As the weather starts to warm, garden pests and diseases begin their rampage. There used to be a tendency to rush out and buy chemicals at the first sign of disease, but with so many organic methods available there are environmentally friendly solutions.

Many fungal diseases are most prevalent in warm humid conditions. They not only affect the aesthetic quality of plants, but also their health and vigour. Once a fungal disease becomes established it can be difficult to eradicate. Prevention in an organic way is much better than having to deal with an established problem.

Black Spot
Black Spot is a fungal disease that commonly attacks roses, reducing the vigour of plants and may eventually produce dieback in susceptible varieties. It first appears as a small black spot on the leaves. Affected leaves turn yellow and generally fall early.

Powdery Mildew
Powdery Mildew is another fungal disease that affects leaves, stems, buds and fruit, covering them with a dusty white fungal growth that looks a bit, like talcum powder. The first sign is often faint white patches on the leaves. Young affected leaves may also become distorted.

Recipe for preventing Black Spot and Powdery Mildew: The basic ingredient is Casuarina needles from any species. These are easy to obtain as they grow widely throughout Australia. 10 grams of needles are added to 2 litres of water and brought to the boil and simmered for 20 mins. When this tea has cooled a further 8 litres of water can be added and stirred for about 10 mins. Make the mixture up to 10 litres, which is enough to cover 100 square metres. It is important to get good coverage on both the top and underneath of the leaves and onto the soil around and under plants, to help clean up any fungal disease and spores that that may be hiding in the soil and plants. Spraying timetable: Spray at 10 – 14 day intervals starting early in the season, just as the temperature is starting to rise. Continue applying the spray until the risk is over.

Leaf Curl
Leaf Curl commonly affects peaches and nectarines, but can also be seen on apricots and almonds. It is a fungus that causes the leaves to twist and distort. Leaves are generally thicker than usual and they develop a pink or purplish colouring. Unfortunately by the time the leaves show signs of damage in spring and early summer it is too late to spray.

Recipe for Bordeaux spray: This is a spray that is based on copper sulphate and lime. You can buy commercial preparations or you can mix your own because it is very simple. Add 10 to 15 litres of water to 1 cup of copper sulphate and 1 dessertspoon of lime, and stir well. The mixture actually prevents fungus from entering the plant, so again good coverage is necessary. If you get the timing right you should only need to do it twice. Try spraying in mid winter and then again at pink bud stage, which is a critical time.

Stinging Nettle Tonic: This plant is high in nitrogen so it promotes good leafy growth. Roughly chop up 1.5 kgs of stinging nettle and then add 4.5 litres of water. In a week or so this mixture will have started to ferment. The liquid can then be used diluted or undiluted as a foliar spray.

The healthier a plant is the less susceptible it is to disease, which means choosing the right plants for the right position, and feeding not only the plants but also the soil with organic fertilisers or aged manures and compost.