Spraying Roundup and time before rain

ryanwheelock · Jun 17, 2010

I'm sure its in the booklet when you buy roundup but how much time is needed to get a good kill before a rain.
Thanks
Ryan

Ron Anderson · Jun 17, 2010

2 hours

rrlund · Jun 17, 2010

The Hefty brothers claim the tissues start to shut down immediately after application,like getting stung. They claim it's a waste to even go back and spray the same plants over during application. If you do get a rain right after application,they say wait a week to 10 days before reapplying IF you don't get a good kill.
I got soaked one time before I even got to the road after spraying a field and I got a good kill. Didn't have to go back and clean it up,so 5 minutes is more like it.

randallk · Jun 17, 2010

Gly-4 Plus = 2 hours, Roundup Power MAX= 1 hour, Roundup Weather MAX = .5 hours.

bradk · Jun 17, 2010

I'm pretty sure the label I read one year said 3 hrs for maximum performance.

Roundup with weathermax has a quicker absorbing agent and has a 30 minute rainfast warranty.

Dave Sherburne NY · Jun 17, 2010

Used to be 3 hrs when I was a commercial applicator
back in the 1990's. Don't spray when the dew is
on either.

CNKS · Jun 17, 2010

I don't know about that -- I try to spray early in the day when the wind is "down". In Kansas it is almost never under 10-15 mph. I have probably sprayed 90% of the glyphosate when there was dew. If the fear is runoff, and you are using 10 gpm of water or less, you don't get much runoff. AND the pores in the leaf are open and ready for intake. I have always believed that the best time to spray anything is early in the day. Worst time to spray is when it is hot and the weeds are under stress. I heard the Hefty brothers on RFD TV say not to spray when there is dew. In almost 40 years they are the first ones I have heard say that, you are the second. 30 of those years were as an agronomist for Kansas State University. The Hefty's are right about many things, but not all.

agpilot · Jun 17, 2010

Hi CNKS: I tend to agree with you. I got best results w/24D very early in the day,,, starting half hour before sunrise.. This was (years ago) in dry Western wheat country... Different chemicals get diff results, of course. I almost never got good results when the crop was under lots of stress.. almost wasn't worth doing but the farmer said "Ya, I know but do it anyway" so I went. That was always the hard part of doing that job and it bothered me to not be doing a good job... ag. (ret)

Mark-Mi · Jun 17, 2010

I had it pour 15 minutes after application and had good results. Mark

Dave Sherburne NY · Jun 17, 2010

Depends on the chemical if it is meant to stay on the plant and be absorbed by the plant most of it will bounce off when it lands on a plant saturated
by dew. If it is meant to go to the ground and be taken up by the roots, the best time is early in the day, when there is no wind to cause drift, and starting early allows you to get more done. The chemical will lay on the ground and dry out and not go to the roots till a rain or heavy dew causes it to be absorbed into the soil and to the roots.

JMS/.MN · Jun 18, 2010

The variety of answers here shows you why you should read the label. What you are looking for is "rainfast".

Rootsy · Jun 18, 2010

Don't skimp on the application rate either... All that does is promote glyphosate resistant weeds...

Spraying Roundup and time before rain

ryanwheelock

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Ron Anderson

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rrlund

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randallk

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bradk

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Dave Sherburne NY

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CNKS

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agpilot

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Mark-Mi

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Dave Sherburne NY

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JMS/.MN

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Rootsy

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