killing zoysia

killing zoysia

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bournetofly – posted 07 June 2006 23:19

I have a yard…well had a yard full of zoysia and i just wanted to let people know that this stuff is killable. Zoysia is a very tough grass because of the extensive root system called rizhomes but like any plant ..with the right weapons it can be killed. I know that when i was researching other peoples woas who have tried to kill it i found that it was a major problem for them. I had my own idea of what to do but i read everyone elses sucesses and failures and was disturbed by the notion that this stuff is impossible to kill. Does anyone out there need help killing some? If so i may be able to help out. Here is what i did and everything died and has not come back. First of all and the most important thing is to make sure that your yard is healthy. Make sure it is warm growing season ..that the grass is green and that is has water and proper fertilization. Once your convinced that your grass is as healthy as you can make it and it is growing and very green skip mowing it for a couple weeks. Let the grass literally get out of control. Zoysia gross slow and usually kind of low to the ground so just let it grow for a while and get nice and juicy. Meanwhile find and Purchase a 64 oz bottle of Roundup Super Concentrate for each 2500 sq feet of lawn to kill. So if you have 5000 sq ft of lawn you will need 128 oz of roundup super concentrate….It has a purple lable. It is 51 percent glyphosate. This is the active ingredient. Make sure you dont get roundup concentrate plus. THis has diquat ..you dont want that right away. Ill get to that later. Now be prepared to spend About 70 dollars per bottle of this roundup. You then need to find some Hi Yield or Spray grade Ammonium Sulfate. Get 3 pounds of that. Mix .17 lbs of the ammonium sulfate per gallon of water. THat is about 1/3 of a cup. Mix the Ammonium sulfate with the water before adding the roundup. Mix the roundup 6 oz per gallon. Concentration is everything. This is about 3 times the recommended dose but with zoysias rizhomes youll need alot of roundup. Apply on a hot dry day, make sure it is not going to rain. You probably want to spray down about 5 gallons of mix per 2500 sq ft of yard. Try to soak every single blade of grass. Set the sprayer to spray the finest mist it can possible spray and keep the tank nice and pressurized to help facilitate atomization of the mix coming out. Wait one day…then setup watering on the yard. Water as normal through the whole process if it is not raining adequately. Just keep taking care of your yard as if your trying to keep it lush and green, even after it appears mostly brown. After 10 days you should see a fantastic spread of nice brown dead and sick looking zoysia. Now is the time to respray again using ammonium sulfate at .17 lbs per gallon mixed with 6oz per gallon of roundup again. Make sure that it is a dry day..you dont want rain washing 70 dollars worth of roundup off your grass. Again make sure you mix the AMS first with the water then add the roundup. Wait 10 more days. If any green persists ..well that will be amazing..but if it does..spray a third time. If the green is more of a sick looking yellowed leaf …this time use roundup plus with diquat. If you still have lush green spots use the Super concentrate mix again…but trust me you wont have any of those spots unless you flat out missed it with your spray. Just make sure you dont use roundup plus with diquat until the 3rd spray. Diquat is a defoliat. It will break down the cells in the leaves on contact and kill the surface green but not the roots. Killing the roots here is the ultimate goal. Roundup wont work unless you have a nice green leaf to absorb it and take it to the roots to work. After 2 applications you should have a lethal dose of roundup in the root system. The 3rd spray you can use the diquat to eradicate the rest of what little green may exist. This should be enough to send the zoysia grass straight to Hell where it belongs. No zoysia grass will come back. Be very sure you get under shrubs and around fence lines and around foundations etc…if even one system of zoysia grass roots remain alive…eventually it will take over the yard again. If you ever see any spots of it growing in your new yard…follow the above procedure on the zoysia spots and then reseed those dead areas. I truley hope that this helps someone out. Just dont get too depressed about killing zoysia. If it lives it can die. With the right procedure it can be killed just as easily as it can live. The idea is that you want to plant new grass seed right away after you kill it…so you have to use chemicals that dont have soil activity. Roundup super concentrate with a spray grade ammonium sulfate mixed in will be your best weapon. Have fun killing.

KBilly – posted 09 June 2006 11:24


First of all, you recommend using GLYPHOSATE, a known neurotoxicant, liver and blood toxicant in concentrations way beyond recommended dosage.

Then you add in AMMONIUM SULFATE, a known neurotoxicant, liver toxicant and respiratory toxicant in concentrations way beyond recommended dosage.

The you apply twice, watering in well both times.

So, you have now @#$%^%’ed up the groundwater in your area, which ultimately feeds to the water you drink, simply to kill grass. Hopefully you have no kids playing in this yard, or learning such lessons.



seed – posted 09 June 2006 15:38

Be careful. Sodium chloride, commonly known as “table salt” is a Cardiovascular or Blood Toxicant. – Phil


KBilly – posted 10 June 2006 22:46

Yup! And so is sugar.

But you don’t put the other two in the OP on food, and you don’t use either one in the quantities the OP is promoting.

