Prepared by MDNR, Forest, Mineral & Fire Management 

 

2008 Forest Health Highlights Page 1 

2008 Michigan Forest Health Highlights

Inside This Issue ............ 

Resource Overview – Drought – Aspen Decline - Diplodia – Roadside Tree Stress – Beech 

Bark Disease – Emerald Ash Borer – Oak Wilt - Spruce Budworm – Larch Casebearer – 

Forest Tent Caterpillar – Gypsy Moth - Hemlock Woolly Adelgid – Jack Pine Budworm – 

Sirex Noctilio Wood Wasp – The Looper Family - Eastern Hemlock Looper - Oak Kermes 

Scale - Garlic Mustard 

Resource Overview

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 and 

water and reduce soil erosion. 
Prepared by MDNR, Forest, Mineral & Fire Management 

 

2008 Forest Health Highlights Page 2 

Drought – Although 2008 began with a wet spring and wet early summer in most areas of 

the state, areas of the south central and western UP again experienced a moderate to 

severe drought by mid-summer (See Figure 1.). All areas of the state impacted by the 

drought of the last few years continue to display drought symptoms. It can take several 

years of normal or higher amounts of precipitation for trees to recover starch reserves and 

return to normal growth patterns. Those areas affected by drought again in 2008 will have 

a longer road to recovery. These areas experienced scattered tree mortality where other 

factors such as poor soils, insects, pathogens and/or other environmental stresses 

compounded drought stress. Major stressors such as drought initiate declines in many tree 

species including aspen, black ash, sugar maple, paper birch, oak, balsam fir, hemlock, 

spruce and yellow birch. Wood borers and bark beetles thrive in drought stressed trees. 

Armillaria fungi are a common component of forest soils, invading drought weakened 

trees. Many epidemics of defoliating caterpillars such as the forest tent caterpillar, gypsy 

moth, jack pine budworm and cankerworms coincide with drought periods. In recent 

years, drought periods have caused an alarming increase in Diplodia shoot blight and 

canker of seedling and sapling red and jack pine growing on droughty sites. Drought 

related pest impacts on balsam fir on lighter, sandier soils had another bad summer in 

2008. Fir trees on poorer sites are suffering high levels of mortality as trees succumb to 

Armillaria root rot.
Prepared by MDNR, Forest, Mineral & Fire Management 

 

2008 Forest Health Highlights Page 3 

Figure 1. Broadscale indicator of drought stress.
Prepared by MDNR, Forest, Mineral & Fire Management 

 

2008 Forest Health Highlights Page 4 

Aspen decline is being reported in many areas throughout the Lake States. There are two 

problems: 1) Thin crowns with small leaves; and 2) Increased rates of top kill and tree 

mortality. These problems occur in pockets, likely corresponding to aspen clones. Site 

features such as soil type and drainage are likely contributing factors. Most commonly 

observed are pockets of aspen with sparsely foliated crowns 

containing many abnormally small leaves. There are also pockets of 

tree mortality. These sites are mostly comprised of large trees and 

are often associated with hypoxylon canker. Both problems are 

likely responses to the extreme droughts of the past decade, most 

notably in 2002-03 and 2006-07, and some areas of the UP in 2008. 

We also have had significant defoliation by the forest tent caterpillar 

and the large aspen tortrix in the last decade. Drought alone 

causes significant stress in many tree species. This stress is compounded when combined 

with other stressors such as repeated defoliation and growing on less than optimum sites. 

Hypoxylon canker is a common aspen mortality factor which can more readily invade 

weakened trees. A similar decline in aspen was observed after the extreme 1976-77 

drought. 

Other observed pests included the bronze poplar borer, leaf spot, and leaf blight. The 

conditions in early June were ripe for fungal leaf disease development. 
Prepared by MDNR, Forest, Mineral & Fire Management 

 

2008 Forest Health Highlights Page 5 

Diplodia Shoot Blight Young red and jack pine plantations 

growing on the light, sandy soils on the Baraga Plains, Baraga 

County, were heavily impacted by Diplodia shoot blight. Two to 

three year old jack pine and 10 year 

old and younger red pine plantings 

experienced areas of whole tree morality. 

