*The Latin name for the European Gypsy Moth is Lymantria dispar dispar (LDD). Note we are transitioning to the term LDD moth following the announcement officially dropping the name “gypsy moth”.

What is the LDD moth

The LDD moth is an invasive and destructive pest that severely defoliates deciduous and coniferous trees and poses a risk to tree health. Caterpillars, which hatch in April to June, pose the largest threat to our tree population since they eat leaves. During severe outbreaks, large populations can completely defoliate trees and shrubs. While some trees can produce new leaves over the summer, the damage caused by losing their leaves can reduce their growth. Repeated defoliation causes affected trees to lose their strength and can eventually lead to tree death.

The LDD moth goes through various life stages. LDD moth egg masses overwinter on the bark of trees and other hard surfaces. In the spring, eggs hatch and caterpillars feed on leaves. By the time the caterpillars are mature in July, feeding is complete. Mature caterpillars transition to short-lived moths in July and August to reproduce and lay their spongy egg masses. Up to 1,000 LDD moth caterpillars can hatch from a single egg mass.

What can you do

Depending on the time of year and life stage there are several options to control the LDD moth. Always wear gloves when handling the caterpillars because their hairs can cause skin irritation.

Destroy egg masses

From August to mid-April, you can destroy egg masses to prevent LDD moth damage on your property. Egg masses can be found on tree trunks, branches, rocks, fences, and other hard surfaces. Scrape the egg masses into a container of soapy water and soak for one week before disposing.

Burlap band

From mid-May to June, use twine to loosely tie the burlap to the tree so that the top of the band hangs over the bottom. The burlap band acts as a hiding spot for caterpillars during the day. Check the bands daily and dispose of any caterpillars in a bucket of soapy water.

Hand pick

From July to August, pick pupae by hand with gloves and dispose into a bucket of soapy water. Soak the pupae for one week before disposing.

Biological control

From mid-April to mid-May, you can apply the biopesticide BTK (Bascillus thuringiensis) on leaves. BTK is a bacterium found naturally in the soil that is poisonous to the larvae once ingested. Use BTK under your own discretion and call a licensed contractor for application. Private landowners may arrange an aerial spray application of BTK by a licensed applicator.

Natural population control

Over the next several years we can expect the current LDD moth outbreak to naturally collapse thanks to predators and pathogens. For example, NPV (nuclear polyhedrosis virus) is a viral infection that spreads quickly through large populations. The larger the population of LDD moths, the easier it is for NPV to spread and cause a population to collapse. There is also a fungus (Entomophaga maimaigi) that has been introduced to control populations of LDD moths. Infections are more likely to spread in a wet spring.

LDD moths in Lanark County

We are providing education and awareness about the LDD moth and how to reduce infestations on your property through Facebook (@LCClimateAction), factsheets, outreach, and more.

We are not actively managing LDD moth populations. Not managing pest populations is a common, practical approach because pest outbreaks come and go naturally. This is largely due to predators, parasites, and pathogens that decrease LDD moth populations and leads to their eventual collapse.

Additional resources

LDD Moth Factsheet

LDD Moth Egg Mass Scraping Challenge 2021

What to expect and what to do with the LDD moth for the summer of 2021


Invasive Species Centre

Eastern Ontario Model Forest

Government of Ontario

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