The carrot fly (Chamaepsila rosae, formerly Psila rosea) is a major annoyance for vegetable gardeners. It’s found pretty much around the world and can make growing carrots difficult or even impossible. The fly itself is rarely seen and quite harmless. It’s its larva you have to worry about. The tiny white grub traces galleries in carrot roots, which then begin to rot, rendering them unusable. But there are ways of keeping carrot flies at bay.
Carrot flies can’t attack your carrots if they can’t find them… and they track the presence of carrots by a chemical component carrots give off: chlorogenic acid. Carrot flies can detect the presence of chlorogenic acid from miles away, especially when carrot leaves are damaged. Not only does chlorogenic acid attract carrot flies, but fly larvae need this acid for their survival. Without the presence of chlorogenic acid, the larvae die quickly.
And that’s why the right choice of carrot varieties can make all the difference, because there are carrots that are very low in chlorogenic acid or even totally free of it. Such is the case with ‘Fly Away’, ‘Flyfree’, ‘Resistafly’, ‘Healthmaster’, ‘Ibiza’, ‘Parano’, ‘Maestro F1’ and ‘Sytan’. These carrots don’t attract carrot flies and even if the fly does find them, they suffer little damage, because the larvae, unable to find enough chlorogenic acid for their development, die shortly after hatching.
Several seed catalogs offer seeds of carrots resistant to carrot fly. Here are just a few I’ve noted: Veseys (www.veseys.com), Halifax Seed Company (www.halifaxseed.ca), West Coast Seeds (www.westcoastseeds.com), T T & Seeds Ltd. (www.ttseeds.com) and Thompson and Morgan (www.thompson-morgan.com).