Christmas Tree Grass Management

[NorthernWIWoodsman]

First of all, I new to the forest industry.  That being said, I have heard there is a chemical that can be applied to Christmas trees to reduce the growth of surrounding grasses.  I also heard these chemicals are typically sprayed when a tree is dormant.  Here are the questions.  What chemical would this be?  When is a conifer dormant (the trees are planted in Northern Wisconsin, Price County)?

[beenthere]

Welcome to the forum. Two weeks ago I gave away my Oust and Princep, which are pre-emergence sprays and I believe safe for Christmas tree species. Best to call the State District Forester (Steve Holladay around Verona, but he should know the answer) and ask him to be sure what to use. The Christmas Tree Growers Assoc. also will likely have some suggestions what to use.
Hope to hear more about your operation and hope you join in here as well. It's a great place, which you probably already know, if you've been pokin around. 
 

[Phorester]

Ditto to the welcome and to the advice.

Herbicide usage and licensing are so different from State to State that you need to contact somebody in Wisconsin to determine the appropriate herbicides, application rates, any permits or licensing requirements, etc.