Browsing by Author "Phipps, Patrick M."
Now showing 1 - 13 of 13
Results Per Page
Sort Options
- Barriers to Internet-Based Learning Systems in a Select Virginia Agricultural PopulationChappell, Glenn Franklin II (Virginia Tech, 2006-12-04)The purpose of this study was to identify the barriers Virginia agricultural producers encounter when using the Internet and their preferences when seeking information delivered via the Internet. The results are expected to provide Extension educators needed information about producer Internet use patterns and their preferences related to Internet-based learning systems. The survey population (N = 370) consisted of Virginia agricultural producers currently known to be using the Internet as identified by the county Agricultural Extension agents. Data were collected online via an interactive, encrypted Web site and analyzed with SAS/STAT software. The 186 usable producer responses indicated that they were predominately white (98.36%), males (82.87%) averaging 51 years of age with some college education. Their primary occupation was farm or ranch work (41.71%) with a gross value of agricultural sales of $100,000 - $249,999. Nearly 60% conducted Internet agricultural marketing activities; three quarters purchased agricultural supplies, 43.17% conduct non-agricultural Internet business, and 50% use dialup services to access the Internet. In total, 95.68% of the responding producers access the Internet at least once a week and 31.60% reported previous participation in Internet-based learning. Producers below 30 years of age considered their lack of experience/training to be less of a barrier than older producers. Time constraints associated with job responsibilities, isolation from other program participants, and their ability to learn at a distance were seen as greater barriers by males than females. Producers listing their primary occupation as other than farming saw time constraints associated with their job as a greater barrier than those retired but still farming. Producers with a high school education generally rated barriers associated with Internet-based learning as greater obstacles than those with advanced degrees. Following an exposure to an Internet-based learning experience, no differences were observed related to the producers' age, gender, primary occupation, and the operation's gross value of agricultural sales and the selected factors. Producers making agricultural Internet purchases, perceived their motivation to participate in Internet-base learning as less of a barrier than those that did not. Generally, as the producers' Internet use frequency increased, their perception of the barriers was reduced and those with previous Internet-based learning experience saw their ability to learn at a distance as less of a barrier than did those with no experience. A comparison of pre- and post-exposure data, revealed time constrains associated with job responsibilities, access to instructors/specialists, feedback/instructor contact, and the motivation to participate as the greatest barriers to Internet-base learning. Differences in pre- and post-exposure assessments confirm that producers' perception of the barriers were worse than actuality. Extension's Internet-based learning experiences should be accessible from a familiar Internet location. The learners' abilities and connectivity should be considered when developing systems to minimize barriers associated with these factors. Internet-based activities should be relevant to the learner. Experiences should be available in multiple formats including video, audio, print and combinations of the aforementioned. Learners should be afforded the opportunity to interact with the presenter/instructor via the most acceptable and timely means.
- Biology and Control of Pepper AnthracnoseMarvel, Josh K. (Virginia Tech, 2003-12-17)Anthracnose (caused by Colletotrichum capsici or C. gloeosporioides) of bell peppers (Capsicum annum) has become a serious problem in recent years on the Eastern Shore of Virginia. The purpose of this research was to characterize isolates of the fungus from the Eastern United States, to compare them with the type species from the American Type Culture Collection, and to evaluate fungicides for disease management. Two cultivars of pepper were inoculated with a conidial suspension, and held in a dew chamber. Lesions were counted and measured every 48 hours. The type species was either not pathogenic or only mildly virulent; most of the virulent isolates originated in areas of intensive pepper production. In addition to pathogenicity experiments and traditional morphology, the Biolog® system was used to compare the ability of fungi to utilize different carbohydrate combinations in 96-well plates. Plates were read at 96 and 168 hours. Analysis of data, by Ward's statistical method, could reliably distinguish field isolates if based on 15 or more replications, but species-level identification was inconsistent. Standard fungicides and new compounds were compared in a field test with four replications of treatments in a randomized complete block design. Fruits were harvested three times, weighed for yield, and the number of marketable and diseased fruit recorded. Aggressive isolates from green pepper were controlled by applications of maneb, or alternation of maneb and strobilurin fungicides.
