From Inga:Since it is garden planting time, I am wondering how to to control onion maggots since the usual powdered chemical is no longer available. What should one use to aleviate this problem?DB:We had this question Friday on CBC and a listener called in to say she had planted rows of carrots between her onions for 40 years and had not had a problem. I guess the smell of the carrots confused the flies.Other tips for control include sanitation. The last generation of larvae in the field in the fall are looking for feeding sites and they do like to feed on random onions left in the field.Gardeners should keep their sites clean and move onions to new locations frequently. If I had this problem in the past I would choose a new site in the spring - plant early and cover the crop with reemay (also known as floating row cover). This would keep the adults from laying their eggs into the new seedlings. I would also plant carrots as per the listener's suggestion- why not?Inga:Our potatoes have small black spots in several places as if infested by some worm... Also the skins are covered with 'scabs'. How can this be remedied?DB: The small holes are probably from flea beetles and the scab is from too much manure. Certain potatoes are thin skinned and more susceptible to scab, although it doesn't affect eating quality. A freshly manured field will often have the bacterial problem of scab.Inga:Carrots are also infested by black worm like areas about 2 - 3 inches below the tops. Cause? How do we get rid of this problem?DB:Again, reemay is the only cure for carrot rust fly and it only works if the fabric is put over the carrots in a new area that did not have flies last year. If you try to grow carrots where they have grown before the small flies will hatch out in spring and if the fabric is already in place they will quite happily smell and find the new carrots and lay their eggs at the top of each plant right there under the fabric..... so move your carrots to a new and clean site before adding the row cover.