Which pest usually attacks weak trees and can build up to an outbreak, making galleries in fresh phloem?

Which pest usually attacks weak trees and can build up to an outbreak, making galleries in fresh phloem?

• A. Bark beetles
• B. Mountain pine beetle
• C. Pine engraver beetle
• D. Douglas fir tussock moth

Answer: (A)

Bark beetles are drawn to trees that are stressed or weakened, and they can switch from small populations to large outbreaks when conditions allow. They bore through the bark and feed in the phloem just under the surface, carving distinctive galleries as they work. This pattern—attack on weak trees and the potential to erupt into an outbreak with galleries in fresh phloem—fits bark beetles best, which is why this option is the right one. While mountain pine beetle and pine engraver beetle are examples of bark beetles that exhibit this behavior, the core idea is the bark beetle lifestyle itself. The Douglas fir tussock moth defoliates needles rather than creating phloem galleries, so it doesn’t match the scenario.

Bark beetles are drawn to trees that are stressed or weakened, and they can switch from small populations to large outbreaks when conditions allow. They bore through the bark and feed in the phloem just under the surface, carving distinctive galleries as they work. This pattern—attack on weak trees and the potential to erupt into an outbreak with galleries in fresh phloem—fits bark beetles best, which is why this option is the right one. While mountain pine beetle and pine engraver beetle are examples of bark beetles that exhibit this behavior, the core idea is the bark beetle lifestyle itself. The Douglas fir tussock moth defoliates needles rather than creating phloem galleries, so it doesn’t match the scenario.