Carrots Under Attack

A readers' organically grown carrots were beautiful when she started harvesting them, but then they were full of blackish, horizontal lines and some have worms in them. Should she just abandon the crop? And how can a Weekend Gardener keep this from happening?

Welocme to the owrld of the carrot rust fly, a very common pest. Adults lay eggs on the soil around the crowns of carrots, parsnips, and related plants.

The newly hatched maggots tunnel into the roots, eat for a month or so, then return to the soil to populate; a few weeks later they turn into the next generation of flies.

The only way to stop further damage is to harvest the carrots, trim off the nasty parts, and eat or preserve the rest. But whether you eat the carrots or not, don't just abandon the crop. And don't put any of it on the compost pile. If the infected carrots are not removed and destroyed, maggots and pupae can overwinter in them or the soil near them and make things worse next year.

Prevention is tricky. Start by planting next years' crop as far from this one as possible. Try planting late: flies lay thier first eggs in May or June, so if you plant in mid-June you can sometimes sneak by them (it takes carrot seeds a couple of weeks to germinate). Be sure to harvest early as well, since the second generation of flies lays eggs in mid-August.

Alternatively, you can use floating row covers to prevent egg laying. Be sure to bury the edges in the soil so no flies can get underneath, and leave them on from planting to harvest.