- Characterization of Transgenic Peanuts Expressing Oxalate Oxidase for Governmental Approval of Their Release for Control of Sclerotinia BlightChriscoe, Shanna Marie (Virginia Tech, 2008-07-08)Sclerotinia minor Jagger is a fungal pathogen of cultivated peanut (Arachis hypogaea L.) that can cause crop losses in excess of 50%. Fungicides are not completely effective at controlling the disease and can cost up to $311 per hectare for three applications. The ability to produce oxalic acid is necessary for the pathogenicity of some Sclerotinia spp. With little to no naturally occurring resistance to Sclerotinia blight in Arachis spp., a biotechnological approach was used to confer resistance to the disease. Peanut plants were transformed with a gene from barley encoding oxalate oxidase, an enzyme that degrades oxalic acid. Transformed peanuts showed resistance to S. minor and increased yields under disease pressure compared to the parental lines. Before the resistant varieties can be marketed, they must be reviewed and approved by the governmental regulatory system. Responsibility for regulation of transgenic plants in the U.S. is shared among the U.S. Department of Agriculture (USDA) through the Animal and Plant Health Inspection Service (APHIS), the Food and Drug Administration (FDA), and the Environmental Protection Agency (EPA). These agencies require several different data sets including molecular characterization and field studies before each transformation event can be commercialized. This project was designed to characterize three different transformation events, N70, P39 and W171. Molecular characterization included determination of insertion number, copy number, intactness of the expression cassette and stable inheritance of the transgene. N70 was found to have two insertions and two copies while W171 had one insertion with one copy. The P39 event has two insertions and two or more copies. Each of the three events was stable over multiple generations. Phenotypic comparisons of each transgenic line to the parent cultivar were carried out in field studies. Characteristics such as oxalate oxidase expression, yield and quality, hay quality, disease occurrence, aflatoxin content and plant height were assessed. Transgenic peanuts showed few differences from the parent cultivar other than resistance to Sclerotinia blight and yield under disease pressure. Outcrossing studies were completed to determine the rate and distance of cross pollination. Outcrossing rates in N70, P39 and W171 were less than 2.5% and occurred up to 19 rows or 17.4 m from the nearest transgenic row. The molecular characterization and field performance of N70, P39 and W171 have been assembled into a document to petition APHIS for determination of non-regulated status.
- 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.
- Improving Nitrogen Management in Corn- Wheat-Soybean Rotations Using Site Specific Management in Eastern VirginiaPeng, Wei (Virginia Tech, 2001-09-21)Nitrogen (N) is a key nutrient input to crops and one of the major pollutants to the environment from agriculture in the United States. Recent developments in site-specific management (SSM) technology have the potential to reduce both N overapplication and underapplication and increase farmers' net returns. In Virginia, due to the high variability of within-field yield-limiting factors such as soil physical properties and fertility, the adoption of SSM is hindered by high gridsampling cost. Many Virginia corn-wheat-soybean farms have practiced generating yield maps using yield monitors for several years even though few variable applications based on yield maps were reported. It is unknown if the information generated by yield monitors under actual production situations can be used to direct N management for increased net returns in this area. The overall objective of the study is to analyze the economic and environmental impact of alternative management strategies for N in corn and wheat production based on site-specific information in eastern Virginia. Specifically, evaluations were made of three levels of site-specific information regarding crop N requirements combined with variable and uniform N application. The three levels of information are information about the yield potential of the predominant soil type within the field, information about yield potentials of all soils within the field (soil zones), information about yield potentials of smaller sub-field units which are aggregated into functional zones. Effects of information on expected net returns and net N (applied N that is not removed by the crop) were evaluated for corn-wheat-soybean fields in eastern Virginia. Ex post and ex ante evaluations of information were carried out. Historical weather data and farm-level yield data were used to generate yield sequences for individual fields. A Markov chain model was used to describe both temporal and spatial yield variation. Soil maps were used to divide a field into several soil management units. Cluster analysis was used to group subfield units into functional zones based on yield monitor data. Yield monitor data were used to evaluate ex post information and variable application values for 1995-1999, and ex ante information and variable application values for 1999. Ex post analysis results show that soil zone information increased N input but decreased net return, while functional zone information decreased N input and increased net returns. Variable application decreased N input compared with uniform application. Variable application based on soil zone information reduced net return due to cost of overapplication or underapplication. Variable application based on functional information increased net return. Ex ante results show that information on spatial variability was not able to increase farmers?net return due to the cost of variable N application and information. Variable rate application decreases N input relative to uniform application. However, imprecision in the spatial predictor makes the variable application unprofitable due to an imbalance between costs of under- and over-application of N. Sensitivity analysis showed that value of information was positive when temporal uncertainty was eliminated. The ex post results of this study suggest there is potential to improve efficiency of N use and farmers?net returns with site specific management techniques. The ex ante results suggest that site specific management improvements should be tested under conditions faced by farmers including imperfect information about temporal and spatial yield variability.
