Certified GKH Gardening Expert
Dried fruit on the tree is normally cause by disease, which is introduced by the Dried Fruit Beetle. They crawl up into the fruit and bring disease. They can overwinter in the ground, which is why you have had this problem for many years. Eggs may be laid in the fruits as well as the soil. Larval stages are very active and will try to hide if disturbed. Adults are active during the day and night. Selective pruning (to allow more sunlight) on figs dropped beneath trees or rapid removal of dropped fruit may reduce problems. General or spot application of a labeled residual insecticide may also be used.
This article will help: http://extension.entm.purdue.edu/eseries3/view.php?article=articles/dried_fruit_beetle_and_corn_sap_beetle.txt&id=1§ion=Stored%20Product%20Pests