Plants are watered every three or four days, usually our rainfall has been regular in Port Macquarie though recently humid after exceptional levels of rain....could this be a form of mildew? Plants have grown considerably through the year they have been planted and are close to and overhanging the ground.
Without seeing the plants it is a little difficult to know whether it is a pest or disease that is attacking your plants. I am assuming you are growing Acacia Limelight, a small growing weeping native shrub. It could be a scale that infests the twigs and branches. This can easily be controlled by spraying PestOil which causes suffocation and rapid death. It could also be mealybug which looks like a white sticky mass. This pest can also be treated with PestOil. Spray on a regular basis to stop this pest from attacking the whole plant. Powdery Mildew is a disease which seems to thrive in warm humid weather. This disease produces produces a white coating on the surface of the leaves. Yates Rose Shield will control this disease as this product contains a systemic fungicide. Perhaps with this information you may be able to determine whether the problem is pest or disease related. All of the products mentioned are available through garden outlets.
Answered: 3 Jan, 2019