Hi Lily,
" And I have some problems with leaf miner and white flies? "
Leaf miners are never a problem for me. They have natural enemies that keep their population in check, and they do only minor cosmetic damage to leaves. (As you have done, if you don't like the looks of a leaf, you can always remove it.)
My only serious white flies problem was when I was trying to raise a full sun plant (tomatoes) in a shaded environment (our front porch.) I did have a major population explosion of white flies on a couple of potted tomato plants on our shaded front porch. I used our canister vacuum cleaner to suck them in. After a few vacuumings, the white flies were pretty much gone. I did do some minor damage to the tomato foliage. But nothing compared to what the white flies were doing, which was killing the plants outright.
Zinnias don't normally have problems with leaf miners or white flies.
ZM
