Dear Jennifer,

I have found quite a bit of information for you on Verticillum Wilt. Unfortunately, it can remain in the soil for "many years". No source was willing to put a specific number of years on it.  There are some controls that can help in the eradication of Verticillum Wilt in the soil, both chemical and soil solarization.  I have included links to both, as will as more information. You will be doing the right thing by eventually choosing resistant plants to put in place.   There are lists included of what species are susceptible and which are not. Best of luck. I think that you will eventually be able to plant the new shrub, it may just take some time.  It looks like careful attention to keeping the fungus out of future plantings is important. I hope this information is helpful. Please contact me if you have additional questions.

Information on how to do soil solarization: Soil Solarization for Gardens & Landscapes Management Guidelines--UC IPM (ucanr.edu)

General information: Verticillium Wilt of Trees and Shrubs – Wisconsin Horticulture

More information, slightly more technical: Verticillium wilt (apsnet.org)

Dear Jennifer,

My apologies for the delay. So much to do...   You are correct, the Colorado State source is reputable.  I'm sure four years will be a good number, but I'm guessing it is not an exact science.  I do think the solarization may help and may shorten the time needed. As a general rule, any extension or edu website should give fact based information. In the case of wilt, the state does not need to be all that close. Anything to do with planting zones though, you'll want a  university in the same general area. But a pathogen doesn't really matter as much I'd guess.  Unless weather, ie. heat/cold temperatures might make a difference. It does  not appear to be the case with verticillium wilt though. Patience seems to be the winning answer here.  Good luck with your future plantings,