1,721,027 research outputs found
Assessment of leaf water potential and stomatal conductance as early signs of stress in young hazelnut tree in Willamette valley
Full text linkCorylus avellana L. is a species highly susceptible to water stresses caused by vapor pressure deficit and high temperature. Under such conditions, transpiration is strongly constrained even with good soil water availability. This is due to ineffective drought resistance mechanisms and indicates the need to identify early indicators of plant stress that are easy to measure, effective and efficient. This research explored the possibility of using stomatal conductance and leaf water potentials as early indicators of stress. For this purpose, an experiment was set up in a commercial 5-year-old Corylus avellana L. var. 'McDonald' orchard located in Willamette valley. The experimental designed featured irrigated and rainfed trees, and potential stress indicators were monitored at different times of the day in canopy sections aligned to cardinal directions.
Results show that hazelnut trees rapidly reduced leaf stomatal conductance when the vapor pressure deficit increased to 2 and 2.5 kPa during the diurnal cycle in both irrigated and rainfed trees, even with good water availability. This suggests leaf stomatal conductance can be an efficient and effective early indicator of stress. In addition, results suggest that stomatal conductance should be measured on leaves on the west and north aspects of the canopy, where they showed lowest and highest values respectively. Leaf and stem water potential values increased during the measurement period and show a strong correlation, but their mean values do not show statistically significant differences between treatments. In Willamette valley conditions, stomatal conductance provided earlier indication of stress than water potential. The results obtained are of methodological importance for the future design of experimental plans
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Reevaluating filbertworm (Cydia latiferreana) phenology : implications for management in Willamette Valley orchards
No full textThe Filbertworm (FBW), Cydia latiferreana (Walsingham) (Lepidoptera: Tortricidae), is the key pest of hazelnuts in Oregon’s Willamette Valley, where 99% of the US crop is grown on roughly 95,000 acres. Adult female FBW moths lay individual eggs on leaves, close to the developing nut clusters. After eclosion from the eggs, the larvae search out nut clusters. When the nut cluster is located, larvae chew a small entry hole through the micropyle, a small pore on the basal scar of the shell and they begin feeding on the kernels. Low tolerance for damage (<1%) necessitates spray treatments against the pest. Untreated orchards are seen to experience upwards of 50% infestation rates. While there is a simple degree-day model to guide management timing, our data suggests that it is not performing well, and it also does not estimate life stage events after the initial flight period and coinciding egg laying and egg hatch period. Moth flights appear to be occurring both earlier and later in the season than historic norms, and growers particularly need guidance on late-season management. Most growers rely on a trap threshold method to time sprays, though some still use a calendar-based approach. Despite the severe damage caused by FBW, it is severely understudied. This research aims to gain a more robust understanding of the FBW and its damage by examining the viability of the FBW degree-day model, suggesting improvements using flight data from a large smart trap network throughout the Willamette Valley, intensive field sampling for immature stages, and lab-based temperature-dependent development studies to reevaluate the temperature thresholds.
We used an extensive network of 814 smart traps to monitor flight over three seasons (2022-2024), while intensive field sampling (2023-2024) and subsequent laboratory rearing characterized immature stage development. Lab-based temperature-dependent development trials established a lower developmental threshold (LDT) of 9.37°C for egg development, and a January 1st biofix was adopted for degree-day calculations based on variability analysis.
Results of this study demonstrated that moth flight commenced significantly earlier and persisted longer, with sustained pressure, than suggested by the historic model. A Beta CDF model effectively described the full cumulative flight season, particularly the early and late season activity. Similarly, all observed immature stage events (oviposition, egg hatch, larval entry) occurred substantially earlier in the season than previously predicted. Field sampling and rearing of larvae provided strong evidence for multivoltinism, revealing two distinct developmental pathways: one leading to rapid within-season adult emergence and another to spinning a hibernaculum and preparing for diapause.
