Let’s keep things in perspective and rely on those who have worked with, managed, and tracked the spread of the disease as a career. Advanced training is required to accurately diagnose and properly treat the disease. Second, the disease can spread directly from tree to tree via their root connections. Insect Transmission. trees (infection centers) are formed. Oak wilt is a disease caused by fungi that can quickly spread to any trees in the vicinity of the infected trees. Wounds are susceptible to infection for about five days. Kidding aside, once the pathogen has entered one tree, it has the potential to move from tree-to-tree quite readily and efficiently. Live Oaks typically die within six months of infection with some individuals not dying for years. Red Oaks, both Shumard and Spanish, are highly susceptible to the pathogen. According to the latest 2016 update, the pathogen has been found in 26 states, with spread in Texas mostly affecting Central and North Texas. The disease is not rampant or terrorizing all our neighborhoods and was first discovered in the Dallas/Fort Worth area in 1978. weeks after infection by the oak wilt pathogen under some circumstances. A second way how the disease can spread is through natural root grafts, which occur when roots of trees of the same species, such as two red oaks, grow together. Oak wilt is spread from infected to healthy trees in two ways: Through root systems from adjacent infected trees. It is no longer just a renewable resource easily replaced. It is caused by a non-native fungus that is spread by “picnic” beetles, by root to root contact, or by people moving firewood from place to place. It disrupts the flow of water and nutrients by plugging the vessels in the vascular system of the tree. Oak wilt cannot be transmitted by burning infected firewood; however, fungal mats may form on unseasoned oak firewood in storage. Infection centers among live oaks in Although new infection centers do form, it is not fully understood whether it is from the insect spreading the disease, or other methods of transmission not yet discovered or researched. Red Oaks appear to form these grafts as well. By certain kinds of beetles, which carry spores between infected trees, logs or even firewood, and fresh wounds (such as pruning cuts) on unaffected trees. Individual fungal mats produce spores for only a few weeks. The disease can spread long distances (overland) by airborne spores in open wounds caused by wind damage, pruning, or other mechanical damage. Fungal mats form beneath the bark of certain diseased red oaks in spring, beetles. Affected foliage usually drops as this symptom appears, but it is common for symptomatic foliage to remain on the tree. If you have questions, remember there is more to follow next month, on this thrilling subject! Symptoms may develop in the upper crowns of white oaks as with red oaks, but they do not spread as quickly. Mr. Houser is a Dallas native with almost 40 years of experience as a consulting arborist and expert tree climber. Another way to prevent the spread of oak wilt is through appropriate management of firewood. The most important thing you can do to help prevent the spread of oak wilt is to only prune your oak trees between October 15 and April 15 during the winter months when the trees have gone dormant. How does oak wilt spread? Sap-feeding beetles typically fly less than 600 meters from an infected oak to a fresh wound. from mats and visit fresh wounds on healthy oaks. Fortunately, this valuable resource can be protected by utilizing effective management techniques. Oak Wilt spreads in two ways. All Oaks, including Live Oaks and species in the Red Oak family, can be infected by overland spread or root-to-root contact. The Best not to mess with a Texan’s trees! It should be noted that fungal mats are produced primarily in the spring or cooler times of the year, and only on infected Red Oaks in a particular stage of decline. At least for me. The below ground movement occurs when the fungus The most common is called veinal necrosis, a yellowing/browning of the leaf midrib and side veins. To continue learning about Oak Wilt, click here for Part Two of this article. The infected tree reacts by developing tyloses and gums which subsequently restrict the flow of water and nutrients in affected vascular tissues with the result that the tree wilts and subsequently dies (French & Stienstra, 1980). Root grafting is known to occur between Live Oaks and Red Oaks. An aerial photograph (below) shows how oak wilt has spread through live oak trees around the house on this ranch. Root grafting depends on soil texture, terrain, and proximity of oaks