Sumacs generally are pest and disease free. They are short lived so will eventually attract some pests or disease simply as a function of growing old. Then it is time to remove them.
Unfortunately when most folks think of Sumac, they think of Poison Sumac (Rhus vernix). This plant is quite toxic to the skin of humans and is combined right up there with poison ivy and poison oak, as a plant that humans want to have nothing to do with. Some botanists classify this plant under the genus Toxicodendron with the poison ivies. Fortunately, you are not likely to see much Poison Sumac, because it is found mostly growing in standing water in peat bogs in the Northeast and Midwest and in swampy areas in parts of the Southeast. If you are hiking in such an ecosystem, you need to be careful because the plant will cause serious skin rashes and much discomfort.