The carrot fly is an tiny, evil flying insect which can easily decimate the carrot crop you have so lovingly created and tended. It has a very sharp sense of smell which will direct it to its chosen root where it lays an egg which, when it turns into a grub, burrows into your carrot and usually makes it inedible.

In brief, this little pest starts out as an egg, then a grub (pls see
pic) which eats those circular holes in your carrots before maturing
into the adult fly whereupon it takes off to mate and the whole cycle
starts once more.
If your crop is unprotected against carrot fly it could easily be infested more than once in any given growing season.


The carrot flies fly only a few inches above ground so any unprotected
crop at ground level is fair game for them. One very effective method of
avoiding infestation is to plant your crop in raised beds or tubs which
are higher than the pest normally flies.
Another method is to purchase some insect proof netting which not
only frustrates the carrot fly's efforts to lay eggs on your crop but
also allows air and rain to come through
An even less
expensive of keeping the carrot fly at bay is to plant with alternate
rows of onions, starting with a row of onions nearest the front edge of
your plot. The onion smell masks the lighter smell of the carrots so the
fly leaves well alone.
A number of gardening experts will tell
you that the carrot fly invasion has finished by mid-June, but that
depends on where you live in our country where the growing season varies
so much due to the different temperatures in the North, Midlands and
South. I keep my nets on until it is time to pull the crop.