Minnesota First Detector Manual
Table of Contents Introduction to the Manual .........................................................................................................5 All About Emerald Ash Borer ....................................................................................................6 Is My Tree an Ash? .....................................................................................................................8 Trees Commonly Mistaken for Ash ..........................................................................................10 How Do I Recognize Emerald Ash Borer? ...............................................................................12 Symptoms and Damage .......................................................................................................12 Recognizing Emerald Ash Borer Adults ..............................................................................14 Recognizing Insect Galleries in Ash Trees .................................................................................15 Emerald Ash Borer ....................................................................................................................15 Eastern Ash Bark Beetle ...........................................................................................................16 Metallic Wood-boring Beetles (Flat-headed Borers) ................................................................17 Long-horned Beetles (Round-headed Borers) ...........................................................................18 Clearwing Moth ........................................................................................................................19 Ash Cambium Miner .................................................................................................................20 What’s in That Woodpile? ...........................................................................................................21 Do I Have Gypsy Moth? .............................................................................................................26 Do I Have Asian Long-horned Beetle? .......................................................................................28 Do I Have Sirex Woodwasp? .......................................................................................................29 Does My Tree Have Thousand Cankers Disease of Walnut? ......................................................30 What Can I Do if I Suspect I Have Found a Forest Pest? ...........................................................32 Tree Genera of Minnesota and Invasive Pests of Concern That May Be In or On Wood ..........33
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Notes
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Introduction to the Forest Pest First Detector Manual In 2008, the University of Minnesota Extension, the Minnesota Department of Agriculture Plant Protection Division, and the Minnesota Department of Natural Resources Division of Forestry combined efforts and rolled out the Emerald Ash Borer First Detector Program. The program is part of the National Plant Diagnostic Network (www.npdn.org) whose mission is to maintain profitability of production in crops, food, fiber and forests, to maintain the security of food production, and to prevent bioterrorism. Here in Minnesota, we chose to focus on and provide in-depth training for a specific pest - emerald ash borer - to increase our chances of finding the targeted pest. Since 2008, the training has expanded to include several other pests of national concern.
The First Detector system addresses only the first detection of the targeted pest in the state and in a county. All new pest detections require the same quick action: to detect and diagnose it so that state and federal agencies can contain and eradicate the pest if possible and specialists can develop control measures. Once discovered, the goal is to slow the spread of the targeted pests within the county and in Minnesota, and to help provide the public with current information about the pest. The pests contained in this booklet are a few of those we are currently facing. To report one of these pests or to find a Forest Pest First Detector near you, please contact Arrest.The.Pest@state.mn.us or 888-545-6684.
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All About Emerald Ash Borer Jeff Hahn, University of Minnesota Assistant Extension Entomologist
Biology
The emerald ash borer (EAB) is a very destructive wood-boring insect pest of ash trees. Ash is the only known host of this borer in the United States. The exotic beetle is native to Asia, including China, Japan, Mongolia, Korea, the Russian Far East, and Taiwan. It was first discovered in North America in southeast Michigan in June, 2002, although it was likely introduced at least 10 years earlier.
EAB generally has a one-year life cycle, sometimes extending to two years. They overwinter as fully-grown larvae (called pre-pupae) in chambers constructed under the bark of ash trees, and pupate in early spring. Depending on where you live in Minnesota, adults emerge any time from late May to August, leaving characteristic D-shaped emergence holes in the bark and wood. After feeding on leaves, adults mate and females lay eggs in bark cracks. Eggs hatch in 7 to 10 days. The creamy white larvae are called flat-headed borers. They can be distinguished from other flat-headed borers by the two dark spines at the end of the abdomen. Larvae tunnel under the bark, creating winding, S-shaped galleries in the bark and outer sapwood as they feed. These tunnels girdle the trunk and branches, interrupting the flow of water and nutrients.
Why is EAB important? This destructive beetle has killed tens of millions of ash trees where it has been established. There are nearly one billion ash trees in Minnesota, the largest concentration of ash in the country. Not only are these trees abundant in our forests, but they are also an important component of our urban landscapes. Research to date has not found any resistance to EAB in our native ash. We are likely to lose much, if not all, of this resource.
Should I Be Planting or Removing Ash? Because of the overabundance of ash in urban landscapes and other sites, it is strongly recommended not to plant additional ash. Consider other woody plant options that are available to Minnesotans (see University of Minnesota Extension information at www.extension. umn.edu/gardeninfo/components/info_trees. html#selection). However, if you have a healthy ash tree in your yard and EAB has not been discovered within 15 miles of a known infestation, there is no reason to remove it. As long as the ash is a low maintenance plant, keep it in your landscape.
Should I Be Treating My Ash?
Mark Abrahamson, MN Dept. of Ag
University experts throughout the EAB-infested states do not advise insecticide treatments without a confirmed infestation within 15 miles. This advice is based on the probability of a tree becoming infested with EAB, bearing in mind that EAB infestations in other states have usually gone undetected five years or more (the EAB infestation first discovered in Minnesota in May, 2009 was found to be approximately three years old). Some of the chemicals used to protect trees from EAB can be highly effective, but such treatments in the absence of a confirmed infestation are very likely to add years of unnecessary applications and expense. For current information on insecticide options, consult your county or regional University of Minnesota Extension office, or visit www.emeraldashborer.info or www. extension.umn.edu/issues/eab.
