Spruce Budworm & BTK - Some Info for Redwood Meadows Residents
We’ve received a lot of questions from our neighbours about Townsite’s plan to complete an aerial application of BTK and our thoughts on it.
While we recognize the discussion and debate that has occurred so far and appreciate the contentious nature this decision may have, we felt it was important to address some of the questions. We live here in Redwood Meadows, too. And while it may at times be difficult to relate a company that cuts trees with people who actually love the trees, we moved to this community for exactly that appreciation. But that’s a chat we’d be thrilled to have another time - let’s talk bud worms for now.
It’s important to preface this with a bit of a disclaimer - we do not represent our townsite or it’s council, and this in no way is meant to be a comprehensive information package for residents. Townsite has pledged to gather all relevant materials and distribute them accordingly. We aren’t experts in entomology or chemists or the like, this is simply our response to the questions we’ve fielded from our neighbours and a bit of sharing on what we know about the topic.
The spruce bud worm has a particular appetite for white spruce, the dominant tree species within our community. The bud worm itself is a species of caterpillar, and as any other variety, creates a cocoon and becomes a moth as it matures to adulthood. These moths then travel from tree to tree, laying their eggs within the spruce needles where they will stay for the winter and hatch the following spring.
As spring comes around, the eggs hatch and the larvae begin to seek out new growth on the tree. As buds start to emerge, the larvae begin to create silk clusters around the new bud to protect themselves as they begin to eat the newly growing needles. Any application of BTK that occurs in this early spring period would be ineffective, as the worms must ingest a lethal dose. As they’re well protected within their hide out’s, this would not occur.
As the worms continue to feed, eventually the new growth is consumed and the worms begin to seek out additional buds. By now the worms are larger, and not as encapsulated by their silk protection. This is the stage we all get disgusted by, as a simple shake of the branch from wind or any other disturbance causes the worms to dangle from their silk threads. They cover the sides of homes and get just about everywhere as you try to mow your lawn. It’s immediately before this stage, as the worms start to emerge from their protective silk homes, that an application of BTK is most effective.
This does mean, however, that this current years growth will also be consumed. Research has shown that any attempt to protect the current years growth does not impact the worm population in a meaningful way. Townsite is making a critically important decision in our situation by engaging an entomologist to notify us of the precise period in which the worms are most susceptible to ensure the maximum effectiveness of population control.
Studies on the development of the spruce bud worm and the bud growth of white spruce all have one very troubling result in common - each study had to change the trees they were utilizing half way through the study as midway through the feeding period, the current years growth had already been stripped away. Trees need new growth to remain healthy. A tree that is robbed the opportunity to achieve new growth due to insects like the bud worm tend to try even harder the following year. The tree tends to ignore attempts to heal open wounds and shuttles all of its nutrients in to new growth. Year after year of these failed attempts puts such incredible stress on the tree. We’re all accustomed to seeing those gorgeous spruce cones on our trees, our children collecting them in the fall to make crafts with. We haven’t had a single cone on our trees for years, a sign of the significant stress the trees are under. These cones allow the tree to reproduce. The absence of them spells the inevitable end of natural repopulation and reforestation.
Over the past few years of our current infestation, our spruce trees have been dying. As the worms eat all of the new growth and the trees are stressed ever further, their branches dry out and disease enters the tree as moisture is focused to areas of attempted growth. Our trees are dying. The crispy branches and abundance of spruce needles on the ground spell the imminent end of our trees. If you’ve followed along with some of our posts, you’ll have seen the intense level of dead and hazardous trees that require removal. Additional stresses on the trees and a lack of reforestation through cone generation will not only further complicate the number of critically hazardous trees, it leaves us increasingly susceptible to the catastrophic effects of a wildland/urban interface fire.
