Why do broadleaf weed killers require application in temperatures below 90 degrees?
Question:Does anyone know why weed-killer manufacturers instruct you to use their product when the temperatures are below 90 degrees? They all seem to say it, but I can't find an explanation as to why.
Also, for how long do temperatures need to be below 90? Can I apply weed-killer in the morning before it heats up, or do I need to wait for a sustained period (i.e. several days) of sub-90 degree weather.
Thanks!
Answers:
The reason manufacturers say this is that, if you apply herbicide in temperatures above this 90 degrees, you will take a chance on burning the lawn area that's immediately surrounding the weed its self. Grass blades are very susceptible to burn from herbicides when the temps reach this 90 degrees. They react very much to the temperature. If you are applying these herbicides, you want to do it when the temp is somewhat cooler and is going to "stay" at that cooler range. If you apply it in the morning and it's 60 degrees out, and by the end of the day it reaches 95 degrees, you will more than likely experience some burning of the lawn areas that were sprayed with this herbicide. After a couple of days of this cooler temp, you can water the lawn as usual as the systemic action of the herbicide will have absorbed into the cellular structure of the broadleaf weed and already will have started to break it down. Hope this answers your question..
...Billy Ray
The stoma's on the leaf close in order to conserve water therefor will not absorb the agent. apply in the morning.
A lot of herbicides are volitale. When paired with heat, their selectivity is weakened, allowing damage to be done to grass and any shrubs close to the area where herbicide was sprayed.
The plants have a stoma on the broad leaf plant. We temperatures get increasingly hot the stoma closes, and helps the plant retain water or other nutrients. If you apply the weed killer after it gets that hot, the leaf will not absorb it.I would suggest putting it on just before dark when the temperature is lower, or put it on in the morning hours before the temperature raises about the threshold.
Good Luck!
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