those incited by H E-parasitica, and distinguished cankers on susceptible chestnut from cankers on resistant chestnut. Differences among such cankers in wound periderm and other pathological alterations of bark and wood anatomy probably were results of differences in rates of fan formation and growth. Wound periderm formation began at the deepest point of a wound or canker and progressed outward to the bark surface. Superficial cankers arose in resistant trees or with hypovirulent fungus when slow-forming mycelial fans expanded through areas where wound periderm had not formed. Rapid epidemics of chestnut blight occur in recently clearcut areas but not in areas with large trees of species other than American chestnut, most probably because chestnut sprouts released after cutting become larger than they do when overtopped by large forest trees. The size of chestnut sprouts appeared to influence the rate of blight progress by setting a maximum limit on canker size and thus canker sporulation. It may be possible to foster spread of H factors in the Appalachians if blight epidemics in clearcuts can be prolonged. This might be done by restricting inoculum production. Cutting and removing some blighted sprouts, cutting some large unblighted sprouts, or increasing blight resistance in the chestnut population are three potential means of restricting inoculum production.
- Bipolaris zeicola: physiological races, morphology and resistance on maizeTraut, Eduardo Jorge (Virginia Tech, 1993)Conidial length, width, septation, curvature and pigmentation of 39 isolates of Bipolaris zeicola (Stout) Shoemaker from different geographical areas and representing distinct physiological races were examined. Wide variability in conidial morphology was found among isolates of each race. No association was found between races or groups of isolates producing the same shape of lesions and conidial morphology. Morphology and expansion of lesions induced by three races of B. zeicola producing different shapes of lesion on susceptible maize (Zea mays L.) inbred lines were studied. Resistant type lesions induced by three races of B. zeicola were indistinguishable based on their shape or size. However, lesion size correlated with the lesion type induced by each race, indicating that it may be useful to evaluate resistance to different races of B. zeicola. Inheritance of reaction to one isolate of the proposed pathotype of B. zeicola was studied. Resistance was controlled by a single dominant gene in the cross Pr x B37. Forty-nine isolates of B. zeicola from different geographical areas including all the previously described races and pathotype were characterized by their disease reaction, severity and symptoms incited on 14 maize inbred lines. Eleven physiological races were distinguished based on their differential reaction on the 14 inbred lines; however, 6 inbred lines were adequate to differentiate the races. A system based on binary notation is proposed to designate races of B. zeicola on maize. Two races induced typical symptoms of Helminthosporium carbonum-toxin (HC-toxin) production on Pr. Seven races produced oval to irregular lesions on susceptible hosts and did not produce typical lesions of HC-toxin production on Pr. One race induced predominantly long, linear lesions, and another was avirulent on all 14 maize inbred lines.
- Chemical interactions between rainfall and northern red oak (Quercus rubra l.) foliageLeininger, Theodor Daniel (Virginia Polytechnic Institute and State University, 1988)Nutrient ion exchange was examined between simulated acid rain solutions and northern red oak (Ouercus rubra L.) leaves of trees growing in fertile, limestone-derived soil and less fertile, sandstone/shale-derived soil. Leaves harvested from trees growing on the fertile site had greater concentrations of total N, P, K, Ca, and Mn but less total Mg than leaves of trees on the less fertile site. Cation losses from leaves of both sites were similar when exposed T3 to simulated rain solutions of pH 5.6, 4.3, and 3.0. Simulated rain solutions of pH 3.0 leached the greatest amount of total cations from leaves of both sites. Differences in acidity between leachates and starting rain solutions increased as the acidity of starting solutions contacting leaves of either site increased. Differences in leaf nutrient status between sites typically did not affect leachate acidity. Hydrogen ion exchange, believed to be the main mechanism of cation loss from leaves of both sites, accounted for 30 to 44% of all cations leached from leaves of both sites. Concentrations of inorganic ions were measured in bulk rainfall and bulk throughfall collected beneath northern red oak trees growing on the fertile and less fertile sites. Rainfall passing through crowns at both sites was enriched with S0₄²⁻, P0₄³⁻, Ca²⁺, Mg²⁺, K⁺, Mn²⁺, and Fe²⁺, but lost NH₄⁺ to the crowns. There was little difference in the inorganic chemistry of incident rainfall between sites. Large-particle dryfall ionic concentrations, rainfall volume, and leaf area were all larger at the fertile than at the less fertile site. Higher concentrations of Ca²⁺, Mg²⁺, NH₄⁺, Mn²⁺, and S0₄²⁻in throughfall at the fertile site compared to that of the less fertile site are likely due to the combination of these three factors. Historical northern red oak crown areas were estimated for the fertile and less fertile sites by a two step procedure using annual growth ring chronologies and published regression equations. These equations related total crown area to total crown dry weight. The usefulness of crown area estimates in throughfall studies was demonstrated by applying nutrient ion exchange data, collected beneath northern red oak crowns in 1984, to 1982 and 1930 crown area estimates. Smaller nutrient ion exchange estimates in 1930 were due to smaller crown area estimates.
