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Pine Tree Anatomy

& Pine Beetles


Once bark beetles identify suitable tree hosts, they can mass attack and kill living trees.  The mass attack process is initiated when adult females bores into a tree and then release pheromones that attract large numbers of beetles.  The beetles can colonize the tree when the infestation overwhelms the tree’s defenses. 


To better understand the process by which beetles kill their host tree and how trees defend themselves against beetle attacks, it is useful to know some basic tree anatomy. The activities in this lesson will familiarize students with the basics of softwood anatomy at the macroscopic and microscopic scales as well the process by which the bark beetle infects a host tree.

Learning Goals:

After completing this activity, students will be able to understand:

  • The appearance of the tree’s structures will be different (both microscopically and macroscopically) depending on the type of cut made in the wood (transvers, radial, etc)

  • Xylem – conducts water and nutrients up from the soil

  • Phloem – conducts sugar from leaves to the roots

  • Resin moves through the xylem and phloem through rays to the bark. This resin is part of the trees’ defense mechanism against beetles and fungus.

  • When trees are unable to produce enough resin (genetics, age, drought), pine beetles will not be washed out of the tree by the resin.

  • Pine beetle females lay eggs in the phloem.

  • Females carry and introduce the blue stain fungus into the xylem and phloem of the tree.

  • Blue stain fungus strangles the tree by cutting off fluid circulation in the xylem and phloem.

Grades: 6-8


* Lesson plans are available in .doc format for easy customization.  Please contact us with any questions or problems.

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