Non Toxic Sprays
I have always been interested in using methods to deal with insect pests and diseases that did not involve toxic chemicals. Although, what is meant by that can be debated. After all when making sprays from such things as rhubarb leaves, which are poisonous, am I making a toxic spray or not?
Using pest plants seems to be a good vengeance on them. Also using readily available Australian native species seems to be good sense. Eucalyptus has long been used as a remedy for many ailments of humans. I came across the use of Casuarina (or Allocasuarina) needles to make a fungicide which is good for damping off fungus in seedlings, and black spot and powdery mildew on plants. Use any available species. These trees are often used in windbreak and border plantings.
One recipe is 10 grams Casuarina needles to 2 litres of water, boiled for 20 minutes. Stand to cool. Make this solution up to 10 litres with additional water and stir well. Strain through cheese cloth so that it will not clog the spray nozzle. Spray over and under leaves, and around the soil beneath the plant. This much will spray 100 square metres. See this ABC Gardening Australia Fact Sheet of a few years ago for other details.