Even if you don't know much about bugs, there's a good chance you know plenty about mosquitoes. Their mere presence is enough to send a mob of people ducking for cover. Not only will mosquitoes stick their long and pointy suckers into your skin, but they will leave evidence of their bite with an itchy red bump that lasts for days. Mosquitos can also spread dangerous diseases such as the West Nile virus to people and heartworms to dogs and cats. If you have them in your garage you likely want to get them out of there -- and fortunately you can.
Eliminate any water sources in your garage. Mosquitoes lay their eggs in standing water, which will increase their population in your garage. If your roof leaks and causes puddles on the floor, you'll have to get this fixed or else you'll continue to have water and mosquito issues in your garage.
Fix any holes or gaps in your garage walls or windows that allow the buzzing bugs to come inside. Replace any torn screens and fill in any gaps with caulk or similar material. Even if you kill the bugs that are inside your garage, more will continue to come inside if they find a way.
Spray an insecticide inside the garage to kill the mosquitoes. Wear long-sleeved shirts and pants, along with gloves and a face mask when applying the spray. Pay special attention to the corners of your ceiling and floors, as well as behind any furniture; basically, any dark, secluded spot is a good hiding place for the biting bugs. Apply the insecticide to your garage door and windows as well. Most insecticides are simply sprayed directly to the offending surface; however, read your product's instructions for best results.
Place citronella-scented objects around your garage to prevent mosquitoes from coming inside. Springs of rosemary and sage situated around the garage can also serve as effective repellents, as well.