Avocado Tree Leaves Turning Brown and Falling?

I have a 9 year old avocado tree and every year when the tree blooms, all the leaves turn brown and fall off and all the buds dry up, turn brown, and fall off. The branches are always green and as everything browns and falls off there is new growth, leaves and branches and such. Only once did it bear a few avocados. I believe there were 8 of them though only two made it to full maturity.

The raccoons may have gotten the rest. The tree is a dwarf tree that we bought at a nursery and planted in our backyard. We have no idea why this happens and it does not make much sense to us because the tree continues to look healthy and grow. We have tried different fertilizers and nothing seems to help. It's about 12ft tall now.

By Alison H.