To deter flies outdoors, remove any water or food sources that may attract the pests, and apply an insecticide to the areas where flies are most populous. Some natural products, such as basil and camphor, also repel flies.
Attractants include water sources, animals, animal waste and garbage bins. Remove these items to eliminate a large portion of the flies in the area. After removing potential breeding grounds for the pests, apply insecticide granules. The granules dissolve slowly, and they may require a reapplication after heavy rains. Do not use insecticides in areas where animals or children can reach the insecticide, and use only the amount recommended on the product packaging to prevent accidental contamination of the surrounding property.
Natural fly deterrents include basil, camphor and essential oils. Plant basil around picnic areas, for instance, and around the perimeter of chicken coops or other animal enclosures to help reduce flies. Camphor incense is a resin that is burned over small charcoal tablets to repel flies, while essential oil can be diluted and used as a spray.
To make a fly repellent with essential oils, mix 1 cup of water with 1 cup of apple cider vinegar, and add a teaspoon of eucalyptus oil and citronella essential oil. Mix the spray thoroughly before use, and spray around outdoors areas to deter flies. A similar solution that contains 1 to 2 percent essential oils can be sprayed on socks and boots to repel flies.