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Last Update 17/12/01 Customized Elm Tree Care Kits Did you know a new wild bird seed has been developed and tested that Custom care kits include actually repels squirrels? How Trees Work specialized and innovative soil Click here to learn about Squirrel Proof Wild Bird treatments designed to promote About Elm Trees Seed. root development and the long- Caring for Your Elm term health and vitality of your Elm Tree Diseases elm. A healthier elm will be better able to fight against Dutch elm disease. Elm Tree Links more Quick Elm Facts
Elm Tree Registry Visit TreeHelp.com for all of your tree and shrub Register your elm tree to receive customized care care needs advice...more.
Return of the Stately Elm
Writer and broadcaster Jamie Swift examines the Canadian city of Winnipeg's struggle to combat Dutch elm disease. Through the work of community groups like the Coalition to Save the Elms and innovative technology, the city has achieved substantial success... more.
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New Treatments for Elms in History Elm Tree Links Dutch Elm Disease? Look at elms in the context of Links to a growing community of Researchers examine new ways to human history. academics, homeowners and fight this devastating disease. professional tree care experts. Elms in Literature Elm Species Quick Elm Facts Read what some of the world's Elms come in many sizes and leading poets and authors have Discover something new and shapes...learn about them all. written of the elm. interesting about the elm.
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Home > How Trees Work Last Update 30/08/00
What is a ring-porous vascular system? What is the difference between wild-type How Trees Work and cloned trees? Types of Trees Important Facts Structure of a Tree How Trees Breathe
How Trees Drink
Find the answers to these questions and About Elm Trees more by clicking on one of the topics below: Caring for Your Elm Elm Tree Diseases More Info... Elm Tree Links Important Facts Types of Trees Quick Elm Facts Structure of a Tree How Trees Drink How Trees Breathe
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Home > How Trees Work > Types of Trees Last Update 30/08/00
Angiosperms vs. Gymnosperms
How Trees Work Trees are scientifically divided into two major categories: angiosperms and gymnosperms. Types of Trees Important Facts Angiosperms are flowering plants and their seeds are encased in a protective Structure of a Tree ovary. This division contains the larger number of species can be further How Trees Breathe subdivided into dicots and monocots. Dicots have two seed leaf structures and How Trees Drink include many broadleaf trees such as the elm, maple and oak. Monocots have one seed leaf structure and include species such as the palm. About Elm Trees Caring for Your Elm Gymnosperms, on the other hand, do not produce flowers. Their seeds have Elm Tree Diseases structures such as cones, rather than a protective ovary. Conifers (needle-leaf
Elm Tree Links trees) are a major group of gymnosperms. Quick Elm Facts
Deciduous vs. Coniferous
Trees can also be divided into deciduous and coniferous categories.
Deciduous trees are also known as broadleaf trees because the leaves are generally larger and wider than those of conifers. The larger leaf size means a greater surface area for photosynthesis, but it also mean the leaf is too fragile to withstand winter conditions. Therefore, most deciduous trees drop their leaves in autumn.
Coniferous trees keep their leaves throughout the year, shedding only the oldest leaves. Usually these leaves are lower down on the tree and do not receive as much sunlight as newly developed leaves higher up. Some of the best-known members of the conifer family are pines, spruces, firs, and hemlocks. The cones of the conifers are its flowers.
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Home > How Trees Work > Important Facts Last Update 30/08/00
Some trees are wild, others are cloned
How Trees Work It's easy to think that all trees of a species are alike. This is only true, however, of certain species. Most trees are wild-type trees, meaning that their genetic make- Types of Trees ups are as dissimilar as individual humans. An example of a wild-type is an elm. Important Facts Structure of a Tree How Trees Breathe Other trees have been cloned to produce many trees with identical genes. This is How Trees Drink usually done to guarantee the presence of certain favourable characteristics of the tree. Examples include apple and pear trees.
About Elm Trees This distinction is important when treating diseases. In a wild-type tree, each tree Caring for Your Elm will react differently. Elm Tree Diseases Elm Tree Links Quick Elm Facts
Some trees are ring-porous, some are diffuse-porous
Trees can be divided into ring-porous or diffuse-porous types. This refers to the structure of the vascular system.
The vascular system of diffuse-porous trees (such as a birch) is characterized by vessels spread evenly throughout the sapwood. These vessels are Diffuse-Porous produced regularly during the growing season.
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The vessels of a ring-porous tree (such as an elm) are generally larger and concentrated in the outermost layer Ring-Porous of sapwood. These vessels are produced early in the season.
This is significant because it affects a tree's susceptibility to vascular wilt diseases. Ring-porous vascular systems are very efficient, but are much more vulnerable to blockage. The elm's vulnerability to Dutch elm disease is an case in point.
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Home > How Trees Work > Structure of a Tree Last Update 30/08/00
How Trees Work Leaves Types of Trees Important Facts The leaves convert carbon dioxide into oxygen and provide the Structure of a Tree tree with energy to grow and fight disease...more. How Trees Breathe How Trees Drink Roots About Elm Trees The roots provide structural stability to the tree and are the means by which it Caring for Your Elm takes up water and minerals...more. Elm Tree Diseases Elm Tree Links Bark Quick Elm Facts Bark is the outer protective covering of tree trunks. The form and
structure of bark can differ greatly from tree to tree...more.
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Home > How Trees Work > How Trees Breathe Last Update 30/08/00 Acting as an enormous "carbon sink", trees soak up carbon dioxide from the air, producing life-giving oxygen in return. In fact, a medium-sized tree generates the How Trees Work same amount of oxygen as each one of Types of Trees us needs to breathe. Important Facts Structure of a Tree In a tree, 'breathing' takes place in the How Trees Breathe leaf. Chlorophyll (the substance causing How Trees Drink the green colour) absorbs the CO2 and uses it along with water to dissolve About Elm Trees minerals taken up through the roots. After the chemical reaction is completed, the Caring for Your Elm leaf releases oxygen and water vapor through its pores. Elm Tree Diseases Elm Tree Links Quick Elm Facts
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Home > How Trees Work > How Trees Drink Last Update 30/08/00 There are two ways that a tree can take in water: through the leaves and through the roots.
How Trees Work Trees absorb small amounts of moisture from the air through their leaves and their bark. Most of their water, however, comes via the roots. Types of Trees Important Facts Water enters the roots through thin membranes at their tips. The tree's vascular Structure of a Tree system draws the water up through the trunk and distributes it to the leaves. The How Trees Breathe leaves use the water to dissolve minerals. Excess water goes back to the air How Trees Drink through pores in the leaf - a process called transpiration.
About Elm Trees Caring for Your Elm Elm Tree Diseases Elm Tree Links Quick Elm Facts
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Home > About Elms Last Update 30/08/00 The majestic elm is one of the most beloved of all our How Trees Work trees.
Dutch elm disease has About Elm Trees taken its toll and sadly the elm is disappearing from The Elm Story our landscape. Identifying Elms Elm Species But through community Biology of Elms action, new research and a concentrated effort, the elm Caring for Your Elm can make a comeback. Elm Tree Diseases Elm Tree Links Perhaps soon, the stately elm can reclaim its rightful place in our lives. Quick Elm Facts Click on one of the following to learn more.
More Info... The Elm Story Identifying Elms Elm Species Biology of Elms
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Home > About Elms > The Elm Story Last Update 30/08/00
The adjectives “majestic” and “stately” leap to mind when How Trees Work describing elms. These trees are truly one of our most recognizable trees whether lining our streets and boulevards or standing on guard in a farmer's field. The number of “Elm” streets, parks and buildings demonstrates About Elm Trees just how much a part of our lives these trees became.
The Elm Story Identifying Elms Elm Species To learn more, click on one of the topics below: Biology of Elms
Caring for Your Elm Elm Tree Diseases More Info... Elm Tree Links The Cultivated Elm Elms in Literature Quick Elm Facts Living History Elms in Mythology
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Home > About Elms > Identifying Elms Last Update 30/08/00
Elm trees make up an important part How Trees Work of the North American landscape and identifying them is the first step in preventing their demise from Dutch elm disease. Although there About Elm Trees are differences amongst the different species of elms, this section will The Elm Story focus on the American elm, which is Identifying Elms Elm Species the most widespread. Biology of Elms
Caring for Your Elm Elm Tree Diseases Elm Tree Links To quickly identify an elm, look at the Quick Elm Facts silhouette, the leaves and the bark.
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How Trees Work Click on one of the elm species below to discover more.
About Elm Trees Common Name : Scientific Name
The Elm Story American Elm : Ulmus americana L. Identifying Elms Rock Elm : Ulmus Thomasii Sarg. Elm Species Slippery Elm : Ulmus rubra Muehl. Biology of Elms
Scotch Elm : Ulmus glabra Huds.
Caring for Your Elm Camperdown Elm : Ulmus glabra camperdownii Elm Tree Diseases Siberian Elm : Ulmus pumila L. Elm Tree Links English Elm : Ulmus procera Salisb. Quick Elm Facts Japanese Zelkova : Zelkova serrata Thunb. Mak. Winged Elm : Ulmus alata Chinese or Hokkaido Elm : Ulmus parvifolia
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Home > About Elms > Biology of Elm Trees Last Update 30/08/00
40 Million Years Old How Trees Work Elm trees first made an appearance in the Miocene period, about 40 million years ago. Originating in central Asia, the tree has flourished and has established itself over About Elm Trees most of North America, Europe and Asia.
The Elm Story Identifying Elms Vascular Plants Elm Species Biology of Elms Understanding how an elm tree lives and breathes is important in understanding how Dutch elm disease has spread. Caring for Your Elm Just like the human cardio-vascular system of arteries and veins, a tree has a Elm Tree Diseases vascular system of long thin vertical tubes. This vascular system takes the water Elm Tree Links and nutrients from the roots and distributes them throughout the tree. Quick Elm Facts In an elm, the cells that produce the vascular tubes are found just beneath the bark in a layer called the cambium. After each growing season, the inner part of the cambium dies. A new cambium is formed the next spring. If you cut through a tree trunk, you can see the tree rings. Each ring is a cambium layer.
An elm tree has a very efficient vascular system but that also makes it vulnerable. The same qualities that allow the elm to efficiently draw water to its upper leaves also give fungi and insects easy access to the inner workings of the tree. The fungus that causes Dutch elm disease, for example, essentially clogs the elm tree’s vascular system.
Dutch elm disease can be treated. However, because the tree’s vascular system is renewed every year, treatments have to be repeated annually.
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Last Update 26/04/01
How Trees Work Trees are a constant in our lives. They seem to last forever (they certainly outlive us) and their branches About Elm Trees cast a protective shadow over generation after generation. Caring for Your Elm Tree So strong and hardy are trees that we often assume that they endure just about any hardship without any Fertilizing help from us. Pruning Lawn Care But trees outside their natural setting are often under Watering tremendous stress. Obstacles Disposal And yes, there is much we can do to help them.
Elm Tree Diseases Fertilizing; pruning; giving the tree room to grow and breathe. We can help our Elm Tree Links trees to thrive and ensure that they can continue to give pleasure for generations Quick Elm Facts to come.
Click on one of the following for more information:
Fertilizing Watering Pruning Obstacles to Growth Lawn Care Disposal of Dead Elms
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Home > Caring for your Elm > Fertilizing Last Update 26/04/01 Elms should be fertilized once or twice a year. However, not just any fertilizer will do and using the wrong type of fertilizer can actually increase the chances that How Trees Work your tree will contract Dutch elm disease. Avoid standard "one-size-fits-all" lawn About Elm Trees and turf fertilizer. In particular, fertilizers that release large amounts of Nitrogen quickly into the soil can encourage structurally weak growth that could attract the elm bark beetles carrying the Dutch elm disease fungus. Aside from the Caring for Your formulation, the method of fertilization differs from that of your grass. In order to Elm Tree give your trees the most benefit, the fertilizer must be placed below the grass Fertilizing roots. Pruning Lawn Care To find out how to obtain fertilizer specially selected for use on elm trees, click Watering here. Obstacles Disposal
Elm Tree Diseases Elm Tree Links Quick Elm Facts
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Home > Caring for your Elm > Pruning Last Update 30/08/00 Pruning is one of the most important ways we can help our trees.
How Trees Work Regular removal of dead branches: About Elm Trees ● decreases the breeding area for disease-carrying insects ● Caring for Your promotes growth ● removes safety hazards Elm Tree ● improve the tree’s appearance. Fertilizing Pruning Take care! Improper or untimely pruning can do more harm than good. Lawn Care Watering Obstacles Click on a topic to learn more: Disposal
Elm Tree Diseases Elm Tree Links Why Prune? Timing Quick Elm Facts Types of Pruning Pruning Pitfalls Technique
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Home > Caring for your Elm > Lawn Care Last Update 30/08/00 Grass and trees are not always the best of friends.
How Trees Work In natural settings, the ground around large shade trees is covered with leaves. As About Elm Trees the leaves decompose, they release nutrients which the tree needs. Not so in our cities where are trees are surrounded by grass. The grass actually competes with Caring for Your the tree for water and nutrients. Elm Tree How you care for your lawn can affect the health of your elm tree. Fertilizing Pruning Lawn Care Watering Obstacles Disposal Fertilizing Scatter fertilizer around a tree and you will end up with very healthy grass. Tree food stakes inserted into the ground release nutrients below the grass layer. Use Elm Tree Diseases fertilizers specifically designed for shade or elm trees. Elm Tree Links Quick Elm Facts
Mowing Take care when mowing. Lawn mowers can damage a tree. Better yet, avoid the problem by keeping the grass back from the base of the tree. A buffer zone of loose soil or mulch is ideal.
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Home > Caring for your Elm > Watering Last Update 30/08/00 Water is, of course, vital to the survival and health of a tree. You can provide a tree with the moisture it needs. How Trees Work About Elm Trees
Caring for Your Elm Tree How Fertilizing Pruning A tree takes moisture in through its root system. At the tip of the root, there are Lawn Care tiny structures called root hairs which absorb moisture from the surrounding soil. Watering This is where you want to target your watering. Obstacles Disposal In an elm, the tips of the roots are usually located outside of the weeping or drip line. This is the outermost extent of the crown of the tree. Therefore, sprinkling Elm Tree Diseases water onto the trunk will have little or adverse effect on the tree's health. Elm Tree Links Quick Elm Facts It is important to remember that grass and other vegetation compete with a tree for moisture. As a result, sprinkling is not a very efficient method of watering. Firstly, there is extensive evaporation, and secondly the grass absorbs a large percentage of this water.
A preferable method of watering is to soak the ground outside the weeping line with a hose. There are also special devices that allow you to apply moisture directly into the ground near the roots.
It is important to allow the soil to dry in between waterings. If the soil is constantly wet, it can easily become compacted, hindering gas exchange with the air.
When
Often nature provides all the moisture a tree needs. It is times of drought or in certain urban environments when watering is required.
● Examine the leaves: wilting, browning, discoloured margins - these are all signs your tree needs moisture
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● Examine the grass: if your lawn is yellowing, there is good chance that your tree lacks moisture even if it has yet to show signs. ● Examine nearby trees: If other trees in your area show signs of drought, your tree may be next. Often other species, such as maples, show signs earlier than elms giving an early warning signal.
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Home > Caring for your Elm > Obstacles to Growth Last Update 30/08/00 Sidewalks, utility lines, houses, poor soil, polluted air - it is a wonder that our trees do as well as they do. We can help our trees thrive and grow by managing some of How Trees Work the obstacles they face. About Elm Trees
Caring for Your Elm Tree Physical Obstacles Fertilizing Pruning Due to the sheer size of a mature elm, things tend to get in its way. The easiest Lawn Care way to avoid conflicts with physical obstacles is to plan around them. This means Watering care when planting. Obstacles Disposal A young tree always looks lonely in a garden. But that spindly litle tree will eventually grow to be more than 30 metres tall with a crown that will engulf Elm Tree Diseases everything nearby. Elm trees should be planted at least 5 metres (15 feet) away Elm Tree Links from houses. Quick Elm Facts Never plant an American Elm under utility lines. The result will be frequent and costly pruning.
Construction
When doing construction around an elm tree, care must be taken to avoid cutting the root system.
It is difficult for the tree to close root wounds. Cutting roots can leave the tree vulnerable to attack by a fungal disease such as Dutch Elm Disease.
If cutting the root is unavoidable, attempt to make clean cuts exposing as little surface area as possible.
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Home > Caring for your Elm > Disposal of Dead Elms Last Update 30/08/00 A dead elm tree is a threat to all the other elm trees in How Trees Work the neighbourhood. About Elm Trees Because dead wood is an Caring for Your ideal breeding ground for the elm bark beetle and Elm Tree the DED fungus, disposal Fertilizing of dead limbs and trees Pruning must be done properly and Lawn Care quickly. Watering Obstacles If you have a dead elm, Disposal first remove the major limbs and proceed to cut down the tree. Remember taking trees down is not a job for the amateur. Call a tree removal Elm Tree Diseases company. Some municipalities offer disposal services for large trees. Elm Tree Links Wood should be burned immediately. It should not be stored. Some communities Quick Elm Facts have strict by-laws prohibiting the storage and transportation of elm firewood.
If there is insufficient space for burning, the wood can be buried.
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Home > Elm Tree Diseases Last Update 30/08/00 While elm trees are extremely hardy, they are still susceptible to attack from diseases or insects.
How Trees Work If your elm tree seems unhealthy, it could be suffering About Elm Trees from one of the diseases on the left. Caring for Your Elm
Elm Tree Diseases
Dutch Elm Disease Elm Leaf Beetle Verticillium Wilt Elm Yellows Cankers Wetwood Elm Leaf Black Spot Elm Leaf Miner Asian Longhorned Beetle
Elm Tree Links Quick Elm Facts
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Home > Elm Tree Diseases > Dutch Elm Disease Last Update 30/08/00
Dutch elm disease (DED) is the most devastating shade tree disease in North America. It is a wilt How Trees Work disease with an extremely high fatality rate among About Elm Trees elms. Caring for Your Elm
How Dutch Elm Disease Kills Elm Tree Diseases Dutch elm disease (or DED) is caused by a fungus. After the disease is contracted, spores rapidly reproduce and spread toxins Dutch Elm Disease throughout the tree. History Transmission Symptoms Prevention The fungus blocks the water-conducting or vascular system of the tree preventing Treatments water and minerals from reaching the branches and leaves. The leaves wilt and New Research eventually the tree dies.
Elm Leaf Beetle Verticillium Wilt The Fungus Elm Yellows The fungus Ophiostoma (Ceratocystis) ulmi attacks various species of elm. It can Cankers kill a tree within a few weeks or it can kill it gradually over a period of years. Wetwood Elm Leaf Black Spot There are two strains of the fungus in North America - the non-aggressive strain Elm Leaf Miner (O. ulmi) and the aggressive strain (O. novo-ulmi). While the elm’s natural Asian Longhorned Beetle defense mechanism tries to fight off the fungus, the aggressive strain often moves too quickly for the tree to react without human intervention.
Elm Tree Links How Long Does It Take for the Fungus to Destroy a Tree? Quick Elm Facts That depends on the age and health of the tree. A younger fast-growing tree can die quickly. Some younger trees have some natural resistance to DED. However, this resistance tends to wear off after 15-20 years. Slow growing older trees can linger for a year or two.