Branch flagging and tree mortality of understory white pine 

has been a common site along the AuSable River in Crawford 

County for the last three years. The size of the problem area expanded each year along 

both the Manistee and AuSable River corridors, also spreading to some inland areas. 

Susan Thiel, Michigan Department of Natural Resources (MDNR) Unit Forest Manager, 

estimates that this problem has caused about 70-90% mortality in the young white pine at 

the worst locations and has significantly reduced the amount of white pine in other sites. 

She also reports seeing flagging starting to occur on some bigger canopy white pine. Dr. 

Gerry Adams, Michigan State University (MSU), has identified the causal agent as Diplodia 

scrobiculata. This pathogen has been reported on E. white pine in Connecticut, but this 

association is unknown in the Lake States. Large branch cankers, under brown lichen 

cankers, small twig cankers, Diplodia exists as a latent pathogen within a healthy host 

tree. It is a drought stress or hail damage triggered pathogen. It's likely that drought stress 

and, possibly, competition stress, have been the triggers that have allowed the fungi to 

get a foothold. D. scrobiculata has been noted as a weak pathogen of jack pine and 

red pine. The MDNR is cooperating with MSU and the USDA, Forest Service to study how 

this disease affects white pine in north central Lower Michigan. 

Roadside trees already stressed by salt and desiccating winds associated with travel 

corridors, were especially impacted by the continued drought in the south-central and 

western UP. Impacted trees included balsam fir, spruce and pine. Attacks by secondary 

pests like bark beetles and Armillaria root rot which invade stressed trees caused pockets 

of tree mortality in some areas. 
Prepared by MDNR, Forest, Mineral & Fire Management 

 

2008 Forest Health Highlights Page 6 

Grafted scion producing nuts 

Photo by Jennifer Koch 

•

Beech Bark Disease 

The MDNR, in cooperation with MSU, the University of 

Michigan and Michigan Technological University, 

continue to monitor the movement of beech scale and 

the development and impacts of Beech Bark Disease 

(BBD). The BBD advancing front (e.g. areas infested with 

scale before fungal infection) continues to spread east 

and west in the UP and to new areas in the North Lower 

Peninsula (NLP) (See map). Ludington State Park in 

Mason County was the first area in the state with BBD. 

Beech trees of all sizes are scale covered. Beech snap is 

extensive throughout the park with beech mortality reaching the 75% mark. Isolated, 

satellite populations of beech scale occur well ahead of the advancing front in both the 

Western UP and NLP. These outliers are being studied by MSU to better understand scale 

movement to new areas, and colonization rates within stands after arrival. 

The USDA Forest Service Research Facility in Delaware, Ohio continues to collect scions 

from Michigan’s resistant trees to study Beech Bark Disease 

Resistance. These trees resist scale establishment. Without the scale, 

beech are not susceptible to infection by Nectria species which 

cause beech bark disease. Scions from resistant American beech 

have been collected from infested areas of both the UP and LP. 

Beginning in the fall of 2009, Michigan will establish the first seed 

orchard with BBE resistant stock. The seed from these orchards will be 

used to restore an American beech component in BBD 

impacted hardwood forests. The long-term objective of this 

research is to develop regional repositories of resistant beech 

germplasm and establish seed orchards and seed production areas that consist of 

Confirmed beech scale sites 

Created by Daniel Wieferich, MSU 
Prepared by MDNR, Forest, Mineral & Fire Management 

 

2008 Forest Health Highlights Page 7 

genetically diverse populations of resistant beech. The MDNR continues efforts to detect 

and protect BBD resistant trees. To date, 19 families of resistant beech from the UP and 9 

families from the NLP have been confirmed resistant at the USDA Forest Service Lab in 

Delaware. Scions will again be collected from some of these trees in the winter of 2009. 

