2000 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. 

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

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. 

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

private foresters, consultants, and nursery inspectors. Information is maintained in a database

that links field observations with extensive GIS datasets. This is the first time specialists and

resource managers will be able accurately track the occurrence of oak wilt in Michigan over

time. This data will be available to the public on the Web in 2001. 

To slow the overland spread of oak wilt, harvesting restrictions have been established on

state land. Cutting forest stands that contain oak trees will be prohibited between April 15

and July 15. This is the period when the sap-feeding beetles responsible for spreading oak

wilt are most active. These beetles are attracted to fresh tree wounds and can infect oak trees

that have been damaged during logging operations. 
2000 Forest Health Highlights - Michigan

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Special Issues

The introduction of exotic organisms is a serious threat to our

native forest ecosystems. Several agencies including the Michigan

Department of Agriculture, the U.S. Forest Service, USDA Animal

and Plant Health Inspection Service, university forest entomologists

and the Michigan Department of Natural Resources are preparing

contingency responses to possible introductions of exotics. Current

planning efforts focus on the Asian longhorned beetle, and the

Hemlock Woolly Adelgid. 

The presence of the beech scale, Cryptococcus fagisuga, was first

confirmed in Michigan in March 2000. The Ludington State Park is

extensively infested, as are several satellite areas within the

Ludington area. Ludington is on the Eastern Shore of Lake

Michigan in the central Lower Peninsula.

Subsequent surveys found beech scale in several areas of

Michigan's Upper Peninsula with associated tree decline and

mortality in isolated areas. Beech Bark Disease is caused by a

combination of two pests, the beech scale and a fungal disease,

Nectria spp. US Forest Service Pathologists, St. Paul, Minnesota

recently identified the fungus currently associated with

Michigan's beech mortality as Nectria galligena. Beech Bark

Disease will continue to spread through Michigan and will have

a profound impact on Michigan's American Beech resource.

Large numbers of an exotic "ladybug" called the Multicolored Asian Lady Beetle,

Harmonia axyridis, invaded homes and other structures in the fall. This exotic species is

native to eastern Asia. Epidemic populations have plagued Michigan homeowners for the

last few falls. Although generally considered a beneficial predator, this was a difficult

concept to sell people removing hundreds of beetles from inside and around their home.

They also disrupt native predator complexes. 

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. 

Sphaeropsis sapinea (=Diplodia continues to affect

open grown and understory red pine in the Upper

Peninsula and in northern Lower Michigan,
2000 Forest Health Highlights - Michigan

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particularly in the northeastern counties. Wind and

hailstorm damage combined with dry growing

seasons in 1998 and 1999 created conditions

favorable for development of the disease.

Sphaeropsis causes shoot death, stem cankers and a

phenomenon called collar rot. Collar rot girdles the

stem at ground level and can kill seedlings and

small trees.

Research at the University of Wisconsin indicates that red pine plantations that develop

symptoms after planting may have been infected at the nursery. There are no effective

controls once a tree is infected with Sphaeropsis. Avoiding stressful conditions, like planting

red pine on poor sites, can help reduce the incidence of infection. Harvesting mature red

pine trees can help reduce infection on young red pine seedlings and saplings growing

below. 

Cold temperatures during the evenings of

May 14-15 and May 20 damaged newly

expanded oak leaves across the Michigan's

northern Lower Peninsula. Temperatures in

the low teens and twenties were recorded

over much of the area. Damage was

widespread but limited to areas of low terrain

where cold air settled. Oaks in the Upper

Peninsula escaped damage because leaves

were still in the unexpanded bud stage. In the

southern Lower Peninsula, oak leaves were

closer to full expansion and largely protected

from damage by the waxy cuticle layer of the

mature leaves. Trees damaged by the freeze

produced new leaves and had fully recovered

by midsummer.

Gypsy moth

defoliation decreased

nearly 50 percent in

2000 to 96,929 acres,

down from 176,626

acres in 1999. The

biological insecticide

B.t. was applied to

another 78,000 acres

as part of the

Michigan Cooperative

Gypsy Moth

Suppression Program.

This also represents a

significant decline

from 1999.

The decrease in gypsy moth numbers is due largely to nucleopolyhedrosis virus (NPV). The
2000 Forest Health Highlights - Michigan

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virus occurs naturally and typically becomes active when gypsy moth populations are high.

In recent years, the virus has also been active in areas where gypsy moth populations are

low. Studies are being conducted at Michigan State University to determine whether the

introduced fungal pathogen Entomophoga maimaiga is also playing a role in the decline of

gypsy moth populations.

Forest tent

caterpillar is at

outbreak levels in the

Upper Peninsula,

where 712,057 acres

of forestland was

defoliation, mostly

pure and mixed aspen

stands. Populations of

this insect in the

Lower Peninsula are

expected to increase

dramatically across the

northern Lower

Peninsula in 2001.

Large aspen tortrix defoliated only 2759 acres of aspen and mixed aspen forests across the

state in 2000, down from 251,826 acres in 1999. 

Jack pine budworm defoliated 18,062 acres in the northcentral Lower Peninsula, up from

10573 acres in 1999. Based on historical information, budworm populations are expected to

begin declining noticeably in 2001. In the Upper Peninsula, where populations have been

low for several years, jack pine budworm defoliation is expected to increase.

Spruce budworm

activity in the Upper

Peninsula has been

spotty for the last few

years with no

significant population

buildup detected.

Larch casebearer, an

insect introduced from

Europe in the late

1800's, attacked

100,774 acres of larch

in the Upper Peninsula

in 2000. Except where

severely weakened,

trees have refoliated

and should recover.

Populations of the casebearer typically don't defoliate the same stands two years in a row.

For more information contact:

Gerald Thiede, 

State Forester 

Forest Health Protection 

Northeastern Area, 

State & Private Forestry 
2000 Forest Health Highlights - Michigan

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P.O. Box 30028 

Lansing, MI 48904 

(517) 373-1275

USDA Forest Service 

1992 Folwell Avenue 

St. Paul, MN 55108 

(651) 649-5244

Updated: January 2001.......

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