Oak wilt is a major disease of oaks (Quercus spp.) in Michigan. The fungus, Ceratocystis fagacearum causes the disease by invading the vascular system of the tree. The pathogenic (disease) fungus causes the leaves on the tree to wilt. Wilting is followed by rapid death of trees in the red oak family. In the white oak family, death is usually limited to one or more branches of a tree.
Oak wilt in Michigan may infect red, black, scarlet and pin oaks in the red oak family as well as white, swamp, and bur oaks in the white oak family. The pathogenic fungus may infect the trees when an insect carries the fungus to a recent wound. Alternatively the fungus may infect a healthy tree through the roots, if the roots are grafted onto roots of a nearby infected oak of the same species.
Leaves of red oaks infected with oak wilt begin to turn reddish-to-bronze in color at the edges. The leaves may wilt and curl, then fall to the ground, or they may turn dark brown and remain attached to the branches. Some leaves drop before wilting begins. These leaves are usually greenish and lie stiff and flat on the ground. Wilting generally occurs in July, beginning at the top of the tree and progressing uniformly downward. Many red oaks die after wilting.
White oaks infected with oak wilt generally have leaves that become tan colored and necrotic (dead). Wilting begins from the tip and progresses through the length of the leaves; no distinct line is evident between the necrotic tissues and green tissues. Usually only a few of the branches on an infected white oak will wilt, and on these branches the leaves curl, remaining attached to the tree. Leaf symptoms generally are evident in July.
If pruning takes place during the months of high and moderate risk, pruning wounds should be treated with commercial pruning sealer within a day of pruning. However, pruning of oaks should be done in the winter to avoid infection. The wound paint discourages visitation of the wounds by insects.
Effective oak wilt management programs use a variety of strategies to limit the spread of oak wilt. Some of the practices and policies that can be used in combination to effectively manage oak wilt include the following:
* Information taken in part from Extension Bulletin E-2764, June 2001 By Zachary Blankenheim, et. all., Michigan State University.
Oak Wilt Information Sheet
Oak Wilt In Michigan Information Sheet
Identify, Prevent and Control Oak Wilt
It has been recommended that residents remove and destroy ash trees that have died or exhibit greater than 20% dieback. Proper disposal includes chipping or burying the wood.
he gypsy moth, Lymantria dispar Linnaeus, is one of the most notorious pests of hardwood trees in the Eastern United States. Since 1980, the gypsy moth has defoliated close to a million or more forested acres each year. In 1981, a record 12.9 million acres were defoliated. This is an area larger than Rhode Island, Massachusetts, and Connecticut combined.
In wooded suburban areas, during periods of infestation when trees are visibly defoliated, gypsy moth larvae crawl up and down walls, across roads, over outdoor furniture, and even inside homes. During periods of feeding they leave behind a mixture of small pieces of leaves and frass, or excrement.
Gypsy moth infestations alternate between years when trees experience little visible defoliation (gypsy moth population numbers are sparse) followed by 2 to 4 years when trees are visibly defoliated (gypsy moth population numbers are dense).
The gypsy moth is not a native insect. It was introduced into the United States in 1869 by a French scientist living in Massachusetts. The first outbreak occurred in 1889. By 1987, the gypsy moth had established itself throughout the Northeast. The insect has spread south into Virginia and West Virginia, and west into Michigan (fig. 1). Infestations have also occurred in Utah, Oregon, Washington, California, and many other States outside the Northeast.
The Asian longhorned beetle (ALB) has been discovered attacking trees in the United States. Tunneling by beetle larvae girdles tree stems and branches. Repeated attacks lead to dieback of the tree crown and, eventually, death of the tree. ALB probably travelled to the United States inside solid wood packing material from China. The beetle has been intercepted at ports and found in warehouses throughout the United States.
This beetle is a serious pest in China, where it kills hardwood trees in roadside plantings, shelterbelts, and plantations. In the United States the beetle prefers maple species (Acer spp.), including boxelder, Norway, red, silver, and sugar maples. Other preferred hosts are birches, Ohio buckeye, elms, horsechestnut, and willows. Occasional to rare hosts include ashes, European mountain ash, London planetree, mimosa, and poplars. complete list of host trees in the United States has not been determined.
The woodwasp, Sirex noctilio, and the associated pathogenic fungus, Amylostereum areolatum, are native to Eurasia and North Africa (USDA APHIS & Forest Service 2000) and have been introduced in New Zealand, Australia, South America (USDA Forest Service 1992), and North America (Lang 2006; USDA APHIS 2007; Canadian Forest Service 2005).
The woodwasp is now present across much of New York State, parts of Ontario, and neighboring areas such as eastern Michigan, northern Pennsylvania, and a few counties in Ohio and Vermont. In the upper Midwest, the two could jeopardize decades of careful management of Jack pine (Pinus banksiana) stands aimed at ensuring survival of the highly-endangered Kirtland's warbler. Federal and state agencies spend about $2.5 million annually to manage Jack pine stands in Michigan the benefit of the warbler (Hogrefe pers. comm.).
The woodwasp injects fungus in the tree when the female lays her eggs.
The larvae of this exotic pest are responsible for damaging the tree. It severs the trees' conductive tissues, interrupting the transport of water and nutrients. Adult females lay their eggs in two- and three-needled pine trees, including: Austrian, jack, red, and Scotch pines.
Sirex Woodwasp is not expected to significantly impact healthy landscape pine trees in the state. Its impact on vigorous, well managed pine plantations in Michigan, while not yet fully defined, is likewise not anticipated to be severe.
Asian Longhorned Beetle
Asian Longhorned Beetle Poster
Brown Spruce Longhorned Beetle
Hemlock Woolly Adelgid
Japanese Cedar Longhorned Beetle
Japanese Pine Sawyer Beetle
Rosy Gypsy Moth
Siberian Silk Moth
Two Spotted Oak Borer