It has also been suggested that the toxic chemical in mothballs will bond to garden soil, causing permanent damage to it. Research has shown that a weak bond can occur, but naturally occurring soil microbes will break down the toxic component of mothballs over extended periods of time. In addition to this, the toxic effects of mothballs may also kill beneficial soil insects. By far, the risk of using mothballs in the garden - involving children, pets such as cats, and other animals accidentally ingesting exposed mothballs - outweighs any benefit of killing unwanted animals
Rules that one out for me.
I've only really beaten the carrot fly once, that was in my first year of gardening, when I had no idea any such thing existed, seems ignorance
is a defence.
I sow late now and grow autumn carrots, because I hate losing a crop, it depresses me deeply.
Some of the old boys, on my site grow their carrots in the open and have beautiful crops, no idea what they're trick is.