About spongy moth
This moth lays hundreds of eggs in a single mass. The egg masses then hatch, releasing hundreds of hungry caterpillars. These caterpillars can strip the leaves from entire trees, devastating stands of trees.
The spongy moth mostly lives in Europe, Russia, China, Korea, and Japan. It turns up in all sorts of places, like the western coast of North America. Although it has been eradicated in many places, it has established on the east coast of North America.
In 2003, we found the moth in Hamilton. It was declared eradicated in 2005. We have a surveillance network monitoring for this moth near our borders.
Global distribution of spongy moth
Why this is a problem for New Zealand
The caterpillars have a broad host range. We know the caterpillar feeds on many tree species that are common in our towns and cities, such as oak, fruiting trees, and birch.
In large numbers, the caterpillars are a public nuisance. They leave large amounts of droppings and have tiny stinging hairs that cause an itchy or painful rash.
We don't know what impact this caterpillar could have on New Zealand forests. Some native trees belong to the same groups as trees that are affected overseas. Some forms of spongy moth even have a taste for pine trees.
How it could get here
In some types of spongy moth, the female moths can fly between 1km and 10km. They lay their eggs on all kinds of surfaces, like tree trunks, rocks, buildings, fences, vehicles, shipping containers, and ships.
Vehicles and ships are the most likely ways for the egg masses to arrive in New Zealand. MPI has strict measures in place to limit the chances of spongy moths making it through the border.
When is it a problem?
Spongy moth lays its eggs during the Northern Hemisphere's summer. Our challenge is identifying which ships and cargo might have been nearby when female moths were laying eggs.
Where you might find it
You may find egg masses on items that have been recently imported, like vehicles. If it were present in New Zealand, you may find the caterpillars in spring on the new growth of deciduous trees (trees that lose their leaves in autumn).
How to identify the spongy moth
The egg masses
The egg masses are covered with fine hairs that are light brown or tan. They are oval and can range in size, up to 4cm by 2cm.
The caterpillars are hairy and their colour varies. There are many species of hairy caterpillars in New Zealand. The key difference is the coloured dots along its back. The spongy moth has pairs of blue dots on the front third of its body and pairs of red dots on the back two-thirds.
The moths only live for a week. They vary in colour from a mottled white to a mottled brown. They're not as easy to identify as the caterpillar or the egg masses.
If you think you've found this pest
We don't have any species that lay hairy egg masses in New Zealand. If you see any:
- photograph them
- note the location
- call 0800 80 99 66
If you've found a hairy caterpillar with red and blue spots:
- photograph it
- capture it (if you can but watch out for the stinging hairs)
- call 0800 80 99 66
- This information is a summary of spongy moth's global distribution and potential impacts on New Zealand.
- Spongy moth was formerly known as gypsy moth. Its name was changed in 2022.