Kudos for taking out these highly invasive trees!

Here is a link to an article from MSU that details the latest information on removal measures. Scroll all the way down to the subheading "How can I remove ToH on my property?" You will see options for management. 

To quote the article:

Herbicide application is often the preferred and most efficient option for controlling ToH. Effective herbicides can kill standing trees and roots, reducing problems with sprouts. Apply herbicides between mid-July and early fall, when leaf color begins to change. Treatment at other times of the year kills trees more slowly and may be less effective.

Numerous products are available for ToH control. Selecting a herbicide will depend on several factors including the size and number of trees that require treatment, along with the surrounding desirable vegetation and landscape features."

It then goes into detail about different herbicide application methods.

At MSU Extension, we generally keep herbicides as a last resort. Tree of Heaven is a terribly invasive species and host to the Spotted Lantern Fly (recently reported in Monroe County) and often necessitates the use of herbicide. Manual removal is often too labor intensive and takes years to be effective. Herbicide is the most effective way to eradicate an established population of TOH. 

Again, thank you for doing your part to remove TOH.