Looks like sun-scalding to me, but odds of it just happening at the tips is pretty low. I would guess mites, as there are many different types with totally different symptoms.

Regardless, I'd snap off the tops, a bit farther then the nasty stuff is taking place. I'd bag and trash the tops, as you'd not want to keep whatever that is ANYWHERE near your garden. Your plants will spring back quick enough, no worries about that. You just don't want that to spread.

Another issue, probably totally separate from the wilt of the tips... Looks like that plant is virused. The crinkled twist of the leaves, along with the lighter veins, would have me pulling and disposing the plant to avoid bugs from biting it and spreading the virus to the neighboring plants. I've been a stickler with virus signs in my garden, yanking left and right to make sure the rest don't get infected.

Check out VirusBrochure2015.pdf for more info.

Good luck!

Thank you.

I am very sad to hear it might be virus... This is the Emory Paul I was so excited about. The terminal flower bud is still growing, so I do not want to discard it just yet... I will take a few more pictures today and post them later.

Oh, I'm sorry. I noticed suspect leaves on other earlier EP images, but didn't want to discourage you. For many general growers that only have a few dahlia plants, virus doesn't adversely effect them. As long as they don't share with serious growers, there's not really any harm done keeping the virused plants.

Sadly, there is a lot of bad stock of that variety out there. Show growers are always on the look-out for clean stock of this one, as the shock value of the enormous blooms is worth the hunt.

I have to admit to sometimes allowing new varieties to bloom, even while seeing clear virus sign. That way, I have a better idea on if I want to bother growing it again. The trick is yanking it up, blooms and all, and not conveniently 'forgetting' that it's virused. Digging and storing suspected stock is extra bad, as we run the risk of infecting other stock with the tools.

Here the picture of the bud -

More pictures -

Any comparable, reliable large sized cultivars that you would recommend? I have grown Kelvin floodlight in the past and it was huge.

Also always a winner is Nick's Sr., which I believe is a seedling off of Bodacious. It blooms very late, but sometimes takes over a week for each bloom to unfurl all the petals. The stalk is massive, and colors vibrant flame.

Wow! Those are all wonderful - thanks!