Powdery mildew is a serious disease of pumpkin throughout the Northeastern United States. Control... more Powdery mildew is a serious disease of pumpkin throughout the Northeastern United States. Control of pumpkin powdery mildew is currently achieved through the use of a calendar-based application of fungicides. Three non-pumpkin weather-based fungicide scheduling programs for powdery mildew were evaluated to determine their usefulness in the control of cucurbit
69th Annual Pacific Northwest Insect Management Conference, held January 11th and 12th, 2010 at t... more 69th Annual Pacific Northwest Insect Management Conference, held January 11th and 12th, 2010 at the Hilton Hotel, Portland, Oregon.
In 2019, a national survey of 252 members of the United States grape industry from 20 states asse... more In 2019, a national survey of 252 members of the United States grape industry from 20 states assessed knowledge perception of fungicide resistance management, application of that knowledge to vineyard practices, and knowledge acquisition sources. Overall, respondents demonstrated clear understanding of resistance management practices. The specific distribution of responses was influenced by the respondent's job role, duration of industry experience, and their farming operation size. Nationally, respondents were moderately familiar with the acronym FRAC (Fungicide Resistance Action Committee), with nearly 75% indicating they could identify the FRAC code of a fungicide. They felt moderately competent they could design a fungicide program that adhered to resistance management principles. Respondents identified fungicide resistance as a serious problem nationally, and as a moderate problem in their own vineyards. They ranked practices that include rotating fungicides of different FRAC codes, avoiding multiple sequential applications of the same trade name or FRAC code, tank mixing with different FRAC codes, using multisite products in a spray program, routine sprayer maintenance and calibration, and good canopy management as very-to-extremely important in managing fungicide resistance; whereas practices such as rotating between trade names and tank mixing different trade names ranked slightly important. Respondents identified university-based extension programs as the primary information resource for fungicide efficacy and fungicide stewardship (resistance management). To maximize potential effect, these results suggest that future educational efforts should be aimed at improving practices for fungicide resistance stewardship and should align with the knowledgebase and demographic factors of the target audience-particularly their job role, experience, and size of operation.
Grape powdery mildew epidemics, caused by Erysiphe necator, are initiated by the release and subs... more Grape powdery mildew epidemics, caused by Erysiphe necator, are initiated by the release and subsequent germination of ascospores from mature chasmothecia. Interrupting the development of chasmothecia prior to overwintering may reduce or prevent the overwintering of E. necator in vineyards, thereby reducing initial disease incidence observed the following growing season. At the end of the grape growing season in 2014 and 2015, one application of Organic JMS Stylet Oil (Vero Beach, FL) at a rate of 10 ml/liter was applied on four treatment dates using an air-assisted backpack sprayer onto Chardonnay grapevines within a vineyard. Leaves were collected weekly and chasmothecia enumerated from the first observation of chasmothecia primordia development until the onset of rains (approximately 5 weeks). In 2014, all stylet oil treatment plots developed significantly fewer chasmothecia than nontreated control plots in 2014 (P = 0.04), and there were no differences in treatment date observed...
Grape powdery mildew (GPM) fungicide programs consist of 5 to 15 applications, depending on regio... more Grape powdery mildew (GPM) fungicide programs consist of 5 to 15 applications, depending on region or market, in an attempt to achieve the high fruit quality standards demanded by the market. Understanding how fungicides redistribute and targeting redistributing fungicide to critical crop phenological stages could improve fungicide protection of grape clusters. This study evaluated fungicide redistribution in grapevines from major fungicide groups labeled for GPM control. Translaminar and xylem redistribution was examined by placing fungicide-impregnated filter disks on the adaxial or abaxial leaf surface of detached leaves for 10 min and then incubating for 48 h before inoculating the abaxial surface with conidia. Vapor redistribution used Teflon disks sprayed with fungicides and placed on the abaxial leaf surface of detached leaves 48 h before inoculation. Disease development was rated 10 days later. Translaminar movement through calyptra was tested using flowering potted vines. A...
ABSTRACTPowdery mildew is the most important disease of grapevines worldwide. Despite the potenti... more ABSTRACTPowdery mildew is the most important disease of grapevines worldwide. Despite the potential for rapid spread by the causal pathogen, grape powdery mildew has been effectively managed using fungicide applications applied based on a calendar schedule or modeled disease risk index. Various epidemiological models for predicting disease development or risk have helped to improve disease management. The Gubler-Thomas (GT) risk index is a popular disease risk model used by many growers in the western U.S. We modified the GT risk index using fuzzy logic to address both biological and mechanical uncertainty in the pathosystem. The spraying schedule suggested by the fuzzy-modified GT risk index was tested in eight site-years. Overall, the fuzzy-modified risk index maintained comparable levels of disease control as both the original model and a calendar based treatment, and had significantly less disease than the untreated control. The fungicide use efficiency of the fuzzy-modified GT ...
