Eucalyptus Longhorned Borer – The Garden Pest Extraordinaire

If you have eucalyptus plants in your garden, you need to know all about the eucalyptus longhorned borer, if you want to keep them safe.

Borers are known to be one of the most devastating types of hardwood pests, and rightly so. 

The eucalyptus longhorn borer larva girdles trees (discussed in detail later) and can potentially kill them.

The eucalyptus tree genus falls among the most popular urban forest trees. 

Unlike many other tree species, the risk of fires from dead leaves piling up in loads under trees is lower. 

This also makes eucalyptus longhorned borer infestation a common problem. Let’s find out more about these pests and how you can tackle them.

Eucalyptus Longhorned Borer
Eucalyptus Longhorn

What Is a Eucalyptus Longhorned Borer?

Eucalyptus longhorned borer refers to two closely related borer beetle species – Phoracantha semipunctata and Phoracantha recurva. 

The former originated in Australia and was eventually spotted in Southern California in 1980. 

The latter was discovered in 1995 in several Californian counties – San Bernardino, Los Angeles, Orange County, and Riverside.  

Adult eucalyptus longhorned borers feed on the pollen of eucalyptus trees and lay eggs in the bark of eucalyptus trees. 

Stressed and freshly cut trees are particularly at risk from these borers.

What Does It Look Like?

Growing to a size of about an inch with brown bodies, adult eucalyptus longhorned borers have segmented antennae. The legs and antennae are of a reddish-brown color.

Like all beetles, they feature a pair of elytra, or hard hind wings.

Yellow-brown in color, these elytra have a thick black band crossing both their posterior ends. Each wing also features two vaguely connected spots.

The larvae resemble white grubs and are often over an inch long. However, you’ll rarely see them as they remain hidden within the tree bark.

Eucalyptus Borer

What Damage Does It Cause?

Moving on, let’s check out what kind of damage Eucalyptus longhorned borers can cause. 

The discoloration and the wilting of eucalyptus leaves are among the first symptoms of an infestation. 

Eventually, the tree limbs will begin to die back too. As the larvae continue to feed on the tree, oval-shaped holes will start appearing in the bark.

The problem with P. semipunctata/recurva infestation is that the larvae destroy the cambial layer – the layer responsible for the transportation of water and nutrients in trees. 

If left unchecked, the infestation will spread throughout the circumference of the tree and may remove a strip of bark (known as girdling).

You may also notice a liquid oozing out of the trunks and limbs of infested trees. It’s a resin produced by the trees to resist a borer attack.

Different eucalyptus species display varying levels of resistance. It depends on the attributes of eucalyptus trees. 

For instance, a drought-resistant species will also be less vulnerable to borer infestations.

Longhorned borer attacks are particularly common during the hot summer months when the trees are stressed. 

When infesting healthy trees with plenty of moisture content, the larvae may suffer mortality in trees by drowning. 

Opening up a tree infested with these pests will also reveal large networks of tunnels bored by the larvae. These tunnels are usually filled with their excrement.

Lifecycle of the Eucalyptus Longhorned Borer

The lifespan of a eucalyptus longhorned borer may vary a lot, depending on the season. In summer or spring, three to four months are enough for them to complete their life cycle. 

The ones hatching in winter take longer, up to nine months. The four life cycle stages are as follows:

Larva of a Eucalyptus Borer

Egg: Female beetles of this species lay up to 300 eggs, distributing them into groups of 3 to 30. These eggs are typically laid in loose bark and take around a week or two to hatch.

Larva: Eucalyptus longhorned borer larvae may take anywhere from 70 to 180 days to develop, depending on the moisture content in the wood. 

The drier the eucalyptus wood, the slower would be their development process. 

These larvae start boring tunnels and mine inward, going through the bark to reach the cambium and sometimes the xylem.

Pupa: Once the larvae are done feeding and ready to pupate, they create pupal chambers in the wood. 

Plugging off the entrances with wood shavings and frass, they remain inside and pupate into adults.

Adult: The adult beetles chew their way out through the wood shaving and frass plugs I mentioned earlier. They eventually lay eggs again, and the cycle continues.

Depending on the egg-hatching timings, there might be two to three generations of eucalyptus longhorned borers per year.

How To Get Rid of Eucalyptus Longhorned Borer?

If you’re dealing with a eucalyptus longhorned borer infestation, here are a few remedies that you may try.

Cultural remedies

  • As water-stressed trees are more vulnerable to borer attacks, make sure to irrigate the eucalyptus trees well. Apply the water at a small distance from trees directly below the edge of the canopies. Don’t water too close to the tree – it would promote root disease.
  • If you’re keeping eucalyptus logs for use as firewood, try to dry them quickly or solarize them. Any amount of moisture may promote beetle generation.
  • Heavily-infested host trees might need to be cut down, burned, or chipped to prevent the spread of the pests.

