Saturday, August 16, 2014

Look for Gypsy Moth Egg Masses In August

Please, if you have any hardwood shade trees on property you own, or property you frequent, take a look at this photo.
Beige, almost cotton-like, fuzzy masses are on hardwood shade trees right now.

These are egg masses laid by the Gypsy Moth (Lymantria dispar dispar) . It's an invasive species of moth (brought over from Europe) which can devour and devastate tree canopies all over the GTA. Eventually, when populations of Gyspy Moth get out of control, they weaken trees and reduce our tree canopies in urban situations.

August is the time Gypsy Moth lay their eggs. I've seen egg masses 6 inches to 10 feet off the ground on nearly all sides of a tree's trunk. It's been said the Gypsy Moth favours the south-east side (more protected) but not always.
Here, the mass has been placed approximately 10 inches off the ground level.

You may not see an egg mass, but instead the pupae skin remaining. This means the adults are close and perhaps in a few days masses will show up on the tree.

Here, below the egg masses (by the raised bark) you see pupae cocoons nestled on the trunk of a Gledistia (Honey Locust).

I just wore gloves and wiped the masses off. Simple. Remove any pupae too. The egg masses have a hairy fibre which has been known to irritate bare skin. So don't use your bare hands.

Each mass must have100 eggs, if not more. Fibrous, paper like vomit covers the eggs in a protective mass, incredibly making them safe for overwintering. Quite remarkable, really.

I was lucky, I found this female Gypsy Moth - having just laid her mass of eggs. Females are flightless, so she just sat there while I grabbed the camera. Pale beige/white in comparison to the male moth, she is larger and will die shortly after laying the eggs.

On this walk alone, I found masses on young trees, 50ft trees and even small fruit trees. Cultivars as: Tilia (Linden), Gleditsia (Honey Locust), Quercus (Oak), Malus (Apple) and Acer (Maples).

Don't be afraid or grossed out. If you see a mass, just take a leaf from the tree or a small stick and squish the soft mass of eggs and wipe away from trunk. You'll be doing the trees a big favour and the environment.

The tree will THANK YOU by having lovely, intact leaves next May-June (when the caterpillars emerge to feast). If we do this more often, less chemical and biological controls need to be sprayed from helicopters above.

Have a look at the Invading Species website for more info on the Gypsy Moth.


  1. Thanks for the info! I'll check out the trees on my property.

  2. Thank you, well explained with photos. We just found our first eggs on an oak tree. Will scout our property for more.


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