What You Need to Know About Egg Masses

What is an Egg Mass?

Egg masses are a protective structure around insect eggs that can come in many different varieties to protect the eggs from weather or predation. Some egg masses, like a spongy moth egg mass, can hold up to 1,000 eggs, making them of particular concern for the spread of invasive insects.

Examples of invasive insect species which form egg masses include:

Spongy moth
Spotted Lanternfly

Other insect species form similar structures that may hold both the eggs and adult insects. For example, Hemlock Woolly Adelgid forms white “woolly” sacs resembling tiny cotton swabs which hosts both eggs and adults.

Egg masses and other structures can be a good indicator to look for to detect invasive species infestations as they are often more visible than individual eggs or small insects (such hemlock woolly adelgid). They also hold several individuals and therefore may pose a greater invasive threat than a single egg or insect.

Here are a few insect species you can look out for.

Spongy Moth

The spongy moth (Lymantria dispar dispar) is native to Europe and is currently established in northeastern United States and eastern Canada, including portions of Ontario, Quebec, New Brunswick, Prince Edward Island and Nova Scotia. The larvae (caterpillars) feed on crown foliage of a wide range of hardwood and some softwood trees, which makes it a defoliating forest pest of concern.

Spongy Moth Egg Masses

Egg mass description: Tanned yellow, covered with fuzz and about the size of a quarter. The texture can be compared to that of a tennis ball.

Where to find them: Spongy moth prefers to lay its eggs on oak trees but eggs can be found on other hard surfaces during outbreaks when the population is large. Spongy moth eggs are laid in mid-late summer and will hatch in early spring of the following year.

Spotted Lanternfly

Spotted lanternfly (SLF; Lycorma delicatula) is a planthopper native to Southeastern Asia that has become an invasive insect pest in the United States. While the invasive tree-of-heaven (Ailanthus altissima) is a preferred plant host, SLF is known to feed on a wide range of native hardwood and fruit trees. Grapevines are particularly vulnerable to SLF, which feed on them in large swarms. If this species spreads to Canada, it could be a formidable threat to various industries and the economy, including the horticulture, tender fruit and grape product industries.

Spotted Lanternfly Egg Masses

SLF egg masses
Image credit (both images): Emelie Swackhamer, Penn State University, Bugwood.org

Image from: Survey Protocol: Spotted Lanternfly by the Canadian Food Inspection Agency

Egg mass description: grey, muddy-looking secretion, arranged vertically

Where to find them: SLF egg masses can be laid on almost any natural or artificial hard surface occurring outdoors such as wood, vehicles, and outdoor furniture. If you’ve visited an area where spotted lanternfly is present, remember to check your vehicle before leaving. Females will lay their eggs between September – December and the eggs will typically hatch in June the following year.

Hemlock Woolly Adelgid

Hemlock woolly adelgid (HWA) is an aphid-like insect (aphids suck fluid from plants) that attacks and kills hemlock trees by feeding on nutrient and water storage cells at the base of needles. Researchers believe HWA was first brought to the United States via infested nursery stock from Japan. HWA can cause significant changes to hemlock ecosystems, impacting both living communities of flora and fauna and ecosystem services.

Insect structures: Woolly sacs at the base of hemlock needles on underside of most recent twigs; these contain not only the eggs but the adult insect as well

Where to find them: The “wool” is most conspicuous on the undersides of branches from fall through spring. There are many detection methods available to help identify HWA in the crown of mature trees, one example of this is Ball Sampling for HWA.

Learn about other sampling methods here.

What Can You Do?

Report it! – Early detection and response are especially important to successfully managing an invasive species. Record where you saw the species and, if possible, take photos of the species and its location using EDDMapS or iNaturalist.

EDDMapS is a web-based mapping system for documenting invasive species distribution. It is fast, easy to use, and doesn’t require Geographic Information Systems experience. You can report on the website or using the EDDMapS mobile app. 

INaturalist is an online social network where people share biodiversity information to help each other learn about nature. It serves as a crowdsourced species identification system and an organism occurrence recording tool. You can report invasive species here using their website or mobile app.

The Canadian Food Inspection Agency (CFIA) collects data on priority pests such as SLF, spongy moth and HWA. Sightings of these priority pests should also be directly reported to CFIA.

Use the Tree Check Form – The tree check form provides a simple guide for what to look for when you are surveying trees in your community. Each survey has room for up to three reports, each of which can be used for a different type of tree.

Pile of firewood rotated isolated on white background

Don’t Move Firewood – Burning firewood in the same location where it was purchased is one of the surest ways to avoid spreading any invasive insects.

Here is some guidance from the Canadian Food Inspection Agency to keep in mind:

Buy and burn your firewood locally. Transporting wood long distances can lead to a free ride for invasive species of all sorts across Canada.

Know where the wood is coming from. If you buy wood from a local supplier, don’t be afraid to ask where it came from. Buy wood that was cut less than 80 km away from where it is being sold. A good rule of thumb is to limit your radius to 15 km if possible.

Don’t “judge a book by its cover”. Just because you can’t see signs of pest infestation doesn’t mean the pests aren’t there. It can be extremely difficult to notice insects, insect eggs and fungal spores on wood.

Spread the word, not the bug. Tell your family, friends and colleagues how to protect forest health by burning firewood where they buy it to prevent the spread of invasive pests.. If you are having people over for a fire in your backyard or at your campsite or going on a camping trip, make sure those who are joining you are aware of this threat.

Learn more

Egg Mass Scraping – Spongy Moth and Spotted Lanternfly

Spongy moths lay tanned yellow, spongy masses, which have a texture compared to the felt of a tennis ball and typically contain 100-1,000 eggs. If you find an egg mass, snap a picture and report the sighting to EDDMapS or iNaturalist, or call the Invading Species Hotline at 1 (800) 563-7711. Then, follow the Scrape – Soak – Scrap Method:

Use a scraper, such as a butter knife, to carefully remove the mass. Always wear gloves and protective glasses and take caution if scraping from a ladder.

Soak the masses in a bucket of dish soap and water mixture for 48 hours.

Dispose of the egg masses.
Learn more

Spotted lanternfly egg masses look like a smear of grey-brown mud and can be found on virtually any hard surface outdoors in the fall and winter. If you spot one, follow the Snap It – Catch It – Report It Method:

Snap a clear picture.

Scrape off the egg masses into a plastic bag filled with hand sanitizer or rubbing alcohol, and seal it. Egg masses can also be stored in the freezer if hand sanitizer or rubbing alcohol is not readily available.

Then, report it as soon as possible to the Canadian Food Inspection Agency with its precise location.

Hemlock Woolly Adelgid Monitoring Network – The Hemlock Woolly Adelgid (HWA) Monitoring Network was initiated to increase early detection of HWA outside of known distribution and regulated areas. This program is coordinated by Invasive Species Centre, in partnership with Natural Resources Canada (NRCan) and the Canadian Food Inspection Agency (CFIA). It empowers community members to monitor for HWA using novel 3-D printed insect traps. Visit the website to learn more about upcoming opportunities to get involved.