Agricultural systems are exposed to and influenced by particles of many types (e.g., pathogens, p... more Agricultural systems are exposed to and influenced by particles of many types (e.g., pathogens, pollen, pests), the concentrations of which are typically highest in the regions immediately surrounding their sources. The intermittent nature of trellised canopies creates an unique canopy architecture that directly affects the shape of particulate plumes and tends to alter their transport patterns in the near-source region. To investigate the behavior of particle plumes near their sources in a trellised canopy, a set of particle release experiments was conducted during a field campaign in an Oregon vineyard in 2013. Specifically, plumes of inert fluorescent microspheres (10-45 μm diameter) were released into the canopy during periods when the mean wind direction was significantly different from the vine-row direction. Plume concentrations were collected at over 100 separate locations in a three-dimensional space < 10 canopy heights downwind of the source during each release period. These plumes were more complex than those released during periods of row-aligned winds. A novel analysis approach using the superposition of two orthogonal Gaussian plume equations was developed to quantitatively assess the behavior of the plumes' shape and its dependence on wind direction and magnitude and on particle release height. Basic plume shape parameters, as determined by integrating the superposed Gaussian equation, varied significantly as a function of the mean wind direction. As the wind direction changed from roughly row-diagonal to directly row-normal, the rate at which the spanwise plume width increased with downwind distance increased by a factor of two. Similarly, the rate at which the plume height increased with downwind distance was higher for row-perpendicular plumes than for row-diagonal plumes. Row-diagonal plumes exhibited a much higher spanwise skewness than did the row-normal plumes, but for all plumes the skewnesses tended towards zero (symmetric) with increasing downwind distance.
Drosophila suzukii is widely studied because of its status as a global pest of berries and soft f... more Drosophila suzukii is widely studied because of its status as a global pest of berries and soft fruits. Environmental conditions and access to food resources impact the physiology and fitness of D. suzukii; these factors could also affect dispersal. Flight mills are a convenient tool for measuring and comparing the flight performance of insects. In this study, two experiments examined the effects of diet and humidity on D. suzukii flight performance using custom-built flight mills, and a third experiment compared the energy reserves of D. suzukii flown or not flown on flight mills. Over all flight assays, the median flight distance and duration were 27.16 m and 2.37 min, respectively, and the mean flight velocity was 0.18 m/s. The maximum flight distance and duration by an individual were 1.75 km and 2.35 h, respectively. Drosophila suzukii provisioned with blossoms, fruits, or standard laboratory diets flew farther distances and longer durations than starved flies. While starvation was associated with reduced flight performance, there were no observed differences between diet types. It remains unclear whether D. suzukii consistently use lipids, glycogen, sugar, or another energy source for flight because tethered individuals may not have flown enough to deplete energy reserves. Humidity did not affect flight performance of D. suzukii within a ~ 2 h test period. These data indicate that most D. suzukii are likely to remain within limited area (e.g., within a field) but that some individuals can disperse long distances (field to field spread). Keywords Spotted-wing drosophila • Dispersal • Flight mill • Flight energy Key Message • On average Drosophila suzukii flew for relatively limited duration and distance but some individuals were capable of long-distance dispersion. • Drosophila suzukii subsisting on natural and artificial diets flew farther distances and longer durations than starved flies on tethered flight mills. • Conditions between 30 and 80% relative humidity did not affect the tethered flight performance of Drosophila suzukii within a 2-h test period. Communicated by A. Biondi.
An infectious disease characterized with short bills and protruding tongues has attacked to meat ... more An infectious disease characterized with short bills and protruding tongues has attacked to meat ducks in China since March 2015, which has caused ducks poor growth and enormous economic losses to duck industry of China. It was eventually proved to be caused by parvovirus after pathogen isolation and identification. As the genomic sequence analysis showed, this pathogen shared 90.8-94.6% of nucleotide identity with goose parvovirus (GPV), and it was called duck-origin novel goose parvovirus (N-GPV). In this study, a quantitative loop-mediated isothermal amplification (qLAMP) assay was developed for the rapid diagnosis of N-GPV. A set of four specific primers, two inner and two outer, were designed targeting at VP3 gene, which could be completed within 60 min at 65°C in water bath or on a real-time PCR instrument for quantitative analysis. Specificity test of LAMP assay showed that there was no cross-reactivity between N-GPV and other duck pathogens, and the detection limit of qLAMP ...
Perhaps the earliest form of monitoring the regional spread of plant disease was a group of growe... more Perhaps the earliest form of monitoring the regional spread of plant disease was a group of growers gathering together at the market and discussing what they see in their crops. This type of reporting continues to this day through regional extension blogs, by crop consultants and more formal scouting of sentential plots in the IPM PIPE network ( http://www.ipmpipe.org/ ). As our knowledge of plant disease epidemiology has increased, we have also increased our ability to detect and monitor the presence of pathogens and use this information to make management decisions in commercial production systems. The advent of phylogenetics, next-generation sequencing, and nucleic acid amplification technologies has allowed for development of sensitive and accurate assays for pathogen inoculum detection and quantification. The application of these tools is beginning to change how we manage diseases with airborne inoculum by allowing for the detection of pathogen movement instead of assuming it a...
