Fruit thinning

I have a friend that has several apple trees in their yard.  They love the
trees except
don't want the fruit.   They get several folks over to pick most of it.  But
my question
is, what can you spray on a tree to thin out the fruit?
-- 

OhioBeeFarmer
Getting kids involved in Beekeeping
http://www.homestead.com/BeeKeepers/BeesRUs.html
http://www.homestead.com/BeeKeepers/Opening.html