Chapter 15 Unified Threat Management for FortiOS 5.0 : Application control : Application considerations : Automatically allowing basic applications : Syntax
  
Syntax
config application list
edit appcontrol
set options allow-dns allow-icmp allow-http allow-ssl
end
As the example indicates, DNS is vitally important to multiple other types of traffic so by default it is set to be allowed, however the other settings must be specifically enabled.