Unknown disease on a peony – how to save it?

Good afternoon! I'd like to tell you about a peony disease.
I have 6 peony bushes at my dacha – 3 pink, 2 white and one burgundy.

In 2019, I transplanted four old peonies to a new location. Their blooms were fading, so I decided to rejuvenate the peonies. I did this in the spring, as my flowers were still blooming profusely at the end of summer, and it seemed a shame to destroy them. I planted all my peonies in the spring, and they developed normally. Of course, you shouldn't expect abundant blooms this year; some even recommend pinching off the buds to allow the bush to root properly and develop new buds.

All the bushes had old roots. After laboriously cutting through these thick trunks, I selected young tubers with buds and planted them in a new spot. They look fine now, with rich green leaves, unblemished and smooth, and few buds yet, but next year they will grow thicker and bloom fully.

I have two other peonies growing in a different place, the bushes are still quite young.

In the spring, as always, I trimmed the low, dry stems and raked the humus away from the bushes, and they sprouted pink shoots. One successfully opened its leaves, but the other pink peony failed to open and had pale yellow stems with stuck-together leaves, twisted in some way, and the stems themselves were crooked and twisted.

At first, I thought the bush lacked nitrogen and watered it with a urea solution. But even after the fertilizer, the leaves wouldn't open, and although the yellowing had disappeared, they were still curled and sticky, and I even thought there were small aphids inside.

We have a small plum tree growing near the peony, and the leaves on the young stems were curled up, too, and there were aphids inside. And, as always, ants had invaded the peonies. I treated the peony and all the nearby plants with aphid repellents. But the bush still showed no sign of unfurling its leaves.

The stems grew, the buds enlarged, but the bush looked strange compared to all the other peonies. The bush had many stems and leaves like these.

I realized the peony was sick. I searched the internet and couldn't find anything similar. Most of the articles were similar in content, describing viral and bacterial diseases—various spotting, rust, and root rot. My peony had no spots or rot; it simply had crooked shoots and curled leaves.

Even the care and treatment recommendations in the articles were the same. They said the peony lacked phosphorus and potassium, and when these elements were lacking, the leaves curled. First, I fed the bush with phosphorus-potassium fertilizer, then sprinkled ash under the bush. A few branches opened their leaves, but most remained as before.

Then I started treating the bush for fungal diseases. I poured a solution of Fundazol (I don't remember the name of this product) under the bush and threw away the packet. But there was no change.

Then, I doused the bush with a solution of Fitosporin directly from a watering can and thoroughly watered the soil beneath the peony. The leaves opened, but they were all somehow misshapen, curved, with a wavy pink border along the edges, and red spots. This is what the bush looked like at the end of May.

These are the leaves it has.

There is a white peony growing nearby, everything is fine with it, and the other four bushes are also healthy.

Could it be a viral disease or could the bush be attacked by nematodes?

In case of viral diseases, it is recommended to dig up and destroy the bush, since viral diseases are not curable and can spread to other flowers.

Diseases are spread by ants, rose chafers, and other insects. We have a lot of ants on our property, and we're constantly battling them. They love peony buds—they contain sweet, aromatic nectar, rich in carbohydrates, and they enjoy it.

The bronze beetle is a large, beautiful, pearly-green beetle. It attacks buds that are opening and blooming, gnawing them out from the inside. We have one here too, and we have to remove it from our flowers.

The bush's tubers can be attacked by nematodes—tiny, light-colored worms that live in the soil and cause significant damage to the flowers. Peonies grow poorly, fail to bloom, the stems wilt, and the bush dies. The presence of nematodes can be identified by the bumps on the roots; to detect this, you need to dig up the peony. But nematodes are unlikely—my bush is growing normally, only its stems and leaves are altered.

I've decided not to destroy my sick peony for now. I'll try to cure it.
This photo was taken in 2018, this is how this peony was blooming, but if you look closely, you can see that there are wavy leaves at the bottom, this means that the peony was already infected.

I didn't notice the altered leaves, and of course, after flowering, I cut off the buds and didn't pay much attention to the bush again. In 2019, the bush bloomed just as profusely, and if there had been any oddities, I would have noticed them.

Found a solution

I found a single video on YouTube, on the Garden Guide channel, titled "New Peony Disease," from which I realized my pink peony was infected with an unknown disease:

After reading the comments under the video and advice on what to do if a viral disease occurs, I decided to cut out all the diseased leaves and stems after flowering. I'll spray it all summer with Fundazol, Fitosporin, Trichoderma, and a potassium permanganate solution. In the fall, I'll treat it with Bordeaux mixture. I hope to cure my peony.

It turns out that many gardeners have encountered this problem for a long time, but for some reason, the all-knowing and ubiquitous Internet doesn't have a single article on the topic.