The best mosquito repellent for your patio costs $20 and runs on a wall outlet: a fan. Mosquitoes are terrible fliers with a top speed of about 1-2 miles an hour, slower than you walk, and they struggle to make headway against even a gentle breeze. Point an oscillating fan at your outdoor seating area and they'll physically struggle to get to you. It works on two levels too. A mosquito finds you by following the plume of carbon dioxide you exhale, plus the heat and scent rising off your skin. A fan scatters all of it and erases the trail that leads them in. So it knocks them out of the air and helps hide you from their senses at the same time. This isn't folk wisdom. The CDC notes that fans reduce mosquito landings, and studies have found that using a fan can substantially reduce mosquito bites. Citronella candles offer only modest protection and are generally much less effective than a fan or EPA-registered repellents. Plug in a fan, aim it at the table, and take your evening back.