Management plans for beech containing stands anywhere in Michigan should now 

consider BBD vulnerability. Management goals are twofold: 1) To reduce BBD impacts 

ahead of the BBD killing front by decreasing the beech component such that a fully 

stocked stand remains to sustain production of both commodity and non-commodity 

forest resource values, and 2) To increase tree species diversity thereby decreasing stand 

susceptibility and vulnerability to BBD. Tree species diversity also protects a stand from 

future pests which may target a single tree species or genera. A beech component is 

maintained even in heavily BBD impacted areas. Keeping a minor beech component 

minimally affects sustained forest productivity, and offers an extended period of mast 

production. In BBD advancing front areas of the UP, it is a real challenge to stay ahead of 

beech mortality and beech snap in scale infested stands. Often times, the beech 

component of a timber sale has a significantly reduced value e.g. salvage value) due to 

volume losses from beech snap and tree mortality between the time a stand is cruised for 

sale and when it’s actually harvested. Heavily scale infested American beech are 

considered hazard trees in recreation and other high use areas. Once infected, these 

trees will break off or “snap” unexpectedly. Thus, scale infested beech are removed from 

areas where they pose a threat to human safety and/or property. 
Prepared by MDNR, Forest, Mineral & Fire Management 

 

2008 Forest Health Highlights Page 8 

*

*

2008 Upper Peninsula 

EAB Detections

The Emerald Ash Borer (EAB) was detected in two new locations in the western and southcentral portions of Michigan’s UP in 2008 (See Map). The current EAB Quarantine now 

encompasses five of the fifteen UP Counties (See Map Below). For detailed information 

on the EAB quarantine, visit the MDA website at: 

http://www.michigan.gov/mda

Michigan Technological University (MTU) in Houghton, MI continued its EAB survey efforts 

sponsored by the USDA Forest Service in cooperation 

with the MDNR. MTU. Areas of high EAB risk were 

identified using maps of the state’s ash resources and 

state park databases showing visits from residents of 

EAB infested 

counties. Trap 

trees were 

deployed in state 

and federal parks 

and 

campgrounds 

throughout 

Michigan and Wisconsin. The survey effort also 

included visual inspections of firewood and ash trees in these and adjacent areas (Storer, 

MTU). 

Researchers at MSU are assessing the influence of clusters of girdled trees on the spread of 

EAB in forested areas of the NLP. Four strategies utilizing girdled trap trees as sinks for EAB 

are: 1) girdle and remove trees annually; 2) apply systemic insecticide, girdle and remove 

some trees each year; 3) harvest (possibly only large ash or thin to 10-120 ft2/ac basal 

area) and create islands of attraction (clusters of girdled trees); and 4) harvest and create 

islands of attraction with lethal trap trees (trees treated with a systemic insecticide and 

girdled). The EAB spread and population densities in treated and untreated areas are 
Prepared by MDNR, Forest, Mineral & Fire Management 

 

2008 Forest Health Highlights Page 9 

Slow Ash Mortality 

Project Area 

SLAM Project Area

compared annually. Preliminary results suggested that clusters of girdled trees were more 

attractive to EAB than nearby clusters of non-girdled trees. Also found that at low EAB 

densities, girdled trees were much more attractive to pioneering adult beetles compared 

to non-girdled trees within the same cluster of girdled trees. At low EAB densities, there 

was little “spill-over” effect leading to EAB infestation of ash trees near or adjacent to 

girdled trees (Siegert & McCullough, MSU). 

The Michigan Department of Agriculture’s (MDA) EAB surveys where more extensive, 

covering the entire UP and the northern tip of the NLP. The MDA deployed both girdled 

detection trees and artificial traps (e.g. purple traps) containing an aromatic lure (See 

Map below). 

A pilot project was initiated in 2008 to test the latest research concepts for managing EAB 

outlier populations. The area selected for this study contains the UP St. Ignace and Moran 

outlier infestations. The project is called ‘SL.A.M’ to stand for Slow Ash Mortality. The goal 
Prepared by MDNR, Forest, Mineral & Fire Management 

 

2008 Forest Health Highlights Page 10 

is to employ and carefully monitor and measure the impact of multiple strategies to slow 

the rate at which EAB disperses and impacts ash trees. The primary facets of the project 

include: 

This work plan was developed with the following objectives: 

• Reduce EAB population growth in the core areas. 

• Limit the expansion (size) of the core areas. 