At the plant or stand level, leaf orientation is often highly anisotropic and heterogeneous, yet ... more At the plant or stand level, leaf orientation is often highly anisotropic and heterogeneous, yet most analyses neglect such complexity. In many cases, this is due to the di culty in measuring the spatial variation of the leaf angle distribution function. There is a critical need for a technique that can rapidly measure the leaf angle distribution function at any point in space and time. A new method was developed and tested that uses terrestrial LiDAR scanning data to rapidly measure the three-dimensional distribution of leaf orientation for an arbitrary volume of leaves. The method triangulates laser-leaf intersection points recorded by the LiDAR scan, which allows for easy calculation of normal vectors. As a byproduct, the triangulation also yields continuous surfaces that reconstruct individual leaves. In order to produce a probability density function for leaf orientation from triangle normal vectors, it is critical that the proper weighting be applied to each triangle. Otherwise, results will heavily bias toward normal vectors pointed toward the the LiDAR scanner. The method was validated using artificially generated LiDAR data where the exact leaf angle distributions were known, and in the field for an isolated tree and
The rapid evolution of high performance computing technology has allowed for the development of e... more The rapid evolution of high performance computing technology has allowed for the development of extremely detailed models of the urban and natural environment. Although models can now represent sub-meter-scale variability in environmental geometry, model users are often unable to specify the geometry of real domains at this scale given available measurements. An emerging technology in this field has been the use of terrestrial LiDAR scanning data to rapidly measure the threedimensional geometry of trees such as the distribution of leaf area. However, current LiDAR methods su↵er from the limitation that they require detailed knowledge of leaf orientation in order to translate projected leaf area into actual leaf area. Common methods for measuring leaf orientation are often tedious or inaccurate, which places constraints on the LiDAR measurement technique. This work presents a new method to simultaneously measure leaf orientation and leaf area within an arbitrarily defined volume using terrestrial LiDAR data. The novelty of the method lies in the direct measurement of the fraction of projected leaf area G from the LiDAR data which is required to relate projected leaf area to total leaf area, and in the new way in which radiation transfer theory was used to calculate leaf area from the LiDAR data. The method was validated by comparing LiDAR-measured leaf area to 1) 'synthetic' or computer-generated LiDAR data where the exact area was known, and 2) direct measurements of leaf area in the field using destructive sampling. Overall, agreement between the LiDAR and reference measurements was very good, showing a normalized root-mean-squared-error of about 15% for the synthetic tests, and 13% in the field.
and the Aral Sea Experiment Station for Plant Genetic Resources, Chelkar Town, Kazakhstan, was co... more and the Aral Sea Experiment Station for Plant Genetic Resources, Chelkar Town, Kazakhstan, was conducted in the fall of 2000. Hop (Humulus lupulus var. lupulus) cones were collected from wild plants growing on trees in a moist area about 50 km NE of Emba, Kazakhstan. A portion of the seeds were brought to the US and donated to the US Department of Agriculture, Agricultural Research Service, National Clonal Germplasm Repository in Corvallis, Oregon. Of 74 seedlings that were germinated from Kazakhstani seedlots, four seedlings from PI 635262 demonstrated resistance to powdery mildew, caused by Podosphaera macularis (Braun and Takamatsu). One of these resistant seedlings, 'Kazak 2000', exhibited a hypersensitive response after challenge by powdery mildew, especially when incubated at temperatures greater than 29°C post-infection. In greenhouse assays with an Oregon field population of P. macularis, macroscopic signs of powdery mildew were not observed following repeated inoculations. In laboratory assays at 18°C, 'Kazak 2000' did not develop powdery mildew when challenged with a P. macularis isolate capable of overcoming resistance genes R b , R 3 , and R 5. Infection of 55% of detached leaves was observed when challenged with characterized isolates
Detection and Diagnostics of Plant Pathogens, 2014
Knowledge of inoculum presence has been used for decades to help guide disease management decisio... more Knowledge of inoculum presence has been used for decades to help guide disease management decisions. However, its implementation on a broad scale has been limited due to the capital costs and technical skill required to effectively monitor pathogen presence across large areas. Recent advances in nucleic acid detection technologies are showing promise in enabling field level implementation of inoculum detection and quantification to aid in disease management decisions. Over the past 7 years we have investigated the use various molecular approaches to monitor the presence of Erysiphe necator in commercial vineyards and time fungicide applications based on its detection. We have found loop mediated isothermal amplification (LAMP) to be a robust method for the detection of E. necator DNA that may be suitable for practitioner implementation.
Management of grape powdery mildew (Erysiphe necator) and other polycyclic diseases often relies ... more Management of grape powdery mildew (Erysiphe necator) and other polycyclic diseases often relies on calendar-based pesticide application schedules that assume the presence of inoculum. An inexpensive, loop-mediated isothermal amplification (LAMP) assay was designed to quickly detect airborne inoculum of E. necator to determine when to initiate a fungicide application programme. Field efficacy was tested in 2010 and 2011 in several commercial and research vineyards in the Willamette Valley of Oregon from pre-bud break to v eraison. In each vineyard, three impaction spore traps were placed adjacent to the trunk. One trap was maintained and used by the grower to conduct the LAMP assay (G-LAMP) on-site and the other two traps were used for laboratory-conducted LAMP (L-LAMP) and quantitative PCR assay (qPCR). Using the qPCR as a gold standard, L-LAMP was comparable with qPCR in both years, and G-LAMP was comparable to qPCR in 2011. Latent class analysis indicated that qPCR had a true positive proportion of 98% in 2010 and 89% in 2011 and true negative proportion of 96% in 2010 and 64% in 2011. An average of 3Á3 fewer fungicide applications were used when they were initiated based on spore detection relative to the grower standard practice. There were no significant differences in berry or leaf incidence between plots with fungicides initiated at detection or grower standard practice plots, suggesting that growers using LAMP to initiate fungicide applications can use fewer fungicide applications to manage powdery mildew compared to standard practices.
