To optimize pesticide applications to the canopies of deciduous perennial crops, spray volume should be adjusted throughout the year to match the changes in canopy volume and density. Machine-vision, computer-controlled, variable-rate sprayers are now commercially available and claim to provide adequate coverage with decreased spray volumes compared with constant-rate sprayers. However, there is little research comparing variable- and constant-rate spray applications as crop characteristics change throughout a growing season. This study evaluated spray volume, spray quality (e.g., coverage and deposit density), and off-target spray losses of variable- and constant-rate sprayers across multiple phenophases in an apple (Malus domestica) orchard and a grape (Vitis vinifera) vineyard. The variable-rate sprayer mode applied 67% to 74% less volume in the orchard and 61% to 80% less volume in the vineyard. Spray coverage (percent), measured by water-sensitive cards (WSC), was consistently greater in the constant-rate mode compared with the variable-rate mode, but in many cases, excessive coverage (i.e., over-spray) was recorded. The variable-rate sprayer reduced off-target losses, measured by WSC coverage, up to 40% in the orchard and up to 33% in the vineyard. Spray application deposit densities (droplets per square centimeter) on target canopies were typically greater in variable-rate mode. However, the deposit densities were confounded in over-spray conditions because droplets coalesced on the WSC resulting in artificially low values (i.e., few, very large droplets). Spray efficiencies were most improved early in the growing season, when canopy density was lowest, demonstrating the importance of tailoring spray volume to plant canopy characteristics.
Despite the significance of grape production to the fruit industry in Tennessee (TN), no published information has been available on viruses affecting grapevines in the state. Hence, a survey was conducted during the 2016 and 2017 growing seasons to determine the status of nine major viruses of grapevines in TN vineyards by taking advantage of classical serological assays and confirmatory nucleic acid-based diagnostic approaches. A total of 349 samples from 23 grapevine cultivars mostly displaying viral-like symptoms were collected from 23 commercial vineyards. All samples were assayed by DAS-ELISA for arabis mosaic virus (ArMV), grapevine leafroll-associated virus (GLRaV)-1, GLRaV-2, GLRaV-3, GLRaV-4, grapevine fanleaf virus (GFLV), tobacco ringspot virus (TRSV), and tomato ringspot virus (ToRSV). Selected serologically positive samples were also tested by RT-PCR, followed by Sanger sequencing of the generated amplicons. Additionally, 19 grapevines displaying symptoms characteristic of grapevine red blotch virus (GRBV) were also assayed by PCR followed by confirmatory sequencing-based methods. Collectively, these assays verifiably detected GLRaV-1, GLRaV-2, GLRaV-3, ToRSV, and GRBV in TN vineyards. This is the first record of the presence of these viruses in TN vineyards. ArMV, GLRaV-4, GFLV, and TRSV were not detected. The majority of samples tested positive for a single virus, whereas mixed infections with more than one virus were detected in 37% of samples.
Many medical schools have transitioned to an integrated curriculum to provide a more salient contextual appreciation of the practice of medicine. Various types of assessments are used in these curricula to support this integration. One of these, multidisciplinary exams, creates challenges for recognizing student performance in different disciplines. A concern for faculty is those students who pass the exams but upon closer scrutiny do poorly in one or more disciplines. Unfortunately, this trend can continue throughout preclinical training. We constructed a database of discipline-specific objective data for each course and that also provided cumulative data longitudinally through the curriculum. The data are used to populate reports for the students, advisors, and administrators. The database was broadened to include data from clerkship performance and residency match to provide a complete profile of student performance. Together, the data and reports provide a useful tool for student review and data-driven curriculum decisions.
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