A number of B.C. residents including those in Zone three were notified of a spraying program to happen this year to eradicate the Spongy Moth or Gypsy moth as previously known. Kamloops, Cranbrook, West Kelowna, Langley and Tsawwassen will be treated as well as communities on Vancouver Island.

I could remember a number of years ago being asked to hang pheromone traps (hormone traps to attract the male moth) in my apple trees to see if there was evidence of these moths. At the time we found none. However, they are now apparently becoming established in areas of B.C. In an effort to eradicate the infestations, the affected areas where the moth has been found will be aerial sprayed three times this spring with Btk or Bacillus thuringiensis.

Spongy Moth larvae, caterpillars, strip their preferred trees of leaves, totally strip them. As if our orchardists don’t have enough to deal with this year after the extreme cold spell this winter, they certainly don’t need this problem in addition. These are not the little green caterpillars that strip so many Manitoba Maples and other trees in our parks. Trees usually recover from those attacks by developing a second set of leaves. The Spongy Moth larvae apparently inflict more lasting damage.  Both these types of moth cycle, meaning some years there are heavier infestations than others.

The bacteria BT or Btk is a naturally occurring organism and one which is extremely useful in treating stagnant and still water with mosquito larvae. When used as a pesticide it is in concentrated form. My immediate concern was that of death to all the butterfly larvae that would also be around at the time of spraying and also for those with respiratory issues. Spraying into the air is different than treating water.  

Residents in the affected areas throughout the province were mailed a card with notice of a virtual Open House where questions could be asked about the spraying. In order to satisfy my curiosity and to justify the killing of innocent butterflies I phoned and satisfied myself for now, with the answers.

This is what I was told. The goal of the spray program is to eradicate and not just control. I could not understand such defined limits for spraying within the communities. Apparently the moths are big and heavy, up to 6cm long, do not travel great distances and so it is felt they do not not exist out of those limits. They must have been brought in to the area of infestation.  It is therefore felt they can be eradicated. The moths are unfortunately now established in Ontario and some jurisdictions do not treat any more. I had read the eggs, which are how the moth overwinters, cannot survive temperatures below -28C. As we had very cold temperatures this winter in parts of B.C I wondered if that would have killed the eggs. Apparently the eggs are frequently laid in crevices and cracks, which may well not get as cold and it cannot be guaranteed they were killed. The eggs are very distinctive being wrapped in a hairy bundle for protection. The Spongy Moth and eggs can be irritating if touched. I asked about natural predators of which there are some, but those predators would also attack butterfly larvae.

Unfortunately for those with respiratory issues they will be asked to remain indoors during spraying, which will happen in early morning.  

I always have a difficult time with the issues of invasive species because we ourselves have been invasive over time spreading our populations around the world. Rabbits, Starlings Spotted Knapweed, Dandelions, Japanese Knotweed, rats, lizards are called considered invasive somewhere. Drawing the line between nuisance and dangerously invasive is difficult and how long will it be before the establishment of some of these invasives is just accepted as with Dandelions and the Spongy Moth in Ontario?   I don’t envy those making these decisions because no matter what they do, someone is likely to object. I understand the rationale and I am satisfied with the answers but I am sad that we humans cause so many of these problems ourselves.

All images from various reliable sites including the Michigan Invasive Species, Don’t Move Firewood.org, Invasive Species Center.

How can we as individuals help? If we can recognize the eggs and when we spot them and destroy them by burning or immersing in soapy water, it would help. If pheromone traps become available and we use them in our deciduous trees, it might reassure us in knowing the Spongy Moth is not around or if we detect one, it will give an early warning. Notifying authorities of course would be important.

I am curious about the status of the Spongy Moth in Alberta. One source I read said it had been eradicated but it also said the same about the moth in B.C!

Government websites have a lot of information. You can read a how many of these moths were trapped in different areas of BC here:

The Government website has a lot of information.