EAB larva
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Jeff Hahn, UMN
All About Emerald Ash Borer
Adult EAB (actual size 1/3–1/2 inch)
What Can I Do To Help? First, don’t transport firewood when you go camping or are buying it for home use. Purchase the wood you need at local sites or at the campgrounds you are visiting. On its own, EAB will generally move only about 1/2 mile a year from infested sites, but with help from people, it can travel hundreds of miles when carried in firewood and other wood products or nursery stock. Next, be aware of what EAB looks like as well as the symptoms of an EAB-infested tree. Report any suspect insects or declining ash trees (see “What Can I Do If I Suspect I Have Found a Forest Pest?” page 32). There have been many cases where a homeownerwas the first to find the infestation in an area. 7
Is My Tree an Ash? Emerald ash borer (EAB) attacks all species of ash native to North America, so the ability to identify ash trees is essential in monitoring for EAB infestations. Black ash, green ash, and white ash are native to Minnesota’s woods and commonly found in our urban environment.
Remember to keep in mind there are other problems that can cause an ash tree to decline and show symptoms of stress (see page 32 for additional resources).
Ash branching, bud arrangement, and seeds On ash trees, buds and branches grow directly opposite each other. This is most clear with individual leaves, as twigs and small branches often die and drop off over time, so large branches may not always have branches opposite them. Seeds are clustered, one to two inches long, and paddle-shaped. Seeds can remain on the tree until late fall or early winter.
Welby Smith, MN DNR
EAB lays eggs on all sizes of ash, from small one-inch diameter to large, mature trees. They commonly attack stressed and unhealthy trees first, similar to bronze birch borer and two-lined chestnut borer, native pests of birch and oak. However, EAB can also attack and kill vigorously-growing trees.
Dave Hanson, U MN
Ash seeds
Ash leaf
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Is My Tree an Ash?
Black ash
Welby Smith, MN DNR
Jana Albers, MN DNR
Black ash bark
Black ash
Welby Smith, MN DNR
Black ash grows to 108 feet tall, with leaves that have 9-11 finely-toothed leaflets. Individual leaflets are not stalked. Leaves range from 9”-16” in length (from twig to terminal leaflet tip). Black ash bark is light gray and smooth on young trees. As the tree matures the bark becomes scaly, not deeply furrowed as with green or white ash. It is one of the last trees to leaf out in spring and is most commonly found growing on wet sites. Leaves turn yellow in the fall.
Black ash leaflets are not stalked.
Green ash
Green ash bark
Welby Smith, MN DNR
Dave Hanson ,U MN
Joe O’Brien, US Forest Service, bugwood.org
Green ash is a common boulevard tree and can grow up to 112 feet tall. Leaves have 5-9 finely-toothed leaflets attached by short, winged stalks. Leaves can range from 6”-12” in length (from twig to terminal leaflet tip). Green ash bark is brown to dark gray and can be smooth to slightly flaky, maturing to deeply furrowed, interlacing ridges with a diamond or honeycomb appearance. Leaves turn yellow in the fall.
Green ash bark
Green ash leaflets have short winged stalks.
White ash
White ash bark
White ash bark
White ash leaflets have long stalks.
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Welby Smith, MNDNR
PA Dept. of Con. and Nat. Res., bugwood.org
Dave Hanson, UMN
Keith Kanoti, Maine Forest Service, bugwood.org
White ash is a large tree up to 105 feet tall, with leaves that have 5-9 (usually 7) toothed leaflets. Leaflets are attached by a relatively long stalk that is not noticeably winged. Leaves can range from 8”-12” in length (from twig to terminal leaflet tip). The bark on young trees is green-gray, maturing to dark gray with deep, narrow furrows and interlacing ridges with a diamond-shaped appearance. White ash looks very similar to green ash, but in the fall, leaves are usually maroon instead of yellow.
White ash
Trees Commonly Mistaken for Ash Boxelder
Boxelder seeds
Welby Smith, MN DNR
Welby Smith, MN DNR
Boxelder is a Minnesota native in the maple family and has opposite branching. The compound leaves have 3-5 leaflets. Seeds are the classic paired “helicopters.�
Boxelder compound leaves
Mountain-ash
Mountain-ash flower
Keith Kanoti, Maine Forest Service, bugwood.org
Welby Smith, MN DNR
Bill Cook, MSU, bugwood.org
This is not a true ash and therefore is not attacked by emerald ash borer. It has alternate branching and compound leaves. European Mountain-ash has showy white flowers in spring and bright orange-red berries.
Mountain-ash berries
Mountain-ash leaf
Hickory
Welby Smith, MN DNR
Welby Smith, MN DNR
Bitternut and shagbark hickory are both native to Minnesota. They have large, compound leaves and alternate branching. Hickory fruit is a brown nut within a green husk.
Hickory fruit
Hickory coumpound leaves
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Trees Commonly Mistaken for Ash
Black walnut
Black walnut fruit
Welby Smith, MN DNR
Welby Smith, MN DNR
Black walnut is a large tree native to Minnesota and has alternate branching. Leaves are compound with 12-18 leaflets. Fruit is a large, round, brown nut in a green husk. The husk is not sticky.
Black walnut compound leaves
Butternut
Butternut fruit
Bill Cook, MSU, bugwood.org
Paul Wray, Iowa Sate University, bugwood.org
Butternut is a medium to large tree, very similar to black walnut. Alternate branches have 11-17 compound leaflets. Fruit is a nut enclosed in a sticky husk that is bluntly pointed.