These findings collectively indicate a significant shift in C. latiferreana phenology in the Willamette Valley. The updated LDT, revised biofix approach, comprehensive flight data, detailed characterization of immature stages, and evidence of multivoltinism provide a critical foundation for a new, more accurate phenology model. This new model framework will enable more precise timing of C. latiferreana management strategies, providing more effective and efficient treatments, while reducing broad-spectrum insecticide use overall, contributing to more productive and sustainable hazelnut orchards
Biology of tachinid parasitoids (Diptera) and their role in biological control of leafrollers (Lepidoptera: Tortricidae) in Washington tree fruit
Full text linkThesis (Ph.D.), Department of Entomology, Washington State UniversityThe tachinid fliesDepartment of Entomology, Washington State Universit
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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Determining the Impacts of Dormant Pruning Methods and Nitrogen Fertilization on Vitis vinifera 'Pinot noir' Bud Fruitfulness and Yield
Full text linkThe majority of grapes grown in Oregon are produced in Western Oregon’s Willamette Valley, where two-thirds of the acreage is planted to Pinot noir. The production of Pinot noir in the Willamette Valley comes at a high cost, and growers are seeking ways to increase profits while maintaining quality fruit production. Not many studies have addressed the impacts of vineyard management practices on bud fruitfulness, an important component of yield. To understand the impacts of pruning method (cane and spur) and N fertilization (N fertilization and no fertilization) on Pinot noir fruitfulness and yield, two separate experiments were conducted in commercial Pinot noir vineyards in Oregon.
Cane pruning is predominant in Oregon Pinot noir vineyards, as producers fear that spur pruning will result in low yields, due to a lack of basal bud fruitfulness. Cane- and spur-pruned vines were monitored over the course of two growing seasons and three dormant periods to determine the effect of pruning method on bud fruitfulness, vine growth, yield, and fruit composition. It was hypothesized that spur-pruning may lead to reduced yields when compared to cane-pruned vines, and that basal buds of Pinot noir would be fruitful regardless of pruning method. Results from the pruning trial indicate that basal buds of cane- and spur-pruned vines contain floral primordia, and similar primary bud fruitfulness and inflorescence primordia size were found regardless of pruning method. Vine growth was similar between treatments, and there was no effect of pruning method on yield and fruit composition. Differences in cluster architecture did exist; however, spur-pruned vines had more clusters of smaller size.
Nitrogen (N) fertilization is often avoided, as it is thought to create excess vegetative vigor and have a detrimental effect on wine quality; however, N-deficiency can lead to reduced yields. Nitrogen was applied in the amount of 44.8-67.3 kg N/ha/yr (40-60 lbs N/acre/yr) via fertigation in a low N site, and we evaluated the effect of nitrogen fertilization on bud fruitfulness, vine growth, yield, and fruit composition. It was hypothesized that N-fertilized vines would result in increased bud fruitfulness and yield. Bud fruitfulness was increased in N-fertilized vines after one year of N application, but differences did not exist within the primary bud. Bud fruitfulness was not affected after two years of N application. Early season vine growth was higher in N-fertilized vines after one year of N application, and pruning weights were higher after two years of N fertilization. We analyzed the legacy effect on N fertilization in a block that was supplied with 40-60 lbs N/acre in the two years prior to data collection. Nitrogen fertilization in this block did not affect bud fruitfulness, yield, or fruit composition, but pruning weights were increased in the N-fertilized vines. Overall, the effect of N fertilization on vegetative growth was minimal, and yield and fruit composition were similar between N-fertilized and non-fertilized vines.
