The population of the European Spongy Moth has been increasing in Ontario since 2019. The result of this outbreak has caused extensive defoliation of targeted trees and a significant impact on individual enjoyment of outdoor settings.
Frequently Asked Questions (FAQs)
It is the property owners' responsibility to manage trees (and pests) on their property. It is recommended that you monitor trees on your property. You can look for egg masses during the winter, caterpillars in the spring, and moths in July and August. Spongy moths can be managed by a number of different actions throughout its life cycle.
Check out the Ausable Bayfield Conservation Authority fact sheet for helpful information on controlling the pests throughout its lifecycle.
Many local landscape and tree companies also offer a variety of tree health services. This includes tree climbing, pruning and removal, deep root fertilization, systemic insecticide tree injections, and ground-based spraying among other things.
Previously called the 'Gypsy Moth', it is now known as a Spongy Moth.
| Timing | Life stage | Control options |
|---|---|---|
| August to Mid-April | Egg Masses | Remove egg masses and discard. |
| Mid-April to Mid-May | Early Stage Caterpillar | Apply biological pesticide. |
| Mid-May to June | Late Stage Caterpillar | Attach burlap bands and discard larvae. |
| June to Mid-July | Pupae | Remove by hand and discard. |
| July to August | Adult Moth | Short-lived; focus on other stages. |
According to Ministry of Natural Resources and Forestry, defoliation caused by the spongy moth was most severe in wood lots containing species of:
- Oak;
- Maple;
- Poplar;
- Willow; and
- Other broadleaf trees
In some areas, the spongy moth defoliated conifer species including eastern white pine.
The damage a spongy moth can cause depends on a number of factors, including:
- Past defoliations;
- The tree’s vulnerability;
- The degree of infestation; and
- The environment.
The tree's damage might range from minor to severe defoliation. When a tree has been weakened or stressed by other factors, and has been defoliated repeatedly in successive years, it dies.
Many attacked trees see regrowth of leaves later in the season.
Yes. Birds, mammals, and other insects are know to prey on the spongy moth. These animals include:
- Chickadees, blue jays, robins, and nuthatches;
- Chipmunks, squirrels, and raccoons; and
- Wasps, flies, beetles, ants, and spiders.
There is a species of wasp that is known to parasitize spongy moth eggs. It is commonly found wherever spongy moths are and can reduce the spongy moth population.
Also, the spongy moth is susceptible to several naturally occurring diseases caused by bacteria, fungi, and viruses. The virus and bacteria escalate when spongy moth populations peak. The spongy moth virus disease is often referred to as, “wilt” because dead caterpillars hang in an inverted, “V” from tree trunks or foliage.
These natural biological controls contribute the most to keeping levels within a normal range and tend to become more prevalent as the spongy moth populations peak.
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