When it comes to tree and shrub care there’s two main things that we focus on: fungus and pests. In our area, both are a major issue, but pests seem to be a bigger problem for us. When treating pests, it’s important that you cover the foliage completely. Just treating the surface of the shrubs will leave tons of interior foliage for pests to hide in. Especially the underside of the leaves. Hope this helps!