Thank you for reaching out to ask2.extension.

I think you may have more going on than the yellow bumps.

Do they move if you touch them?  I think you may have aphids.  I’m also looking at the white  and black things on the stems and the other leaves.

I don’t know much about silk weed.  If you can cut off the affected stems and totally get rid of them, I would.

I would treat the entire plant with insecticidal soap or Neem, coating both sides of the leaves and the stems.  Please follow instructions on the label.

When you cut back for fall, dispose of all of the plants debris.  Keep an eye out next spring for signs of insects.

I hope this helps you!