The coastal Pandanus tree (Pandanus tectorius) is now under threat from the native leaf hopper (Jamella australiae) in South East Queensland. Although the two have co-existed for a long time, the leaf hoppers numbers are normally kept in check by its natural predator a tiny wasp known as Aphanomerus pusillus. The problem is believed to have been caused by trees being shipped south from Northern Queensland with the leaf hopper on board. Unfortunately, the tiny Aphanomerus pusillus wasp missed the trip.
Drastic action is now being undertaken on the Gold Coast with Pandanus trees being heavily pruned back or even cut down in the interests of public safety. In 2015 on Fraser Island thousands of Pandanus trees died due to the diseases spread by the leaf hopper. Just North of Noosa at the Great Sandy National Park around 20 percent of the pandanus trees have died. Another 2500 trees were showing the effects of the infestation. Joel Fostin from the University of the Sunshine Coast has been studying the problem on Frazer Island and is undertaking research on biological controls using the Aphanomerus pusillus wasp.
How to check your Pandanus
Normally even healthy Pandanus trees will have some dead leaf at the base of the leaf head. If you see a large amount of unexpected dead leaf material in the centre of the head, there is a good chance you have the infestation. Look for the black sooty mould caused by the leaf hopper’s secretions on the tree’s trunk or leaves. Also look for cast insect skin casings or insect egg cases between the leaf sheaths or on the underside of leaves.
Treating the infestation
Contact your local council if you see signs of infestation. Prune the plant back hard and seal the trimmed material in a bag. This material should be mulched or composted. When buying plants use locally grown stock from a reputable plant nursery. Inspect plants carefully for any sign of infestation before buying. Your local plant nursery should have a skilled horticulturist on hand to check the health of your plants.
About the Pandanus tectorius or screw pine.
A small tree which can reach up to 6 metres tall with leaves up to 1 metre long. Prop roots at the base of the tree help to anchor the plant in sandy soil.
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Tweed Shire Council – 02 66 702400.
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