Living With Red Bay Ambrosia Beetle

Much of the Midwest and East Coast is concerned with Emerald Ash Borer, a beetle that is methodically killing all the ash trees in North America. Although it is currently the most devastating pest, the Emerald Ash Borer is not the only invasive insect pest killing our native trees.

Numerous beetles that bore into trees have been unintentionally imported into the US, primarily in wood that is used for packing trade items. Solid Wood Packing is used in wooden crates and dunnage (scrap wood used to fill the space between the containers and the ship hull to prevent cargo from shifting). Although the wood is required to be treated, compliance is less than 100 percent. Beetle infested wood finds its way into cargo ships bound for North America. When cargo is unloaded, the beetles emerge from the infested wood and fly off to wreak havoc in their new home.

The Red Bay Ambrosia Beetle, Xyleborus glabratus, is an invasive species from Asia. It grows and develops in Red Bay trees and other trees in the Laurel Family. The beetle bores into the tree but does not feed on the wood. The Red Bay Ambrosia Beetle has special structures (mycangia) at the base of its mandibles that store a fungus and transmit it into the wood as the beetle bores. The beetle feeds on the fungus. The fungus can spread throughout the sap wood and kill the tree. There is no cure for an infected tree.

In Asia, the beetle primarily attacks trees that are stressed and healthy Asian trees have resistance to the fungus. In North America, trees have no resistance to the fungus. In areas where the beetles have been detected, up to 90 percent of the red bay trees die within 15 months. The fungus has killed all the Red Bay Trees in some areas such including Hilton Head Island, South Carolina.

The beetle and its fungus are currently confined to the Southeastern United States. On its own, the beetle spreads only a few miles every year. However, the beetle can move hundreds of miles when people unwittingly move infected wood or wood products, most commonly wood used by campers for fires. Campers are encouraged to buy firewood locally and are discouraged from moving wood. In some infested areas, moving firewood has been made illegal with extensive fines attached to slow the spread of the beetle and the disease.

Known hosts for the beetle are Red Bay and Sassafras. However, the fungus has been detected in other trees of the Laurel Family and is capable of killing avocado trees. No one knows what will happen once the Red Bay Ambrosia Beetle reaches the avocado plantations in Southern Florida. The risk for substantial economic loss is high. Efforts to prevent these pests from entering the US and slowing the spread of pests that are already here are important.

Red Bay Ambrosia Beetle
The Beetle is about 2 mm long
Image: Florida DACS,

About jjneal

Jonathan Neal is a retired Associate Professor of Entomology at Purdue University and author of the textbook, Living With Insects (2010). This blog is a forum to communicate about the intersection of insects with people and policy. This is a personal blog. The opinions and materials posted here are those of the author and are in no way connected with those of my employer.
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8 Responses to Living With Red Bay Ambrosia Beetle

  1. Anonymous says:

    This post was very interesting. I live on a large property with a lot of Ash trees so I am aware of the affects of the Emerald Ash Borer but, I’ve never heard of the Red Bay Ambrosia beetle at all. It was cool to learn more about it, especially as it is a potential threat to our environment, and what is being done to stop its progression through the country.

  2. Anonymous says:

    I am from the Midwest and was aware that such bug existed but i was unaware of the fact that is was the Red Bay Ambrosia Beetle. I was also very interested by this article because it explained exactly how the insect affects the wood because this beetle has a structure called mycangia at the base of its mandibles that stores a fungus that is transmitted into the wood as the beetle bores into the tree. This fungus then spreads through out the sap and evidently kills the tree because there is no known cure.

  3. Anonymous says:

    I found this post very informative. I was aware that there was a beetle that killed these trees. I found it very interesting how the beetles came over to North America in wooden crates. However, I was surprised how bad the situation with the Red Bay Ambrosia Beetle was. It is surprising that up to 90 percent of die within fifteen months. It seems that regulations on cargo need to be more readily enforced, but I can understand how sometimes, that does not happen.

