Is Crossbow a good choice for killing wild blackberries?
I can find lots of information on what Crossbow kills but no specific information on how it does it. I am trying to kill wild blackberries. My yard is in a condo development and is right next to my neighbor who does not like herbicides. She tells me that if I spray the blackberries that are next to her organic fruit tree, the herbicide will transfer to any roots in adjacent plants and kill them. From what I can see, Crossbow acts in the same manner as Roundup, traveling from the leaves to the roots and killing or damaging only those that have leaves sprayed.
Can you give me some information on how it kills plants and if the herbicide is transferable to other plants via the roots?
First, I should tell you that Crossbow is not labeled to be used in residential yards. You should pick another approach/product in this setting, but I want to go further to answer your question.
Crossbow has two active ingredients: 2,4-D butoxyethyl ester and triclopyr butoxyethyl ester. You can read about their "modes of action" in the NPIC collection of technical fact sheets (http://npic.orst.edu/factsheets/archive/index.html).
I think you're asking, "Will the Crossbow hurt my neighbor's fruit trees?" The answer is likely yes. The label for Crossbow says, "Do not apply Crossbow directly to, or otherwise permit it to come into direct contact with ... fruit trees... and do not permit spray mists containing it to drift onto them." In another section, "Under conditions which are conducive to evaporation (high temperatures and low humidity), vapors from this product may injure susceptible crops growing nearby." Here is the label information for Crossbow (https://www3.epa.gov/pesticides/chem_search/ppls/062719-00260-20091106.pdf).
I'm glad you reached out before making an application. There's a lot of great advice/information in this OSU publication by Max Bennett, Managing Himalayan Blackberry in western Oregon riparian areas (https://catalog.extension.oregonstate.edu/em8894).