The best recipe, in my opinion, is to go to the store and buy a bottle of insecticidal soap with an instruction label on it.

There are soaps on the market that can be used for a homemade spray, but as you have seen the info on the web is quite contradictory and in some cases dangerous (to the plants).

Most soaps aren't soaps these days and contain many things that may or may not harm the plant. You won't know until you try or find someone you trust to give you specifics.

For what it's worth, we've been making our own insecticidal soap for years" 1 Tblsp. Ivory soap, shaved in 1 qt. water (if you use treated tap water let it set in an open container for 24 hours to rid it of cholorine)and 1 tsp. vegetable oil (not canola, not olive). I put this in a spray bottle and let the little bugs have it! It works for us, but perhaps until you feel comfortable with using the soap spray, commercial could be better for you.

Dish soap isn't really insecticidal soap (registered trademark required). It is dish soap, of course. Will it kill insects - yeah. I use both but on plants that really have value - I use the commercial product.

The sunflowers usually become a mess with aphids late in the season. I like to have, at least, some that mature a crop of seeds. And, there are usually others that I want for bouquets without the aphid-plagued older plants contaminating them. Sunflowers make wonderful informal bouquets but having them "dancing" with aphids is a bit too informal.

Each year, I spray the sunflower patch with: 3 tablespoons of Palmolive Green dish soap for every 1 gallon of water. (I bet Marlingardener's formula would be good, also.) The Palmolive has worked well for me and over 5 or 6 seasons I haven't seen damage to the plants.

Elsewhere, I have seen damage - - a plum tree that was hit with aphids and then hit with dish soap (probably un-measured). That tree dropped every leaf.

. . . a word to the wise.

Steve

I've been diluting Safers insecticidal soap by half and still seeing damage to the new growth on my CA sages and certain roses, so do be careful in application.

Yes. This recipe of 2 TBS. of Murphy's Oil soap to 32 oz of water was recommended to my by the Cactus and Succulent Society of America to be safe on cactus and succulents to kill spider mites and insects . I use it on all of my plants and have for over 8 years. Petroleum based pesticides will kill succulents and cactus plants, so I know i'm safe with this vegetable based oil. No need to add more ingredients and more oil. It works like an insecticidal soap and much cheaper. Watch out on the Safer products that contain Neem. Neem almost killed my Japanese Maples that I used it on. I think it will also damage magnolias too and a bunch of others. I burnt some of my cactus too. I don't trust neem oil at all.

Neem is a great horticultural oil to use for a wide assortment of plant problems, both insects, mites, and diseases. HOWEVER, it can't be used on everything nor at all times of the year.

It is, after all, an oil. Japanese Maples are well known for being extremely sensitive to oil applications in general, but not to neem oil specifically.

I can think of no plant with a specific neem sensitivity, but plenty that require care when using any kind of horticultural oil.

Neem oils are specifically recommended for the management of scale insects on Magnolias. We just need to be watchful of the timing and of our application rates.

As always, following labels is important, as well doing a little bit of homework to make sure that we understand the ramifications of any application.

Any pure soap is made with an oil source. Coconut oil, olive oil, canola, corn, etc. The original soaps were made from animal fats. Liquid vegetable soaps can be found anywhere that sells true soaps, liquid or bars. I prefer to use a soap without artificial colors and scents, which can cause plant problems all by themselves.