Eucalyptus Borer

Biological remedies

  • Specialized parasites can get rid of an infestation by destroying the borer eggs. A. Longoi, an encyrtid egg parasitoid, is particularly effective.
  • If you’re going to try biological remedies, avoid applying any persistent and broad-spectrum insecticides on the bark.

Chemical remedies

  • Managing eucalyptus longhorned beetles requires systematic insecticides, i.e., insecticides that move through trees along with water and nutrients.
  • Chemical remedies might be especially necessary against P. recurva due to its resistance to biological remedies.

Apart from these, you can use tree care kits to keep your eucalyptus trees healthy, strong, and resistant to infestations.

Frequently Asked Questions

How do you treat borers in eucalyptus trees?

Borers in eucalyptus trees can cause significant damage to the tree, so treatment is essential.
Trees should be inspected for signs of borers, such as holes in the bark and sawdust on the ground.
Depending on how far along the infestation is, one may need to remove large chunks of bark to reach and exterminate the larvae.
After destroying the borers, prune affected branches and apply an insecticide or antifungal treatment.
Additionally, improving overall tree health by irrigating during times of drought and providing fertilizer during active growing periods may help prevent future infestation.

Can a tree survive borers?

Yes, a tree can survive borers depending on its condition. Borers are wood-boring insects that feed off of living tissue inside your trees.
If the tree is healthy and adequately managed, it has plenty of defenses against borer populations.
It is important to carefully inspect your tree for signs of infestation and to address any issues as soon as possible before they become more severe.
Proper pruning techniques and balanced fertilization can also help a tree avoid or overcome borer damage.
Proper cultural care, like preventive treatments in the early spring season, can also deter borer larvae from taking up residence in your trees.

What insecticide kills borers?

Borers can be difficult to kill as they live and feed in the inner bark of trees.
The most effective insecticide for exterminating borers is Dursban, which is a broad-spectrum organophosphate pesticide that eliminates both wood-boring insects and their larvae.
When using insecticides, it’s important to select a product with appropriate levels of toxicity based on the size of the borer being targeted.
These products should only be used according to label instructions by trained professionals to minimize risks to non-target organisms and human health.

What bug kills eucalyptus trees?

The eucalyptus longhorn beetle is a major pest in Australia, and it kills eucalyptus trees by boring tunnels into the trunk and hollowing out the inside.
Their larvae feed off of nutrients in the tree, eventually starving it of life.
This beetle can spread rapidly through many different regions, as the tree-to-tree transmission is common. As a result, infested trees can die very quickly, making them a serious threat to forests.
Control methods include pruning affected branches and using specialized insecticides.

Wrap Up

As we can see, the two borer variants in question can cause significant damage to eucalyptus trees and may even result in tree mortality. 

Protect your eucalyptus trees from drought stress to keep them safe and take the necessary steps to treat a borer infestation. 

Thanks for reading, and I hope you can control the borer infestation before it grows out of hand.

Reader Emails

Considering the threat that these bugs hold to eucalyptus plants, it is of little surprise that our readers have sent in several letters trying to identify them.

Read through and understand what this bug looks like, where it can be found, and what people are doing in order to get rid of it from their eucalyptus plants.

You might also get to read a letter or two admiring the beautiful colors and long antennae of these borers!

Letter 1 – Eucalyptus Tree Borer


Hi, I Live in West Los Angeles/Santa Monica area and this morning – New Year’s Day, while blissfully watching the Rose Parade on TV with morning cuppa java this noise catches my ear – and my cat’s ear. It sounded like a small ornament had dropped off the Christmas Tree onto the window sill. Upon investigation it is a really horrid bug. Looks a bit like a cricket, 6legs, antenna and beige body with black spots. Body in length is approx 1″.I have seen crickets crawl, they’re slow and lumbering, so I was a bit relived that it wasn’t going to attack me in any way. I got the vacuum and prepared to suck the icky crawler into the swirling vortex of death. Wrong! The thing can fly! I lost it – both literally and figuratively. I got near it with the hose when it took off and disappeared into the darkness behind the tree and the cat and I quickly retreated to the safety of the bedroom to regroup and formulate a strategy on capturing the winged beast. I was afraid to leave it alone for too long lest I lose track of it in the house (not acceptable) so I grabbed the cat and we moved back in to the battle zone to wait for its reappearance. Sure enough within minutes it flew toward the window and banged into it with a loud “thwack”. I did manage to get it sucked up in the vacuum but it was still inside the plastic container crawling around lively in the dust. I thought it would surely die with the trip up into the vacuum, or choke on the dust but it didn’t. I looked closely at the bug and your site, but didn’t see any of the bugs that resemble this thing. I dumped it into a plastic trash bag tied it tightly and took it out of the house. Yeech! What is that thing? Did it come in on the tree or is it local to the area and how can I avoid seeing one ever again in my home? Need a glass of champagne now to steady my jangled nerves and will hope to hear from you when you catch up on emails. Thanks, Bugged by the Bug on the Westside Dear Bugged, Your letter is great, but lacking in some helpful identification details. I’m going to take a wild guess and say perhaps a beetle, the Eucalyptus Tree Borer. Here is a photo of a dead one sent last year. Ed. Note: We just received this information: (08/09/2005) identifications Hello – I was recently shown your site, and it is excellent. My specialization is longhorned beetles, and in cruising around I notice a number of incomplete or uncertain IDs for this family. I don’t know if you are interested in receiving this sort of input, but if you are, I offer the following additions to your identifications. The eucalyptus borer in this photo (and also shown elsewhere on one of the other pages of your site) is Phoracantha recurva, nor P. semipunctata. Both species now have become well-established in California. Cheers. Frank Hovore