• Prevent satellite populations from expanding and becoming core populations. 

• Protect high value trees where possible. 

• Outside of the core areas, focus on phloem reduction which should limit future 

EAB population buildup due to reduced food availability. 

• Locate and disrupt any corridors of ash that may exist within the project area, 

especially any corridors that would extend outside the project area. The most 

likely locations that would support ash along a corridor would include riparian 

corridors (streams, lake sides), road, railroad and trail corridors. 

• Develop and maintain regular communications and consistent messages with 

the local landowners in and around the project area. 

• Assist local woodland owners and homeowners in making environmentally and 

fiscally responsible decisions in regards to their ash trees and woodlands. 

The MDA conducted intense surveys in the SLAM area to determine the density and 

distribution of EAB. They deployed 433 girdled detection trees and 225 panel traps. They 

also worked with the MDNR to survey the ash resources in the Moran Area. Survey data 

will help locate proposed management activities on the site in 2009 and, over time, will be 

used to evaluate the impact of management activities. 

The MDNR conducts annual Firewood sweeps in December after closure of the firearm 

deer hunting season. All hardwood firewood left at State Forest Campgrounds and State 
Prepared by MDNR, Forest, Mineral & Fire Management 

 

2008 Forest Health Highlights Page 11 

Parks is burned. This eliminates the risk of EAB emerging from infested firewood the 

following spring. During the camping season, Parks and Recreation employees inspect all 

campers entering state parks. State forest staff conducts random inspections of state 

forest campgrounds. When found, firewood which is not in compliance with the EAB 

quarantine and the MDNR Director’s Order is seized and burned. The Director’s Order 

prohibits moving ash wood onto state lands, unless that ash is without bark attached. 

Guidelines to manage ash are influenced by the distance from EAB populations and the 

abundance and size of ash trees. The general goal is to decrease forest vulnerability by 

reducing the number of ash trees where abundant, and increasing tree species diversity 

either by promoting the regeneration and establishment of existing tree species, or by 

planting suitable, new tree species. An objective is to create a stand that will recover 

rapidly in the event that all ash is lost to the EAB. Increasing tree species diversity where 

needed protects a stand from future pests which target a single tree species or genera. If 

possible, no more than 10% of any stand should remain in ash species. If confidence is 

high that a stand is greater than 10 miles EAB infested trees, a greater ash component 

can be retained. This is especially important if ash are needed to maintain a fully stocked 

stand for optimum utilization of a site. Vigorous pole size and smaller ash are targeted for 

retention. Removing one large ash has a much greater effect on reducing EAB 

population potential than does removing many saplings or a few pole size trees. 

A new pesticide, Tree-ägeTM (active ingredient: emamectin benzoate) is now registered 

for use in Michigan. Its primary use will be protecting valuable landscape ash trees from 

EAB. Tree-age can be purchased and applied only by trained, certified arborists and 

landscapers. The product is applied as a trunk injection at the base of an ash tree. Like 

any systemic insecticide, this product must be transported through the trunk and into the 

canopy. Therefore, it will usually be more effective in a tree that is reasonably healthy 

than in a tree that has already been severely injured by EAB larvae. 
Prepared by MDNR, Forest, Mineral & Fire Management 

 

2008 Forest Health Highlights Page 12 

Upper Peninsula Counties with Oak Wilt 

Oak Wilt continues to spread naturally and artificially through much of the Lower 

Peninsula. Overland spread of oak wilt through firewood movement and the wounding of 

oak by activities such as branch pruning continue to plague efforts to slow the spread of 

this fatal disease. To slow the overland spread of oak wilt, harvesting restrictions are 

observed on state land. Forests where red oak trees remain after harvest cannot be cut 

between April 15 and July 15. Michigan currently has three oak wilt initiatives: 

1. Beginning in 2004, USDA Forest Service Oak Wilt Suppression funds have supported a 

joint MSU Extension and MDNR effort to rid the UP of this threat to its oak resources. 

