Sumac & Sasafras tree disease
Sumac tends to shed leaves early in autumn and stressed trees can prematurely drop leaves. Our weather has been hot and dry except for the recent rains. The tree could just be stressed.
Sumac is subject to various diseases which can also bring on a stress response. The "black substance" is a concern. Root rot could be a concern if drainage is poor. Stressed trees should re-leaf next spring. Dropping large compound leaves can make a sumac look pretty sad. Rake away and destroy fallen leaves incase of disease. Remove any dead or diseased branches well below the problem. Don't forget to disinfect tool between cuts. Most problems with sumac usually require no treatment.
Sassafras is also subject to various diseases. This tree is pretty hardy and can put up with a lot of problems. The leaf spotting is of concern but probably not a bjg problem. Leaf curl can be a stress response, also. Cleaning up the area by removing dropped leaves can help keep down any disease inoculums. Here again, treatment is probably not required.
In both cases, monitor the tree regularly. Please contact us if you need additional help.
Thank you for your assessment of the problem.