Agenda - Council - 10/11/1988 - Laserfiche WebLink

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barren, or have extensive wilt (30 percent or more of the tree is wilted). Such trees shall be identified and marked prior to June 25. These high risk trees shall be removed within 20 days of notification of the property owner. (c) Low Risk Elm Trees: Low risk elm trees shah be those trees that show early stages of infection in June or subsequently beyond the 30 percent wilting point. Every reasonable effort shall be made to have ]ow risk trees removed within 20 days of notifica- tion of the property owner, but in no case shall it be later than April 1 of the year follow- ing the appearance of symptoms. (d) Oak Trees: All oak trees within the designated oak wilt control area of the City diagnosed as having oak wilt should be isolated from neighboring healthy oak trees of the same species by chemical or mechanical disruption of common root systems to prevent root graft transmission of the oak wilt fungus. To control the overland spread of oak wilt, the pruning of oaks shall be avoided during the most susceptible period of infection, from April ]5 until July 1. If wounding is unavoidable during this period: as in the aftermath of a storm or when the tree inter- feres with utility lines, a tree wound dressing shall be applied immediately. (1) To prevent the oak wilt fungus from producing spores and to prevent over- land spread of this fungus, any diseased material of the red oak group wilting in July and August of one year shall be declared hazardous the following spring, from April 15 until July 1. Any hazardous oak wood to be used as fuel wood or to be salvaged for other purposes must be debarked or else completely covered by heavy plastic (4 mil or greater) from April 15 until July 1 of the year following the appearance of symp- toms. After this time there is no danger of spore production, and the wood does not need to be covered. Any branch greater than 2" in diameter of the red oak group determined to be hazardous and not to be salvaged shall be disposed of by burning, chipping, or removal to an authorized dump site prior to April 15 of the year following the appear- ance of symptoms. Dead standing red oaks that have advanced beyond the potential for spore production need not be removed except where they constitute a hazard to life and/or property. The City tree inspector will advise accordingly. Stumps of trees of the red oak group removed due to oak wilt shall be complete- ly covered: removed, or debarked to the ground line to eliminate ail possibilities of spore formation and overland disease spread. (2) l.~'hite Oaks: Trees of the white oak group (i.e. white oak, bur oak, bicolor oak) diagnosed as having oak wilt should be isolated by root graft disruption as previously stated. Diseased material originating from such trees will rarely ever support spore formation, and salvaged material therefore will not require special treatment to prevent overland spread. Standing trees of this group showing early symptoms of oak wilt may be saved by removing affected branches. The City tree inspector will advise accordingly. 101.09 Root Graft Disruption (Barriers) at Property Boundaries. (a) If the tree inspector finds that Dutch elm disease or oak wilt threatens to cross property boundaries or disease control area boundaries, the tree inspector may require root graft disruption to prevent the spread of disease in this manner. If plowing or trenching is not possible due to terrain, location, or buried utilities, the tree inspector may require chemical root graft disruption. These barriers will be placed in accordance with current ~echnology and plans as may be designated by the Commissioner of Agriculture, State of Minnesota. (b) The charge, or any portion thereof, for any necessary root barriers may be assessed against the property on which the root barriers are placed. (c) 13eeause oak wilt is a community problem and because oak wilt control may