Oak wilt has been detected in two counties, 

Menominee and Dickinson. The objectives of this 

program are to: 1) Remove oak wilt from the UP by 

detecting and treating all infection centers; 2) 

Educate affected communities to prevent the 

reintroduction of oak wilt; and 3) Demonstrate an 

approach for detecting and effectively treating oak 

wilt infection centers throughout Michigan. To date, 

20 miles of root-graft barriers have been established, 

and approximately 150 oak wilt epicenters removed. 

Unfortunately, the 2008 federal funding for this 

project was withdrawn to help cover the costs of 

western fires. This funding has now been restored 

and is available for 2009 suppression activities. 

2. In cooperation with USDA Forest Service, State & 

Private Unit pathologists, the MDNR Forest Health 

Program continues to evaluate the effectiveness of 

stump extraction for stopping the underground 
Prepared by MDNR, Forest, Mineral & Fire Management 

 

2008 Forest Health Highlights Page 13 

spread of oak wilt. The method is being tested at two infection centers in the NLP. 

Root graft barriers were created in 2007 and 2008 by severing symptomatic trees 

and extracting stumps using backhoes and excavating equipment. Extracted 

stumps were inverted, placed back into the hole and covered with dirt to prevent 

sap beetles from feeding on any pressure pads that might form. Only symptomatic 

trees were treated. Wood from infected trees was burned to prevent development 

of spore-producing pressure pads. Additional treatments scheduled this fall will 

include applications of herbicides to cut stumps of perimeter trees. It appears that 

this method can be a cost-effective alternative to traditional root graft barrier 

methods when used to treat new 

infection centers, i.e. areas where 

symptoms appeared within one year 

of treatment. Treatment of older 

infection centers is not recommended 

since the fungus has likely already 

traveled through the roots beyond the 

immediate vicinity of the extracted stumps. Cost analyses indicate that this method 

is significantly cheaper than traditional root graft barrier installation using a vibratory 

plow. Also, the method can be used in soils too rocky for vibratory blades to 

penetrate. 

3. Michigan, Minnesota, Wisconsin and Texas are working with the USDA Forest Service, 

Forest Health Technology Enterprise Team, Fort Collins, CO, to create a national oak 

wilt database. The database is being designed to meet both state and national 

forest health program needs for reporting and mapping oak wilt occurrence, 

measuring resource impacts, evaluating resource risk, and tracking management 

efforts. 
Prepared by MDNR, Forest, Mineral & Fire Management 

 

2008 Forest Health Highlights Page 14 

Spruce Budworm is in several counties in Michigan’s UP. Isolated areas of mature to over 

mature spruce/fir in the south central and north central UP have top kill and tree mortality 

caused by repeated defoliations. The spruce budworm is one of the most destructive 

native insects in the northern spruce and fir forests of the Eastern United States and 

Canada. Periodic outbreaks of the spruce budworm are a part of the natural cycle of 

events associated with the maturing of balsam fir. Balsam fir is the species most severely 

damaged by the bud-worm in the Lake States. White and black spruces are also hosts 

with some feeding on tamarack, pine, and hemlock. Spruce mixed with balsam fir is more 

likely to suffer budworm damage than spruce in pure stands. 

Areas of Eastern Larch (tamarack) predisposed by Larch Casebearer defoliation and 

drought continue to be impacted by the Eastern Larch Beetle. Larch beetle populations 

which build in stressed trees can successfully attack neighboring healthy larch. Signs of 

larch beetle activity include: 1) yellowing of foliage in the lower portion of the tree in late 

July and early August; 2) Small round (2 mm in diameter) adult beetle entrance holes in 

the bark; 3) brownish boring dust below the entrance holes; 4) bark beetle galleries 

etched in the sapwood beneath the bark; 5) woodpeckers feeding on the main stem; 

and 6) loose bark on seemingly health trees in late summer. It takes a few years of 

recovery before larch beetle populations subside. If the current drought affecting the 

south central and western UP extends into the 2009 growing season, we can expect 

continued eastern larch beetle activity in affected areas. There was little casebearer 

activity reported in 2008. 
Prepared by MDNR, Forest, Mineral & Fire Management 

 

2008 Forest Health Highlights Page 15 

Forest tent caterpillar (FTC) populations were heavy over 

a large area of the northwestern Lower Peninsula for the 

first time is several years. Over 43,904 acres were 

moderately to heavily defoliated, with sugar maple and 

basswood most commonly affected. As with most earlyseason hardwood defoliators, 3 or more years of 

consecutive heavy defoliation can cause dieback and 

mortality, particularly if trees have been previously 

stressed by drought or other factors. Fortunately, FTC is a 

pest native to Michigan, and an effective natural enemy 

complex made up of insect parasites, predators and fungal pathogens usually bring high 

populations under control within 2 years. 

