Hi- this is called gummosis. It's a defense mechanism by which the tree pushes out

sticky resinous gums to expel insect pests and diseases and respond to

environmental stress. Specific causes include canker diseases, peachtree borer and plum curculio, excess soil water, heavy pruning, and extreme weather.

We can't determine the exact cause from the photos. It could be a combination of factors. Look closely at the globs of sap closest to the trunk for signs of frass (sawdust in the sap from peachtree borers feeding under the bark).

Because there is so much sap it could be a canker disease. In that case, you will see dead, oval-shaped areas that extend into the bark and you'll begin to see dieback of branches. If the tree looks healthy through the growing season, the cause of the gummosis was probably due to environmental factors.

You should remove the vegetation around the base of the tree and lay down 2-3 inches of mulch. This will help keep string trimmers and lawnmowers from injuring the trunk.

Lichens are not harmful to the tree: https://extension.umd.edu/hgic/topics/lichens

These web pages will give you more information:
https://extension.umd.edu/hgic/topics/diseases-stone-fruit (see Leucostoma canker)
https://extension.umd.edu/hgic/topics/stone-fruit-insects (see peach tree borer)

https://blogs.ifas.ufl.edu/lakeco/2018/07/06/peach-gummosis/#:~:text=Do%20your%20peach%20trees%20have,trunk%20can%20cause%20this%20symptom.

https://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/pests-and-problems/diseases/cankers/gummosis-of-fruit-trees.aspx

Jon