Pandanus trees and the threat of dieback

Pandanus, or screw pine, is one of the iconic tree species of the New South Wales north coast. It grows on exposed coastal headlands and along beaches north of Port Macquarie, and has thick 'prop roots' to anchor itself in the loose sand. A prop root is a root on the stem of a plant, usually close to the ground, which helps to keep the plant upright and secure it to the ground.

Pandanus trees can grow up to 6m high. They have long, thin, light green leaves, which grow in spirals on the plant's stems. As the plant grows, the leaves drop off, leaving 'scars' on the stems. Pandanus fruits look a bit like a woody pineapple. They hang from the branches, and can stay on the tree for more than 12 months.

It is hard to imagine the north coast of New South Wales without pandanus trees, but recently these well known trees have been dying as the result of an insect infestation.

What is pandanus dieback?

Pandanus dieback is caused by an infestation of the flatid, or planthopper (Jamella australiae). A female planthopper lays eggs on the backs of the pandanus tree's leaves. When the eggs hatch, the planthoppers build up within the tightly packed leaf sheaths, where they feed on the tree's sap.

The insects produce a sticky substance called honeydew, which encourages mould growth. This makes leaves drop and kills the tree's growing points, eventually causing the death of the entire tree.

The planthopper is native to North Queensland, where it is controlled by natural predators that are not found in New South Wales.

Where is pandanus dieback happening?