Butternut compound leaves
Elm
Elm seeds
Welby Smith, MN DNR
Paul Wray, Iowa Sate University, bugwood.org
There are several species of native elms in Minnesota. They all have simple, toothed leaves that are alternately arranged on the branch. Seeds are small, papery, and round with the seed in the center.
Elm alternately arranged leaves
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How Do I Recognize Emerald Ash Borer? Symptoms and Damage When trees are first attacked by EAB, symptoms of its presence are inconspicuous and difficult to notice. Because the same symptoms can be indicators of stress as a result of many other factors such as drought stress, soil compaction, diseases, or mechanical injury, they may be ignored by the homeowner at first.
Mark Abrahamson, MN Dept. of Ag
Adult beetles feed on ash foliage, but the damage seen along leaf margins is minimal. Ash trees can tolerate small numbers of EAB larvae, but are girdled and killed as more and more larvae feed on the phloem and outer sapwood beneath the bark. When populations increase, the winding tunnels made by the larvae cut off the supply of nutrients and water in the tree. Thinning foliage and dieback in the upper part (crown) of the tree become apparent after multiple years of infestation, eventually resulting in severe dieback and little foliage. Infested trees are usually killed in three to four years.
Thinning foliage in crown
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How Do I Recognize Emerald Ash Borer?
Woodpecker damage
Vertical bark splits
Mark Abrahamson, MN Dept. of Ag.
Steve Katovich, USFS, bugwood.org
PA Dept. of Cons. of Nat. Res., bugwood.org
Woodpeckers feed on insects beneath bark, so woodpecker attacks on ash may also indicate the presence of EAB. In general, EAB attacks higher in the tree at first, so woodpecker activity may also go unnoticed until the infestation is heavier. Rough holes and strips of bark flecked away by woodpeckers as they excavate the tree looking for larvae may actually be the earliest symptom of infestation. If you were to remove the bark behind a woodpecker hole on the trunk of a tree showing symptoms, you should also find a larval gallery.
Revealed larval gallery from woodpecker hole
Mark Abrahamson, MN Dept. of Ag.
Edward Czerwinski, Ontario Minnistry of Natural Resources, Canada, bugwood.org
When the adults emerge, they create 1/8-inch, D-shaped exit holes that are characteristic of this insect but can be hard to see. Vigorous shoots, called epicormic sprouts, may occur in clumps on the lower trunk and major branches as the tree responds to EAB activity.
D-shaped exit holes
Epicormic sprouts
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How Do I Recognize Emerald Ash Borer?
Recognizing Emerald Ash Borer Adults
different shape, with the abdomen wider than the head. The polydrusus weevil is a small, 1/4-inch long, oval insect with a short snout. Its body is covered with pale metallic-green scales.
Dave Cappaert, MI State University, bugwood.org
Emerald ash borer (EAB) is a slender, elongate insect, usually 1/3–1/2 inch long. It is widest just behind the head, gradually tapering to the end of the abdomen. It is bright metallic green, often with a copper-colored area behind the head. Beneath the wings the body is bright magenta.
Also, not every insect you find beneath the bark is EAB. There are many native ash borers present in Minnesota, such as the redheaded ash borer, ash bark beetle, and ash clearwing borer (see pages 15–20).
This borer belongs to a group of insects called metallic wood-boring beetles and is closely related to the bronze birch borer and the two-lined chestnut borer, both native to Minnesota. However, EAB is slightly larger and more brightly colored than these species.
Jeff Hahn, UMN / Val Cervenka, MNDNR
Not every green insect you see is EAB. There are several common insects that are confused with EAB, especially the six-spotted tiger beetle and the polydrusus weevil. The six-spotted tiger beetle is similar in size to EAB, generally 3/8–1/2 inch long, but has a conspicuous, large head and eyes. It is also a
Insects in Minnesota that may be confused with emerald ash borer.
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Recognizing Insect Galleries in Ash Trees The images in this section include galleries made by different types of insect larvae found in ash trees in Minnesota so that you may compare their appearance with those made by EAB.
Emerald ash borer
Mark Abrahamson, MN Dept. of Ag
EAB larvae make S-shaped galleries, particularly during the early stages of infestation. As borers grow larger and space becomes limited, galleries may be less compact.
Mark Abrahamson, MN Dept. of Ag
Mark Abrahamson, MN Dept. of Ag
Early EAB gallery
EAB gallery
Photo source unknown
Mark Abrahamson, MN Dept. of Ag
D-shaped emergence hole in debarked wood
Old infestation
EAB in black ash: galleries not as compact
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Recognizing Insect Galleries in Ash Trees
➜
The Minnesota Department of Agriculture found eastern ash bark beetles in 83 percent of ash trees sampled during 2007 EAB detection tree surveys.
➜
Unlike other borers found in ash trees, adult ash bark beetles feed under the bark just as the larvae do. Bark beetle egg galleries cross the wood grain and larval galleries run parallel to the grain.
Gyorgy Coska, Hungary Forest Research Institute, bugwood.org
Eastern ash bark beetle
Mark Abrahamson, MN Dept. of Ag.
David Cappaert, Michigan State University, bugwood.org
Larval galleries are at right angles to egg-laying galleries and often closely spaced. Egg-laying galleries cross the wood grain
Eastern ash bark beetle
Exit holes
Mark Abrahamson, MN Dept. of Ag.
➜ Multiple adult feeding galleries begin to show as bark is peeled away
Adult eastern ash bark beetle on knife tip
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Mark Abrahamson, MN Dept. of Ag.
