2001 Forest Health Highlights - Michigan

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The Resource

Forests comprise 53% of the land area of the state, or about 19.3 million acres. These

forests are a critical component of Michigan's environment and economy for the

recreational opportunities and the products they provide. Forestry related industries and

manufacturing employ 150,000 people statewide and annually contribute $9 billion to the

state's economy. Additionally, forest-based tourism and recreation support 50,000 jobs

and add $3 billion to Michigan's economy. Michigan's forests contribute to clean air,

water, and reduce soil erosion.

Special Issues

The introduction of exotic organisms is perhaps the most serious health threat to our

native forest ecosystems. State and federal agencies are preparing contingency responses

to the possible introduction of exotics such as the Asian longhorned beetle, the

Hemlock Woolly Adelgid, the Balsam Woolly Adelgid, and Sudden Oak Death.

A Hemlock Woolly Adelgid Quarantine now restricts

movement of eastern hemlock into Michigan from infested

counties of other states. All eastern hemlock shipments

require a phytosanitary certificate. Two infested shipments of

hemlock were intercepted in 2001. Both shipments were

made prior to enacting the HWA quarantine. These

introductions were eradicated through immediate and

aggressive action by the Michigan Department of Agriculture.

Beech bark disease (BBD) was detected in the spring of 2000. The

interaction of an exotic scale insect (Cryptococcus fagisuga) and native and

exotic canker-causing fungi (Nectria spp.) cause beech bark disease. Once

infected by the fungus, trees usually

decline and trunks may break at canker

sites. Two state parks are currently

removing many infested beech because

of the hazard posed by these potentially

dangerous trees. The disease has

significant implications for wildlife in the
2001 Forest Health Highlights - Michigan

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northern hardwoods where beechnuts are

the major or only mast crop. As the

disease progresses, the majority of large, mature trees

will die. Salvage or pre-salvage operations are only

recommended for heavily infested stands. A system of

monitoring plots is being established to 1) Delineate the

advancing & killing front of the scale; 2) Identify &

quantify tree, stand & site factors influencing rates of

decline; 3) Identify potentially resistant trees; 4)

Measure impacts of native & exotic Nectria; 5) Study

regeneration potential of beech & other tree species; 6)

Evaluate wildlife impacts; and 7) Revise beech

productivity models to ensure the affected forest

resource is sustainably managed.

Sudden Oak Death - poses a real threat to Michigan's forest resources. We are currently

conducting a risk analysis to determine the exact nature of this threat. This will be an

ongoing effort, until this potentially devastating new disease is better understood. For

more information visit http://www.suddenoakdeath.org

In the past decade Sphaeropsis

(Sphaeropsis sapinea) has been

increasingly associated with damage

and mortality of red and jack pine in

Michigan. Prior to the 1980s, damage

by the pathogen was rare in the Lake

States. Increasing damage by the

pathogen has been correlated to the

increasing prevalence of a more

virulent and more aggressive form

(morphotype), called Type A. There is

evidence that the Type A S. sapinea

may be an introduced species that is

replacing the presumptive native and

less virulent, less aggressive Type B.

Severe damage is often associated

with site stresses, and drought years like 2001 when 1,174 acres of affected plantations

were detected. Research efforts are currently underway to evaluate the presence of TypeA S. sapinea in Michigan red and jack pine.

An exotic plant receiving much attention in the UP is garlic mustard (Alliaria petiolata).

Garlic mustard poses a severe threat to native forest plants communities. Garlic mustard

completely displaces native hardwood wildflower communities. A few small introductions

have been detected in the Eastern UP. This is one of several exotic plants of concern. A

new interagency council, the Michigan Invasive Plant Council (MIPC) has been formed to

address exotic plant issues and actions in Michigan. For more information visit the MIPC

website at http://www.msue.msu.edu/mipc. 

Incidence of the vascular disease oak wilt continues to increase from 2000 levels in

several areas around the Upper Peninsula and the northern Lower Peninsula of Michigan.

In response, a statewide oak wilt initiative is underway in cooperation with the Michigan
2001 Forest Health Highlights - Michigan

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Department of Agriculture and the Michigan Department of Natural Resources. This effort

is focusing on detecting new and established oak wilt pockets across the state, and

working with local communities to suppress the spread of infection centers. In addition, a

7-state consortium is forming to address research and management issues in the

Midwest. 

Detection is being accomplished through ground surveys conducted by state, federal, and

private foresters, consultants, and nursery inspectors. For the first time, the public will be

able to view maps and information about the status of oak wilt in Michigan by pointing

their browser to the Report a Forest Pest feature on the Michigan DNR Forest Health

website at http://www.michigan.gov. 

To slow the overland spread of oak wilt, harvesting restrictions are being

exercised on state land. Forest stands with oak trees are not being cut

between April 15 and July 15 in areas where the risk of oak wilt is high.

These dates mark the period when the sap-feeding beetles responsible

for spreading oak wilt are most active. These small (1/4-inch long) beetles

are attracted to fresh tree wounds and transmit spores to oak trees that

have been damaged during logging operations. 