Letter 2 – Eucalyptus Tree Borer


Scary Bug Hello, Could you please help me to identify this bug I have never seen one of these before. It was on our ceiling and was terrifying my young son (unfortunately the bug didn’t survive). It was about one inch long excluding legs and feelers. I would like to be able to tell my son what it is and whether or not it is harmless. We live in San Diego, California. Thank you, Caroline Gilbert Hi Caroline, The Eucalyptus Tree Borer, Phoracantha semipunctata, is harmless to you, but will do considerable damage to your eucalyptus trees. This insect was introduced to southern California from Australia where it has multiplied due to the absence of natural predators. Young bore into the wood of Eucalyptus trees and have destroyed many stands of this common tree.

Letter 3 – Eucalyptus Longhorned Borer from Australia


Unidentified bug Hi. Attached is a photo of a bug found in Melbourne, Australia. I have looked all over the web but can’t find anything. Have you any idea what it is? Thank you! Corey Wright Hi Corey, Sorry for the delay. We are just returning to old emails that we never had a chance to answer. This is a Eucalyptus Longhorned Borer Beetle, Phoracantha semipunctata. This beetle has been introduced to Southern California where it is a major cause of eucalyptus damage. The larvae are the borers that feed on wood.

Letter 4 – Eucalyptus Borer


Long antennae beetle found in So. California Seems a lot smarter than cockroaches and a lot slower. Can fly very well and seemed to make a quiet hissing noise when we first moved the grass around him. After the pursuit began, he went silent and we almost lost him as a result. He was found on the grass near some wood from a eucalyptus we had just cut down. Weerdbugs Findmi Carlsbad California 3.5 miles East of the Ocean
Eucalyptus Borer
Eucalyptus Borer
Dear Weerdbugs, It has been many years since we have received an image of a Eucalyptus Borer, Phoracantha recurva or Phoracantha semipunctata.   According to BugGuide, there are two species, both introduced from Australia.  Our edition of Charles Hogue’s Insects of the Los Angeles Basin was printed in 1993 and only mentions Phoracantha semipunctata, and indicates it was introduced “to Southern California, probably in 1982.”    Hogue also writes:  “Until this borer came on the scene, its host, eucalyptus, had been virtually free of major pests since its own arrival here after the 1860s.  It is uncertain, however, how serious a threat the Eucalyptus Long-horn Borer poses, because the beetles probably only attack trees weakened by lack of moisture, disease, or other stresses.  they also infest freshly cut wood.  Damage by larvae is characteristic and may be extensive because of their large size (length up to 1 1/2 in., or 40 mm).  They form deep broad galleries under the bark and, as they reach maturity, they girdle the tree and may kill it.”   Because it is an introduced species that has spread in California, we are going to include this Eucalyptus Borer in the Invasive Exotics section of our site, but since the beetle feeds on an introduced tree species, it really doesn’t pose as much of a threat to the native California ecosystem.

Letter 5 – Eucalyptus Tree Borer


I found this beetle dead at Angel’s Gate art center in the Point Fermin Area of San Pedro, Calif. Could you please help me identify it. Latin name, common name and something about its life style. This is the first time I have seen this beetle. Thank you.

Dear Yvetta,
Thanks for sending in the photo. Your specimen is a Eucalyptus Long Horned Borer, Phoracantha semipunctata. They were probably introduced to California in 1982 near El Toro, and it has steadily moved throughout Southern California. The grubs bore into Eucalyptus trees, often weakening them. They are considered a pest.

Thank you so much. It was a new one to me. I will be on the lookout. We will put it in the collection.