➜➜
➜
Recognizing Insect Galleries in Ash Trees
Metallic Wood-boring Beetles (Flat-headed Borers)
Larvae are greatly enlarged just behind the head and flattened, giving them their common name. The rest of the body is conspicuously narrower and somewhat tapered. Galleries are usually not tightly winding in shape. Exit holes are usually oval in shape.
Stephanie Visker, MN Dept of Ag
Dave Cappaert, MI State University, bugwood.org
Flat-headed borers were most common in black ash found in surveys conducted by the Minnesota Department of Agriculture in 2007.
Flat-headed borer on black ash
Mark Abrahamson, MN Dept. of Ag
Flat-headed apple tree borer
Mark Abrahamson, MN Dept. of Ag
Mark Abrahamson, MN Dept. of Ag
Early flat-headed borer gallery
Flat-headed borer and gallery in black ash
Adult beetle emergence hole
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Recognizing Insect Galleries in Ash Trees
Long-horned Beetles (Round-headed Borers) Larvae are more or less cylindrical and taper gradually. Galleries are loosely meandering, can be nearly as wide as a pencil, and eventually dive deep into the sapwood. Exit holes may be round or oval.
Mark Abrahamson, MN Dept. of Ag
The Minnesota Department of Agriculture found galleries or larvae of long-horned beetles in 10 percent of sampled trees during surveys in 2007.
Jim Baker, NC State University, bugwood.org
Pupal chamber deep in wood
Mark Abrahamson, MN Dept. of Ag
Mark Abrahamson, MN Dept. of Ag
Red-headed ash borer
Round-headed borer
Mark Abrahamson, MN Dept. of Ag
Mark Abrahamson, MN Dept. of Ag
Close-up showing holes tunneled into wood
Emergence hole of long-horned beetle
Heavy infestation of round-headed borers resembles heavy EAB infestation
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Recognizing Insect Galleries in Ash Trees
Clearwing Moth
The Minnesota Department of Agriculture found clearwing larvae or galleries in 7 percent of sampled trees during surveys in 2007.
Mark Abrahamson, MN Dept. of Ag
➜
Clearwing moth larvae tunnel deeply into the wood and leave large round holes when they emerge as adults. Galleries made by the lavae are approximately the width of a pencil and deeply etched into the sapwood. Clearwing larvae have three pairs of legs behind the head, distinguishing them from round-headed and flathead borers, which have none.
➜
Jill Herberg
Mark Abrahamson, MN Dept. of Ag
Clearwing moth adult emergence hole with EAB exit hole below
Clearwing moth larvae
Whitney Cranshaw, CO State University, bugwood.org
Clearwing larval gallery starting at edge of mechanical girdle
Linda Treeful
Mark Abrahamson, MN Dept. of Ag
Clearwing pupal skin
Banded ash clearwing moths
Gallery at branch crotch
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Recognizing Insect Galleries in Ash Trees
Ash Cambium Miner
Galleries of ash cambium miner fly larvae are close to the surface of the sapwood, thin (width of pencil tip), and are either straight or a broad zig-zag.
Mark Abrahamson, MN Dept. of Ag
➜
Mark Abrahamson, MN Dept. of Ag
During 2007 Minnesota Department of Agriculture detection tree surveys, galleries or larvae of ash cambium miner were found in 35 percent of sampled trees.
Larva of ash cambium miner
Mark Abrahamson, MN Dept. of Ag
Mark Abrahamson, MN Dept. of Ag
Gallery of ash cambium miner present when tree was girdled
Galleries of ash cambium miner
Galleries of ash cambium miner
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What’s In That Woodpile? Identifying three groups of trees found in Minnesota woodpiles By Gary Johnson and Rebecca Koetter University of Minnesota, Department of Forest Resources - 2007
Joseph O’Brien, USDA Forest Service
Firewood identification and quarantine has been one of the important tactics for managing oak wilt (OW) (Figure 1) and Dutch elm disease (DED) (Figure 2) in the Upper Midwest. Both of these fungal diseases can be spread by insects from standing dead and dying trees to healthy trees or fresh pruning wounds in the case of oak wilt. Firewood from these trees may harbor insects that carry the diseases or produce fungal disease spores that attract insect carriers to the fungus. Thus, proper disposal or treatment of firewood from such diseased trees is extremely important.
Figure 1: Oak tree infected with oak wilt
Emerald ash borer kills both urban and rural trees, and all species of ash in the Fraxinus genus (black, green, white) are susceptible to this aggressive insect. Once again, monitoring the movement and storage of firewood is critical to a complete management program. The main way the insect is spreading across the Upper Midwest is through transportation of ash firewood from trees that were killed by the insect and still harbor the borer. Dave Hanson, U of MN/Dept of Forest Resources
Elm, oak, and ash have unique wood grain and bark characteristics. Often it is a combination of these characteristics that distinguishes the exact species, and sometimes even odors and colors help. Very often, firewood piles have wood from both mature tree trunks as well as smaller, younger branches. The bark from tree trunks and tree branches of the same species look very different, so firewood identification from bark samples alone can be difficult and confusing. Figure 2: Elm tree infected with Dutch elm disease
Penn.Dept of Conservation & Natural Resources
When bark is not enough to identify a piece of firewood, a close examination of the end grain is necessary. A sharp knife or a single-blade razor, a 10x hand lens, and a liquid that will enhance the end grain all help the process. Shellac or boiled linseed oil are both very effective end grain enhancers. Simply spray or brush the liquid on and the wood features (pores, rays, rings) become much more obvious. Even water works for a short time.
