I have two fringe trees in front of my home. One of them looks to have a disease, possibly black knot. I've trimmed a few branches but it appears to be spreading. We planted the trees about 3 yrs ago when we built the house. I'm really not looking to save the trees because I'm not really happy with them, especially since I've had to trim the one and it's very unbalanced. My question is if I dig these trees up and replace them with another tree, will it pass on the fungus/disease? Do I need to do something to treat the soil? I was considering a cherry at first but I see those are typically the ones that get the disease so probably not a good idea. Now I'm thinking about a Chaste tree/vitex. Would that be a tree less likely to contract the disease? Crape myrtle is my 3rd choice. Also, if I do dig up the two fringe trees and attempt to replant them in my rear yard, ok to trim the diseased tree and what should I do to rid the disease from the tree? Or should I just replant the one and discard the diseased tree? Thank you Kirsten
Scale can be controlled with horticultural oil sprays. Mites are pests in full sun locations. A borer is the most serious insect pest. Borers are more likely to attack trees that are already stressed or have wounds.
Phytophthora root rot can occur on plants in soil with poor drainage. Botryosphaeria dieback may occur on plants that are stressed, particularly by drought. Powdery mildew and leaf spots can occasionally be problems.
Black Knot Fungus is difficult to control. If you are thinking of removing the shrubs, I would do so and not replant. I would discard the trees.
Here are articles about the replacement trees you mention.
Since I don't know your growing zone, I would suggest you call your County Extension Office for tree recommendations for your region.