DISEASE
 
   NAME
     Verticillium Wilt
     Verticillium dahliae

Description
This is a soil based fungus that attacks the root hairs and travels throughout the plants vascular system.

Symptoms
With annuals or perennials such as dahlias lower leaves wilt, turn brown and die and the stems appear normal until the base splits open and turns blackish. This may extend throughout, killing the plant. With larger trees the fungus causes the leaves at the end of the branches wilt and die off.

Verticillium albo-atrum is a soil born fungus that normally infects the roots acting on the water conducting cells by restricting flow causing the plant to wilt. On trees the leaves suddenly wilt and die. This may happen on individual branches on one side of the tree. Other symptoms are leaves form smaller than usual turning yellow and the plant may not shoot the following season. Trees may die over a short or long period of time depending on the severity or number of infections it has incurred and Acer saccharinum and Catalpa species are most susceptible. 

Source and Dispersal
It is found in the soil and dispersed by movement of soil i.e. in containers or on machinery. The fungus may survive in the soil for many years.

Favoured Conditions
Moist poorly drained soils are prone to fungus and during the cooler humid months the fungus is most active.	

Affected Plants
There is a wide range of hosts including tomatoes, potatoes, chrysanthemums and other perennials. It also found in shrubs and trees.
Acer, Achillea, Koelreuteria , Paeonia  and Syringa species are infected by Verticillium albo-atrum causing wilting. Erythrina x sykesii may also become infected.

Berberis species are infected with Verticillium albo-atrum causing the leaves to turn brown, shrivel then die.

Paeonia species are infected by (Verticillium albo-atrum) and the symptoms include the stem becoming covered in grey mould and the leaves wilt during the flowering season resulting from xylem tubes being blocked with fungi. Control methods include removing and destroying disease plants and apply soil pasteurisation using steam.

Non-chemical Control
Cultivate soil to improve drainage and aeration. Cut down and destroy any infected plant material and when taking cuttings from a susceptible plants quarantine them, to ensure they are not infected. Infected soil may be allowed to lay fallow for 2 to 3 years and when replanting used resistant plant varieties.

Chemical Control
For quick control of a cultivated area the soil will require treatment with a fungicide. Consultation with your local Department of Agriculture is advised.
Note
Always read the label for registration details and direction of use prior to application of any chemicals.