Please note that seemingly different trees are referred to as groups throughout this fact sheet. Trees within these groups often have similarities among bark, wood, and leaves.
Figure 3: Epicormic sprouting occurs about 2 years after EAB infestation.
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What’s in That Woodpile?
Identifying firewood: Types of end grain
Ring porous end grain: Small pores arranged in a wavy “tire track” pattern (Figure 3). Sapwood: white to tan-colored. Heartwood: brown to reddish brown.
There are three types of end grain used to identify firewood: ring porous, diffuse porous, and semi-ring porous. Of these three types, there is currently only one type–ring porous– that is characteristic of hardwood firewood that may house a harmful disease or insect in Minnesota.
Elm group (including hackberry) Peter Gillitzer, UMN
Ring Porous: All species in the elm group, oak group, and ash group have ring porous wood. Within an annual growth ring there will be two regions: springwood (distinctly larger pores) and summerwood (distinctly smaller pores as in Figure 1). Figure 3: Summerwood is wavy. Bark resembles bacon strips.
Dave Hanson, UMN
Peter Gillitzer, UMN
Bark: Cross-sections of American elm and rock elm bark have alternating bands of dark and light colored tissue that gives the appearance of bacon strips (Figure 3). Slippery elm does not have “bacon-strip” bark.
Figure 1: Group examples- oak, elm (including hackberry), and ash Figure 4: Corky hackberry bark.
Diffuse Porous: Within an annual growth ring, springwood and summerwood are not distinctly different. Wood within an annual ring looks uniform (Figure 2).
Peter Gillitzer, UMN
Gary Johnson, UMN
Exception: Hackberry, another member of the elm group, also has summerwood pores arranged in a wavy “tire track” pattern. However, it is not susceptible to DED. Also, its bark is characteristically corky and rough (Figure 4).
Figure 5: Stringy firewood characteristic of some elm species
Figure 2: Group examples- maple (including boxelder), birch, some poplars, basswood (a.k.a. linden), ironwood, buckeye, and black cherry
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Note: Split sections of American and rock elm can have stringy, long grain wood (Figure 5).
What’s in That Woodpile?
Oak group
Bark: Red oak group The smaller diameter pieces of wood have flat, gray, and smooth bark. Larger diameter pieces have ridged and furrowed bark (Figure 4).
Dave Hanson, UMN
Oak wilt affects all species of oak in Minnesota including the red oak group (Figure 1): northern red oak, northern pin oak, eastern pin oak, and black oak and the white oak group (Figure 2): white oak, bur oak, and swamp white oak. Red oak group identification is important because it is more susceptible to oak wilt than white oak and is the firewood most likely to have spore mats under the bark. Firewood from red oaks killed by oak wilt that have bark attached should be completely enclosed with black plastic for 12 months after tree death or until bark sloughs off.
Figure 4: Mature bark of red oak
Dave Hanson, UMN
Bark: White oak group Bark ranges from gray and platy (white oak) to deeply ridged and furrowed (bur oak) (Figure 5).
Dave Hanson, UMN
Figure 1: Species of red oaks have pointed leaf margins.
Figure 5: Mature bark of bur oak
Figure 2: Species of white oaks have rounded leaf margins.
Rebecca Koetter, UMN
Ring porous end grain: Large wood rays are clearly visible to the naked eye. Within an annual growth ring, springwood has distinctly larger pores versus the smaller pores of summerwood (Figure 3).
Peter Gillitzer, UMN
Figure 6: Red oak sprayed with NaNO2. Notice that wood color does not significantly change, not even with time lapse.
Rebecca Koetter, UMN
Dave Hanson, UMN
Sodium Nitrite (NaNO2) Test: Applying a 10 percent solution of sodium nitrite to the heartwood makes the natural light brown color of the red oak group heartwood only slightly darker (Figure 6). However, it turns the white oak group heartwood yellow-orange, then red-brown, and then dark green or purple to black (Figure 7).
Figure 7: White oak sprayed with NaNO2. Left: color change within seconds of application. Right: color change within minutes of application.
Notes: Freshly cut or split red oak has a very distinct odor, sweet or rancid. Heartwood of red oak is light reddish brown versus the light to dark brown heartwood of white oak.
Figure 3: All species in the oak group have rays visible to the unaided eye. The growth ring includes one season of springwood and one of summerwood.
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What’s in That Woodpile?
Ash group
Peter Gillitzer, UMN
Ring porous end grain: Within an annual growth ring, springwood has large obvious pores with an abrupt transition to summerwood that has very small pores (Figure 8).
Figure 8: Cross-section of green ash. Notice no obvious wood rays are present.
Note: Unlike the oak group, large rays are absent to the naked eye.
Dave Hanson, UMN
Bark: Deeply furrowed, narrow ridges that are diamond to canoe-shaped; ash gray to ash brown (Figure 9).
Figure 9: Mature bark of green ash
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What’s in That Woodpile?
Glossary
References
Cooperative Extension Service. Is it red oak or white oak? Color test will tell. University of Wisconsin Extension. G7FSRWO. (The sodium nitrite test- NaNO2)
Diffuse porous- all pores are of similar size and can be found evenly distributed throughout the growth rings. Growth ring- contains two layers (springwood and summerwood) of cells resulting from one year of growth.
Core, H.A., Cote, W.A., and A.C. Day. 1979. Wood structure and identification. Syracuse University Press. Syracuse, New York.
