Does dry weather affect Roundup herbicide?
 

I sprayed some weeds with Roundup about 6 days ago. A few of them died, but most of them just kind of wilted without dying. Could this ineffectiveness be related to the dry weather? I was thinking that maybe the lack of water prevents the plants from moving the herbicide where it needs to go to do its work.

Round-up is not very fast acting. 6 days is about right. After spraying I wait two weeks before applying again. Some things are just slow to die off.

Yep! Since Roundup is absorbed through the leaves and translocated to the roots, hot and dry weather can definitely have an effect. During hot, dry weather the plants effectively shutdown and go into self-preservation mode. Otherwise, 7-10 days after spraying until showing signs of "distress" isn't unusual. The QuikPro version will show signs within a couple days thanks to the addition of Diquat.

The same thing can happen with some plants if you mix it at a higher than recommended rate. The glyphosate causes the plant to begin to shutdown so the chemical doesn't fully make its way through the plant, enabling it to recover once growing conditions improve. Sometimes less and repeated is better.

I always drench the weds in Roundup, I put it on it's needle spray and completley soak each weed. All over it's leaves and stem. I use way more than the recommended amount. They are dead the next day.

- Peter.

I was concerned about the drought here in Texas causing us to waste some weedkiller.

We use a glyphosate product mixed as recommended to control growth of weeds and grasses on the fence lines. Treated several thousand feet about a month ago and it easily took 12-14 days to see any effect.

Once it did take hold, everything we treated was brown in 48 hours.

For the standard sized home/patio/driveway, I never understood using Roundup. Don't you have to go back and pull the dead weeds anyway? Why not just pull them to start with?

I burn mine with a Red Dragon propane burner. Lots more fun, and they don't come back. I use it on my fence lines around the pastures and pens near the house, and on the flagstone patios. They're gone right away.

I think it also depends on the weed type. I've read in some gardening columns that adding dish soap helps. Other sources say a surfactant is one of the additives in Pro and Plus versions of Round Up.

How old was the Round Up? Effectiveness decreases with age. I can't find it in small enough bottles to make buying it worthwhile. I've gone old school and simply pull weeds by hand, but I've got a small yard.

It's not necessary to buy "Round Up"...any 48% glyphosate product (Eraser, etc) will be the same thing. Some of the 'pro' products may have a surfactant but unless you're spraying a waxy-leaved plant like greenbrier, the surfactant isn't all that necessary.

Don't think age matters on glyphosate because we started spraying this year with some that had been in the barn for at least a year. However, exposure to sunlight/UV of Remedy (triclopyr) type products will degrade performance.

Those are neat but I wouldn't dare use a pear burner now. This place would be up in smoke in a heartbeat.

Photoreactive. Spray late evening (sundown) or eaarly morning for greatest effect.

Nope. The ones I battle with roundup simply dry up and blow away in the wind, or something. Don't know exactly what happens actually but I never have to pull them. Admittedly I tend to get on them early in the front of my house. Two reasons. One the suburb Nazi's and two I simply don't like em, so zapping them as soon as they appear is fine by me.

- Peter.

I've been using some muriatic acid that the concrete guy left behind. That seems to stop 'em. Leaves the concrete nice and bright as well.

Thanks.

Quart of vinegar.
Cup of salt.
Teaspoon of dishwashing liquid.

Absolutely, now that glyphosate is post-patent there are many generic formulations available in the market. Even Monsanto offers their own "generic" under the Ranger/Ranger Pro label.

I went to a local Farm Co-op and bought a gallon jug of Crossbow (Dow product). ($60.00/gallon)

That stuff is NAAAAAAAASTY!!!

I "accidently" sprayed a birch tree with the stuff. The tree died within the month and the following spring, I was able to push it over with my hands!

It takes about a week to tear up the weeds/grass but when it's done, you take a simple hard-tined lawn rake and scrape the surface clean of grass/weeks and even woody bushes and the like. Clean earth.

If I remember correctly, it mixes 2oz/gallon of water. I also squirt in a little DAWN dishwashing liquid...helps make the mixture "wetter" and soil, if too dry, will suck up the mixture better...thereby, getting to the roots quicker that way...

WEED ON!!!