- The chemotaxonomy of the fungal genus Endothia fr.Micales, Jessie Ann Daubert (Virginia Polytechnic Institute and State University, 1985)The taxonomic status of the fungal genus Endothia was recently changed in a controversial monograph by Barr (Barr, M. E. 1978. The Diaporthales of North America. Mycol. Mem. 7. J. C. Cramer. 232 p.), who divided the genus into two separate genera, Endothia and Cryphonectria, based on differences in ascospore shape and septation, stromatic configuration and distribution of stromatic tissues. This group of fungi traditionally contains some important plant pathogens; its taxonomic position needs to be resolved. The morphological criteria used by Barr were reinvestigated. Polyacrylamide gel electrophoresis and fungicide sensitivity assays were also used to examine biochemical relationships among the organisms and to establish additional means of distinguishing among the closely related taxa. The morphological features of 12 species of Endothia were examined. Those species with 2-celled, ovoid ascospores produced valsoid stromata, while organisms associated with nonseptate, allantoid ascospores formed diatrypoid stromata. Pseudoparenchymatous tissue was observed along the edge of the stroma, while prosenchyma was confined to the stromatic center. The major criteria used by Barr were confirmed. Polyacrylamide gel electrophoresis was used to separate the buffer-soluble proteins of 78 isolates, representing 13 species of Endothia and Cryphonectria cubensis. Intraspecific variation of banding patterns was less than interspecific differences; the species were separated by this technique. The banding patterns of E. eugeniae isolates closely resembled those of C. cubensis: these organisms may be conspecific. Hypovirulent isolates of E. parasitica could not be distinguished from wild isolates. The banding patterns of specific isozymes were species specific; the use of isozyme analysis has great potential for future taxonomic and genetic studies. The sensitivities of E. parasitica and E. gyrosa were determined for 23 different fungitoxicants. The two species were differentially sensitive to cycloheximide, with ED₅₀ values of 0.01-0.03μg/ml and 1.0-2.0 μg/ml for E. gyros and E. parasitica respectively. Differential sensitivities were not exhibited toward the remaining fungitoxicants; these fungi probably share many biochemical processes and response mechanisms. Barr’s classification system is technically correct and it seems to organize relationships within the entire order in a uniform manner. Its adoption is recommended with some hesitation since the influence of host on stromal development is not fully understood.
