Quicksilver on new grass

[RigglePLC]

I had new grass 16 days old, growing in a cup indoors. It was Scotts perennial rye and it was about 3 inches tall.
I sprayed it with Quicksilver (contains carfentrazone). The spray solution contained about the equilivalent of about 2.4 pints per hundred gallons of a non ionic surfactant--which the label suggests may reduce selectivity.
At 24 hours some of the sprouts had fallen at an angle. At 4 days more than 50 percent of the new grass blades had tipped at an angle and were no longer vertical. It appears that a sensitive rapidly growing area near the soil line had been affected, and perhaps the rapidly growing cells had collapsed.

http://www.fmcprosolutions.com/Porta...l%20Label1.pdf

The label says that new seedlings may be treated 7 days following emergence, but mentions temporary yellowing on hybrid Bermuda grass.

This indicates the label should be believed in this case. Newly seeded grass can be treated, but 7 days after treatment is perhaps a bit optimistic.

[RigglePLC]

The above results suggest that perhaps products containing similar active ingredients...like for instance...Square One, could potentially damage new grass less than 7 days after emergence...although the label permits such applications.
http://www.fmcprosolutions.com/Home/...ne%20Herbicide

or just click the FMC advert.

[Skipster]

A couple of things I noticed:

1) You had NIS in your initial spray mix. Why? Carfentrazone usually does its job well enough without adjuvants. Unless you're targeting weeds with thick waxy cuticles or you're partnering it with a product that requires an adjuvant, the NIS really isn't needed. Just adding the NIS is probably what magnified the injury you saw on the P. rye.

2) What was your carfentrazone application rate?

3) Carfentrazone is a PPO inhibiting herbicide, so it has contact activity and doesn't really translocate. It works, in part, by dessicating cells and interefering with cell membrane stability. It is not really affected by growth stage or cellular activity.

4) Check the ai rates when comparing different products. At the highest label rates for cool season grasses, SquareOne applies 33% less carfentrazone than Quicksilver.

Just some thoughts ....

[KeystoneLawn&Landscaping]

When it comes to apps to new turf, I always stay on the side of caution and extend the time when safe to apply.

[RigglePLC]

Good points, Skip,
I normally use a non-ionic surfactant in my solutions, particularly when spot spraying, as the cost is minimal when spot spraying; I am looking for better herbicide activity.

My calculations how Square One applies about 0.03 lbs AI Carfentrazone/Acre

I think I applied Quicksilver at about 0.05 lbs AI/Acre. More, but still below the maximum label rate for moss. Of course, measuring the application rate with a tiny handsprayer is difficult to say the least. I know it took about 5 seconds to spray an ounce. And I mixed 2 milliters of Quicksilver in one quart of spray solution. The rate must, of course, be approximate.
I was hopeful that the product would be safe on new grass, even a bit over the label rate.

[greendoctor]

On a new lawn, with newly emerged weeds, herbicides with either no surfactant or 8-16 oz per 100 gallons will work. I go for the minimum needed to effect wetting and penetration. It is very different from treating old lawns with weeds that are supposed to be annuals but have turned into woody perennials.