The Damage Spruce Beetles Can Do

The Facts and Figures of the Spruce Beetle

  • Spruce beetles are just 1/4 inch in length.
  • Beetles live at the thin, phloem (growing) layer between the bark and the wood. Therefore the wood stays intact from the beetles and is usable for construction for a while.
  • One female beetle may lay from 10 to 150 eggs in”galleries” assembled beneath the bark in the phloem tissue. Beetles emerge from infested trees and fly to new host trees out of mid-May until mid-July (when temperatures are over 60° F).
  • Spruce Beetles feed and breed on wind-thrown, fallen, or injured trees wherever there are spruce woods. When conditions are appropriate, beetle populations may outgrow the source of down trees and move into neighboring living trees, especially older spruce stands.
  • Recent annual statewide aerial surveys have suggested that the ongoing spruce beetle outbreak in Southcentral Alaska has affected more than 900,000 cumulative acres from 2016-2018. Statewide, almost 600,000 acres of ongoing spruce beetle activity were mapped in 2018.
  • Human activities such as fire suppression and improper use of slash enhance conditions for beetle outbreaks; as do natural phenomena such as wind-thrown, fire-scorched, or flood-damaged trees.
  • Fast-growing, healthy trees are more resistant to beetle attacks than slow-moving trees that are unhealthy.
  • Beetles can emerge out of infested firewood and attack trees.
  • Beetles produce chemicals called pheromones to communicate with other beetles — for breeding, to find vulnerable host trees, and to repel additional spruce beetles. Spruce trees also produce chemicals that impact beetle behavior. These compounds show potential for changing beetle behavior and lessening the severity or even preventing, harmful infestations.
  • Several EPA-approved insecticides have provided 100% protection against beetle attacks for two decades, based on research.


Spruce Beetles in Firewood

Spruce beetles assault and breed just in spruce. Aspen, cottonwood, and other trees aren’t in danger. The recently hatched larvae create feeding tunnels in right angles into the bigger egg galleries, in which they finish their two or one-year life cycle. If numerous beetles strike the tree, then the resulting brood could girdle Spruce beetles would rather assault lately windthrown trees, however, they also attack and destroy standing trees that are weakened or diseased. Slow-growing and not as vigorous trees can also be attacked when circumstances favor beetle dispersal. Trees killed by spruce beetles are frequently used as firewood. Throughout The very first winter following infestation both larvae and adult beetles can be found beneath the bark. Adult beetles may also be under the bark around the base of this tree during the second winter and might emerge the next spring. Two years following the assault, beetles have abandoned the tree. A two-year life cycle is the most frequent in South-central Alaska. Adult beetles over-wintering beneath the bark of firewood emerge when Warmer weather arrives and search out new host material, often a precious Landscape tree close to the woodpile. By analyzing spruce logs for use For firewood, and after hints below, you might avoid spruce Beetle infestations on your live-standing trees.

Condition of spruce firewood and ways to reduce beetle populations:

Fresh log with green needles when cut; bark peels away from wood smoothly; wood not split.

  • Store only enough firewood for a single winter’s use.
  • Split into stove-size pieces to dry out; stack loosely or separate to allow maximum air circulation.
  • Dry wood discourages new spruce beetle attacks.
  • De-bark log to eliminate potential beetle habitat.

Fresh log with green needles when cut; visible beetle attacks on bark surface (reddish-brown boring dust and pitch globules); bark may peel smoothly; wood not split.

  • Split and use prior to next spring to kill adult beetles that will emerge at that time.
  • Fire-scorch the outer portion of the bark, killing beetles beneath, but keep the bulk of the wood intact (messy, but intact) for future use.
  • Consider preventive measures on surrounding live spruce trees.

Dry log; rust-colored or no needles present on the tree when cut; some evidence of old beetle attacks or woodpecker activity; bark may adhere tightly or pull off in pieces.

  • Spruce beetles will not attack well-seasoned wood and are normally gone from trees that have been dead for more than one year ( though beetles and other insects may enter the wood). Old wood, free of spruce beetles, is not a potential spruce beetle infestation source.

Dry, old log or split wood; barks pulls off loosely