Turbulent particle dispersion in plant canopies plays an important role in many agricultural and ... more Turbulent particle dispersion in plant canopies plays an important role in many agricultural and forestry ecosystems. Most research on dispersion in plant canopies has focused on dispersal patterns in homogeneous dense canopies and/or on patterns far from the source. To study near-source particle dispersion in a sparse agricultural canopy, a series of point-source particle release events was conducted in a commercial vineyard. Analysis of the wind velocity data indicated that the majority of the flow in the open spaces between the vine rows was channeled parallel to the vine rows regardless of the direction of the mean wind above the canopy. Although this channeling led to significant turning of the mean velocity, profiles of turbulent statistics taken at times when the above-canopy winds were nearly parallel to the vine rows showed similar behavior to canopy flow profiles in previous studies. The particle release events were conducted using fluorescent microspheres with similar physical characteristics to the spores of multiple airborne fungal pathogens of grapes (diameter = 10-45 µm, density = 1.0 g/cm 3). Microspheres were released from two vertical positions within the canopy and monitored using a dense three dimensional impaction trap array in the nearsource region (1-5 canopy heights downwind). The shape of the microsphere plumes was strongly impacted by the flow channeling within the canopy. Specifically, the plumes' maximum concentrations were typically channelled down the aisle in which they originated. The spanwise concentration profile also tended to be skewed from the release aisle toward the mean wind direction above the canopy. This was believed to be caused by the wind directional shear created by the difference between the mean wind direction above the canopy and the vine row direction as well as the filtering effects of the plants themselves.
A 3-year field rotation study was conducted to assess the potential of switchgrass (Panicum virga... more A 3-year field rotation study was conducted to assess the potential of switchgrass (Panicum virgatum) to suppress root-knot nematodes (Meloidogyne arenaria), southern blight (Sclerotium rolfsii), and aflatoxigenic fungi (Aspergillus sp.) in peanut (Arachis hypogaea L.) and to assess shifts in microbial populations following crop rotation. Switchgrass did not support populations of root-knot nematodes but supported high populations of nonparasitic nematodes. Peanut with no nematicide applied and following 2 years of switchgrass had the same nematode populations as continuous peanut plus nematicide. Neither previous crop nor nematicide significantly reduced the incidence of pods infected with Aspergillus. However, pod invasion by A. flavus was highest in plots previously planted with peanut and not treated with nematicide. Peanut with nematicide applied at planting following 2 years of switchgrass had significantly less incidence of southern blight than either continuous peanut withou...
Large-eddy simulations of approximately resolved heterogeneous vegetative canopies with repeating... more Large-eddy simulations of approximately resolved heterogeneous vegetative canopies with repeating row structure were compared to 'equivalent' homogeneous simulations to explore how overall canopy density and horizontal heterogeneity influence the vertical transport of non-depositing massless fluid parcels. A Lagrangian approach was used to quantify particle dispersion. The subgrid component of particle motion was modeled with a Langevin equation that was integrated with a new semi-implicit scheme that successfully minimized rogue trajectories. With rogue trajectories controlled, the subgrid model had a negligible impact on average statistics. Analysis suggested that above the canopy top, canopy density and heterogeneity had a minor effect on mean profiles of particle concentration and vertical flux. However, increasing canopy density resulted in a linear increase in particle residence time, and increased the importance of release height on canopy escape. The average time of persistent vertical particle motions did not follow this monotonic trend. For sufficiently dense canopies, the time scale of persistent vertical motions increased with decreasing canopy density in agreement with mixing-layer scaling. As wall shear became significant, a
The blackberry rust pathogen Phragmidium violaceum was first observed in Oregon in spring 2005 on... more The blackberry rust pathogen Phragmidium violaceum was first observed in Oregon in spring 2005 on both commercially cultivated Rubus laciniatus (Evergreen blackberry) and naturalized R. armeniacus (Himalayan blackberry). Several commercial plantings suffered severe economic losses. In 2006 to 2008, all five spore stages of this autoecious, macrocyclic rust pathogen were observed annually, and asexual perennation of the pathogen on old leaves or in leaf buds was not evident in the disease cycle. In field experiments, teliospore germination and infection by basidiospores occurred mostly during April. On potted “trap” plants exposed for periods of 1 week under dense collections of dead leaves bearing teliospores, basidiospore infection was associated with wetness durations of >16 h with mean temperatures >8°C. Trap plants placed under the bundles of collected leaves frequently developed spermagonia, whereas only 1 of 630 trap plants placed in a production field of R. laciniatus b...
