Several reports have recently come in of bright orange slime on trees or on mulch in Brown, Door and Shawano counties. Slime molds and yeasts can make bright colors, usually pink, orange, or yellow. Don’t panic – they don’t harm the tree. Often the orange, slimy areas on trees are associated with sapsucker wounds, where the tree has been bleeding sap on which microorganisms are growing. We see these most during the spring when the weather is moist, but once the weather warms the slime will dry up, leaving just a faint orange tinge to the tree where they were.

Sapsuckers wound trees and return to lick the sap that oozes from the wounds.

Slime molds and yeasts can be orange, pink, or yellow. Photo by: Gerald Vomastic

Written by: Linda Williams, forest health specialist, Green Bay, (Linda.Williams@wisconsin.gov), 920-662-5172.