Dear Brad,

Thank you for contacting Ask an Expert.  Your tree description sounds like it has a fungus, could be a couple of different fungal infections.

You need to prune all the limbs that are infected back to clean or uninfected growth. I would use pruning sealer. Wash your pruners before and after each cut in a 10% bleach solution or dip them in isopropyl alcohol. A 10% bleach is one part bleach to 9 parts water. That way you do not re-infect the tree.

You can cut or shave off the cankers (that's what they are called on trees) from the trunk and put pruning sealer on them. The wood has a different drier look than healthy wood. Get some gloves, the pruning sealer is messy and can also get it all over your clothes.  

Clean the area around the tree of all debris, fallen leaves, any decaying wood, et cetera. The tree has a serious fungal infection and yes, it can spread to other trees. You need to start a spray program right away.

There are copper sprays available, however, they are toxic to humans and can build up in the soil, so I would be very careful with them if you decide to use them. I have not heard of copperas or using calcium as a treatment.

Rex Lime/sulfur is available at Wilco and Neem Oil is available at most stores that carry plants. Follow the directions on the packages. Spray the lime/sulfur first wait about a week and spray the Neem oil. Often there are mites and other pests on the weakened trees and Neem is a fungicide and a miticide. You can also spray with dormant oil, but I would alternate between the lime/sulfur and Neem oil sprays every two weeks throughout until August. Alternating these two fungicides is a stronger defense against spores. Dormant oil is great in October, November when the tree goes dormant, it smothers any eggs of insect pests and seals again fungal spores.

In February we usually have a couple of warm weeks, spray the lime/sulfur once and Neem oil once a week later if possible. The temperature has to be above 40 degrees, dry for 8 hours after you spray and no wind (sometimes that is pretty hard to get in February here in the Willamette Valley).

Do not spray the trees with anything once the buds start to show and wait until all blossoms are completely gone before starting your spray program again. Neem oil is toxic to bees and other pollinators.

In the spring if the tree is looking good, you can spray once a month, otherwise go back to the every two week program especially if it is warm and then rainy and then warm again. Unfortunately this is a long term issue and will take one to two years to get rid of. However, that said, you should stay with a maintenance spray program after that due to our very wet and warm weather during the spring.

Water regularly, at ground level, do not wet the tree, add thoroughly composted material only to the top of the soil around the tree, do not put it right up against the tree, keep it back about 8-10 inches.
Keep the area completely clean of dead leaves or leaves that have fallen on the ground. The leaves with spots on them should be removed from the tree and thrown in the trash as with all leaves on the ground. Do not put them into your compost pile if you have one. Do not put the limbs in the compost pile, cut them up and bag them for the garbage or burn them thoroughly. Leaving them on the ground uncovered will spread the fungus.

Keep pruning back any diseased wood that you see. Use the bleach solution. And be sure to use the bleach on all tools that are used so you don’t transfer the disease to other plants. See the pictures below.  Is this what your tree looks like? Thank you for contacting Ask an Expert. Feel free to email again with more questions.