If you've noticed thin strands of sawdust sticking out of the trunk of a young tree, almost like tiny toothpicks, you may be looking at ambrosia beetle damage. Around your Verona home, these beetles tend to show up on ornamental trees that are already under some kind of stress. That's the real answer to why they're there. Ambrosia beetles are attracted to trees that are struggling, so they're often a sign of a bigger issue with the tree itself. Below, we'll cover what ambrosia beetles are, what draws them in, how to spot the damage and what you can do. If you're not sure what's affecting your trees or yard, our pest inspection services can help you sort it out.
What Ambrosia Beetles Are
Ambrosia beetles are very small beetles, often about the size of a grain of rice or smaller. They're part of the same group as bark beetles, but they live differently. Instead of feeding on the wood or inner bark, females bore tunnels into the wood and bring in a fungus that grows on the tunnel walls. The adults and larvae eat that fungus, which is called ambrosia. The name comes from that food source.
Several species are found in the Northeast, including some that came from other parts of the world. The granulate ambrosia beetle and the black stem borer are two invasive species known for attacking ornamental trees and nursery stock.
Why You Have Ambrosia Beetles
Ambrosia beetles are attracted to trees that are stressed. When a tree is struggling, it can give off chemicals, including ethanol, that the beetles can detect. Common causes of stress include:
- Recent planting. Newly transplanted trees are still recovering from root loss.
- Too much or too little water. Flooding, waterlogged soil and drought all weaken trees.
- Cold damage. A late freeze after trees have started to leaf out can injure tissue.
- Mechanical injury. Damage from mowers, string trimmers, construction or storms.
- Poor planting. Trees planted too deep or with circling roots tend to struggle for years.
Thin-barked ornamental trees are frequent targets. Examples include dogwood, redbud, Japanese maple, cherry, magnolia and styrax, though many other trees can be attacked. Adults are usually most active in early spring when they fly in search of new trees.
Signs Of Ambrosia Beetle Damage
- Toothpick-like strands. Thin, compacted strands of sawdust pushed out of small holes in the bark. They're fragile and can break off in rain or wind.
- Pinholes. Very small, round entry holes in the trunk, often on the lower part of young trees.
- Wilting. Leaves that wilt or brown suddenly, sometimes on one branch and sometimes on the whole tree.
- Dark staining. If you scrape away bark near a hole, the wood underneath may be stained by the fungus.
- Sap or ooze. Some trees weep sap from attack sites.
Ambrosia beetles are closely related to other bark beetles, which leave different patterns under the bark. Our guide on signs of bark beetle damage covers those.
Are Ambrosia Beetles Harmful?
To people, pets and your home, no. They don't bite, sting or infest the wood in a house. They need living or freshly cut wood where their fungus can grow.
To trees, they can be serious. A young or stressed tree can die after a heavy attack, both from the tunnels and from the fungus they bring in. Larger, healthy trees are less likely to be affected. Because the beetles spend nearly all their time inside the wood, sprays don't reach them once they're established.
How To Protect Your Trees
- Reduce stress. Water new trees during dry spells, but don't let soil stay soggy.
- Plant carefully. Set trees at the right depth, with the root flare visible, and choose sites with good drainage.
- Protect the trunk. Keep mowers and string trimmers away from bark. A ring of mulch, not piled against the trunk, helps.
- Watch in early spring. Check young and recently planted trees for toothpick strands and pinholes.
- Remove badly infested trees. A tree that's heavily attacked and dying can be a source of beetles for nearby trees. Have it removed and disposed of properly.
- Ask about preventive options. A certified arborist can tell you whether protective treatments make sense for valuable young trees.
When To Call A Professional
Tree treatment and removal are jobs for a certified arborist, and EcoFusion doesn't treat or inject trees. Where we help is in figuring out what's going on. Sawdust around a tree could be ambrosia beetles, but sawdust near your house could point to carpenter ants or carpenter bees, which are a very different problem. Our NJ DEP-licensed technicians can inspect your yard and home, identify what you're finding and recommend a plan using Integrated Pest Management and EPA-registered, eco-safe products.
Ambrosia beetles are usually a sign that a tree needs help. Keeping new and young trees healthy is the best way to keep these beetles away from the landscape around your Verona home.