Spongy Moths

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)

Does the Township of Warwick do an aerial spray for Spongy Moths?

Currently, the Township of Warwick does not do aerial spraying for Spongy Moths.

What can I do to protect my property?

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.

Spongy Moth Lifecycle

Gypsy Moth life stage and control options

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.

What kinds of trees are most affected by the Spongy Moth caterpillar?

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.

Spongy Moth Damage

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.

Does the Spongy Moth have any natural enemies?

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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