- Commercial recommendations for disease, insect, and weed control on shade trees and shrubsStipes, R. Jay (Virginia Cooperative Extension Service, 1978-01)
- Comparative physiology of radish populations with differential sensitivity to O₃ and SO₂Gillespie, Chris Todd (Virginia Polytechnic Institute and State University, 1989)Radish plants (Raphanus sativus L. cv Cherry Belle) were exposed to 0.10 μl l⁻¹ ozone (O₃) or 0.50 μl l⁻¹ sulfur dioxide (SO2) for 4 h d⁻¹, 3 d wk⁻¹ for 3 weeks. From these fumigated plants, individuals were selected that were resistant or sensitive to these pollutants. The selected plants were used as parental material in a breeding program to produce lines differing in resistance to O₃ and SO₂. Non-selected (NS) plants from the original populations served as controls. F₁ populations were raised and exposed to O₃ or SO₂ with the same fumigation regime used for the parents. The plants were harvested 30 days after emergence and dry weights were determined. Plants selected for O₃ resistance (O3R) weighed significantly more than either plants selected for sensitivity to O₃ (O₃S) or NS plants when exposed to either O₃ or SO₂. The hypocotyl was most affected by pollutant exposure, leading to reduced root/shoot ratios. Plants selected for resistance or sensitivity to SO₂ generally had biomass production similar to that of NS plants. Growth analysis at early stages of growth indicated that both O₃R and O₃S plants had less growth under O₃ fumigated conditions; however, by maturity O₃R plants had similar amounts of growth under fumigated or non-fumigated conditions. Ozone fumigations tended to decrease free sugar concentrations in leaves at early stages of growth in both O₃R and O₃S plants, and caused some accumulations of carbohydrates during late stages of growth in O₃S plants. Allocation of Mc was significantly lower to hypocotyls and roots of O₃ fumigated O₃S plants. Allocation to hypocotyls of O₃R plants was not affected, although both O₃R and O₃S plant groups had lower photosynthetic rates due to O₃ fumigation. Ozone did not significantly affect chlorophyll concentrations in leaves of either sensitive or resistant plants, nor was the time of new leaf production affected by fumigation. These experiments demonstrated the potential of O₃ to influence the composition of sensitive plant populations. However, SO₂ was a much less powerful influence on the composition of these populations.
- Creeping bentgrass response to plant growth regulating substances and annual bluegrass competitionBigelow, Cale A. (Virginia Tech, 1995-05-05)Creeping Bentgrass (Agrostis stolonifera var. palustris (Huds.) Farw.) is the most widely used cool-season turf grass used for putting greens in North America. Frequently it becomes invaded with a persistent weed, annual bluegrass (Poa annua L.). Studies were conducted on a predominately annual bluegrass area managed as a putting green to attempt to quantify the impacts of plant growth regulator, seeding rate" and season on the success of introducing creeping bentgrass. Also, the impact of plant growth regulating substances on creeping bentgrass overall quality and seasonal rootmass production was evaluated. It was observed that creeping bentgrass does not become well established when overseeded into annual bluegrass regardless of plant growth regulator applications or season. Additionally 1I plant growth regulator application, following seedling emergence reduced creeping bentgrass seedling populations. Competition from established annual bluegrass and close frequent cutting were deemed reasons for lack of creeping bentgrass establishment success. Creeping bentgrass turf was maintained at a high level of quality with plant growth regulating substances. The use of the plant growth regulator trinexapac-ethyI reduced clipping production and was not detrimental to root production. Propiconizole application increased clippings and controlled Sclerotinia dollarspot. The application of a proprietary biostimulator material (3D) enhanced creeping bentgrass green color and generally increased rootmass over untreated turf.
- Cultural characteristics, vegetative compatibility, and spatial pattern of white hypovirulent strains of Cryphonectria parasitica on grafted American chestnut treesHogan, Eric P. (Virginia Tech, 2001-02-19)In 1982-1983, naturally formed blight cankers, within a zone ranging from the ground to 183 cm on three grafted American chestnut trees, were inoculated with a mixture of four European (white), and six, pigmented hypovirulent strains of Cryphonectria parasitica. A total of 202 C. parasitica isolates were recovered from 49 cankers located outside of the inoculated zone. Ninety-five isolates (47%) were white and 107 (53%) were pigmented. Forty-eight vegetative compatibility groups were identified among 110 white isolates collected from this and previous studies. The ratio of VC groups to isolates tested (S/N), and Shannon diversity index were calculated to be 0.43 and 3.64 respectively. Of the 48 VC groups identified, 25 consisted of two or more isolates. These 25 groups were found to be vegetatively incompatible with all four of the original hypovirulent white inoculated strains, consisting of three VC groups, but were compatible with five of the 11 most common pigmented VC groups recovered from previous studies. These data provide evidence for spread of the original European hypoviruses (Cryphonectria hypovirus 1, CHV1) but not for spread of the original inoculated strains. Forty-five VC groups therefore represent the minimum number of "new" VC groups into which one or more of the original hypoviruses (CHV1) have spread. Single-spore colonies of the white isolates recovered from the 49 cankers were placed into four cultural morphology (CM) groups based on degree and pattern of pigmentation, and type of colony margin in culture. The two largest CM groups contained 37 (CM group 3) and 33 (CM group 1) isolates. Single-spore colonies from the original, white inoculated strain, EP-49, were classified to CM groups 3 and 1, while colonies of EP-51W were classified into CM group 1. The spatial pattern of white isolates within cankers was evaluated using a 7 x 7 lattice plot. Spatial pattern determination using the join-count statistics, described by Pielou, indicated that three of the four cankers containing white isolates had random patterns of white isolates. Vegetative compatibility tests of C. parasitica isolates in the two cankers sampled for spatial pattern indicated that the majority of both white and pigmented isolates in the cankers were within the same VC group for each canker. This was frequently the case even when pigmented and white isolates occurred in adjacent lattice cells. Isolates in each of the cankers identified to VC group had random patterns of the major VC groups (includes pigmented and white isolates). Using a double matrix statistical test, the spatial pattern of white VC groups among the 49 cankers was found to be aggregated (P=0.019), whereas the spatial pattern of white isolates was found to be random (P=0.325). The Lloyd's index of patchiness value for the pattern of white isolates in all cankers was 0.91. This value is just less than 1.0, which would indicate a random pattern.
