Answer: Young Eureka lemon trees often set more blossoms than they can possibly develop into fruit. Early fruit drop is common in young trees. Sounds as though you've been pollinating the flowers correctly - the only other thing you need to do is make sure the soil is consistently moist during fruit formation. What you might try doing is physically removing all but one or two flowers on each branch. The tree may be able to grow a few fruit to maturity without giving the signal to abort all. As your tree matures, it will be able to set and hold fruit to maturity. It just needs a little more time.
Best wishes with your tree!
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