  4. Anonymous says:

    I found this post very interesting. I am from the Midwest so I was aware of theEmerald Ash Beetle and how it’s wiping out the native trees in the area. I was unaware how exactly the beetles made it over to America so i found that pretty interesting. Before reading this post I had never heard about the Red Bay Ambrosia Beetle, but i found it pretty crazy how they are wiping out trees in different places and possibly the avacado trees. Hopefully some things can be done to fully prevent these beetles from destroying more of the natural trees.

  5. Lora says:

    Hi,I just came upon this article today. I live in Mobile Alabama & I’m surrounded by a swamp bottom forest that includes Red Bays & Swamp Bays. Yes this nasty beetle has killed the mature trees but I have noticed that the swamp bays that I thought were dead have re-sprouted among the dead growth and are growing. There are many,many baby red-bays growing through-out the forest. They are growing in the vicinity of the dead red-bays. The dead red-bays have no new growth sprouting up from the base of the tree like the swamp bays have.Strange. Also I have a few young tree size red bays untouched and some that have grown almost side by side with the dead red bays and they are thriving. Why would some trees die, others re-sprout and some are untouched.The adult trees have died but their off-spring are popping up everywhere with no sign of infection.The death of these trees was very rapid and all happened at the same time about 2years ago almost overnight it seemed. This insect also killed my full grown sassafras tree.The sassafras sent out 2 runners out from the edge of the forest. The one runner closest to the edge of the forest died like her mother but the other runner showed up about 20 feet away from the mother tree and is growing well.What do you think about these trees “surviving” the attack of the ambrosia beetle. Do you think they may perhaps have some immunity? Do you think that something happened in the soil that could be helping them or protecting them from the fungus?It was heartbreaking to see all these dead trees but I am hopeful now because of all the new growth and they all appear healthy. I have also noticed that some of the swamp bays that re-sprouted last year,their new growth (about 3feet tall) was once again dead & wilted but is back again this year and so far looks healthy!The new growth is growing within the clump that died. The baby red-bays right now are about 12-24 inches tall.The swamp bays are about 3-4 feet tall and more shrubby. Once the tree dies do the beetles leave and what happens to the fungus that is in the trees? I ask because there are so many dead trees, some have fallen but some are still standing.Can the dead trees infect the soil with the fungus or does the fungus die with the trees? Why is there so much new growth in the midst of this plague? Does it move on, die off, or hibernate only to re-emerge? I can’t find any answers regarding this plague and the status of the red-bays/swamp bays in other areas. It seems to me from my own observations that the swamp bay is doing much better than the red-bays in spite of the ambrosia beetle attack.Any thoughts? Anyone.

    • jjneal says:

      You ask good questions.
      This beetle is relatively new to the US so its biology is not yet well understood.
      Studies are limited. It may be some time before the impact is understood.
      Detailed notes on your site could potentially be helpful especially if you note a tree that has survived an attack that killed its neighbors.

      There may be some resistance to the beetle and the fungus.
      For Example: Some avocado cultivars express resistance.
      Healthy Asian laurel species have resistance; only stressed trees are attacked. There may be some resistance in North American trees.
      Beetles may have a preference for trees larger than a minimum size. (This is true for ash borer.)
      Effects may vary with species of plant.
      Stump sprouts have been noted, but their survival rate remains to be seen.

      There are other closely related ambrosia beetles that also may be capable of transmitting the fungus.
      Standing dead trees can be a source of fungus.
      Typically the fungus needs a beetle to create a tunnel in a tree to successfully grow.

      Invasive beetles are altering long standing ecological patterns and forest composition. We often don’t know the effects until after they appear.
      It is very important to limit the spread of the beetle and fungus by not moving firewood or other wood products.

  6. Gabriel A. Adedeji says:

    I am currently working on Terminalia mantaly pests. Beetles have been found to be the most devastating pest. I need entomologist to help identify the beetle. I will send the pictures of the beetles via email.

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