Michigan 2003 Forest Health Highlights

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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

Michigan’s newest exotic forest pest, the Emerald Ash Borer (EAB) (Buprestidae: Agrilus

planipennis), attacks all ash (Fraxinus spp). At present EAB predominately infests 13

counties in Southeast Michigan (Figure 1.) These counties are under a Michigan

Department of Agriculture (MDA) quarantine. The EAB Quarantine prohibits the movement

of all firewood and ash materials of any type including logs and branches unless chipped

to 1” or less. Additionally, there is a one-year moratorium on the sale and movement of

ash nursery stock into or within Michigan’s Lower Peninsula.

Estimates place the EAB toll to date in Southeast Michigan at 6 million trees infested or

dead. Michigan is home to an estimated 700 million ash trees.

Several small EAB populations known as outlier populations were detected to the north

and west of the generally infested areas in 2003. The MDA is actively evaluating and

taking actions to eradicate outliers which pose a significant breach of containment

strategies. Emerald Ash Borer strategies are currently focused in five main program areas:

1) insect survey, 2) regulatory activities, 3) public education, 4) urban and rural forest

restoration and 4) active management of outlying isolated populations. For further

information on these and other activities visit the EAB web site at:

http://www.emeraldashborer.info.

Michigan DNR 2004 EAB Plans include a statewide detection survey in cooperation with

the US Forest Service, St. Paul, MN. Trap trees will be used to survey high risk areas

throughout the state. Trap trees are ash trees that are girdled. Girdled trees have proven

to be ten times more attractive to adult beetles.

The purpose of this survey is to detect EAB populations currently below detectable limits

(e.g. below-damage threshold populations) which may exist in other parts of Michigan.
Michigan 2003 Forest Health Highlights

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Selected survey sites have a significant ash resource and a significant numbers of visits

from people living in EAB infested counties.

The Michigan State Parks Visitor Database was used to select State and Federal camping

sites at high risk of movement of EAB infested firewood. State Park visitors from EAB

infested zip code areas in SE Michigan were tracked for the period of mid-April through

Mid-August for the years 2001 to 2003. Cumulative visitor days were then used to rank

State Parks from most to least frequently visited (Figure 1).

Survey locations cover the entire state outside of the 13 quarantined counties. In total

116 sites were selected, 46 State Parks, 47 State Forest Campgrounds and 23 USFS

Campgrounds.

A Hemlock Woolly Adelgid quarantine continues to restrict

movement of eastern hemlock into Michigan from infested

counties of other states. All eastern hemlock shipments

require a phytosanitary certificate. This follows the

interception of the insect at two Michigan nurseries in 2000.

Rapid early detection surveys for the adelgid have been

conducted statewide in hemlock stands and in areas adjacent

to nurseries since 2001. No hemlock woolly adelgids were

found in 2003.

Beech Bark Disease (BBD) is a serious threat to Michigan’s 7.2 million acres of MapleBeech-Birch type. This represents 138 million beech in all size classes. Of these, 15 million

larger beech in the > 9 inch diameter class are highly vulnerable to damage. BBD is

greatly impacting the beech resource in areas infested with beech scale for 10 years or

more (Figure 1). Two thousand acres of beech forest land within the Luce County in the

Upper Peninsula are currently being salvaged.
Michigan 2003 Forest Health Highlights

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Michigan State University is studying the Effects Of Beech Bark Disease On Forest

Resources And Wildlife Habitat in Michigan. They are quantifying impacts of beech bark

disease on stand composition, productivity, and wildlife values. They are also studying the

relative abundance and distribution of the three causal fungi (Nectria galligena, Bionectria

ochroleuca, and N. coccinea var. faginata). To date they have discovered:

Canopy dieback was extremely variable within and among stands

Trees with greater than 30% dieback occurred more commonly in stands with heavy

beech scale, regardless of beech density.

No apparent patterns in canopy dieback occurred in relation to varying beech

density.

The University of Michigan continues expand their Beech Bark Disease Monitoring &

Impact Analysis System. Results to date:

Scale likely arrived in Michigan ~1985

Heaviest in two epicenters are in Luce (Upper Peninsula) and Mason Counties (Lower

Peninsula)

202 Plots - 36% infested

Mortality is only high in stands with high scale densities

Killing front plots: 5% dead basal area in 2001 to 18% dead basal area in 2003

Foliage transparency - 38% higher from 2001 to 2003

Crown dieback – 66% greater from 2001 to 2003

The Northeastern Research Station, USDA Forest Service, Delaware, OH is identifying

mechanisms of Beech Bark Disease Resistance with the goal of producing resistant

seed and seedlings. They have successfully crossed resistant parents and resistant &

susceptible parents. The resulting 1,600 seedlings have been outplanted. They are

currently conducting insect challenge experiments to determine the resistance phenotype

of cross progeny.

