(This page was originally published on www.nugget.demon.co.uk)
An adult Carrot Fly is a very small black fly which has been described as "a low flying miniature cruise missile". The fly is reputed to be attracted to the carrots by smell. It lays its eggs in the soil adjacent to the Carrot(s). The grub of the fly over-winters in the ground gorging itself on your carrots, pupates and lays eggs in early spring. Eggs will ideally be laid near to carrots but parsley, cow parsley,celery, (and possibly parsnips), are also liked. After the spring generation have hatched they lay eggs in June and July and this second generation hatches and matures in enough time to have another frenzy of egg laying August/September time.
Basically you will not know until you lift the crop. In severe infestations the first sign is that the carrot leaves look an orange/reddish/rusty colour. They then turn yellow. On lifting an affected carrot it will be seen that the root end will be black or dark. Close examination of what appear to be good carrots may reveal small holes in the carrot. If carrots are put in a bucket of water badly affected ones will come to the surface. This however does not mean that those which do not float are totally unaffected.
Lift the crop. There is no point in leaving them in the ground as all you are doing is giving the Carrot Fly maggot ideal board and lodgings. Give the carrots the bucket of water test and discard any which come to the surface. Of the others you may, with a bit of judicious cutting and scraping, be able to salvage something. Any you consider eatable open freeze for 24 hours, or blanch and freeze, then bag and store.
There are five options you may wish to try...
1. Companion planting.
2. Prevent the fly getting to the carrots using barriers.
3. Apply an insecticide to the soil to prevent eggs hatching.
4. Use a fly resistant variety.
5. Careful timing.
Lets look at the options...
4.2.2. I grew
carrots under loose agryl fleece with the carrots pushing it up as they grow and
I got pretty clean carrots This was in the vale of York where carrot fly is
terrible. The only problem was taking it off to weed properly which was a
4.2.3. Have you tried growing
them under that gauze matting type of thing, it has a name, but I can't remember
it. It lets enough light and rain through, but keeps the pesky carrot flies out.
It is also used to bring on early crops
4.2.4. Marshalls are selling a
new product "Enviromesh" for crop protection. It can be laid over hoops. It's
more expensive than fleece (?15.75 for 15ft x 7ft) but is supposed to last at
least 5 years.
Suggested Suppliers of Fleeces.
Pan Products Ltd.,
The first two I believe do both screens and fleece, the last only ground cover materials.
4.2.5 Agriframes - (01342)319111 7.95 UKP for 40*5 ft roll.
A local nursery sells it by the metre off a huge roll. I can't remember the price, but it was the cheapest by far and you can get it cut to the length of your beds - overlapping smaller bits is a pain.
When sowing treat the seed
drill with diazinon and chlorpyrifos, phoxim, (but see para 4.3.2. below). This
will protect the plants for about 6 - 8 weeks. Carrots not to be lifted until
the autumn should also be watered thoroughly in late August with spray strength
There are few insecticides available to amateur gardeners for the following
reasons. Firstly to do the job strong products are needed which are generally
too toxic for amateurs to use. Secondly carrots have a habit of accumulating
pesticide in the root and therefore only chemicals which are poorly systemic are
generally used. Normally the soil is treated and not the Carrot. Thirdly amateur
usage often requires different residue trials to be carried out and under EU
rules for North Europe only this can cost over 100,000 per product per crop.
Minor uses such as carrot fly is unlikely to be supported in the future.
At present only a few products have carrot fly as an approved use.
Chlorophos (PBI) containing diazinon & chlorpyrifos Soil Pest Killer (Miracle) containing pirimiphos-methyl. Both are dusts used at sowing or transplanting. Pirimiphos-methyl (Sybol) drench can be used afterwards but is bound onto organic matter and will not penetrate far into the soil.
Caution...There are no other actives approved for amateur use that I am aware of. Phoxim approvals (Murphy Soil Pest Killer) were revoked in 1994 with a sell out period to the end of 1996 (I believe).
4.4.2. The resistant
varieties like T&M 'Flyaway' (I think!) are getting quite good
4.4.3. Good Reading (5) suggests the quick
maturing variety Nandor.
Information on the following would be much appreciated:
A... Any references to trials of fly resistant Carrots.
B... Supplier(s) and prices of ready made screens.
C... Should fly ravaged Carrots be composted? Or burnt? Other suggestions?
Research Institute for Plant
Again you may find some reference to pests and diseases.
Advice on making a screen to put around your Carrots.
Washington State University.
Report on intercropping as a means of reducing Carrot Fly attacks.
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