What is the alternate host for Cooley spruce gall adelgid?

What is the alternate host for Cooley spruce gall adelgid?

• A. Douglas fir.
• B. Western hemlock.
• C. Lodgepole pine.
• D. Sitka spruce.

Answer: (A)

Cooley spruce gall adelgid uses a two-host life cycle, involving both spruce and Douglas-fir. On spruce trees, it causes the distinctive galls that distort twigs. The insect then moves to Douglas-fir to complete a different life stage (the sexual form) before returning to spruce to continue the cycle. Because of this two-host requirement, Douglas-fir is the alternate host. The other trees listed do not serve this two-host role for this adelgid, though they may be involved with other pests in different systems. Understanding that the insect relies on Douglas-fir as an alternate host helps explain why management must consider both hosts and timing across hosts.

Cooley spruce gall adelgid uses a two-host life cycle, involving both spruce and Douglas-fir. On spruce trees, it causes the distinctive galls that distort twigs. The insect then moves to Douglas-fir to complete a different life stage (the sexual form) before returning to spruce to continue the cycle. Because of this two-host requirement, Douglas-fir is the alternate host.

The other trees listed do not serve this two-host role for this adelgid, though they may be involved with other pests in different systems. Understanding that the insect relies on Douglas-fir as an alternate host helps explain why management must consider both hosts and timing across hosts.