Hi Pepper! Welcome to Goy! Would be great if you could add a photo so we can see the infection. If its Canker you need to cut it out before it kills the tree. If its Scab, you can try to get on top of it with a fungicidal spray. Much like Roses, you need to spray the whole tree as soon as it breaks bud, and again after flowering...monthly is best. I have been doing this for the past two years to try to get scab under control on a couple of my old apple trees. But to be honest, some trees are very susceptible to scab and sometimes it pays to remove the tree and find one that is resistant to replace it with. HOpe this helps, but a photo would really be great as there are many other possibilities!

Fungal infection also covers rusts, so we do need to see the evidence of fungal infection on both the apple and pear tree - if its on the leaves, just post a pic of the leaves of each, if its on the branches, then make sure they show in the pics too.