Spongy moth

Spongy moth not known to occur in Australia and must be reported to DPIRD if found or suspected to be present in WA. 

Early detection is critical to protect WA’s native plants, forestry industry, and fruit and nut producers. 

What is spongy moth? 

Spongy moth (Lymantria dispar) is a destructive and costly pest insect. Its larval stage is a severe defoliator of a wide range of broad-leaved trees and shrubs. 

Young caterpillars feed in groups and large infestations can defoliate entire plantations. Shipping containers are considered a major contributor to the worldwide spread of the pest. 

This pest is not present in Western Australia, so its early detection will improve chances of eradication and containment, helping protect WA’s native plants, forests, fruit and nut producers, as well as building and furniture industries.

What plants are affected? 

Spongy moth affects more than 1,000 plant species including eucalypts, pine trees, fruit, and nut trees. 

What damage can this pest cause? 

Spongy moth caterpillars can defoliate trees in farms, fruit and nut orchards, bushland, plantations, and sometimes whole forests, causing billions of dollars of damage.  

In high numbers, larvae can strip all leaves from a tree.  

Severe defoliation can reduce tree growth and predispose trees to attack from other insects and diseases. 

Spongy moths hold great potential for damage to commercial radiata pine plantations, which would have a severe economic impact on building and furniture industries in Western Australia. 

Legal duty to report 

Spongy moth is not known to occur in WA. Lymantria dispar Linnaeus, 1758 is a declared pest under section 12 of the Biosecurity and Agriculture Management Act 2007.

This means that any person who finds or suspects the presence of spongy moth must report it to the department.

How does spongy moth survive and spread? 

Spread over long distances occurs through human activity such as the movement of infested plant parts, wood, nursery stock, machinery, and equipment, as well as on cargo and in shipping containers. 

• Spongy moths \overwinter as eggs. Although it only takes about one month for larvae to develop inside of the eggs, they usually do not hatch for 8 or 9 months over winter. 

• Masses of eggs are located closer to the ground or within crevices which protect them from cold temperatures. Eggs can resist temperatures up to −20°C without freezing. 

• Mature larvae pupate within a silk nest on a trunk, rock or in leaf litter until complete development within three weeks to emerge as moths. 

• Spongy moth larvae can feed on many hosts, making it a very adaptable invasive species. Feeding patterns depend on larval stages (instars): 

1. Eggs usually hatch in spring, coinciding with the budding of most hardwood trees. 
2. Feeding activity in the first three instars only occurs during daylight hours, but from the fourth instar onwards feeding occurs at night. 
3. Young larvae travel from the bark of the tree to feed on the new foliage by cutting small holes in the surface of leaves. Food intake increases as the larvae grow and feed on the edge of the leaves. 

• Young larval stages can travel up to 200m by spinning silk from their head and travelling on wind currents. They can travel several kilometres and reach new hosts when departing from an elevated position.