I have read that carrot flies only fly below a certain height and that erecting a barrier around your carrots you can prevent/reduce carrot fly attacks

How intelligent are these flies?

If my carrots are in pots on my decking or on top of my picnic bench does this count as being high enough to be out their flight path? Would I still require a barrier around them? Or would carrot flies go up and over?

Hope someone can help

Karen