Ed. Note: We just received this information:
(08/09/2005) identifications Hello – I was recently shown your site, and it is excellent. My specialization is longhorned beetles, and in cruising around I notice a number of incomplete or uncertain IDs for this family. I don’t know if you are interested in receiving this sort of input, but if you are, I offer the following additions to your identifications.
The eucalyptus borer in this photo (and also shown elsewhere on one of the other pages of your site) is Phoracantha recurva, nor P. semipunctata. Both species now have become well-established in California. Cheers.
Frank Hovore

Letter 6 – Eucalyptus Longhorned Borer from Australia


Beetle found in friends work in melbourne australia Wed, Feb 4, 2009 at 3:14 AM Hello my friend found this bettle / bug in his car dealership in melbourne australia & we cant seem to work out what type it is. It is approx 6cm in length. I really cant give you 2 much more info then that but would really love to find out.  thank you B. Marshall essedon, melbourne Australia
Eucalyptus Longhorn Borer
Eucalyptus Longhorn Borer
Dear B, This is one of two closely related species commonly called the Eucalyptus Longhorned Borer or Eucalyptus Tree Borer, either Phoracantha semipunctata or Phoracantha recurva.  Both species which are native to Australia have also been introduced to southern California where there are numerous cultivated eucalyptus trees.

Letter 7 – Eucalyptus Borer


Larger than normal for Berkeley Wed, Jul 1, 2009 at 4:39 PM I’ve found the insects here in Berkeley to be generally fewer and less varied than where I grew up in rural Wisconsin. But a few weeks before I move back to the midwest this one turned up on my bedroom ceiling two nights ago. I’ve never before seen one in Berkeley. The body is 1 inch long and 0.25″ inch wide, and each antenna is 1.25″. I kept her occupied with a raisin during the photoshoot, which she seemed to appreciate. What is it? Finally something large and not a crane fly Berkeley, CA
Eucalyptus Borer
Eucalyptus Borer
Hi Finally, This is a Eucalyptus Borer in the genus Phoracantha. There are two species with the same common name. Phoracantha recurva and Phoracantha semipunctata were both accidentally introduced from Australia. The two species are quite similar and we don’t feel qualified to determine which of the species you have found. The larvae bore in the wood of eucalyptus trees. Update: Thank you for the response!  Between those two, it seems to be clearly a Phoracantha semipunctata, based on the description and P. semipunctata photo here… …and the P. recurva photo here… — Finally

Letter 8 – Eucalyptus Borer


Checkered Beetle, I think 12 July 2009, 9:03 AM We have lived in Southern California for two years and this is the first time I have ever seen this “bug.” First discovered it in the garage a couple of weeks ago. I thought it was a roach at first, but because of the markings, I decided it wasn’t. A few days later there was one in my bedroom, high up on the wall near the ceiling. This one is on the wall in the dining room; near the back patio door, also high up near the ceiling. My 4 year old son asked, “what kind of bug is that?” I didn’t know, so here we are asking you! Thanks! Sara and Lane Coastal Southern California
Eucalyptus Borer
Eucalyptus Borer
Hi Sara and Lane, You are the first letter we are posting in over two days.  We have  been without a computer while Apple transferred data from the old computer to the new one.  This is a Eucalyptus Borer in the genus Phoracantha.  We believe it is Phoracantha recurva described  on the UC Davis Statewide Integrated Pest Management Website as:  “mostly cream to yellowish; dark brown areas primarily limited to rear third of elytra”

