On the scent of eucalypt leaves and psyllids

Posted on June 8, 2011

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Why do some species of psyllid, tiny insects similar to cicadas, go crazy for the taste of one eucalypt leaf over another?

Is it the taste, smell or concentration of leaf nitrogen that is the main attraction?

Does how the nutritional quality of eucalypt leaves respond to changes in soil nutrient and water availability affect psyllid survival and growth?

These are questions that Dr Martin Steinbauer has been asking in an attempt to understand more about the relationship between psyllids and eucalypts.

The answers will help entomologists and foresters find ways to protect trees from defoliation and plant diseases, and not before time.

According to Dr Steinbauer, an Australian Research Council Future Fellow working in the University’s Department of Zoology, in 2000 the replacement cost of eucalypts succumbing to dieback – caused by complex interactions involving soil and climatic factors, psyllids and other defoliating insects was – estimated at $20 billion.

 Seeking sustainable solutions

‘Australia has at least 364 different species of native psyllid with more discovered each year. Of these, 90 per cent feed on eucalypts and the remainder live on acacias. In the main, Australia’s native psyllids are not pests at all: they are sources of sugar and protein for wildlife, particularly birds and ants,’ he said.

But there are about 20 species that are considered forestry pests because their feeding reduces the photosynthetic capacity of leaves and eventually cause trees to prematurely drop damaged leaves.

‘My research will contribute to the wider search for more cost-effective and environmentally sustainable solutions to manage psyllids on eucalypts.

‘Through this research we will explain how climate change affects the suitability of eucalypts for psyllids.’