Powdery mildew is a serious disease of pumpkin throughout the Northeastern United States. Control... more Powdery mildew is a serious disease of pumpkin throughout the Northeastern United States. Control of pumpkin powdery mildew is currently achieved through the use of a calendar-based application of fungicides. Three non-pumpkin weather-based fungicide scheduling programs for powdery mildew were evaluated to determine their usefulness in the control of cucurbit
69th Annual Pacific Northwest Insect Management Conference, held January 11th and 12th, 2010 at t... more 69th Annual Pacific Northwest Insect Management Conference, held January 11th and 12th, 2010 at the Hilton Hotel, Portland, Oregon.
In 2019, a national survey of 252 members of the United States grape industry from 20 states asse... more In 2019, a national survey of 252 members of the United States grape industry from 20 states assessed knowledge perception of fungicide resistance management, application of that knowledge to vineyard practices, and knowledge acquisition sources. Overall, respondents demonstrated clear understanding of resistance management practices. The specific distribution of responses was influenced by the respondent's job role, duration of industry experience, and their farming operation size. Nationally, respondents were moderately familiar with the acronym FRAC (Fungicide Resistance Action Committee), with nearly 75% indicating they could identify the FRAC code of a fungicide. They felt moderately competent they could design a fungicide program that adhered to resistance management principles. Respondents identified fungicide resistance as a serious problem nationally, and as a moderate problem in their own vineyards. They ranked practices that include rotating fungicides of different FRAC codes, avoiding multiple sequential applications of the same trade name or FRAC code, tank mixing with different FRAC codes, using multisite products in a spray program, routine sprayer maintenance and calibration, and good canopy management as very-to-extremely important in managing fungicide resistance; whereas practices such as rotating between trade names and tank mixing different trade names ranked slightly important. Respondents identified university-based extension programs as the primary information resource for fungicide efficacy and fungicide stewardship (resistance management). To maximize potential effect, these results suggest that future educational efforts should be aimed at improving practices for fungicide resistance stewardship and should align with the knowledgebase and demographic factors of the target audience-particularly their job role, experience, and size of operation.
Grape powdery mildew epidemics, caused by Erysiphe necator, are initiated by the release and subs... more Grape powdery mildew epidemics, caused by Erysiphe necator, are initiated by the release and subsequent germination of ascospores from mature chasmothecia. Interrupting the development of chasmothecia prior to overwintering may reduce or prevent the overwintering of E. necator in vineyards, thereby reducing initial disease incidence observed the following growing season. At the end of the grape growing season in 2014 and 2015, one application of Organic JMS Stylet Oil (Vero Beach, FL) at a rate of 10 ml/liter was applied on four treatment dates using an air-assisted backpack sprayer onto Chardonnay grapevines within a vineyard. Leaves were collected weekly and chasmothecia enumerated from the first observation of chasmothecia primordia development until the onset of rains (approximately 5 weeks). In 2014, all stylet oil treatment plots developed significantly fewer chasmothecia than nontreated control plots in 2014 (P = 0.04), and there were no differences in treatment date observed...
Grape powdery mildew (GPM) fungicide programs consist of 5 to 15 applications, depending on regio... more Grape powdery mildew (GPM) fungicide programs consist of 5 to 15 applications, depending on region or market, in an attempt to achieve the high fruit quality standards demanded by the market. Understanding how fungicides redistribute and targeting redistributing fungicide to critical crop phenological stages could improve fungicide protection of grape clusters. This study evaluated fungicide redistribution in grapevines from major fungicide groups labeled for GPM control. Translaminar and xylem redistribution was examined by placing fungicide-impregnated filter disks on the adaxial or abaxial leaf surface of detached leaves for 10 min and then incubating for 48 h before inoculating the abaxial surface with conidia. Vapor redistribution used Teflon disks sprayed with fungicides and placed on the abaxial leaf surface of detached leaves 48 h before inoculation. Disease development was rated 10 days later. Translaminar movement through calyptra was tested using flowering potted vines. A...
ABSTRACTPowdery mildew is the most important disease of grapevines worldwide. Despite the potenti... more ABSTRACTPowdery mildew is the most important disease of grapevines worldwide. Despite the potential for rapid spread by the causal pathogen, grape powdery mildew has been effectively managed using fungicide applications applied based on a calendar schedule or modeled disease risk index. Various epidemiological models for predicting disease development or risk have helped to improve disease management. The Gubler-Thomas (GT) risk index is a popular disease risk model used by many growers in the western U.S. We modified the GT risk index using fuzzy logic to address both biological and mechanical uncertainty in the pathosystem. The spraying schedule suggested by the fuzzy-modified GT risk index was tested in eight site-years. Overall, the fuzzy-modified risk index maintained comparable levels of disease control as both the original model and a calendar based treatment, and had significantly less disease than the untreated control. The fungicide use efficiency of the fuzzy-modified GT ...
