I have always had a terrible time with aster yellows. (And I LOVE the flower for bouquets). I searched on this forum and see that a row cover is suggested to deflect the leaf hoppers. I do OK with asters if I plant them in large pots in the greenhouse, although most varieties have weak stems when grown this way.

Any suggestions for more disease resistant varieties?

I go to farmers' markets with bedding plants and perennials. Bouquets are an added value product for me - but SO much fun to make and sell.