Letter 9 – Eucalyptus Borer and Pharaoh Ants in Hawaii


Phoracantha recurva (Eucalyptus Longhorned Borer) January 5, 2010 Okay so I have already identified this beetle, however… I am wondering why it is that Hawaii seems to be left out of so many United States bug guides. I understand that we aren’t part of the 48 contiguous states, nor are we even attached to the continent; but it just seems rather unfair. We have a plethora of insects here, and I am sure that there are more people than just me who are interested in them. Sorry, I am just vaguely aggravated that whenever I want to find a “hawaiian bug” whether it is endemic to Hawaii or not, I have to search through a very long list of bugs. (This is my reference that I use for Hawaii ) Sorry for the rant, just a little perturbed. And yeah the little guy/gal got smooshed, but onl y cause I was moving my fan and didn’t notice him. The ants didn’t waste any time in trying to devour him either, I actually had to fend them off in order to take this photo. Tina Honolulu, Oahu, Hawaii
Eucalyptus Borer and Ants
Eucalyptus Borer and Pharaoh Ants
Dear Tina, We totally sympathize with your discontent because as an international insect identification website that has posted many Hawaiian bugs, we here at What’s That Bug? often have a very difficult time identifying specimens from some parts of the world, including Hawaii.  The Continental U.S. tends to have very good identification resources, as does Australia, but some locales have a noticeable dearth of information online.  France, for instance, has very few sites for identification purposes, and we rarely get requests from France.  Are we to believe that there are no insects in France, or that the French people don’t care about insects, or perhaps there is some other reason for the lack of resources available online.  Hawaii is underrepresented as well.  Perhaps you should contact your local universities to see why they don’t have websites devoted to insect identification.  We do applaud your proper identification of a Eucalyptus Borer though we aren’t certain which species it is since both Phoracantha recurva and Phoracantha semipunctata look similar and BugGuide does not explain how to correctly distinguish them from one another.  It is a species introduced from Australia, but luckily, its natural food, the eucalyptus trees, are also introduced.  The ants in your photo appear to be Argentine Ants, Linepithema humile based on our own experience and images on BugGuide.  Like the Eucalyptus Borer, the Argentine Ants are invasive exotic species that was introduced to Hawaii.  According to the Ants in Hawaii website:  “Hawaii is one of the few places on earth believed to harbor no native ant species. The extreme isolation of the island chain has meant that ants never managed to arrive on their own. Today, over 40 ant species have become established in Hawaii. This assemblage is unique in that nearly all the species qualify as “tramps” (species with habits and life histories that make them exceedlingly good at moving about in conjunction with human activity). Among them are a majority of the world’s most successful–and damaging–invasive species. Oops… Phoracantha semipunctata would actually seem to be more fitting… The only difference that I can actually visibly see is at the top of the wings on P. semipunctata the dark region is more pronounced than with P. recurva. Sorry about the ranting once again, I just get vaguely irritated that Hawaii is constantly not included in bug identification guides for the U.S. Hawaii does have a site that will assist with identification of local flora and fauna (, but I actually prefer your site. I wasn’t upset with your site, so I really hope you didn’t take it as such. Your site was actually how I identified the beetle to begin with (should have just come here in the first place… lesson learned). Sorry if there are any grammatical errors, or typos, it is getting rather late here, but I just wanted to clear all that up. Oh and could those ants be pharaoh ants instead? I looked up the Argentine ant, and an eighth of an inch is a bit too big for those ants (the beetle was rather small, maybe half of an inch or so). I will try my best to get better macros of them, but they move rather quickly. Hi again Tina, According to the Featured Creatures website, the Pharaoh Ant is Monomorium pharaonis.  We also found the Red Imported Fire Ant, Solenopsis invicta, on BugGuide, which is a tiny species that stings.  BugGuide indicates:  “The Red Imported Fire Ant is the most aggressive and widespread of the fire ants found in North America. It was introduced from South America into the United States between 1933 and 1945.  If their nest is stepped on, the workers rush out and sting the feet and legs of the intruder. Each sting results in a small, acutely painful wound that develops into a pustule in 24 to 48 hours. As the pustules heal they become itchy and can become infected.”  The Red Imported Fire Ant is not reported from Hawaii, so you are probably correct with the Pharaoh Ant ID.  The University of California Pest Management Program has a good page of the Pharaoh Ant.

Letter 10 – Eucalyptus Longhorned Borer from Morocco


What is this? January 9, 2010 This bug was found on our rooftop terrace in Casablanca, Morocco. It was alive but lethargic – perhaps a bird got to it. Its length is approximately 3 cm. Later, after I took the photo, it climbed the vertical leg of a wooden stool that was nearby and tried to hide in a nook. I’ve never seen this bug here before. Do you have any idea what it is? Amina Casablanca, Morocco
Eucalyptus Longhorned Borer
Eucalyptus Longhorned Borer
Dear Amina, We believe your letter might be the first identification request we have received from Morocco in the nearly ten years our column has been online.  This sure looked to us like a Eucalyptus Longhorned Borer, one of two species in the genus Phoracantha, but we were uncertain if this Australian native, which has been introduced to California and Hawaii, had found its way to the Mediterranean.  According to the excellent UC Riverside Center for Invasive Species Research website:  “P. semipunctata has been accidentally introduced into virtually all Eucalyptus-growing regions of the world (e.g., Brazil, Canary Islands, Chile, Egypt, France, Israel, Italy, Morocco, Reunion Island, Spain, and South Africa) and is causing significant tree mortality in many of the areas it has invaded. P. recurva is demonstrating a similar high level of invasion throughout areas of the world with significant eucalyptus production.
Eucalyptus Longhorned Borer
Eucalyptus Longhorned Borer
Ed Note: After posting our reply, we checked, and we have actually received three other letters from Morocco. Wow…thank you for the amazingly quick response! Our immediate neighborhood doesn’t have many trees, so not sure how this little guy ended up on our roof. Maybe he blew in with some of the very gusty rain we’ve had recently, or a bird decided he wasn’t good pickings. Many thanks for your terrific service! Off to read up on Eucalyptus Longhorned Borers. ~ Amina

Letter 11 – Eucalyptus Borer


What beetle is this? Location:  El Sobrante California September 10, 2010 4:31 pm Found a bunch of these in our garage, Never seen them before. Its about 1.3 inches long (this one had expired) Signature:  Peter Wallace
Eucalyptus Borer
Hi Peter, Were you storing cut eucalyptus firewood in your garage?  This is a Eucalyptus Borer.  There are two similar species in the genus Phoracantha (see BugGuide) that were accidentally introduced to Southern California from Australia and they have both become well established since their native food, the Eucalyptus trees, were extensively cultivated in California.  We believe your specimen is Phoracantha semipunctata.

