- Most declining tree health begins with drought-related stress and frequent deep watering will often significantly improve a tree’s health.
- Disease and insect agents usually attack drought-stressed trees and are usually only a secondary cause of declining tree health.
- Herbicides can also damage or kill trees, as trees are just larger versions of broad-leafed weeds. Never use herbicides in hot weather or apply under a tree canopy.
- Keep trees healthy by keeping grass away from the tree base. It reduces root compaction from mowers, eliminates the chance of damage from string trimmers, and reduces competition for water and nutrients.
Diseases and Pests
Insect pests on ornamental trees are usually more troubling to the resident than to the tree and most trees and shrubs can survive an infestation. Most pest and disease problems in an urban environment are the result of:
- Too much or too little water, light, or fertiliser.
For more information:
Douglas-fir beetle outbreaks occur regularly in British Columbia and usually last up to five or six years. Certain parts of BC experience higher than normal populations of these pests, including the area around Prince George. The colour of an infected tree's needles offer a visual indication of the infestation's progress:
Pale Green or Yellow - The tree has been recently attacked.
Bright Red - The tree was infested the previous year.
Brown - Along with sparse foliage, brown needles indicate the tree has been dead for two or three years.
Grey - A grey tree that has lost its needles has been dead for more than two years.
For more information:
Spruce beetle outbreaks are a normal occurrence in spruce forests and typically last five or more years. Outbreaks often happen when beetle levels rise in trees that have been blown down, with the insects eventually moving on to attack living spruce trees.
Bark beetle populations - including the spruce beetle - are increasing beyond normal levels thanks to changing weather and climate. Mild winters have led to increased winter survival rates and favourable weather conditions have increased how quickly these beetles can complete their life cycle.
External Signs of Infestation
- A pale yellow-green or red-brown crown. It may take a year or more for needles to change colour and fall off.
- Light brown or red-brown fine sawdust on the tree's bark and around the tree base.
- Crystallised tree sap on the bark. This may not always be present, especially if a beetle attack occurs in the late fall or in stressed trees.
- The layer of tissue between the tree bark and wood is brown and crumbly.
For more information on how to spot other signs of spruce beetle infestation, taking preventative measures, removing trees under attack, and more:
Note: Although the BC Government recommends burning infected trees to destroy spruce beetles, the City of Prince George Clean Air Bylaw No. 8266 prohibits open burning at any time and recreational fires (under 60 cm) are prohibited during an air quality advisory.
- Accurately identify the plant. Many insects and diseases are plant-specific. This information can quickly limit the number of suspected diseases and disorders.
- Compare the affected plant with other plants on the site. If damage is restricted to a single specimen it may indicate insect, disease, or mechanical damage. Damage to several trees or plants, especially of different types, is an indication of environmental damage such as drought, flood, heat damage, gaseous fumes, opening of the tree canopy, or a toxic spill.
- Examine the roots. Brown roots usually indicate dry soil conditions or the presence of toxic chemicals. Black roots reflect overly wet soil or the presence of root-rotting organisms.
- Examine the trunk for wounds. Wounds can be caused by weather, fire, lawnmowers, and rodents, as well as a variety of other mechanical factors.
- Note the position and appearance of affected leaves. Dead leaves at the top of the tree are usually the result of root stress. Twisted or curled leaves may indicate viral infection, insect feeding, or exposure to herbicides.
It is important to remember most insects are beneficial rather than destructive. Insects help with pollination or act as predators of more harmful species. In the unlikely event that the City needs to use chemical controls on City-owned trees, the softest control method possible, such as insecticidal soap, is used.
City tree-planting standards follow those outlined by the International Society of Arboriculture. This planting method is recommended for use by residents planting trees on their own property as well. Residents must get permission from the City before planting a tree on municipal property. Trees growing on City property are owned by the City regardless of who planted them. Pruning or planting of City-owned trees is not permitted by anyone other than City staff or contractors.
A number of tree species are recommended for planting within the City of Prince George due to their ability to prosper under local conditions and the provision of environmental benefits.
The City has produced a guide with more information about trees that are recommended for planting in Prince George. The guide also identifies the appropriate use of trees in various locations.
Trees on City Property
If a tree is within eight to 20 feet from the front of a property, it is most likely on City ground and will be maintained or treated by the Parks and Solid Waste Division.
Trees considered hazardous are removed to prevent harm to people or property. The City does not remove healthy trees that drop branches, cones, or seeds onto private property.
To confirm if a tree is on City property, call 311 for more information.
City trees are often pruned in the winter months when trees are dormant to prevent unnecessary stress and damage. Reasons for pruning include:
- Avoiding impeding pedestrians, vehicles, and City utilities, including garbage and snow removal services.
- Public safety and health.
- Aesthetic reasons.
Trees on City-owned boulevards may only be pruned by City staff.