In my pruning time disease considerations (this link opens Google Drive with this year’s recommendation for trunk disease management), I refer to Topsin-M as a choice of trunk disease management, especially for Botryosphaeria canker, which is very common in our area. The product has been transferred to a new company this year, and hence, there are changes in the label. [The US distributor is still the same (UPI), thus, I do not think it will affect where you can purchase the product.]
If you are using Topsin-M for pruning wound protection, please update your label. You can download the new label by clicking this link (will open Google Drive).
Also, speaking of trunk diseases, I have been involved in a big research effort to develop management strategies for various trunk diseases. Please check our project page which contains not only research reports, but also extension information, such as disease keys, management guides, and economic tools to estimate the benefit of trunk disease management over the life of a vineyard.