Is There a Cure for DED? When an elm tree detects the presence of the fungus, it produces a number of defensive compounds. ‘Mansonones’, for example, are toxic to the DED fungus. However, left to its own devices, a tree cannot produce enough to fight off the disease.
Researchers are now learning how to stimulate the tree’s natural defenses to produce larger quantities of mansonones. It is a promising breakthrough. For more information on the new DED treatment, click here.
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For more information on Dutch elm disease, click on one of the topics below:
History of Dutch elm disease Prevention of Dutch elm disease Transmission of Dutch elm disease Traditional Treatments Symptoms of Dutch elm disease Innovative Treatment Thank you for visiting elmcare.com
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Home > Elm Tree Diseases > Dutch Elm Disease > History Last Update 30/08/00 Why “Dutch” elm disease? The Dutch may have been unfairly blamed for the loss of millions of trees. “Dutch” elm disease got its name How Trees Work because Dutch scientists identified it when the About Elm Trees disease made an appearance in Holland in 1917. From there, it spread quickly wiping out many of the Caring for Your Elm European elms.
Elm Tree Diseases
Dutch Elm Disease History of DED Transmission Symptoms Prevention Origins Treatments Scientists believe that the fungus that causes DED originally came from the New Research Himalayas. It travelled to Europe from the Dutch East Indies in the late 1800’s. In the 1930’s, the disease spread to North America on wooden crates made with Elm Leaf Beetle infected elm wood. Verticillium Wilt Elm Yellows A second introduction of the disease in North America occurred in 1945 starting in Cankers Sorel, Quebec. It destroyed over half the remaining elm trees in eastern Canada Wetwood and the US. By 1976, only 34 million elm trees were left. Elm Leaf Black Spot Elm Leaf Miner New strains of the disease appeared in the 1960’s in England. Within 20 years, 17 Asian Longhorned Beetle million of the country’s 23 million elm trees were dead.
Elm Tree Links Moving West Quick Elm Facts The disease has now spread to Manitoba and Saskatchewan where there are approximately 500,000 elm trees in the cities. Three to five percent of the elms die each year
Winnipeg is spending C$2.5 million a year on sanitation and pruning. Having lost 40,000 trees in the last 20 years, the city’s elm population is now just 200,000.
More Than Just Beauty Mature trees add to property values. The estimated value of a mature elm for insurance purposes is C$3,600 (US$2,500) per tree. With roughly 650,000 elms in cities in Canada, the elms are worth C$2.3 billion. The 7 million urban trees in the US are worth US$17.5 billion.
Source: "The American elm and Dutch elm disease" M. Hubbes, Forestry Chronicle, March/April 1999. Vol. 75, No. 2, p.265
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Home > Elm Tree Diseases > Dutch Elm Disease > Transmission Last Update 07/12/00
Dutch elm disease can be transmitted from tree to tree by the elm bark beetle, root How Trees Work grafts and infected tools. About Elm Trees Caring for Your Elm
Elm Tree Diseases Elm Bark Beetle Dutch Elm Disease History of DED The elm bark beetle (not to be Transmission confused with the Elm Leaf Symptoms Beetle) is by far the most Prevention important factor in Dutch Elm Treatments Disease. New Research
Elm Leaf Beetle These tiny insects’ lives revolve Verticillium Wilt around elm trees. The female Elm Yellows beetle tunnels into the tree Cankers between the bark and the wood Wetwood and lays its eggs. When the eggs Elm Leaf Black Spot hatch, the larvae tunnel further into the tree in order to feed before emerging as Elm Leaf Miner mature beetles. Asian Longhorned Beetle Adults feed in the crown of the tree, moving from tree to tree before breeding Elm Tree Links again. Quick Elm Facts If a beetle breeds or feeds in a DED-infected tree, the sticky spores of the fungus become attached to its back. When the beetle moves to a healthy tree, so too do the spores.
There are two species of the elm bark beetle in North America – the European and the Native elm bark beetles. The European is more temperature sensitive and lives mainly in southern regions. The Native is dominant in the mid-west.
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Brood Gallery of Native Bark Beetle Brood Gallery of European Bark Beetle
The native elm bark beetle consists of two separate breeding groups. One group overwinters as larvae in the breeding tunnels, while the second group overwinters as adults. These adults emerge from mid-April to mid-May. It is their feeding phase that causes the majority of DED infections. It is believed that the European elm bark beetle overwinters as larvae.
Much of the effort to control the spread of DED has focused on controlling the beetle population with insecticides or trapping. These methods have enjoyed some degree of success but the beetles remain the single most important factor in the spread of the disease.
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Root Grafts
Mature elms have a large system of roots. When these roots come into contact with those of another elm, they can graft together to promote the exchange of nutrients. The fungus can spread through the root grafts, infecting the neighbouring trees.
A tree infected by root graft transmission shows very sudden and devastating symptoms. Treatment is much less effective.
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Infected Tools
Pruning tools can also transmit Dutch elm disease. All tools should be cleaned http://www.elmcare.com/disease/dutchelm/transmission.htm (2 of 3) [2/27/02 10:30:44 PM] Transmission of Dutch Elm Disease
before pruning a healthy tree. Some arborists recommend a 10% solution of household bleach.
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Home > Elm Tree Diseases > Dutch Elm Disease > Symptoms Last Update 30/08/00 An infected elm tree usually exhibits symptoms soon after infection. Because of the speed with which the disease attacks, detecting symptoms as early as possible is essential for treatment. How Trees Work About Elm Trees Caring for Your Elm The first sign of the disease is the sudden Elm Tree Diseases wilting of leaves in the upper reaches of the tree Dutch Elm Disease History Transmission Symptoms Prevention Treatments New Research Next, the leaves change colour from green Elm Leaf Beetle to yellow to brown. They then shrivel and Verticillium Wilt die. Elm Yellows Cankers Wetwood Elm Leaf Black Spot Elm Leaf Miner Asian Longhorned Beetle
Elm Tree Links Timing Quick Elm Facts If the infection occurs very late in the season, the leaves will appear to fall normally. However, the following spring the new leaves will be smaller than normal. The tree will often die before mid-summer.
In late summer, it may be difficult to distinguish between wilting and natural fall colours.
Bark Signs
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Discolouration of the wood is also a sign of the disease. If you peel back the bark on a wilted branch, you will see some streaking on the wood.
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http://www.elmcare.com/disease/dutchelm/symptoms_of_dutch_elm_disease.htm (2 of 2) [2/27/02 10:30:46 PM] Prevention of Dutch Elm Disease
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Home > Elm Tree Diseases > Dutch Elm Disease > Prevention Last Update 30/08/00 Integrated Sanitation Program
Traditionally, people have tried to control Dutch Elm Disease by stopping it from How Trees Work spreading. Many communities, like the City of Winnipeg, have adopted a highly co- About Elm Trees ordinated program to try to save their elms. Caring for Your Elm
Elm Tree Diseases
Dutch Elm Disease Surveillance History Detection is the first step. The earlier the disease can be caught, the quicker it can Transmission Symptoms be stopped. Prevention Some communities and government agencies have designated experts to help Treatments make a definitive diagnosis. Contact these experts at the first suspicion of DED. New Research Early detection can help prevent infection of nearby trees.
Elm Leaf Beetle Verticillium Wilt Elm Yellows Cankers Wetwood Disposal Elm Leaf Black Spot Dead wood is an ideal breeding ground for the elm bark beetle. Dead wood must Elm Leaf Miner be properly removed and destroyed. Asian Longhorned Beetle Firewood spreads the disease. Storing elm firewood is illegal in many jurisdictions with active DED control programs. Elm Tree Links Quick Elm Facts All elm wood should be buried, burned or chipped immediately.
Pruning Pruning promotes tree health. Regular pruning helps a tree use its natural defenses against DED. It also removes breeding sites for the elm bark beetle. Click here for proper maintenance pruning techniques.
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An elm in downtown Toronto is pruned in winter to discourage further spread of DED When you prune is as important as how you prune. Pruning creates open cuts in a tree’s bark that take time to heal. Since the elm bark beetle is attracted to these wounds, pruning should not take place from early April to late July when the beetle is active.
Some municipalities have by-laws stating when pruning can be legally done.
Insecticides Chemical insecticides are used to control the elm bark beetle.
Chemicals are sprayed on the crown, bark and base of the tree in early April when the beetles become active. The chemicals kill the emerging adult beetles before they can introduce the fungus by feeding on the tree. Insecticides include Methoxychlor, carbaryl (Sevin) and chlorpyrifos (Dursban).
Some cities spray all boulevard and park elms. They may also offer their services to individual homeowners.
Before using any chemicals, consult a professional arborist. Most insecticides can be harmful to people, pets and the environment.
Insecticides are used less than they were in the past because proper dead wood disposal is more effective.
Fungicides Fungicides can help guard against Dutch elm disease.
Chemicals such as Arbotect 20-s, Alamo, and Lignasan, are injected into the tree through holes drilled in the base or in the root-flares.
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Fungicide injection is both a preventative measure and a treatment for infected elms. However, fungicide injections are best left to professional arborists. Preventative injections can actually have an adverse affect on a tree’s health making it more susceptible to DED infection.
Fungicide injection should never be used as a substitute for pruning and other measures.
Natural Resistance A team from the University of Toronto has recently developed an innovative approach to preventing Dutch elm disease.
An “elicitor” inserted into the tree stimulates the tree’s natural defense mechanism which in turn prevents the fungus from gaining a foothold in the tree’s vascular system.
For long term protection, the elicitor must be applied on an annual basis. Along with regular pruning, it is an extremely effective method to prevent DED. It is also completely safe because it uses the tree’s natural defenses.
For more information about the elicitor, click here.
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Home > Elm Tree Diseases > Dutch Elm Disease > Traditional Treatments Last Update 30/08/00
Pruning How Trees Work Pruning is an extremely effective way to treat a tree infected with DED. About Elm Trees Caring for Your Elm Timely removal of diseased wood checks the spread of the disease. It is however less effective for well-established infections or for root-graft infections. Elm Tree Diseases When you prune is extremely important. Pruning opens fresh wounds in the tree that take time to heal. The elm bark beetles are attracted to these wounds. Dutch Elm Disease History Pruning should not take place while the beetles are active (from early April to late Transmission Symptoms July). Some municipalities have by-laws defining when you are legally permitted Prevention to prune elm trees. Treatments New Research Technique
Elm Leaf Beetle ● Verticillium Wilt On an infected tree, locate the wilted branch and remove the bark until Elm Yellows sapwood can be found with no discoloration. ● Cankers Cut the branch approximately 10 feet below the discolored area. The Wetwood farther below the discolored area the limb is cut, the greater the chance of Elm Leaf Black Spot freeing the elm of the disease. Elm Leaf Miner ● Properly dispose of dead wood. ● Asian Longhorned Beetle Disinfect tools using a 10% household bleach solution.
The loss of a major limb is regrettable but it can prevent the loss of the tree. One Elm Tree Links study reported that 60% of the trees that had been pruned at the early signs of the Quick Elm Facts disease survived.
If the symptoms are allowed to continue, however, the success rate plummets. Studies have shown that if less than 5% of a tree is infected, pruning successful stops the disease 65% of the time. If 20% of the tree is infected, the success rate drops to 0%. 1
Chemical Fungicides Treating elm trees with systemic fungicides is a popular way to combat the effects of Dutch elm disease. Chemicals are injected into the tree either through holes drilled in the base of the tree or in the root-flares. Some chemicals that are currently used include Arbotect 20-s, Alamo and Lignasan.
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Chemical fungicides can be effective for trees in the early stages of the disease. If, however, a tree has advanced DED or has contracted the disease through a root graft, fungicides have little or no effect.
Fungicides are not a substitute for pruning and other measures.
Due to the difficulty of the procedure, fungicide injections are best left to professional arborists. A preventative injection into a healthy tree can adversely affect its health making it more susceptible to a DED infection.
1 (Himlick and Ceplecha, 1976)
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Home > Elm Tree Diseases > Dutch Elm Disease > Innovative New Treatment Last Update 30/08/00 Jump ahead to:
Unique Discovery How It Is Applied How Trees Work How It Works About Elm Trees Using ELMguard Caring for Your Elm
Elm Tree Diseases
Dutch Elm Disease History Transmission Symptoms
Prevention Treatments The elicitor in pellet form being inserted into a young elm. New Research Over the past twenty years, a team of scientists from the University of Toronto, Elm Leaf Beetle Faculty of Forestry, under the leadership of Dr. Martin Hubbes, has been working Verticillium Wilt on an exciting, new all-natural treatment for the prevention of Dutch elm disease. Elm Yellows The new treatment or "elicitor" does not work directly on the fungus causing Dutch Cankers elm disease. Instead, it stimulates the tree's own immune system. The treatment Wetwood has a strong protective effect because it activates the tree's natural defense Elm Leaf Black Spot response to Dutch elm disease. Elm Leaf Miner Asian Longhorned Beetle
Elm Tree Links Quick Elm Facts
Unique Discovery
The treatment is based on a special natural protein which was discovered by the University of Toronto scientific team as a result of intensive advanced molecular biology research. The protein elicits a defensive response in the tree which enables it to resist the onset of the aggressive and deadly strain of Dutch elm disease. The treatment is unique because it is all natural - it contains no synthetic chemicals and is non-toxic.
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How It Is Applied
ELMguard is an annual treatment applied to the tree in the spring. It is injected directly into the tree in either a liquid or pellet form through small holes drilled in the tree's outer growth ring. After injecting ELMguard, a wax sealer is used to close the small holes. During the season, the tree then closes the hole naturally with new wood growth.
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How It Works
After the injection, the tree's vascular system absorbs the protein starting a series of defensive reactions.
These reactions include the production of mansonones and cell lignification (hardening). Mansonones are a naturally produced substance and play an important role in an elm tree's defense response against Dutch elm and other diseases.
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Using ELMguard
ELMguard should be used as part of a comprehensive elm care program which promotes good health, proper sanitation (pruning) and the use of the elicitor to boost the tree's immune response system.
ELMguard does not provide 100% protection against Dutch elm disease in all elm trees because of the simple fact that each elm is different. Just as each of us is genetically different from everyone else, the same is true for wild elms. Therefore, each tree will react slightly differently to the treatment. Also, general health of an individual tree is a major factor in determining ELMguard's effectiveness.
For further information on ELMguard and other natural treatments for the control and prevention of Dutch elm disease, visit www.elmguard.com.
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Home > Elm Tree Diseases > Elm Leaf Beetle Last Update 30/08/00 The elm leaf beetle is a pest which poses some danger to the elm tree.
Adult beetles are approximately ¼ inch How Trees Work long. Their colour fades from yellow to olive About Elm Trees as they mature. They have black stripes on the wing covers and four black spots on the Caring for Your Elm thorax. The larvae are about 1/2 inch long and a dull yellow colour. Elm Tree Diseases The adults lay eggs on Dutch Elm Disease Elm Leaf Beetle the underside of elm Verticillium Wilt leaves in late May and early June. After they hatch, the larvae Elm Yellows begin feeding on the flesh of the leaf, leaving only the veins Cankers intact. About three weeks later, the adults emerge and chew Wetwood small holes in the leaves. Elm Leaf Black Spot Elm Leaf Miner A tree can survive an infestation of elm leaf beetles. However, its weakened state will make it more susceptible to other diseases such as Dutch elm disease. Asian Longhorned Beetle Birds, toads and other insects are natural enemies of the elm leaf beetle. There Elm Tree Links are also a number of effective pesticides. Quick Elm Facts As many chemical pesticides can be poisonous, care should be taken to read the label before use.
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Home > Elm Tree Diseases > Verticillium Wilt Last Update 30/08/00 Verticillium wilt is caused by a fungus that lives in the soil. The fungus penetrates the root system of susceptible plants, eventually blocking the plant’s water- conducting system. How Trees Work About Elm Trees The fungus affects more than 300 types of plants throughout the world - from raspberries and tomatoes, to maples and elms. Although the disease occurs in Caring for Your Elm naturally forested areas, it is found mostly in landscape plantings.
Elm Tree Diseases Dutch Elm Disease Elm Leaf Beetle Verticillium Wilt How It Spreads Elm Yellows Cankers The two fungal species, V. alboatrum and V. dahliae, can survive in the soil for Wetwood decades lying in wait for new plants to move in. The fungus usually enters the Elm Leaf Black Spot roots through wounds, but if the tree is weak, it can actually penetrate the root. Elm Leaf Miner Asian Longhorned Beetle When a plant dies, the fungus enters a resting state, producing structures called “microsclerotia”. These structures can be easily transported from place to place when trees are transplanted. In dry conditions, these microsclerotia can by carried Elm Tree Links by the wind to infect new areas. Quick Elm Facts Tools can also carry the fungus, so proper sanitation procedures should be followed.
How the Fungus Kills
Once inside the root, the fungus reproduces and spreads through the tree via the xylem, or water-conducting tissue. As it spreads, it causes tissue damage and clogs the xylem, preventing water from reaching the outer branches. Without moisture and necessary nutrients, these outer limbs wilt and die.
Symptoms
The first sign of disease is a slight yellowing of the foliage (similar to symptoms of
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Dutch elm disease although with less extensive crown involvement). There is also discolouration of the wood. Branches, stems and roots show a light to dark brown staining of the sapwood. Cankers may form on the branch and stem.
Trees with extensive infection show reduced growth rates and branch dieback. Younger trees usually succumb within one year. Older trees tend to deteriorate for a few years before finally dying.
Control
Fertilizing
Fertilizing with a balanced mixture light on nitrogen (5-10-10) may help to alleviate some of the symptoms. High nitrogen fertilizers, however, should be avoided. They promote new growth that would be vulnerable to the fungus.
Natural Defenses
One area that does offer hope comes from the Forestry Department of the University of Toronto. A team led by Dr. Martin Hubbes has isolated a glycoprotein that can potentially boost the natural defenses of a tree. Although research so far has focused on Dutch elm disease, stimulation of natural defenses could also be effective with Verticillium wilt.
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Home > Elm Tree Diseases > Elm Yellows Last Update 30/08/00 Also known as Elm Phloem Necrosis, this disease infects trees native to North America, while European and Asian elms How Trees Work seem to be immune. About Elm Trees Caring for Your Elm The first symptom is the death of root hairs and tips followed by foliar wilt. Leaves will turn yellow, then brown and curl up. Elm Tree Diseases Generally the tree dies a few weeks after Dutch Elm Disease foliar symptoms manifest themselves. Elm Leaf Beetle Other symptoms include yellowing of the sapwood and a wintergreen odour Verticillium Wilt emanating form the bark. The causal agent of elm yellows is a “mycoplasma-like Elm Yellows organism” (MLO) which is classified between a virus and a bacterium. This Cankers organism is carried from tree to tree by leafhoppers. There is no known effective Wetwood treatment for elm yellows, so disposal of infected trees is the only option. The Elm Leaf Black Spot most effective preventative measure is controlling the leafhopper population. Elm Leaf Miner Asian Longhorned Beetle In order to do this, a homeowner can utilize a pesticide such as methoxychlor emulsifiable concentrate. Applied during the bud breaks, this chemical represents Elm Tree Links an effective control of the leafhopper. As most chemical pesticides are poisonous, Quick Elm Facts care should be taken to read the label before use.
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Home > Elm Tree Diseases > Cankers Last Update 30/08/00 Cankers are a fungal disease. The leaves turn bright yellow (similar to the How Trees Work symptoms of Dutch elm disease) with reddish-brown to black cankers on the twigs About Elm Trees and small branches. The infected leaves Caring for Your Elm can stay on the tree for several weeks.