The Michigan DNR and Department of Agriculture have been on the alert since the first

reporting of Sudden Oak Death (SOD)(Phytophthora ramorum). The MDA inspects

rhododendrons in nurseries for SOD, and has not detected SOD to date. The DNR is

educating public and private resource professionals to increase awareness and ability to

recognize SOD symptoms. Michigan will cooperate with the proposed national baseline

survey of Phytophthora species in oak forests in 2004.

Sphaeropsis Canker (Sphaeropsis sapinea) which plagued many red and jack pine areas

in Michigan during the drought of 2000 and 2001 was not noticeable in 2003. Many of the
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hardest hit plantings in 2000-2001 were on drought susceptible, light soils.

Michigan DNR funded research titled “Sphaeropsis sapinea in diseased Red and jack pine

stands of Michigan” by Gerard Adams, Michigan State University reported that the high

mortality of red and jack pines following drought stress was caused by the Type B strain

and not the more virulent and aggressive introduced Type A strain of S. sapinea.

Earlier studies of red and jack pine seedlings in DNR nursery ground beds revealed that

most plants had endophytic infections with Type A strains. The next step is to examine

such seedlings after out planting to determine whether Type A strains continue to

predominate in tree tissues.

Eastern Larch Beetle (Dendroctonus simplex) populations

in Eastern and the South Central Upper Peninsula declined

in 2003. This bark beetle became epidemic in tamarack

(Larix laricina) stressed trees from the drought of 2000-

2001 and repeated defoliation by the Larch Casebearer

(Coleophora laricella).

The threat of Invasive Plants to Michigan’s Forest

Resources is gaining much attention in many public and

private sectors. The Michigan Invasive Plant Council created

in 2001 continues to seek partnerships and expand its

service. Visit the MIPC web site at:

http://forestry.msu.edu/mipc/

About 30 acres of Garlic Mustard (Alliaria petiolata) were

treated with herbicides and prescribed fire in Mackinac

County. Public agencies are cooperating in an effort to keep

garlic mustard from establishing in the Upper Peninsula.

During the spring of 2003, the Michigan DNR and Seney

Wildlife Refuge joined forces to combat glossy buckthorn

(Rhamnus frangula) adjacent ownerships along Highway M77. Treatments included herbicides and use of brush saws.

Reports of Giant Hogweed, Heracleum mantegazzianum, in the Upper Peninsula have

initiated education and detection efforts to keep this invasive plant from gaining a

foothold.

Incidence of the vascular disease oak wilt continues to increase

from 2002 levels in several areas around the Upper Peninsula

and the northern Lower Peninsula of Michigan. 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 sapfeeding 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
Michigan 2003 Forest Health Highlights

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damaged during logging operations. Under a grant from the USFS

State & Private, efforts have begun to eradicate oak wilt from

Menominee and Dickinson counties. This work is also being

funded by MDNR Wildlife and the

Wildlife Habitat Improvement Program (WHIP). Oak wilt

pockets are being isolated with root graft barriers and the

wood burned or chipped to destroy the fungus.

The Red-Headed Pine Sawfly (Neodiprion lecontei) is an

important defoliator of young red and jack pines. Building

sawfly populations were detected in many areas of the

Eastern UP and the Northern Lower Peninsula in 2002.

Dimlin 4L was used to protect 1,321 acres of plantation red

pine in 2003.

Gypsy moth (Lymantria

dispar) populations continue on an upward trend statewide.

This follows a long period of population decline that began

in the early 1990’s and culminated in 2001 when, for the

first time in over a decade aerial surveys detected no

defoliation in the state. Since then, egg mass numbers

have been increasing steadily and defoliation was locally

heavy in some northern Lower Peninsula and Upper

Peninsula counties. A total of 38,119 acres were defoliated

statewide.

The Jack pine budworm (Choristoneura pinus pinus) is

considered the most significant pest of jack pine. Stands

older than 45 years that are growing on very sandy sites

and suffering from drought or other stresses are very

vulnerable to damage. Tree mortality and top kill resulting

from budworm defoliation creates fuel for intense wildfires.

Harvesting and other management activities can minimize

budworm-caused tree mortality and reduce the threat of

damaging wildfires, and create suitable conditions for jack

pine regeneration. A buildup of jack pine budworm

populations began in the Eastern UP in 2000. In 2003,

131,809 acres of jack pine were moderately to heavily

defoliated. This epidemic will spread westward affecting

most of the UP jack pine resource in the next 2 to 3 years.
Michigan 2003 Forest Health Highlights

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In the Lower Peninsula, jack pine budworm numbers rebounded in 2003 after having

declined since 2001. Approximately 196,000 acres were defoliated. Stands that were

defoliated previously and show signs of heavy population buildup are at risk of mortality.

