Pesticides are not all created equal
I'm usually not very enthusiastic about insecticides in general and I almost never suggest that you use them indoors. However, there are times when a carefully timed application of insecticide will bring an otherwise out-of-control pest situation back to tolerable levels.
Until recently homeowners had relatively few options when it came to safe and effective pesticides for use indoors. The only available pesticides were either a messy, smelly aerosol spray or an equally smelly powdered insecticide. Gardeners have a few more options like insecticidal soap and neem oil (see below) but even here the choices were limited.
Fortunately, times they are a changin' (apologies to Bob Dylan). There has been a real movement in the last few years toward natural pesticides, those derived from natural, not man-made, sources. And, pesticides that are safer for the user and the environment - the so called biorational pesticides. Not all natural pesticides are biorational and not all biorational pesticides are natural. The classic example is nicotine, the active ingredient in the tobacco plant. Nicotine is a natural pesticide because it is derived from a living plant but it certainly is not biorational because it is so broadly toxic to both plants and animals.
There's now a new category of natural pesticides called botanicals that meets both criteria of low toxicity and low environmental impact while being effective and easy to use. Technically speaking botanical pesticides are not new. Pyrethrum is one of the oldest natural plant products used as an insecticide and neem oil, from the neem tree, has been used for its insecticidal and medicinal properties for hundreds of years. What's new is the combination of plant essential oils in different formulations (aerosol, dust, wettable powder, liquid concentrate) that can be used in a wide variety of pest control situations.
Why do plants make essential oil pesticides?
Plants make essential oils, like clove oil and peppermint oil, as defense against their animal and disease-causing enemies. The oils are made in special gland cells where they can be released in response to feeding by an herbivore or attack by a pathogen. It makes sense that these same compounds could be used as insecticides and fungicides when extracted from the plants. In small doses some of these same essential oils are used for fragrance or flavor.
Are they safer than synthetic pesticides?
No pesticide is 100% safe and non-toxic. However, the margin of safety for botanical pesticides is generally much higher than older synthetic pesticides. Most "pesticide" products in the US require testing and registration by the Environmental Protection Agency (EPA) to ensure they are both effective and safe, when used as directed on the product label. Some of the new botanical pesticides are so low in mammalian toxicity that they are exempt from EPA registration.
Bottom line: if you use an insecticide indoors consider using one of the new botanicals instead of the older synthetic pesticides. They are both effective, much safer, and even smell better! The only downside is that they are somewhat more expensive but this should encourage you to use less! Use the link below for more information.