I agree with Njoynit and Longy about the importance of consistent watering. I also use/put gravels on top of the soil to help keep the soil moisture in limes, lemons, oranges, kumquats, other citruses, loquats and edible figs.
Jim, large amount of fruit drop may occur when the lime
tree is under stress due to overwatering or underwatering, high heat or extreme cold, or rapid changes in air temperature and moisture.. Fruit drop is usually preceded by blossom drop.
Fruit may develop to the size of a pea, and/may also fall off if the
flowers have not been pollinated. Pollinators could be deterred by rain, and cold weather.
Excessive fruit drop may also be caused by improper fertilization. Do the apllication between February and September, 4X during the first two years, 3X thereafter until maturity.