Spongy Moth Spraying in BC - Questions and Concerns

The Canadian government were planning, and recently approved spraying mass amounts of land with a biological insecticide called Bacillus thuringiensis ssp. Kurstaki, or BtK, to target and prevent the invasive Spongy Moth (Lymantria dispar dispar) from fully establishing.

All the news outlets I was seeing were very vague with what was being used, what the affects on other fauna would be like, and even where they were spraying. After looking into it a bit more, the insecticide only affects lepidoptera (moths/butterflies), however it affects EVERY species alongside the Spongy Moth, including native and endangered species. Right next to where they plan to spray, there’s the pretty famous endangered species Grammia complicata.

Thankfully it doesn’t look like it affects every moth or butterfly to the same degree (see here) but it still feels pretty reckless to spray such a huge amount, in such ‘risky’ areas housing so many natives and quite a few endangered species, and the lack of information given on that aspect doesn’t sit well with me.

Is me being worried about this unreasonable because it’s been used for so long? No clue! That’s why I thought I’d ask you guys and start a discussion about this.


I don’t know much about this specific case, but I did work for lab that worked on spongy months for decades. Here are a couple things that come to my mind:

  1. Spongy moth caterpillars are present relatively early in the season and tend to prefer oaks. Targeting specific times and trees/stands limits exposure to non-target caterpillars.
  2. Some biocontrol microbes have species-specific strains. I have no idea if those have been developed for BtK, but they have for some fungi.
  3. Widespread defoliation is pretty drastic and not good for native species either, so there are tradeoffs to consider.

Hey! That sounds really cool, thank you for the reply!

  1. It’s good they’re only targeting a specific type of foliage, I was under the presumption that they had a wide range of host plants. I don’t think that just targeting oak forests early in the year will cut back on the amount of damage done to native species though, underneath the tree canopy there’s hundreds of plant species and moths designed to eat them. Even just in my secluded spot in interior BC this month I’ve seen 30 or so caterpillars ranging from first and last instar on virtually every plant.

  2. Interesting! I don’t believe one exists for BtK, but I’ll look into the subject more anyways ^

  3. That is true! Both seem pretty detrimental to native species, the moth more-so if it establishes, I still don’t know if I appreciate the media’s ambiguity and information side-steps, I had to dig for a bit to find information about it being detrimental to other early native species, which feels like something the media should be upfront about.

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