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1.Every year, Minnesota loses a large number of oak trees to oak wilt. Oak <br />wilt is caused by a non-native fungus that affects all types of oaks found in <br />Minnesota. Typically, these oaks can be categorized as the red oak family <br />(includes red oak, pin oak, and northern pin oak) and the white family <br />(includes white oak, bur oak, and swamp white oak). The “high risk” <br />timeframe for potential oak wilt infection is generally April through June, <br />but infection can occur anytime an oak tree is not dormant. <br />2.The oak wilt fungus travels within a tree through its water-conducting <br />system. In the red oak family, wilting begins at the top and outer portions <br />of the tree. In the white oak family, wilting of the canopy can be more <br />scattered. Oak leaves will wilt from the tips inward toward the base of the <br />leaf. The fungus quickly affects the red oak group, with complete wilting <br />and defoliation in as little as four weeks. The disease progresses more <br />slowly in the white oak group, with death often occurring over a growing <br />season or longer. <br />3.The fungus spreads below ground through connected (grafted) roots and <br />above ground by certain insects. Below the ground, roots from trees of the <br />same species can fuse or graft together. Oak wilt moves within a tree, both <br />up into the canopy and down into the root system, and if it encounters <br />grafted roots, it can easily move into the adjacent tree. Above ground, the <br />fungus is spread by picnic beetles as they feed on sap flowing from fresh <br />wounds on oak trees (due to storm damage, pruning activities, etc.). <br />4.There are ways to minimize the spread of oak wilt. They include <br />mechanically cutting grafted roots between diseased and healthy oaks <br />and/or chemically injecting trees to protect against infection. If oak <br />wilt is present, injections should be repeated every other year for three <br />injection cycles over six years. Avoid pruning oaks between April and <br />June (later if possible) and do not transport infected firewood to other <br />locations (e.g., don’t bring it up to the cabin). If pruning of an oak tree <br />is absolutely necessary during the “high risk” period, seal the wound <br />immediately with a product such as shellac or a water-based paint. <br />5.Proper disposal of infected wood is essential. Options include debarking <br />the trunk, chipping the wood or cutting it into firewood-sized lengths <br />and stacking and covering with 4-6 mil. clear plastic for an entire growing <br />season. The edges of the plastic should be buried in the ground several <br />inches to create a tight seal and this should be in place before April 1. <br />Five Things to Know <br />About Oak Wilt <br />in the City of Ramsey <br />If you have questions or concerns about your trees, <br />please contact Senior Planner Chris Anderson at <br />763-433-9817 or canderson@cityoframsey.com. <br />What to look for if you suspect <br />your trees have oak wilt <br />Spore (or pressure) pads form on the <br />wood just beneath the bark. These can <br />crack the back and emit a sweet aroma <br />that attracts insects. <br />Oak wilt symptoms include leaves wilting <br />from the edges inward and from the top of <br />the tree canopy downward.