There are dog safe mosquito repellents on Amazon. I live in an area with lots of mosquitos as well. Here's a link to the one I bought for my dog: https://www.amazon.com/dp/B01987CT1I/ref=cm_sw_r_cp_apa_i_HEx.EbD8088DW
Just make sure to test in a small area of their skin to see if your dog is allergic or irritated by the repellent.
This one](http://Vet's Best Mosquito Repellent for Dogs and Cats | Repels Mosquitos with Certified Natural Oils | Deet Free | 8 Ounces https://www.amazon.com/dp/B01987CT1I/ref=cm_sw_r_apan_i_T41VGCAY1RF18CP5GZ88?_encoding=UTF8&psc=1)
We don't have a mosquito problem where we camp- it's a regular spot and the land is quite dry. The fucking black flies though.... So the reviews that complain about it not working for mosquitoes don't deter me a ton. Citronella and lemongrass work for the horses at the barn I worked at for these bastards, so I know it'll help!
Worth noting it contains lemongrass and if your dog is a licker, don't apply where they can lick it. Mine aren't so not a big worry.