Essential Oil Spray
Essential oils are an effective natural way to deter bedbugs. In a fine-mist spray bottle mix 1 cup water, 10 drops lavender essential oil, 10 drops eucalyptus essential oil, 10 drops rosemary essential oil and 3 drops essential oil of clove (optional). Shake well and spray the solution on mattresses, furniture and other items in the bedbug-infested room. Essential oils are highly concentrated in their undiluted form, so take care with their use. Wear gloves when mixing the bedbug solution and remove from the room before you use the spray.
There are some more ideas and tips in the link above