Without question you have an infestation of the lesser canna leaf roller. This is NOT a virus, it is caused by a small worthless night flying moth that lays its eggs on the leaves and rolls and seals the leaf into the tight whorl. All the kings men could not slow down or prevent infestations in your area.

You may have other issues but because the leaf roller has decimated your cannas to the point that identifying other problems become moot. Everyone in your area and down through the Gulf States deal with this issue (the lesser canna leafroller). There are many beautiful cannas growing in these areas but not without using control measures.

You have four choices:

First: continue to grow as you have and continue to provide a prime breeding area for the leafroller.

Second: Try using band aid GREEN solutions sometimes found at this site and others that reminds me of trying to rid my dog of fleas with a flea comb; with the same results.

Third: Stop growing cannas.

Last: Follow directions and USE a systemic insecticide.

Brutal but direct for a serious problem. Thanks for posting.
Kent

I have the same problem, yes, the leaves are being rolled by caterpillars. Ask yourself honestly, do you like these Cannas enough to inspect them about twice a week all summer to get rid of the caterpillars? If not, I would urge you to get rid of them. They are a nectar source for hummingbirds, so poisoning them to get rid of the caterpillars could also poison the hummingbirds.

If you have the time and inclination, I would get a large tub of water, start cutting off everything not green or rolled, into small enough pieces to fit in the water. Left overnight, anything alive should be drowned, so then pour it out, but put the leaf material in compost or far away in another location, in case there's still live eggs on it. Then inspect growth for new signs of caterpillars and dispose of as you find them. Signs are little black dots (poo,) rolled leaves, they will be sealed with spider-web type stuff. You can slice that open and find the caterpillar inside, or just cut the whole thing off to drown or otherwise dispose of the cat. If you kill them as fast as they show up, you should get a good show from a patch that size, but it's constant work. "Getting rid" of them this year doesn't mean they won't be there next year. The adults fly, so can fly right over and lay new eggs.

Also, when the season ends, they're in the leaf litter, hibernating or pupating, I don't remember. But point is, it's recommended to clear Canna litter to compost or far away across the yard to mulch something else, then mulch the Cannas with tree leaves or other OM if wanted or necessary.

HTH you consider what would work for you.

Thank you very much for your reply. Much appreciated. Given the time I have available to deal with this issue I think I'm going to get rid of them. Normally I shred my plant waste but I'm not sure if it's a good idea to risk further spreading the problem

Yeah, I may get sick of doing this sometime soon also, lot of mosquito bites dealing with these caterpillars. There are plenty of other nectar plants...