I am not a fan of 'diy' pesticides - especially ones circulating around the internet right now. I'm all in favor of things being cheaper and I'm definitely in favor of no one ever buying Round Up again, but to replace it with this is not an improvement.
I am an organic gardener and have been from the days it was 'crazy' and 'stupid' to be an organic gardener. Now that it's cool to be an organic gardener, I have moved on to being what we laughingly refer to as "post modern organic." I don't use any chemical pesticides at all. It really doesn't make sense to use any poison on the food you will eat. If it must be doused with poison, it is not worth eating. I am convinced that insects primarily attack weak and under performing plants and in that way are nature's clean-up crew, keeping genetic material of weaker plants out of the reproductive pool.
Part of the reason we need insecticides, though, is because we buy bunches of chemicals to make our plants greener and taller and fatter and more better in all ways. All that extra growth is succulent and green - easy picking for insects. Stop putting on all that fertilizer and you won't have to spray insecticides! How about that - you stop buying both products - think of the money you save. Meanwhile you'll have uglier looking fruit that is better for you and the environment - plus, if you like killing things, you can now afford a couple of tickets to see the latest nonsense the movie industry has dreamed up in which people die left and right. I'll pass on that too.
But to this chemical concoction directly - did you even look at the ingredient list? Holy cow! There is NO WATER to dilute the mixture. It is ONE GALLON of vinegar. Do you know what the pH of vinegar is? 2.2 - remember, your soil and plants perform at optimum somewhere much closer to 4.5 or 5. THIS STUFF WILL KILL YOUR SOIL'S EARTHWORMS, BACTERIA AND FUNGI! You'll be creating dead soil. I know, because you won't spray it over your entire garden, the dead zone will be relatively small and can be repopulated from adjacent areas, but do you really want to do this? Why kill the things you are trying to attract to your garden, like soil bacteria, fungi and the millions of other little creatures in the soil that make your garden truly fertile?
Besides which, this concoction will not really kill several of my perennial weeds, although it could give them a good knock. False garlic, Bermuda grass, morning glories and nut grass. All of these have defense mechanisms that would prevent this weedkiller from working. I used straight vinegar for a time, but then, one day pouring a quarter cup on a false garlic, next to the plant three earthworms came out of the soil and writhed to death in front of my eyes. I realized in an instant that this 2.2 pH is not benign - it is deadly. It has an advantage that the deadliness does not last long. The soap is to help make it deadly longer and soap itself will disrupt bodies and bacteria and fungi quite nicely too - soap is the active component in many insecticides. Then there is the Epsom salts.
Two cups is quite a lot of anything – makes you think twice about the vinegar, doesn't it? Epsom salts (not really a salt, but a form of magnesium) will act in counter to the vinegar's pH, but what does happen is not clear. Without any tests to establish what this combination does do, I'm not inclined to want to unleash it on the environment. That is the kind of shoddy work we expect from companies hawking GMO's and prescription drugs. (This paragraph was edited considerably from the initial post thanks to a reader's comment pointing out an error.)
Save your vinegar for cleaning windows or whatever the cool usage is today. Do NOT put this concoction on your plants or in your garden. It is simply not worth it. And while you're at it, look at all diy pesticides a with a little more questioning attitude and do not take them at face value.
Your garden thanks you .