Vine vigor was related to bud fruitfulness parameters in both experiments. In the N trial, greater bud fruitfulness was related to larger dormant cane size (weight and internode diameter). In both trials, greater inflorescence primordia size was observed with larger dormant cane internode diameter. The results of this work indicate that vine vigor affects Pinot noir bud fruitfulness more so than the dormant pruning and nitrogen fertilization practices used in these studies. In addition, basal buds of Pinot noir are fruitful. Thus, spur pruning is a viable option for Oregon Pinot noir producers and may decrease dormant pruning costs. Additionally, N application at the rates used herein had little impact on Pinot noir bud fruitfulness, vegetative growth, and yield
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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Effects of Diet and Humidity on Drosophila suzukii Flight Performance
No full textDrosophila suzukii is a global and economically significant pest of berries and other soft fruits. This insect can survive and reproduce under a wide variety of environmental conditions and with a substantial number of cultivated and wild hosts. Management of D. suzukii is commonly done with chemical control strategies. However, ecological and environmental costs associated with overreliance on insecticides are driving the research and adoption of integrated pest management practices. Integrated pest management incorporates multiple management tactics, including the use of natural enemies and mass trapping. Integrated pest management is improved with further research on pest biology and dispersal behavior. The research presented in this thesis examined the flight performance and nutrient utilization of D. suzukii subjected to various dietary treatments and relative humidity conditions.
Our study used flight mills to measure the distance, duration, and velocity that female D. suzukii fly between resources. Overall, the flight distances ranged from 1 m to 1.75 km, the median was 27 m, and the mean was 87 m. The flight distance of fed flies was two to four times greater than that of starved flies. Flight parameters of D. suzukii were not significantly influenced by humidity. Lifetime flight performance could not be measured on the flight mill, but we hypothesize that, given the availability of food and water, at least a portion of D. suzukii within a large population could disperse much farther than 1.75 km over their lifespan. The estimated flight parameters measured in our study are representative of laboratory-reared D. suzukii subjected to the various treatments in each experiment, and the scope of inference is limited to the comparisons in flight parameters between experimental groups because of unknown behavioral effects of tethering the insects. The levels of lipid, sugar, and glycogen reserves were measured in D. suzukii flown and not flown on the flight mill. The nutrient levels are reported, but it is still unclear what energy substrate, and how much of it, is utilized during flight. Drosophila suzukii flight performance and flight energy utilization will be better understood with additional research that builds on the results presented in this thesis
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NETTING APPLICATIONS FOR INSECT MANAGEMENT IN APPLE ORCHARDS
Full text linkExclusion netting may provide sustainable protection from apple insect pests where chemical control options are limited. To examine the efficacy of net enclosures to exclude direct pests and assess non-target effects, I investigated pest and natural enemy densities in net-enclosed versus open blocks. I conducted trials to assess the effects of large enclosures (48 trees) and small enclosures (three trees). In all studies, results were strikingly similar. Direct pest, codling moth (Cydia pomonella (L.)) and Euschistus conspersus Uhler, abundance and damage were lower inside the enclosures, while the abundance of an indirect pest, woolly apple aphid, Eriosoma lanigerum (Hausman) was substantially higher. The increase in woolly apple aphid densities may be related to the reduced abundance of two important groups of its natural enemies, lacewings and syrphids, inside the cages. These findings indicate that while netting structures may improve direct pest control, biological control services can be disrupted leading to indirect pest outbreaks.I investigated the ability of net enclosures to inhibit migration of codling moth, a key direct pest of apple. Mark-recapture experiments were used to assess the permeability to immigrating and emigrating adults. Moth emigration was reduced only slightly by the presence of the nets (versus controls), but only one moth released outside was recaptured inside the cages. This suggested that the netting is physically permeable to codling moth, but provides a behavioral barrier to external populations.Native stink bugs, also direct pests of apples, frequently migrate from uncultivated land into the orchard borders making them difficult to control. Using clear sticky panel traps, I determined the average height at which stink bugs migrate is from 2-3 m. With this information, I assessed the ability of a 4 m net barrier at the orchard border to exclude stink bugs and found that they reduce stink bug migration into the orchard. Through these studies, I established that net barriers can provide an additional method for direct pest control. Although, the negative effects on indirect pests and natural enemies need to be carefully considered for improving crop protection
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