Letter 12 – Eucalyptus Borer


Long Antenna beetle Location: San Diego, CA December 2, 2010 4:33 pm Hi, I found this beetle on the outside of a trash can in our warehouse. Our office would love to know about this guy. We released him back into the ”wild”, but not with getting a picture of his smiling face first! I thought maybe he came in on a shipment of flowers. He was found during the day, in Southern California in the cool part of early December (highs in the 60s, lows in the 30-40s). Signature: Thanks! Melinda
Eucalyptus Borer
Dear Melinda, Your beetle is one of the Long Horned Borer Beetles in the family Cerambycidae.  It is a Eucalyptus Borer, an insect that was accidentally introduced from Australia.  Its larvae feed exclusively on wood of eucalyptus trees, another introduced species in California.

Letter 13 – Eucalyptus Longhorn Borer


Picture of Beetle Location: Orange County, Southern California, USA April 21, 2011 8:31 am can You Identify this Beetle, found in Southern California. In a Park in Orange County. Signature: FELIPE ANTILLON
Eucalyptus Longhorn Borer
Dear Felipe, We are sorry about the delay in our response, but we were on holiday.  We have started with the oldest emails that arrived in our absence and we are going to post those that we find the most interesting.  Your beetle is an imported exotic species, but luckily, it feeds on an imported exotic plant and it does not have a direct effect on our native southern California ecosystem.  This is one of two closely related species that are both known as Eucalyptus Longhorn Borers.  They are native to Australia.  They first appeared in Southern California in the early 1980s when their presence did not garner much attention because that coincided with the Med Fly eradication program.  Residents are advised against transporting eucalyptus firewood as this is known to spread the Eucalyptus Longhorn Borers to new locations.  Since the eucalyptus trees have become ubiquitous in much of the southwest, these invasive exotic beetles have a significant economic impact.  The larvae bore tunnels and galleries under the bark and if they are especially numerous, they may kill a tree.

Letter 14 – Eucalyptus Borer from Australia


What is this Location: Melbourne, Australia February 29, 2012 7:42 pm I think this chap flew into my 5th floor hotel room at night. I am from the Uk and have never seen anything like this before. Can anyone help. It flew quite loudly and was approx an inch in length Signature: Richard
Eucalyptus Borer
Hi Richard, This is a Eucalyptus Borer in the genus Phoracantha.  The larvae bore in the wood of eucalyptus trees. 

Letter 15 – Eucalyptus Borer from Australia


Subject: what type of bug in south australia is this? Location: South australia December 16, 2013 3:39 am Hey ive found this bug and trying to figure out what sort it is. is it dangerous? They keep arriving. Thanks Matt Signature: Att Matt
Eucalyptus Borer
Eucalyptus Borer
Dear Att Matt, This is a Longhorned Borer Beetle in the family Cerambycidae, and though the markings on the elytra or wing covers are not typical of what we are used to seeing, we believe it is a Eucalyptus Borer in the genus Phoracantha.  We did find a photo posted to a Russian Coleoptera website that looks very similar to your individual.  We are quite familiar with the Eucalyptus Borer in Southern California because without any natural enemies, it is considered to be a significant pest to the eucalyptus trees that are so common in our area.

Letter 16 – Eucalyptus Borer adult and larva


Subject: Looking to identify beetle Location: Alongside Canyon in Spring Valley -San Diego California February 5, 2014 9:47 pm Hello and thank you in advance for your assistance in identifying this beetle. Found in seasoned Eucalyptus logs that we were cutting for firewood. A dozen or so Beetles and larva. Signature: Linda Diaz De Leon
Eucalyptus Borer
Eucalyptus Borer
Hi Linda, Both the adult beetle and the larva are Eucalyptus Borers in the genus Phoracantha.  There are two similar looking species, and we are unable to tell one from the other.  Eucalyptus Borers are native to Australia, but they have been introduced to North America and they are relatively common in California due to the ubiquity of the Eucalyptus host trees.  In an effort to keep populations of Eucalyptus Borers from spreading, people should not transport firewood far from the source of the growing trees.  You can find an image of the larva on Forestry Images.
Larva of a Eucalyptus Borer
Larva of a Eucalyptus Borer
Thank you very much for your time expertise. Linda

