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The occurrence of Creeping Mistletoe Muellerina eucalyptoides (DC) Barlow on introduced trees in a ~300 ha area in suburban Melbourne is reported for the third time. The first survey, completed in 1995, was repeated in 2005. Since 2005, there has been a large reduction in the number of trees infected by the mistletoe. This reverses the previously reported trend of an increase in the number and distribution of infected trees from 1995-2005. The reduction is not the result of loss of host trees or removal of individual mistletoes by arborists. Populations of the seed-dispersing Mistletoebird Dicaeum hirundinaceum, of mistletoe pollinators such as Red Wattlebird Anthochaera carunculata and 2 species of possums appear to be stable across all 3 surveys and seem unrelated to changes in mistletoe population size. [ABSTRACT FROM AUTHOR]

Background: Tree risk assessment methods have been developed to assist arborists in conducting thorough and systematic inspections of trees and the threat they pose to people or property. While these methods have many similarities, they also have a few key differences which may impact the decisions of those employing them. Moreover, arborists specify the associated timeframe for their risk assessment, which can range from months to years. How this impacts risk assessment reproducibility is unknown. Methods: To assess the impact of risk assessment methodology, we sent videos depicting trees in urban settings to arborists holding the International Society of Arboriculture (ISA) Tree Risk Assessment Qualification (TRAQ; n = 28) or Quantifi ed Tree Risk Assessment (QTRA; n = 21) training. These assessments were compared to those prepared by North American arborists lacking the TRAQ credential (ISA BMP; n = 11). ISA BMP arborists were also asked to assess trees using both a 1-year and a 3-year timeframe. Results: While a direct comparison between the QTRA and TRAQ assessments is not possible given differences in terminology, arborists with the latter training were less likely to rate trees as having "high" or "extreme" risk compared to their ISA BMP counterparts. Moreover, we found that switching to a longer timeframe did not increase the variability of risk assessments. Conclusions: These results give further insights into how different risk assessment methods compare when assessing the same group of trees as well as the impact of training efforts and specified timeframe. [ABSTRACT FROM AUTHOR]

Arborists commonly investigate the extent of stem decay to assess the likelihood of stem failure when conducting tree risk assessments. Studies have shown that: (i) arborists can sometimes judge the extent of internal decay based on external signs; (ii) sophisticated tools can reliably illustrate the extent of internal decay; and (iii) assessing components of tree risk can be highly subjective. We recruited 18 experienced tree risk assessors who held the International Society of Arboriculture's Tree Risk Assessment Qualification (TRAQ) to assess the likelihood of stem failure due to decay after each of five consecutive assessments on 30 individuals of 2 genera. The five assessment techniques, in stepwise order, were: (1) observing visually, (2) sounding the trunk with a mallet, (3) viewing a scaled diagram of the cross-section that revealed sound and decayed wood ascertained from resistance drilling, (4) viewing sonic and electrical resistance tomograms, and (5) consulting with a peer. For each technique, the assessors assigned two or more likelihood of failure ratings (LoFRs) for at least 83% of trees, which were proportionally greatest after the assessors viewed the tomograms; the proportions did not differ among the other four assessment techniques. Covariates that influenced the distribution of the LoFRs included percent of the cross-section that was decayed, and assessors' experience using resistance drilling devices and tomography in regular practice. Practitioners should be aware that disagreement on the likelihood of tree failure exists even among experienced arborists. [ABSTRACT FROM AUTHOR]

