Scentless chamomile, as its names suggests does not have an odor when you crush plant parts and when you look at the finely divided leaf segments with a hand lens they are spine tipped.  Pineapple weed is a closely related plant and in early vegetative stages looks very similar, but pineapple weed has a distinct fruity odor even as a seedling (leaf segments are also spine tipped). 

Scentless chamomile is expanding its range in NW Minnesota.  For a period of years this plant was found primarily around Thief River Falls, but now is found scattered in areas from Roseau to Crookston and is probably moving with infested farm equipment and crops.  Scentless chamomile acts as an annual, winter annual and short lived perennial.  Early season tillage controls most winter annuals, but this plant has an extensive fibrous root system that holds a large amount of soil and can re-establish itself if soil conditions are moist.  Scentless chamomile thrives under wet conditions and the seeds are reported to float and may move into fields when ditches flood.  A number of herbicides have activity on this weed including Curtail, Stinger, Express, Harmony Extra, glyphosate, bromoxynil.  Scentless chamomile is more of a challenge to control in conventional soybean production.  Control should be focused on plants in the rosette stage before they bolt. 

Flixweed looks grayish green because it is densely covered with star shaped and forked hairs.  The crushed leaves have an old moldy basement smell to us, but some references call the odor foul.  The leaves of flixweed are pinnately divided one more time than tansy mustard (compare Figures 4 and 6). 

Flixweed is widely distributed in NW MN but is observed more on field margins, or in un-cropped disturbed areas, or in winter wheat.  Flixweed grows both as an annual and as a winter annual and tillage is an effective means of controlling the winter annual form.  This is not a very competitive mustard species and is certainly less competitive than wild mustard.  Flixweed is not very difficult to control with herbicides (control is very similar to wild mustard), but interestingly it is more somewhat more tolerant of 2,4-D than it is to MCPA.  The tolerance of flixweed to herbicides increases as it reaches bolting (and later) stages of development. 

Tansy mustard also grows as an annual and winter annual and looks very similar to flixweed until you look at leaf hairs and the divisions of the leaves.  This plant is found throughout the region but is much less common than flixweed.   Control of this plant is similar to flixweed.