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How Unhealthy Trees Attract Borer Insects!

Here at Giroud Tree and Lawn, we get all sorts of calls to evaluate trees that are infested with insects. Sometimes a homeowner can see insects gathering around the trunk or high up in the branches. But oftentimes, the problem is lurking deep within the bark of the tree. Borer insects of all types are common in the Philadelphia area, and unless you’re working with an ISA Certified Arborst, identification can be tricky! Read on to learn about the different types of borers, why these insects are attracted to unhealthy trees, and what you can do to deter them!

Types of Borers

Borers include a wide variety of beetles, weevils, and moths.  Borers carve out tunnels in trees to lay their eggs and feed.  By tunneling between the bark and cambium layers, Borers restrict the flow of food and water through the tree. 

Pitch Mass Borers

Pitch Moths are common to our area, and they inject their larvae into Pine, Spruce and sometimes Fir trees. The larvae feed beneath the bark, causing the tree to ooze clumps of “pitch”, a sticky, sappy substance. Unfortunately, the pitch creates a protective covering for the larvae, making it difficult to reach with insecticides. In order to eradicate Pitch Mass Borers from a tree, a trained tree care specialist will have to scrape the pitch clump off of the tree and manually kill the larvae by poking it with a sharp instrument! Check out this video showing the process:

Pitch Mass Borer larvae need to be removed manually because the sappy, clumps of pitch cover the insect and prevent insecticide sprays from reaching them. A Giroud tree care expert will scrape the pitch masses from the tree trunk to find the larvae underneath.

Emerald Ash Borer (EAB)

One borer insect that certainly gets a lot of attention these days is the Emerald Ash Borer. These beautiful, shiny green beetles invaded North America around 2002 and they are believed to have migrated over on shipping materials from Asia. Unfortunately, there are very few natural predators here to control the EAB population, so they have decimated Ash Trees in the USA and Canada.

According to Penn State’s Department of Entomology, Emerald Ash Borer have killed over 40 million trees in the United States. Without treatment, Ash Trees with Emerald Ash Borer die within 1-3 years. By the time you see a visible decline, Emerald Ash Borer has already done significant internal damage to the tree. That’s why it’s critical to treat now before the damage is beyond repair. Check out this post, What We Know Now About Emerald Ash Borer, for more information.

Other Borers

Although Pitch Mass Borers and Emerald Ash Borers are the two types of greatest concern in our area, there are plenty of others who are causing big problems for local trees. Among them are the Bronze Birch Borer, which attack Birch Trees, the Ambrosia Beetle, which are drawn to all sorts of conifers, and the Bark Beetle, which are known kill White Pines. The only way to know for sure if your trees are infested with borer insects is to schedule a free evaluation with a Girould ISA Certified Arborist.

How to Know if Your Tree has Borers

Borers leave a telltale trail of sawdust and tiny holes as they drill through a tree’s roots, trunk, and branches.  The bark on the tree may also be discolored from sap drippings.  It is impossible to measure the amount of internal damage Borers have inflicted on a tree since their tunnels are underneath the bark. 

Borer holes can be random or in a line around the tree, depending on the type of insect.

Borer Treatment & Prevention

For treatment to be successful, borer problems must be caught early.  The best treatment available is injecting infested trees with a pesticide that can kill actively feeding Borers inside the tree as well as larvae attempting to enter the tree.  While there are no guarantees, if the tree is able to absorb the chemical, it will usually survive and respond. However, the Pitch Mass Borer needs to be removed manually because the pitch mass can block the insecticide from reaching the insect.

The good news is that the best line of defense against Borers is to keep your trees healthy!

“Believe it or not,” explains Giroud Vice President and ISA Certified Arborist, Drew Slousky, “an unhealthy tree will actually emit a scent, like a pheromone, that attracts insects. The best way to prevent a borer attack is to make sure your tree is healthy!”

There are many steps you can take to make your trees stronger, and it all begins with an evaluation by a Giroud ISA Certified Arborist. During your FREE inspection, your arborist may recommend:

  • Annual Deep Root Feedings to keep your trees fertilized
  • Pruning out hazardous and nutrient-zapping deadwood 
  • Protecting roots from injury by mowers and other equipment.

Call 215-682-7704 today for a FREE property inspection!

Author: Jeanne Hafner

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