Heartwood- nonliving and commonly dark-colored wood in which no water transport occurs; it is surrounded by sapwood.
Hoadley, R.B. 2000. Understanding wood: a craftsman’s guide to wood technology. Tauton Press, Inc. Newtown, CT.
Ring porous- pore sizes found in springwood and summerwood are very different, forming conspicuous bands.
Sharp, J.B. 1990. Wood identification: a manual for the non-professional. University of Tennessee. Agricultural Extension Service. Publication 1389. Raven, P.H., Evert, R.F. and S.E. Eichhorn. 1999. Biology of plants, 6th Edition. Worth Publishers, New York.
Sapwood- outer part of the wood of stem or trunk, usually distinguished from the heartwood by its lighter color. Water transport takes place in sapwood. Springwood- large cells formed when the tree is rapidly growing and are usually visible without a hand lens.
White, M.S. 1980. Wood identification handbook: commercial woods of the Eastern United States. Colonial Hardwoods, Inc. Falls Church, VA.
Summerwood- small to tiny cells formed during slower growth period of summer and are not usually visible without a hand lens.
Technical Advisors Harlan Petersen Extension Specialist and Assistant Professor University of Minnesota Jennifer Juzwik Northern Research Station, USDA Forest Service Minnesota Shade Tree Advisory Committee Information Transfer subcommittee
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Do I Have Gypsy Moth? The gypsy moth is an invasive forest pest from Europe and is one of the most damaging tree defoliators currently in the United States. Aspen and oak top the list of over 500 trees and plants fed on by gypsy moth caterpillars.
Minnesota Department of Agriculture
Introduced to the United States in 1869, gypsy moth spread slowly across New England over the first 100 years, primarily through caterpillar movement. Over the next 40 years, gypsy moth quickly spread as a result of human activities (egg masses attached to motorized vehicles, outdoor articles, and firewood). Today the area infested with gypsy moth spans across the eastern United States and into Wisconsin. The United States Forest Service began a Slow-The-Spread Program to help states on the advancing edge of gypsy moth infestation delay its establishment.
Minnesota Department of Agriculture
Female and egg mass
Opuntia,GDFL
Larval emergence
Minnesota Department of Agriculture
Male gypsy moth (actual size 3/4–1 1/2 inch wingspread)
John H Ghent, USDA Forest Service, bugwood.org
Minnesota Dept. Agriculture
Gypsy moth pupae (actual size 3/4–1 1/2 inch long)
Gypsy moth caterpillar (actual size)
Female gypsy moth (actual size 1–2 inch wingspread)
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Do I Have Gypsy Moth?
Gypsy Moth Life Cycle Egg Masses
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Larva Stage
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Pupa Stage
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Adult Stage
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
First: identify which life stage the insect is in: adult, egg mass, caterpillar or pupa (cocoon). Next: review the gypsy moth life cycle table above to see which stage is active at what time of year.
Jeff Hahn, UMN
Jeff Hahn, UMN
Finally: could it be something that is similar to gypsy moth? Compare these photos.
Eastern tent caterpillar
Jeff Hahn, UMN
PA Dept. of Cons. and Nat. Res.
Cecropia moth caterpillar
Forest tent caterpillar
Minnesota Dept. Agriculture
Jeff Hahn, UMN
Fall webworm
Steve Katovich, USFS, bugwood.org
Yellow-necked caterpillar
White-marked tussock moth caterpillar
Spiny elm caterpillar
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Do I Have Asian Long-horned Beetle?
Kenneth Law, USDA APHIS PPQ , bugwood.org
The Asian long-horned beetle (ALB) is another exotic insect that likely came to the U.S. from Asia in wood packing material. It was discovered in Brooklyn, New York in 1996, and since then has destroyed millions of trees in New York, New Jersey, Illinois, and Massachusetts. ALB has a one-year life cycle. The female beetle chews a visible depression in a hardwood tree and lays a single egg beneath the bark. She can lay 30-60 eggs in her lifetime of two weeks to three months. The larva chews through the sapwood and eventually moves deeper to feed on woody tissue. This feeding and tunneling disrupts the flow of water and nutrients in the tree, causing it to weaken and die. The larvae pupate closer to the surface of the bark, and adults emerge in July and August, chewing a dime-sized exit hole.
Asian long-horned beetle
Trees at risk include ash, birch, elm, mountain-ash, hackberry, horsechestnut, maple, poplar, and willow.
Dennis Haugen, USFS
Signs and symptoms of ALB include crown die-back, shallow depressions in the bark where eggs are laid, sap seeping from wounds in tree, dime-sized, perfectly round exit holes, and sawdust-like frass (excrement) on ground or in branch crotches.
Frass
Symptoms of ALB
Kenneth Law, USDA APHIS PPQ , bugwood.org
E. Richard Hoebeke, Cornell University, bugwood.org
Two long-horned beetles native to Minnesota that may be confused with ALB are the cottonwood borer and white-spotted sawyer. The cottonwood borer is similar in size to ALB, but is white with black markings. Markings on the white-spotted sawyer are variable, from scattered spots to a single white spot in the middle of the upper back.
Asian longhorned beetle exit holes
Asian longhorned beetle larva
Egg-laying site
Cottonwood borer
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Joseph Berger
Charles T. Bryson, USDA ARS
Dennis Haugen,USFS
PA Dept.of Cons. and Nat.Res. bugwood.org
In spite of being so destructive, the adult beetles are a beautiful glossy black with irregular white spots, and may have blue feet. Both male and female are 1 to 1 ½ inches long. The antennae are at least as long as the body, and have black and white bands.
