This is actual cedar wood oil . Cedar oil is known to annoy several types of flys gnats ticks and possibly even spiders. I use it everywhere and i still get spiders in my sticky trap in the house.
There are many different origin of Cedarwood Oil, it all depends on the Cedar Tree and geographical location. This product does not specify the Cedar Wood tree. The best thing to do is to try it. Keep in mind that there are other type of Cedar Wood products and other types of oil which are effective against spiders. Having said that, there are no producrt which is 100% effective 100% of the time.