One can use IPM (Integrated Pest Management) which says to use the least toxic product that will kill the pests. It recommends organic control but also suggests the least toxic insecticide that will do the job. Meaning, one doesn't go to the cabinet and get an insecticide that kills everything it comes into contact with. It also suggests limiting the spray to the infected area and only when the pests are present. This is just common sense, but many people spray to prevent insect pests which may cause some to build up a resistance to a particular insecticide. If we all used IPM, there'd be no problem but we usually go for the big guns right away. When I give programs and the topic of insecticides comes up, I recommend IPM. I'll recommend putting up with insect damage but if one has to spray make sure the label lists the pest and mix at the dilution rate listed on the label. Not all of us are willing to walk past an insect damaged bud or leaf. I figure the insects need to eat also and I choose butterflies and birds over insecticides. It takes a few years to get to a good balance of nature and just one insecticide application can take you back to square one. But if one has a perfect leaf or bloom phobia and they have to spray insecticide, use common sense. Remember also, you can sterilize your garden but if you're the only one in your neighbor hood doing it, you'll soon get the buggers back. It then turns into a vicious cycle. Then if you try to let the predatory insects keep your bad insects under control, remember they won't return until they have something to eat. This means you'll have damage again until they arrive in sufficent numbers to make a difference. Caterpillars eat leaves and many turn into butterflies. I'm not going to stand on a soapbox and say spraying any insecticides is terrible. I'll tell people what works for me then let them make the choice. Taking a hard line against insecticides is not much different than entolling the virtues of fresh human waste as a home fertilizer or insect/fungus spray. We all know how we felt about that! The leaves on my General Jacqueminot look like lace from rose slugs but I'm willing to put up with it. Not everyone is!

I don't know that substance, but fungus gnats come largely from overwatering. Correct the watering problem & the gnats will go elsewhere for their water, no chemicals needed. How is it applied? Do you know if it's liquid or powder, for instance, a spray on succulents, is generally inadvisable. I can't say w/out more info; let's see what others think.

Spider mites are often caused by warm, dry conditions. A good rinsing will help get rid of most of them. You can help keep them away with a humidifier (in heated or air-conditioned spaces) or by keeping a window open. You can also set the pots above trays of water, add gravel to your saucers so that they can hold a little water away from your plants, or put a baking dish of water on the radiator. Produce a mild breeze with a fan; good air circulation will also help with things like powdery mildew. It's important not to overwater; herbs are especially sensitive to this. Let the top inch of soil dry out before watering thoroughly. Make sure all of your pots drain properly (water runs out the bottom when you water them) and never let the plants have "wet feet", in other words don't ever let the pots sit in even a small amount of water. A spray consisting of a teaspoon of baking soda to a quart of water, with a drop or two of dish soap, will help kill powdery mildew. Apply every week or two until the problem goes away. Meanwhile, promptly remove and throw away any branches that become mildewed. Even though I don't have any outdoor growing space in my city apartment, I've been able to rig up a sunny outdoor window box that can grow herbs pretty well. Is this a possibility for you? Neem is "organic" but I wouldn't want to eat it, partly because it smells like a cross between garlic and peanut butter and tastes terrible. Some of those other sprays, even if they're "environmentally friendly," sound even worse. If you can't grow herbs indoors without sprays, I'd suggest getting rid of them. You'll get cleaner, healthier produce at the farmer's market, and there are plenty of houseplants that are more tolerant of the indoor environment.

Neem smells nice imho. Kinda citrusy. I believe Lowe's carries it. Sulfur dust(you can mix with water and spray) also works well for a general fungicide/miticide. You want the pest control grade, not the nutrient. Probably available at a local nursery or online. Good Luck. Kevin