Yesterday morning I found an eggplant bloom on the ground. The stem had a clean cut about an inch below the flower. It was not a bloom "drop" because the cut was very clean, healthy stem and there was a bead of serum oozing out of the plant end of the cut. This flower was about 2 feet above ground and the plant is well developed. There is no other indications of any insect or pest damage on this or other plants in the area. Retrospectively, I think similar damage has occurred before but I did not actually notice this closely. So I am wondering what is doing it and how to prevent it?