to one another. This fungal pathogen has two main means of spreading: by means of an insect vector carrying spores from a fungal mat to a fresh wound, and through connected root systems. The above ground movement is facilitated by a sap-feeding beetle that carries the fungal spores to new trees. How Does Oak Wilt Spread? Once you’ve observed that a particular tree has … If trees become infected, harvest them before the following spring. Oak Wilt is an aggressive disease that affects all species of oak trees, especially red oaks. Trees infected with oak wilt. Recovery from oak wilt infections in red oaks can occur, but is rare. Red Oaks appear to form these grafts as well. Live oaks tend to grow in large, dense groups (called motts) with The Oak Wilt fungus is spread via two ways: above ground and below ground. Root grafting is most prevalent in sandy soil and flat terrain, but also occurs in heavier soils with hillier terrain. Infected Red Oaks typically die within a few months of infection. Once the beetles feed and the fungus moves into the vascular tissue, the tree reacts and tries to wall off the spread of the disease by plugging cells which causes branches to wilt. stumps, and fresh firewood cut from diseased red oaks. So how do you help control the spread of oak wilt? above ground movement is facilitated by a sap-feeding beetle that carries the to 150 ft in any one direction. Oak Wilt most frequently spreads from tree-to-tree by root-to-root contact. All species of Oaks are susceptible, with some species being somewhat tolerant. Insects help spread the spores by feeding on the sap that leaks out of these trees and mixes with the mats. spores for only a few weeks. The oak wilt fungus can spread from diseased trees to healthy trees in several ways. but do not form on white or live oaks. kinds of insects, the most important of which are sap-feeding nitidulid The second, and less common expression, is a heavy and rapid shedding of foliage with individual leaves displaying the symptoms previously mentioned. The fungus is able to spread from infected to healthy trees by underground roots and two groups of insects; the sap and bark feeding beetles. Fungal mats are viable, that is producing spores, for a short period--usually two to three weeks at most. This occurs when fungal spore mats are produced on a dying Red Oak and visited by the suspected insect vector or transmitter, the sap-feeding Nitidulid Beetle. Live Oaks regularly form functional root grafts with other Live Oaks. He is the president and owner of Arborilogical Services, “The Experts Your Trees Deserve.”®, Get a Quote Find out more about how this website uses cookies to enhance your browsing experience. grafted roots, but movement through grafted roots is slower and occurs Leaf discoloration occurs, but the changes are often more gradual than with the red oak group. Uneducated or inexperienced advice can be very costly. commonly formed on standing trees, but they also can develop on logs, How do I recognize it? over shorter distances than in live oaks. Oaks like to be “hooked-up” with each other and swap spit. In Texas, live oak (Q. virginiana) is moderately susceptible to the disease, but because of its tendency to form large, root-connected clones through which the disease can spread… Live Oaks (Quercus fusiformis and Quercus virginiana) follow as a close second. The beetle can carry the spores to a wound on a nearby tree, but the spores can only infect the tree if the wound was fresh and created in the previous 24 to 48 hours. The below ground movement occurs when the fungus travels from tree to tree through interconnected roots. © 2020 Arborilogical Services, Inc - All rights reserved, City of Dallas Urban Forest Advisory Committee. The fungus enters the tree and stops the flow of water as well as elements by plugging the vessels in the vascular system. interconnected roots. The oak wilt fungus is spread overland by insect vectors and by humans Symptoms are often restricted to one or a few branches at a time. How Does Oak Wilt Spread? Oak Wilt is a vascular wilt disease caused by the fungus Bretziella fagacearum. How Oak Wilt Spreads The oak fungus is spread in one of two ways: Fungal spores are either transported to healthy trees by insects, or the fungus travels from a diseased tree to a healthy one via root grafts. The spread of oak wilt occurs both overland and underground. travels from tree to tree through interconnected roots. The fungus invades the water vessels in the sapwood of oak trees, blocks them, and kills the infected trees. Most root grafts form between oaks of the same species; grafts between red and white oaks are very rare.