Tag Archives: Maple

Bacterial Wetwood

What is bacterial wetwood?  Bacterial wetwood, also known as “slime flux”, is a visually frightening-looking, but typically non-lethal, disorder of many types of deciduous trees.  This disorder can reduce the aesthetic appeal of landscape trees, and more seriously, can substantially reduce the value of forest trees used for lumber.  Bacterial wetwood most commonly affects elm and poplar, but can also be a serious problem on aspen, maple, and mulberry.

Bacterial wetwood leads to discolored, rancid-smelling areas on tree trunks.
Bacterial wetwood leads to discolored, rancid-smelling areas on tree trunks.

What does bacterial wetwood look like?  Trees suffering from bacterial wetwood have areas where liquid oozes from their trunks.  This ooze may flow freely at certain times of the growing season, but then may stop flowing at others.  The ooze leads to streaked, discolored, water-soaked areas on tree trunks.  The ooze is often colonized by bacteria, as well as yeasts and other fungi.  These organisms can give the ooze a slimy, sometimes brightly-colored (i.e., pink or orange) appearance as well as a highly disagreeable, rancid smell.  Internally, bacterial wetwood can be associated with localized areas of wood decay.

Where does bacterial wetwood come from?  Bacterial wetwood arises when localized wet areas develop in the heartwood or sapwood of tree trunks.  These areas are colonized by a diverse assortment of bacteria (e.g., Enterobacterium, Klebsiella, Pseudomonas and many others) that can enter trees through root, branch or trunk wounds.  As these bacteria feed and grow, often under anaerobic conditions (i.e., conditions without oxygen), they can produce gases such as methane, carbon dioxide, or nitrogen gas.  These gases build up pressure, causing movement of interior liquids to the exterior of the trunk where they escape through wounds and cracks.

How do I save a tree with bacterial wetwood?  Bacterial wetwood is a chronic disorder and affected trees cannot be cured.  To limit the unsightly staining of bark caused by bacterial wetwood, try to identify where the ooze is exiting from the trunk and insert a long, plastic tube at this location to direct the ooze away from the trunk and to the ground at the base of the tree.  There has been speculation that the build-up of gases due to bacterial wetwood might cause a tree to explode.  However, there have been no reliable reports of this ever happening.

How do I avoid problems with bacterial wetwood in the future?  There is little you can do to prevent problems with bacterial wetwood.  Many affected trees were likely invaded by wetwood-associated bacteria in the seedling stage.  Developing a healthy tolerance for bacterial wetwood, when it occurs, is perhaps the best method for coping with this disorder.

For more information on bacterial wetwood:  Contact your county Extension agent.

Anthracnose

Anthracnose is very common on many types of trees and shrubs. It often occurs on the leaves of ash (left) and maple (right) trees, causing blotchy-brown, dead areas.
Anthracnose is very common on many types of trees and shrubs. It often occurs on the leaves of ash (left) and maple (right) trees, causing blotchy-brown, dead areas.

What is anthracnose?  Anthracnose is the name of several common fungal diseases that affect the foliage of woody ornamentals in Wisconsin.  Trees that are most commonly and severely affected by anthracnose include ash, maple, white oak, sycamore, and walnut.  Anthracnose typically affects young leaf tissue.

What does anthracnose look like?  Symptoms of anthracnose vary from host to host, but in general include irregular spots, and dead areas on leaves that often follow the veins of the leaves.  Affected tissue can vary in color but is often tan or brown.  Severely affected leaves often curl and may fall off.  In some tree species, such as sycamore, twigs can also become infected leading to twig dieback.

Where does anthracnose come from?  Anthracnose is caused by several fungi (many historically classified in the genus Gloeosporium) that survive in leaf litter.  These fungi are host specific.  The anthracnose fungus that infects one type of tree (e.g., ash) is not the same one that infects another type of tree (e.g., maple).  However, when anthracnose occurs on one tree, then weather conditions (typically cool and moist conditions) are favorable for development of the disease on many types of trees.

Anthracnose can be severe on some hosts. On white oak (left), it can cause extensive leaf browning and curling. On sycamore (right), anthracnose can cause twig dieback.
Anthracnose can be severe on some hosts. On white oak (left), it can cause extensive leaf browning and curling. On sycamore (right), anthracnose can cause twig dieback.

Anthracnose can be severe on some hosts. On white oak (left), it can cause extensive leaf browning and curling. On sycamore (right), anthracnose can cause twig dieback.

How do I save a tree with anthracnose?  DO NOT panic.  For many trees, anthracnose is a cosmetic disease.  It may make a tree look a little ragged but will not kill the tree.  However, if a tree has been defoliated by anthracnose for several years, or it is a tree, such as a sycamore, where twig infections can occur, then you may want to use a fungicide for disease control.  Three treatments are typically needed for adequate control: one at bud break, one when leaves are half expanded, and one when leaves are fully expanded.  Fungicides containing copper, chlorothalonil, or mancozeb are registered for anthracnose control in Wisconsin.  DO NOT use the same active ingredient for all treatments.  Instead, alternate the use of at least two active ingredients to help minimize problems with fungicide-resistant strains of anthracnose fungi.  Be sure to read and follow all label instructions of the fungicide(s) that you select to ensure that you use the fungicide(s) in the safest and most effective manner possible.

How do I avoid problems with anthracnose in the future?  You can reduce the number of spores that cause anthracnose infections by removing and disposing of fallen, infected leaves in the autumn.  Leaves can be burned (where allowed), buried or composted.  When composting, make sure that your compost pile reaches high temperature (approximately 140°F).  Also, make sure that your compost pile is routinely turned so that leaves on the outside of the pile eventually end up in the center of the pile.  The combination of high temperature and decay of leaf tissue in a compost pile helps eliminate anthracnose fungi.  Also, maintain good tree vigor by watering and fertilizing trees appropriately.  Check with your local county Extension agent for details on how to properly care for trees.

For more information on anthracnose:  Contact your county Extension agent.