Fishermans Formula Will not harm gear and equipment. At 20%, this long lasting topical (topically applied) insect repellent is effective up to 8 hours against mosquitoes, ticks, biting flies, gnats, chiggers and fleas. Picaridin is more effective at repelling biting flies than DEET. 20% Picaridin is virtually odorless; It has a mild citrus scent added to it which quickly evaporates away.