Ooze from Aspen trunk

Asked July 21, 2016, 2:10 PM EDT

Hello. I have an Aspen with 3 locations that have orange ooze coming from them. Please let me know what type of issue this may be. Thank you! Steve Wisecup

Boulder County Colorado trees and shrubs

1 Response

Hello- Thank you for your question and the attached photo of your aspen trunk. We believe this orange-staining ooze to be caused by one of two things: 1) poplar borer (Saperda calcarata) or 2) Cytospora canker (Valsa sordida) which is a fungus. Without seeing the issue in person, diagnosis is an educated guess based off your description and the photo. Cytospora is the most common canker-causing fungus and plagues ornamental aspen. It leaves orange-stained areas of bleeding bark, small orange tendrils of a jellylike material on the bark, and large patches of dead bark. You could look for symptoms of the orange gelatinous spore tendrils or "horns". Prevention is better than control; avoid wounding, carving or scraping bark; perhaps a fungicidal tree spray may work; sterilize pruning shears in between prunings to prevent fungi travel. Small trunk cankers can sometimes be cleaned up by removing affected tissue down to sound, un-stained wood. Seek help from a professional arborist if unsure how to perform this "surgery". Do not attempt to remove large trunk cankers. If a small canker is found on a branch, prune that branch off, remembering to sterilize your shears afterward to prevent the spread of the fungus. Now, if the problem you have is caused by the poplar borer, you may see moist areas on the bark, often with associated sawdust. Stringy sawdust is pushed out of holes in the bark by the developing larvae and may pile around the base of trees. Look for this as a symptom to help diagnose the problem. Chronically infested trees exhibit a black varnish-like stain on the bark below points of borer attack. The poplar borer is the most destructive insect to aspen in many areas of the state, including native and oranamental stands. Attacks are generally restricted to large-diameter, over-mature trees. Trees most affected are in direct sunlight and generally suffering from some growing stresses such as drought. If the problem your trees have is caused by the poplar borer, there are several things you can do for management. Several biological controls including parasites of eggs and larvae, predators, and fungal diseases have been reported to affect this insect. Siting aspen so it is shaded, receives adequate water and grows optimally will reduce risk of attack. The poplar borer is difficult to control because of its three-year life cycle. Standard borer treatments of insecticides applied to the trunk should provide coverage throughout the period of adult activity (July - August). Application should be most throrough to existing areas of attack, in the middle of the tree, where egg laying is concentrated. Injections of insect parasitic nematodes into active borer tunnels have given partial control of larvae. Perhaps the best thing you can do at this stage is call a professional arborist to come out to diagnose the problem in person and further provide management solutions. Best wishes.