What is this white powder that's appearing on the new growth of my eucalyptus tree?

Hi Michelle,

From your description, it sounds like the new foliage is covered in powdery mildew. This disease can distort new limbs or stunt the growth of the tree. The leaves will ultimately fall off. Usually if a eucalypt is planted in full sun, it tends not to suffer with powdery mildew. If it is only a young tree, and you can reach the top leaves, you could remove those infected leaves. To keep the tree healthy and to help it to recover applying a root booster such as Uplift Organic Plant Starter & Root Booster would be of great benefit.