Although we know DEET can be harmful, we use it because it is the only thing that really works. Citronella is at best only partially effective. A powerful compromise is to concentrate a DEET application on your clothes, socks, and hat. Avoid direct application to the skin until you just can't take the bugs another minute. If you are allergic to bee stings, be sure to include an anaphylaxis emergency kit with your personal first-aid kit and consult your doctor before going outdoors.
Bug nets are light, cheap and can be a lifesaver.
You can get nets to fit over your hat and face to keep bugs at bay while hiking, and you also can put bug nets over your face while sleeping. You can also put on your rain gear to prevent bites and stings, but be sure to drink enough liquids to avoid dehydration once you are all bundled up. .