Hi last year was my first time i got my allotment both my rows of carrots got carrot fly i was just wondering is there any ways of preventing this apart from raised beds which plan on doing in winter.many thanks for advice in advanced.
I don't know much other than that they don't fly very high off the ground so try a barrier of some sort. If you put 'carrot fly' into the search box at the top of the page here, there are lots of useful links including a video of Monty Don deterring the little blighters!
Keep a layer of fine horticultural fleece over them, my friend has had wonderful carrots since she started doing this.
It is said that growing onions nearby helps, as the onion fly and the carrot fly get confused about the smells.
Don't thin out until late in the day, as they can smell that from a very long way away. A physical guard like fleece does the trick very well.