This summer, many millions of gypsy moth (Lymantria dispardispar, LDD) caterpillars have emerged across Ontario, causing ecological concern from North Bay and Sault Ste. Marie to Windsor and Ottawa.
The species was introduced to eastern North America from Europe in the late 1800s through a failed attempt to harvest silk from LDD cocoons.
These invasive caterpillars damage native trees and shrubs, destroying habitat and food sources for wildlife by consuming foliage including oaks – the preferred host plant for LDD. Rural and urban areas are teeming with the caterpillars, which disturb residents with vast quantities of caterpillar feces and by covering external walls with dense infestations as larvae look for sites to turn into moths.
Spraying noxious pesticides to control L. d. dispar caterpillars is controversial. It is detrimental to the environment, contaminates watersheds, and is harmful to pollinators and other wild animals (e.g. amphibians, birds and fish).
Supporting habitat and healthy habitat for local wild species that predate L. d. dispar could be helpful both for the wild species themselves and biodiversity more broadly by controlling LDD populations.
Chickadees will eat all life stages of the L. d. dispar. Blue jays, eastern towhees, red-eyed vireos, grey catbirds, Baltimore orioles and black-billed and yellow-billed cuckoos will eat LDD larva and adults. Indigo buntings consume hairy caterpillars including those of LDD. Robins are an effective predators of these larva, pupae and adults too. White-footed mice also eat LDD larva, pupae and adults. American and Fowler’s toads regularly consume L. d. dispar larva and adults. Interestingly, carpenter ants will also eat the pupae and eggs of this moth.
L. d. dispar overwinter in the egg stage on tree bark or buildings. Eggs hatch and larvae seek foliage to consume in spring. LDD larvae mature in July and often grow to be five centimetres long, at which point they metamorphize into pupae. Moths emerge and mate mid-summer and then lay egg masses on trees and sheltered areas. LDD outbreaks tend to occur every five to seven years.
Hand picking and removing LDD caterpillars May through July;
Burlap wrapping to remove larvae and adults June through August;
Using pheromone traps to attract male moths in July and August; and
Destroying egg masses from November to April.
Together we can control and decrease the invasive Lymantria dispar dispar population while protecting the natural heritage systems that we all depend on.
An accomplished naturalist with a passion for protecting the great outdoors, Noah Cole is Ontario Nature’s communications technician.
Our neighbourhood in Scarborough has a lot of gypsy moth egg on the birch trees. Can we hire someone to spray the trees as they moth pods are quite high up?
We have a cottage on the severn river (Big Chute). Many cottages would like to plane spray the bay next spring. What is your department’s position on spraying in this area. I think it might be to early as there is minimal evidence / sightings.
As recommended in the blog, the City of London website suggests scraping the egg masses off with an object such as a butterknife or a paint scraper, containing the egg masses in a bucket, and then keeping those egg masses in a bucket of soapy water for a couple of days then disposing the content.
I think letting the egg masses fall to the ground will not ensure that they do not hatch later in the spring.
Over the course of this past winter, I made 8 excursions through our woods, scraping off and catching and then burning a total of approx. 6 pounds of gypsy moth egg masses. That’s a lot of eggs. And I thought it would make a lot of difference.
But the damage this spring could hardly have been more extensive.
Now, the deciduous trees have been producing new leaves. Whether they can survive another back-to-back year of stripping is questionable.
But as to the conifers. A beautiful high-ground stand of 60-to-80 ft. white pine and hemlocks have been stripped bare, and their poor skeletons are showing no signs of new needles coming. Indeed, one reliable source has it that evergreens just simply die, then and there.
The birds and other wildlife who feed on these caterpillars were not nearly numerous enough to make a difference this year. And with egg masses this summer multiplying exponentially over last year’s, I wonder what hope we can have for the remainder of our trees, and the survival of the millions of species whose lives depend on the survival of such woodland habitats?
Very good article!
Myself and others are noticing brown moths who try to land on us during the day in the Ottawa, Ontario area. Are these Gypsy Moth males? Why do they want to land on us?
Thanks,
Jane
They may be male Lymantria d. moths (formerly referred to as gypsy moths, but due to derogatory and offensive nomenclature it is best to refer to these moths as Lymantria dispar) , which often do fly during the day and live for about a week.
Our neighbourhood in Scarborough has a lot of gypsy moth egg on the birch trees. Can we hire someone to spray the trees as they moth pods are quite high up?
We have a cottage on the severn river (Big Chute). Many cottages would like to plane spray the bay next spring. What is your department’s position on spraying in this area. I think it might be to early as there is minimal evidence / sightings.
Thank you
D’Arcy
Is it effective to just brush the egg masses down to the ground or does one need to do more to kill the eggs?
Hi Beth,
Good question.
As recommended in the blog, the City of London website suggests scraping the egg masses off with an object such as a butterknife or a paint scraper, containing the egg masses in a bucket, and then keeping those egg masses in a bucket of soapy water for a couple of days then disposing the content.
I think letting the egg masses fall to the ground will not ensure that they do not hatch later in the spring.
ON Noah
Over the course of this past winter, I made 8 excursions through our woods, scraping off and catching and then burning a total of approx. 6 pounds of gypsy moth egg masses. That’s a lot of eggs. And I thought it would make a lot of difference.
But the damage this spring could hardly have been more extensive.
Now, the deciduous trees have been producing new leaves. Whether they can survive another back-to-back year of stripping is questionable.
But as to the conifers. A beautiful high-ground stand of 60-to-80 ft. white pine and hemlocks have been stripped bare, and their poor skeletons are showing no signs of new needles coming. Indeed, one reliable source has it that evergreens just simply die, then and there.
The birds and other wildlife who feed on these caterpillars were not nearly numerous enough to make a difference this year. And with egg masses this summer multiplying exponentially over last year’s, I wonder what hope we can have for the remainder of our trees, and the survival of the millions of species whose lives depend on the survival of such woodland habitats?
Very good article!
Myself and others are noticing brown moths who try to land on us during the day in the Ottawa, Ontario area. Are these Gypsy Moth males? Why do they want to land on us?
Thanks,
Jane
Hello,
Thank you Jane.
They may be male Lymantria d. moths (formerly referred to as gypsy moths, but due to derogatory and offensive nomenclature it is best to refer to these moths as Lymantria dispar) , which often do fly during the day and live for about a week.
ON Noah