Bark beetles can cause significant damage to trees and shrubs, often leading to the decline of overall tree health. Effective management of these pests can help maintain the integrity of your yard and the surrounding ecosystem.
One of the primary methods of controlling bark beetles is through prevention. This involves maintaining tree health by keeping them hydrated, mulched, and pruned.
Healthy trees are less prone to bark beetle infestation, as they can naturally fend off these pests.
There are several bark beetle control methods with varying degrees of effectiveness. Some of the most common approaches include chemical treatments, removing infested trees, and using pheromone traps.
Understanding Bark Beetles
Species of Bark Beetles
There are hundreds of species of bark beetles that infest various trees. Some common examples include:
- Mountain pine beetle
- Spruce beetle
- Ips beetle
- Red turpentine beetle
Each species typically attacks a specific type of tree, making it crucial to identify the infestation correctly for effective control measures.
Life Cycle
Bark beetles undergo a complete metamorphosis, consisting of egg, larva, pupa, and adult stages. The overwintering process can occur as late-stage larvae or adults, depending on the species.
When temperatures rise, they become active, mate, and lay eggs within galleries beneath the bark. Larvae feed on the tree’s cambium layer and eventually pupate, emerging as adults to restart the cycle.
Bark Beetle Identification
An effective way to identify bark beetles is by examining the galleries they create beneath the bark.
These winding tunnels are chewed by both adult and larval beetles. Additionally, look for signs such as:
- Boring dust or frass in bark crevices
- Discolored foliage
- Small exit holes on the bark
Causes and Impacts of Bark Beetle Infestations
Host Trees and Their Damage
Bark beetles are known to attack various tree species, causing significant damage to their branches and roots.
- Trees: Pine, spruce, and fir trees are common targets of bark beetles.
- Damage: Infestations result in the destruction of the inner bark, causing the tree to lose its ability to transport nutrients and eventually leading to tree death.
An example of a tree impacted by bark beetles is the loblolly pine, which is often attacked by the southern pine beetle source.
Drought Conditions and Infestations
Drought conditions play a vital role in bark beetle infestations, primarily because moisture-stressed trees become more susceptible to attacks.
- Moisture: Healthy trees can fend off beetles through increased resin production.
- Drought: Trees weakened by drought are more vulnerable, and a beetle outbreak can quickly spread, overwhelming their defenses.
Environmental Factors
Both natural and human-made factors contribute to bark beetle populations and their impact on tree health.
- Natural: Climate changes and weather patterns can influence bark beetle reproduction and the likelihood of a large-scale outbreak.
- Human: Firewood transportation and improper disposal of infested trees can inadvertently spread bark beetles to new areas.
| Factors | Pros | Cons |
|---|---|---|
| Natural | Necessary for bark beetle life cycles | Can lead to severe infestations |
| Human | Supports firewood industry | Unintentional spread of bark beetles |
Leaves are generally not the primary target of bark beetles. Rather, they focus on the inner bark, as it provides the necessary nutrients for their survival.
However, massive infestations can eventually lead to the collapse of entire tree canopies.
How to Get Rid of Bark Beetles: Preventing and Managing Infestations
Bark beetle infestations have caused significant damage in pine forests in the United States and Canada, affecting landscapes and killing trees.
This section will provide methods for preventing and managing these infestations.
Pruning and Thinning
- Regularly prune and thin your trees to maintain good air circulation and prevent overcrowding.
- Remove and discard infested branches prior to beetle emergence to halt their spread.
For example, properly pruning your pine trees can reduce the likelihood of attracting pine bark beetles, an aggressive species known to cause extensive damage.
Proper Moisture Control
- Maintain a healthy landscape by providing adequate moisture to your trees and shrubs.
- Avoid using excessive amounts of mulch; this can create a damp environment attractive to adult beetles and facilitate infestations.
Proper moisture control helps promote healthier trees, making them less susceptible to bark beetle infestations.
Chemical Treatments and Pest Control
- Apply insecticides (carbamates, pyrethroids) to the bark and branches to prevent damage in areas of active infestation.
- Consider hiring a pest management professional to ensure the proper application of chemicals.
A comparison of insecticides:
| Insecticide | Pros | Cons |
|---|---|---|
| Carbamates | Effective in controlling various beetle species | Toxic to some beneficial insects |
| Pyrethroids | Fast-acting and less toxic | Break down more quickly, requiring repeated applications |
Natural Predators
- Encourage the presence of natural predators such as birds, ladybugs, and parasitic wasps to help control bark beetle populations.
- Introduce natural repellents, like peppermint oil, as an alternative to chemical treatments.
By promoting a healthy ecosystem that includes natural predators, you can help minimize the impact of bark beetle infestations.
Bark Beetles in the United States and Canada
Regional Bark Beetle Species
In the United States and Canada, some common species of bark beetles include the pine bark beetle and the mountain pine beetle.
These beetles primarily infest pine trees and can cause severe damage.
- Pine Bark Beetles: Commonly found in red pine forests older than 50 years in the US, particularly in Minnesota.
