You have discovered something of great value, that you can never kill all the insects there are, and you really do not want to because if you killed off all the insect pests then the beneficial insects would die of starvation because there would be no food for them.
Spraying lots of toxic stuff around, especially inside your house in winter, is not good for your health either because most of the stuff that will kill insects could cause problems with us as well. Links to the diseases you get that might have been caused by your exposure to some insecticide are difficult to establish because of the time that passes from exposure to getting the disease. Keep in mind that you cannot exist without water, but a little too much is toxic to you, it will kill you.
Water is a very good insecticde, when used properly. Add a bit of soap to water and you can get a bit better insecticide, if used judiciously. But the single best way to control insect pests is to be sure your plants are growing strong and healthy. More often than not plants that are infested with insect pests, or plant diseases, are unhealthy.

HI..
Thanks so much for the info. But when I said "Toxic" I should of worded it correctly. Not toxic sprays, as in chemical, but a natural homemade recipe of Garlic, Lemon Juice, Kneem Oil, Dish Soap, and Ceyanne powder is what I use that is "Toxic" or deadly to, any bad pests invading my trees not humans.
As for toxic chemical sprays, which most are, I do not use them. In fact you know something, I just ran across I friend I hadn't seen in years, who has been using chemical sprays for years to kill pests in his greenhouse, and he told me he has had so many health issues recently, that sometimes I wonder if those sprays contributed to his poor health? He said he has been using them for years, and can not seem to rid of his pests. He has even used beneficial pests, to no avail. Your explanation is what I am going to share with him.
I told him to stop using the stuff, and gave him the recipe of my all natural "toxic" to insects only one. Let's see how it does for him..
I have to thank rhizzo, and toni for stearing me away from those. I will admit, I was using all kinds of store bought systemics and sprays myself last year, and they did nothing anyways. Great info kimmsr, and by the way, I have seen your input before, not to often, but when you speak you are a very helpful member. Thanks!:-)

Kimm, you are mistaken about the bad health of plants being an issue for why pests invade. Grubs never attack a poor lawn....why would they, there's nothing there for them to eat. What the grub wants is a good healthy rooted lawn that will feed them until the cows come home.

Same for houseplants; they want the good stuff, the green, healthy leaves and stems where there's lots of juices to suck and eat of the foliage.

True, the more healthy a plant, better it can stand up to adversity....same goes for a lawn.
But when looking for bugs, they, like us, only dine where the food is good and plentiful.

Bugs when they are in numbers, can cause harm to a plant, can cause stunted growth, loss of bloom, otherwise wilting plants that do not live very long.

"water is an insecticide"! Where did that come?
I think you mean if you blast a stream of water at a bug, he loses his grip and so falls out of the plant...and in so doing, cant harm the plant. Yeah, I guess that counts for something too.

Many garden centres have on their shelves an insecticide that is safe for most houseplants. The label might identify the contents as being "for houseplants".
In so identifying, the contents will treat what is commonly the pests that are found on all our houseplants.
aphids, whiteflies, scale, thrips, mealybugs, spider mites and so on.
Other product labels might identify one pest in particular that it treats.

But the very best ridder --you cant beat it---is on the ends of your hands. Pick a bug up and squeeze it between thumb and forefinger. He'll never again eat at your plant. I guarantee it.
Now its his children that is the problem. They should be given the loving hug as well.

Hi. I had problems with scale and spidermites on houseplants for _years_. Some of the plants had been with me for so long, they were like family. I ended up giving away all but two when I moved out of state a few years ago. After trying several "High-octane" insectides, I was finally able to get rid of the bugs on my remaining plants using Neem oil. Since then, I keep two sets of gardening equipment-- one for my houseplants and one for the outdoor plants. The outside equipment is never brought in the house and the indoor stuff never goes outside. I have yet to have another infestation. As for my outdoor plants, I now only use Neem oil. In my experience, it is a far superior insecticide than anything else I've ever used, plus it has fungicidal properties if applied every few weeks. Neem oil is non-toxic to mammals, birds, bees and as such, is the far superior choice for any eco-savvy gardener.