Agricultural systems are exposed to and influenced by particles of many types (e.g., pathogens, p... more Agricultural systems are exposed to and influenced by particles of many types (e.g., pathogens, pollen, pests), the concentrations of which are typically highest in the regions immediately surrounding their sources. The intermittent nature of trellised canopies creates an unique canopy architecture that directly affects the shape of particulate plumes and tends to alter their transport patterns in the near-source region. To investigate the behavior of particle plumes near their sources in a trellised canopy, a set of particle release experiments was conducted during a field campaign in an Oregon vineyard in 2013. Specifically, plumes of inert fluorescent microspheres (10-45 μm diameter) were released into the canopy during periods when the mean wind direction was significantly different from the vine-row direction. Plume concentrations were collected at over 100 separate locations in a three-dimensional space < 10 canopy heights downwind of the source during each release period. These plumes were more complex than those released during periods of row-aligned winds. A novel analysis approach using the superposition of two orthogonal Gaussian plume equations was developed to quantitatively assess the behavior of the plumes' shape and its dependence on wind direction and magnitude and on particle release height. Basic plume shape parameters, as determined by integrating the superposed Gaussian equation, varied significantly as a function of the mean wind direction. As the wind direction changed from roughly row-diagonal to directly row-normal, the rate at which the spanwise plume width increased with downwind distance increased by a factor of two. Similarly, the rate at which the plume height increased with downwind distance was higher for row-perpendicular plumes than for row-diagonal plumes. Row-diagonal plumes exhibited a much higher spanwise skewness than did the row-normal plumes, but for all plumes the skewnesses tended towards zero (symmetric) with increasing downwind distance.
Drosophila suzukii is widely studied because of its status as a global pest of berries and soft f... more Drosophila suzukii is widely studied because of its status as a global pest of berries and soft fruits. Environmental conditions and access to food resources impact the physiology and fitness of D. suzukii; these factors could also affect dispersal. Flight mills are a convenient tool for measuring and comparing the flight performance of insects. In this study, two experiments examined the effects of diet and humidity on D. suzukii flight performance using custom-built flight mills, and a third experiment compared the energy reserves of D. suzukii flown or not flown on flight mills. Over all flight assays, the median flight distance and duration were 27.16 m and 2.37 min, respectively, and the mean flight velocity was 0.18 m/s. The maximum flight distance and duration by an individual were 1.75 km and 2.35 h, respectively. Drosophila suzukii provisioned with blossoms, fruits, or standard laboratory diets flew farther distances and longer durations than starved flies. While starvation was associated with reduced flight performance, there were no observed differences between diet types. It remains unclear whether D. suzukii consistently use lipids, glycogen, sugar, or another energy source for flight because tethered individuals may not have flown enough to deplete energy reserves. Humidity did not affect flight performance of D. suzukii within a ~ 2 h test period. These data indicate that most D. suzukii are likely to remain within limited area (e.g., within a field) but that some individuals can disperse long distances (field to field spread). Keywords Spotted-wing drosophila • Dispersal • Flight mill • Flight energy Key Message • On average Drosophila suzukii flew for relatively limited duration and distance but some individuals were capable of long-distance dispersion. • Drosophila suzukii subsisting on natural and artificial diets flew farther distances and longer durations than starved flies on tethered flight mills. • Conditions between 30 and 80% relative humidity did not affect the tethered flight performance of Drosophila suzukii within a 2-h test period. Communicated by A. Biondi.
An infectious disease characterized with short bills and protruding tongues has attacked to meat ... more An infectious disease characterized with short bills and protruding tongues has attacked to meat ducks in China since March 2015, which has caused ducks poor growth and enormous economic losses to duck industry of China. It was eventually proved to be caused by parvovirus after pathogen isolation and identification. As the genomic sequence analysis showed, this pathogen shared 90.8-94.6% of nucleotide identity with goose parvovirus (GPV), and it was called duck-origin novel goose parvovirus (N-GPV). In this study, a quantitative loop-mediated isothermal amplification (qLAMP) assay was developed for the rapid diagnosis of N-GPV. A set of four specific primers, two inner and two outer, were designed targeting at VP3 gene, which could be completed within 60 min at 65°C in water bath or on a real-time PCR instrument for quantitative analysis. Specificity test of LAMP assay showed that there was no cross-reactivity between N-GPV and other duck pathogens, and the detection limit of qLAMP ...
Perhaps the earliest form of monitoring the regional spread of plant disease was a group of growe... more Perhaps the earliest form of monitoring the regional spread of plant disease was a group of growers gathering together at the market and discussing what they see in their crops. This type of reporting continues to this day through regional extension blogs, by crop consultants and more formal scouting of sentential plots in the IPM PIPE network ( http://www.ipmpipe.org/ ). As our knowledge of plant disease epidemiology has increased, we have also increased our ability to detect and monitor the presence of pathogens and use this information to make management decisions in commercial production systems. The advent of phylogenetics, next-generation sequencing, and nucleic acid amplification technologies has allowed for development of sensitive and accurate assays for pathogen inoculum detection and quantification. The application of these tools is beginning to change how we manage diseases with airborne inoculum by allowing for the detection of pathogen movement instead of assuming it a...
