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Parks, Recreation, & Culture » Trees - Urban Forestry » Forest Health

Spruce Budworm

Western spruce budworm (Choristoneura occidentalis) is a primary defoliator of interior Douglas-fir in British Columbia (BC). During outbreak situations, defoliation can result in significant damage to infested trees which can in turn negatively affect various land values.

Impacts of the Western Spruce Budworm

The budworm moth prefers the upper to mid-crown section of larger host trees for depositing eggs. When the hatched larvae disperse small trees that are growing underneath or in close proximity to large trees may receive a disproportionate number of larvae. Small trees have a greater percentage of the preferred current-year foliage than large trees and as a result are subject to heavier defoliation during budworm outbreaks.

Impacts caused by Western Spruce Budworm outbreaks as they relate to forested land in the City of Kamloops include:

  • foliage loss and bud destruction, causing a reduction in the tree's photosynthetic capability and growth potential
  • reduced seed production for replenishing forests due to damaged cones
  • top kill resulting in stem defects and possible overhead hazards
  • increased susceptibility of weakened trees to other forest health agents such as Douglas-fir beetle and root disease
  • mortality, particularly of understory trees
  • increased fire hazard due to dead foliage and dead understory trees
  • reduced aesthetic values due to stand defoliation and an abundance of feeding larvae

  • nutrient influx to the soil from shed foliage and frass from budworm feeding
  • contribution to the food chain for predators and parasites of the budworm such as ants, birds and insect parasitoids
  • natural stand thinning resulting in more resources for surviving trees and more forage for wildlife

When negative impacts are weighed against the positive ones, a net overall loss of stand value is realized. Douglas-fir trees on the identified city land are a valuable commodity, as they represent the vast majority of the trees that will remain after the current mountain pine beetle epidemic is finished.

What is the City of Kamloops Doing?

Observations by City of Kamloops Natural Resource staff noted an apparent significant increase in Spruce Budworm occurrence in the summer of 2007 over previous years. The City of Kamloops contracted a forest health specialist to conduct egg mass surveys and developed a City-wide Spruce Budworm management plan in the fall of 2007.

Egg mass surveys indicated infestation levels to be moderate in Kenna Cartwright Park and low in all other City-owned areas in the City. The consultant recommended aerial spraying of 300 hectares within Kenna Cartwright Park with Btk for the spring of 2008. This program was completed on June 7, 2008.

City-wide egg- mass surveys conducted in the fall of 2008 will determine future management actions on City owned properties.

What Can You Do?

Monitor your trees and review the information provided in this section. If you suspect forest health issues with your trees contact a certified arborist or forest health professional for further investigation

For More Information:

Parks Operations
955 Concordia Way
Phone 250 828 3551

Note: All correspondence is entered into our system and will be directed accordingly. The City of Kamloops will endeavor to contact you within two business days. Thank you.