- Incidence and Management of Seed Transmission of Cylindrocladium Black Rot of Peanut in VirginiaGlenn, Deborah Lea (Virginia Tech, 2001-03-01)Seed transmission of Cylindrocladium parasiticum was investigated as a possible explanation for the higher-than-expected incidence of Cylindrocladium black rot (CBR) of peanut in fields fumigated with metam sodium. Sixty-three commercial seed lots from Virginia production fields were examined for the presence of seed with speckled testae, a symptom of seed infection by C. parasiticum. Speckled seed was present in conditioned seed lots in 1998, 1999, and 2000 at an average rate of 1%. Soon after pods were harvested, the fungus was recovered from speckled seed at high frequencies. During winter seed storage, pathogen survival remained high in seed stored at -13 and 4 C, but declined in some seed stored at 15 C and ambient temperatures. Speckled and normal seed with and without fungicide treatment was planted in steam-treated soil in the greenhouse and metam-treated field plots in 1999 and 2000. Speckled seed treated with captan + pentachloronitrobenzene (pcnb) + carboxin transmitted the pathogen to emerging plants in the greenhouse and field. Transmission levels depended on the amount of viable inoculum present in seed at the time of planting. In the field, yield losses were significant when 20% or more of the seed planted was speckled. The low incidence of speckled seed in commercial seed lots would not result in a loss of yield for growers, but may contribute to disease spread. Testing of additional seed treatment fungicides indicated that fludioxonil, tebuconazole, and thiram may offer the best protection against disease spread from seed transmission of C. parasiticum.
- The influence of meteorological events and cultural practices on sclerotinia crown and stem rot of alfalfa, caused by Sclerotinia trifoliorumReed, Karen L. (Virginia Tech, 1987-01-05)Sclerotinia crown and stem rot (SCSR), caused by Sclerotinia trifoliorum Eriks., causes serious spring losses in some fall=sown, no-tillage alfalfa fields. In microplots artificially infested with sclerotia, greatest numbers of apothecia were found during November and December. Temperature and rainfall had significant impact on apothecium development. A proposed prediction method for apothecium appearance considers monitoring mean soil temperature. For apothecium initiation to occur, it was necessary for sclerotia to be subjected to an estimated 17 days of temperature at or below 15 C before apothecium production occurred. Soil temperatures were usually below 10 C at the time of apothecium appearance. Greatest numbers of apothecia occurred between 5-10 C. Rainfall influenced the number of apothecia, with significant increases occurring early in the 1984-85 production period.
- Integrated Pest Management Peanut Scouting ManualLinker, H. M.; Jordan, David; Baiely, Jack; Herbert, D. Ames Jr.; Phipps, Patrick M.; Swann, Charles W. (Virginia Cooperative Extension, 2020)In the competitive global peanut market, you need to lower production costs. At the same time, you also need to keep pesticide residues in peanuts to a minimum; protect rivers, streams, and lakes from runoff; and prevent chemicals from leaching through the soil to groundwater. Using IPM to protect crops only from pests that are likely to cause economic losses is a good way to meet these goals
- Perennial Grass Based Crop Rotations in Virginia: Effects on Soil Quality, Disease Incidence, and Cotton and Peanut GrowthWeeks, James Michael Jr. (Virginia Tech, 2008-04-24)In 2003 eight peanut and cotton crop rotations were established in southeastern Virginia, 4 of which included 2 or 3 years of tall fescue or orchardgrass grown as high-value hay crops. Each crop rotation was evaluated for changes in soil quality indicators including soil carbon and nitrogen, water stable soil aggregates, plant available water content, bulk density, cone index values, and soil moisture. Cotton and peanut growth and yield were also observed to evaluate changes in crop growth associated with differences in soil quality. Soilborne plant pathogens including root-knot nematode, stubby root nematode, ring nematode, stunt nematode, and Cylindrocladium parasiticum microsclerotia were measured in the spring and fall of each year to determine differences associated with crop rotations. Water stable soil aggregates in 2007 were higher in rotations with 3 years of either perennial grass. Soil moisture tended to be the highest at depths 30 - 60 cm in the 3-year tall fescue rotation in August and September 2007. Cotton in 2006 and peanut in 2007 had higher growth and yield where the annual crop directly followed a perennial grass. Root-knot nematode tended to decrease in all rotations over time. Stubby root nematode populations tended to increase in rotations with either duration of orchardgrass. Including perennial grasses in cotton and peanut rotations has the potential to increase growth and yield as demonstrated in this research.
