Is the problem holes in the leaves, Jo? Or are the flying specks the problem? If the former, have you gone out at night with a flashlight--the flying bugs are probably not the culprit, though they may be doing damage all their own. If the latter, are the specks snow white, or some range of black? Is the plant yellowing, and/or covered with a sticky "varnish"? Ask anyone on this site, they'll tell you what a nosy parker I am! I am just trying to narrow down the possibilities, though.

Well now just had a good close up look at my Rudbeckia & Im near certain it's a slug attack. I did a big slug catching exercise last year & maybe got a bit too cocky this year thinking I'd captured them all! Silvery trails around base of plants & were they are planted is prime slug territory & they must be able to scale up to the top leaves between 1 & 2 feet high. Hope it's them not an invisible caterpillar creature!

Nope, I'd be pointing my finger at the slugs first, too!