Homeowners in the Atlanta Metro area have to keep an eye out for a number of tree pests and diseases. But while many of these problems produce relatively familiar signs, such as leaf discoloration, bark holes, or mushrooms, some leave people puzzled.
For example, many local residents are shocked to see toothpick- or noodle-like projections emerging from the trunks of their trees. They’re certainly a bit odd looking, but more importantly, they’re a sign that your trees may be in very serious trouble.
Read on to learn more about this issue and the steps you need to take.
What Are the Toothpicks Sticking Out of My Tree?
The toothpick-like tubes emerging from your trees are almost certainly frass sticks produced by ambrosia beetles.
They’re essentially made up of insect waste (frass) and the wood dust created when they bore into a tree. They often look pretty solid, but they’re actually quite delicate. A gentle breeze, raindrop, or finger tap will often cause them to fall apart.
Because they’re so fragile, they don’t last very long after they’re produced. This means that their presence almost always indicates an active infestation.
What Are Ambrosia Beetles?
Ambrosia beetles are wood-boring insects with an interesting life strategy — rather than consuming the wood of the trees they colonize like many boring insects, they actually subsist on a symbiotic fungus found within the galleries they create.
In fact, they do more than just eat the fungus; they actually tend to it in a manner reminiscent of farming. They’ll keep their “gardens” clean and free of invaders, ensure it is available to their larvae, and then transport it to new trees when they reach adulthood and disperse.
More than 30 kinds of ambrosia beetles have been documented in Georgia, but the granulate ambrosia beetle (Xylosandrus crassiusculus) is the most notable species found in the Atlanta area. It was first detected in South Carolina in the 1970s, but it quickly made its way to the Peach State, where it’s spread widely.
How Do Ambrosia Beetles Harm Trees?
Ambrosia beetles harm trees in two basic ways:
- Their tunneling physically damages the tree’s tissues, particularly when large numbers of beetles attack a small tree.
- The fungi they introduce can interfere with the tree’s vascular system, limiting the movement of water and nutrients.
Healthy, mature trees are sometimes capable of sealing off the damaged area and surviving ambrosia beetle attacks. But stressed, young, or recently transplanted trees often begin declining shortly after an infestation.
What Trees Do Ambrosia Beetles Attack in Georgia?
Georgia’s native ambrosia beetles primarily bore into dead or dying trees, which means they are typically regarded as beneficial insects that play a role in the decomposition process. But several of the invasive species — including the granulate ambrosia beetle — can sometimes cause problems for healthy trees.
The granulate ambrosia beetle alone has been documented boring into more than 100 tree species. A few of the most common victims include:
- Apple (Malus domestica)
- Chinese Elm (Ulmus parvifolia)
- Crape Myrtle (Lagerstroemia spp.)
- Dogwood (Cornus spp.)
- Fig (Ficus carica)
- Golden Rain Tree (Koelreuteria paniculata)
- Magnolia (Magnolia spp.)
- Maple (Acer spp.)
- Ornamental Cherry (Prunus spp.)
- Peach (Prunus persica)
- Pecan (Carya illinoinensis)
- Persimmon (Diospyros virginiana)
- Plum (Prunus spp.)
- Redbud (Cercis canadensis)
- Rhododendron (Rhododendron spp.)
- Shumard Oak (Quercus shumardii)
- Sweetgum (Liquidambar styraciflua)
This list is certainly not exhaustive, but these are some of the trees under greatest threat from the granulate ambrosia beetle.
Other Symptoms of Ambrosia Beetle Infestations
While frass toothpicks are the most common sign of an ambrosia beetle infestation, there are a few other clues that can point to their presence, including:
- Tiny holes in the bark. If the frass toothpicks have already fallen off a tree, you may see perfectly round, 1- to 2-millimeter holes made by the beetles.
- Sawdust at the base of the tree. When the frass toothpicks fall apart, the frass and wood material can pile up at the base of a tree.
- Sap oozing from the tree. Some trees try to defend themselves from borer attacks by flooding the entrance holes with sap. This is particularly common among peach, cherry, and plum trees.
- Stained wood. If you peel away a small amount of bark from an infested tree, you may notice blue, gray, or black stains, caused by the fungus carried by the beetles.
- Branch flagging. As infestations progress, the afflicted tree becomes unable to transport water and nutrients effectively, which can cause the death of individual branches in the canopy (“flags”).