- Pest management guide for peanutsSmith, John C.; Phipps, Patrick M.; Rud, O. E. (Virginia Cooperative Extension Service, 1981-01)
- Pest management guide for soybeansMcPherson, Robert M.; Smith, John C.; Roberts, James E. Sr.; Phipps, Patrick M.; Rud, O. E.; Wilson, H. P.; Foy, Chester L. (Virginia Cooperative Extension Service, 1981-01)
- Reducing copper and chlorothalonil in staked tomato production on Virginia's Eastern ShoreGraves, Arthur S. (Virginia Tech, 2001-06-28)Virginia ranks third in fresh market staked tomato (Lycopersicon esculentum Mill.) production with approximately 1,659 hectares on the Eastern Shore. Estimated annual gross value is $30,800,000. Copper and chlorothalonil have long been considered essential to control bacterial and fungal diseases in fresh market tomatoes. High rates of these fungicides on tomatoes grown under plastic mulch have led to concerns about their potential adverse effect on water quality in estuaries adjacent to fields. The development of new fungicides, such as azoxystrobin and acibenzolar-S-methyl, which have more favorable environmental fate characteristics and are used at much lower rates, may provide viable alternatives to copper and chlorothalonil. Using a disease forecasting system, such as Tomcast, may reduce the number of applications of fungicides. The research objectives of this study were to reduce the amount of copper and chlorothalonil used in fresh market tomato production and to evaluate the effectiveness of the Tomcast disease forecasting system for controlling fungal leaf diseases on the Eastern Shore. Field studies compared copper to acibenzolar-S- methyl for bacterial diseases caused by Xanthomonas campestris pv. vesicatoria and Pseudomonas syringae pv. tomato. Research plots were established in a randomized complete block design with four replications in grower fields and at the Eastern Shore Agricultural Research & Extension Center. Acibenzolar proved to be as effective as the standard copper bactericides in controlling bacterial spot. Acibenzolar provided better control than the standard copper bactericides when bacterial speck was the target disease. Azoxystrobin application alternated with maneb was evaluated as a replacement for chlorothalonil. Azoxystrobin and Tomcast were studied as tools to reduce chlorothalonil use for control of Alternaria solani. Tomcast can reduce the number of applications by 40-70 % per year and provide adequate control of early blight. Azoxystrobin provides better control of early blight than chlorothalonil. Use of these new, more environmentally compatible, plant-protection products , along with the Tomcast disease forecasting system, can significantly reduce or eliminate the need to use copper and chlorothalonil for tomato disease management and therefore eliminate them as potential pollutants of the Chesapeake Bay and Atlantic Ocean estuaries.
- The Role of Host, Environment, and Fungicide Use Patterns in Algorithms for Improving Control of Sclerotinia Blight of PeanutLangston, David B. (Virginia Tech, 1998-04-09)An algorithm was developed for assessing disease risk and improving fungicide timing for control of Sclerotinia blight of peanut, caused by Sclerotinia minor. A 5-day index (FDI) of disease risk was calculated daily by multiplying indices of moisture, soil temperature, vine growth and canopy density and summing the values for the previous 5 days. Spray thresholds of FDI 16, 24, 32, 40, 48 were compared to a 60, 90, 120 DAP (days after planting) schedule and the standard demand program. Field trials in 1994 indicated that fluazinam (0.58 kg a.i./ha) applied at an FDI of 32 performed similarly to the demand program and was more efficient than the DAP schedule. However, the original FDI 32 algorithm triggered sprays 13 days subsequent to disease onset in 1995, indicating the need for improved vine growth and temperature parameters as well as DAP-dependent FDI thresholds. Results from 1996 and 1997 demonstrated that algorithms with new vine growth and temperature parameters coupled with DAP-dependent thresholds performed as well or better than the original FDI 32 algorithm, demand program, or DAP schedule. Protection intervals of 7 and 14 days improved the performance of iprodione (1.12 kg a.i./ha) while fluazinam provided protection for up to 21 days when applied according to the original FDI 32 algorithm. Planting date was evaluated for its effect on disease and fungicide use patterns. Late planting (20-28 May) delayed disease onset and reduced early season disease incidence three of the four years tested. When averaged across planting dates, the original FDI 32 algorithm performed as well or better than the demand program in 1994 and 1995, as did algorithms utilizing new vine growth and temperature parameters with DAP-dependent thresholds in 1996 and 1997. Chemicals for altering plant architecture were compared to defoliation by corn earworm and leaf spot for suppression of Sclerotinia blight. Chlorimuron (8.8 g a.i./ha) and withholding fungicide for leaf spot control demonstrated the most significant disease suppression and yield improvement. Results show the importance of fungicide timing and plant growth and canopy architecture modification for control of Sclerotinia blight of peanut.