White-spotted sawyer
Do I Have Sirex Woodwasp?
Dennis Haugen
Sirex woodwasp belongs to a family of large, nonstinging wasps whose larvae bore into wood. They can easily be distinguished from other wasps because of their large size, broad “waist� and long, speciallymodified ovipositor (egg-laying tube), used to insert eggs into wood. Although similar woodwasps are native to Minnesota, the exotic Sirex noctilio (Sirex) is native to Europe, Asia and North Africa where it attacks Scotch and Austrian pines as a secondary pest. It was discovered in the United States in New York and Canada in 2005, and since then has been found in Michigan, Ohio, Pennsylvania, and Vermont. Sirex has been very destructive to plantations of pines introduced from North America to South Africa, South America, New Zealand, and Australia. In the United States, overstocked pine plantations and stressed forest stands of red, white, ponderosa, lodgepole, Monterrey and jack pine are susceptible.
Steve Katovich, USFS, bugwood.org
Adult sirex
As with the invasive emerald ash borer, Sirex can attack healthy, living pines, while our native woodwasps attack only dead and dying trees. Needles on infested pines wilt, turning pale green, to yellow, to red within six months after attack. Trees may have beads of resin or running sap from egg-laying sites. Woodwasps are robust insects, usually 1 to 1 1/2 inches long. Sirex adults are dark metallic blue or black, and the middle segments of the male are orange. The legs are reddish-yellow; males have black hind legs. Males have a spear-shaped plate at the end of the body, and females also have a long ovipositor underneath this plate. Larvae are creamy white and resemble other large wood-boring larvae, but they have a distinctive dark spine on the end of the abdomen.
Pine damage
Bleeding sap
Resin beads
29
Paula Klasmer
Kevin Dodds, USFS
Sirex has a one-year life cycle. The female is attracted to stressed pines and drills into the outer sapwood with her ovipositor, injecting a fungus, mucus, and 25-450 eggs. The fungus and mucus work together to make a suitable environment for the larvae, at the same time killing the tree. The larvae feed on the fungus as they tunnel through the wood for approximately 11 months. The larvae pupate closer to the surface of the bark, and adults emerge from July through September, chewing a round exit hole 3/8-inch in diameter.
Dennis Haugen
Paula Klasmer, Instituto Nacional de Tecnologia Agropecuaria, bugwood.org
ALB (top) and Sirex larvae
Sirex damage
Does My Tree Have Thousand Cankers Disease of Walnut? Is my tree a black walnut? Black walnut is native to Minnesota and has alternate branching (see page 11). Leaves are compound with 15-23 leaflets, the terminal leaflet often missing. Leaves are fragrant when crushed. The round, light green husks are 1 1/2 – 2 inches thick and have a grainy surface.
USFS
How do I recognize thousand cankers disease of walnut (TCD)? During late June to late August, thinning foliage and dieback in the crown become apparent. Leaves may be wilting, yellow, or brown. Very carefully scrape off the outer bark of a branch that is larger than 1 ½ inches in diameter. If the tree is infected with TCD, the inner bark will have brownish spots instead of inner bark that is completely cream-colored or pale green. The branches may also have numerous tiny exit holes, caused by bark beetles, whose meandering tunnels will be visible beneath the bark.
W. Cranshaw, Colorado State University, bugwood.org
Cankers
USFS
Entry or exit holes
Wilt
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Does My Tree Have Thousand Cankers Disease of Walnut?
Butternut
Also a native of Minnesota, butternut has alternate branching. The compound leaves have 11-19 leaflets. The oblong fruit is covered with sticky hairs.
Chris Evans, River to River CWMA, bugwood.org
Honeylocust
Paul Wray, Iowa State University, bugwood.org
Bill Cook, Michigan State University, bugwood.org
Trees commonly mistaken for black walnut
Honeylocust is a common boulevard tree. It has alternate branching with compound or doubly-compound, small leaflets. Stems have a zig-zag appearance. The fruit is a brown to black, 7 to 8-inch pod that curves and coils when mature.
Dave Hanson, UMN
Kentucky coffeetree
Dave Hanson, UMN
Like honeylocust, the leaves are alternate with doublycompound leaflets, but Kentucky coffeetree has fewer leaflets and the lower leaflets on each stalk are often not doubly-compound. The fruit is a brownish black, leathery pod from 5-10 inches long. The pods hang on through the winter.
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What Can I Do If I Suspect I Have Found a Forest Pest? After you have gone through the previous pages, if you cannot easily rule out one of the forest pests described, contact the Minnesota Department of Agriculture’s Arrest the Pest hotline at Arrest.The.Pest@ state.mn.us or 888-545-6684 to report your suspicions.
