MACADAMIA DISEASE: Evidence of how phytophthora can impact a macadamia plantation - the tree at right has succumbed.
MACADAMIA DISEASE: Evidence of how phytophthora can impact a macadamia plantation - the tree at right has succumbed.

Fight against disease

THE largest number of macadamia growers in many years attended a Mac Group two weeks ago at Wollongbar DPI to learn more about the disease phytophthora.

"We had about 60 people which may partly have had to do with the weather, as it was too wet to get out in the orchard," Australian Macadamia Society CEO Jolyon Burnett said.

"I think it also had to do with the important topic of phytophthora."

Mr Burnett said many farmers were starting to notice the effects of the disease on their macadamia trees and wanted to learn ways in how to get rid of it.

"We were lucky to have one of Australia's experts on the topic give the talk," Mr Burnett said.

Dr. Femi Akinsanmi, senior research officer with the University of Queensland is a macadamia disease expert and said the phytophthora species are unique and different to fungi in that they are water-borne and spread.

Phytophthora survive and infect plant tissue such as roots and the lower stem under wet and waterlogged soil conditions, reducing production by as much as 50%.

"Phytophthora is endemic in Northern Rivers soils and the macadamia trees, being native, have developed a tolerance but if soil health is poor then they are less able to fight the disease," Mr Burnett said.

"Femi went on to talk on soil health saying it was the first thing to address or nothing else will change."

What to look out for

Symptoms of phytophthora:

Leaf yellowing

Small, black, mushroom shaped stromata on large exposed roots and the basal trunk of the affected tree

The wood of the diseased roots and trunk turns brown, shows distinct black lines consisting of pigmented hyphae, and remains firm and hard



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