Mark VanGessel, Extension Weed Specialist; mjv@udel.edu
Jimsonweed, Datura stramonium, also known as thornapple, is one of those species that is quite recognizable because of its showy white flowers, thorny seed capsules and distinctive odor when the leaves or stems are crushed. It contains various alkaloids,chemicals which have effects on humans if ingested. I am not aware of any issues associated with skin contact. In particular, those growing vegetables need to be scouting for jimsonweed and keeping it under control.
Jimsonweed is a summer annual. I have seen more often in the past couple of years and have gotten a few questions about it. I do not have a good explanation for why it is becoming more common, but talking with colleagues in other states they are noticing it more frequently as well. There is only one report of herbicide resistance for this weed, so that does not seem to explain why we are seeing more.
Jimsonweed is susceptible to many common herbicides including atrazine, Command, Callisto, Basagran, dicamba, 2,4-D, Liberty (glufosinate). Metribuzin, Valor, and Reflex are fair to good on it. The Group 15s (metolachlor/Dual, acetochlor/Harness, pyroxasulfone/Zidua) and pendimethalin/Prowl provide little to no control.
In a five-year emergence study, jimsonweed emerged much earlier in conventional tillage than no-till. Under no-till conditions, 85% emergence did not occur until mid-July (one of the latest emerging species). So maybe we are seeing more of it because of its later emergence and while use of postemergence sprays often includes a residual herbicide, the residual herbicides commonly used in soybeans are not effective for jimsonweed.