By Growing Illawarra Natives coordinator Emma Rooksby

The beautiful Sassafras tree (Doryphora sassafras) is a distinctive and very common local rainforest tree of the escarpment.

It is present in many areas along the slopes and benches, but particularly the steep upper slopes. These upper slopes run all the way up to the towering sandstone cliffs at the very top of the escarpment. They are dominated by a relatively small group of trees, particularly the Sassafras and the Coachwood (Ceratopetalum apetalum).

The Sassafras are a beautiful slightly yellowish-green in appearance while the Coachwoods have darker green leaves. 

But something (or many somethings!) is eating the leaves of the Sassafras and many trees are almost leafless as a result.

This phenomenon has been reported locally over the years, including on Mount Keira (autumn 2023), the escarpment in Thirroul (autumn 2024) and this year in Kangaroo Valley. In some cases, such as Mount Keira, the result has been dramatic, with much more light landing on the forest floor and some trees not yet recovered from the feast. 

Curious locals have investigated and found that the severe defoliation of Sassafras trees is the result of feeding by phasmids, also known as stick insects.

In 2023, Elena Martinez of Keiraville spotted Phasmids in the genus Candovia. This year, Ruben Fitzsimons from Kangaroo Valley has identified three separate phasmid species, including the the Margin-winged Stick Insect (Ctenomorpha marginipennis), the Richmond River Stick Insect (Candovia rumosa) and Candovia robinsoni (sorry, no common name for this one!), having a right old feast on his Sassafras trees. The image below shows Richmond River Stick Insects. 

One fun fact about stick insects is that they are a favourite food of the Pacific Baza, a small raptor with a distinctive prominent 'Mr Curly' crest on its head. Pacific Bazas also eat mantids (e.g. praying mantis) and frogs, but stick insects seem to be their favourites, particularly during the breeding season. 

Anyone who's seen a similar phenomenon recently, with trees completely losing their leaves, may have a phasmid feeding frenzy happening. If so, feel free to let me know – and share a few pictures (there are also other insects that can defoliate whole trees). Email me here.