I see aphids on the plant. These can transmit viral diseases and they can result in 'broken' flowers and distortion. This is only a suggestion and I have nothing further to add.

@floraluk2 This makes total sense. It's some kind of viral transmission from the Aphid infection.

Assuming I control the Aphids at some point, I guess the virus is here to stay?

I also read that thrips can lead to discoloration. Mine were showing white discoloration and distorted leafs on the tips while indoors over the winter. I would give it a good spray of water and then horticulture soap or neen spray. A Bayer 3 in 1 would also work if you aren't averse to chemicals.

Obviously, the aphids need to go.

@getgoing100_7b_nj I have tried quite a few things for Aphids and the Aphids are winning.

Watering them off is a non-starter. There are far too many places for them to hide.

Insecticidal soap works well, but it would be 30 minutes of work each and every day to get every spot where they are growing. There are thousands of leaves on this vine.

I tried Ladybugs recently and that is a joke. They stand face to face with the Aphids and do nothing. After about four days, they appear to be just gone. This plant could feed 10K Ladybugs for a month. Why would they fly off?

I tried Lacewings, and those eggs never even hatch (a common complaint of buyers online as well).

I would like to try parasitic wasps, but they are too expensive.

Why every day? I would think 2-3 sprays a week apart should do it. What kind of sprayer are you using? One way to do it is to make the plant healthy enough to withstand the attacks. I would give it a low N, high P fertilizer, perhaps sea weed and may be some epsom salt as well. High N atracts aphids. Another way is to give the aphids something else (sacrificial plant) that they would prefer. These are yellow, I have seen these on Calotropis Procera/gigantea, another plant with latex sap. Perhaps a milkweed?

perhaps a systemic is called for, like bonide that has imidacloprid. That way, no spraying and it would work for a while.

I still think hose blasting plus fingers would work, even if you don't get all of them. You need to repeat it, though not every day. The idea is to weaken the insects and break the breeding cycle. Use a strong spray. It's much faster than planting Allysum and awaiting predators. Do that as well but it will take time to establish an environmental balance.

@floraluk2 There are 100+ stems they are hiding on, and much of that is hidden behind dense leaf growth.

Is there a hose attachment that would create a stream better tailored toward taking aphids off of a vine? The normal garden spray is putting out large amounts of water. It sprays against the house, the windows, and everywhere, and makes very little impact on the Aphids.

@getgoing100_7b_nj I used the Bonide potassium insecticidal soap. I do use it every two or three days. It looks like it works and you don't see any more Aphids. Then, three days later, there are tens of thousands of them densely covering the whole plant.

So to really impact this you would have to dig back into the plant and find all of their hiding places. It's a big vine and it's time-consuming.

I hesitate to use a systemic insecticide but may lose that battle. I end up spraying it on my skin, breathing it in, and do I end up getting cancer one year earlier in order to kill some Aphids?

Bonide has a granular systemic that is just added to the soil. So no spraying.

"Is there a hose attachment that would create a stream better tailored toward taking aphids off of a vine?"

Quite possibly but it is not necessary to be constantly buying stuff for every problem. I just stick my finger over the end of the hose to create a narrow spray. I've seen pictures of your plant. It's absolutely doable. You don't have to get every aphid from every twig. Just knock down the numbers and do it again every so often.

Have you grown mandevilla in prior years without an aphid issue?

I generally don't have an aphid issue with my mandevilla, flowers, herbs or vegetables in pots or in the ground. BUT anytime I have planted tomatoes, petunias or calibrachoa, hordes of aphids appear on them. So after a few years I stopped growing them because it was a never ending battle that the aphids usually won.

@getgoing100_7b_nj Can you point to the granular systemic you like on Amazon?

Sure, Bonide Systemic Insect Control, 1 lb. Ready-to-Use Granules for Long Lasting Insect Control in Lawn and Garden https://a.co/d/8dItf9N

Here is what a typical section of the infected Mandevilla looks like. Spraying this with water just doesn't get them all. Potassium salt works well on these long exposed sections, but they hide on stems protected by leaves, and even just finding all these sections would be 30 minutes of work.

Both Bonide and Fertilome make a liquid soil drench systemic that lasts for 30 days.