Do Bug Sprays Kill Spiders? What to Look for When Buying Spidercides

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Most bug sprays sold right now have a bad reputation for not being to deal with spiders. Yes, they can get rid of roaches and termites, but when it comes to those eight-legged arachnids, the buggers just seem to be unaffected by them. So what’s going on? Do bug sprays kill spiders? Or is there a particular type of spray that you should be using?

Do Bug Sprays Kill Spiders? What to Look for When Buying Spidercides

The usual bug sprays have ingredients that can affect spiders.

What’s inside a bug spray?

As we all know, there are two kinds of bug sprays, the repellent and the pesticide. But in this post, we’re going to focus more on the latter.

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How pesticides are made heavily depends on the company that produce them. But there is a standard formula that they all follow. Generally, pesticides consist of active and inert ingredients. The active ingredients are the substances that kill the target pests while the inert ingredients are the chemicals that carry the active ingredients, all the while allowing the entire pesticide to be completely “sprayable” but sticky and viscous enough to latch into various surfaces.

According to, some of the most common ingredients for pesticides are elements like chlorine, oxygen, phosphorus, nitrogen and bromine. They also contain substances like kerosene or petroleum distillates, talc, emulsifiers and calcium carbonate.

What should you look for in a bug spray?

Pesticides that can kill spiders have specific active ingredients that are not found in other products. So if you’re going to buy a bug spray that can handle spiders, here are the 2 best active ingredients that you should look for.


Permethrin is an insecticide that’s extracted from chrysanthemums. It targets an insect’s nervous system and causes loss of muscle control, paralysis and eventually death.

Currently, permethrin is marketed as an all-around pesticide, capable of wiping out major pests like ants, mosquitoes, scabies, lice and even termites. However, a 2011 study on cobweb control in urban buildings discovered that the insecticide could actually kill spiders.

Researchers found that it reduced approximately 95% of the spiders in an area. It was able to get rid of most of them, and it even gave off a residual barrier that kept the arachnids away within the entire treatment period. It even warded off the bigger and stronger species.

If you’re interested in using a permethrin-based pesticide, check out our list of the best ones here.



Pyrethrins are synthetic compounds that have powerful insect-repelling and insect-killing properties.

Just like permethrin, pyrethrins also come from chrysanthemum flowers. And they also target the pest’s nerve cells, cutting off muscle control and causing the pest to die from paralysis.

As for their repelling abilities, a 2001 toxicological profile on pyrethrins and pyrethroids stated that we can use pyrethrins to ward off pests just by putting a small amount in an area. The tiny amount is enough to drive the arachnids and insects away just before some of them die.

So if you can’t find products that have permethrin in them, read about pyrethrins instead. And don’t forget that there are products that combine the two ingredients together, just to have that extra bit of potency. Sprays like the ones from Terro are like this, and the brand prides itself in being able to kill spiders in less than a few minutes.

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