Hi, Dianne!
Thank you for reaching out to UNH Extension regarding the growths you are finding on your tree.

Good news first - the green growths are lichen, which are not harmful to your tree and are only found in areas of very good air quality (yay!). You can read more about lichen here: https://extension.unh.edu/blog/2019/04/should-i-be-worried-about-lichens-growing-bark-my-apple-trees

Now onto the black growths - those look to me like they are black knot fungus (more about that here: https://hort.extension.wisc.edu/articles/black-knot-apiosporina-morbosa/). Winter is actually the perfect time of year to prune and treat black knot, so your timing is excellent. 

Some recommendations on how to manage the disease are below, from this UNH Extension article: https://extension.unh.edu/blog/2018/01/my-plum-tree-has-black-fungus-growing-branches-what-can-i-do-treat-it#:~:text=Trees%20infected%20with%20black%20knot,that%20appear%20on%20infected%20branches.

Control of black knot requires both prevention and sanitation. Prune out all infected branches in late winter (late February through the end of March) and destroy them by burning, burying, or throwing them away. Remove at least 3-4 inches of healthy tissue below each knot to ensure elimination of the fungus. Heavily infected trees should be removed completely, including wild host trees such as black cherry (Prunus serotina). However, the most effective way to avoid issues with black knot in the future is to plant resistant varieties of plum.

Please know it might take a couple of years of winter pruning efforts to bring your tree back to health. You should see a reduction in the growths over time, however if they continue to overtake the tree, you might want to consider replacing with a resistant variety to save your sanity. :-) It can sometimes feel like a losing battle out there, but we are here to help whenever you need it. Take care, Michelle