- Mountain Pine Beetles: Affecting millions of acres in the western US and parts of Canada.
Specific Threats and Treatments
Bark beetle infestations can pose significant risks to pine forests in the United States and Canada.
Threats:
- Landscape-wide tree mortality
- Damage to mature and pole-sized pine trees
Treatments:
- Early detection and monitoring
- Removal of infested trees
- Application of insecticides
| Species | Regions | Impacted Trees | Treatment Methods |
|---|---|---|---|
| Pine Bark Beetles | US (Minnesota) | Red pine forests | Early detection, tree removal, insecticides |
| Mountain Pine Beetles | US (Western states), Canada | High-elevation forests | Monitoring, infested tree removal, insecticides |
Conclusion
Bark beetles pose a significant threat to trees, particularly when the trees are stressed or weakened. Effective management and prevention are key to preserving the health of trees and shrubs.
One of the primary strategies involves maintaining tree health through hydration, mulching, and pruning, as healthy trees can naturally resist these pests.
Various control methods, such as chemical treatments, pheromone traps, and the removal of infested trees, have been employed with varying success.
It’s also crucial to understand the specific bark beetle species involved, as different species target different trees.
By being proactive and informed, tree owners can mitigate the damage caused by these pests and ensure the longevity of their trees.
Reader Emails
Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about bark beetles. Scroll down to have a look at some of them.
Letter 1 – Bark Gnawing Beetle is Beneficial Predator!!!
Subject: Temnoscheila
Location: Wichita Falls, Texas
May 30, 2014 2:46 pm
We have identified the green beetles on one of our red oak trees as temnoscheila.
We used a tree drench on it a few days ago to systemically rid the tree of the beetles, which are gnawing holes in the bark and making it fall off. But drench can take up to three months to work. Is there anything else you would recommend to help us? We don’t want to lose the tree.
We live in Wichita Falls, Texas, and are in a bad drought. We have been watering the trees with pond water, since we are not allowed to use city water on the yard.
We don’t see the beetles on any other trees (hope they don’t spread). Thanks.
I hope I sent the right picture of the beetles and not my dogs.
Signature: Ercie Hill
Dear Ercie,
We are very excited to be able to post your image of this beautiful species that helps to return trees to humus. We took the liberty of cropping and correcting your image of a Bark Gnawing Beetle. The BugGuide page on the genus is a beautifully designed page.
Daniel, thank you. Sorry my image was not better. My camera doesn’t take very good close-up photos.
Any idea why the beetles are on the oak tree and how to talk them into going somewhere else?
Thanks again,
Ercie Hill
We have very good news for you Ercie, sort of. We just received a complimentary copy of Arthur V. Evans’ new book, Beetles of Eastern North America, and here is what he has to say about Temnoscheila virescens:
“Adults and larvae found in pines infested with bark beetles and are important predators of Dendroctonus. Adults prey on adult bark beetles, while their larvae consume Dendroctonus eggs and larvae.” According to BugGuide, Dendroctonus: “Breed on boles of conifers; sometimes kill healthy trees.”
So, you have photographed the predator, not the problem. We would urge you not to take any action against this magnificent Bark Gnawing Beetle, even though its family name is deceptive. It is feeding on the beetle that is the problem.
The material we are citing lists pines as the trees affected by the Bark Beetle, but that is not to say that the Bark Gnawing Temnoscheila might also prey on Bark Beetles that affect other trees, namely, your oak.
Daniel, thank you. We’ve seen these beetles around here as long as I can remember, just never saw them on a tree. I appreciate your responses – thanks so much.
Ercie
Letter 2 – Bark Gnawing Beetle: Temnoscheila species
Emerald ash borer?
Location: Annapolis, Maryland
December 19, 2011 8:54 am
Hi, I found this insect while chopping wood. At first I was concerned that it was an emerald ash borer as it is the right size (14mm long) and shape. It’s head, especially the eyes and mandibles look quite different though.
It was dead when I found it, seemed to be attached to the wood by its rear end.
Thanks!
Signature: ash borer?
Dear ash borer?,
You are correct that this is not an Emerald Ash Borer, Agrilus planipennis, which is nicely represented in this excellent online pdf prepared by Gary L. Parsons of the Michigan State University Department of Entomology.
On page 55 of that pdf, we located a Bark Gnawing Beetle, Temnoscheila virescens that appears to match your beetle. It is described as: “Length: 8.6-17.8 mm, slightly larger than EAB.
Color bright green or blue-green varying to almost dark purplish-blue, often with brassy reflections. Head large, prognathous, and more evident than in Buprestidae, and the connection of the pronotum to mesothorax is narrowed, waist-like.
T. virescens occurs in the eastern U.S. with T. chlorodia (Mannerhiem), a very similar species, occurring in the western North America. Both species are predators found under the bark of dead trees where they feed on a variety of woodboring beetles.”
That Bark Gnawing Beetle can also be found on BugGuidealong with several other members of the genus.
On the genus page, BugGuideindicates: “can inflict a painful bite if handled carelessly.” Thanks for providing our archives with this convincing Emerald Ash Borer imposter.
