The fleece (floating row cover) works if you are in a garden area where you previously didn't have the carrot flies during the previous year.

Suggestions:
1. Do a search for 'carrot fly + United States' for some of the latest updates on possible organic controls. It appears that planting chives along the carrot rows may be helpful. Also using tightly placed row covers helps.

2. If the fly is present in the soil, crop rotation each year with new soil added may help. On a hunch, try my old time method for combating larvae that burrow into root crops. At planting time make the furrow and liberally scatter granulated sugar and fresh, unperked/uncooked coffee grounds along the furrow. Plant carrot seeds. In this situation where the fly is attracted by odor I would repeat this process on top of the furrow after it has been filled in. Repeat again every two weeks over growing carrots. This method is easy to do and well worth trying. I have used it, as have my customers, for years successfully.

Going to try this. I REALLY HATE CARROT FLY!!! And I have doubts about getting enough water if I use row covers. Low water seems to cause splitting in my soil.( Zone 6 North east MA) So the following questions are serious:
Do I put sugar and coffee grounds on soil surface every 2 weeks? Seems like sugar would draw ants, and their attendant issues?
Caffinated or non?
How fresh? Fresh ground, or fresh from store ground package? (I grind and brew every day, religious thing)
Do you mulch as well?
Reading lots of forums I have noticed that mid summer plantings seem less affected. Do you use this method all the time?
Thanks for any info!

QBush, I note that you have retrieved one of my old posts which always seems to raise the alarm that my sugar/coffee treatment which discourages root crop insects will attract ants. No worries, it does not. FYI, I have known of and worked with this treatment beside my Dad since the days of Victory Gardening in WWII and he was a well known garden writer and broadcaster in Boston.

So, press on; the least expensive ground caffeine type coffee works, plus sugar just as I have described above.

Nandina
Thanks!!! Ground coffee on the list, new carrot planting next!

There are a number of things one can do to reduce the damage done by the Carrot Fly, Floating Row Covers (fleece) or barriers about 2 feet high along the planting rows, Intercropping/Companion planting, planting later, better spacing to reduce, if not eliminate, thinning, are some.

Here is a link that might be useful: Carrot Fly control

Thank you for these replies!
Kimmsr - The link was especially helpful. I learned that I have been planting at exactly the wrong time, and my spacing is to close. So Today I am going to do a test sowing, using barriers, and Nandina's method. Right now I have enough open space in harvested beds to try both separately.

Oddly, information ion the linked site the indicates that you should never leave carrots in the ground after January. To date the best carrots I have gotten were Meridia, planted late Sep 2011. I had a minimal yield, but they were perfect: long sweet, nonsplit, and UNBITTEN!!! And I used none of the clues I am so painstakingly learning now. I guess it is a good thing I really enjoy watching seeds sprout and grow!

Well I got this advice just after i had planted a nice new bed of Carrot Adelaide, smack in the middle of the CRF second egg laying season. I wasn't expecting this bed to do anything much, so imagine my surprise when I accidentally pulled a handful of perfect carrots while weeding the beets in next area. The following day I pulled the entire bed, and found only a few carrots infected with CRF larvae!!! Did I just get lucky and miss the fly because of warmer, earlier season? Or did I pull the carrots when Adelaide SHOULD be pulled, at a small baby carrot size? Combination?

So I steamed them and we had them with yellow beans. DH said he could eat them 5 days a week, (DH speak for 'worth all the fence pole digging, manure hauling, and weed whacking') DTAB (dear teenage boy) agreed, with his mouth full! So I guess the two other beds I have planted, following Nandina's advice re sugar and coffee will be eagerly awaited.

Todays crop, with the larvae infested few at top. This is a nice change!

Update: The sugar and coffee method above worked well this year as well. Carrot Hercules, planted at foot of snow peas had coffee/sugar in furrow, and one surface application. 20 feet gave a good yield, with only about 10% damage. Since this was planted as a full sized carrot I waited until July 20 to fully harvest the bed. This is in the middle of the season for CRF damage, so I find 10% damage acceptable.

Link from kimmsr very informative, and I have it bookmarked for future!! Going to try scallion interplanting next year, and row cover for next July planting.