Forest Health

The term forest health relates to the identification and management of damaging agents in the forests.  This includes insects, diseases, animals, and abiotic factors (i.e. wind).  Not all damage is detrimental, and endemic (agents or pests that are always present here) levels of forest heath "pests" are not usually a problem.  However, sometimes damaging agents become epidemic, which is when management considerations need to be addressed.

The two major factors affecting the health of the Haida Gwaii Forest District's forests are wind damage and deer browse.  

Windthrow

Licensees can manage for the effect of wind damage on trees by:

  • feathering the cutblock edge
  • removing the trees with the most windthrow potential
  • designing the cutblock as to disperse the force of the wind
  • tree topping and pruning to make the surrounding timber windfirm.

Tree topping an pruning is usually done to protect high value features (such as streams) as the treatment is quite expensive.
Top

Deer Browse

Damage resulting from deer browse can be reduced by using protective cones on all cedar and cypress seedlings.  Cones must be maintained until the seedling is well out of the top of the cone.

In addition to these damage agents, several forest diseases and insects contribute to compromising the health of our forests.

Top

Forest Diseases

The major disease impacting the forested land base is Hemlock Dwarf Mistletoe (Arceuthobium tsugense).  Hemlock mistletoe is managed for by not regenerating hemlock adjacent to infected sites as well as by instituting the greater than or equal to 3 metre knock down rule.  All trees that are greater than or equal to 3 metres in height are cut within hemlock mistletoe infected stands.

Minor forest diseases that are not managed for in QCIFD are:

  • Spruce Broom Rust (Chrysomyxa arctostaphyli)

  • Armillaria Root Disease (Armillaria ostoyae)

  • Annosus Root Disease (Heterobasidion annosum)

  • Western Gall Rust (Endocronartium harknessii)

Top

Forest Insects

There are three insects that cause damage within this district.  Two of these insects work together, defoliating trees sometimes in the thousands of hectares.  Other minor forest pests exist, but do not cause significant damage in this district. 

The Western Blackheaded Budworm and Hemlock Sawfly

The western blackheaded budworm (Acleris gloverana) and hemlock sawfly (Neodiprion tsugae) both defoliate hemlock and spruce trees. 

Their infestations are cyclical in nature, usually occurring in a 10 year cycle.  Time is needed for the insect populations to build up until it reaches a peak, followed by a population crash.  Both insects feed on part of the foliage; however, the blackheaded budworm prefers the new foliage, whereas the hemlock sawfly prefers the second and third year foliage. 

Insect feeding rarely leads to tree mortality, except on poor, rocky, or high elevation sites.  Growth rates are affected by the insects feeding patterns.  Evidence of insect damage can be seen by the affected trees which turn brown.

Outbreaks and the Queen Charlotte Islands

Infestations in the Queen Charlotte Islands have started in the South Moresby area and moved northward from there.  The last outbreak on the islands occurred from 1996-2001.  The Canadian Forest Service is currently working on a project to monitor the effect on growth caused by budworm and sawfly defoliation.

Outbreaks of these insects are not treated in this district since the risk of mortality is low.  However, in the future, we may have to look for treatment since the amount of second growth trees is more significant today than it has been in the past which may lead to a greater intensity of insect attack. 

The White Pine Weevil

This insect is not in the Queen Charlotte Islands yet, but it is a potential risk.

Photograph of the White Pine Weevil (approx. 6mm)

The white pine weevil (Pissodes strobi), despite its name, attacks spruce trees, mainly Sitka Spruce.  This insect attacks regenerating spruce trees by boring into the previous year's leader and depositing eggs inside it.  The larvae emerge and feed down the leader, thus girdling the stem and killing the current leader of the tree.  This results in dead, deformed, or multiple leaders.  This insect has greatly reduced forester's ability to plant Sitka spruce in areas such as Vancouver Island.

Outbreaks and the Queen Charlotte Islands

This insect is not in the Haida Gwaii Forest District at this time.  However, trees from the HGFD when transported elsewhere, were found to be especially vulnerable to the white pine weevil.  It is unclear if the insect cannot survive here because of the cool climate, or if it simply has not been transported here yet.  Since spruce is a major part of our forest ecosystem, the introduction of this forest pest would be catastrophic.

For this reason we ask that visitors to the island DO NOT bring live trees or forest litter material to prevent the introduction of this or other forest pests.   

The Green Spruce Aphid

The spruce aphid (Elatobium abietinum) attacks spruce trees by sucking on sap from the underside of the needles.  Outbreaks of this pest occur in a cyclical pattern. 

Trees that are attacked are spruce two years old or greater growing along the shoreline in the salt spray zone.  The aphid will only attack trees up to a certain elevation, depending on the topography of the site, usually 100-200 metres above sea level.

Outbreaks and the Queen Charlotte Islands

Feeding of the aphid can kill trees or greatly weaken them.  Trees affected by the aphid can be seen along any coast of the Queen Charlotte Islands.  Damage is visible as a band of brown trees along the shoreline.  

No management strategies are in place for the spruce aphid since the insect population only causes some tree mortality. Spruce trees are the best tree for the salt spray zone site following tree mortality due to aphids.  Spruce regeneration is usually vigorous in coastal areas.  Spruce aphid attacks, in these circumstances, play a role as the natural agent of forest succession.

Top