In the summer of 2020, many millions of spongy moth (Lymantria dispardispar, 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.
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.
Hand picking and removing spongy moth 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 spongy moth population while protecting the natural heritage systems that we all depend on.
Noah Cole is Ontario Nature’s communications technician and a regular contributor to Ontario Nature's blog and ON Nature magazine. Noah is an accomplished naturalist with a passion for protecting the great outdoors and a nature photographer. Noah is the author of Ontario Wildlife Photography (canadianimages.net).