Spiders are good for the environment since they help keep insect populations in check. But if seeing cobwebs build up in the corner of windows drives you nuts, there is no need to grab the chemical insect spray to get rid of them. Instead, rub rosemary essential oil onto your windowpanes. The bitter-tasting oil is a natural deterrent for spiders, so they'll stay far away. Plus, the oil is good for wooden windowpanes, so it'll help nourish the wood at the same time.