Hi Ironraven,

If you find that a Citronella based insect repellent does not last long enough before repeated spraying/application then you could move on to tea tree oil based repellents such as found here

http://www.thursdayplantation.com/Product%20Sites/Walkabout50_125ml.htm

the tea tree oil based formula also has other beneficial medicinal effects being useful for skin infections (the tea tree oil soap would be useful to use also in the field). It also acts as an anti fungal and germicidal treatment as well and relieves the irritation of insect bites. I don't know if it is freely available in the US though. I don't know whether it has been given FDA approval for its use as an insect repellent, but it does appear it has FDA approval as an antiseptic.

The next step up in the insect chemical warfare would then be the picaridin preparations. I afraid I don't know if this synthetic chemical gives brain damage like the high concentration DEET preparations though.

You may also find the Nordic Summer repellent useful also available at

http://www.raymears.com/shop_item_desc.cfm?id=284&itemType=Skin%20Care