The very old and large white oak became sick last year- then this year the leaves came out and quickly began to fall so now more than half of the leaves have died. Is it anthracnose? What can be done to save the tree? It is large and you can see the top of the house at the bottom of the photo.Thanks
Thank you reaching out to the Toronto Master Gardeners for help with your tree. It is incredibly sad to see such a large mature Oak ailing so badly. Oak trees Quercus are hardy, generally problem free trees. The pests and diseases they are most susceptible to are rarely very damaging to the tree, however in this case your tree seems to be experiencing major die back and this needs to be addressed quickly. Die back can be caused by a number of issues and it is impossible to diagnose the exact cause by viewing a photo. Here is a link which details the condition, it shows photos and diagrams describing various causes and possible remedies.
http://ipm.illinois.edu/diseases/series600/rpd641/
I would go further however and contact a licenced arborist. This link to Landscape Ontario will assist is choosing one in your area. I wish you good luck with this, hopefully you can find a solution for your beautiful tree.