Townsite has taken critical steps to ensure the maximum effectiveness of an aerial application of BTK and has done their homework well. The correct experts are involved to ensure the best possible outcome. We’ve received questions about a natural cycle for these insects, suggesting that they’ll move on on their own. While technically that is correct, the worms leave when there’s no more food to sustain them - when all of our white spruce are dead and cannot generate ANY new growth. Coupled with the lack of natural reforestation and the incredible hazard dead trees 75 feet tall and higher present hanging over our homes, without this critical intervention we will not live in this beautifully forested area much longer.
Trees, much like us, can benefit from the occasional health intervention or prescribed medication. BTK is perhaps the safest and best medication for this current situation. BTK has been used in numerous communities across Canada and around the world as a way to eliminate harmful moth infestations. A natural occurring bacterium, it is harmful only to caterpillars and must be applied through a spray application. Aerial spraying remains the most effective and inexpensive way to eradicate infestations (vs. ground spraying).
There’s been debate as to whether BTK is a pesticide - a pesticide is defined as a substance used for destroying insects or other organisms harmful to plants or animals. By this definition, yes - BTK is a pesticide. It is however a biological insecticide. It is a rod-shaped bacterium found naturally in dead or decaying soil. First isolated in 1902, it is widely used by gardeners and forest services as it is effective and safe.
A look at the Safety Data Sheet (SDS) for BTK can be a bit alarming, as it speaks to skin and eye irritation, a requirement to keep it away from waterways, etc. It is important to understand that this SDS speaks to BTK concentrated in storage and transportation containers. Should a large drum of concentrated BTK be splashed in to your eyes or on your skin, it will cause irritation. Dumping a tanker truck of BTK into the Elbow River will have detrimental effects to the ecology of the area. Once dispersed through a spray applicator, however, the concentrations or BTK are not enough to cause irritation or concern to the rivers or waterways. Remember, BTK is a natural bacterium found in decaying soil. The amount applied through an aerial application will not significantly impact the naturally occurring concentrations within the ground, it will simply generate sufficient amounts above ground to impact the current spruce bud worm infestation. BTK is also fairly unique in it’s targeting of caterpillars, and is considered non-toxic to other flora and fauna. Our wildlife will not be impacted by the application of BTK, however the complete deforestation of our area will not only take away their homes but their food sources as well.
There will always be concerns with the use of pesticides to manage insects. One health recommendation made specifically for aerial applications is directed at those who may have compromised respiratory systems. For these individuals, it’s advised to close all windows in their home the evening before application and stay indoors for one hour after aerial application concludes. By that time, airborne droplets are no longer present. Ideally we wouldn’t find ourselves in a situation where the use of pesticides was required to manage this infestation, however BTK remains the safest and most effective option and has been used since the 1960’s for successful aerial applications. The risk of not conducting this application is far greater as our trees continue to die and we end up needing to remove the forest we all love.
Additional Resources:
https://www.nrcan.gc.ca/our-natural-resources/forests-forestry/wildland-fires-insects-disturban/top-forest-insects-diseases-cana/spruce-budworm/13383
https://extension.entm.purdue.edu/GM/PDF/GMquestions.pdf
https://www2.gov.bc.ca/gov/content/industry/forestry/managing-our-forest-resources/forest-health/invasive-forest-pests/gypsy-moth/what-is-btk
https://www2.gov.bc.ca/gov/content/industry/forestry/managing-our-forest-resources/forest-health/invasive-forest-pests/gypsy-moth/spraying-with-btk
http://www7.mississauga.ca/documents/parks/forestry/2018-Aerial-Spray/SDS.pdf
https://tidcf.nrcan.gc.ca/en/insects/factsheet/12018
https://www.nrcan.gc.ca/forests/fire-insects-disturbances/top-insects/13403
https://www.nrcan.gc.ca/simply-science/20299/slowing-down-spruce-budworm-ask-nrcan/22113
https://cwf-fcf.org/en/resources/encyclopedias/flora/spruce-trees-of-canada.html
Written by Sean Sterna - The Rocky Mountain Arborist & Used with Permission