either mildew or nettle pollen.

When you asked this before you said it was a nettle-like plant and were advised that a photo would help. That's still true - its rather too early in the year for actual nettles to be flowering. If its an actual nettle you need to dig it out. If it isn't we need to see a picture.

Also, actual nettles don't produce showy flowers--just little green fuzzy things.

sorry steragram but the nettles in my garden are flowering now perhaps they are in a more sheltered spot but definitely in flower. and stinging Ouch!