[Ccorbett83]

I am planning to overseed my front yard over Labor Day weekend but I need to apply tenacity first to kill bentgrass that is in various spots. How far in advance should I start applying tenacity as I know it takes a couple applications to kill the weeds. I was planning on starting at the end of July. Am I right?

Thanks for the help.

 

[pennstater2005]

You can apply Tenacity during seeding. It has a post emergent effect I believe lasts thirty days. So, if you are worried that new seed might not take because of a barrier it has created than I would stop 30 days before your seed down.

Here is some more info:

http://www.greencastonline.com/tenacityherbicide/golf/keybenefits-preseeding.html

 

[g-man]

Some studies on controlling bentgrass with tenacity here:

To be clear, the label calls for 5oz ai/acre rate, but a few studies found better control at lower rates when using NIS and some urea.

Based on the results of this study, Tenacity should be applied at 1.0 oz. per acre in each of three sequential applications on two-week intervals using a non-ionic surfactant plus UAN with power raking. Power raking will remove debris before each Tenacity application and allow for the greatest control of creeping bentgrass.

-http://www.golfdom.com/improve-the-efficacy-of-tenacity-for-creeping-bentgrass-control/

While other suggest 4oz rate, they all suggest the repeat applications as key. https://turf.unl.edu/turfinfo/Sept10%20Fall%20Tenacity%20Apps.pdf

Since I think you have some fine texture fescues (based on your images), a low rate (2oz ai/acre) will be safer.

 

[Delmarva Keith]

Here's an article on eliminating creeping bent.
http://hortsci.ashspublications.org/content/43/2/509.full

I've sprayed triclopyr alone on creeping bent (just hit it while spot spraying other stuff to see the result) and it did kill a good bit of it with only one app. I'd expect the tenacity + triclopyr combo to do the business.

The wait before seeding after tyriclopyr is 3 weeks so schedule accordingly.

 

[Bkell101]

Some studies on controlling bentgrass with tenacity here:

To be clear, the label calls for 5oz ai/acre rate, but a few studies found better control at lower rates when using NIS and some urea.

Based on the results of this study, Tenacity should be applied at 1.0 oz. per acre in each of three sequential applications on two-week intervals using a non-ionic surfactant plus UAN with power raking. Power raking will remove debris before each Tenacity application and allow for the greatest control of creeping bentgrass.

-http://www.golfdom.com/improve-the-efficacy-of-tenacity-for-creeping-bentgrass-control/

While other suggest 4oz rate, they all suggest the repeat applications as key. https://turf.unl.edu/turfinfo/Sept10%20Fall%20Tenacity%20Apps.pdf

Since I think you have some fine texture fescues (based on your images), a low rate (2oz ai/acre) will be safer.

GMAN....thanks for the articles. I'm new to this yard thing, but I like evidence based practice....what is your take on timing of application in terms of temperature? I may have misinterpreted, but I believe one of the articles said they had decreased efficacy of the tenacity and that may have been due to application during lower temperature.

- "It indicates that temperature and sunlight intensity both impact the efficacy of Tenacity. Our observation in another study also showed low efficacy of Tenacity in creeping bentgrass control under low temperature conditions."

However, there I didn't see a table or graph displaying temps. Could have missed it though. My understanding is that herbicides in the heat 90+ don't work great. Opposite for tenacity? I'm confused. Also because I thought bentgrass goes brown when too hot and not cared for in the heat, but that the weed needs to be green in order for the tenacity to be taken up and work. What do they consider "low temp conditions"? Thoughts?

Also, Any updates on combination therapy? I didn't see any articles that addressed this theory like you proposed? Any experience with it?