Deciduous Plant Health

As our region transitions into fall, the most noticeable change is the decreasing number of daylight hours. Plants start responding to this change long before we notice it because they are highly cued into light levels because of…you guessed it…photosynthesis. Deciduous plants, like trees and shrubs, are gearing up metabolically for winter dormancy. This fact, coupled with hot weather and fewer instances of rainfall, may mean that, this time of year, deciduous trees and shrubs in our landscapes may already be looking worse for wear. This is normal.

If, however, deciduous trees and shrubs become stressed during the growing season, other symptoms and signs may be evident in late summer and early fall that may point to potentially larger issues. One problematic sign is the presence of bracket or shelf mushrooms growing out of the trunk or branches of the tree. Any mushroom, including bracket or shelf mushrooms, is simply the spore-producing body of a fungus. The vegetative part of the fungus, called the mycelium, is under the bark digesting cellulose and lignin, the main chemical components of woody plant bodies. Most bracket fungi are wood rotters, but will typically not infect a healthy, living tree unless it is already stressed due to reasons such as a lightning strike, heat and drought, or insect infestation. Improper pruning such as lopping branches off at midway, or scraping the trunk with lawn equipment also stress trees and will provide efficient portals of entry for fungal spores. Once fungi have become established internally in trees and shrubs, they are difficult, if not impossible, to treat or manage. It is impossible to know the extent of mycelium growth internally. But, if bracket or shelf mushrooms are observed, then the fungus as has reached a physiological state that supports the formation of reproductive structures. Any tree or shrub with bracket or shelf mushrooms growing out of it is in a period of decline and should be removed.

Another sign of a potential problem is slime flux or bacterial wet wood. Typically, the bark has been compromised by either insects, lawn equipment, or some other agent, and bacteria colonize these areas and infect that tree’s vascular tissue which lies just under the bark. Bacteria ferment the sugary sap and it will ooze out of the tree and run down the trunk. The foamy appearance of the fermented sap often startles property owners. Fermented sap also attracts a plethora of insects ranging from fruit flies to yellow jackets. Slime flux, in and of itself, isn’t generally lethal to mature, well-established trees. However, if bark tissues continually stay wet, decay will set in further compromising the outermost bark tissues and set up portals of entry for fungal spores. The fermented sap itself may also be infected by microbial pathogens.

Long term good health of trees in the landscape depends on several factors like making sure the bark tissues are not compromised. A 3 to 4-inch layer of mulch that extends out to dripline will prevent mowers and other lawn equipment from damaging the tree trunk. Giving the root systems plenty of room to grow and expand will keep trees from becoming stressed for nutrients and water. Also, checking trees for boring insects should done regularly.

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Photos by Kerry Heafner, LSU AgCenter

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Photos by Kerry Heafner, LSU AgCenter

10/22/2021 7:01:13 PM
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