Are mosquitoes prevalent in Croatia's Plitvice National Park? At least in July. My guidebook has a few warnings about Zagreb but doesn't say anything about the park. Usually places with water and trees have plenty of mosquitoes.
We were there (late) July - (early) August 2014 and didn't have any problems. As previous contributors have said, always carry bug spray anyway (Lidl do one that's pretty good) and take plenty of water to drink.