# Burn down before planting



## Swv.farmer (Jan 2, 2016)

How long does Roundup have to stay on before it will kill.
Just say I sprayed and 4 hours later it came a rain will it kill the weeds


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## somedevildawg (Jun 20, 2011)

Swv.farmer said:


> How long does Roundup have to stay on before it will kill.
> Just say I sprayed and 4 hours later it came a rain will it kill the weeds


Did you use surfactant or adjuvant? Seems like 3 hours is the minimum but I think that has a lot of variables to be factored in...available sunlight, humidity, time of day, rate of application and rate of rainfall. 
I believe I would wait and see, unless it's a small tract then I might opt to respray depending on the other variables.....


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## haybaler101 (Nov 30, 2008)

I think generics and plain round up is an hour. Weathermax, spray in rain.


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## Vol (Jul 5, 2009)

You are probably OK, but it would help to know your version type.

Regards, Mike

http://www.simsfarm.com/images/E0162301/Rain_Free_Chart[2].pdf


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## IHCman (Aug 27, 2011)

With Cornerstone I always figure at least an hour then feel I'm safe.


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## Swv.farmer (Jan 2, 2016)

I used Roundup Max and about 4 hours after I finished it rained a tenth of a inch so some of it was on about 5 hours and the rest around 4 hours.


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## somedevildawg (Jun 20, 2011)

Swv.farmer said:


> I used Roundup Max and about 4 hours after I finished it rained a tenth of a inch so some of it was on about 5 hours and the rest around 4 hours.


I wouldn't re-spray.....


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## Vol (Jul 5, 2009)

Swv.farmer said:


> I used Roundup Max and about 4 hours after I finished it rained a tenth of a inch so some of it was on about 5 hours and the rest around 4 hours.


According to the chart, you are more than in the clear.

Regards, Mike


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## pede58 (Oct 27, 2015)

It will tell you on the label where it says "rain fast" usually 20min-2hrs, but have sprayed in the rain(nothing heavy) just to finish a round or last little section and could see no ill effects.


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