And, if *you* ever grow a third eye on your forehead from too much salt, then you may want to look up the OP and meet him for a drink. Chances are his will be well formed by then… and maybe on his kids too. But hey… it’s just a joke about serious matters… like the salt thing from you…

[This message has been edited by KBilly (edited 10 June 2006).]

bournetofly – posted 11 June 2006 17:34

Well in my 30+ years of agriculture experience and exposure to thousands of gallons of a variety of chemicals i dont have 3 eyes or cancer yet. As for the groundwater it would take more than 128 oz of pure glyphosate to contaminate the ground water. And Ammonium sulfate which is more commonly used for fertilizer is also not going to contaminate ground water in that amount or cause cancer either. If anyone is that concerned about these chemicals in these doses causing cancer i would just give up your yard work altogether. Going outside and being exposed to the sun rays and cosmic radiation is most certainly going to cause cancer and kill you long before the glyphosate or ams does.

Grassguy – posted 11 June 2006 18:30

I guess with all the round up ready corn being grown we may all be at danger. Monsanto claims that glysophate is as harmless as table salt..personally I dont believe that

bournetofly – posted 12 June 2006 20:42

Well glyphosate binds very tightly to soil. It is extremely affinitive to the elements in the soil such as magnesium and sodium and and other elements with ionic charges or cations. This makes it hard for the molecule to leach through soil down to where ground water is. Even if it did make it to the ground water the concentration would be nil and the overall toxicity of the molecule to humans is also very low if any. Our dear buddies at the EPA say that it takes 700 ug/l if glyphosate in any water sample to consider it dangerous. The most I’ve ever seen in a water sample is .1 ug/l. So nothing to worry about there. The benefits to the world of agricultural use of glyphosate far out weigh what little danger may even exist. In my instructions how to kill zoysia grass i had talked about adding ams to the roundup solution..this was to bind with the “hard” elements in the water. That way they dont bind to your glyphosate molecule when you add it to the water rendering them useless. On that note…One last thing i failed to mention about the previous claim that i had overdosed ammonium sulfate….well the lable from monsanto and many generic glyphosate products specify 17 pounds of ams per 100 gallons of water…hence .17 pounds per gallon which is what i recommended. This will greatly increase the absorbtion of glyphosate and it is proven to increase effectivness in controlling tough perennial weeds.

Grassguy – posted 12 June 2006 21:20

If the soil has a poor CEC,(sandy soil), will this allow leachment of the glysophate or is that what the ammonium sulfate is for?

bournetofly – posted 13 June 2006 18:32

In all the test data i have seen the leaching of glyphosate in sandy soil is negligible at best. It was not any more dangerous than the clay soils. The same cations exist in sandy soil making the molecule stick. As for the ammonium sulfate that was added to the water prior to putting the glyphosate, it was used to actually bind with the hard elements in the tap water. If you put glyphosate in with the tap water alone much of it would bind to these elements. Unless you want to go get some reverse osmosis water..then you would be ok but i would not spend the money. I would just use the spray grade ammonium sulfate. In a nutshell the AMS increases the effectivnes of the glyphosate because more of it will be absorbed into the plant …once glyphosate binds with a cation…the molecule is useless for trying to kill anything.

groundgirl – posted 30 May 2010 06:41

We tried to kill our ever spreading zoysia grass last fall before winter set in. We reseeded in the spring and apparently the zoysia is coming right back with the seeding. Does anyone know if rototilling will kill any remaining roots that were not killed with the chemical treatment?

ken4255 – posted 01 June 2010 08:47

I think it is most effective to try to kill grass when the grass is actively growing. (I assume you used Roundup?) Was the zoysia starting to brown up when you sprayed it in the fall? Anyway, I think it always takes at least two applications. If it’s dormant, how do you know whether it was killed? Now I suppose your problem is how to kill the remaining zoysia without killing the newly seeded grass (fescue?). I’m not sure it can be done.

mbarber – posted 14 August 2011 09:29

Our neighbor “accidentally” put zoysia grass in his front yard and it eventually covered about 1000 sq ft of our front lawn. My 1st attempt to kill it failed. Then I found and followed bournetofly’s recipe, and it seems to be a success. I killed it (and two feet beyond the edge of the zoysia), continued to water the area, and waited a couple weeks for any recurrence. Half a dozen small spots started growing again, so I sprayed them again. They are all dying now, and I’ll wait another couple weeks to make sure it’s all dead, dead, dead. I will temporarily install a metal border at the edge of my lawn, but I’m hoping my neighbor will agree to kill all of it and replace his front yard. Otherwise, I am not confident I can stop it from entering our lawn again. Thanks to bournetofly for the recipe!!

jod788 – posted 15 August 2011 10:31

Just curious – what’s so bad about zoysia taking over? I mean, I wouldn’t want it in flower beds, but I’m pretty sure my neighbors would be ecstatic if my zoysia somehow took over their yard.

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