Tree Care Industry Association founded in 1938, formerly the National Arborist Association, is a US public and professional resource organization on trees and arboriculture.
TreesAreGood.org by International Society of Arboriculture is the tree owner's resource. It provides information on tree benefits and proper care. Home of the arborist directory to verify credentials.
Since it's founding in 1964, the Wisconsin Arborist Association has been dedicated to our mission of "Improving the understanding of trees and the practice of arboriculture".
University of Wisconsin-Madison/Extension's Plant Disease Diagnostics Clinic provides assistance in identification and educational information for plant diseases and their control.
Wisconsin's Insect Diagnostic Lab at the UW Department of Entomology. This is the place to go for positive identification of a tree pest. A great resource for information on Emerald Ash Borer.
The Wisconsin Department of Natural Resources forest health website has information about the distribution, life cycles, impacts, and management of the pests, plants, and diseases that affect our forests.