There is no chemical treatment. Pruning is Elm Tree Diseases the best way to manage this disease. Dutch Elm Disease Elm Leaf Beetle Verticillium Wilt Elm Yellows Cankers Wetwood Elm Leaf Black Spot Elm Leaf Miner Asian Longhorned Beetle
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Home > Elm Tree Diseases > Wetwood Last Update 30/08/00 Wetwood is caused by a bacterial infection and is very common in elms and many other species. The infection causes moisture to be retained in the wood and also How Trees Work produces metabolic gases that increase the internal About Elm Trees pressures in the tree. Periodically the liquid will be forced out Caring for Your Elm of the tree through wound sites. The liquid oozes out and down the tree, where other organisms colonize it. This liquid is called slime flux and is known to have a foul odour. Elm Tree Diseases
Dutch Elm Disease Elm Leaf Beetle Wetwood becomes a problem only when enough infection Verticillium Wilt sites occur on the tree to compromise its structural integrity. A Elm Yellows professional or consulting arborist should judge this. Cankers Otherwise, wetwood can be viewed as somewhat beneficial, Wetwood as the moist environment that it creates in the tree helps to Elm Leaf Black Spot prevent decay fungi from colonizing the tree. Symptoms Elm Leaf Miner appear as long discoloured streaks on the trunk. Leaves may Asian Longhorned Beetle also exhibit some scorch if the infection is extensive.
Elm Tree Links At present, there is no treatment for wetwood. Quick Elm Facts
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Home > Elm Tree Diseases > Elm Leaf Black Spot Last Update 30/08/00 Elm Leaf Black Spot, also called elm anthracnose, is another fungal disease affecting the leaves of an elm tree. How Trees Work About Elm Trees First, yellow spots appear on the topside of the leaves. These spots are Caring for Your Elm followed by slightly raised black fruiting bodies. Elm Tree Diseases Removing diseased leaves can aid in Dutch Elm Disease treatment. Elm Leaf Beetle Verticillium Wilt Nurseries use chemicals such as Elm Yellows Bordeaux and mancozeb but these are Cankers not recommended for home use. Wetwood Elm Leaf Black Spot Elm Leaf Miner Asian Longhorned Beetle
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Home > Elm Tree Diseases > Elm Leaf Miner Last Update 30/08/00 The elm leaf miner is a common pest throughout eastern North America.
This insect feeds inside the leaf. The larvae tunnel through the leaf forming How Trees Work blotches and discolouration. As the miners move to the outer edge of the leaf, the About Elm Trees leaf turns brown. The larvae finish feeding in late June or early July and then fall to the ground where they pupate. Caring for Your Elm Whitish with pale brown heads, the elf leaf miner larvae measure about 6mm in Elm Tree Diseases length. They overwinter in the soil and produces a brown papery cocoon. In the spring, they emerges as an adult sawfly. Dutch Elm Disease Elm Leaf Beetle Pesticides can control the spread of the elm leaf miner. Injected into the trunk after Verticillium Wilt the leaves are fully formed, the pesticide will repel the larvae for about 2 months. Elm Yellows As many chemical pesticides can be poisonous, care should be taken to read the Cankers label before use. Wetwood Elm Leaf Black Spot Natural predators can also help. Ground beetles, braconid wasps and Elm Leaf Miner Asian Longhorned Beetle ichneumonids all prey on the leaf miner during various stages of development. To attract these predators, introduce plant species such as evening primrose, evergreen eunymous, baltic, boston or english ivy, fennel or rue. Elm Tree Links Quick Elm Facts
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Home > Elm Tree Diseases > Asian Longhorned Beetle Last Update 30/08/00
See also www.asian-longhorned-beetle.com. How Trees Work About Elm Trees A wood-chewing insect from China is the newest threat to North America's elms. Caring for Your Elm
Slightly larger than a cockroach, the Asian longhorned beetle chews its way into Elm Tree Diseases the trunks of the trees where it lays its eggs. Eventually, the tree dies.
Dutch Elm Disease Although elms will be affected, the primary target of this insect are maples. Loss Elm Leaf Beetle of maple trees could have a considerable impact on the maple syrup industry. Verticillium Wilt Elm Yellows Carried over from China in wooden skids, the beetle has made its presence felt in Cankers Chicago. Officials have begun extensive efforts to control further spread. Wetwood Elm Leaf Black Spot Elm Leaf Miner Source: Globe and Mail August 18, 1999 Asian Longhorned Beetle
Elm Tree Links Quick Elm Facts
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Home > Elm Tree Links
Last Update 30/01/01 Canada United States How Trees Work International About Elm Trees Other Information Links Elms in the Media Caring for Your Elm Elm Tree Diseases
Canada Manitoba Elm Tree Links
● Winnipeg's Coalition to Save the Elms Quick Elm Facts ● Manitoba Natural Resources Forest Landscape Management, Forestry Branch
Nova Scotia
● Nova Scotia Provincial Regulation Registry ● Halifax Regional Municipality, City of Dartmouth Bylaw
Ontario
● Ontario Shade Tree Council
Saskatchewan
● Saskatchewan Environment and Resource Management ● CETAC-WEST ● College of Agriculture, University of Saskatchewan
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United States National
● Department of the Interior, National Parks Service, Integrated Pest Management Dutch Elm Disease Manual
Colorado
● Colorado State University Cooperative Extension Plant Talk
Illinois
● Morton Arboretum in Chicago "A Brief History of Dutch Elm Disease" ● Des Plaines City Services
Iowa
● Iowa State University Horticulture and Home Pest News
Kansas
● Kansas State University Research and Extension
Kentucky
● Kentucky State University Extension Service
Michigan
● Michigan State University Extension Service
Minnesota
● University of Minnesota Center for Urban Ecology and Sustainability
Missouri
● University of Missouri-Columbia Extension
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Montana
● Montana State University Extension Service
North Dakota
● North Dakota State University Extension Service
Washington
● Washington State University Cooperative Extension, Western Washington
International International Links coming soon
Other Information ● Elms Return to Elm Street Links
Elms in the Media ● Smithsonian Magazine "Racing to Revive our Embattled Elms", June 1998.
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Also, if you live in an area not listed above, we can do some research for you to see if we can find some helpful resources.
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Home > Quick Facts Last Update 17/12/01
● Trees add not only beauty but value to our property. The value of a mature elm for insurance purposes is How Trees Work US$2,500 (C$3,600). About Elm Trees Caring for Your Elm ● The 7,700,000 elm trees in urban centres in North Elm Tree Diseases America have a combined value of over US$19 billion Elm Tree Links ● Dutch elm disease got its name because it was discovered by scientists Quick Elm Facts in Holland in 1917.
● The seven Dutch scientists who first identified Dutch elm disease were all women.
● Dutch elm disease hit England in the 1960’s and within 20 years had killed 17 million of the country’s 23 million elm trees.
● A second out-break of Dutch elm disease in 1945, destroyed second- generation elms in Eastern Canada and the United States. The elm population dropped from 77 million to 34 million by 1976.
● Fully mature elm trees can live as long as 300 years.
● The cooling effect of one urban elm tree is equivalent to five air conditioning units.
● North American settlers named the elm “the lady of the forest”.
● Elm trees first appeared in the Miocene period, about 40 million years ago.
● The American Elm grows to over 115 feet tall and can have a diameter in excess of ten feet.
● The Iroquois used elm bark to make canoes, rope and utensils
● The film “Nightmare on Elm Street” has absolutely nothing to do with elm trees
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Home > Site Map About This Site Caring for your Elm Quick Elm Facts Fertilizing How Trees Work Pruning
Important Facts Why Prune? Types of Trees Types of Pruning How Trees Breathe Proper Technique How Trees Drink Timing of Pruning Structures of Trees Pruning Pitfalls
Leaves Lawn Care Roots Obstacles to Growth Bark Disposal of Dead Elms
About Elms Elms Tree Diseases
Identifying Elms Dutch elm disease
Silhouette History of DED Leaves Symptoms of DED Bark Transmission of DED Preventing DED Treatments Elm Species New Research The Elm Story
Asian Longhorned beetle Elms and Humans Cankers Elms in History Elm Leaf Beetle Elms in Literature Elm Leaf Black Spot Elms in Mythology Elm Leaf Miner Elm Yellows Biology of Elms Verticillium Wilt Wetwood
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Home > About This Site Last Update 17/12/01 This site is designed to be a comprehensive resource for homeowners, researchers and tree care professionals to find information about about elm trees. Dutch elm disease
About Elmcare How Trees Work ● Quick Facts About Elm Trees ● How to Care for Your Tree Caring for Your Elm ● The Elmcare Newsletter - Sign up on the Homepage! Elm Tree Diseases Elm Tree Links ● Dutch Elm Disease Quick Elm Facts ● The Elm's Place In History
● Links to elm tree resources
....and much more!
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Home > Copyright Last Update 17/12/01 This site is copyrighted by ArborScience. While we would be happy to share any of our information, we do require a written request. How Trees Work About Elm Trees Please note that while we have taken every effort to make sure that this site contains accurate information, we cannot be held responsible for any damages or Caring for Your Elm problems arising from the use of the information that we have supplied. Elm Tree Diseases Elm Tree Links CONTACT Quick Elm Facts ArborScience Inc. 270 Yorkland Blvd. Suite 160 Toronto, ON M2J 5C9
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http://www.elmcare.com/copyright.htm [2/27/02 10:31:18 PM] Why Prune?
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Home > Caring for your Elm > Pruning > Why Prune? Last Update 30/08/00
How Trees Work Safety First About Elm Trees Dead or dying branches can fall causing injury or property damage. Overgrown branches can obstruct lines of sight in vital areas such as intersections or driveways. Trees can come into contact with overhead power lines. Pruning Caring for Your removes safety hazards. Elm Tree Better yet, by careful planting, you can avoid many of the potential hazards in the Fertilizing first place. Pruning Lawn Care Watering Obstacles Disposal Maintenance Pruning Elm Tree Diseases Trees shed weak branches to promote growth in healthier areas. You can help this process. Remove branches that are in competition for sunlight or that are rubbing Elm Tree Links against other. Quick Elm Facts
DED Preventative Pruning When an elm is under attack from the Dutch elm disease fungus, timely pruning of infected branches can check the spread of the disease.
Pruning should not take place from early April to late July when the beetle is active. After the limbs are removed they should be burned or buried.
For more information on DED preventative pruning, click here.
Types of Pruning
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Home > Caring for your Elm > Pruning > Types of Pruning Last Update 30/08/00
Crown-thinning How Trees Work With this type of pruning, dead or dying branches are removed from the crown in About Elm Trees order to allow better air movement and light penetration to the tree.
Caring for Your Crown-raising Elm Tree This type of pruning is performed to provide clearance. Most municipalities have Fertilizing bylaws specifying minimum branch height beside roads and sidewalks. The lower Pruning branches are removed effectively raising the crown of the tree. Lawn Care Watering Obstacles Crown-reduction Disposal When a tree has outgrown the available space, crown-reduction pruning is often necessary. Upper limbs are pruned to either reduce the height or width of the Elm Tree Diseases crown. Elm Tree Links Quick Elm Facts Proper Pruning Techniques
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http://www.elmcare.com/caring/pruning/types.htm [2/27/02 10:31:21 PM] Pruning Technique
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Home > Caring for your Elm > Pruning > Technique Last Update 30/08/00 Adopting proper pruning techniques is vital for the health of the tree. Cuts should be made at the point where two branches meet (known as a node). Cuts made in How Trees Work the middle of a branch (internodal cuts) can result in unhealthy regrowth and slow About Elm Trees wound closure.
Caring for Your Elm Tree
Fertilizing Where To Make Your Cut Pruning The area where the branch meets a major limb is characterized by two features – Lawn Care the branch collar and the branch bark ridge. The branch collar is underneath the Watering branch, while the branch bark ridge is above it. This is the point where branches Obstacles would naturally be lost. When pruning a branch, it is important to make a cut as Disposal close as possible to these features without actually cutting them. Cutting into the branch collar will promote decay in the main stem as it takes longer for the tree to Elm Tree Diseases close such a wound. Elm Tree Links Quick Elm Facts
Larger Limbs For larger limbs, special care is required to prevent damage to the tree. If a cut is made from the branch ridge directly through to the branch collar, often the limbs weight will cause it to rip away from the stem leading to a large slow-closing wound. Therefore, first a small undercut should be performed a small distance (maybe 5cm) away from the collar. Then, a clean topcut can be made on the outside of the undercut (away from the stem). Finally, a clean cut can be made just outside the branch collar.
Timing
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Home > Caring for your Elm > Pruning > Timing Last Update 30/08/00
How Trees Work About Elm Trees When Unlike many other tree species, pruning must be done at a very specific time of Caring for Your year. Because open wounds attract the elm bark beetle (the major vector for Dutch elm disease), pruning should never be performed from about mid-April to late- Elm Tree July. In fact, some communities have bylaws to this effect. Also, due to presence Fertilizing of a variety of fungal spores in the fall, if possible, pruning should be avoided. This Pruning leaves early spring as an ideal pruning season. With the growing season to follow, Lawn Care the tree has ample time to close the wound and regain its vitality. Watering Obstacles Disposal
Elm Tree Diseases Elm Tree Links Quick Elm Facts How Often Mature deciduous ornamental trees such as elms should be thoroughly pruned once every three years with annual minor pruning. In areas where Dutch elm disease is present, more vigilance is required to allow timely removal of dead or dying branches. If a tree is noticeably slow to bounce back from a pruning session, less frequent pruning may be in order.
Pruning Pitfalls
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Home > Caring for your Elm > Pruning > Pruning Pitfalls Last Update 30/08/00
How Trees Work Topping About Elm Trees
This practice is extremely harmful to trees. Firstly, it involves the sudden removal Caring for Your of a large proportion of the tree’s foliage which temporarily starves the tree of Elm Tree needed energy. To compensate for the loss, the tree will promote the growth of new buds, usually from just below the stub. Homeowners may feel that this new Fertilizing growth represents healthy regrowth, but this is not the case. The new buds are Pruning structurally weak and superficially anchored to the larger branch. Although very Lawn Care quick to grow, they can easily break in windy conditions. Thus, the original Watering purpose of topping (pruning potentially hazardous limbs or controlling upward Obstacles growth) is defeated. Disposal Secondly, bark that is suddenly exposed to large amounts of sunlight and heat can Elm Tree Diseases become scalded. This can lead to damage and often death of the limb. This again Elm Tree Links creates a potential hazard. Quick Elm Facts Thirdly, topping wounds close slowly and sometimes not at all. Insects and pathogens can therefore gain access to the tree for extended periods of time. This is a major concern if Dutch elm disease has been spotted in the region.
Finally, topped trees are unattractive and can often contribute to a lowering of property values.
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http://www.elmcare.com/caring/pruning/pitfalls.htm [2/27/02 10:31:26 PM] Leaves
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Home > How Trees Work > Structure of a Tree > Leaves Last Update 30/08/00 Leaves perform two vital functions for trees. They produce sugars by photosynthesis and they allow for the distribution of water through transpiration.
How Trees Work Photosynthesis is a process by which CO2 and water are combined with sunlight and a pigment called chlorophyll. The chemical reactions result in the production Types of Trees of sugars which provide energy to the tree. The leaves use some of this energy, Important Facts but the majority is transported, in the form of sugar solutions, to other parts of the Structure of a Tree How Trees Breathe tree that require it. How Trees Drink Transpiration, or water loss, also takes place in the leaves. As this occurs, water is drawn up from the roots through the vascular system to replace lost moisture. About Elm Trees Caring for Your Elm Elm Tree Diseases Elm Tree Links Roots Quick Elm Facts Bark
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http://www.elmcare.com/trees/structures/leaves.htm [2/27/02 10:31:28 PM] Roots
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Home > How Trees Work > Structure of a Tree > Roots Last Update 30/08/00 Jump ahead to: Root Structure Root Growth
Roots are organs that provide structural stability for trees. Roots also absorb water and minerals. How Trees Work
Types of Trees Important Facts Root Structure Structure of a Tree How Trees Breathe Roots are made up of a number of specialized components. The root hairs, tiny How Trees Drink structures extending from the main root stems, have very thin walls which absorb water and minerals. This mineral solution is passed into the vascular core of the About Elm Trees root from where it is transported throughout the tree. At the tip of the root, there Caring for Your Elm exists a protective structure called the root cap. These loose cells are shed as the root grows into the soil. Elm Tree Diseases Elm Tree Links Different trees have slightly different root systems. Some trees, such as the pine, Quick Elm Facts have a strong central root called the taproot. This is usually larger than any other roots and often extends deep into the ground. Because substantial damage to this root can be fatal to the tree, trees with taproots are generally difficult to transplant.
Other trees, such as the elm or maple, do not have a dominant taproot. Their root systems are characterized by a large number of roots often closer to the surface.
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Root Growth
Generally, root growth is influenced by moisture and gravity. In other words, unless there are substantial amounts of moisture near the surface, roots tend to grow downwards through the soil.
Roots are always growing and, like a tree's trunk, they grow both longer and wider. At the tip of the roots, the growing region is called the meristem. This is where most of the lengthwise growth takes place. In addition to this, wood is added to the inside of the root and phloem is added towards the outside.
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Source: MS Encarta online encyclopedia
Leaves Bark
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Home > How Trees Work > Structure of a Tree > Bark
Last Update 30/08/00 Bark is the outer protective covering of tree trunks. The form and structure of bark can differ greatly from tree to tree. As a result, it is a useful characteristic for tree identification. About Elmcare.com Bark is made up of two layers - outer bark and inner bark. How Trees Work The outer bark is made up of dead cells. This layer is usually quite thick, but in Types of Trees certain trees (young birch, for example) it is very thin. Important Facts Structure of a Tree How Trees Breathe The inner bark, known as the phloem is made up of a thin layer of living cells. These cells have extremely thin walls allowing water and nutrients (in the How Trees Drink form of sugar solutions) to pass easily throughout the tree. Somewhat akin to human skin, old bark is shed, and new bark is formed from the inside. About Elm Trees Caring for Your Elm Elm Tree Diseases The Elm Community Leaves Roots
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http://www.elmcare.com/trees/structures/bark.htm [2/27/02 10:31:31 PM] Ask the Experts
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Home > Ask the Experts Last Update 30/08/00 Due to the overwhelming response we have been receiving, we are temporarily suspending the Ask the Experts section of elmcare.com. Our experts are currently in the field conducting trials for ELMguard and are unable How Trees Work to keep up with the number of questions we are receiving. About Elm Trees Caring for Your Elm Please check back frequently or enter your e-mail address below to be Elm Tree Diseases informed when the Ask the Experts section is reopened. Elm Tree Links Quick Elm Facts
Perhaps your question has already been answered. Check the categories below for past questions and answers.
Fertilizing (4) Watering Insects (1) Elms in general (5) Dutch elm disease (5) Pruning (2) Other diseases (2) Elm Wood (2) new!
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http://www.elmcare.com/experts/experts.htm [2/27/02 10:31:33 PM] Ask the Experts - Fertilizing
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Last Update 30/08/00 Should I be using fertilizer for my tree?
