Plants can be affected by many types of diseases, which are caused by a fungus, bacteria or virus, and may affect part of the plant (such as its leaves, flowers, fruit or roots) or can be more widespread. Some diseases can even kill a plant.
Diseases may be spread by moisture, wind or by pest insects feeding on plants. Some arise from infected seeds or cutting material. Diseases are often specific to a plant or a group of plants.
Diseases are generally more likely to have an adverse effect a plant if it is under stress or not growing in its ideal environment. Some diseases are kept in check by regularly removing the diseased part (sterilise secateurs afterwards to avoid spreading disease) and cleaning up around the plant.
A healthy garden can also help prevent disease infestation. If your plants are strong and healthy, they may be able to handle and reduce the stress of pests and diseases. Applying Seasol regularly every two weeks during the year can help them to cope with environmental stress. Keeping plants fed with fertilisers such as PowerFeed All Purpose including Natives, better watering and appropriate light exposure can also help build tougher plants.
In the vegetable garden, practice crop rotation to help plants avoid some common diseases. Where a plant is affected repeatedly by disease, the safest option may be to remove it and replant with a different plant.
Safe chemical options to control plant diseases include horticultural oil sprays such as EarthCare White Oil insect spray or EarthCare Enviro Pest Oil insect spray and chemicals including copper, lime and sulphur such as Sharp Shooter Lime Sulphur. There are also chemical products such as fungicides formulated for specific diseases. Always take care and follow the directions on the label for application rates and frequencies. Remember not to spray when beneficial insects and bees are around.
Below are some plant diseases that may be found in commonly grown plants and crops.