Looks like WhiteFly, they lay eggs in a circle & have all this whispy white
stuff.
A soap or oil spray would do. I was told that the eggs hatch every three
days so you need to
spray often until they are gone. They love Hibiscus & large leafed plants.
I think I used Neem oil.
Good luck
Cheers Wendy
"Paul O." wrote in message
...
Can any one tell what this is on a leaf of one of my plants? Thank you.

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Paul O.