LDD Moths

Gypsy Moth Caterpillar Lymantria dispar dispar (formerly known as gypsy moth), are a forest defoliating insect found in Ontario. The Lymantria dispar dispar (LDD Moth) populations have been increasing in Ontario since 2019 with an obvious outbreak evident in areas of Lambton Shores in 2020.  

In the summer of 2021, the area of Lambton Shores most affected was the Highway 21 corridor between Port Franks and Grand Bend, including the large forest blocks in the Pinery Provincial Park, the Lambton County Forest and the Ausable Bayfield Conservation Authority.  These areas contain large populations of oak trees.

The Government of Ontario has released the Defoliation Forecast for 2022 and the Lambton Shores area is not expected to experience the same severity as previous years. Residents are encouraged to monitor their property and we have included several resources below for more information about LDD and what can be done to further protect your property.

Frequently Asked Questions

Was there an aerial spray for LDD Moth in 2021?

In the spring of 2021, there was a community-led effort to have Zimmer Air Services spray for LDD Moth in Lambton Shores. To support those efforts, Council committed to and completed: 

  • Adding an LDD Moth information page to the municipal website
  • Alerting all property owners by mailing out LDD Moth information
  • Waiving any objection to BTK spray
  • Coordinating permissions needed by other levels of government
  • Putting money in the 2021 budget to control LDD Moth on municipal property

On May 31, 2021, Zimmer Air Services Inc. advised the Municipality that their 2021 Aerial Spray Program for the control of LDD Moth in Lambton Shores was complete.

What is BTK spray?

Baccillus thuringiensis subspecies kurstaki pesticide (Btk) is a bacterium found naturally in soils. It has been used worldwide as a biological pest control agent to combat a group of insects called lepidopterans (which include the LDD Moth) in forestry and agricultural settings. Btk is also approved for residential and commercial use including aerial application over residential areas.

According to Health Canada, Btk poses little threat to human health either through handling products directly or through indirect exposure such as aerial spraying.

Lambton Public Health has no public health-based objections to aerial spraying of Btk as part of a moth control plan provided that the rules of application as outlined by the Pest Control Products Act and other applicable federal or provincial legislation are strictly followed.

More information about Btk in Lambton Shores.

What can I do to protect my property?

Property owners are responsible for managing trees (and pests) on their property. You are encouraged to monitor trees on your property.  Look for egg masses during the winter, caterpillars in spring, and moths in July and August. There are a number of actions that you can take to control LDD Moth at all stages of its life cycle.

The Ausable Bayfield Conservation Authority provides helpful information for controlling the pest throughout its lifecycle in this factsheet: ABCA Factsheet 

Are there other Control Measures to deal with the LDD Moth?

The Ausable Bayfield Conservation Authority provides helpful information to homeowners as an alternative (or addition to) aerial spray programs in this factsheet: ABCA factsheet

There are many local landscape and tree companies that also provide various tree health services. This includes tree climbing, pruning and removal, deep root fertilizing, as well as systemic insecticide tree injections and ground based spraying.  Although not an endorsement of any particular service the following list of companies may be considered:

What is the LDD Moth lifecycle?  

LDD Moth spend the winter as partially developed larvae in eggs. The eggs hatch in the spring and the young larvae begin feeding by cutting small holes in the surface of leaves. As the larvae develop, they feed on the edge of leaves. Larvae have five pairs of blue and six pairs of red spots along their backs. Feeding is normally completed by early to mid-July.

Emerged Caterpillars Ausable Bayfield Conservation Authority (2020) - Click to enlarge the image   Gypsy Moth Larvae - Forest Health Monitoring Program, MNRF (2019) - Click to enlarge the image   European Gypsy Moth Male (brown) and Female (white) - City of Toronto - click to enlarge

Pupation occurs in a cocoon which can be found on a variety of surfaces including trees, rocks, houses, boats, trailers, fences, picnic tables, and firewood. In 13 to 17 days, the moths emerge. Both sexes have wings, but only the males can fly. The male moth is dark brown to beige, medium-sized, and is a very erratic flyer. The female is mostly white and has a wingspan between 60 to 70 mm. The female lays eggs in masses of 100 to 1000 on tree trunks, branches, houses, fences, etc. as well as under rocks and forest floor debris. The eggs are covered with fine brown hairs from the female’s abdomen. The egg masses will remain all winter and caterpillars will hatch in the spring, from late April to mid-May.

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

According to the Ausable Bayfield Conservation Authority, Oak, Aspen, Birch and Basswood are the tree species in our area that are preferred by the LDD Moth. However, depending on a variety of conditions, including high populations, the LDD Moth will eat whichever tree species is available. 

How much damage can LDD Moth cause trees? 

Tree damage depends on a number of factors including:

  • The degree of infestation
  • Past defoliations
  • The tree’s vulnerability, and
  • The environment.

Damage to the tree can range from light, to almost complete defoliation. Death to a tree occurs in cases where a tree has been weakened or stressed by other conditions, and defoliated repeatedly in successive years.

Many attacked trees see regrowth of leaves later in the season.

Does the LDD Moth have any natural enemies?

Yes. Predators include other insects like wasps, flies, beetles, ants and spiders as well as birds such as chickadees, blue jays, robins and nuthatches. Animals such as chipmunks, squirrels and raccoons will also prey on the caterpillar.

The wasp that targets the LDD Moth is a parasite of the LDD Moth egg. It is now commonly found where ever LDD Moth is and has become an important natural control of the LDD Moth.

Also, the LDD moth is susceptible to several naturally occurring diseases caused by bacteria, fungi and a virus. The virus and bacteria escalate when LDD Moth populations peak. The LDD 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 LDD Moth populations peak.

Additional Links

The links below provide additional information about the LDD Moth caterpillar.

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