Liriope’s Muse: Tree Care Tips from a Master Arborist
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Liriope's Muse: The mystery in the BCMA’s front yard
Eric, our BCMA and founder, has two red oak group trees in the front yard of a neighborhood house he just recently moved to. When he moved there, the trees were all still in their dormant window, but as time went on, other similar red oak group trees began leafing out all around town, and even across his neighborhood, yet his had not. So immediately, he knew something was wrong with it.
The yard had shown obvious signs of previous herbicide use when Eric first moved in, but that is to be expected of any neighborhood property, so he wasn’t too alarmed. However immediately upon his moving in, he ordered a biostimulant treatment to be administered across his entire property to help give the plants a little boost into their spring growth and help break down any residual herbicides.
After the biostimulant treatment, his Azelea bushes flowered in abundance, his lawn became the greenest on his street, and the red oak group trees even began to leaf out, except it was abnormal. He noticed that about 1/3 of the trees' canopies were deadwood, the leaves were taking a while to develop, mature, and were not true to form. (Up until this point, with 50+ years of experience in the local oaks, Eric has only been able to classify the trees to be some sort of red oak group tree but hasn’t been able to identify exact species, even after leafing out due to its unusual and distorted growth. We’ve used modern identification algorithmic software that are very accurate and also haven’t been able give a straight identification either.)
When leaves first emerge during spring leaf flush, they are often smaller, thinner, softer, and lighter in color than mature foliage. As the leaves continue to expand and develop chlorophyll, they typically darken in color and become firmer in texture. For most red oak group trees, this transition generally occurs over approximately 2 to 4 weeks after leaf emergence, however the two in Eric's front yard took much longer to fully develop. And this is an ongoing issue with all of the new growth, too.
Noting this symptom, he removed all of the deadwood and hoped for the best. Initially, he had just assumed that this was a hormonal disturbance from residual herbicide remaining in the soil, as previously discovered. So, he continued to monitor them and that’s when he noticed random branches beginning to flag (leaves suddenly die and brown but still remain connected to the branch in an otherwise green canopy), perplexed by the abnormal array of symptoms, he would remove the flagged branches as they came up and continued to monitor the tree. So, he began sharing his concerns with his 3rd generation tree guy, ISA Certified Arborist and son-in-law, Shane Krajnik at their weekly family dinners who was equally as amused and curious by these trees.
These two experienced tree guys would spend about 20 minutes each evening, perplexed by these trees, trying to figure out what could possibly be plaguing these poor trees, while the 4th-generation tree gal ran circles around their feet.
Their most recent visit was something different: while the ladies were preparing dinner, all 3 generations were out at the trees, trying to get to the bottom of what was causing them to slowly die off. Shane was closely observing and tugging on one of the flagged leaves when the twig it was connected to snapped off in his hands. Upon inspection, he found a small gallery hole bored through the center of the twig and inside was a larva of some sort. When he looked at the other end of the branch (still connected to the tree) he noticed another larva and immediately a lightbulb went off for them. They began snapping off the other flagged branches, between the living and dead wood, and found more larvae, eggs, and even fully mature beetles. They then began looking closer at the afflicted branches and those that appeared healthy and were able to identify entrance wounds.
The culprit? The Black Twig Borer, in the family of ambrosia beetles, is one of the few known to attack otherwise healthy trees! More information in next week's blog:
Liriope’s Muse – Arborist Observation: The Black Twig Borer
This was the first case of the Black Twig Borer that Eric has identified in our service area, though it is a type of Ambrosia Beetle which we see very often so it didn’t come to be much of a surprise to him. The borer infestation is not what caused the hormonal issues in the tree, that came from the chronic herbicide use in the yard for most of the tree’s lives.
As noted many times on this platform, trees are not entirely defenseless; they have a natural chemical ability (allelopathic chemicals) to defend themselves against disease and ward off pests. However, when a tree is stressed these defense systems are weakened and they become more susceptible to a secondary issue… such as a fungal pathogen, or in Eric’s case a tree boring pest.
The photos above were captured to show the live and active borer larvae, that the arborists found in galleries
hidden in the twigs.
The photo above to the left shows a borer entrance hole into the twig, and the photo in the middle and to the right have
red arrows pointing to the random flagging in the canopy caused by these borers
The photos above show a live Black Twig borer, Xylosandrus compactus, a type of Ambrosia Beetle.
A caution to all homeowners:
Eric is a highly educated and experienced arboricultural professional, and even he was ‘stumped’ by this case and wanted to use it as an opportunity to educate and raise awareness. If you take one thing from this blog, other than to spend more time with family, it's to keep a close eye on your tree and not ignore flagging! If you notice your tree(s) beginning to flag, take a closer look. Break the twig off (its already dead and wont hurt the tree) and look at the center. Maybe even break it into a few pieces as you may not break it in the right place the first time – a good tip here is to grab on to the twig tip, or flagged leaves, and tug on it, wherever it breaks usually is a sign of its weakest point and might be where a gallery hole can be found. Look closely at the galleries, are there any larvae, eggs, or mature bugs? Closely observe afflicted, and non-afflicted branches for entrance wounds (pictured above), this’ll solidify that your tree has an active borer infestation!
In short, flagging can be caused by a number of factors, such as drought, disease, pest infestations, and more. So, it is not something that should be taken lightly and always requires some formof arborist intervention. So, if you notice flagging or find an active borer infestation in your tree(s) contact your local ISA Certified Arborist promptly!
*this statement is not meant to fear monger but rather spread awareness of the potential severity of the situation*
Liriope’s Muse - Expert Tree Care Tips
