# Before or after mowing to apply a herbicide.



## 737mechanic

I use MSMA and 24D but would like to know if it would be best to apply it after a fresh mowing or if I should apply it a couple days before I mow for best results? Or will it even matter either way?


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## Movingshrub

You need enough leaf blade and time for the weed to absorb the herbicide. So, you could cut, wait for the weeds to pop up, spray, and then cut a day or two later.


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## Ware

Keep in mind both of those can damage bermuda if sprayed in high temps, and MSMA is not labeled for use on home lawns.


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## CenlaLowell

I usually cut then try to spray early the next morning. I don't spray any herbcides in temps over 85. Good luck


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## ktgrok

The prevailing wisdom seems to be to not cut for 2 days before or after, to allow the most leaf contact with the herbicide. I did find a study though that said there was zero statistical difference based on if you mowed before spraying or not - but they did say that if you scalped it down to dirt then yeah, that would obviously effect the ability of the weed killer to contact the weeds. Otherwise, didn't seem to be a factor. Also probably depends on what you are trying to kill - my big bad is Florida Pusley that grows very low to the ground so mowing wasn't going to effect it one way or the other.


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## FlowRider

Most of the herbicides I have are labeled with instructions to not mow two days before or two days after spraying weeds.

The reasons are (1) mowing stresses the plant, and it responds to being cut by slowing its growth in order to heal the blades that are cut, which results in less of the herbicide translocating (moving into) the weed, which is how most herbicides kill; (2) mowing reduces the available leaf surface for the spray to land on, which means less chemical can enter into the plant; (3) the weed will absorb more herbicide if it is actively growing, so you want it to drink in as much of the herbicide as it can; and (4) you want the herbicides (i.e., poisons) to stay on and in the plant tissue as long as possible so it can penetrate into the tissue and be absorbed into the cellular structure and root system of the plant, so once you spray, you need to let the poison do what it is designed to do - kill the weed. Mowing takes away the exposed tissue (blades) which reduces the poison dose.

Basically, you spray pricey herbicide on a plant to kill it; mowing too soon before or after means it will be less effective, which means the weed may survive being sprayed, which means you wasted your time, money and effort trying to kill the weed....


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## ktgrok

This study was on broadleaf weeds, and showed no effect with mowing timing, but I could see how that might be different with grassy weeds. https://turf.unl.edu/turfinfo/9-7_effects_of_mowing_timing_on_broadleaf_herbicide_efficacy.pdf


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