- Development and evaluation of a computerized leafspot advisory program for effective use of cultivar resistance, fungicide, and spray adjuvant to control early leafspot of peanutCu, Ramon M. (Virginia Tech, 1991-04-15)An advisory program to determine the timing of fungicide application for control of early leafspot of peanut, caused by Cercospora arachidicola, was developed based on growth responses of the pathogen to specific environmental conditions. The advisory program (89-ADV) assigned time-duration values to conditions conducive for infection (TDVi). Cumulative TDVi levels were used to determine when fungicide applications were needed. Various spray thresholds (TDVi=48, 72, 96, 120) of the 89-ADV program were compared to a 14-day spray schedule and an advisory program that was released to growers in 1981 (81-ADV). Leafspot incidence, area under the disease progress curve (AUDPC), spray number, yield and value were used to evaluate the performance of spray programs. Preliminary trials used Florigiant peanut and the fungicide chlorothalonil (1.26 kg/ha). The 89-ADV program with TDVi=48 performed exceptionally well for three consecutive years in field tests and in simulated disease environments reconstructed from historical weather data. Benefits of this program compared to the 81-ADV program included significant improvement of leafspot control, and improved crop yield and value. Based on performance, the 89-ADV program was delivered to growers as the on-line peanut leafspot advisory in 1989. Subsequent evaluations of the 89-ADV program included cultivars and fungicides in large multi-factorial experiments. Three classes of cultivars were identified: class I or highly susceptible, Florigiant and NC 9; class II or moderately susceptible, NC 7 and NC-V11; and class III or moderately resistant, NC 6. The efficiency of fungicide sprays was improved through effective leafspot control with about three fewer sprays per season than the 14-day spray schedule when chlorothalonil at 1.26 kg/ha, diniconazole at 140 g/ha or terbutrazole at 126 g/ha was applied on class I cultivars according to the TDVi=48 threshold of the 89-ADV program. The same efficiency was achieved when chlorothalonil or terbutrazole was applied on class II cultivars according to the TDVi=96. Cupric hydroxide at 1.79 kg/ha plus sulfur at 1.04 kg/ha or terbutrazole at 126 kg/ha with TDVi=96 as well as chlorothalonil at 1.26 kg/ha with TDVi=120 resulted in efficient control of disease on the class III cultivar. The spray adjuvant SoyOil 937® at 0.5% of spray volume consistently improved the performance of chlorothalonil, and allowed a reduction of application rate from 1.26 to 0.95 kg/ha without sacrificing disease control. The integrated use of cultivar resistance, fungicide, spray adjuvant, and TDVi thresholds of the 89-ADV program contributed to a reduction of fungicide input and improved disease control.
