There is no real need to mix any soap in the water you spray to knock the Aphids off any plant, just that sharp stream of water is all that is needed, and that will not harm the Lady Beetle larva. Since an Insecticidal Soap spray will also kill those LB larva it is not something you would want use.
If no LB larva were present you could mix 1 teaspoon of a good soap, not a detergent, in 1 quart of water, about a 1 percent solution.

It sounds like the lady beetles already have your back. Just let them work.

Your strong sprays of water will dislodge some LB larvae, make no mistake. But the population will soon recover. Their eggs are a bit more difficult to knock off, so you'll have a fresh batch of hungry soldiers to help out.

The adult beetles will fly away temporarily, but will return to the banquet, too. On a plant like your clematis, sometimes Mother Nature needs some help from YOU in order to return things to a healthy balance.

The black sooty mold will wear away, but only once the aphid population has really been diminished. Be sure to do a good housekeeping job when you cut your clematis back in the fall. If you don't cut your plant back, then you should spray it with horticultural oil over the winter in order to help get rid of aphid eggs.

In the early spring, when new growth emerges, use horticultural oil again. Neem applications, also, can assist greatly in controlling early aphid populations with little affect on the beneficials. Much less so than insecticidal soap, I think.

But your challenge will be to prevent a population from taking over in the first place. Then you won't have the problems you're experiencing now.

I have been hesitant to spray them with the hose b/c I didn't want to knock off the lady bug larvae, since they are doing such good work. However, I do think they need some help, since it's a pretty massive infestation. I have never had this problem with this plant before, or anywhere to this degree. I think the unprecedented amount of rain that we have had this spring is the culprit. I usually have some aphids on certain viburnums in my yard, but I have learned when to watch for them, and a spray with the hose, and a package or two of live ladybugs takes care of them.

Anyway, I was under the impression that a little plain soap (I never said insecticidal soap) in some water would not harm the ladybug larvae. Is this not the case? When I asked about this at one of the local garden centers they said it would be ok. Now I'm a bit confused. I definitely don't want to hurt my little red and black friends!

Insecticidal soaps, whether home-made or commercial, are intended to kill soft-bodied insects on contact. If your intent is to get rid of aphids with 'a little plain soap', you'll need to make it strong enough to do the job. Such a concoction will also harm the LB larvae that it might come into contact with.

Again, as with plain water, the LB population will recover.

I always recommend the commercial insecticidal soaps because there are actual directions to follow. There's little chance of making a solution that is too weak or too strong, or one that is loaded with additives that might cause problems for the plants.

If this were my plant and my home, I'd be all over it with strong sprays of water, on a regular basis. You've got a badly infested ornamental vine and black sooty mold all over the place. That would not be OK with me.

Ok, thanks. Now I know that the person at the garden center did not know the facts. (big surprise.) What you said makes sense about the soap, that's why I was skeptical and wanted to ask here. Normally I do use a commercial insecticidal soap now and then if I need to, but in this case, I will have to get going with just the hose. The aphids and the sooty mold are not ok with me, but I thought I would give the ladybugs a chance to see if they could take care of it. They just aren't working fast enough.

Thanks again.

Using a spray bottle will allow you to avoid the LB larvae. Literally scores of threads on this site on how to make your own soap.

Dan

The pressure of the water stream of a hand held sprayer is adequate to knock Aphids off plants and not high enough to cause plant damage which the garden hose can if not used with great care.