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

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

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 spongy moth was most severe wood lots containing species of:

oak
maple
poplar
willow
other broadleaf trees

In some areas, gypsy moth defoliated conifer species including eastern white pine.

Damage that a Spongy Moth can cause

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. Such as:

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 populations.

Also, the spongy moth is susceptible to several naturally occurring diseases caused by bacteria, fungi and a virus. 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.

Helpful links