Beat the heat
A LITTLE STEAM HEAT
Climatologists are suggesting tropical weather activities over South Australia this summer are likely to result in periods of increased humidity (and possibly tropical rainfall).
While most garden plants thrive when conditions are humid, high humidity can also lead to a significant increase in the number of leafdamaging fungal diseases.
SA gardens are usually relatively free from rust diseases, thanks largely to our relatively dry summer climate. However, this season keep a close watch on the leaves of roses, geraniums, snapdragons and a range of soft-leaved evergreen shrubs.
Rusts are spread very rapidly by numerous brown, yellow or orange powder-like pustules that suddenly appear on the underside of plant leaves. Seriously affected leaves quickly wilt and die.
Rusts are effectively controlled by spraying the foliage thoroughly with Mancozeb, Triforine or Zaleton (ornamentals only).
However, you may care to try a relatively new organic fungicide containing potassium bicarbonate. This is now available commercially and sold as eco-Rose or ecoFungicide.
This is another damaging leaf fungus that thrives when conditions are humid, mild to warm (not hot) and dry.
Powdery mildew can affect a very wide range of vegetables and ornamentals.
Look for grey powder-like material on both sides of plant leaves. Powdery mildew can be controlled before it is well established by spraying plants with milk (one part milk, 10 parts water).
Also recommended are eco-fungicide and wettable sulphur.
Gardeners growing grapevines will need to keep a watch out for downy mildew when conditions are humid and remain wet for up to 24 hours.
Those with stone fruits may need to protect their crops at harvest from the brown rot fungus.