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© Lora Denis
In the summer of 2020, many millions of spongy moth (Lymantria dispar dispar, LDD) caterpillars emerged across Ontario, causing ecological concern from North Bay and Sault Ste. Marie to Windsor and Ottawa. In the summer of 2021, the species commonly named as gypsy moth was renamed spongy moth. The former common name of the species changed because it was derived from a culturally offensive slur.
The species was introduced to eastern North America from Europe in the late 1800s through a failed attempt to harvest silk from spongy moth 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 spongy moth caterpillars. 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 spongy moth 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 spongy moth 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 spongy moth 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 will also eat the larva, pupae and adults. American and Fowler’s toads regularly consume spongy moth 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. Spongy moth 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. Spongy moth outbreaks tend to occur every five to seven years.
The City of London has identified effective ways property owners and managers can moderate spongy moth populations without significantly disturbing the natural environment. These methods include:
Together we can control and decrease the invasive spongy moth population while protecting the natural heritage systems that we all depend on.
2021 is another active boom year for these Lymantria dispar dispar (LDD) moths and caterpillars. The scientific name also refers to the Latin word for “destroyer” so, these moths are becoming colloquially informally referred to as “The Destroyer” moths now too. To help remedy infestations in the caterpillar stage, it can be helpful to dissuade and prevent the caterpillars from climbing trees before they turn into moths by wrapping the base of trees with several layers of burlap so the caterpillars may have a harder time climbing the trees and gather beneath the burlap, often in sizable groups, before cocooning themselves and metamorphizing into breeding moths. These caterpillars tend to drop when they get wet or sprayed with hose, that can also help in removing them from a tree. And you could also collect them in a soapy water filled bucket to get rid of them as well in caterpillar stage. This action will help to remedy and prevent further local infestations, even if your own actions help your own yards.
If affected trees are within reach of an extension cord, I used a shop vac last fall to collect hundreds of egg masses around my property. Very fast, easy and I also used a 8 foot extension tube to reach masses on overhead tree trunks. Once finished I soaked the vac bag in soapy water before disposal.
Good luck one and all!
I also had a nasty infestation of these little ones on my Oak tree last summer. I wrapped burlap around the trunk about 4-5 feet off the ground and collected hundreds of them. The leaves did come back and the tree looked normal later in the summer. As an experiment I collected some egg masses in January and put them in a small terrarium. Well in 2 weeks they hatched. Can’t believe how many there are. I see some egg masses on the Oak and will remove them as best I can later when the weather gets warmer, but before they hatch. Here’s hoping for the best this spring. Stouffville, Ontario
I wrapped my trees with a strip of burlap wrapped circumference of truck (fold over rope and draped a foot or so) where the caterpillars sheltered during the day time away from the sun – scrapped the caterpillars into soap water – hoping this will help diminish next years invasion a bit – and also scrapped any egg masses into soapy water – also ensure there’s no foliage at the base of the tree also for the buggers to hide
Thank you Gwen, your tip sounds practical and useful. People may be glad to know they can use burlap with rope to help block caterpillars from climbing the trees and may be glad to use that in addition to scraping egg masses into soapy water. Smart ideas!
I have scraped pails of eggs, sprayed upper clusters with soy bean oil and am still bracing for a major assault this spring . I have seen an enormous amount of egg clusters on my property which consists of 50 acres of mostly hardwoods. My yard is treed with mature oaks and spruce which I planted as small trees 45 years ago.The oaks were about 75% defoliated this year and the spruce about 25%. Unless I take drastic measures I am concerned I will have a dead tree wasteland.I have made a small dent in the clean up of the emerald beetle aftermath and cringe at what may follow. I can see no choice but to invest in applying a bacterial control this spring. This was done this past year by the GrandRiver Conservational Authority at Pine Hurst Lake. I am concerned that there is not more govt interest in the gypsy moth problem given the benefits of our forest in carbon capture
We spent hours squashing Gypsy moth caterpillars this summer, and recently have scraped hundreds of egg masses off our birch, pine, spruce and oak trees. However, the trees on this 1.5 acre property are mature and very tall. I can see egg masses up high, but have no way of reaching them. Do you have any suggestions? We bought bands and sticky material from Lee Valley, but the egg masses are above where we can reach to attach the bands. Any help would be most appreciated.
Thanks for asking!
It is, of course, difficult for most people to get up to the upper branches. I am not certain which techniques you have used. You could perhaps try using a pole to reach higher up and scrape available eggs masses. There is also some further relief in that wildlife such as ants and birds such as woodpeckers and chickadees, mentioned in the blog also do control and eat from egg masses. Like yourself, I alos spent time removing Lymantria dispar dispar (LDD) egg masses from our yard this year.
Majority of my trees are over 60 feet tall. I guess the egg masses up there are unapproachable. Do the caterpillars come down the trunk as night appears and then crawl back up. I noticed the congregate around the trunk base shielding from sun. I live rural and have over 2.5 acres trees.
In the blog, I mention that in fall and winter you can remove LDD egg clusters by scraping them into a bucket of soapy water. This fall, I have removed 30 locally (around 3000 LDD eggs!!). Now is the perfect time to remove these egg clusters while the weather is mild and there isn’t much rain or snow on the branches.
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.
Is it effective to just brush the egg masses down to the ground or does one need to do more to kill the eggs?
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?
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.