Left - Aerial view of FTC defoliation in Northern 

Lower Peninsula. 
Prepared by MDNR, Forest, Mineral & Fire Management 

 

2008 Forest Health Highlights Page 16 

Gypsy moth populations were down again slightly in Michigan in 2008 with 18,689 acres 

defoliated, compared with 19,146 acres in 2007 and 31,995 acres in 2006. Rainfall levels 

were normal or above normal in many parts of the state in the spring, and temperatures 

were cool in May and early June. This weather was favorable to development of the 

fungal pathogen Entomophoga maimaiga and likely contributed to the statewide 

decline in gypsy moth numbers. 

The MDA no longer sponsors the Cooperative Gypsy Moth Suppression Program, which 

provided communities cost-share assistance for aerial pesticide applications. A handful 

of communities conducted locally-funded programs around Michigan in 2008. 

Gypsy Moth Larva 
Prepared by MDNR, Forest, Mineral & Fire Management 

 

2008 Forest Health Highlights Page 17 

The MDNR continues to cooperate with the MDA and MSU in efforts to prevent the 

Hemlock Woolly Adelgid (HWA) from becoming established in the NLP and the UP. The 

HWA is an exotic invasive insect that feeds on tree sap, killing needles, twigs and 

branches. Infested trees eventually die. The HWA was detected on eastern hemlock 

landscape trees in the Harbor Springs Area in 2006. In 20 years of HWA survey activities, 

this is the third time the pest has been detected in 

Michigan. The previous two findings in 2001 were 

restricted to nursery stock that was quickly destroyed. 

The 2006 detection marks the first time that HWA has 

been found on out-planted and native trees. All 

imported hemlock and adjoining native trees were 

removed and destroyed. The MDA also treated a perimeter of hemlock with a systemic 

insecticide to eradicate difficult to detect HWA. Treatments were repeated in the spring 

of 2007. The MDA continues to look at other hemlock in the area to determine whether 

additional infested nursery stock have been planted in Michigan. 

The MDA established a HWA Quarantine in December 2000. 

The quarantine prohibits the movement of hemlock seedlings 

and nursery stock, logs, lumber with bark, uncomposted 

chips with bark and uncomposted bark from infested 

counties of eastern states and 

from California, Oregon, 

Washington and British 

Columbia. The MDNR Forest Health, Inventory and 

Monitoring Program continued HWA and Beech Scale Rapid 

Early Detection Surveys for the fifth straight year. Areas 

throughout the state with abundant hemlock, particularly 

those within or adjacent to high hazard zones (see map), 

were surveyed for HWA. These zones, developed by MSU, 
Prepared by MDNR, Forest, Mineral & Fire Management 

 

2008 Forest Health Highlights Page 18 

identify areas where higher minimum winter temperatures reduce overwintering mortality 

of HWA. 

The HWA monitor trees were established in several hemlock stands near the initial HWA

detection area. The assumption is that bird feeders hung at these plots increase the 

likelihood of detecting bird-vectored HWA crawlers on these trees. 

American beech growing near HWA survey areas that were outside of known beech 

scale areas were examined for beech scale. No HWA or new beech scale areas were 

found in 2008. 
Prepared by MDNR, Forest, Mineral & Fire Management 

 

2008 Forest Health Highlights Page 19 

The Jack Pine Budworm defoliated 14,569 acres statewide in 2008, down significantly from 

158,500 acres in 2007 and 150645 acres in 2006. This follows a historical trend for budworm 

in Michigan, where populations typically decline significantly after 2 years of moderate to 

heavy defoliation. Egg and larval parasites and overwintering mortality typically account 

for this drop in insect numbers. 