These stands will be harvested. Chemical treatment of jack pine budworm infestations is

rarely cost-effective.

Forest Tent Caterpillar (FTC) (Malacosoma disstria)

defoliated 167,000 acres in 2003. Affect areas were

primarily counties bordering Wisconsin in the south central

Upper Peninsula. This is the tail end of a 4-5 year epidemic

which defoliated 11.5 million acres in its peak year, 2001.

Spruce Budworm was active in Marquette and Schoolcraft

counties in Michigan’s Upper Peninsula. Areas of light

budworm defoliation have been visible for the last few

years.

During 2003 the Michigan DNR embarked on several GIS

projects, providing new tools to resources managers for

evaluating potential forest health impacts across the

landscape. The most significant of these projects is the

construction of a set of forest habitat type maps for

northern Michigan. The system, developed by Dr. John

Kotar and Timothy Burger of the University of Wisconsin in

cooperation with the Michigan DNR, is “...based on the

identification of repeatable patterns in the composition of

understory vegetation”. Once an area is classified,

assessments can be made about the potential for forest pest infestations and the affect

these pests will have on the forest. Through the use of soil, geomorphic and climatic maps

a forest habitat type map was created for northern Michigan, allowing resource managers

to assess forest health risks and impacts in individual forest stands across the state. Maps

like this will continue to play a significant role in long-range planning and in enabling

foresters to maintain healthy forests. The draft map can be seen at:

www.mcgi.state.mi.us/forestHabitatTypes/

To determine the potential risk for emerald ash borer across the lower 48 states a multicriteria model was constructed. This type of computer model provides a process for

combining multiple criteria based on the importance or influence of each factor. The EAB

risk model provides a tool for assessing where EAB is likely to occur in the future.

Our on-line mapping system for forest pest infestations is in its second year. In addition

to pest information mapped annually as part of the MDNR aerial survey program, a map

epicting gypsy moth defoliation since the 1980’s is available for viewing. The current

extent of EAB in Michigan is visible in the 2003 pest map. The maps can be found at:

www.mcgi.state.mi.us/forestHealth.

A project by Michigan State University in cooperation with MDNR to

determine the presence and distribution of Dogwood anthracnose

continued in 2003. This exotic pest was introduced into the United

States in the mid-1970’s and has become established in Michigan in

recent years. Dogwood anthracnose infects the leaves shortly after

they expand in the spring, eventually causing cankers that kill
Michigan 2003 Forest Health Highlights

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stems and shoots. Infected trees die in 1 to 3 years.

Because healthy trees are much better at coping with the disease

than stressed trees, management strategies focus on watering,

mulching and moderate fertilization. Fungicides can be effective if

applied beginning at bud break and reapplied every 10 to 14 days

until leaves are fully expanded.

The map shows the distribution of dogwood in Michigan and

the current distribution of dogwood anthracnose.

Increased usage of road de-icing salt last winter damaged

pines and hardwoods alike along many of the major

highways in Michigan’s Northern Lower Peninsula. The most

evident damage occurred on white pines which are highly

susceptible to salt injury. Trees within 150 feet of a

highway are easily reached by salt spray produced by fast

moving vehicles. De-icing salt damage usually occurs on

the side of the tree closest to the road. Earlier in the

winter, each passing car sent up clouds of water with a

little salt dissolved in it. This salty water settles on nearby

objects, including needles, twigs and buds. Salt can burn

and accumulate to toxic levels in plant tissues resulting in

dead needles back and in extreme cases, branch dieback starting at the branch tip.

Several hardwood defoliators were active across Michigan in

2003, including oak skeletonizer and fall webworm. Oak

skeletonizer attacks red oak trees, feeding on the upper

and lower leaf surfaces and leaving the veins exposed. The

small, pale green larvae form white cocoons, 3 mm long,

on vegetation and other surfaces. There are two

generations per year. Trees usually recover completely; no

treatments are recommended.

Fall webworm is a late season defoliator that feeds on

the leaves of dozens of species of forest and shade trees.

Newly emerged larvae immediately begin to spin a silken

web over the foliage on which they feed; as they grow,

they enlarge the web to enclose more and more foliage.

The webworm is of no great economic importance to

forest trees, but it can be a serious aesthetic pest of

shade and ornamental trees. Outbreaks usually subside

after 1 or 2 seasons. Webs can be removed safely by

pruning.

For more information contact:
Michigan 2003 Forest Health Highlights

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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: April 2004

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