• George R. Lee

What's Wrong with My Maple Tree?


Maple Trees (Acer) are among the most common and regularly planted trees in many regions of the United States. Maple trees come in all sizes, shapes, and colors. Although tolerable of heavy clay soils, maples grow best in loam soils with good drainage. These trees are used in a variety of settings and for particular purposes. You'll find dwarf ornamental maples used to accent a garden or landscape bed. You can also find maples with heights of 60-100 ft sprawling in a yard, used as a centerpiece for the property, screening, a noise buffer, or for shade.


Maple trees also have their share of illnesses which if left uncared for can lead to their ultimate decline. Fertilizing with the correct source of nutrients is often overlooked. Diseases such as verticillium wilt can devastate any maple. Common insects such as scale insects can harm maple trees too. There are numerous threats to these trees and especially those growing out of their natural habitat in the forest but rather living within your normal landscape setting lending to a more stressful environment.


One pest threat which is lethal to most shade tree species of maples is the "Ambrosia Beetle". This oftentimes overlooked or misdiagnosed insect is a deadly, invasive and native threat to the health and safety of maples.


The Ambrosia Beetle is closely related to bark beetles but is actually more associated with the weevil family of insects (curculionidae). Ambrosia beetles and their larvae do not feed on the wood per say, but rather on ambrosial mold (it's like a fungus). The females introduce the fungus into the tunnels as they bore into the sap and sometimes heartwood of trees, shrubs, and logs. Once the fungus is laid the larvae begin to feed on the fungus. Upon completing their development, the males mate and their life cycle begins again.


There are 2 families of Ambrosia beetles, the invasive family and the native family. These 2 beetle families are also known as "The Black Stem Borer" and the other is the "European Shot Hole Borer". These beetles girdle branches as well as invade tree trunks. Branches and trees are not killed by insect chewing but rather by the ambrosia fungus clogging up the vascular tissue (something similar to cholesterol causing blood clots in a person). Weakened, low vigor trees appear to be more susceptible to infestations from Ambrosia Beetles but evidence shows these borers will infest healthy trees as well.



Ambrosia beetle damage
Ambrosia beetle channels

Signs and symptoms of Ambrosia beetle infestation may include upper limb/tip dieback, discoloration of the leaves, oozing spots along the trunk and main branches and tiny holes that look very similar to those found in a BB Gun. You can also look for frass tubes which looks like a toothpick sticking out of the tree or leaking sawdust. A stressed tree can die quickly during hot dry weather as water cannot reach the branches and leaves in the crown.


Some will ask, "do Ambrosia (shot hole borer) beetles attack other types of trees?" The answer is YES! This deadly pest can be found in over 200 different plant species. At Branch Tree Service we're seeing increased ambrosia symptoms in various types of maple trees but also in the hickory tree family, walnut, sweetgum, tulip, poplar, magnolia, and the oak tree family.


How can you get rid of Ambrosia Beetles?


It is possible to apply timely trunk penetration applications which may offer some managed level of suppression. The latest supported research shows that micro invasive injections of systemic insecticide has better, longer lasting results and control of these beetles. Be aware that there are no known treatments available as of August 2021 which provide total control and eradication of Ambrosia Beetle.


Other Ways To Help


If your tree appears to be more than 40 percent defoliated, (first confirming your tree's problem is ambrosia beetle) you may want to remove the tree to reduce beetle population and spread.


If less than 40 percent of the tree is defoliated, maintain good soil fertility. Trees in the landscape may require more nutrient supplements than one might think.

  • Mulch around trees

  • Long soaks of water around the branch line (when the weather is dry) of the tree will help reduce unwanted stress to the trees vascular system.

  • Prune out dead and infected limbs

  • Remove infected wood (such as fire wood) from the site

  • De-bark nearby logs


As the author of this article I have first hand experience dealing with Ambroisa Beetle infestation in my trees. Upon purchasing my home in 2019 I found that of my 26 large mature trees, 11 of the trees were infested with Ambrosia Beetle. While investigating further as to how I could best tackle my beetle problem I found most resources stating this is usually a minor concern and simply keep my trees watered and fertilized. Although I appreciate the comments of others, I have found their research information outdated as I continue to battle this Ambrosia Beetle infestation in my own landscape.


Here's what my "hands on" experience has found


  • These beetles attack perfectly healthy trees, (not all but some and I still don't know why one over the other).

  • This beetle is deadly, (which is not what many articles state) as seemingly within months of identifying this beetle it killed one of my bitter-nut (hickory) trees. The tree appeared normal and healthy upon my first inspection and within months the top was dead. No treatment had been made as of that time yet as I was too late to perform any impactive sort of service.

  • The beetle fungus (because of the females laying eggs) moves much faster than what I was told.

  • I have been trunk injecting, spraying, fertilizing, and pruning. Due to the care I've given over the last 3 years, I have been able to manage and save 23 of my 26 targeted trees.


Don't know what's wrong with you maple tree or even other species of trees in your landscape? Don't wait, contact an arborist today. Your tree might be in decline from Ambrosia Beetle or one of the many other harmful pest known to negatively impact the health, beauty and life of your tree.


Feel free to call or contact our office to set up your visit today.