The budworm is the most important pest of jack pine in North America. Stands older than 

50 years are most susceptible to damage. Jack pine over 50 years old that has suffered 2 

or more defoliations during the past 3 years is at highest risk of top kill or mortality. The 

MDNR management objective is to reduce jack pine rotations on state land to 50 to 60 

years, significantly reducing the risk of budwormtriggered mortality. 

Locally, heavy budworm defoliation occurred for 

the second year in the Yellow Dog Plains in 

Marquette County. In the Baraga Plains, 

defoliation occurred for the first time in this 

outbreak cycle. In addition to older, high-risk 

stands, defoliation is occurring in young saplingand pole-sized jack pine stands. 

Ground and aerial views of JPBW 

Damage. 
Prepared by MDNR, Forest, Mineral & Fire Management 

 

2008 Forest Health Highlights Page 20 

Since its detection in New York State in 2004, the European wood wasp, Sirex noctilio, has 

been confirmed at trap sites throughout the eastern Great Lakes region of Ontario, 

Canada. This exotic wood wasp (commonly referred to as horntail wasp) is native to 

Europe, Asia and northern Africa and was collected in Fulton, New York in September 

2004. The New York find is the first time the insect has been documented in North 

American forests. The EWW is rarely a pest in its native areas where it confines its attacks 

to dead or dying trees. In areas where it has been introduced, however, it is a major pest 

of pine plantations, where it attacks living trees and can cause up to 80% mortality. 

Outbreaks often build up in stressed trees and then spread to more vigorous trees. 

Widespread outbreaks have occurred in Australia, New Zealand, South Africa and South 

America. 

Female Sirex are attracted to stressed trees where they insert their sword-like ovipositors 

into the outer sapwood, deposit their eggs and introduce a toxic mucus and fungus 

(Amylostereum areolatum). Larvae feed only on the fungus, which, together with the 

mucus, kills infested trees. 

Symptoms of Sirex infestation include: 

• Exit holes approximately 1/8 to 3/8 inches in diameter; 

• Tree crowns turning light green then yellow to reddish brown in the late spring or 

early summer; 

• Larval galleries (tunnels) in the wood, packed with a fine powdery frass (insectproduced sawdust); 

• Beads of resin or streams of resin on the bark, exuding from holes created during 

egg-laying. 

Pitch or resin will often weep from the tiny puncture wounds made by the adult females 

when they lay their eggs. The damage can be very subtle or quite obvious and care must 
Prepared by MDNR, Forest, Mineral & Fire Management 

 

2008 Forest Health Highlights Page 21 

be taken in using this symptom as a feature of fresh attacks. In Michigan, most 2- and 3-

needle pines are considered susceptible, including Scotch, jack, red and Austrian pines. 

The Eastern Regional office of the USDA Animal Plant Health Inspection Service’s Plant 

Protection & Quarantine (PPQ) conducted a Sirex survey in 17 uninfested counties in 

southeastern Michigan to continue delimiting the spread of Sirex. 

Traps were placed in Scotch, red, jack and Austrian pine and baited with 70% alphapinene/30% Beta-pinene blend. 

New detections of Sirex were made in Huron and St. Clair counties. A single female was 

caught in St. Clair County and 4 females were caught in Huron County at two different 

sites (see map). All catches were made in mature Scotch pine and were either single 

trees or Scotch pine mixed with hardwoods. No detections were made in dense 

overstocked stands of host material. Positive 

catches were made between early August 

and mid September. 

Trapping data from across the region 

indicates that Sirex populations are 

spreading naturally along the shoreline of 

Lake Huron to the north after spreading into 

Michigan from Ontario, Canada. 

MTU continues to work on a USDA Forest 

Service-funded Sirex detection survey. Sites 

were established in 2007 using groups of 3 to 

5 herbicided pine trees. The herbicides 

cause stress that increases the trees’ 

attractiveness to the wood wasp. Traps are 
Prepared by MDNR, Forest, Mineral & Fire Management 

 

2008 Forest Health Highlights Page 22 

hung from these trees and a subset is cut in the spring to look for larvae of the wood 

wasp. In addition, funnel traps baited with alpha and beta pinene are placed in the 

trees. 