When working with urban trees, arborists can negatively impact urban wildlife. There have been recent efforts to strengthen wildlife protection and conservation during arboricultural practices, both legislatively and voluntarily through arboriculture organizations. To examine arborists' perceptions of these environmental policies and understand their experiences with urban wildlife, we conducted an international online survey of 805 arborists. Many respondents (n  = 481, 59.8%) reported being involved in tree work that resulted in wildlife injury or death, despite most respondents reportedly modifying work plans or objectives after encountering wildlife (n  = 598, 74.3%). Decisions to modify or cease work were most heavily influenced by the legal protection of species, wildlife having young, and the overall management objectives. Support for new wildlife best management practices (BMPs) was high (n  = 718, 90.3%), as was awareness of wildlife and arboriculture-related legislation (n  = 611, 77.2%). The findings demonstrate support amongst arborists for the implementation of wildlife policies to protect wildlife in urban forestry; however, implementation of such policies would require a non-prescriptive approach that is relevant to a diversity of wildlife concerns globally, causing concern amongst arborists about the applicability of such a document. Concerns also included the economic impacts of voluntary wildlife protection policies in arboriculture, where competitors may not adhere to industry standards or best practices. Given the support of arborists for increased wildlife protection policies, we recommend the development of international wildlife-focused BMPs for arboriculture, especially as an intermediary until legislation can be implemented or more rigorously enforced. [ABSTRACT FROM AUTHOR]

Background: Arboricultural tree climbing is inherently dangerous, in part because of the possibility of failure of the tie-in point (TIP). To help climbing arborists choose TIPs wisely, we have conducted several studies to quantify the magnitude and frequency of loading associated with arboricultural tree climbing. One parameter that has not been previously studied is whether the choice of climbing line influences loads experienced by a TIP as a climbing arborist ascends. Methods: The lead author conducted trials in which he ascended to 3 TIPs (in different trees) using 2 ascent techniques and 3 different climbing lines. During each trial, we measured loads at the TIP, and from the resulting time histories analyzed the magnitude and frequency of loading. We compared the effect of ascent technique, climbing line, and their interaction on the magnitude and frequency of loading. Results: During trials, the magnitude of loading varied between 1.1 and 1.5 times the lead author's weight and did not differ between ascent techniques, climbing lines, or their interaction. Loading frequency varied among ascent techniques, but not climbing lines. Footlocking induced loads at a wide range of frequencies, but 2 distinct frequencies were associated with ropewalking. Conclusion: Climbing arborists can use the results of this and our previous studies to help select a suitable TIP. It is important for climbing arborists to understand the magnitude of forces associated with ascending into and working in a tree. Future studies should investigate the load-bearing capacity of a TIP from the ground. [ABSTRACT FROM AUTHOR]

When professionals assess tree risk, they must consider the potential consequences associated with a branch or whole tree striking a person, vehicle, or structure. This process requires an assessor to determine the diameter and fall distance of a tree part and then gauge the likely damage to a target if failure occurred. The ability to accurately estimate diameter and fall distances is important, as direct measurements are not always possible. In this study, we examined whether differences exist between visual estimations and direction measurements of tree part diameters and fall distances among 106 arborists of differing experience levels. Our findings suggest arborists' estimations were reasonably accurate in comparison to direct measurements. International Society of Arboriculture Certified Arborists and experienced arborists were more accurate in diameter estimations than arborists lacking assessment experience. In contrast, nonexperienced arborists were closer in their fall distance estimations than arborists with risk assessment experience. [ABSTRACT FROM AUTHOR]

Risk assessment of urban trees is an incipient practice in Latin America, generally performed with foreign methods, due to the lack of qualified personnel and locally validated or adapted methodology. This article evaluates the application of three methods on street trees in Montevideo city, Uruguay: Tree Hazard Risk Evaluation and Treatment System (THREATS), Quantified Tree Risk Assessment (QTRA) and Best Management Practices - Tree Risk Assessment (ISA BMP). Three assessors with similar experience applied three methods in 36 trees of three widely used genera, totaling 324 assessments and 1,296 data. The methods were decomposed into the components: Likelihood of Failure, Likelihood of Impact, Consequence and Risk Rating. The data were statistically analyzed through a generalized linear mixed model (p<0.05), for the factors: assessor, method, genus, and their interactions. Results showed no significant differences among assessors, but there were differences among methods, specifically for the Likelihood of Impact and Risk Rating components. The ISA BMP method presented higher means in these last two components. Still, this method is suggested for street trees in Montevideo until a more appropriate method is adapted or developed for local conditions. [ABSTRACT FROM AUTHOR]