Connie, What you see on your tree is an infestation of Eastern Tent Caterpillars.  If you have only the one 'nest', it can be treated fairly easily. Here is a link to a fact sheet from Penn State University Extension on Eastern Tent Caterpillars: https://extension.psu.edu/eastern-tent-caterpillar.
  After reading this Fact Sheet, if you feel you want to remove the nest and need help, I recommend you contact a local ASA Certified arborist. They know exactly how to handle your problem pests and can advise you on the best way to treat your infestation. 
  One thing I should note is the feeding and defoliation caused by the Tent Caterpillars is more of a cosmetic problem and usually does not threaten the future health of an otherwise healthy tree. Having said that, leaving the problem untreated most likely will result in reinfestations in this tree and possible spread to adjacent trees in following years.
   Thank you for the question and I hope you have a great late summer and fall season.

Thank you so much!