Forest Health

Teacher Background

1. Foliar Disease

a) Brown Felt Blight

• Attacks the foliage of the tree.
• Symptoms that the tree is infected: Discolouring of needles, thinning of the foliage.
• Signs of the disease: Dark masses of mycelium on the branches.

b) Douglas Fir Needle Blight

• Attacks the foliage of the tree.
• Symptoms that the tree is infected: Discolouring of needles, thinning of the foliage, dark spots on the needles.
• Signs of the disease: Black fruiting bodies on the needles.

2. Wood Decay

a) Brown Crumbly Rot

• Attacks the tree wood.
• Symptoms that the tree is infected: Brittle cube-like wood structure.
• Signs of the disease: Staining of the wood, conks on the stem.

b) White Laminated Rot

• Attack the tree wood.
• Symptoms that the tree is infected: Pitted wood structure.
• Signs of the disease: Yellow discolouration of the wood.

3. Mistletoe

a) Douglas Fir Dwarf Mistletoe

• Attacks branches and stems.
• Symptoms that the tree is infected: Reduction in tree growth.
• Signs of the disease: Large broom-like structures forming on the branches of the crown.

4. Root Disease

a) Armillaria Root Rot

• Attacks the root system.
• Symptoms that the tree is infected: Discolouring of needles, thinning of the foliage, reduction in tree growth.
• Signs of the disease: Whitish fan-like fungal mycelia between the bark and wood and mushrooms at the base of the tree.

b) Laminated Root Rot

• Attacks the root system.
• Symptoms that the tree is infected: Discolouring of needles, thinning of the foliage, reduction in tree growth.
• Signs of the disease: Pitted wood structure, red-brown stains on fresh stumps or on cross sections of major roots.

5. Defoliating Insects

a) Tussock Moth

• This insect attacks Douglas fir.
• The larvae are responsible for defoliating the foliage.
• The female adult does not have wings; she emits a pheromone (scent), which attracts the male to her.
• For more information refer to pest leaflet #9.
  www.pfc.cfs.nrcan.gc.ca

b) Tent Caterpillar

• These insects attack many deciduous trees (alder, ash, birch, cottonwood, willow, and many fruit trees).
• The larvae are responsible for defoliating the foliage.
• They got their name from the silk tent like nests they make in the tree.

6. Gall Adelgids (Aphid-like Insects)

• The Cooley Spruce Gall Adelgid alternates between two trees: Douglas fir and spruce.
• It causes cone-like galls or swellings on the branches of spruce trees.
• Light infestations are common, yet not seriously damaging.
• Small trees stressed by environmental conditions are often more heavily infested.

7. Bark Beetles

• Galleries – every year female bark beetles fly to a new large, mature tree and bore into the bark of the tree and start making galleries (tunnels) under the bark (this prevents the flow of nutrients and water to the crown of the tree resulting in mortality). They then lay eggs in galleries. (show gallery sample from Mountain Pine Beetle package)
• Pheromone – the female beetle emits a pheromone to attract more beetles to the tree to overcome the tree’s defence mechanism (the more beetles the better the chance of overcoming the tree’s defence mechanism) and to attract a mate.
• Pitch Tubes – the tree’s only defence mechanism against the beetle is to pitch them out with its sap.
• Blue Stain – the beetles introduce a fungus into the tree, which grows into the sapwood of the tree and causes it to turn a blue colour. When growing into the sapwood the fungus prevents the tree from pitching out the beetles. (show blue stain sample from MPB package)
• Current Epidemic – Beetle outbreaks are a natural occurrence in our forests, but right now the mountain pine beetle is out of balance in nature and is a big problem in BC. It is killing millions of hectares of trees every year. We will not win this battle, but we will learn from it... we need to react quickly (even if the attack is in a park), we need to understand the ecological process that mature and over mature pines are a target to these bark beetles.

8. Weevils (Snout Beetles)

• There are 2 main species of weevils in BC:
• Spruce Leader Weevil, Pissodes strobi: attack spruce
• Lodgepole Pine Terminal Weevil, Pissodes terminalis: attack lodgepole pine
• Weevils attack the terminal leader of the tree.
• The female lays her eggs in the terminal leader.
• The larvae mine (eat) down the terminal leader.
• The terminal leader wilts and dies, which forces the lateral leaders to take over the vertical growth.
• Weevils rarely kill trees but rather affect the growth of trees.
• Defects:
  • Crease – minor defect, little or no stem curvature at the point of attack.
  • Crook – a major defect, stem curvature by at least ½ the stem diameter.
  • Fork – a major defect resulting when 2 lateral stems assuming the vertical growth of the tree.
  • Staghead – a major defect resulting from 3 or more lateral stems assuming the vertical growth of the tree.

9. Wood Borers

a) Flat headed wood borers

• Adults are often metallic in colour.
• Adults are attracted to dead and dying trees.
• They lay their eggs in bark crevices.
• Larvae have flat heads.
• Larvae make galleries under the bark and into the wood.
• Larval galleries in the wood are oval and they enter the wood at an angle.
• The holes that are made in the wood by the larvae decrease the wood value.

b) Long horned wood borers

• Adults have antennae that are half as long as their body or longer.
• Adults are attracted to dead and dying trees.
• They lay their eggs in bark crevices.
• Larvae do not have flat heads.
• Larvae make galleries under the bark and into the wood.
• Larval galleries in the wood are circular and they enter the wood straight on.
• The holes that are made in the wood by the larvae decrease the wood value.

DOWNLOAD the tree diseases chart here. 50Kb PDF

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