By: Alicia Mah, Dutch Elm Disease Technician
Dutch elm disease (DED) is caused by Ophiostoma novo-ulmi, a fungal pathogen that is most often spread by the elm bark beetle. The fungus produces spores that adhere to the beetle during breeding. When the beetle feeds and overwinters in elm trees, the pathogenic fungus is allowed to spread.
Fungal infection interferes with the tree’s ability to deliver water from the roots to the rest of the tree. Since water is needed for the tree to generate energy (photosynthesis), decreased water transport results in gradual decline and death of the tree. This produces the characteristic symptoms of DED, including a yellowing or browning, wilting and curling of leaves.
If you suspect that your elm tree has DED, samples can be sent to the Crop Protection Laboratory for testing from June 1 to September 30. The guidelines below can be used to submit samples that accurately reflect the health of your tree.
How to Take a Good Sample
- Examine the elm tree. Look for yellow/brown wilting or curling leaves.
- Only sample an elm tree between June 1 and September 30. Infected leaves may be confused with leaves changing colour in the fall.
- Sterilize your pruning tools with 10 per cent bleach, 70 per cent rubbing alcohol or gas line antifreeze.
- Choose a branch showing symptoms of wilting or flagging. Infected wood may appear to be stained brown. To confirm, peel back the bark and look for brown staining in the sapwood, or just under the bark. While staining is a strong indicator of DED, it is not always present in a diseased tree.
- Select a smooth and straight branch, without any cankers or knots, that is not dried out or dead.
- Ensure each branch is 1 to 1.5 cm in diameter (about the size of your index finger).
- Each piece should be 10 to 15 cm long (see photos 1 and 2).
- Cut three to four branches.
- Please do not send elm leaves, elm trunks and large branches to the lab.
- Remove the leaves and twigs from the cut pieces of the branch, but do not remove the bark.
- Wrap all branch pieces in wax paper and secure with tape to prevent drying.
- If sampling more than one tree, be sure to sterilize your pruning tools between each tree. Keep each sample separate and clearly marked/identified.
- Place the sample(s) in an envelope. Make sure to include your name, address, phone number and the location of the tree(s).
- Send the sample as soon as possible to:
Crop Protection Laboratory
346 McDonald Street
Regina SK S4N 6P6
Important Points to Remember
- Samples can be submitted between June 1 and September 30 each year. Samples will not be accepted after September 30.
- If the sample needs to be stored temporarily prior to submission, it should be kept in a cooler or a fridge to prevent deterioration.
- Ensure that the sample is taken from a branch showing symptoms; otherwise, the results may not be accurate.
When to Expect Results
- Testing begins in June. Samples are tested on a first–come, first-served basis. Results for diagnoses will be provided within 15 working days of the Crop Protection Lab receiving a viable sample.
- A positive result means DED is present on the sample and the tree must be removed. A negative result indicates the absence of the disease.
What to do When the Tree is Tested Positive for DED
- DED is provincially regulated under The Forest Resources Management Act and is federally regulated under The Plant Protection Act. Trees confirmed to have DED are to be removed immediately, and the wood must be promptly disposed of at the nearest elm tree disposal site. The Saskatchewan Ministry of Environment will be notified of any positive results.
- To find out more about DED and what you can do about it, or if you suspect an elm tree has the disease, contact the Saskatchewan Ministry of Environment DED line at 1-800-567-4224. Contact your local municipal office for more information about infected elm tree or wood disposal sites.