Spongy Moth

Spongy Moth (Lymantria dispar)

Report

Photo Credit: Gyorgy Csoka, Hungary Forest Research Institute, Bugwood.org

Management Category

ID Characteristics

The appearance of Spongy Moths varies depending on their sex. Both sexes have pectinate antennae (antennae that look like a comb) and crescent-shaped markings on the front of their wings (forewing).

Adult Female: Creamy white and much larger than males, with a 55 – 70 mm wingspan. Adult females can’t fly.

Adult Male: Light to dark brown, with a smaller wingspan (37 – 40 mm). Males have feathery antennae and are strong fliers.

Eggs: Each egg mass contains 100 – 1000 eggs. Egg masses are about 30 – 60 mm long and 20 – 30 mm wide. They are covered with the tan-coloured hairs of the female’s abdomen.

Caterpillars: Dark brown and hairy, with rows of red spots at the head and blue spots at the tail end. They can grow up to 60 mm long in maturity.

Habitat and Origin

Introduced from Europe to North America in 1869, possibly for silk production. Spongy Moth was first recorded in BC in 1978.

Found throughout the Eastern U.S. and parts of Ontario and Quebec; small populations have also been found in the Western U.S. Additionally, small populations have been observed in New Brunswick, Nova Scotia and BC. Aggressive monitoring and control measures are in place to prevent further introduction.

Caterpillars feed on leaves within the crown of healthy trees. Forested areas are common habitats, specifically oaks, birches, maples, white pines and white spruces, but they feed on over 500 species of trees and shrubs. Egg masses are laid close to where the female transformed into an adult (pupation), on trees, rocks, tires, trailers or firewood.

Reproduction

Since adult females cannot fly, they lay one egg mass near where they transformed into adults (i.e., where they emerged from pupation). The eggs hatch in spring, leaving pin holes in the egg mass.

The caterpillars feed until mid-summer before seeking shelter to pupate. There, they transform into adults within a reddish-brown cocoon; this process is called pupation.

The adults emerge between late July and late August to mate and lay eggs. They only live a week, and don’t feed.

How it Spreads

Egg masses are laid on several objects including firewood, tires, and trailers. Spongy moths spread easily when these objects are moved.

Impacts

Ecological:

Larvae feed on over 500 species of trees and shrubs.
Larvae can completely defoliate trees; this can kill trees, including endangered Garry Oak trees.

Economic:

Spongy Moths damage forestry and tree nursery industries, as well as residential properties.
Attempts to stop the spread of Spongy Moths cause quarantines and trade restrictions.
Spongy Moths threaten fruit producers by attacking fruit trees and blueberry plants.

Health:

Caterpillar hairs can cause allergies, with symptoms like skin rashes or respiratory problems.

Prevent the Spread

Spongy Moth has been observed around ISMAs 1 and 2 (Squamish and Whistler), but not in the north of the region. PREVENTION of further spread and new introductions is key.

Regularly monitor properties for the hairy, tan-coloured egg masses of the Spongy Moth.
Look closely at your vehicle, patio furniture, tarps, garden items, and sports equipment and ensure that the underside of your things is free of egg masses.
Buy Local, Burn Local. Do not move firewood from one location to another. This will avoid spreading egg masses accidentally.
If you are travelling, check your camper, trailer or RV before and throughout the trip.

Control

Mechanical Control:

Remove or scrape off egg masses, larvae, caterpillars or moths. Destroy them by soaking them in hot soapy water for at least two days, then place them in your household garbage. DO NOT COMPOST.

Biological Control:

BC is conducting an aggressive program to eradicate Spongy Moth. Adults are trapped and trees are sprayed with a biological insecticide called BtK (Bacillus thuringiensis) in areas where moths are found. BtK kills the larvae before they mature and reproduce. There are also parasites and birds that attack the larvae.