David Clement, Extension Specialist and Plant Pathologist, explains two common concerns homeowners have with their pine trees in the fall season: browning foliage and “what are these growths?” (hint: they’re just pine cones).
Trees
Ambrosia Beetles Are Behind Those Tubes
Q: These things like spaghetti pasta were sticking out of our tree that suddenly died. They crumbled when I touched them. Did they attack the tree and kill it?
A: These are sawdust tubes pushed out by ambrosia beetles as they bore into your tree. The tubes are rarely seen this time of year. However, because of abnormal rainfall, some trees are producing ethyl alcohol, a reaction to stress. Alcohol production signals ambrosia beetles to attack. The beetles introduce a fungus into the tree, which clogs up its xylem (the water and nutrient transport system). Since your tree is already dead, it’s hard to say exactly what killed it. Its roots may have rotted or drowned from standing water or saturated, poorly draining soil. The ambrosia beetles may have merely pushed it over the edge. The beetles are not necessarily a death sentence. When numbers are low and a tree is fairly healthy, a tree can recover.
Learn more about ambrosia beetles from Ohio State University.
By Ellen Nibali, Horticulturist, University of Maryland Extension Home & Garden Information Center. Ellen writes the Garden Q&A for The Baltimore Sun.
Have a plant or pest question? University of Maryland Extension’s experts have answers! Send your questions and photos to Ask an Expert.
Pine Trees: Browning Foliage and Pine Cones – Featured Video
Moving into the fall season, you may see some of your pine trees turning partially brown. This is generally a natural occurrence.
Learn more about pines and other trees in the fall/winter season at our FAQ page.
Why is My Tree (Or Shrub or Flower) Dying? Abiotic Problems Could be the Cause
Professionals in the landscape and greenhouse industry, trained horticulturists, and Master Gardeners often use the term “abiotic disorder” when diagnosing a plant problem. To the layman, this can be very confusing. To add to the confusion, signs and symptoms you see on your plants can look very similar to the damage caused by insects and diseases.
Surprisingly enough, the vast majority of plant problems are not caused by insect pests or diseases. Typically, the first thought that comes to mind when a plant is looking “ill” is that some insect or fungus has attacked it without much thought that it could be something else.
Japanese Maples in Maryland Landscapes: Plant Location & Care Are Keys to Success
The group of small ornamental shade trees lumped under the name Japanese maples, Acer palmatum and A. japonicum, and their many hybrids, are very popular with gardeners and plant enthusiasts. Most of the questions we receive about problems with Japanese maples are horticulturally related to poor growing conditions and maintenance rather than insects or diseases. The causes of these problems are usually root or trunk-related issues. So, let’s start with a look at the planting conditions Japanese maples need in order to thrive. Continue reading
Q&A: Why didn’t Japanese maples lose their leaves last fall?
Q: Most of my Japanese maples are still full of dead leaves. They never exfoliated in the fall to leave bare branches. Will this affect new growth in the spring? Should I just let them be?
A: We have received several questions about Japanese maples that are still holding on to brown leaves that didn’t drop last fall. Some crapemyrtles also have held their leaves during the winter. This issue has been reported in several areas of Maryland, which suggests it is due to an environmental factor. An unusually warm autumn followed by a quick cold snap likely interfered with the trees’ normal winter preparation processes.
As the days shorten in the fall, trees go through a series of biochemical and physical changes to prepare for winter survival. In deciduous trees, this includes the development of an abscission zone of cells where the branches connect to the base of leaf stems (petioles). A layer of cells essentially seals off the branches to protect them from water loss, and then the leaves are shed from the tree. We suspect the fall cold snap interrupted this process and normal leaf abscission did not occur in some trees.
Some types of trees naturally do tend to retain dead leaves during the winter. American beeches and many oaks exhibit this trait, called leaf marcescence. This occurs most often on juvenile trees. It may be a strategy to protect buds from winter damage or to discourage deer browsing. Trees may also wait until spring to shed their leaves, thus providing a fresh source of nutrient-rich organic matter to the root zone where soils are otherwise poor. The exact reasons for leaf marcesence haven’t been determined completely.
There is nothing you need to do for your Japanese maple at this time. If your tree was otherwise healthy, new growth will emerge in the spring and the old brown leaves will drop off eventually.
Sources and Additional Resources
By Christa Carignan, Coordinator, Digital Horticulture Education, Home & Garden Information Center
Have a plant or pest question? University of Maryland Extension’s experts have answers! Send your questions and photos to Ask Extension.
Featured Video: Mushrooms and Trees’ Symbiotic Relationship
David Clement, Ph.D. Extension Specialist, Plant Pathology, explains how fungi grow and feed on tree roots under the ground and sprout above ground as mushrooms.
Visit the Home & Garden Information Center website to learn more about Wood Rots and Decay of Trees and Shrubs.