According to reports from across the Prairies, you’re not alone. In Manitoba, the weed has been found in fields from Swan River down through the south-central region.
Jimsonweed (Datura stramonium) is an annual broadleaf with white/off-white trumpet-like flowers on stalks that can grow over 5 feet tall. It reproduces by seed that is contained in spiny pods (see Figure 1). This weed isn’t new to the Province but it’s only occasionally a problem. Although seed contamination is being considered, it’s just as likely that warm temperatures and less competitive crop stands contributed to increased germination and establishment of existing weed seeds.
Recommendations for Control:
Crop Rotation: Jimsonweed is not overly vigorous, so rotating to competitive crops like cereals or canola will help with control. The weed tends to be a bigger issue in less competitive and later season crops, including corn and soybean.
Herbicides: Although Jimsonweed doesn’t show up on many product labels there are lots of pre- and post-emergent herbicides that should provide control including glyphosate, glufosinate and various group 2’s, 4’s 6’s, 14’s and 27’s (www.msu.edu/~zandstra/Weed-Chem/jimsonweed-Chem.htm**; 0= no activity, 1= good to excellent, 2= fair to good). **Only use labelled applications of herbicides registered by Health Canada.
Application timing: Like most weeds, herbicides are most effective on Jimsonweed when it’s small. Because it’s a later germinating weed, it might be ‘missed’ by early herbicide applications but be too large for some later herbicide applications.
Rouging or cutting: Hand-pulling or cutting Jimsonweed before it sets seed is also an option, depending on the number of plants and their distribution in the field. Seed growers may need to put this option into play this fall since Jimsonweed is a prohibited noxious weed seed under the Weed Seeds Order (http://laws-lois.justice.gc.ca/eng/regulations/SOR-2005-220/page-2.html#h-4). Jimsonweed seed can be similar in size to canola.
Submitted by: Jeanette Gaultier, Provincial Weed Specialist, MAFRD
Visit MAFRD Crop webpage for more current topics: www.gov.mb.ca/agriculture/crops/seasonal-reports/current-crop-topics.html#agronomy