To eliminate a fly infestation, you must first focus on its vulnerabilities. They are attracted to brightness and scent. You can kill them with essential oils and potent fragrances.
A homemade fly trap can be made that works indoors or out. These flying insects love fermented apple juice or Apple cider vinegar traps. A repellent spray is another effective way to eliminate insects.
Lavender is known for its pleasant scent and ability to repel insects. In addition, the faint clove scent repels flies. Combining lemon and this little spice will make an effective insect repellent.