Will my lawn fertilizer help my elm tree? About Elmcare.com How Trees Work When should I fertilize my elm? About Elm Trees What formulation would you recommend for an elm tree? Caring for Your Elm
Elm Tree Diseases The Elm Community Question Should I be using fertilizing for my tree?
Answer Fertilizing is an integral part of a comprehensive elm care program. Elms trees that live in a city lack some of the nutrients it needs to truly do well. Ask the Experts!
Quick Elm Facts Question Will my lawn fertilizer help my elm tree? ELMguard Trials Answer Probably not. Lawn fertilizer has several characteristics which make it undesirable for elms. First, it's generally in a granular formulation. For trees, you want a fertilizer you can put into the ground. Secondly, the formulations often include chemicals to kill weeds. This can be harmful for the tree. Thirdly, grass competes with a tree for available nutrients. Because of this, nutrients will be absorbed by the grass before they can penetrate the soil to the tree's roots. You should use a fertilizer specially formulated for trees.
Question When should I fertilize my elm?
Answer Fertilization should be done in the spring or the fall. Fall is very good because there is a lot of moisture in the ground and the roots are very active.
Question What formulation would you recommend for an elm tree?
http://www.elmcare.com/experts/fert.htm (1 of 2) [2/27/02 10:31:35 PM] Ask the Experts - Fertilizing
Answer A 5-10-10 or 6-12-12 fertilizer would be ideal for an elm. The first number is the proportion of Nitrogen. You don't want as much Nitrogen because that is the mineral that promotes new growth. If you have too much new growth, the tree can't focus as much on other important tasks such as building up its defense mechanism.
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Last Update 30/08/00
How should I water my elm tree? About Elmcare.com How Trees Work About Elm Trees Question How should I water my elm tree? Caring for Your Elm Elm Tree Diseases Answer When you are watering your tree, you want to get the moisture below The Elm Community the turf line (below the grass roots). Because of this, a sprinkler is not very effective. One method is to simply soak the ground with a hose. This allows the water to penetrate to the tree roots.
Ask the Experts!
Quick Elm Facts If your question isn't answered here, send it to us! ELMguard Trials Or visit the watering section of elmcare.com.
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http://www.elmcare.com/experts/water.htm [2/27/02 10:31:37 PM] Ask the Experts - Insects
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Last Update 30/08/00 What should I do to control the elm bark beetle population?
About Elmcare.com How Trees Work Question What should I do to control the elm bark beetle population? About Elm Trees Caring for Your Elm Answer Elm bark beetles are the major vector of Dutch elm disease. They Elm Tree Diseases carry the fungus on their backs and burrow into elm trees. There are The Elm Community a number of insecticides that are registered for use in controlling the
elm bark beetle population.
It is estimated, however, that less than 5% of elm bark beetles actually carry the fungus. The presence of the beetles does not necessarily indicate the presence of Dutch elm disease. Also, it is Ask the Experts! important to consult a professional applicator before using insecticides. Quick Elm Facts ELMguard Trials If your question is not answered here, send it to us! Or visit the Elm Tree Diseases section of elmcare.com.
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http://www.elmcare.com/experts/insects.htm [2/27/02 10:31:38 PM] Ask the Experts - Elms in General
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Last Update 30/08/00 Can I separate two elms that have grown together?
How suitable is the Siberian elm as a windbreak? About Elmcare.com How Trees Work How do I remove stumps? About Elm Trees What causes the bark to peel away? Caring for Your Elm Elm Tree Diseases Do elm trees lose their leaves in Florida? The Elm Community
Question Can I separate two elms that have grown together?
Answer Probably the best solution would be to pick the best one, keep it and
Ask the Experts! remove the other. I hate to suggest that you cut one seedling, but you will only have problems if you leave them together. I fear that if Quick Elm Facts you try to separate them you may lose both. ELMguard Trials
Question How suitable is the Siberian elm for use as a windbreak? Answer I would have to say the Siberian elm is considered a weed species in many cities. It is extremely hardy and will grow out of a crack in the pavement with very little soil available. It is a 'dirty' tree that sheds branches, leaves, seeds etc. , almost continually. If you are committed to maintenance then it can be used as a windbreak, but if the tree is left to grow without pruning it will soon become unmanageable and unsightly. The species is best used as a hedge species.
Question How do I remove stumps? Answer Have someone come with a stump grinder and grind it down al least 6 inches below the grade. If that doesn't work, there are over-the- counter products available at most garden centers that inhibit any new sprouting.
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Question My elm tree seems healthy, but I've noticed that there are large tracts of bark running vertically from the base up to 3-4 feet that can be easily peeled away. What may have caused this and what should I do? Answer When elms get to be larger in diameter, there is a tendency for outer bark to loosen to allow for the expansion of the tree. This is also why bark tends to be furrowed in appearance. Generally, as this is a natural occurrence, you need not take any special action. To be sure, however, it is always a good idea to consult a qualified arborist.
Question I live in Florida and I recently bought two elm trees. They both lost the majority of their leaves. Do elm trees usually lose their leaves this far south? Answer American elms are deciduous broadleaf trees and as such, they lose their leaves in the fall. In the natural habitat, I haven't heard of any instance where they kept their leaves for the winter. When they are transplanted into an area with a warmer climate such as Florida, however, they could potentially act quite differently.
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http://www.elmcare.com/experts/elms.htm (2 of 2) [2/27/02 10:31:40 PM] Ask the Experts - Dutch Elm Disease
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Last Update 30/08/00 Is Dutch elm disease a problem in Texas?
How long can DED remain dormant? About Elmcare.com How Trees Work Can you use dead elms for furniture? About Elm Trees Are some species more resistant to DED? Caring for Your Elm Elm Tree Diseases Can Nystatin be used to treat DED? The Elm Community
Question Is Dutch elm disease a problem in Texas?
Answer From what I can gather, there is an extremely low incidence of DED
Ask the Experts! in Texas. I was told that there is usually at least one confirmed case a year in Texas, but there has been no significant wholesale loss of elms due to DED. The native Cedar elm seems to display some level Quick Elm Facts of resistance to DED but I do not believe that this has been ELMguard Trials extensively tested. The American elm is not a prevalent species in the state.
Question How long can Dutch elm disease remain dormant in elm trees? Answer I found out that in one study, the researchers isolated the fungus in vessels in the tree that had been effectively sealed off in the tree for 25 years. The fungus that was isolated was still viable. If this occurs in trees it is generally not a threat to survival if the defense reactions effectively isolate the disease by the end of the growing season. If, however, the defense reactions are not complete, the fungus may be able to reach the newly forming vessels in the next growing season. When this happens there is a much higher likelihood that the disease will affect the entire tree and eventually kill it.
I must point out that this is not a common occurrence.
Question My Siberian elms died. I don't think it was Dutch elm disease and I want to use the wood for furniture. Is it safe?
http://www.elmcare.com/experts/ded.htm (1 of 2) [2/27/02 10:31:42 PM] Ask the Experts - Dutch Elm Disease
Answer Generally, DED does not kill Siberian elm trees. Usually only one branch will die as the species can effectively fend off the disease. I would be fairly certain that your trees are not infected with DED. If you remove all of the bark there should be no risk of bark beetles breeding in the wood. You should check with the local authorities, however, as there may be bylaws restricting the use of elm wood.
Question Are some elm species more resistant to Dutch elm disease than others? Answer Yes. Species that have coexisted with the Dutch elm disease fungus for the longest period tend to have the highest degree of resistance. These species have evolved to develop better defenses against the pathogen. Scientists now believe that Dutch elm disease originated in central Asia. Therefore, we would expect that species originating from Asia would show an increased resistance to DED and in fact that is what we do see. The Siberian elm, for example, is largely resistant. Species such as the American elm, however, have only recently come into contact with the disease and as such have not had the time to develop immunity.
Scientists are now working towards developing cultivars which exhibit greater resistance to Dutch elm disease. The Liberty Elm is one such cultivar.
Question I have heard of an antifungal called Nystatin. Can it be used to treat Dutch elm disease? Answer Because Nystatin is an antifungal, it could conceivably have an effect on Dutch elm disease. The drug was, however, designed for use on humans and is relatively expensive to procure. A major concern about the use of Nystatin arises from the fact that it is an antibiotic. As a result, overuse can lead to more aggressive strains of the fungus.
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http://www.elmcare.com/experts/ded.htm (2 of 2) [2/27/02 10:31:42 PM] Ask the Experts - Pruning
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Last Update 30/08/00
Does pruning make a tree grow faster?
About Elmcare.com Why can't I prune in my municipality? How Trees Work
About Elm Trees Caring for Your Elm Elm Tree Diseases Question Does pruning make a tree grow faster? The Elm Community Answer I'm not sure that pruning will help the tree to grow faster, but it will help if you prune out weak, crossing and interfering branches and direct future growth into the good structure. Ideally you should keep as much foliage as possible so that the tree can produce and establish a solid root system - especially when the tree is young. I Ask the Experts! would consult a local arborist before you do any pruning.
Quick Elm Facts
ELMguard Trials Question There is a law in my municipality against pruning an elm tree, but other trees can be pruned. Why is that? Answer That's a good question. The answer lies with the way that Dutch elm disease is transmitted. The elm bark beetle, which carries the DED fungus on its back, is most active from mid-spring until late summer. These beetles are attracted to the open wounds that are left on a tree after pruning. Therefore, you should only prune an elm when the beetles are relatively inactive which is in early spring or fall.
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http://www.elmcare.com/experts/prun.htm [2/27/02 10:31:44 PM] Ask the Experts - Other Diseases
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Last Update 30/08/00 How do I know if my tree has elm yellows?
What can I do if my tree has wetwood? About Elmcare.com
How Trees Work About Elm Trees Question How do I know if my tree has Elm Yellows? Caring for Your Elm Elm Tree Diseases The Elm Community Answer You can test for elm yellows by cutting a small potentially infected branch and placing it in a sealed glass jar. After a couple of hours, open the jar and smell inside to see if you detect a wintergreen odour. This is a telltale sign.
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Quick Elm Facts ELMguard Trials Question What can I do if my tree has wetwood? Answer In, general, there is not a lot that you can do about Wetwood. Wetwood is caused by a bacterial infection and is very common in elms and many other species. The infection causes moisture to be retained in the wood and also produces metabolic gases that increase the internal pressures in the tree. Periodically the liquid will be forced out of the tree through wound sites. The liquid oozes out and down the tree, where other organisms colonize it. This liquid is called slime flux and is known to have a foul odour.
Wetwood becomes a problem only when enough infection sites occur on the tree to compromise its structural integrity. A professional or consulting arborist should judge this. Otherwise, wetwood can be viewed as somewhat beneficial, as the moist environment that it creates in the tree helps to prevent decay fungi from colonizing the tree.
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http://www.elmcare.com/experts/other_diseases.htm (1 of 2) [2/27/02 10:31:46 PM] Ask the Experts - Other Diseases
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http://www.elmcare.com/experts/other_diseases.htm (2 of 2) [2/27/02 10:31:46 PM] Ask the Experts - Wood
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Can I use elm firewood given to me by a tree removal company?
About Elmcare.com Is furniture made of elm wood prone to cracking? How Trees Work
About Elm Trees Caring for Your Elm Elm Tree Diseases Question Can I use elm firewood given to me by a tree removal company? The Elm Community Answer I would be very concerned about the wood and the possibility of disease. Tree companies will often have trouble disposing of wood and will jump at the opportunity of giving it away rather than hauling it away. Many of them are rather unscrupulous and will tell you what you want to hear if it is in their best interest. You could very well Ask the Experts! spread the disease in your area by having the wood there. Many jurisdictions have strict bans on elm firewood with stiff penalties if it is found on your property. There is a characteristic streaking of the Quick Elm Facts wood that can be seen in infected branches, but sometimes that is ELMguard Trials hard to detect if you are not familiar with the symptom. If the wood is very dry and the bark is loose or absent then there is little to be concerned about. If not, then you could have a problem. Elms are very vigorous trees and don't die very easily, so I wonder why the tree died if it was not DED. I would suggest contacting a local urban forester or a consulting arborist ASAP, as the bark beetles that transfer the disease will fly to healthy trees any time soon. This could be a serious problem for your neighbourhood.
Question Is furniture made of elm wood prone to cracking in dry areas?
http://www.elmcare.com/experts/wood.htm (1 of 2) [2/27/02 10:31:48 PM] Ask the Experts - Wood
Answer It seems that if that much time has been taken to dry the wood it should be fairly dry. The only question remaining is whether it was dried outside or inside. If outside, it will probably have about 15% residual moisture and that can drop to 4-5% inside in the driest time of the year. The other question raised is how was the piece cut? If the slice was made along the grain of the wood there is a much lower likelihood that it will split than if the piece was cut on an angle across the grain. You should also see how the final finish has been applied and how well all the surfaces have been sealed. The finish should be highly impermeable to moisture.
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http://www.elmcare.com/experts/wood.htm (2 of 2) [2/27/02 10:31:48 PM] Identifying Silhouette
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Home > About Elms > Identifying Elms > Silhouette Last Update 30/08/00
How Trees Work The American elm is one of the largest trees in eastern North America and it grows to a height of About Elm Trees 35m with a trunk diameter of 175cm. The base of the tree is The Elm Story reinforced by prominent root flares Identifying Elms and a shallow and wide-spreading Elm Species root system. A few large upright Biology of Elms limbs support many outwardly fanning branches. Caring for Your Elm Elm Tree Diseases The tips of these branches often Elm Tree Links droop downwards contributing to the overall graceful umbrella-like Quick Elm Facts silhouette. Fully mature trees can live as long as 300 years, although in areas which have experienced Dutch elm disease, young trees less than 30 years old are the norm.
Leaves Bark
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http://www.elmcare.com/about_elms/identifying/identifying_silhouette.htm [2/27/02 10:31:50 PM] Identifying Leaves
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Home > About Elms > Identifying Elms > Leaves Last Update 30/08/00 Elm leaves are deciduous and alternate in two rows along the How Trees Work shoot. The shape is oval and tapers towards a point. The edge is ragged and saw-toothed and veins are prominent. The size is About Elm Trees dependent on the species, but the leaves of an American elm are The Elm Story usually between 10 and 15 cm in Identifying Elms length. Elm Species Biology of Elms Notice the uneven base on each leaf. This characteristic is Caring for Your Elm common in elms and is a good
Elm Tree Diseases thing to look for. Elm Tree Links Quick Elm Facts
Silhouette Bark
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http://www.elmcare.com/about_elms/identifying/identifying_leaves.htm [2/27/02 10:31:52 PM] Identifying Bark
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Home > About Elms > Identifying Elms > Bark Last Update 30/08/00 The bark of an American elm is dark grayish- brown becoming mottled ash-gray as the tree How Trees Work ages. The surface is deeply furrowed with broad obliquely intersecting ridges. About Elm Trees
The Elm Story Identifying Elms Elm Species Biology of Elms
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Silhouette Leaves
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http://www.elmcare.com/about_elms/identifying/identifying_bark.htm [2/27/02 10:31:54 PM] The Cultivated Elm
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Home > About Elms > The Elm Story > The Cultivated Elm Last Update 30/08/00
How Trees Work Long Ago
We have been using the elm tree for thousands About Elm Trees of years since the first farmers found them in ancient forests. The Elm Story Identifying Elms Elm Species In western Europe, farmers used elm leaves Biology of Elms and branches as cattle feed. Fisherman traded for elm leaves to boil and eat in times of scarcity. Caring for Your Elm Elm Tree Diseases Romans used living elms to support their Elm Tree Links grapevines - a practice called "marrying the Quick Elm Facts vine to the elm." They also selectively bred elms producing many of the species we see today throughout their former Empire.
In North America, the Iroquois used the bark of elms to make canoes, rope, utensils, and roofing for their homes. The Ainu, native people of Japan, used elm bark for clothing.
Luxurious Shade
Until recently, elms were the predominant shade tree in North America.
Elms, like other shade trees, are nature’s air conditioners. They help to cool not just by providing shade but by the transpiration of water from their leaves. In fact, the cooling effect of one urban elm tree is equivalent to five air conditioning units.
And like all trees, elms are a natural air purifier converting carbon dioxide into oxygen.
Rural Roots
http://www.elmcare.com/about_elms/elms_and_humans.htm (1 of 2) [2/27/02 10:31:57 PM] The Cultivated Elm
The hardy elm trees readily endures the severe winters of the US Midwest and the Canadian Prairies.
Shelterbelts of elm trees provide shade for livestock and protect farms from biting winds and storms.
Because their wood is particularly tough, farmers often left elms standing when clearing fields. To this day, you can see solitary elms in the middle of large open fields.
Industrial Benefits
The tough cross-grained wood of the elm tree is highly resistant to splitting. It is used to make baskets, furniture, and flooring. Hockey sticks, wheel hubs and boat frames have all taken advantage of the special properties of elm wood.
A Special Affection
Appreciation of the elm tree is evidenced by North American settlers, who named the elm “the lady of the forest”. Countless poems have been penned about the stately giant.
It also figures in many historical events. For example, George Washington first drew his sword underneath the Washington Elm in 1775. Poet James Russell Lowell wrote of Washington: “What figure more immovably august, Than that grave strength so patient and so pure.” (Atlantic Monthly: 1875 36)
What better words to describe the elm itself?
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http://www.elmcare.com/about_elms/elms_and_humans.htm (2 of 2) [2/27/02 10:31:57 PM] Living History
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Home > About Elms > The Elm Story > Living History Last Update 30/08/00 From the Liberty Elm in Boston to the Wolseley Elm in Winnipeg, elms have been focal points of How Trees Work community and political action.
About Elm Trees Click on one of the following to learn more:
The Elm Story Identifying Elms The Liberty Elm The Wolseley Elm Elm Species The Washington Elm William Penn's Elm Biology of Elms
Caring for Your Elm Elm Tree Diseases Elm Tree Links Quick Elm Facts Courtesy APS (www.scisoc.org)
Do you know of any historically significant elms not listed above?
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http://www.elmcare.com/about_elms/history/elms_living_history.htm [2/27/02 10:31:59 PM] Liberty Elm
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Home > About Elms > The Elm Story > Living History > The Liberty Elm Last Update 30/08/00 Boston's Liberty Elm is arguably the first symbol of freedom for the United States. It was a backdrop to oration, celebration, and revolution. How Trees Work On August 14, 1765, colonists hung effigies of Lord Butte and Andrew Oliver in About Elm Trees protest against the despised Stamp Act. Revolutionaries held rallies and speeches around the tree. The Elm Story Identifying Elms It was cut down by departing British soldiers in 1775. Elm Species Biology of Elms Back to "Living History"
Caring for Your Elm
Elm Tree Diseases Do you know of any historically significant elms? Elm Tree Links Quick Elm Facts If so, e-mail us at [email protected]
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http://www.elmcare.com/about_elms/history/liberty_elm_boston.htm [2/27/02 10:32:00 PM] Wolseley Elm
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Home > About Elms > The Elm Story > Living History > The Wolseley Elm Last Update 30/08/00 In Winnipeg, Manitoba, in the late 1950's, city officials wanted to remove a majestic elm to make way for a new street. Outraged, a group of women locked How Trees Work arms around the tree in protest. The city backed down and the tree was saved.
About Elm Trees Years later, the tree was lost to vandalism. But after it was taken down, a new elm was planted to take its place. The Elm Story Identifying Elms The Wolseley Elm is now part of Winnipeg's folklore. Elm Species Biology of Elms Source: Manitoba's "Coalition to Save the Elms." (www.savetheelms.mb.ca) Caring for Your Elm Elm Tree Diseases Back to "Living History" Elm Tree Links Quick Elm Facts Do you know of any historically significant elms not listed above?
