Fuyu Persimmon dropping fruit - causes?

This may be a bit early for a question like this, but JIC...
My wife & I live on the border of Zones 6 and 7 and have a small Fuyu Persimmon tree. We planted the sapling about 11-12 years ago.
In the past 9 years the tree has put forth a number of blossoms that have grown into small fruits. However, long before the fruit ripens, most of it drops from the tree. In six of those years all of the fruit dropped; in the other three years, most of it dropped. What is most discouraging is that the year where we had the most fruit remain on the tree was 1997, where it produced a couple dozen ripe persimmons. Since then we've only had one year with fruit reaching full ripeness, and even then only about half a dozen persimmons made it.
What are some of the things that can causes fruit for this type of persimmon to drop?
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Consider thinning the fruit heavily when they are no larger than a quarter. Assume one persimmon needs fifty leaves to mature. Fertilize, prune and mulch. I am surprised Fuyu fruits that far north. I thought it was Zone 8 and higher.
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Most likely causes of excessive fruit drop are over fertilizing, lack of pollination and not enough sunlight. Other causes can include manganese deficiency, poor choice of rootstock and exposure to winds. Best practices to assure fruit retention include careful, split applications of fertilizer only if tree is not growing vigorously, sensible pruning to allow adequate sunlight penetration, and hand pollination and thinning of flowers. elizabeth, Baton Rouge, LA http://community.webshots.com/user/elott63

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