Additional Resources Emerald Ash Borer Prevention, Early Detection, and Rapid Response www.mda.state.mn.us/en/plants/pestmanagement/eab.aspx Gypsy Moth www.mda.state.mn.us/plants/pestmanagement/gmunit.aspx Asian Long-horned Beetle www.uvm.edu/albeetle/identification/index.html Sirex Woodwasp www.na.fs.fed.us/spfo/pubs/pest_al/sirex_woodwasp/sirex_woodwasp.htm Thousand Cankers Disease of Walnut www.colostate.edu/Dept/bspm/extension%20and%20outreach/thousand%20cankers.html What’s Wrong With My Plant? www.extension.umn.edu/gardeninfo/diagnostics/index.html University of Minnesota Gardening Information www.extension.umn.edu/gardeninfo/components/info_trees.html#problems Center for Invasive Species and Ecosystem health www.invasive.org/index.cfm
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Tree Genera of Minnesota and Invasive Pests of Concern that may be Contained In or On Wood
Type
Genus
Name
Asian long-horned beetle 1
Emerald ash borer
Gypsy moth 2
Sirex woodwasp 3
No
No
Unlikely
Unlikely
Possible
No
Conifer
Abies
Fir
Hardwood
Acer
Maple, boxelder
Very good host
No
Non Native
Aesculus
Horse Chestnut
Very good host
No
Possible
No
Hardwood
Alnus
Alder
No data
No
Preferred host
No
Hardwood
Amelanchier
Serviceberry
No data
No
Preferred host
No
Hardwood
Betula
Birch
Good host
No
Preferred host
No
Hardwood
Carpinus
Blue beech
No data
No
Possible
No
Hardwood
Catalpa
Catalpa
No data
No
Unlikely
No
Hardwood
Carya
Hickory
No data
No
Possible
No
Hardwood
Celtis
Hackberry
Occasional host
No
Possible
No
Hardwood
Cornus
Dogwood
No data
No
Unlikely
No
Hardwood
Crateagus
Hawthorn
No data
No
Preferred host
No
Non Native
Eleagnus
Russian olive
No data
No
Possible
No
Hardwood
Fraxinus
Ash
Occasional host
Yes
Unlikely
No
Hardwood
Gleditsia
Honeylocust
No data
No
Possible
No
Hardwood
Gymnocladus
Kentucky coffeetree
No data
No
Possible
No
Hardwood
Juglans
Walnut / Butternut
No data
No
Possible
No
Conifer
Juniperus
Juniper
No
No
Possible
No
Conifer
Larix
Tamarack
No
No
Possible
Unlikely
Hardwood
Malus
Apple
Questionable host
No
Preferred host
No
Hardwood
Morus
Mulberry
Questionable host
No
Unlikely
No
Hardwood
Ostrya
Ironwood
No data
No
Possible
No
Conifer
Picea
Spruce
No
No
Possible
Unlikely
Conifer
Pinus
Pine
Hardwood
Populus
Poplar
Hardwood
Prunus
Hardwood
No
No
Possible
Yes
Occasional host
No
Preferred host
No
Cherry, plum
Questionable host
No
Possible
No
Quercus
White oak, red oak
Questionable host
No
Preferred host
No
Non Native
Rhamnus
Buckthorn
Non Native
Robinia
Black Locust
Hardwood
Salix
Hardwood
No data
No
Unlikely
No
Questionable host
No
Possible
No
Willow
Very good host
No
Preferred host
No
Sorbus
Mountain-ash
Occasional host
No
Preferred host
No
Conifer
Thuja
White cedar
No
No
Unlikely
No
Hardwood
Tilia
Basswood
Questionable host
No
Preferred host
No
Hardwood
Ulmus
Elm
Very good host
No
Possible
No
1 www.uvm.edu/albeetle/hosts.htm 2 Preferred hosts from www.na.fs.fed.us/SPFO/pubs/fidls/gypsymoth/gypsy.htm. In addition to preferred hosts, egg masses can be laid on any type of tree, firewood or other outdoor article. 3 www.aphis.usda.gov/plant_health/plant_pest_info/sirex/downloads/sirex-pra.pdf
33
Notes
34
Additional photo credits
Wilt source photo front cover: USFS Asian long-horned beetle source photo page 2: Kenneth Law, USDA APHIS PPQ Flat-headed apple tree borer source photo page 5: David Cappaert, Michigan State University, Bugwood.org EAB source photo page 24: Pennsylvania Department of Conservation and Natural Resources – Forestry Archive, Bugwood.org Woodpile source photo page 25: Deborah Rose, MNDNR Gypsy Moth source photo page 32: John H Ghent, USDA Forest Service, bugwood.org EAB source photo back cover: Pennsylvania Department of Conservation and Natural Resources – Forestry Archive, Bugwood.org
For more information, contact: Department of Natural Resources 500 Lafayette Road St. Paul, MN 55155-4040 651-296-6157 (Metro Area) 1-888-MINNDNR (646-6367) (MN Toll Free) www.mndnr.gov ©2012, State of Minnesota, Department of Natural Resources Equal opportunity to participate in and benefit from programs of the Minnesota Department of Natural Resources is available to all individuals regardless of race, color, creed, religion, national origin, sex, marital status, status with regard to public assistance, age, sexual orientation, membership or activity in a local commission, or disability. Discrimination inquiries should be sent to MN-DNR, 500 Lafayette Road, St. Paul, MN 55155-4031; or the Equal Opportunity Office, Department of the Interior, Washington, DC 20240. This document is available in alternative formats to individuals with disabilities by calling 651-296-6157 (Metro Area) or 1-888-MINNDNR (MN Toll Free) or Telecommunication Device for the Deaf/TTY: 651-296-5484 (Metro Area) or 1-800-657-3929 (Toll Free TTY). This project was funded in part by the USDA Forest Service. The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or part of an individual’s income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET Center at 202-720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, DC 20250-9410, or call 1-800-795-3272 (voice) or 202-720-6382 (TDD). USDA is an equal opportunity provider and employer.
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