100 Haugen et al.: Efficacy of PBZ Soil Application for Utility Right-of-Way Pruning Longer branches are more challenging to extricate from the canopy (Mann et al. 1995). Aſter initial cuts are made, there is an increased risk of workmanship error, with longer branches potentially resulting in power interruptions as well as a greater challenge for managing larger branches than smaller branches on the ground for efficient branch processing (Ball and Vosburg 2010). Working with untreated branches averaging 285.8 cm in length versus 162.1 cm is dramatically different for the arborist using an aer- ial bucket (Table 6). This reduction leads to both a reduction in cost of labor for pruning and process- ing time, as well as a reduction in potential injuries while on a job site (Table 6) (Ball and Vosburg 2010). Ideally, the timing of PBZ application to live oak trees is between 90 days pre-prune and 90 days post- prune (Table1; Table 2; Table 3; Table 4; Table 5; Table 6). Although statistically significant differences exist between the results from application times of PBZ, the maximum of 12.8% difference in reduction of branch growth may be negligible for the end user, indicating greater flexibility in application timing (Table 2). Additionally, due to the inherent subjec- tivity in the pruning of the trial trees there is a high level of variability in the branch re-growth data. Paclobutrazol is a tool that can predictably reduce the vegetative re-growth on Q. virginiana trees pruned for utility line clearance. The application of this tool results in reduced vegetative growth lead- ing to reduced pruning and chipping time by line- clearance crews. This reduction in time decreases the maintenance cost necessary for pruning and increases the safety of pruning crews. The timing of PBZ application on live oak trees in relation to the pruning event, though statistically significant, would not drastically affect operation efficiency on live oak trees in Louisiana. However, the savings in labor for the pruning and processing of the biomass is signifi- cant when PBZ is utilized compared to no application of PBZ. Further research is required to understand how the severity of the initial pruning event relates to the quantity and length of resurgent growth. Acknowledgments. The authors wish to thank Brandon Hughson and Erik Gabbey from Rainbow Treecare Scien- tific Advancements, Jim Neeser from the Davey Resource Group, and John Dean from Entergy Louisiana, LLC. for their assistance and coordination of field work. This research was funded, in part, by The TREE Fund, and the authors sincerely thank The TREE Fund for their generous support of this research project. LITERATURE CITED Bai, S., W. Chaney, and Y. Qi. 2004. Response of cambial and shoot growth in trees treated with paclobutrazol. Journal of Arbori- culture 30(3):137–145. Ball, J., and D.F. Blair. 2009. Chipper accidents are more common than reported. Tree Care Industry pp. 8–13. Ball, J., and S. Vosburg. 2010. A survey of United States tree care companies: Part I: Safety training and fatal accidents. Arbori- culture & Urban Forestry 36(5):224–229. Burch, P.L., and R.H. Wells. 1995. Tree Growth Evaluated 10 Years Aſter Application of Paclobutrazol Tree Growth Regulator. Down to Earth. Campbell, R.J. 2012. Weather-Related Power Outages and Electric System Resiliency. Washington, D.C.: Congressional Research Service. Dayinian, M. 1993. Wood Chip Management. Arborist News 2(2):9–13. Entergy. 2014. Distribution Vegetation Management Line Clear- ance Specifications. Louisiana: Entergy. Gillespie, A., and W. Chaney. 1989. Process modeling of nitrogen effects on carbon assimilation and allocation—A review. Tree Physiology 5(1):99–112. Goodfellow, J.W., and T.W. Michael. 2012. Public Regulatory Authority Review of the Public Service Companies’ Response to 2011 Storms. Connecticut: Townsley Consulting Group, LLC. ISA. 2002. Utility Specialist Certification Study Guide. Interna- tional Society of Arboriculture, Champaign, Illinois, U.S. 84 pp. Jacobs, K., and L. Berg. 2000. Inhibition of fungal pathogens of woody plants by the plant growth regulators paclobutrazol. Pest Management Science 56(5):407–412. Mann, M., H.A. Holt, W.R. Chaney, W.L. Mills, and R.L. McKenzie. 1995. Tree growth regulators reduce line-clearance trimming time. Journal of Arboriculture 21(4):209–212. Martinez-Trinidad, T., W.T. Watson, and R.K. Book. 2011. Impact of paclobutrazol on root-pruned live oak. HortTechnology 21(1):46–50. ©2016 International Society of Arboriculture
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