For more information about Sirex, link to: 

http://na.fs.fed.us/spfo/pubs/pest_al/sirex_woodwasp/sirex_woodwasp.htm

http://www.aphis.usda.gov/plant_health/plant_pest_info/sirex/index.shtml

http://www.treesearch.fs.fed.us/pubs/12997. 

To determine whether an insect that you have collected is Sirex noctilio, contact the MSU 

Plant Pest Diagnostic Clinic at 517-355-4536, or your local county MSU Extension office. 

Isolated areas of hardwoods including mostly sugar maple and American beech were 

defoliated by caterpillars known as loopers or cankerworms in 2008. Hardwood 

defoliators included the Spring Cankerworm, Bruce Spanworm, Linden Looper, and Fall 

Cankerworm. Many caterpillar outbreaks coincide with drought periods. Drought 

stressed trees are less able to produce chemicals used to defend against defoliators. 

Periods of warm, dry weather also reduce mortality from insect pathogens which are 

favored by cool, wet weather; and, decrease larval predation and parasitism due to the 

quicker transition from egg to larvae to pupae. Areas in the western UP reported heavy 

moth flights of fall cankerworm in October. These areas can expect some level of 

hardwood defoliation early in the growing 2009 growing season. 

Eastern Hemlock Looper larvae can be extremely destructive to 

hemlock, balsam fir, and white spruce. Hemlocks may die after one 

year of severe defoliation, fir in one or 

two years. Loopers have been 

epidemic in isolated areas of the state 

in the last few years. Populations moved areas of the 

central UP to the western UP in 2008. Unfortunately, 
Prepared by MDNR, Forest, Mineral & Fire Management 

 

2008 Forest Health Highlights Page 23 

because loopers first feed on lower branches, it is impossible to detect feeding damage 

with aerial surveys until trees are heavily damaged. Areas first defoliated in 2008 should 

be monitored in 2009. Two years defoliation can result in top kill and tree mortality. 

Hemlock should not be harvested in stands where defoliation is expected because: 1) 

Insects are concentrated on residual hemlock after cutting; 2) New openings can reduce 

moisture availability by increasing amount of sunlight reaching the forest floor. 

Oak Kermes Scale was reported on red oaks in the Northern Lower Peninsula in 2008. Both 

Kermes and Lecanium scales are common on oak and 

both are native to North America. Mature scales are 

tan, globular and hard. They are easily mistaken for 

galls or buds. Oak is the only host. Kermes scales are 

sucking insects which feed on oak sap. Feeding can 

result in branch dieback, reduced tree growth rates, 

and the production of sooty mold which grows on the 

honeydew secreted by the scales. Tree mortality may occur during heavy infestations, 

especially in an oak resource stressed by other factors such as severe drought and 

repeated defoliation. 

This was the 5th year of an effort to eradicate Garlic Mustard from an eighty acre northern 

hardwoods site in the Eastern UP. This is a seven year prescribed burn project which 

includes follow-up use of glyphosate herbicide to treat plants missed by the spring burns. 

Treatments are designed to stop the spread of the plant 

and eventually eliminate garlic mustard. Garlic mustard 

populations have been greatly reduced. The burn just 

did not carry well in 2008 with only about 30-40% burn 

coverage. Only a few small clumps of second year 

stalks remain on this 80 acre parcel with none closer 

than a chain from the perimeter. The entire area was surveyed for residual plants which 

Kermes Scale on Oak 

Whitney Cranshaw, Colorado State Univ. 
Prepared by MDNR, Forest, Mineral & Fire Management 

 

2008 Forest Health Highlights Page 24 

were subsequently sprayed with Glyphosate. Additional treatments and monitoring of 

plant community responses to burning and herbicide treatments are planned for 2009. 

The MDOT is aggressively treating garlic mustard at the Cut River Bridge Scenic Area in 

Mackinac County on highway US-2. This was the 3rd consecutive year that MDOT applied 

Garlon 3A in spring and fall at the bridge site.