- Differentiation of Endothia gyrosa and Endothia Parasitica by Disc Electrophoresis of Intramycelial Enzymes and ProteinsStipes, R. Jay; Emert, George H.; Brown, Ross D. (Mycological Society of America, 1982)Mycelial proteins from seven isolates of Endothia gyrosa and five isolates of E. parasitica were extracted from acetone powders, separated on polyacrylamide gels by disc electrophoresis, and then stained for general proteins, esterase activity or 3-glucosidase activity. By simple visual inspection, three different observers separated the twelve uncoded general protein gels into the two species. The enzyme gels of both species were more easily differentiated. Very little or no/3-D-glucosidase and general esterase activities were noted on E. parasitica gels. Although the extract sample load (about 220 /xg protein) was standardized, qualitative and quantitative intraspecific variations were noted; these did not interfere with species differentiation. Protein and enzyme profiles from a 30-yr-old isolate of E. gyrosa compared favorably with new isolates. These data corroborate the separation of the species on the basis of morphology.
- Disease, insect, and weed control recommendations for commercial production and maintenance of trees and shrubsStipes, R. Jay; Weidhaas, John A., Jr.; Coartney, James S. (Virginia Cooperative Extension Service, 1977-01)
- Diseases of landscape trees : Dutch elm disease and its control in VirginiaStipes, R. Jay; Weidhaas, J. A. (John A.) (Virginia Cooperative Extension Service, 1971-01)Dutch elm disease is the most devastating and economically important shade tree disease in the United States.
- Diseases of shade tree: fusarium wilt of mimosaStipes, R. Jay (Virginia Cooperative Extension Service, 1975-04)Symptoms of fusarium wilt of Mimosas. Disease cycle and control
- Diseases of shade trees: cultural control of shade tree diseasesStipes, R. Jay; Beecher, Albert S. (Virginia Cooperative Extension Service, 1975)Diseases of shade trees including leaf scorch, winter and low temperature injuries, sunscald, mechanical injuries, dieback, and nutrient deficiencies
- Diseases of shade trees: verticillium wilt of shade treesStipes, R. Jay (Virginia Cooperative Extension Service, 1975-06)List of susceptible trees, disease process and control of verticillium wilt
- Ecological and taxonomic studies of the Russulaceae and other ectomycorrhizal Basidiomycetes in the high-elevation forests of the southern AppalachiansBills, Gerald F. (Virginia Polytechnic Institute and State University, 1985)Temperate and boreal fungal floras indicate that species of the Russulaceae (the genera Russula andLactarius) are among the dominant ectomycorrhizal fungi in forest communities. The contribution of the Russulaceae to the communities of ectomycorrhizal Basidiomycetes fruiting in red spruce and adjacent northern hardwood forests in West Virginia was evaluated and compared with other ectomycorrhizal Basidiomycetes occupying the same habitats. The Russulaceae exhibited the greatest species diversity of any family of ectomycorrhizal fungi fruiting in the stands studied (44% of the species in spruce, 39% of the species in hardwoods). Species of Lactarius and Russula were among the most productive in both forests. Species diversity, productivity, and fruiting phenology of all ectomycorrhizal Basidiomycetes were compared between red spruce and northern hardwood stands for a 3-year period. Sporocarp numbers and sporocarp frequency in 384 four m² quadrats in each forest type was used to estimate productivity. Species richness was greater in hardwoods (36 species) than in spruce (27 species). Nine species were common to both forests. Most productivity was concentrated in a few species, while most species were rare. Species-area curves were constructed for both forests. Fungal species and tree species composition in both forests were compared by principal component analysis. Fungi in spruce forests were more productive than in hardwood forests. Productivity was highly variable among the three seasons studied because of climatic variability. Sporocarp abundance and frequency were positively correlated with basal area and density of mycorrhizal trees and were negatively correlated with fern cover in hardwood forests. Fruiting seasons extended from early July to late September or early October. Numbers of species fruiting from the same four m² quadrats ranged from 0 to 7 in spruce forests and 0 to 5 in hardwood forests. Spatial patterns of sporocarps of major species were characterized by the variance-to-mean ratio, mean crowding, patchiness, and spatial autocorrelation and were found to exhibit highly aggregated, contagious patterns. Interspecific associations between pairs of major species were measured by 2 x 2 contingency tables and Cole's index of association. A taxonomie and geographic survey of Russula and Lactarius in both the quantitative study areas and in similar habitats in the Southern Appalachians was presented.
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