At the plant or stand level, leaf orientation is often highly anisotropic and heterogeneous, yet ... more At the plant or stand level, leaf orientation is often highly anisotropic and heterogeneous, yet most analyses neglect such complexity. In many cases, this is due to the di culty in measuring the spatial variation of the leaf angle distribution function. There is a critical need for a technique that can rapidly measure the leaf angle distribution function at any point in space and time. A new method was developed and tested that uses terrestrial LiDAR scanning data to rapidly measure the three-dimensional distribution of leaf orientation for an arbitrary volume of leaves. The method triangulates laser-leaf intersection points recorded by the LiDAR scan, which allows for easy calculation of normal vectors. As a byproduct, the triangulation also yields continuous surfaces that reconstruct individual leaves. In order to produce a probability density function for leaf orientation from triangle normal vectors, it is critical that the proper weighting be applied to each triangle. Otherwise, results will heavily bias toward normal vectors pointed toward the the LiDAR scanner. The method was validated using artificially generated LiDAR data where the exact leaf angle distributions were known, and in the field for an isolated tree and
The rapid evolution of high performance computing technology has allowed for the development of e... more The rapid evolution of high performance computing technology has allowed for the development of extremely detailed models of the urban and natural environment. Although models can now represent sub-meter-scale variability in environmental geometry, model users are often unable to specify the geometry of real domains at this scale given available measurements. An emerging technology in this field has been the use of terrestrial LiDAR scanning data to rapidly measure the threedimensional geometry of trees such as the distribution of leaf area. However, current LiDAR methods su↵er from the limitation that they require detailed knowledge of leaf orientation in order to translate projected leaf area into actual leaf area. Common methods for measuring leaf orientation are often tedious or inaccurate, which places constraints on the LiDAR measurement technique. This work presents a new method to simultaneously measure leaf orientation and leaf area within an arbitrarily defined volume using terrestrial LiDAR data. The novelty of the method lies in the direct measurement of the fraction of projected leaf area G from the LiDAR data which is required to relate projected leaf area to total leaf area, and in the new way in which radiation transfer theory was used to calculate leaf area from the LiDAR data. The method was validated by comparing LiDAR-measured leaf area to 1) 'synthetic' or computer-generated LiDAR data where the exact area was known, and 2) direct measurements of leaf area in the field using destructive sampling. Overall, agreement between the LiDAR and reference measurements was very good, showing a normalized root-mean-squared-error of about 15% for the synthetic tests, and 13% in the field.
and the Aral Sea Experiment Station for Plant Genetic Resources, Chelkar Town, Kazakhstan, was co... more and the Aral Sea Experiment Station for Plant Genetic Resources, Chelkar Town, Kazakhstan, was conducted in the fall of 2000. Hop (Humulus lupulus var. lupulus) cones were collected from wild plants growing on trees in a moist area about 50 km NE of Emba, Kazakhstan. A portion of the seeds were brought to the US and donated to the US Department of Agriculture, Agricultural Research Service, National Clonal Germplasm Repository in Corvallis, Oregon. Of 74 seedlings that were germinated from Kazakhstani seedlots, four seedlings from PI 635262 demonstrated resistance to powdery mildew, caused by Podosphaera macularis (Braun and Takamatsu). One of these resistant seedlings, 'Kazak 2000', exhibited a hypersensitive response after challenge by powdery mildew, especially when incubated at temperatures greater than 29°C post-infection. In greenhouse assays with an Oregon field population of P. macularis, macroscopic signs of powdery mildew were not observed following repeated inoculations. In laboratory assays at 18°C, 'Kazak 2000' did not develop powdery mildew when challenged with a P. macularis isolate capable of overcoming resistance genes R b , R 3 , and R 5. Infection of 55% of detached leaves was observed when challenged with characterized isolates
Detection and Diagnostics of Plant Pathogens, 2014
Knowledge of inoculum presence has been used for decades to help guide disease management decisio... more Knowledge of inoculum presence has been used for decades to help guide disease management decisions. However, its implementation on a broad scale has been limited due to the capital costs and technical skill required to effectively monitor pathogen presence across large areas. Recent advances in nucleic acid detection technologies are showing promise in enabling field level implementation of inoculum detection and quantification to aid in disease management decisions. Over the past 7 years we have investigated the use various molecular approaches to monitor the presence of Erysiphe necator in commercial vineyards and time fungicide applications based on its detection. We have found loop mediated isothermal amplification (LAMP) to be a robust method for the detection of E. necator DNA that may be suitable for practitioner implementation.
Management of grape powdery mildew (Erysiphe necator) and other polycyclic diseases often relies ... more Management of grape powdery mildew (Erysiphe necator) and other polycyclic diseases often relies on calendar-based pesticide application schedules that assume the presence of inoculum. An inexpensive, loop-mediated isothermal amplification (LAMP) assay was designed to quickly detect airborne inoculum of E. necator to determine when to initiate a fungicide application programme. Field efficacy was tested in 2010 and 2011 in several commercial and research vineyards in the Willamette Valley of Oregon from pre-bud break to v eraison. In each vineyard, three impaction spore traps were placed adjacent to the trunk. One trap was maintained and used by the grower to conduct the LAMP assay (G-LAMP) on-site and the other two traps were used for laboratory-conducted LAMP (L-LAMP) and quantitative PCR assay (qPCR). Using the qPCR as a gold standard, L-LAMP was comparable with qPCR in both years, and G-LAMP was comparable to qPCR in 2011. Latent class analysis indicated that qPCR had a true positive proportion of 98% in 2010 and 89% in 2011 and true negative proportion of 96% in 2010 and 64% in 2011. An average of 3Á3 fewer fungicide applications were used when they were initiated based on spore detection relative to the grower standard practice. There were no significant differences in berry or leaf incidence between plots with fungicides initiated at detection or grower standard practice plots, suggesting that growers using LAMP to initiate fungicide applications can use fewer fungicide applications to manage powdery mildew compared to standard practices.
