Wednesday, 10 June 2009

The Plant Hospital (Passion for Plants*)


Like us, plants are damaged, debilitated and killed by diseases. Sometimes they shrug off a minor infection, other times they only survive with some kind of surgery or chemical treatment.

With around 42,000 individual plants – excluding grasses in our lawns, but including more than 3,000 mature trees and about 9,000 different species and cultivars – the botanic garden needs a plant hospital. We call it the Plant Disease and Diagnostic Unit.

We now have a new ‘hospital’ building in our Central Depot, in the shadow of the Cahill Expressway. Like all hospitals, we have disease diagnosis and treatment areas, as well as research laboratories.

Most of the diagnoses are for soil-borne pathogens, particularly species that cause Phytophthora root rot. Treatment for Phytophthora cinnamomi, the usual culprit, includes adding more organic matter to the soil (to encourage other micro-organisms to out-compete it), improving drainage and under some conditions using the chemical phosphonate.

Generally you can only slow down its spread. It’s far better to use good garden hygiene to avoid Phytophthora getting into your garden in the first place.

Our research is mostly on fungi, but also includes Phytophthora (which is actually more closely related to the giant brown kelp in the sea than it is to a mushroom).

A lot of effort goes into detecting and documenting leaf diseases in the Proteaceae and Myrtaceae families, including well-known Australian plants such as the banksias and eucalypts.

Within eucalypts at least, there seems to be a close association between many of the fungal and eucalypt species, suggesting probably co-evolution of the host and its pathogen.

But with more eucalypts being planted overseas, new associations are formed between fungus and plant, sometimes with drastic consequences for the plant. Accelerated climate change may have the same result, as pathogen and plant respond differently to changes in temperature and rainfall.

We also have one of the world’s top research groups studying a deadly fungus called Fusarium oxysporum. This is actually a complex of different but related fungi that cause catastrophic crop losses in over 150 plant species, with huge economic consequences. It is also a major cause of palm deaths in Sydney.

The Botanic Gardens research team have discovered strains native to Australia, in soil as well as on local relatives of tomatoes, palms and cotton. This knowledge will help predict future adaptations of the fungus, as well as tracking the evolution of the pathogen to help manage its future spread.

But if you simply want to know what is wrong with you garden plant, and how to cure it, look up ‘Pests & diseases’ under the ‘Plant Info’ tab on the Gardens’ website or ring (02) 9231 8186. Note that this service does incur a charge.
*This posting will also appear on the ABC Sydney website (possibly under 'gardening'), and is the gist of my radio interview with Simon Marnie on Saturday Morning sometime between 9-10 am on 702AM.

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