In most cases, sooty mould is the secondary infection caused by insects such as aphids, scale, mealybugs, and whiteflies that secrete honeydew. Sooty mould is a fungus that feeds on the honeydew, covering the leaves and stems in a black sticky substance. It does not feed directly on the plant’s foliage; however, it covers the plant’s leaf surface, blocking light and reducing photosynthesis, essential for plant growth.
Sooty mould can easily be rubbed off the plant by wiping the affected foliage with a damp cloth or a soap and water solution to help soften the sooty coating. This is only a temporary fix, the permanent solution is to remove the pest that causes it. Using a horticultural oil such as EarthCare White Oil insect spray or EarthCare Enviro Pest Oil insect spray will help to control the insects that secrete honeydew. As the supply of honeydew gradually runs out, the sooty mould will disappear.
A healthy garden can also help prevent pest and 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.