- Sudden death. Some trees suffer such overwhelming attacks that the entire canopy may turn brown, leading to the death of the tree in a matter of days.
If you notice any of these symptoms, you’ll want to contact AKA Tree Service immediately to obtain a positive identification, so you can get ahead of the problem.
Ambrosia Beetle Prevention and Treatment
Unfortunately, there isn’t a lot you can do to help trees that are already suffering from an active ambrosia beetle infestation. Once the beetles have tunneled into the tree’s wood, they’re largely shielded from insecticidal sprays, and because they don’t actually eat the tree’s wood, systemic pesticides aren’t helpful either.
That’s why Georgia property owners must focus on supporting the health of susceptible trees and preventing infestations from occurring in the first place. There are a few ways to do this:
- Ensure your trees are adequately watered before and during the summer.
- Spray the bark of vulnerable trees with a permethrin- or bifenthrin-based insecticide when beetle activity begins.
- Quickly remove trees suffering from heavy infestations and burn or chip the wood.
- Protect trees from mechanical damage or other forms of stress.
- Avoid unnecessary fertilization during the early spring, as this may make trees more attractive to the beetles.
Ultimately, most homeowners will find that they require the expert guidance of an ISA-certified arborist to effectively protect the trees on their property from these insects.
Ambrosia Beetles in Georgia: FAQ
Still have questions about the ambrosia beetle in Georgia? We’ve answered a few of the most common questions our clients have below.
How can you get rid of ambrosia beetles?
It’s difficult to eliminate ambrosia beetles once they tunnel into a tree, so prevention is key. This means supporting your trees properly to keep them in the best condition possible and potentially using insecticides to prevent new infestations from starting.
Do ambrosia beetles attack healthy trees?
Ambrosia beetles can attack healthy trees, but they prefer trees already weakened by drought, disease, or other pests.
What attracts ambrosia beetles?
Ambrosia beetles are attracted to the ethanol emissions produced by stressed trees.
Are ambrosia beetles invasive?
There are a number of ambrosia beetles native to the United States, but most of these species focus on dead (or nearly dead) trees. It is the invasive species — such as the granulate ambrosia beetle — that cause the most problems for healthy trees.
What is the best spray for ambrosia beetles?
Bifenthrin- and permethrin-based bark sprays are the best products for preventing new infestations, though they’re not very effective for killing beetles that have already tunneled into the bark.
Do ambrosia beetles kill trees?
Yes, ambrosia beetles can and do kill some trees. Healthy, mature trees can sometimes fight off attacks, but young or stressed trees may die following severe or repeated infestations.
Do trunk injections work for ambrosia beetles?
No — because ambrosia beetles do not feed on tree wood, systemic trunk injections are ineffective against them.
Plant Health Care Services from AKA Tree Service: Protect Your Trees
By now, you can probably understand why people are so disappointed to see the telltale toothpicks ambrosia beetles produce sticking out from their trees. By the time these signs appear, treatment becomes much more difficult.
It also highlights the importance of proactive tree care. Like many other common tree pests and pathogens in Georgia, ambrosia beetles are easier to prevent than to treat.
If you’d like to protect your trees and give them the best chance to thrive, contact AKA Tree Service today and request a free plant health care estimate. We’ll be happy to send one of our ISA-certified arborists to your property to assess your trees and develop a plan for supporting your trees’ ongoing health.
Sources & References
- Georgia Forestry Commission – “Ambrosia Beetles in Urban Trees”
This technical report details the biology of ambrosia beetles and provides specific management protocols for protecting ornamental and hardwood trees in urban landscapes.
https://gatrees.org/wp-content/uploads/2020/02/AmbrosiaBeetlesinUrbanTrees.pdf - University of Georgia Cooperative Extension – “Granulate Ambrosia Beetle”
This resource outlines the identification, host range, and chemical control options for the granulate ambrosia beetle, focusing on its impact within nursery and landscape environments.
https://extension.uga.edu/programs-services/landscape-pest-management/Nursery-pests/granulate-ambrosia-beetle.html - Walter Reeves – “Asian Ambrosia Beetle Control”
This publication offers practical advice for homeowners and arborists on detecting early signs of infestation and applying protective trunk sprays to vulnerable tree species.
https://www.walterreeves.com/insects-and-animals/asian-ambrosia-beetle-control/
