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Pest Alerts

Big Bug Cartoon
Not all insects will be this obvious.  Diligence is key to preventing a new infestation. (Source credit: Far Side Comics)

Oak Wilt

Emerald Ash Borer

Gypsy Moth

Asian Long-horned Beetle

Sirex Woodwasp

More Links and Pest Documents

News

 

Oak Wilt in Michigan

Introduction

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.

Symptoms

Red Oak and White Oak leaves showing oak wilt symptomsLeaves 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.

Prevention & Control

Trees have been found to be more susceptible to infection in early June because it is easier to wound trees during spring when the bark is loose. Trees should be protected from wounding in the springtime; in Michigan, oak trees should not be pruned from March through the end of July, and if possible, all pruning should wait to happen until November. A tree has a moderate risk of contracting Oak Wilt between August and October.


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.

Leaf showing pruning risk time periods

Summary of Integrated Oak Wilt Management Strategies

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:

  • Avoid wounding oaks during critical infection periods
    • If pruning is necessary, or if wounds occur on oak trees during the critical infection period, apply tree wound dressings or paints as soon as possible to prevent transmission of oak wilt.
    • Develop and enforce construction ordinances and utility pruning guidelines that minimize wounding of oak trees.
    • Use public service announcements, billboards, and flyers to raise awareness of the dangers of wounding oaks during susceptible periods.
  • Use a vibratory plow line, trench barriers, stump extraction, or chemical disruption of roots to isolate pockets of oak wilt.
    • Communities and neighbors should join together to lower the cost of these tools and achieve more complete and effective local control.
    • Use root graft disruption, use cut-to-the-line practices, and treat stumps with herbicides to greatly reduce or eradicate oak wilt in local areas.
  • Remove and properly treat oaks killed by oak wilt by debarking, chipping, or splitting and drying the wood before the spring following the tree’s death.
    • Do not move infected wood offsite without debarking, chipping, or properly drying it. Do not move or store firewood from infected stands near healthy oaks without proper treatments.
    • Use and enforce city codes and ordinances that mandate removal and treatment of dead oak trees. Such ordinances can significantly reduce the chances for overland transmission of oak wilt.
  • Use appropriate fungicides to protect very high-value trees at imminent risk of infection through root-to-root transmission.

* 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
 

 

Emerald Ash Borer

Overview

Emerald Ash BorerEmerald ash borer (EAB), Agrilus planipennis Fairmaire, is an exotic beetle that was discovered in southeastern Michigan near Detroit in the summer of 2002. It probably arrived in the United States on solid wood packing material carried in cargo ships or airplanes originating in its native Asia. Because ash trees (Fraxinus spp.) in North America have no immunity to the insect, EAB has the potential to wipe out more than 700 million ash trees in Michigan. Since 2002, it has killed more than 30 million ash trees in southeastern Michigan alone. State and federal agencies in Michigan, and researchers in Michigan universities, are working to stop EAB from spreading. This includes the initiation of quarantines to stop the movement of infested ash wood and wood products, research to understand the pest's life cycle and what methods and strategies can control or eradicate it and development of educational and informational materials to help communities detect and deal with EAB infestations.

Property owners are encouraged to remove dead and dying trees of any species. There is an expense connected with removing these trees from private property; however, property owners’ potential expense associated with doing nothing could be far worse. These potential costs include death, injuries, damage to your home, damage to neighbors’ homes, and damage to vehicles. Property owners are responsible for damage that occurs as a result of falling trees, and property insurance may not cover damage caused by dead or dying trees.

Identification and Information

Where to get more information

For information on ash-wood quarantine areas, approved disposal sites, use of ash wood and more, visit these sites and search on emerald ash borer:

Historical Information

The City of Novi Forestry Division took a proactive approach in managing the Emerald Ash Borer (EAB) by monitoring our street ash tree population. In July of 2003, we completed a comprehensive inventory of the city’s 2,500 street ash trees. The purpose of this inventory was to assess the health and maintenance needs of the ash trees. The following information was collected: location, size, health, and maintenance needs. The data collected has been used to develop an EAB management plan as well as create and prioritize tree work orders.

Forestry crews have been actively removing ash trees on public property throughout Novi for the last few years. The main message is that tree diversity is the key aspect to having a healthy and sustainable urban forest. In the few years, the City of Novi has been planting a wide diversity of tree species in effort to prevent this devastation from happening in the future. Rows of the same tree species lining streets are no longer desirable. Areas where the same tree species are spaced closely together make it easier for insects and diseases to spread. 
For more information, please visit the following websites:

Emerald Ash Borer Facts

Ash Tree LeafWhat does an Ash tree look like?:
The tree has light-gray bark, which is smooth in younger trees and rough and scaly in older ones. The tree also has compound leaves, which are divided into five to nine lance-shaped leaflets.

How to identify the Emerald Ash Borer Problem:

  • Initial thinning and/or yellowing of the foliage
  • Development of suckers from the trunk or branches
  • Woodpecker injury
  • Tiny D-shaped emergence holes on the trunk or branches
  • Gradual death of the tree
  • "S" tunneling beneath the outer bark
  • Dieback/Death
  • Bark splitting

Emerald Ash BorerWhat does the Emerald Borer look like?

Adults are metallic green in color and approximately 1/2 inch in length. Larvae are cream-colored and are found in or under the bark.

What you can do if you have an infected tree:

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.
Is there treatment for the Emerald Ash Borer? There are some insecticide treatments available, which may prevent further decline. Insecticide Options for Protecting Ash Trees from Emerald Ash Borer - Purdue University

 

Gypsy Moth

Gypsy MothThe 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.

For more information, visit these sites and search for gypsy moth:

 

 

Asian Long-horned Beetle

Asian Longhorned BettleThe 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. A complete list of host trees in the United States has not been determined.

For more information, visit these sites and search for Asian longhorned beetle:

 

 

Sirex Woodwasp

Sirex WoodwaspThe 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.

For more information on this pest, please visit:

 

More Links and Pest Documents

Links

Sudden Oak Death
Hemlock Wooly Adelgid
Sirex Woodwasp
Beech Bark Disease
Giant Hogweed
Other Pest Alerts

Documents

 Asian Longhorned Beetle
 Asian Longhorned Beetle Poster
 Brown Spruce Longhorned Beetle
 Giant Hogweed
 Hemlock Woolly Adelgid
 Japanese Cedar Longhorned Beetle
 Japanese Pine Sawyer Beetle
 Nun Moth
 Rosy Gypsy Moth
 Siberian Silk Moth
 Sirex Woodwasp
 Two Spotted Oak Borer

News

For up-to-date news on forest health in Michigan, visit the webpages below:

You can also sign up for Michigan State University Extension News Digests. You can choose specific topics you wish to receive information about. You can do that through their webpage: