Lavender oil is another powerful plant extract that is commonly referred to when discussing DIY ant repellents. Lavender flowers are known for their strong scent and are often used not just as pest repellents, but also in perfume. Generally speaking, human beings like the smell of lavender. To the contrary, pests like ants, flies and mosquitoes are not too keen on its smell. In fact, many store-bought natural pest repellents already contain lavender oil.