Q.The leaves on my dappled Willow bush are turning brown and crumbling from the tips on.
The rest of the bush looks healthy it looks like the tips of the leaves are drying out. Is it bugs..I don’t see any insects.
It could be a number of things...disease, pests, watering issues, nutrient needs.
Check soil; is it dry or is there excess water?
If you have mulch at the base, pull it back so that it does not touch the trunk of the shrub.
Inspect the bark and leaves for signs of bugs eating it. If there is a sticky substance; this is Honeydew and the residue from pests.
Review the care in the article below.
https://www.gardeningknowhow.com/ornamental/trees/willow/dappled-japanese-willow.htm