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http://www.elmcare.com/about_elms/history/wolseley_elm.htm [2/27/02 10:32:02 PM] Washington Elm
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Home > About Elms > The Elm Story > Living History > The Washington Elm Last Update 30/08/00
How Trees Work George Washington took control of the revolutionary army and first drew his sword underneath this tree in 1775. About Elm Trees The tree died in 1923. The Elm Story Identifying Elms Back to "Living History" Elm Species Biology of Elms Library of Congress, Prints and Photographs Division, Detroit Publishing Company Collection Caring for Your Elm Elm Tree Diseases Do you know of any historically significant elms? Elm Tree Links If so, e-mail us at [email protected] Quick Elm Facts
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http://www.elmcare.com/about_elms/history/washington_elm.htm [2/27/02 10:32:04 PM] William Penn's Elm
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Home > About Elms > The Elm Story > Living History > William Penn's Elm Last Update 30/08/00 William Penn signed the Treaty of Shackamaxon with the Delaware Indians underneath a huge elm. How Trees Work This treaty formalized the purchase of land in About Elm Trees Pennsylvania. It also marked the beginning of an amicable relationship between the Quakers and the The Elm Story Indians that lasted for almost a hundred years. Identifying Elms Elm Species Biology of Elms In 1810, a storm blew the tree down. It was a grand 280 years old. Today, items made from the wood of that elm are considered valuable antiques.
Caring for Your Elm Back to "Living History" Elm Tree Diseases Elm Tree Links Quick Elm Facts Do you know of any historically significant elms?
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http://www.elmcare.com/about_elms/history/william_penn_elm.htm [2/27/02 10:32:05 PM] Elms in Literature
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Home > About Elms > The Elm Story > Elms In Literature Last Update 30/08/00
How Trees Work The elm has enchanted and inspired poets for countless generations.
About Elm Trees Click on a name to read more: The Elm Story Identifying Elms Elm Species Robert Frost John Milton Biology of Elms Ralph Waldo Emerson Robert Browning Herman Melville Erasmus Darwin Denise Levertov William Butler Yeats Caring for Your Elm Phillip Freneau Alfred Tennyson Elm Tree Diseases William Wordsworth Sylvia Plath Elm Tree Links John Clare Oliver Wendell Holmes Quick Elm Facts Ovid Virgil Theocritus
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http://www.elmcare.com/about_elms/literature/elms_in_literature.htm [2/27/02 10:32:07 PM] Robert Frost
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Home > About Elms > The Elm Story > Elms in Literature > Robert Frost Last Update 30/08/00 Robert Frost (1874-1963) From "The Cocoon" How Trees Work As far as I can see, this autumn haze About Elm Trees That spreading in the evening air The Elm Story both ways Identifying Elms Makes the new moon look Elm Species anything but new Biology of Elms And pours the elm-tree meadow full of blue, Is all the smoke from one poor Caring for Your Elm house alone. Elm Tree Diseases Elm Tree Links Quick Elm Facts Back
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http://www.elmcare.com/about_elms/literature/robert_frost.htm [2/27/02 10:32:09 PM] John Milton
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Home > About Elms > The Elm Story > Elms in Literature > John Milton Last Update 30/08/00
John Milton (1608-1674) How Trees Work From "Comus" About Elm Trees Perhaps some cold bank is her bolster The Elm Story now, Identifying Elms Or 'gainst the rugged bark of some broad Elm Species elm Biology of Elms Leans her unpillowed head fraught with sad fears
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http://www.elmcare.com/about_elms/literature/john_milton.htm [2/27/02 10:32:11 PM] Ralph Waldo Emerson
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Home > About Elms > The Elm Story > Elms in Literature > Ralph Waldo Emerson Last Update 30/08/00
Ralph Waldo Emerson (1803-1882) How Trees Work
From "Compensation" About Elm Trees Man's the elm, and Wealth the vine, The Elm Story Identifying Elms Stanch and strong the tendrils twine Elm Species
Biology of Elms
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http://www.elmcare.com/about_elms/literature/ralph_waldo_emerson.htm [2/27/02 10:32:14 PM] Robert Browning
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Home > About Elms > The Elm Story > Elms in Literature > Robert Browning Last Update 30/08/00
Robert Browning (1812~1889) How Trees Work "Oh, to be in England" About Elm Trees Oh, to be in England The Elm Story Now that April's there, Identifying Elms And whoever wakes in England Elm Species Sees, some morning, unaware, Biology of Elms That the lowest boughs and the brushwood sheaf Round the elm-tree bole are in tiny leaf Round the chaffinch sings on the orchard bough Caring for Your Elm In England - now! Elm Tree Diseases
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http://www.elmcare.com/about_elms/literature/robert_browning.htm [2/27/02 10:32:15 PM] Herman Melville
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Home > About Elms > The Elm Story > Elms in Literature > Herman Melville Last Update 30/08/00
Herman Melville (1819-1891) How Trees Work From "Malvern Hill" About Elm Trees We elms of Malvern Hill The Elm Story Remember everything; Identifying Elms But sap the twig will fill: Elm Species Wag the world how it will, Biology of Elms Leaves must be green in Spring
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http://www.elmcare.com/about_elms/literature/herman_melville.htm [2/27/02 10:32:17 PM] Erasmus Darwin
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Last Update 30/08/00 Erasmus Darwin (1731~1802)
About Elmcare.com From "Untitled" How Trees Work Herb, shrub, and tree, with strong emotions About Elm Trees rise For light and air, and battle in the skies; The Elm Story Whose roots diverging with opposing toil Identifying Elms Contend below for moisture and soil; Elm Species Round the tall Elm the flattering Ivies bend, Biology of Elms And strangle, as they clasp, their struggling friend.
Caring for Your Elm Back Elm Tree Diseases The Elm Community
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http://www.elmcare.com/about_elms/literature/erasmus_darwin.htm [2/27/02 10:32:20 PM] Denise Levertov
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Home > About Elms > The Elm Story > Elms in Literature > Denise Levertov Last Update 30/08/00 Denise Levertov (1923-1997)
How Trees Work "Living While it May"
About Elm Trees The young elm that must be cut because its roots push at the house wall The Elm Story Identifying Elms taps and scrapes my window Elm Species urgently - but when I look round at it Biology of Elms remains still
Denise Levertov by David Geier Caring for Your Elm Photography Elm Tree Diseases Back Elm Tree Links Quick Elm Facts
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http://www.elmcare.com/about_elms/literature/denise_levertov.htm [2/27/02 10:32:22 PM] William Butler Yeats
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Home > About Elms > The Elm Story > Elms in Literature > William Butler Yeats Last Update 30/08/00
William Butler Yeats (1865~1939) How Trees Work From "My House" About Elm Trees An ancient bridge, and a more ancient The Elm Story tower, Identifying Elms A farmhouse that is sheltered by its wall, Elm Species An acre of stony ground, Biology of Elms Where the symbolic rose can break in flower, Old ragged elms, old thorns innumerable. Caring for Your Elm
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http://www.elmcare.com/about_elms/literature/william_butler_yeats.htm [2/27/02 10:32:24 PM] Phillip Freneau
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Home > About Elms > The Elm Story > Elms in Literature > Phillip Freneau Last Update 30/08/00
Phillip Freneau (1752~1832) How Trees Work From "The Indian Burying Ground" About Elm Trees Here still an aged elm aspires, The Elm Story Beneath whose far-projecting shade Identifying Elms (And which the shepherd still admires) Elm Species The children of the forest played. Biology of Elms
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http://www.elmcare.com/about_elms/literature/phillip_freneau.htm [2/27/02 10:32:26 PM] Alfred Tennyson
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Home > About Elms > The Elm Story > Elms in Literature > Alfred Tennyson Last Update 30/08/00
Alfred Tennyson (1809~1892) How Trees Work From "Untitled"
About Elm Trees And gathering freshlier overhead The Elm Story Rocked the full-foliaged elms, and swung Identifying Elms The heavy-folded rose, and flung Elm Species The lilies to and fro, and said, Biology of Elms "The dawn, the dawn," and died away; And East and West, without a breath, Mixt their dim lights, like life and death, Caring for Your Elm To broaden into boundless day. Elm Tree Diseases From "Come Down, O Maid" Elm Tree Links Quick Elm Facts Sweeter thy voice, but every sound is sweet Myriads of rivulets, hurrying through the lawn, The moan of doves in immemorial elms, And murmuring of innumerable bees.
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http://www.elmcare.com/about_elms/literature/alfred_tennyson.htm [2/27/02 10:32:28 PM] William Wordsworth
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Home > About Elms > The Elm Story > Elms in Literature > William Wordsworth Last Update 30/08/00
William Wordsworth (1770~1850) How Trees Work From "Untitled" About Elm Trees Thither I came, and there, amid the gloom The Elm Story Spread by a brotherhood of lofty elms Identifying Elms Appeared a roofless hut, four naked walls Elm Species That stared upon each other... Biology of Elms
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http://www.elmcare.com/about_elms/literature/william_wordsworth.htm [2/27/02 10:32:30 PM] Sylvia Plath
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Home > About Elms > The Elm Story > Elms in Literature > Sylvia Plath Last Update 30/08/00 Sylvia Plath (1932~1963) How Trees Work "Elm"
About Elm Trees I know the bottom, she says. I know it with my great tap root; The Elm Story It is what you fear. Identifying Elms I do not fear it: I have been there. Elm Species Biology of Elms Is it the sea you hear in me, Its dissatisfactions? Or the voice of nothing, that was you madness? Caring for Your Elm Love is a shadow. Elm Tree Diseases How you lie and cry after it. Elm Tree Links Listen: these are its hooves: it has gone off, like a horse. Quick Elm Facts All night I shall gallup thus, impetuously, Till your head is a stone, your pillow a little turf, Echoing, echoing.
Or shall I bring you the sound of poisons? This is rain now, the big hush. And this is the fruit of it: tin white, like arsenic.
I have suffered the atrocity of sunsets. Scorched to the root My red filaments burn and stand,a hand of wires.
Now I break up in pieces that fly about like clubs. A wind of such violence Will tolerate no bystanding: I must shriek.
The moon, also, is merciless: she would drag me Cruelly, being barren. Her radience scathes me. Or perhaps I have caught her.
I let her go. I let her go Diminished and flat, as after radical surgery. How your bad dreams possess and endow me.
I am inhabited by a cry.
http://www.elmcare.com/about_elms/literature/sylvia_plath.htm (1 of 2) [2/27/02 10:32:31 PM] Sylvia Plath
Nightly it flaps out Looking, with its hooks, for something to love.
I am terrified by this dark thing That sleeps in me; All day I feel its soft, feathery turnings, its malignity.
Clouds pass and disperse. Are those the faces of love, those pale irretrievables? Is it for such I agitate my heart?
I am incapable of more knowledge. What is this, this face So murderous in its strangle of branches?--
Its snaky acids kiss. It petrifies the will. These are the isolate, slow faults That kill, that kill, that kill.
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http://www.elmcare.com/about_elms/literature/sylvia_plath.htm (2 of 2) [2/27/02 10:32:31 PM] John Clare
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John Clare (1793-1864) How Trees Work From "The Elm Tree" About Elm Trees Old favourite tree thoust seen times change The Elm Story But change till now did never come to thee Identifying Elms For time beheld thee as his sacred dower Elm Species And nature claimed thee her domestic tree. Biology of Elms
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http://www.elmcare.com/about_elms/literature/john_clare.htm [2/27/02 10:32:34 PM] Oliver Wendell Holmes
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Oliver Wendell Holmes (1809-1894) How Trees Work The hubs of logs from the Settler's ellum, Last of its timber, they couldn't sell'em, About Elm Trees Never an axe had seen their chips, The Elm Story And the wedges flow from between their lips, Identifying Elms Their blunt ends frizzled like celery tips. Elm Species Biology of Elms
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http://www.elmcare.com/about_elms/literature/oliver_wendell_holmes.htm [2/27/02 10:32:36 PM] Ovid
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Home > About Elms > The Elm Story > Elms in Literature > Ovid Last Update 30/08/00 Ovid (43 B.C.~A.D. 17)
How Trees Work If that fair elm alone should stand, No grapes would glow with gold and tempt the hand, Or if that vine without her elm should grow, About Elm Trees T'would creep, a poor neglected shrub below. The Elm Story Identifying Elms From "Untitled" Elm Species Biology of Elms Help bucksome God then! so may the lov'd Vine Swarm with num'rous grapes, and big with Wine Load the kind Elm, and so thy Orgyes be Caring for Your Elm With priests lowd showtes, and Satyrs kept to thee! Elm Tree Diseases
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Home > About Elms > The Elm Story > Elms in Literature > Virgil Last Update 30/08/00
Virgil (70~19 B.C.) How Trees Work From "Untitled" About Elm Trees And great gods eke aggrievèd with our town. The Elm Story I saw Troye fall down in burning gledes, Identifying Elms Neptunus' town clean razèd from the soil, Elm Species Like as the elm forgrown in mountains high, Biology of Elms Round hewen with axe, that husbandmen With thick assaults strive to tear up, doth threat, And hackt beneath trembling doth bend his top, Caring for Your Elm Till gold with strokes, giving the latter crack, Rent from height, with ruin it doth fall. Elm Tree Diseases Elm Tree Links Quick Elm Facts Back
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Theocritus How Trees Work From "The Death of Daphnis" About Elm Trees Then rest we in the shadow of the elm The Elm Story Fronting Priapus and the Fountain-nymphs. Identifying Elms Elm Species Biology of Elms Back Caring for Your Elm
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http://www.elmcare.com/about_elms/literature/theocritus.htm [2/27/02 10:32:41 PM] Elms in Mythology
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Last Update 30/08/00 Elm trees have entered our mythology - a mark of their prominence in the lives of early civilizations. How Trees Work Germanic tribes included the elm in their creation myth, and Mongols incorporated About Elm Trees it in a wedding prayer.
The Elm Story Germanic Creation Myth Identifying Elms Elm Species Biology of Elms The ancient Germanic peoples who came to inhabit much of Europe, believed that
three gods, Odin, Vili and Ve, created the world. Caring for Your Elm According to the myth, these three gods were walking by the sea examining their Elm Tree Diseases handiwork when they came upon two fallen trees. One was an ash, the other an Elm Tree Links elm. Odin imbued them with the spark of life. Vili endowed them with spirit and a Quick Elm Facts thirst for knowledge. Ve gave them the gift of five senses.
When they had finished, the fallen trees resembled the gods themselves. Out of the ash came man. Woman was created from the elm and her name was Embla.
(Source: "Mythologies" compiled by Yves Bonnefoy v. 1, p.281)
Mongol Wedding Prayer
"Mother Ut (Fire), Mistress of Fire, descended from the elms on the tops of the Khangai-Khan and the Burkhatu-Khan mountains. Thou, who wast born when Heaven and Earth parted, who camest forth from the footprints of Mother Ötygen (Earth), thou creation of Tengeri-Khan. Mother Ut, thy father is the hard steel, thy mother the flint, thy ancestors, the elm trees. Thy brightness reaches the heavens and spreads over the earth. Thy brightness reaches the Heaven-dweller, nursed by the Mistress Uluken.
Goddess Ut, we offer thee yellow butter and a yellow-headed white sheep. Thine are this brave boy and the beautiful bride, the slender daughter."
(Source: "Mythology of All Races" vol. iv, Uno Holmberg, p.453)
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http://www.elmcare.com/images/hubbes_lab.jpg [2/27/02 10:32:50 PM] Hubbes1 Abstract
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About This Site How Trees Work The American Elm and Dutch Elm Disease About Elm Trees Caring for Your Elm M. Hubbes Elm Tree Diseases Faculty of Forestry, University of Toronto The Elm Abstract Community
Research Shortly after World War I, a new disease previously unknown among elms, Community emerged in Holland. It spread rapidly from Europe to Great Britain (1927), United States (1930), and Canada (1945), killing millions of elms. The disease known, as Dutch elm disease (DED) is a wilt disease, caused by the fungus Ophiostoma ulmi. It is transmitted from tree to tree by elm bark beetles (scolytid) vectors. Ask the Experts! Numerous attempts to control the disease have concentrated on the reduction of Quick Elm Facts insect vector populations, exploitation of natural host resistance, extensive ELMguard Trials application of fungicides and integrated pest management. In spite of these efforts in Canada, the disease continues to migrate westwards threatening the elm populations in Saskatchewan and Alberta. Today there are approximately 700,000 elm shade trees in cities and towns across Canada and their value exceeds $2.5 billion dollars.
With the advance of molecular biology new, powerful tools are now available to study, in greater detail, the molecular and biochemical mechanisms of the DED pathogen, with particular reference to the mechanisms that induce host defenses. A glycoprotein, has been isolated and identified such that when injected either in liquid or pellet form into the elm tree, significantly reduced the wilting symptoms of both 5 year old elm seedlings and 10 cam diameter trees. The elicitor induces a chain of defensive reactions that prevent the rapid spread of the fungus within the vascular system of the host.
Click here to view the entire article.
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Last Update 30/08/00
About Elmcare.com How Trees Work The American Elm and Dutch Elm Disease About Elm Trees Caring for Your Elm M. Hubbes Elm Tree Diseases Faculty of Forestry, University of Toronto The Elm Abstract Community
Research Shortly after World War I, a new disease previously unknown among elms, Community emerged in Holland. It spread rapidly from Europe to Great Britain (1927), United States (1930), and Canada (1945), killing millions of elms. The disease known, as Dutch elm disease (DED) is a wilt disease, caused by the fungus Ophiostoma ulmi. It is transmitted from tree to tree by elm bark beetles (scolytid) vectors. Ask the Experts! Numerous attempts to control the disease have concentrated on the reduction of Quick Elm Facts insect vector populations, exploitation of natural host resistance, extensive ELMguard Trials application of fungicides and integrated pest management. In spite of these efforts in Canada, the disease continues to migrate westwards threatening the elm populations in Saskatchewan and Alberta. Today there are approximately 700,000 elm shade trees in cities and towns across Canada and their value exceeds $2.5 billion dollars.
With the advance of molecular biology new, powerful tools are now available to study, in greater detail, the molecular and biochemical mechanisms of the DED pathogen, with particular reference to the mechanisms that induce host defenses. A glycoprotein, has been isolated and identified such that when injected either in liquid or pellet form into the elm tree, significantly reduced the wilting symptoms of both 5 year old elm seedlings and 10 cam diameter trees. The elicitor induces a chain of defensive reactions that prevent the rapid spread of the fungus within the vascular system of the host.
Introduction
Almost 80 years ago Dutch scientists reported the dramatic appearance of a new disease on elms in Holland. The disease quickly became known as Dutch elm disease (DED). It is caused by the fungus Ophiostoma ulmi (sensus lato), and has claimed the life of millions of stately elm trees in Europe and North America. Elms, and in particular the American elm (Ulmus americana), have been an
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unmistakable cultural and historic landmark of the North American continent. The tree’s tall and majestic growth combines beauty and grace, placing it among the most desirable shade tree in our cities and villages. Planted along boulevards and streets, their crowns span roads and houses providing clean air, coolness during hot summer days and shelter against UV radiation. The New York Times, in a February 26, 1989 article, claimed that a large tree is equivalent to five air conditioning units, playing a very important energy conservation role in our ecosystem.