Letter 17 – Eucalyptus Borer invades home


Subject: What is this!?!? Location: Pomona, CA February 13, 2014 3:00 pm Hello Bugman, About a month or so ago, my roommates and I noticed these fairly large beetle-like bugs starting to appear in our living room. They have very long antennaes and are almost always either on the ceiling or on walls. We live in southern California, about 30 miles inland from downtown LA. Some things to consider: *The room they are most frequently in is an add-on to the house (probably not insulated properly) *The beetles seem to appear in the middle of the night/early in the morning (after 2am) *The beetle has wings and can fly Please help us identify this beetle and find some sort of method to prevent them from continuing to scare us! Thanks so much, can’t wait to hear back from you. Samantha Signature: ???
Eucalyptus Borer
Eucalyptus Borer
Hi Samantha, This is an invasive, exotic species commonly called a Eucalyptus Borer.  Do you have a wood burning stove or a fireplace?  Do you bring logs in to burn?  Did you bring eucalyptus logs into the house?  If the answer to those questions is yes, that explains the presence of the Eucalyptus Borers in your home.  If you do not burn wood, then perhaps there is an infested eucalyptus tree nearby and the Eucalyptus Borers are entering the room due to the poor insulation. Thank you so much for responding! You definitely helped me identify the problem. Now our living room is beetle-free! Have a great day 🙂 Samantha Vaisman

Letter 18 – Eucalyptus Longhorned Borer


Subject: Black & Yellow 2 inch Bug Location: Concord CA April 20, 2014 9:19 pm Should I be concerned about this bug? Or is it just a beetle? It is about two inches long with four inch antennae. The head is black. The body is mostly yellow from the head to the black band before getting to the yellow butt area. There are two symmetrically located black dots in the yellow area of its back. The legs and antennae appear to be brown. I found this bug on an exterior garage wall under a light on Sunday, April 20, 2014. We live in Concord, CA, about 35 miles east of San Francisco. It is starting to stay warm throughout the day (average of 70’s to 80’s). The weather is cool at night with dew in the morning, and dry/not humid during the day. The closest I could come to identifying it is calling an “Instable Longhorn beetle Judolia spp Family Cerambycidae” from the website address below: The attached photo was taken with my iPhone and emailed to me as “Actual” size. I’m not sure what to make of it. Any information you can provide will be greatly appreciated. Thank you, Raymond Winters Signature: Ray W. of Concord CA
Eucalyptus Longhorn
Eucalyptus Longhorn
Dear Ray, While you have misidentified this Longhorn Borer Beetle, you did get the family correct.  This is actually a Eucalyptus Longhorned Borer and it is an invasive species in Southern California, but luckily, its host tree is also an introduced genus, the Eucalyptus trees, which are ubiquitous in Southern California.  More information on Eucalyptus Longhorned Borers can be found on the UC Davis Statewide Integrated Pest Management Program website.

Letter 19 – Eucalyptus Borer from Australia


Subject: Unidentified flying object Location: Esperance, Western Australia March 5, 2017 11:50 am Insect has long antennae (about the same length of the body), 6 legs, about an inch long, made a highpitch squeaking noise when I put it in the container, can fly, wings seem to be sheltered like a beetles, body is black with a brown patch in the middle Signature: With an answer
Eucalyptus Borer
This is a Eucalyptus Borer, a species that has been accidentally introduced to California where it has a plentiful supply of food plants, but no natural enemies to control its populations.

Letter 20 – Eucalyptus Borer in Hawaii


Subject: Longicorn 9pm 1500′ Maui Location: 20n 156w Pukalani, Maui June 29, 2017 1:50 pm Aloha – This guy was unexpectedly found at 9pm the other night. The paint spot to the right is about 7/16″ in diameter. Longicorn was on its back when I first saw it, flipped over and started moving to the left. Attempted to fly away but didn’t succeed. It was not there when I checked a while later. Know it is hard to determine just what kind of longicorn it is from one photo. Rare for us to have any bug this size flying at night other than mating American cockroaches or Black Witch moths. Appreciate all your posts. I start my day looking over the bugs posted to learn more about insect life. Signature: Eliza
Eucalyptus Borer
Aloha Eliza, Thanks for your kind words.  Were there eucalyptus trees near the sighting?  This is a Eucalyptus Borer, and we have already received documentation that they are found in Hawaii.  They are covered briefly on page 11 of the Pests of Trees and Palms in Hawai’i article posted to Aloha Arborist. Aloha Daniel – Mahalo nui loa – thanks very much. Appreciate knowing what this critter is. Yes, upwind by about 1/4 mile or so, a stand of old eucalyptus is being removed. One had been laying on the ground for many years, when the leftover winds of a tropical storm knocked it down. Even tho’ it was supine, the tree still had green leaves. The neighboring shorter trees were standing till earlier this week. The pieces of trunk are in the field which gets grass/weed trimmed by goats. Who knows what their next step in their life gets to be. No doubt this borer got evicted suddenly from its home. Have a pleasant 4th of July holiday. A hui hou (until we meet again) – Eliza

