I have two lilac bushes. This year one had six clumps of blossoms, the other had none. Now, two weeks later, after the purple flowers have dried up and are gone, I have a whole bunch of small white clumps at the ends of the branches. What is this? I do not recall seeing this before.
It looks like you may have some growth from a root stock.
Lilacs sold today are often on grafted stock.
You should prune away any growth at the base of the plant to prevent root stock take over.