Multicolored Asian lady beetle (Harmonia axyridis) continued to

enter homes by the hundreds in the fall. Based on the number of calls

and publicity, populations were significantly down from 2000. This

lady beetle is one of many exotic ladybeetle purposely released in the

U.S. since the early 1900's as a biological control of selected insect

pests. 

The Larch Casebearer defoliated tamarack (eastern larch) in the central Upper Peninsula

for the second consecutive year. Larch casebearer is an exotic insect introduced to the

Lake States since the early 1900's. Introduced parasites have effectively protected the

tamarack resource. 

Public agencies and private groups are creating a Michigan Invasive Plant Council. The

Council's mission is to protect Michigan from the threat of invasive plants like purple

loosestrife, leafy spurge, spotted knapweed and garlic mustard by 1) Raising public

awareness about the spread and impact of invasive plants; 2) Facilitating the exchange of

information concerning management, control, inventory and monitoring of invasive plants;

3) Providing a forum for all interested parties to discuss issues relating to invasive plants;

4) Serving as an educational, advisory and technical support council for all aspects of

invasive plants and related issues; 5) Preventing future introductions of new invasive

plants; and 6) Developing, maintaining and publishing a council-reviewed invasive plant

species list. 

Other Michigan Forest Health Issues 

Gypsy moth (Lymantria dispar) populations continued their downward trend. This marks

the first year since the mid-1980's that no gypsy moth defoliation was detected during

the annual statewide aerial survey. In the Upper Peninsula, ground surveys indicate that

the moth continues it's westward movement. All of Michigan is now federally regulated.

The first gypsy moth defoliation in the Upper Peninsula could occur in an oak area near

Gladstone in the South-central UP in the next few years.

A buildup of jack pine budworm (Choristoneura pinus pinus)

populations began in the Eastern UP this year. The epidemic

will spread westward affecting

most of the UP jack pine resource

in the next 3-4 years. In the

Lower Peninsula, jack pine

budworm numbers rebounded

somewhat in the northcentral and

northeastern areas of the region.

This follows a widespread collapse
2001 Forest Health Highlights - Michigan

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in 2000 of an outbreak that began

in the 1997. Budworm populations

will be monitored in 2002. Stands

that were defoliated previously and

show signs of heavy population

buildup are at high risk of mortality. These stands will be

harvested. Chemical treatment of jack pine budworm infestations is rarely cost-effective.

Isolated pockets of spruce budworm, Choristoneura fumiferana, were detected on 3,600

acres of spruce/fir in Michigan's Upper Peninsula.

The locust leafminer (Odontota dorsalis) made an

unusual appearance in the southwest Lower

Peninsula. This insect emerges as the leaves are

developing and lay small clusters of overlapping eggs

on the lower surface of the leaf. On hatching, the

larvae form a common mine that is initially white but

turns brown as it become larger. Large areas of black

locust were affected. Fortunately, parasites of the

larvae and pupae of this leafminer reduce high

populations before trees are damaged or killed.

The Forest Tent Caterpillar (FTC) (Malacosoma disstria)

defoliated 11.5 million acres. The FTC is a native leaf-feeding

caterpillar. Epidemics occur about every 10-15 years in the

Great Lakes region, and last for 2-4 years. FTC prefers to

eat aspen leaves in the UP though it also readily consumes

paper birch, green and white ash, basswood, oak and willow

leaves. Sugar maple is readily consumed only in the

Northern Lower Peninsula. FTC can defoliate trees for several

years with little ill effect. This is especially true for years with

average or above average rainfall. Parasites were abundant in this year's populations,

signaling a likely significant population reduction in these areas next year.

Tamarack, also known as Eastern Larch

(Larix laricina) were defoliated by the larch

casebearer (LCB) (Coleophora laricella).

Brown trees were evident in many areas of

the Central and Eastern U.P. This is an

introduced species from Europe, first

recorded in Massachusetts in 1886. It now

occurs throughout most of the range of

tamarack in North America. The LCB is a

serious defoliator of tamarack of all ages.

Defoliation for two or more consecutive years

can cause tree decline and mortality.

Populations generally collapse after a single
2001 Forest Health Highlights - Michigan

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year of damage thanks to two parasites

imported from Europe. These parasites have widely established and are believed to be the

reason that outbreak severity has diminished throughout North America.

In the Lower Peninsula, late spring frosts damaged new

growth on oak trees in low-lying areas. Some oak stands

were affected for the second consecutive year. Most trees

refoliated by late June. Wet, cool spring weather led to a

widespread outbreak of hardwood anthracnose across

the Lower Peninsula in 2001. This disease was common on

white oak, ash and maple. Many homeowners confused the

symptoms of this disease with oak wilt. Because

anthracnose is usually isolated to the leaves, trees rarely

suffer long term effects. Raking and bagging infected

leaves may help reduce the spread of the disease.

For more information contact:

Gerald Thiede, 

State Forester 

P.O. Box 30028 

Lansing, MI 48904 

(517) 373-1275

Forest Health Protection

Northeastern Area, 

State & Private Forestry

USDA Forest Service 

1992 Folwell Avenue 

St. Paul, MN 55108 

(651) 649-5244

Updated: February 2002

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