Trees and the Urban Forest

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:

• Learn more about the Douglas-fir beetle and how to manage an infestation
  

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:

• Download the BC Government's March 2020 Guide to Managing Spruce Beetles on Private Property [PDF]
  

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.