Traditionally, people have tried to control Dutch Elm Disease by stopping it from spreading. Many communities, like the City of Winnipeg, have adopted a highly co-ordinated program to try to save their elms.

Surveillance
Detection is the first step. The earlier the disease can be caught, the quicker it can be stopped.  
Some communities and government agencies have designated experts to help make a definitive diagnosis. Contact these experts at the first suspicion of DED. Early detection can help prevent infection of nearby trees.

Disposal
Dead wood is an ideal breeding ground for the elm bark beetle. Dead wood must be properly removed and destroyed.

Firewood spreads the disease. Storing elm firewood is illegal in many jurisdictions with active DED control programs.

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. 

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. 

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.  

Top