Common diseases that infect maple trees include maple wilt, anthracnose, tar spot, sapstreak and phyllosticta. Maples, like all hardwood trees, are also prone to armillaria root rot. These diseases range in severity from relatively harmless and preventable to fatal and incurable.
Two species of verticillium fungi cause maple wilt. These are the same types of verticillium that cause wilting diseases in flowers, fruits and vegetables. Maple wilt causes the tree's leaves to change color and wilt. A young, healthy maple tree can fight off a minor verticillium infection, but these fungi often kill older trees and those with severe infections.
Anthracnose, tar spot and phyllosticta are all minor fungal diseases. These conditions are common after wet, mild winters when the fungus has a greater chance of growing and releasing spores. Each condition causes only minor discoloration in leaves, and all but the weakest maples have no trouble fighting off these fungi.
Sapstreak is a dangerous, fatal fungal disease that attacks maple trees. Unfortunately, sapstreak gives very little evidence of its presence until the tree is near death. Sapstreak also discolors wood, making the timber worthless.
Armillaria root rot is also called honey fungus, due to the honey-brown mushrooms that spring up around an infected tree's trunk. Like sapstreak, armillaria gives very little indication of its presence except for the mushrooms. By the time the mushrooms appear, the tree is usually beyond help.