Shortly after World War I, in 1918, a new, previously unknown disease of elms emerged in Holland, which caused yellowing and then wilting of leaves as well as rapid tree death. The disease spread like a plague and traveled quickly from Europe to Great Britain (1927) and reached the United States in 1930 (Campana and Stipes 1981). Although some tree losses occurred in 1927 in England, it was the appearance of a new strain of the plague in the late 1960s that severely decimated the elm populations (Gibbs 1981). By 1980, 17 million of the 23 million previous existing elms had been killed in southern England, causing extensive economic, esthetic and environmental losses.
Around 1930 there were approximately 77 millions elm trees in cities and towns across North America. The introduction of the disease had a devastating effect. For example, by 1976 municipalities in the northeastern United States lost 56% of their original elm population (Huntley 1982).
Equally significant, a second introduction of the disease to the North American continent at Sorell, Quebec, Canada in 1945 (Pomerleau 1981) initiated one of the largest mass destruction of trees ever witnessed, particularly when the disease fronts from the US and eastern Canada met to migrate westwards. Of the 77 millions elms in the US prior to the disease introduction, only about 34 million survived by 1976. In Canada the eastern provinces, New Brunswick, Quebec, and Ontario also suffered major losses. More than 600,000 elms were quickly killed in Quebec and Toronto’s 35,000 elm tree population was rapidly reduced by 80% (Huntley 1982). Presently the disease front has reached the elm populations of Saskatchewan and threatens those of Alberta. This situation causes great concern to private citizens as well as provincial and municipal authorities. In the prairie provinces, elms constitute the majority of shade trees in cities and villages. No other tree is better suited than the elm to withstand the harsh winter climate and urban environmental stresses in these regions, with its high winds, extreme temperatures and road salt. Therefore the great efforts of the City of Winnipeg for example to save their elms through a fully integrated management program, allows the City to claim itself as the City of elms. However, in spite of this, successful control programs after 21 years the losses of trees due to DED went from 2.5% to near 5.0% annually in 1996. Winnipeg’s American elm population still exceeds 200,000 in number. Today there are about 700,000 elms as shade trees in cities and towns across Canada and their value well exceeds $2.5 billion. The average elm tree value is based on the data given by Westwood (1991).
Disease control
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The DED fungus is mainly transmitted from tree to tree by the European elm bark beetle Scolytus multistriatus and the native elm bark beetle Hylurgopinus rufipes (Parker et al. 1947, Jin et al. 1996). Infection, by DED usually occurs from late May to July while the trees are producing “early wood” in the form of large vessel cells (Pomerleau 1968, Smalley and Guries 1993). Therefore, the spring-maturating adults of the European elm bark beetles and the over wintering adults of native elm bark beetles are the most common vectors of the disease (Pomerleau 1965, Lanier 1978, Lanier and Peacock 1981, Webber 1990). In addition the fungus may also move internally from tree to tree through root grafts (Stipes and Campana 1981).
Numerous attempts to control the disease have concentrated on three processes: reducing the vector populations namely the elm bark beetles (Lanier 1978, O’Callahan and Fairhurst 1983, Jin et al. 1996), the exploitation of natural host resistance (Ouellett and Pomerleau 1965, Holmes 1976, Lester 1978, Stipes and Campana 1981, Heybroek 1983, Smalley and Guries 1993, Ware and Miller 1997), and extensive application of fungicides (Smalley 1978, Stennes and French 1987). For the most part, these efforts have not produced the expected results of DED control (Stipes and Campana 1981, Sticklen et al. 1991).
Reduction of vector populations
Control of elm bark beetles, via chemical insecticides still seems the preferred choice in areas of high beetle populations to reduce the inoculum potential. However, in the long run this option is not viable because of the potential negative impact of the chemical insecticides to the environment and therefore can only be recommended for very specific situations. Particular attention must also be given to the selection of correct application equipment otherwise spraying is not very effective (Roy et al. 1988). The use of biological control agents such as insect parasitic (entomopathogenic) nematodes against bark beetles has not yet been exploited and awaits further development (Tomalak et al. 1989). The same is also true for the Lepidopteran BT toxins (Sticklen et al. 1991). The use of pheromone traps for vector control has great attraction from an environmental point of view. However it did not gain the expected momentum because the results were not as anticipated (Birch et al. 1981, Sticklen et al. 1991). Lanier (1989) reported on the usefulness of elm bark beetle trap trees for control of DED. This method seems very appealing, but awaits its wider testing application and has little use in many towns and cities because trees cannot be spared for traps. Sanitation, though expensive, is imperative for a successful DED control program, by removing infected tree parts, or dead trees that harbor beetle populations as well as the perfect and imperfect stage of the fungus. If not removed and destroyed, these dead trees are a major source of inoculum. However, sanitation alone is unable to halt the progress and spread of the disease (Pomerleau 1981).
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Chemical control
The introduction of several benzimidazole systemic fungicides has prompted a number of investigations on the effect of these compounds for DED control. Of these, benomyl has been tested against O. ulmi (Kondo et al. 1973). Another chemically related compound known as “Arbotect 20-S” has also been reported as active against the fungus (Smalley 1978, Prosser 1998). Attempts to overcome uptake and solubility problems caused by the tree were made by injecting the chemical into the stem or by uptake experiments through the roots (Kondo 1978, Roy et al. 1980). Compartmentalization of the tree (Shigo and Campana 1977), in response to wounding during injection, solubility problems with the chemical, as well as the ability of the pathogen to develop resistance against the fungicide (Bernier and Hubbes 1990a, b, Schreiber 1993), and economic reasons did not lend themselves for very large scale application of these fungicides.
Dutch elm disease is a vascular disease. To effectively colonize its host, the DED fungus has to invade a large number of vessels and can therefore not rely on its passive travel in the transpiration stream of a limited number of vessels. It has to spread from vessel to vessel. Pit membranes are the places where this can occur. Spores have to germinate and their hyphae penetrate through the membranes. Scheffer et al. (1988) reported that sterol biosynthesis inhibitors that interfere in the hyphae formation in O. ulmi suppressed disease development in two Dutch elm clones. Among a number of chemical derivatives fenpropimorph gave the best results. The problem is that this chemical renders the tree frost sensitive. Very recently another compound, a triazole derivative fungicide propiconazole, also known as “Alamo”, has been introduced for DED control. It is too soon to judge its effectiveness. Some tests appear encouraging, while others were not as successful as those were with “Arbotect 20-S” (Prosser 1998). However the manufacturer has withdrawn this latter product from the Canadian market.
Natural host resistance
The prospects for developing trees with genetic resistance to DED range from uncertain (Ouellett and Pomerleau 1965, Holmes 1976) to very well (Heybroek 1993, Smalley and Guries 1993, Smalley et al. 1993, Ware and Miller 1997). Earlier efforts to select and breed American elms (Ulmus americana) for DED resistance were disappointing. All North American species (U. rubra, U. thomasii, U. alata, U. serotina, and U. erassifolia) are susceptible to DED. U. americana is the most susceptible. Therefore efforts were also directed towards the development of genetic combinations from European and Asian gene pools (Smalley and Guries 1993, Smalley et al. 1993, Townsend and Santamour 1993, Sherald 1993, Ware and Miller 1997). A number of selections with superior resistance to DED were made of which the American “Liberty” elms were the most promising ones. There is a problem with these selections, as the basis for their resistance is unknown to scientists and therefore no estimates can be made as to whether this resistance will last or not. Small changes in the genetic background of
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the fungal population or changes in the physiology of the host as it ages may cause loss of resistance. Indeed, the DED fungus attacks some of the formerly resistant “Liberty” elms (A.L Shigo, personal communication).
It has been debated how the DED fungus kills its host. I believe that , a final solution to these problems can only be expected through application of modern methods of molecular biology by identification, isolation and subsequently directed rearrangement of genes controlling pathogen (DED) virulence and genes governing the host’s defense. Once the genetic bases of pathogen virulence and host resistance have been clarified, trees with long term tolerance towards the pathogen can be developed (Hubbes 1981, 1993). This for example has been achieved by the Siberian elm (U. pumila) probably through natural selection.
The fact that the Asian elms show resistance towards DED led to the assumption that DED originated in Asia. Recent investigations place its origin in the Himalayas (Brasier and Mehrotra 1995).
Although the development of resistant elms may satisfy the long-term strategy of DED control, effective protection of the existing elm populations in our cities and villages still remains a problem. In the past, there has been no lack of efforts to control the pathogen by biological means with the use of antagonistic microorganisms such as bacteria (Mazzone et al. 1982, Strobel and Myers 1982, Holmes and Plourde 1982, White 1982, Shi and Brasier 1986), fungi and virus particles (Hoch et al. 1985, Rogers et al. 1986, Webber 1987, Bernier et al. 1996). Some of the organisms showed promise, but their broad application as control agents has not yet been achieved. It is surprising that most of these treatments were conducted solely with the view to inhibit the fungal growth by direct antagonism, while the role of the host’s defense reactions was ignored. Field observations show that some trees have the means to defend themselves successfully against the invasion of the DED pathogen by restricting the spread of the fungus in their vessels. We assume if the mechanisms of this defense reaction could be clarified and their genetic basis understood they might well form a solid basis for disease control and resistance breeding.
The pathogen and its strains
In the early 1970’s, the observation that the population of O. ulmi was composed of two major group of strains, the aggressive and non-aggressive group, gave rise to numerous assumptions to explain pathogenicity and virulence (Gibbs et al. 1972, Bernier 1983). The non-aggressive isolates induce slower development for foliar symptoms during the first year of infection, a difference that tends to disappear during the second year (Schreiber and Townsend 1976). Scala et al. (1997) reported similar results. Isolates of the aggressive group very quickly induce severe wilting symptoms leading to the death of the hosts.
Aggressive and non-aggressive group of isolates also differ in a wide range of http://www.elmcare.com/community/research/hubbes1.htm (5 of 22) [2/27/02 10:33:01 PM] Elmcare.com - Hubbes 1
morphological and physiological characters. Crossing between the two groups is believed to be rare under field conditions (Gibbs and Brasier 1973, Brasier 1977, 1979, 1982). The aggressive group has been further subdivided in two races termed as the European (EAN) and North American (NAN) races (Brasier 1988). Initial separation of the isolates into the various sub-groups based on morphological characters was often erratic. Various well known laboratory techniques to identify isolated strains such as isozyme and protein patterns as well as restriction fragment length polymorphisms (RFLPs) and DNA fingerprinting have proven to be a very reliable approach to accurate strainal characterization (Bernier et al. 1983, Jeng and Hubbes 1983, Bates et al. 1989, Jeng et al. 1991, Hintz et al. 1991).
These methods also provide a better view into the genome (all the genes carried by a haploid germ cell) of the pathogen than earlier methods. For example, Jeng et al. (1991) showed that the size of the mitochondrial genome was 40% larger for the non-aggressive isolates than for the aggressive ones. The restriction site map of the mitochondrial genome which is a diagram portraying a linear array of sites on the DNA segment at which specific enzymes cleave the molecule, showed that the various isolate groups differed from each other by discrete length mutations in their mitochondrial genome (Hintz et al. 1991). Based on the above criteria and some physiological characters, Brasier (1991) separated the aggressive sub-group from the non-aggressive one by classifying the former as a new species, which he named O. novo-ulmi, while the non-aggressive group maintained the name O. ulmi. Further investigations by Jeng et al. (1996) showed that the DNA sequence of the ITS1 and ITS2 region of the ribosomal gene of the aggressive and non- aggressive group display high homology but differ between each other in one DNA base pair showing the close relatedness of the two groups. The ribosomal gene is a very important genetic marker. It is highly conserved, stable and shows little change over long time periods. However some of its regions (DNA stretches) such as those known as internal spacers (ITS) show some variation while others known as 18S, 5.8S, or 26-28S are very stable. Both are used for characterization of taxonomic units. Lately Brasier and Mehrotra (1995) described a third species belonging to the Ophiostoma group: O. himal-ulmi. This species has been found on U. wallichiana in the Himalayas and lead to the hypothesis that the DED may have its origin in this relatively narrow geographic region.
Methods of molecular biology such as RFLPs of mitochondrial DNA (mtDNA), nuclear DNA fingerprinting and RFLPs of the ribosomal DNA (rDNA) are very sensitive tools not only for strainal characterization but also for monitoring population dynamics. Studies of strains of O. ulmi population from Manitoba, southeastern Saskatchewan and northern Dakota show that these populations are composed of well defined fungal strains (Hintz et al. 1993, Hubbes 1992). This observation is based on the restriction site pattern of the mtDNA. Analysis of the nuclear DNA fingerprinting and rDNA reveal that the nuclear type of all isolates is that of the aggressive sub-group (O. novo-ulmi) (Hubbes 1992). Mitochondrial DNA in O. ulmi is inherited from the mother and the nuclear DNA from the father (unpublished results from our laboratory). This means those strains carrying non- aggressive mitochondrial types and aggressive nuclear types resulted from a cross between a non-aggressive mother (O. ulmi) and an aggressive father. Such strains have been reported for Manitoba (Hubbes 1992). Very recently Brasier et al.
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(1998) found similar strains in Europe. These observations are of great importance for the selection and breeding strategies which attempt to develop elms that in future can tolerate the disease like Siberian elms. It further indicates that under North American field conditions the number of strains is rather limited, a fact that has also been found by Brasier (1996). Changes in non-aggressive and aggressive subgroups within two populations of American elm in New England has also been reported by Houston (1991), a fact already known from Europe (Brasier 1991). The population of the non-aggressive subgroup is declining.
Furthermore, spore deficient strains of O. ulmi have been successfully isolated; these natural mutants lack the ability to produce conidiospores, blastospores, and ascospores. As a result of these mutants, O. ulmi is incapable of causing internal and external disease symptoms normally associated with DED (Richards et al. 1982, Richards, 1993, 1994, 1998). Spore production is of insturmental importance for the pathogen for transmittance by the elm bark beetle vector and rapid distribution within the elms vascular system. Understanding the mechanism(s) that block O. ulmi sporulation may be very helpful in developing methods of DED control.
Fungal metabolites as factors of virulence
Although the aggressiveness of O. ulmi strains was initially established by inoculation experiments, the basis of this ability has not yet been precisely determined. Knowing these factors precisely would allow effective DED control strategies including the development and selection of long term disease tolerant American elms. Brasier and Gibbs (1976) have shown in crossing and subsequent inoculation experiments, that the F1 generation of the fungus does not exceed the virulence of their parents. Assumptions (based on circumstantial evidence) have been made that toxins, such as cerato ulmin (CU) (Takai 1980, Richards 1993), peptidorhamno-mannan (Claydon et al. 1980, Nordin and Storbel 1981, Scheffer 1983, Scheffer et al. 1987), glycopeptides and glycoprotein elicitors (Yang et al. 1989, Hubbes 1993) may function as factors of virulence. Binz and Canevascini (1996) stated that production of extra-cellular laccase may be important for the survival of the fungus in its host. Confirmation of these compounds as factors of virulence is still waiting. For example, experiments by Bernier (1988) did not confirm previous results by Takai (1980) showing a correlation between high CU production and virulence. It appeared that the only way to prove the role of CU as a key factor of virulence would be the production of a number of mutants that are unable to produce the CU toxin. These CU negative mutants (CU-) should not be able to cause DED when inoculated into elms. If they do, then CU is not a major virulence factor.
Bernier (1988) produced a large number of chemical induced mutants, but none were CU-. The problem with chemically induced mutants is that the fungal genome may be altered at many more sites than those phenotypically visible. This led to efforts to identify and isolate the genes responsible for CU production (Yaguchi et
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al. 1993, Bowden et al. 1994, Jeng et al. 1996). Once the CU gene had been isolated a CU- mutant was created by transformation-mediated gene disruption of an aggressive strain (O. novo-ulmi). Bioassay of the CU- strain in highly susceptible elm trees indicated no difference in percent of brown streaks under the bark and percent foliar wilting. Simultaneously Tegli and Scala (1996) obtained five CU- mutants by UV-irradiation. In their inoculation experiments two out of the five mutants showed significant reduction in pathogenicity when compared to the wild type. However, very likely the UV-treatment affected not only genes of the CU pathway but also a number of other genes sitting at important metabolic switching points not detected by the authors.
CU- strains do occur naturally and are pathogenic (Brasier et al. 1994). This would support the view that CU is not a major virulence factor. However there exists another possibility, i.e., that the gene(s) for pathogen virulence and CU production are located close to each other giving the impression of one single unit. The loss of one during reproduction or by mutation would not affect the expression of the other. Recent studies by Scala et al. (1997) found higher CU levels in wilting leaves of elm seedling infected with aggressive isolates (O. novo-ulmi) than in those leaves of seedlings infected with non-aggressive strains (O. ulmi). Temple (1997) found that a transformed non-aggressive strain, which over expresses CU production showed no alteration in virulence when compared to the parent strain. Unfortunately no experiments were conducted to test whether the CU gene of the aggressive strain was expressing the correct CU protein in vivo, as tested by Scala et al (1997). CU research is complicated with various conflicting results being obtained by different scientists. CU may one day be shown to be a major factor in pathogen fitness and virulence.
Virus-like RNA elements for the control of DED
In the mean time (Brasier 1983, 1986, Hoch et al. 1985, Rogers et al. 1986, Brasier et al. 1993, Webber 1987, 1993) described the occurrence of double stranded ribosomal nucleic acid (dsRNA) particles in isolates of the aggressive strains (O. novo ulmi) and non-aggressive strains, and termed them as d-factors. One of them, the d2 factor, has been associated with reduced vigor in infected isolates (Hong et al. 1998). Work in Brasier’s laboratory has been conducted to use the d-factor to control Dutch elm disease on a wide scale (Sutherland and Brasier 1997). The problem up to now has been that the d-factor is not easily transmitted from strain to strain, because not all strains are vegetatively compatible. Furthermore, the transformation of the fungus into the yeast phase, one of the main distribution phases of the fungus within the tree (Banfield 1941, Pomerleau and Mehran 1966, Pomerleau 1968) allows Ophiostoma individuals to lose deleterious d-factors (Webber 1993). Similar problems have been encountered in the US with hypovirulent strains of Cryphonectria parasitica, the causal agent of chestnut blight (Choi and Nuss 1992, Enebak et al. 1994). However recent investigations suggest that it is the effect of induced resistance triggered by the hypovirulent strain that is responsible for the survival of chestnuts infected by chestnut blight (Schafleitner and Wilhelm 1997, Ghabrial 1998). http://www.elmcare.com/community/research/hubbes1.htm (8 of 22) [2/27/02 10:33:01 PM] Elmcare.com - Hubbes 1
Apparently the transformation of virulent strains to hypo-virulent strains induces some changes in the physiology of hypo-virulent strains that affect the pathogen and mobilize effective defense reactions in the chestnut host.
