|Oak Wilt / Live Oak Decline
THINGS YOU SHOULD KNOW ABOUT LIVE OAK DECLINE/OAK WILT
Fall (October) is a great time to plant trees, but it is also important that we protect the trees that we have. The major disease threat to live and red oak trees in our area is oak wilt. The disease is expressed in red oaks (Texas, Schumard, Blackjack) by a healthy tree showing fall-like coloring in late spring or early fall and dying. The live oak usually dies slower (2 months to two years after showing initial symptoms), an agonizing time for the tree's owner because once symptoms are evident there is nothing to do to save the tree. Watch for the characteristic veinal necrosis on leaves from infected live oaks. The area on the veins is red, brown, or yellow and the area in between is green.
Oak wilt is easy to prevent and difficult to treat. Because the disease travels through the interconnected roots of live oaks at 100 feet per year once the infection is in a neighborhood, you must trench a break in the roots around the infected trees (plus 100 feet). Trenching is disruptive, expensive, and difficult in an urban neighborhood. Everybody must cooperate and tolerate the removal of fences, shrubs, outbuildings, etc.
Individual trees can be protected with the chemical Alamo injected by a trained applicator but it is also expensive (approximately $7 to $18 per inch of diameter). It protects the tree from infection but does not stop the spread of the disease or cure the infected tree.
Prevent the diseases spread by painting all wounds on live oaks and red oaks. Keep a spray can of pruning paint in your garage to immediately paint any wound on your trees. Pruning, weed-eater and machinery cuts on the trunk and exposed roots are especially susceptible to infection. Sap beetles carry the disease spores from an infected red oak to the wound on a live or red oak. The paint stops them. Every minute you wait after the wound occurs increases the chance of infection. The first two days are most critical. We no longer say there are windows of safety because of cold weather or hot weather. Central Texas weather is too unpredictable and changeable--paint every wound all year long.
Firewood from red oaks can also rarely be a source of the oak wilt infection. Protect your neighborhood by managing firewood to avoid infection. It is not necessary to reduce the use of the fireplace in order to stop the spread of oak wilt. Smoke from infected wood burning is NOT a threat! The fungus is destroyed by heat and will not even survive in dry firewood. If you utilize red oak firewood, try to purchase wood from trees that have not been infected or killed from oak wilt. Only wood that has been cured for an entire summer should be stored in the vicinity of uninfected red or live oaks. If you bought oak firewood for this winter and are unsure of its age or origins, use it up before spring.
Texas A&M Plant Pathology http://cygnus.tamu.edu/Texlab/oakwilt.html http://cygnus.tamu.edu/Texlab/trees/tree4.html, for more information.) PLANTanswers | Aggie Horticulture |