Is there a remedy to stop armillaria luteobubalina root rot diagnosed in gum tree>
03 October 2011, 05:28AM
Unfortunately there is no chemical control measure for armillaria root rot. There is wonderful information available from the Royal Botanic Gardens Sydney. Here is an excerpt: Armillaria luteobubalina is a soilborne fungus that causes root rot and wood decay of a wide variety of plants, including many Australian native and introduced ornamental plants.
The fungus Armillaria luteobubalina is native to Australia and causes losses in natural ecosystems, forest plantations, fruit crops and ornamental or amenity plants. The host range of the fungus is very large and poorly defined with little information on the presence of resistant or tolerant species.
Symptoms of the disease
Early infection is difficult to detect and symptoms may not appear until late in the disease cycle and are generally not definitively diagnostic when presence. Such symptoms may include dieback of the limbs and branches, yellowing of foliage, splits in the trunk of the infected tree, poor vigour, exudates from the trunk (kino production), scars may form on the trunk and darkening of the larger roots.
Removal of the bark may reveal the presence of mycelial fans, which are large sheets of fungal growth, usually white in colour. The surface of the affected timber is often pitted in appearance.
The fungus produces mushrooms in May-Jun. These are olive brown to yellow in colour, can be up to 12 cm in diameter with a stipe (stalk) of up to 15 cm high, although usually less. The stipe has an annulus (the ring of tissue around the stipe) that should be quite obvious.
Infection occurs primarily across root contacts from the infected roots coming into contact with uninfected roots and the fungus growing across. The fungus does not appear to readily produce rhizomorphs (specialised fungal threads that can grow through the soil) and it is less likely that the fungus can spread through the soil by its own devices.
The fungus is able to infect new areas by several means. Very rarely the spores of the fungus are dispersed through the air and land on dead wood surfaces and initiate infection. More commonly the fungus will be introduced into an area by the transportation of infected material such as the transplantation of infected plants, contaminated roots, or contaminated mulches. Hygiene is obviously important in minimising the spread of this fungus as the fungus survives in infected plant debris.
Drought is often associated with severe symptoms. It appears that the stress involved predisposes the tree to infection and also allows the fungus to more rapidly colonise the root system of the plant. Similarly stresses resulting from flooding can also predispose trees to severe infection. It is fair to say that any factor that stresses trees is likely to result in a weakened defence system and an increased likelihood of the disease developing.
The fungus can survive in soil for extremely long periods of time and there are estimates of survival for up to 50 years.
At present there is no one simple method for controlling Armillaria luteobubalina. A combination of sanitation measures, good horticultural management and the addition of organic matter to soils can be expected to retard the activity of Armillaria.