Induced resistance for DED control
Our efforts here in Toronto concentrated on the defense mechanisms of elms in response to fungal infection. Cross-protection against aggressive strains of O. ulmi was reported in U. hollandica and U. americana (Scheffer et al. 1980, Hubbes and Jeng 1981). Seedlings of U. americana were indeed protected against the attack by aggressive strains when first inoculated with non-aggressive strains (Jeng et al. 1983, Duchesne 1985, Duchesne et al. 1986, Sutherland et al. 1995). We have isolated and identified a number of chemicals produced by the elm in response to the inoculations as mansonones A, C, D, E, F and G from fungal inhibitory sapwood extract of elm seedlings treated with O. ulmi (Dumas et al. 1983, 1986 Jeng et al. 1983). Procter and Smalley (1988) also observed increased mansonone accumulation in elm inoculated with O. ulmi strains. Wu et al. (1989) demonstrated the toxic effect of these chemicals on the physiology and ultra- structure of the fungus. Mansonones were first reported to accumulate in elms infected with O. ulmi by Elgersma and Overeem (1971). However, these authors were unable to correlate mansonone accumulation with resistance to DED. There are several reasons why these authors overlooked the correlation. For example they compared mansonone content between treatments on the basis of number of cuttings that were extracted rather than using a more precise unit of comparison such as dry or fresh weight. Smalley et al. (1993) and Procter et al. (1994), using a number of chemically induced mutants showing lower mansonone tolerance than the parent strains, point out that mansonones alone do not play a major role in the resistance of elms to DED. These authors could not correlate mansonone sensitivity of a number of DED fungal mutants with high virulence. This is not surprising since chemically induced mutants often are altered at many more loci (position that a gene occupies in a chromosome) than those tested and visible. Therefore correct interpretation of the results is very difficult without knowing all the affected loci and their genetic stability.
Nevertheless, mansonone production is a very sensitive and precisely measurable process implicated in the host’s reaction in response to pathogen invasion. It is definitely a part of genetically programmed sequences of host defense mechanisms in DED. Duchesne (1993) concluded that timing of expression of different mechanisms of resistance to DED is critical for both anatomical and chemical means of defense to be effective in localizing the pathogen. He bases his assumption on the faster accumulation of mansonones in U. pumila (Duchesne et al. 1985), the faster mansonone accumulation in U. americana inoculated with aggressive isolates, and finally on the faster barrier zone formation (Shigo and Tippet 1981) in non-host trees than in host trees inoculated with O. ulmi (Rioux and Ouellette 1991a, b). To isolate the mansonone-inducing factor of the DED fungus, a sensitive bioassay had to be developed. Szczegola-Derkacz (1988) showed that tissue cultures responded to O. ulmi inoculations with mansonone
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production. Autoclaved spores of the yeast phase of the DED fungus produced the same effect as living spores indicating that the compounds triggering mansonone production are heat stable. Yang et al. (1989) demonstrated that fungal culture filtrates, cytoplasm and cell walls of O. ulmi contain molecules that elicit mansonone accumulation in elm calli. The culture filtrate elicitor has been purified (Yang 1991) and its structure identified (Hubbes et al. unpublished results).
When elm seedlings and elm trees (10 cm in diameter) were first injected with the elicitor and then challenged with 8,000 to 1 million spores of an aggressive strain per tree, the treated trees showed significant difference in wilting when compared to the control. The 5-year old seedlings obtained the high spore dose, while the trees obtained the lower dose (unpublished results). A United States patent application based on the structure of the elicitor for the control of DED has been filed. The elicitor can be injected in liquid form or in pellet form into the tree. It is heat stable, has an indefinite shelf life, appears environmentally safe and easy to administer into the tree, particularly in pellet form. Field trials on the feasibility of pellet treatment as well as elicitor activity have been conducted in 1997 by a number of cities in Manitoba, Saskatchewan and Alberta. Field trials on the efficacy of the elicitor are presently being repeated in Ontario, Saskatchewan and Alberta. Investigations in our Forest Pathology laboratory on the mechanisms of induced resistance show that they follow similar complex defense reactions as those found in agricultural crops (Somssich and Hahlbrock 1998). The elicitor induces a chain of defense reactions that prevent the rapid spread of the fungus. However the difference between agricultural crops and elm trees is that elm trees are wild type individuals with greater genetic variability and therefore show greater variations in their defense reactions. Hence, control of fungal pathogens in trees by induced resistance is a new approach of disease control and appears to be one of the few remaining options to protect the existing elm populations in our communities against DED.
Since the first appearance of DED a nagging question has emerged over and over: “Is the elm tree worth saving, and will this tree follow the doomed fate of the North American sweet chestnut? The chestnut has lost its once vast territories and other tree species have taken its place. Why then worry about losing another native tree species?” The very emotional argument against such a statement is that although the North American continent is rich in number, variety and magnificence of native trees, no tree can replace the American elm in the hearts of the people. The argument goes further in that the elm typifies, as no other tree does, the finest things in North American life. No substitute greenery, however luxurious, could hide the scars that would be left by the loss of the elm in our cities.
Acknowledgements
Part of our work has been supported by NSERC, City of Winnipeg, Province of Manitoba, Province of Saskatchewan, Coalition to Save the Elms, University of http://www.elmcare.com/community/research/hubbes1.htm (10 of 22) [2/27/02 10:33:01 PM] Elmcare.com - Hubbes 1
Toronto. Many thanks also to Mike Allen, Chief Forester of the City of Winnipeg, for reviewing the manuscript.
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Smalley, E.B., K.F. Raffa, R.H. Proctor and K.D. Klepzig. 1993. Tree responses to infection by species of Ophiostoma and Ceratocystis. p. 207- 218. In: Ceratocystis and Ophiostoma, Taxonomy, ecology, and pathogenicity (Eds. M.J. Wingfield, K.A. Seifert and J.F. Webber). APS, St. Paul, Minnesota.
Somssich, I.E. and K. Hahlbrock. 1998. Pathogen defence in plants - a paradigm of biological complexity. Trends Plant Sci. 3(3):86-90.
Stennes, M.A. and D.W. French. 1987. Distribution and retention of thiabendazoic hypophosphite and carbendazim phosphate injected into mature American elms. Phytopath. 77:707-712.
Sticklen, M.B., M.G. Bolyard, R.K. Hajela and L.C. Duchesne. 1991. Molecular and cellular aspects of Dutch elm disease. Phytoprotection 72:1-13.
Stipes R.J. and R.J. Campana. 1981. Compendium of elm disease. Amer. Phytopathol. Soc., St. Paul. MN.
Strobel, G.A. and D. Myers. 1982. Bacterial antagonism as a strategy for the treatment of Dutch elm disease. p. 46•61. In: Proceedings of the Dutch elm disease symposium and workshop, Winnipeg, Manitoba, October 5•9, 1981 (Eds. E.S. Kondo, Y. Hiratsuka and W.B.G. Denyer). Manitoba Department of Natural Resources, Manitoba, Canada.
Sutherland, M.L. and C.M. Brasier. 1997. A comparison of thirteen d-factors as potential biological control agents of Ophiostoma novo-ulmi. Plant Pathol. 46:680-693.
Sutherland , M.L., L. Mittempergher and C.M. Brasier. 1995. Control of Dutch elm disease by induced host resistance. Eur. J. For. Path. 25:307-318.
Szczegola-Derkacz, M. 1988. Induction of mansonones by Ophiostoma ulmi in tissue cultures of Ulmus americana and Ulmus pumila. M.Sc.F. thesis, Department of Forestry, University of Toronto.
Takai, S. 1980. Relationship of the production of the toxin, cerato•ulmin, to synnemata formation, pathogenicity, mycelial habit, and growth of Ceratocystis ulmi isolates. Can. J. Bot. 58: 658•662.
Tegli, S. and A. Scala. 1996. Isolation and characterization of non-cerato-ulmin producing laboratory induced mutants of Ophiostoma novo-ulmi. Mycol. Res. 100(6):661-668.
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Temple, B.O. 1997. The biological role of the hydrophobin cerato-ulmin in the life history of Ophiostoma ulmi and O. novo-ulmi. M.Sc.F. thesis, Department of Botany, University of Toronto. 133 pp.
Tomalak. M., H.E. Welch and T.D. Galloway. 1989. Nematode parasites of bark beetles (Scolytidae) in southern Manitoba, with descriptions of three new species of Sulphuretylenchus Rühm (Nematoda: Allantonematidae). Can. J. Zool. 67:2497- 2505.
Townsend, A.M.and F.S. Santamour, Jr. 1993. Progress in the development of disease-resistant elms. p. 46-50. In: Dutch elm disease research: Cellular and molecular approaches (Eds. M.B. Sticklen and J.L. Sherald). Springer-Verlag New York, Inc.
Ware, G. and F. Miller. 1997. Developing better elms. American Nurseryman August 15, 1997:44-51.
Webber, J.F. 1987. Influence of the d2 factor on survival and infection by the Dutch elm disease pathogen Ophiostoma ulmi. Plant Path. 36:531-538.
Webber, J.F. 1990. Relative effectiveness of Scolytus scolytus, S. multistriatus and S. kirschi as vectors of Dutch elm disease. Eur. J. For. Pathol. 20:184-192.
Webber, J.F. 1993. D factors and their potential for the control of Dutch elm disease. p. 322-332. In: Dutch elm disease research: Cellular and molecular approaches (Eds. M.B. Sticklen and J.L. Sherald). Springer-Verlag New York, Inc.
Westwood, A.R. 1991. A cost between analysis of Manitoba’s integrated Dutch elm disease management program 1975-1990. Proc. Entomol. Soc. Manitoba 47:44-59.
White, J.C. 1982. An industrial approach to biological control of Dutch elm disease. p. 71•77. In: Proceedings of the Dutch elm disease symposium and workshop, Winnipeg, Manitoba, October 5•9, 1981 (Eds. E.S. Kondo, Y. Hiratsuka and W.B.G. Denyer). Manitoba Department of Natural Resources, Manitoba, Canada.
Wu, W.D., R.S. Jeng and M. Hubbes. 1989. Toxic effect of elm phytoalexin mansonones on Ophiostoma ulmi, the causal agent of Dutch elm disease. Europ. J. For. Path. 19:343-357.
Yaguchi, M., M. Pusztai-Carey, C. Roy, W.K. Surewicz, P.R. Carey, K.J. Stevenson, W.C. Richards and S. Takai. 1993. Amino acid sequence and http://www.elmcare.com/community/research/hubbes1.htm (21 of 22) [2/27/02 10:33:01 PM] Elmcare.com - Hubbes 1
spectroscopic studies of Dutch elm disease toxin, cerato-ulmin. p. 152-170. In: Dutch elm disease research: Cellular and molecular approaches (Eds. M.B. Sticklen and J.L. Sherald). Springer-Verlag New York, Inc.
Yang, D. 1991. Isolation, identification and characterization of phytoalexin elicitors from Ophiostoma ulmi. Ph.D. thesis, Department of Forestry, University of Toronto.
Yang, D., R.S. Jeng and M. Hubbes. 1989. Mansonone accumulation in elm callus induced by elicitors of Ophiostoma ulmi, and general properties of elicitors. Can. J. Bot. 67:3490-3497.
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Home > About Elms > Elm Species > American Elm Last Update 30/08/00 American Elm Ulmus americana L. How Trees Work
Height 35m (115')
About Elm Trees Leaves 10-15cm (4-6")
The Elm Story Identifying Elms Elm Species Biology of Elms
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The American or White elm is the largest species of elm. Due to its graceful form and size, it was an extremely popular urban tree before the spread of Dutch elm disease. Once found mostly in eastern North America, remaining populations of mature American elms are concentrated in the American Midwest and Canadian Prairies.
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Home > About Elms > Elm Species > Rock Elm Last Update 30/08/00 Rock Elm Ulmus thomasii Sarg. How Trees Work
Height 25m (80 feet)
About Elm Trees Leaves 5-10cm (2-4 inches)
The Elm Story Identifying Elms Elm Species Biology of Elms
Caring for Your Elm Elm Tree Diseases This elm species, also known as the cork elm due to corky ridges on branches, is probably the least typical in form. Rather than branching out into large co- Elm Tree Links dominant limbs, the trunk remains distinct almost to the top of the tree. The crown Quick Elm Facts is cylindrical in shape and can grow to approximately 25m in height. A relatively rare tree, it occurs mainly in the US Midwest. The leaves are 5-10 cm long and hairy on the underside.
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Home > About Elms > Elm Species > Slippery Elm Last Update 30/08/00 Slippery Elm
Ulmus rubra Muehl. How Trees Work
Height 40m (132')
About Elm Trees Leaves 15-20cm (6-8") The Elm Story Identifying Elms Elm Species Biology of Elms The Slippery or Red elm is rather uncommon and lives mainly in the eastern half of Caring for Your Elm the US and southern Ontario and Quebec. The crown is umbrella-shaped with a Elm Tree Diseases high canopy and the leaves are quite rough to the touch. Elm Tree Links Quick Elm Facts Slippery elm is vulnerable to many of the same of the diseases as American elm including Dutch elm disease and, as a result, rarely reach full maturity.
This tree has also been an important component of herbal medicine for more than a century. Native Americans and early settlers used the dried inner portion of the bark to soothe irritated stomachs and to heal wounds.
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Ulmus glabra Huds. How Trees Work
Height 40m (132')
About Elm Trees Leaves 8-16cm (3-6") The Elm Story Identifying Elms Elm Species Biology of Elms Also known as Wych elm, these trees are native to Europe and western Asia and Caring for Your Elm common in North and West Britain and Ireland. Similar to the Slippery elm, this Elm Tree Diseases tree is often planted in urban centers in eastern North America. Often growing to a Elm Tree Links height of 40m, 500 year-old specimens are known to exist. Quick Elm Facts If you are worried about Dutch elm disease, click here.
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Ulmus glabra camperdownii How Trees Work
Height 3-5 m (10-15 feet)
About Elm Trees Leaves 8-18 cm (3-7 inches) The Elm Story Identifying Elms Elm Species Biology of Elms Also known as the Umbrella Elm or Weeping elm, this tree originated from a Caring for Your Elm seedling at Camperdown House, near Dundee Scotland. It is in fact a cultivar of Elm Tree Diseases the Scotch elm. Elm Tree Links Quick Elm Facts The leaves show a high degree of asymmetry at the base and are dark green in colour. The drooping branches have made it attractive as a small-scale landscape tree.
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http://www.elmcare.com/images/camperdown.jpg [2/27/02 10:33:23 PM] Elmcare.com - Siberian Elm
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Home > About Elms > Elm Species > Siberian Elm Last Update 30/08/00 Siberian Elm
Ulmus pumila L. How Trees Work Height 40m (132 feet)
Leaves 2-7cm (1-3 inches) About Elm Trees
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Copyright © APS (www.scisoc.org) Caring for Your Elm Elm Tree Diseases Elm Tree Links This medium-sized tree is native to northeastern Asia, but has been extensively planted in cities across North America – especially in the West. This is due to the Quick Elm Facts Siberian elm’s resistance to Dutch elm disease and other pathogens.
The Siberian is extremely drought resistant. In grows at altitudes of up to 3900m in Tibet and once grew in the Gobi desert. After the drought of the 1930’s in the US Midwest, Siberian elms were planted extensively and became the most widely planted shelterbelt tree in North America. It is now found in places as distant as the USSR and Argentina where arid land came under cultivation.
Thriving on moist soils, this hardy tree can flourish in adverse conditions. Leaves are narrow and between 2 and 7 cm long. Unlike other elm species, the leaves are almost symmetrical at the base. The bark is gray and rough.
Many arborists consider the Siberian elm an undesirable street tree due to its weak wood and prolific seeding.
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Ulmus procera Salis. How Trees Work
Height 40m (132 feet)
About Elm Trees Leaves 8-16cm (3-6 inches) The Elm Story Identifying Elms Copyright © APS Elm Species (www.scisoc.org) Biology of Elms
th th Caring for Your Elm This elm was relatively rare until the 17 and 18 centuries when it was planted extensively by landowners along hedges that surrounded farmland. The leaves Elm Tree Diseases are 6-9 cm long with a rough upper surface, and hairy underside. Elm Tree Links Quick Elm Facts Selected for their shade cover, genetic variation was reduced making the species especially vulnerable to Dutch elm disease. After the disease reached Britain in 1967, more than 12 million English elms perished. Mature English elms can grow to 36m and have narrow crowns.
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Zelkova serrata Thunb. Mak. How Trees Work
Height 15-20 m (50-60 feet)
About Elm Trees Leaves 3-5cm (1-2 inches)
The Elm Story Identifying Elms Elm Species Biology of Elms
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Native to Japan, this medium-sized tree has the vase-shaped form typical of American elms. Its tolerance of Dutch elm disease has made it a popular choice to replace disease-stricken populations. It flourishes in almost any good soil preferring a deep, well-drained moist loam.
Fast-growing, its leaves are slender and 3-5 cm long with 8-14 veins per side ending in a single sharp tooth.
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Home > About Elms > Elm Species > Winged Elm Last Update 30/08/00 Winged Elm
Ulmus alata How Trees Work
Height 10-12 m (40-50 feet)
About Elm Trees Leaves 4-8 cm (1.5 to 3 inches) The Elm Story Identifying Elms Elm Species Biology of Elms
A small to medium-sized tree native to the southeastern U.S. Caring for Your Elm Elm Tree Diseases The bark is flat with scaly ridges separated by shallow, irregular furrows. Elm Tree Links Quick Elm Facts If you are worried about Dutch elm disease, click here.
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Home > About Elms > Elm Species > Chinese Elm Last Update 30/08/00 Chinese Elm
Ulmus parvifolia How Trees Work
Height 6-18 m (20-60 feet)
About Elm Trees Leaves 2-7 cm (0.8 to 2.5 inches) The Elm Story Identifying Elms Elm Species
Biology of Elms
Native to northern China, Japan, and Korea, the Chinese or Lacebark elm Caring for Your Elm generally has a broad, vase-like shape with pendulous branches. In warmer Elm Tree Diseases regions, it may be evergreen. The bark is usually smooth. It grows fairly quickly Elm Tree Links and is resistant to Dutch elm disease making it a popular choice for landscaping. Quick Elm Facts If you are worried about Dutch elm disease, click here.
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http://www.elmcare.com/images/chinese.jpg [2/27/02 10:33:37 PM] Elms in Winnipeg - Part 1
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Home > Elms in Winnipeg March 2000 - Part 1 Last Update 30/08/00
Part 1 Part 2 Part 3 Part 4 How Trees Work About Elm Trees olseley Avenue wanders through a gentrified Winnipeg Caring for Your Elm neighbourhood on the north side of the Assiniboine River, Elm Tree Diseases its 2.5 kilometres of sidewalk dappled by light that filters through a canopy of American elms. Elm Tree Links Quick Elm Facts Sometimes the shady street follows the meandering course of the muddy brown river; at other times, like Portage Avenue just to the north, it obeys the dictates of traffic engineers and straightens out. But whether straight or curvaceous, it is always lined with grand, old, century elms. Hundreds of them.
Back in the 1950s, when Winnipeggers began their passionate affair with the automobile, if you wanted to avoid busy Portage Avenue on your way downtown or if you lived in the south end and were on your way to see a Blue Bombers game at the new Winnipeg Stadium, Wolseley was a fast alternate route with no bothersome traffic lights or stop signs. It did, however, have an old tree growing smack-dab in the middle of the road near the corner of Basswood Place. The ancient Wolseley elm, according to local lore, was planted in 1859 by a girl named Mary Anne Good who lived on a prairie farm near the bank of the Assiniboine. Nearly 100 years later, by some road-planning oversight, it was still there, although surrounded by a curb and a fringe of grass that Ripley's Believe It Or Not declared was "the smallest park in the world." Motorists, however, were not amused, and city officials worried that someone might drive into it and kill themselves. Neighbourhood residents argued that the tree protected their kids from being killed by speeding cars.
