Under the bark of your trees, insects could be feeding on the wood while you have no idea it’s happening. These wood-boring insects can kill trees rapidly, especially if you fail to notice the common signs of activity before it’s too late. Learn how to spot the symptoms of a borer infestation in your New Jersey trees and what to do when you think you have a problem.
Key Takeaways:
- Wood-boring insects attack the inner wood of trees, causing extensive damage that trees cannot recover from and potentially girdling the tree by preventing water and nutrient transport.
- Three primary wood borers in Northern New Jersey are bronze birch borers (attacking birch trees), ambrosia beetles (targeting multiple species, including dogwoods and maples), and southern pine beetles (damaging pines).
- Each type of wood borer has distinctive symptoms, including D-shaped emergence holes for bronze birch borers, sawdust and entrance holes for ambrosia beetles, and pitch tubes during early southern pine beetle attacks.
- Keeping trees healthy and stress-free through proper watering, fertilization, and mulching can reduce their vulnerability to wood borer attacks, and preventive insecticide treatments can provide additional protection.
- Early detection of wood borer symptoms and prompt treatment by a Certified Arborist is critical, as trees cannot recover from extensive borer damage and may require removal if the infestation is severe.
The Danger of Wood-Boring Insects
Of all the insects that attack trees in Northern New Jersey, few are as deadly to your trees as wood borers. Many pests spend their time feeding on the leaves of trees. While this causes stress, it likely won’t kill them, as deciduous trees can regrow their leaves with enough time.
Borers, on the other hand, attack the inner wood of trees. They cause extensive damage that the tree cannot recover from. Eventually, the borers will damage enough of the inner wood to girdle the tree, preventing it from transporting water and nutrients throughout.
Knowing what insects are most common in Northern New Jersey and what symptoms they produce will allow you to catch these problems early to potentially save your tree.
General Tips to Protect Your Trees from Borers
One of the best things you can do for your trees is to keep them free of stress, as unstressed trees are better able to fight off infestations. Some simple tips for reducing stress include:
- Fertilizing trees when soil testing reveals a deficiency
- Watering trees during a drought
- Placing mulch around trees to reduce the effects of summer heat stress
Additionally, having an arborist treat your trees with preventive insecticides can prevent wood-boring insects from establishing in your trees.
Common Northern New Jersey Tree Borers and Their Symptoms
There are three primary wood borers to keep an eye out for in Northern New Jersey that can quickly harm your trees.
Bronze Birch Borers (Agrilus anxious)
Bronze birch borers (BBB) are native insects that attack birch trees. The pests overwinter inside the tree as larvae and emerge in the spring as adults. Adults are very tiny, with most measuring around ⅜ inches long.
Adults emerge at anywhere between 440 and 800 growing degree days (GDD). This typically corresponds to late May until early June in our area.
PRO TIP: Growing degree days are a more accurate way to determine when insects emerge. The measurement accounts for the amount of hot weather we see in a given year to decide when to look for insects. To find out how many GDD’s we’ve experienced and to look at historical data, use this online GDD calculator.
The adults do not damage the tree; instead, they lay eggs on the bark that produce larvae that eat the inner wood. When attacking a vulnerable birch species, BBB can kill it within a few years. Research from Rutgers has found that many native birches have some resistance to BBB. River birch is the most resistant, while other native species like paper birch or yellow birch have demonstrated some resistance. Non-native species like Asian and European birches have no resistance, and we recommend not planting them.
Symptoms of Bronze Birch Borer
- Wilting leaves
- Dead patches in the upper canopy
- Ridges and bumps on limbs and branches
- “D”-shaped emergence holes in the bark
- Rusty brown stain on the trunk
Ambrosia Beetles (Xylosandrus germanus and Xylosandrus crassiusculus)
Ambrosia beetles cover 30 different invasive species. We are focusing on the black stem borer and granulate borer, as they are the two most damaging to our New Jersey landscapes and forests.
Ambrosia beetles attack a wide variety of tree species in Northern New Jersey, though some common species that are most likely to deal with them include:
- Dogwoods
- Honey locusts
- Magnolias
- Maples
- Redbuds
Ambrosia beetles typically begin attacking trees in April. Adult beetles bore into small trunks or branches, creating tunnels where they lay eggs and introduce a fungus. The larvae then feed on the fungus as they develop into new adults.
