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<br />2. Check the Trunk <br /> <br />. Watch for Forked Trunks <br /> <br />Forked trunks are signals of <br />potential weakness, especially <br />if one side of the fork grows <br />outward instead of upward <br />like the other. Narrow.angled <br />forks are also prone to <br />infection, often indicated by <br />sap or pitch being exuded. <br />Earl y pruning of one side of <br />the fork can prevent these <br />problems; cables or braces are <br />corrective actions taken bv <br />arborists to strengthen the fork <br />in trees of higher value. <br /> <br /> <br />. What About Balance? <br /> <br /> <br />Leaning or lopsided <br />trees present more of <br />a hazard than those <br />growing vertically, but <br />if a tree has ahv8Vs <br />grown off center, ~it <br />generally is not an <br />undue risk. However, <br />any sudden lean <br />indicates breakage or <br />weakening of support <br />roots and should be <br />cause for alarm and <br />immediate action. <br /> <br />· Look for Signs of Decay <br /> <br />Clues to internal decay of the <br />trunk or large branches are <br />cavities, disfiguration (cankers) <br />and the fruiting bodies of fungi <br />(conks). Sometimes there are no <br />ouhvard indications. Arborists <br />then use one of the methods <br />shown belm\' to check for decay. <br /> <br />According to the USDA Forest <br />Service, internal decay does not <br />automatically render a tree <br />unsafe, VVorking wth pines, the <br />Forest Service determined that if <br />the amount of sound wood <br />surrounding internal rot exceeds <br />that established by the line on <br />the graph, the tree can be <br />considered relatively safe from <br />failure. <br /> <br /> <br /> <br />Canker <br /> <br />Conk <br /> <br />~ 10 <br />" <br />~ " <br />2~ <br />6g 6 <br /><Jl~ <br />~ <br />o , <br />o <br />" <br />z <br />. <br />u , <br />" <br />" <br /> <br /> <br />Relativelv Safe <br /> <br />Danger <br /> <br />16 24 32 40 48 <br />BOLE DIAMETER {INSIDE BARK} <br />{1I>cn.!sl <br /> <br />. Examine Wounds and Cracks <br /> <br /> <br />Drill and Bit <br /> <br />An electric drill and 1/8" <br />bit can reveal rot <br />through changes in <br />drilling speed or ease, <br />and condition of the <br />wood chips extracted. <br /> <br />Any trunk "vound is an opening for <br />decay. \'Vounds extending into the <br />ground, including lightning scars, <br />should be of particular concern and <br />examined regularly. Some cracks, <br />such as frost cracks, have little effect <br />on the strength of a trunk. However, <br />if 1'......0 vertical cracks appear on <br />opposite sides of the tree, it can be a <br />sign of root injury or breakage. It is <br />usually associated with a <br />circumferential separation of \\-'ood <br />internally and is extremely <br />dangerous. <br /> <br />Tools Used by Arborists to Check for Internal Decay <br /> <br /> <br />Increment Borer <br /> <br />A small core of the tree <br />about 1/4" thick is <br />removed and examined. <br />This causes some <br />wounding. <br /> <br />4. TREE cln' USA 8ULLETIN No. IS' National Arbor Day FDundation <br /> <br /> <br /> <br /><> <br /> <br />. <br /> <br />., <br /> <br />~ <br />~. <br />&Ii <br /> <br />Mallet <br /> <br />This method is <br />harmless to the tree <br />but relies on differ- <br />ences in sound as the <br />tree is struck. <br /> <br />Shigometer <br /> <br />This instrument uses a <br />pulsed electrical current <br />to measure the resistance <br />of wood, and thereby the <br />presence of decay. Drilling <br />is necessary. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br />