In September 1957, at the height of the football season, the city assigned a crew to remove the offending elm. In the ensuing standoff, a dozen neighbourhood women circled the tree, arm in arm, to fend off the buzz saws, and within minutes the police had arrived, paddy wagons and all. A crowd gathered.
"If they want to chop down this tree," said one of the women, "they're going to have to chop us down first."
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In the end, the matter was settled peaceably by newly-elected mayor Stephen Juba, who pulled up in his Cadillac and sent the workers home. Most of the rest of the neighbourhood's trees have also survived, somehow evading both the urban- planners' axe and the more serious threat of Dutch Elm Disease. In fact, the city remains shaded by a forest comprised of over 200,000 elms, a remarkable legacy that is guarded by Winnipeggers every bit as vigilant as the defenders of the Wolseley Elm. Their appreciation of the urban forest, and their decades-long battle against a disease that has virtually extirpated the elm from the streets of most other cities, is now finally offering some hope for those who might otherwise have given up on what was once eastern North America's most popular city tree. At the turn of the century, when the grain and railroad boom was fuelling Winnipeg's growth, the city fathers looked south for inspiration and were, perhaps inevitably, inspired by Chicago, a city with a similar economy, monumental architecture, grand streets, and lots of elm trees. By then, much of eastern North America had been cleared of forest, and city dwellers were starting to rethink the value of trees. Arbour Day had become fashionable, and tree planters had only to look to adjacent farmsteads, where the stubborn Ulmus americana, a very tough tree for settlers to remove, still proliferated. The giant American elms that survived the agricultural clearances and thrived on prime farmland became the source of the graceful, parasol-shaped trees that would dominate the urban forests of North America for decades to come.
Part 1 Part 2 Part 3 Part 4
Jamie Swift is a writer and broadcaster living in Kingston, Ontario. His most recent book, Wheel of Fortune, was published in 1995. He is also the author of Cut and Run, a lament for the mismanagement of Canadian forests.
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http://www.elmcare.com/features/mar01-1.htm (2 of 2) [2/27/02 10:33:42 PM] Elms in Winnipeg - Part 2
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Home > Elms in Winnipeg March 2000 - Part 2 Last Update 30/08/00
How Trees Work Part 1 Part 2 Part 3 Part 4 About Elm Trees Caring for Your Elm Winnipeg's early planners had a perfect source of planting stock at hand. When the time came to bring trees into the Elm Tree Diseases newly laid-out subdivisions on both sides of the Assiniboine Elm Tree Links and Red rivers, they simply collected native elms from the riverbanks. Each new city park featured a nursery where the Quick Elm Facts trees were grown to sapling size before being transplanted along the generous boulevards. The city charged each homeowner a lot levy and planted an elm in front of every residence, and Winnipeg's splendid urban forest was born. It's a democratic forest, lining not just the tonier streets of southern neighbourhoods but also offering shade and comfort to people in Winnipeg's storied north end, where successive waves of poor immigrants-most recently aboriginal people from reserves-have settled in the rundown streets around Selkirk Avenue.
"Our forest is unique in the world," enthuses chief forester Mike Allen as he surveys the elms that shade Palmerston Avenue in the Wolseley district. "There's no other city anywhere with this incredible natural arch of trees." A tall, thoughtful man with the image of a tree etched on his brass belt buckle, Allen grew up in Toronto at a time when the dreaded Dutch elm disease was obliterating the elm from the city's parks and lawns. "When I was eight," he says, "I noticed workers removing one giant after another along my route to school, and whenever I travelled around southern Ontario, I witnessed the death of elms standing like weird witch's broomsticks." He has vowed not to let that happen in Winnipeg. He points to a four-storey elm and describes the multipronged fight he has waged against Dutch elm disease, explaining that the trees' rough and diverse origins on the banks of the Assiniboine were the key to their survival. "They're not high-tech clones cultivated for certain desirable traits," he says. "They were selected purely from native stock, so they had tremendous genetic diversity even though they were all one species. Today, I can show you elm from all over Winnipeg, all American elm, but you might look at one and say, "That's not the bark of an American elm.' " As we tour the city's forest, it becomes clear that most Winnipeg elms have the elm's characteristic bark, deeply furrowed and light grey, like a heavy grade of rough corduroy. Some, however, have no fissures or ridges, and the bark is dark or tinged with brown. Sometimes the leaves are enormous; sometimes they're
http://www.elmcare.com/features/mar01-2.htm (1 of 3) [2/27/02 10:33:44 PM] Elms in Winnipeg - Part 2
small. Some leaves have sawtooth edges and grow in double rows; sometimes the edges are wavy and the rows are triple. Such variation makes for a more resilient species, because certain variants seem to have an inherent resistance to Dutch elm disease. Not all of them, however. Five years ago, in the biggest single elm infection that Winnipeg has witnessed, the disease destroyed 20 mature elms at Palmerston and Ethelbert. The memory still makes Mike Allen shudder. But the resilient variants survived the infestation, and their genetic material may help save the species.
Dutch elm disease, so named because it was first identified in the Netherlands in 1917 or 1918, likely originated in Asia. It's an infection of the deadly fungus Ophiostoma ulmi, which enters and disrupts the tree's vascular system literally on the back of the elm bark beetle, Hylurgopinus rufipes. The scourge reached the United States in 1930, with the first Canadian outbreak reported in Sorel, Quebec, in 1945. Within a few years, more than 600,000 elms in Quebec had been wiped out. Toronto's population of 35,000 elms was quickly reduced by 80 percent. According to the University of Toronto's Martin Hubbes, a leading Dutch elm disease researcher, "one of the largest mass destructions of trees ever witnessed" accelerated when the Canadian and American disease fronts merged and began to migrate westward, travelling up the Red River from South Dakota into southern Manitoba in the early 1960s, most likely brought in by campers hauling infected firewood. The disease was reported in Winnipeg in 1975 and by 1990 was infecting elms in Saskatchewan. This year, it arrived in Alberta. Today, possession of elm firewood-infected or not-can bring a $5,000 fine in Winnipeg, where they take the threat seriously. Since the disease's arrival, some 34 percent of city elms have been infected and cut down.
It's a paradoxical story, at least as far as Winnipeg is concerned. The same riverbank forests that provided the city with its rich genetic diversity now offer an ideal host for Dutch elm disease. Because the Assiniboine, La Salle, and Seine rivers empty into the Red near Winnipeg, their rich silt valleys provide both a breeding ground and a highway for the elm beetle. The province has earmarked and sporadically protected a buffer zone surrounding Winnipeg. This is a crucial battlefield in the war to save the city's cherished elms. The idea is to remove infected trees from this zone in an attempt to protect the city proper. Other western cities that depend on the elm for shade, shelter, and beauty are luckier because they are more like isolated islands in the prairie, with little contiguous elm forest.
Another paradox. Despite the devastation of the urban elm forests of Toronto and Montreal, those central Canadian cities are well situated to bounce back. Their relatively moderate climates can support a wide variety of trees, from the colourful red maple to the elegant black walnut. Winnipeg's famously frigid winters mean that few species can thrive there. The American elm, one of the hardiest, is ideal. Not only sublimely beautiful, it's tough enough to resist road salt and devastating cold. What's more, Winnipeg's harsh winters have little appeal for the European elm bark beetle, Scolytus multistriatus, a larger, hairier critter that's a perfect host for the toxic fungus. As long as Winnipeg has only the native prairie variety, its elms have a fighting chance. Yet Mike Allen remains cautious. http://www.elmcare.com/features/mar01-2.htm (2 of 3) [2/27/02 10:33:44 PM] Elms in Winnipeg - Part 2
"Insects are highly versatile and opportunistic," he warns. "It may well only be a matter of time before we get European beetles reproducing themselves and becoming hardy enough to invade Manitoba."
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Jamie Swift is a writer and broadcaster living in Kingston, Ontario. His most recent book, Wheel of Fortune, was published in 1995. He is also the author of Cut and Run, a lament for the mismanagement of Canadian forests.
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http://www.elmcare.com/features/mar01-2.htm (3 of 3) [2/27/02 10:33:44 PM] Elms in Winnipeg - Part 3
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How Trees Work Part 1 Part 2 Part 3 Part 4 About Elm Trees Caring for Your Elm The past 20 years have witnessed widespread conflicts over ancient trees and old-growth forests. A familiar snapshot: Elm Tree Diseases Environmentalists cry foul, claiming the wilderness is being Elm Tree Links strip-mined. Loggers and millworkers cry foul, claiming their jobs are being jeopardized by a Birkenstock brigade of Quick Elm Facts outsiders who return to comfortable condos once the camera crews depart. The conflict is, in a very real way, about a sense of place. Many environmentalists plead for places they cherish. That place, however, is often somewhere else: the boreal forest, the Pacific rainforest, the wilderness. For many Canadians, nature is, indeed, something out there in cottage country, a wilderness park, a summer camp-a rural landscape, not a city streetscape.
When Mary Anne Good planted the Wolseley elm, most Manitobans were sod- busting settlers. Twenty years later, when landscape architect Frederick Law Olmsted urged Montrealers to make their new park on Mount Royal a naturalistic retreat ("You can put in a broad dark mass of low mountain pine, or pensive, feathery and brooding hemlock . . . to supply the degree of canopy and shadow which will be the most effective for your purpose"), Quebecers were still by and large country folk. We're about to enter the planet's first truly urban century: a majority of the world's people now live in cities, and although Canadians may visit a wilderness place from time to time, we pass our daily lives in the shadow of an urban forest.
Urban forest may sound like a contradiction in terms, but not to Judy Werier, the peppy director of Winnipeg's Coalition to Save the Elms. As we drive around trendy Osborne Village to check out the condition of its trees, she hits the brakes and jumps out of her car to rip a yard-sale sign off a sidewalk elm.
"Can you believe this?" she fumes, hurling the offending poster into the back seat. "It was nailed to the tree! Someone actually used four nails!" Jamming the car into gear, she mutters something about going over to the yard
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sale on Saturday to scold the culprit. She explains that nails provide another way into the tree for the elm bark beetle and wood-boring beetles and hence for the fungus that causes Dutch elm disease. Heading along River Avenue, she has trouble keeping her eyes on the road as she points out the cankerworm bands that residents have dutifully wrapped around their neighbourhood trees, scolds construction foremen for neglecting to strap protective lumber around trees on building sites, and of course, keeps an eye out for the telltale flagging that indicates an elm has been infected.
Citizen involvement has been crucial to Winnipeg's efforts to preserve the elm forest. Coalition members report "hazard" elms to Mike Allen's department, where every summer forestry staff adopt a war-room approach, sticking hundreds of red and black pins onto a map as they chart sightings of the disease. There are lots of pins along the rivers. The city uses an expensive fungicide injection system on valuable park trees, while a less expensive basal spraying technique is aimed at zapping beetles with an insecticide containing chlorpyrifos. This prevents the beetles from overwintering in the tree but must be done annually. The principal defence, however, is sanitation, which includes tree removal and pruning of dead branches: some diseased trees can be saved by fungicidal injection, but many are simply cut down. It's a $2 million-a-year battle, but Werier thinks it's worth it. Aside from organizing workshops on tree planting, identification, pruning, and Dutch elm disease, the coalition helped pressure the province into restoring some of the $3 million it had cut from the program to control the spread of the disease in the buffer zone around the city.
"My husband calls me 'a crazy militant little person,' " she says as we head out Portage Avenue. When I ask her about her commitment to the urban forest, why she's such a tree zealot, she responds in the same way a wilderness tree hugger might. "I love the trees," she says after a moment's thought. "That's all I can say. There are no words I can put to it. It's emotional."
Werier got an early start in urban forestry. Her father, Val Werier, a longtime Winnipeg newspaper columnist who recently won the Order of Canada for his advocacy work, used to quiz her about trees, teaching her to tell an ash from an elm. "When Dad came home from work, we'd go for a brisk walk. I'd have to run to keep up with him, but he taught me about trees, and I developed a real appreciation for them. So when I became involved with the elms, I said to myself, 'This feels right.' "
In 1969, Val Werier was pushing for a bylaw to control the removal of trees on public land. Three years later, he was telling his readers to get out and put sticky bands on elms to protect them from cankerworms. And in 1974, the year before Dutch elm disease was first identified in Winnipeg, he wrote a long series of columns on the imminent threat. By 1976, he was writing that government action wasn't enough-Winnipeggers had to get involved in the fight against the disease. Werier was soon able to point out that Manitoba was the first North American
http://www.elmcare.com/features/mar01-3.htm (2 of 3) [2/27/02 10:33:47 PM] Elms in Winnipeg - Part 3
jurisdiction to require the removal of diseased elms from private and public property.
"There's a history of citizen activism here," Mayor Glen Murray told me when I asked him about Werier. "And a very practical reason is that the absence of the elms would have a huge negative impact on property values and the enjoyability and livability of neighbourhoods."
A city forest has a long list of virtues. Urban air, full of carbon dioxide and a host of noxious car fumes, is measurably improved in cities where a dense overstorey of trees adds life-giving oxygen. The forest moderates storm runoff. A deciduous forest protects houses from the summer heat, saving on air-conditioning costs while permitting passive solar gain in wintertime. If it's dense enough-as it is in Winnipeg-it acts as a winter windbreak. It also buffers the ceaseless white noise of city traffic. Parents can take comfort that shaded play areas are safe in an era when high-ultraviolet sunlight is cause for concern. Realtors know that a treelined street is a price-boosting part of their "location, location" mantra.
Though she has a passionate attachment to the urban forest, Werier inherited a lobbyist's understanding of how to protect it. She knows that she can't just rely on the virtues of nature appreciation when it comes to navigating the political terrain at city hall. A savvy politician, Glen Murray is well aware that Stephen Juba, Winnipeg's longest-serving mayor, made an early and lasting impression when he defended the Wolseley elm in 1957. "If you ever want to lose elected office in Winnipeg," says the mayor wryly, "say something bad about a tree."
Of course, all the political will in the world will not stop the steady onslaught of Ophiostoma ulmi. That's why Winnipeg, prodded by Werier and the Coalition to Save the Elms, has been sending cheques to the Faculty of Forestry at the University of Toronto, where Martin Hubbes and his research team have recently developed a vaccine that immunizes the elm against the fungus. With patents on the way, Canadian scientists have helped spark renewed international interest in a problem that many had given up as a lost cause.
Part 1 Part 2 Part 3 Part 4
Jamie Swift is a writer and broadcaster living in Kingston, Ontario. His most recent book, Wheel of Fortune, was published in 1995. He is also the author of Cut and Run, a lament for the mismanagement of Canadian forests.
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http://www.elmcare.com/features/mar01-3.htm (3 of 3) [2/27/02 10:33:47 PM] Elms in Winnipeg - Part 4
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Home > Elms in Winnipeg March 2000 - Part 4 Last Update 30/08/00
How Trees Work Part 1 Part 2 Part 3 Part 4 About Elm Trees Caring for Your Elm Hubbes began studying Dutch elm disease in 1968 and quickly became fascinated by the many ways trees react to the Elm Tree Diseases threat of infection. When bark beetles laden with fungal spores Elm Tree Links burrow their way under the craggy bark of an elm, the tree responds to the invasion with what Hubbes describes as a Quick Elm Facts "cascade of defensive reactions," including the production of compounds called mansonones that help ward off fungal infestation. He and his colleagues have succeeded in isolating from the fungus a glycoprotein "elicitor" that tricks the tree into mounting its protective cascade.
"What the tree tries to do," explains Hubbes, "is to wall the fungus off in a confined space so that it cannot further invade the vascular system. The trees actually shut down the cell walls and surround the fungus with an inert tissue so that the fungus cannot penetrate the tree further."
Once the defences are elicited and the fungus is isolated, the host tree is then primed with antifungal mansonones (related to a group of substances called sesquiterpine quinones) that destroy the fungus. "They kill by attacking mitochondria, the energy powerhouses of the fungus," Hubbes told New Scientist magazine last year after news of the discoveries began to filter out. Since then, there's been a surge of international attention. "It was incredible how a much renewed interest flared up around the world," Hubbes says now in his Toronto lab. A plant pathologist who seems torn between modesty ("We didn't want a lot of propaganda because we like to work in a quiet atmosphere") and bubbling enthusiasm for saving trees, he can't help letting the enthusiasm surface. "We're getting inquiries from all over the world," he says, "the U.S., Australia, New Zealand, Europe." Everyone, its seems, wants their elms back.
Hubbes and his colleagues are busy conducting field tests in Winnipeg, Toronto, and several other places in Ontario, treating trees with the elicitor and then exposing them to high dosages of Ophiostoma ulmi spores "to see how good the stuff is." They have also begun to treat elms in Saskatchewan and Alberta but
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have carefully avoided introducing any fungus to vulnerable stands of elms there. Results are already encouraging. In one trial, all the trees in the control group died when exposed to the fungus, whereas only one in 33 vaccinated trees succumbed.
Hubbes agrees that Winnipeg has a natural advantage because of its genetically diverse elm population. But here again, Canada's richest urban elm forest presents paradoxical problems inherent in any effort to intervene with a complex ecological system.
"For our treatment, wide diversity within the species is not so good," Hubbes says. "If I could just treat clones of a single variant, it would be so much easier for me because one cloned tree would react the same as a thousand others. But where there's high diversity, some trees do very well, while others require more conditioning."
Another variable is the influence of the tree's environment. A handsome old elm standing alone on a rural fence row may survive because it's being nourished by good agricultural soils. "When you plant them in a city where you have a dreadful environment," says Hubbes, "they might not react the same way. That's why we have to understand the defence mechanisms. Once we do that, then I think we'll have solved the problem."
Hubbes admits that even after 30 years of study, there's still much to learn about the immune systems of Ulmus americana, particularly in a forest ecology as complex as that of Winnipeg. But he is in no doubt about the prairie city's role in sustaining the work that finally seems to be bearing fruit. "If Winnipeg hadn't supported us," he says, "I would have given up a long time ago." Most people, including Ottawa politicians and officials who have stopped supporting Dutch elm disease research, still hear the word elm and immediately think of those skeletal remains that dot the rural landscape in eastern Canada. Hubbes keeps getting advice from people who say, "The elm? Don't bother. It's dead, forget about it."
But it's not dead in Winnipeg. "I grew up in Montreal when all of the elms died and the city didn't act to save them," recalls Glen Murray. "I remember very vividly the trees disappearing in my neighbourhood. Here in Winnipeg, people have a real attachment to the trees. It's part of our identity as a city." And thanks to officials like Mike Allen and citizen activists like Judy Werier, tree huggers whose stubbornness was perhaps inherited from the women in the cloth coats who defended the Wolseley elm, eastern cities may one day rejoice again under their own restorative canopies of stately elms.
Part 1 Part 2 Part 3 Part 4
Jamie Swift is a writer and broadcaster living in Kingston, Ontario. His most recent book, Wheel of http://www.elmcare.com/features/mar01-4.htm (2 of 3) [2/27/02 10:33:49 PM] Elms in Winnipeg - Part 4
Fortune, was published in 1995. He is also the author of Cut and Run, a lament for the mismanagement of Canadian forests.
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http://www.elmcare.com/features/mar01-4.htm (3 of 3) [2/27/02 10:33:49 PM]