ARBORICULTURE ARBORICULTU URBAN FORESTRY Volume 32, Issue 6, November 2006 & CONTENTS Formerly the Journal of Arboriculture, 1975 – 2005 (Volumes 1 – 31) www.isa-arbor.com Gregory A. Dahle, Harvey H. Holt, William R. Chaney, Timothy M. Whalen, Jason Grabosky, Daniel L. Cassens, Rado Gazo, Rita L. McKenzie, and Judith B. Santini Decay Patterns in Silver Maple (Acer saccharinum) Trees Converted from Roundovers to V-Trims ..............................................................................................................260 Abstract. Trees growing beneath electrical power lines are oſten subjected to heading cuts made during roundover trimming. Heading cuts create wounds that allow decay to enter the branch, and a decay column will form if the tree does not contain it with compartmental reaction zones. The presence of a sizable decay column may predispose the leader to failure, especially when the tree has been converted from a roundover to a V-trim. The objectives of this study were to quantify the amount of decay in silver maples (Acer saccharinum L.) converted from roundover to V-trims and to develop models to allow utility arborists to estimate the extent of internal decay columns. Parent stems (leaders) were removed from converted trees, cut into 50 cm (20 in) sections, and measured for internal and external decay. Eighty percent of the leaders had internal decay columns beginning within 50 cm (20 in) of the heading cut and internal decay columns were found to be over 21⁄2 times longer than the length of external decay. Mod- els are presented to predict the length and volume of internal decay from external measurements on the leader, including length of external decay. Key Words. Acer saccharinum; Heading Cuts; Line Clearance; Roundover; Utility Arboriculture; V-trimming; Wood Decay. W. Todd Watson and Tomas Martinez-Trinidad Strategies and Treatments for Leafy Mistletoe (Phoradendron tomentosum [DC.] Engelm ex. Gray) Suppression on Cedar Elm (Ulmus crassifolia Nutt.) ...........................................................265 Abstract. Leafy mistletoe, Phoradendron tomentosum (DC.) Engelm ex. Gray, can adversely affect trees growing in urban environments. The eff cacy of several methods for controlling P. tomentosum in Ulmus crassifolia was evaluated in two separate trials. In the first experiment, eight treatments with five replicate trees, 20.3 to 30.5 cm (8.1 to 12.2 in) dbh, were evaluated. Removal of the branch 30.5 cm (12.2 in) below the mistltoe, removal of mistletoe, and treating the branch bark with naphthaleneacetic acid (NAA) or a caulking compound in which mis- tletoe was removed resulted in reduced regrowth of the ectophyte (>90%) aſter 5 months. The use of growth regulator and herbicides (ethe- phon, 2,4-D, and glyphosate) on intact mistletoe plants in experiment 1 did not provide acceptable control of mistletoe. Aſter 29 months, only removal of the branch and caulking over the bark aſter mistletoe removal demonstrated a significant long-term effect on mistletoe mor- tality (40% and 57%, respectively). In the second experiment, a new treatment was evaluated based on the results from the first experiment. The use of NAA and light exclusion (black latex paint) reduced the resprouting of mistletoe by 50% aſter 8 months, but this effect dimin- ished over time. However, 16 months aſter application, NAA and paint significantly reduced regrowth compared with removing mistletoe alone. This study provides strategies to achieve acceptable short-term control and long-term management of leafy mistletoe in urban trees. Key Words. Auxin; Christmas Mistletoe; Herbicide; Parasitic Plant; Pest. Michael F. Galvin Certain Characteristics of Unlicensed Tree Expert Companies Advertising in Maryland, U.S. .............................................................................................................................271 Abstract. In 2005, Maryland’s tree expert licensing law, initially enacted in 1945, was amended to include tree removal as an activity requi ing a tree expert license. The Maryland Department of Natural Resources (MD DNR) sought to identify and communicate with the pote tially affected community regarding the pending changes in the law by a number of means, including a search of companies advertising tree ser- vices in Maryland by online phone listings. The majority of firms (69.91%) found to be advertising tree services online were unlicensed tree experts (UnLTEs). A significant number of those UnLTEs (40%) did not provide full contact information, including a street address, and no current address was available for over 25% of them. Only 21 of the UnLTEs studied had ever been the subject of a complaint to MD DNR and those firms accounted for only 18.2% of complaints MD DNR received regarding UnLTEs during a 10 year period. UnLTEs were found in approximately equal measure in one of three business types: incorporated, unincorporated, or unknown (sole proprietorships, general part- nerships, or noncompliant). UnLTEs are fairly ubiquitous in small numbers across Maryland with the largest concentrations found close to the borders of adjacent states, in the northeast metropolitan area of Maryland’s largest city (Baltimore), and around the state capital (Annapolis). Key Words. Arborists’ Licensing; Commercial Arborists; Tree Experts. ©2006 | International Society of Arboriculture | ISSN:1935-5297
November 2006
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