Turbulent particle dispersion in plant canopies plays an important role in many agricultural and ... more Turbulent particle dispersion in plant canopies plays an important role in many agricultural and forestry ecosystems. Most research on dispersion in plant canopies has focused on dispersal patterns in homogeneous dense canopies and/or on patterns far from the source. To study near-source particle dispersion in a sparse agricultural canopy, a series of point-source particle release events was conducted in a commercial vineyard. Analysis of the wind velocity data indicated that the majority of the flow in the open spaces between the vine rows was channeled parallel to the vine rows regardless of the direction of the mean wind above the canopy. Although this channeling led to significant turning of the mean velocity, profiles of turbulent statistics taken at times when the above-canopy winds were nearly parallel to the vine rows showed similar behavior to canopy flow profiles in previous studies. The particle release events were conducted using fluorescent microspheres with similar physical characteristics to the spores of multiple airborne fungal pathogens of grapes (diameter = 10-45 µm, density = 1.0 g/cm 3). Microspheres were released from two vertical positions within the canopy and monitored using a dense three dimensional impaction trap array in the nearsource region (1-5 canopy heights downwind). The shape of the microsphere plumes was strongly impacted by the flow channeling within the canopy. Specifically, the plumes' maximum concentrations were typically channelled down the aisle in which they originated. The spanwise concentration profile also tended to be skewed from the release aisle toward the mean wind direction above the canopy. This was believed to be caused by the wind directional shear created by the difference between the mean wind direction above the canopy and the vine row direction as well as the filtering effects of the plants themselves.
A 3-year field rotation study was conducted to assess the potential of switchgrass (Panicum virga... more A 3-year field rotation study was conducted to assess the potential of switchgrass (Panicum virgatum) to suppress root-knot nematodes (Meloidogyne arenaria), southern blight (Sclerotium rolfsii), and aflatoxigenic fungi (Aspergillus sp.) in peanut (Arachis hypogaea L.) and to assess shifts in microbial populations following crop rotation. Switchgrass did not support populations of root-knot nematodes but supported high populations of nonparasitic nematodes. Peanut with no nematicide applied and following 2 years of switchgrass had the same nematode populations as continuous peanut plus nematicide. Neither previous crop nor nematicide significantly reduced the incidence of pods infected with Aspergillus. However, pod invasion by A. flavus was highest in plots previously planted with peanut and not treated with nematicide. Peanut with nematicide applied at planting following 2 years of switchgrass had significantly less incidence of southern blight than either continuous peanut withou...
Large-eddy simulations of approximately resolved heterogeneous vegetative canopies with repeating... more Large-eddy simulations of approximately resolved heterogeneous vegetative canopies with repeating row structure were compared to 'equivalent' homogeneous simulations to explore how overall canopy density and horizontal heterogeneity influence the vertical transport of non-depositing massless fluid parcels. A Lagrangian approach was used to quantify particle dispersion. The subgrid component of particle motion was modeled with a Langevin equation that was integrated with a new semi-implicit scheme that successfully minimized rogue trajectories. With rogue trajectories controlled, the subgrid model had a negligible impact on average statistics. Analysis suggested that above the canopy top, canopy density and heterogeneity had a minor effect on mean profiles of particle concentration and vertical flux. However, increasing canopy density resulted in a linear increase in particle residence time, and increased the importance of release height on canopy escape. The average time of persistent vertical particle motions did not follow this monotonic trend. For sufficiently dense canopies, the time scale of persistent vertical motions increased with decreasing canopy density in agreement with mixing-layer scaling. As wall shear became significant, a
The blackberry rust pathogen Phragmidium violaceum was first observed in Oregon in spring 2005 on... more The blackberry rust pathogen Phragmidium violaceum was first observed in Oregon in spring 2005 on both commercially cultivated Rubus laciniatus (Evergreen blackberry) and naturalized R. armeniacus (Himalayan blackberry). Several commercial plantings suffered severe economic losses. In 2006 to 2008, all five spore stages of this autoecious, macrocyclic rust pathogen were observed annually, and asexual perennation of the pathogen on old leaves or in leaf buds was not evident in the disease cycle. In field experiments, teliospore germination and infection by basidiospores occurred mostly during April. On potted “trap” plants exposed for periods of 1 week under dense collections of dead leaves bearing teliospores, basidiospore infection was associated with wetness durations of >16 h with mean temperatures >8°C. Trap plants placed under the bundles of collected leaves frequently developed spermagonia, whereas only 1 of 630 trap plants placed in a production field of R. laciniatus b...
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