volunteer trees - Ask Extension
Hi,
I have some prairie acres with volunteer trees growing in them, mostly small twig thickness and pencil sized up to some the diameter of a qu...
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volunteer trees #868482
Asked May 14, 2024, 10:38 PM EDT
Hi,
I have some prairie acres with volunteer trees growing in them, mostly small twig thickness and pencil sized up to some the diameter of a quarter. I'm using stump-out stump and weed killer and the best time for me to do it is in the evenings, say 7PM for an hour or so. My question is how effective would it be to apply the stump killer at that time of day? I'm wondering if going into the evening is the plant shutting down to "get ready for bed" as it were. I didn't see anything on the bottle with regards to a minimum temperature but I was wondering if the cooler temps of the evening would make it less effective as well.
Thanks for your help.
Toby Meyer
Benton County Iowa
Expert Response
In general, it can be beneficial to apply herbicides when winds are calm and temperatures are cool - it can help avoid some issues with drift. Mornings and evenings are often times of the day when conditions are like this.
There has not been extensive research done on this topic. In general, herbicides will be effective regardless of the time of day they are applied. One study from Ohio State found that applying glyphosate (the active ingredient in Roundup) between 9 AM and 6 PM was more effective than applying it earlier or later than those times. However, they looked at two different weed species, and this statement was only true for one of them (giant ragweed). For the other (lambsquarters), the time of day the application was made saw no difference in the amount of control. It is also impossible to determine if these same effects would be seen in other herbicides with different modes of action.
So, I cannot say for sure that applying herbicides to these particular plants at a specific time of the day will affect the amount of control you will see. There is simply not enough research known to definitively make a statement like that. In practice, you will see control of these woody weeds regardless of when you apply the chemical.
Below are some links that can be helpful:
https://yardandgarden.extension.iastate.edu/how-to/managing-weedy-woody-plants
https://agcrops.osu.edu/sites/agcrops/files/ofr_reports/Effects%20of%20Time%20of%20Day%20of%20Glyphosate%20Applications%20on%20Weed%20Control.pdf
There has not been extensive research done on this topic. In general, herbicides will be effective regardless of the time of day they are applied. One study from Ohio State found that applying glyphosate (the active ingredient in Roundup) between 9 AM and 6 PM was more effective than applying it earlier or later than those times. However, they looked at two different weed species, and this statement was only true for one of them (giant ragweed). For the other (lambsquarters), the time of day the application was made saw no difference in the amount of control. It is also impossible to determine if these same effects would be seen in other herbicides with different modes of action.
So, I cannot say for sure that applying herbicides to these particular plants at a specific time of the day will affect the amount of control you will see. There is simply not enough research known to definitively make a statement like that. In practice, you will see control of these woody weeds regardless of when you apply the chemical.
Below are some links that can be helpful:
https://yardandgarden.extension.iastate.edu/how-to/managing-weedy-woody-plants
https://agcrops.osu.edu/sites/agcrops/files/ofr_reports/Effects%20of%20Time%20of%20Day%20of%20Glyphosate%20Applications%20on%20Weed%20Control.pdf