Young trees are especially vulnerable – an ambrosia beetle infestation can kill them. Older trees are more likely to survive but may lose branches and become stressed, making them more susceptible to other issues.
If you have several trees close together or have previously dealt with ambrosia beetles, you may want to invest in traps. Many nurseries choose to use ambrosia beetle traps to protect their stock, and they have provided promising results.
Symptoms of Ambrosia Beetles
- Entrance or exit holes on branches or small stems
- Sawdust around the base of a tree
- Sap production from the tree
- Bark cracking
- Wood staining
Southern Pine Beetles (Dendroctonus frontalis)
The southern pine beetle was once a distant concern for us in Northern New Jersey. As the name implies, it used to be a problem in the south and southwest of the country. However, shifting climates have led to the beetle expanding its range, and now, this destructive pine pest is in our area.
Southern pine beetles can attack most pines but prefer some, like Virginia or pitch pines. Adult females will locate a vulnerable tree and release pheromones to attract nearby beetles. They will work to burrow into the tree and colonize it. The female digs S-shaped galleries underneath the bark in the inner wood to lay eggs, while the males follow behind to pack the holes with frass (insect waste).
Symptoms of Southern Pine Beetle
We divide trees dealing with southern pine beetle into three categories with different symptoms:
- Fresh Attacks: These are trees that are seeing the initial wave of attacks. You may notice small pitch tubes in the trunk with beetles working in them and reddish-white sawdust on the ground. The foliage will still be green at this stage.
- Fading Trees: In this stage, the foliage has begun to fade in color as girdling occurs. Under the bark, the females have finished creating galleries for eggs.
- Vacated Trees: The tree will appear dead in this stage, and you likely won’t see any more activity from the southern pine beetle. Other pests, including the ambrosia beetle, may colonize the tree at this time.
What to Do When You Think You Have Wood Borers on Your Property
If you’ve noticed any of these early symptoms, it may not be too late to save a tree. Because trees cannot recover from borer damage, knowing the symptoms and recognizing them early can be the difference between saving a tree and having to remove it.
As soon as you suspect borer presence, call an arborist and have them inspect your tree for insects to help determine what the culprit is.
“If we catch it early enough, we might be able to stop the borers before they cause too much damage. We’ll usually treat the tree with a systemic insecticide to kill anything that’s still active. It won’t fix the damage that’s already done, but it can keep things from getting worse.” – Casey Walentowicz, ISA Certified Arborist & Owner of Aspen Tree
If the damage is too severe, the only option for the tree will be to remove it for the safety of your family and property.
Frequently Asked Questions About Wood Borers in Northern New Jersey
To help you better understand wood-boring insects and the threat they pose to New Jersey trees, we’ve answered some of the common questions we hear from homeowners.
When should I start looking for signs of wood-boring insects?
While the timing of when insects are active will depend on the species, we recommend you begin looking for pests and symptoms in May. Keep an eye out for any symptoms like wilting or discolored foliage throughout the growing season.
Are there any natural predators that can help control borer populations?
Yes, natural predators like predatory wasps or woodpeckers can help control insect populations. While they won’t be able to control populations when they reach infestation levels, these beneficial predators can lower the risk of a pest establishing.
How do wood-boring insects spread from one area to another?
In many instances, wood-boring insects travel thanks to help from humans. Most insects can travel naturally, but humans aid in long-distance spread by moving infested wood or nursery stock into a new area. Many local governments enact quarantine measures when a pest infestation is severe enough.
Don’t Let Wood-Boring Insects Destroy Your Trees – Call Aspen Tree!
Wood-boring insects can do serious damage before you even know they’re there. If you’re seeing warning signs or just suspect something’s off, don’t wait – early action is the best chance to save your tree.
At Aspen Tree, every job is overseen by an ISA Certified Arborist who knows exactly how to diagnose the problem and apply the right treatment (or safely remove the tree if it’s too far gone). We stay current with the latest arboriculture research so we can deliver the most effective solutions possible.
Call us today at 201-939-8733 or request a quote online.
