Responded on your duplicate thread.

The adults look similar to a house fly while the larva look much like what you have pictured.

the best means of control starts in the fall with good clean up of other food sources, seeding of some cover crops has been found beneficial in preventing this pest. Planting later is also a good choice as is covering the newly planted starts with a Floating Row Cover. Moving the planting beds each year is another help, but that distance should be a minimum of 300 feet to be most effective.

Perhaps this article will be of some help.

http://ipm.ncsu.edu/AG295/html/cabbage_maggot.htm

kimmq is kimmsr