Why won't my Washington dwarf navel tree produce any fruit?

[am.smiley]

I have a dwarf navel orange tree in my yard, the previous owners planted it so I am not sure how old it is, but I moved here 3yrs ago so it's at least that old. Each year it produces lots of flowers and tiny little buds, but they all eventually fall of. Should this tree be producing fruit by now? Is there anything I can do to encourage fruit production? I fertilized it this year with ground spikes for citrus trees, and it has plenty of sun and water. The flowers are very fragrant. Anytime I check it, I see at least 2-3 bees on the flowers, so I don't know what the problem could be. I have read that "shaking" the tree can help with pollination, should I try this? Any advice would be appreciated, thank you.

[The Helpful Gardener]

Premature flower or fruit drop is usually about abrupt changes in one or more of three things: temperature, humidity, or photoperiod (light). Most of us can't keep the constant conditions these trees love, hence no orange groves in St. Louis...

The more you can do to keep these three things constant, the better of you'll be...

HG