Letter 21 – Eucalyptus Longhorn from Australia


Subject:  Can you identify this bug please Geographic location of the bug:  Ferny Creek, Melbourne Vic Date: 12/16/2018 Time: 12:04 AM EDT Your letter to the bugman:  Hi bug man, Just wondering if you can tell me what this bug was. It was So pretty…. How you want your letter signed:  Tammara
Eucalyptus Borer
Dear Tammara, While it appears to have met an unnatural end, your indication that “It was So pretty” causes us to speculate that you were not involved in this beetle’s demise.  Though it is an insect native to Australia, most of our images of Eucalyptus Borers are sent from Southern California where the beetle has naturalized because of an accidental introduction in about 1967.  There are many eucalyptus trees in Southern California, so when the Eucalyptus Borer was introduced, it had no trouble finding a food source.  According to Oz Animals:  “The larvae of the Eucalyptus Long-horned Borer attack Eucalypt trees. They mostly attack stressed or damaged trees. Evidence of borers includes holes in the bark and oozing fluid on trunk or branches. In severe cases foliage may wilt and limbs die back. They rarely kill healthy trees.”  Thankyou Daniel for your reply! We have lots of bugs in Ferny Creek, never spotted a live one. We are surrounded by eucalypts and messmates as we live on the Dandenong Ranges National Park. Thanks again for you time… I will keep an eye out for a living one .️ Tammara


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    Bugman aka Daniel Marlos has been identifying bugs since 1999. is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

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    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

12 thoughts on “Eucalyptus Longhorned Borer – The Garden Pest Extraordinaire”

  1. Oops… Phoracantha semipunctata would actually seem to be more fitting… The only difference that I can actually visibly see is at the top of the wings on P. semipunctata the dark region is more pronounced than with P. recurva. Sorry about the ranting once again, I just get vaguely irritated that Hawaii is constantly not included in bug identification guides for the U.S. Hawaii does have a site that will assist with identification of local flora and fauna (, but I actually prefer your site. I wasn’t upset with your site, so I really hope you didn’t take it as such. Your site was actually how I identified the beetle to begin with (should have just come here in the first place… lesson learned). Sorry if there are any grammatical errors, or typos, it is getting rather late here, but I just wanted to clear all that up. Oh and could those ants be pharaoh ants instead? I looked up the Argentine ant, and an eighth of an inch is a bit too big for those ants (the beetle was rather small, maybe half of an inch or so). I will try my best to get better macros of them, but they move rather quickly.

  2. I had a bug appear on the upper inner right arm that apparently tried to bore into me. I have searched and found on your site, what I believe to be, a Eucalyptus borer. I’m in Miami Florida and the county is attempting to kill off all the Eucalyptus trees. This bug left quit a wound but now, on the inner lower side of my right arm, I am getting an itchy rash directly below and in line with the wound. The bite happened 03/21/2012 and the rash just began about three days ago. You say the bugs are harmless but this one doesn’t seem to be and I’m wondering if there is actually an effect from such a bite/boring. Can you enlighten me? I still have the dead bug.

    Pete 02/26/2010

    • We are not qualified to diagnose skin conditions. The bite and the rash might not even be related. We would suggest seeking professional medical advice if you are concerned.

  3. we now have allot of these eucalyptus borers every time a night light is left on for a few minutes we get hundreds! Thanks to You Dwight Takemine and his brilliant notion of arranging the planting of twenty thousand acres of eucalyptus on the Hamakua coast of Hawaii.

  4. Hi Mate, just doing a bit of research, one of these just bit my hand, fairly painful & burning sensation.
    This is exactly the one in the photo as shown.

    Is this bug dangerous, poisonous or harmful?

    Thanks MIke

  5. Hi Mate, just doing a bit of research, one of these just bit my hand, fairly painful & burning sensation.
    This is exactly the one in the photo as shown.

    Is this bug dangerous, poisonous or harmful?

    Thanks MIke

  6. I live in the Bay Area and have now found 2 of these in my house! I also thought initially that it was a cockroach but due to the markings decided it wasn’t too. Why are they in my house and how do you get rid of them?

  7. Hi Amina,
    Hi what’s that bug Team,

    I have found the same bug at home. It came out of a hole that it made in my tv table. The table was brought from London about 5 years ago and the eggs were probably in it as I’ve never seen such a bug before. When it came out of one of the wholes, it was lethargic too. I don’t know why, maybe because of the first exposure to light. But anyways, I want to ask if there is anyway to stop them from spreading to the rest of the furniture or if there’s anyway I can kill them as they’re ruining the table with the holes they’re coming our from.

    The bug I saw looked exactly like this and the holes were about half a centimeter in diameter while the bug was about 2-3 cm tall.

    Looking forward to hearing from you.

    Kind Regards,


    • Dear Ahmed,
      Often times wood boring beetles emerge many years after something is created from the felled tree that was the home to the larva. Any beetles that emerge will not infest your furniture.


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