Root borers are notorious pests, but are they dangerous to humans? For example, is broad necked root borer poisonous? Let’s find out.
Seeing scary-looking black beetles at the base of your plants? Despite the appearance, it could be a very harmless root borer!
Black in color with a thick head and strong jaws in front, the Broad-necked Root Borer looks scary both as a larva and an adult.
However, they are not poisonous and cannot harm humans or pets.
Though the same cannot be said for plants. Infected trees can die if they’re young.
Even older, healthy trees can end up with weakened roots, making them liable to falling over.
What Is The Broad Necked Root Borer?
Their common habitat includes parts of North America, and they’re widely considered pests, both in larval and adult form.
They’re found all the way from Quebec in Canada, through North Carolina to Arkansas in the South.
They look quite similar to the Black Caterpillar Hunter but have a thicker neck which helps distinguish them.
What Does It Look Like?
The Prionus laticollis is dark brown to black in color with a hard body protected by an exoskeleton.
The underside or belly is yellow in color.
When compared to other longhorn beetles, the broad-necked root borer has a much thicker neck covered with spikes – giving them their name.
Female broad-necked root borers are almost twice the size of males, and this makes it impossible for them to fly, despite having wings.
Males are smaller in size and can fly.
Females also have a long thing, an ovipositor at the end, which helps them deposit eggs within the ground.
Both sexes have black mandibles, with the males having the larger ones that they use in territorial fights.
As with other beetles, the root borer is quite efficient at burrowing at the base of trees and shrubs – especially oak.
Are They Dangerous To Humans?
Despite their scary look, root borers are not poisonous. They cannot harm humans or pets – even if your pet happens to ingest them.
However, they do have strong burrowing mandibles which can deliver a strong bite.
While I don’t suggest it, you can pick them up gently and throw them away. The beetles do not usually bite unless they are attacked.
Do They Bite or Sting?
They cannot bite or sting. While the female might look like she has a sting – it is actually an ovipositor.
The ovipositor is a thin, needle-like organ that protrudes from the rear of the female.
This helps them to lay eggs deep within the ground. They then use the ovipositor to cover the eggs with more soil by moving them up and down.
Are They Poisonous/Venomous?
Root borers do not possess any venom. Hence, they are not poisonous.
Even if this beetle does end up biting you, you will only suffer from temporary local inflammation.
It is rare for them to attack or bite humans, as most of their aggression is reserved for other beetles.
What Is Their Lifecycle?
The female will generally lay clutches of eggs at the base of trees and shrubs.
Generally, each clutch contains groups of two to three eggs. After covering the eggs with soil again, both sexes leave.
The eggs turn from sharp white to pale yellow and eventually a washed-out shade of pink.
Finally, just before the larvae hatch, the eggs take on an ivory shade.
The larvae chew their way out through the egg and can be as large as 3.5 inches.
They have well-developed mandibles that they use to burrow out of the soil and feed on bark or soft, dead wood.
Eventually, they start burrowing through roots, damaging crops they come in contact with.
After this, the larvae enter into a pupal stage from which adult beetles emerge.
The adults feed on tree foliage and fruits. The entire process can take upto three years.
What Do Broad Necked Root Borers Eat?
Larvae start by feeding on softwood and eventually start eating the roots of a variety of trees – even those of older, larger plants.
Adults eat foliage, fruits, and dark and internal plant tissue.
Due to their voracious appetite, the broad-necked root borer is a huge pest for gardens and agricultural lands.
Some common fruit trees they attack are peaches, apples, grapes, and other deciduous softwood trees.
Where Do They Live?
Generally, the larvae can be found at the base of deciduous trees, where they feed on shoots and roots.
Adults also mostly hide within plant debris, at the base of shrubs, or within their food source.
Frequently Asked Questions
What does broad-necked root borer eat?
Its larvae feed on the roots of trees, such as maple, oak, and beech, as well as any other woody material.
Adult beetles eat the foliage and can cause extensive damage to vegetation. They have also been known to vector a number of diseases that further damage plants.
In order to control this species, it is important to plow deeply in order to reach their larvae so they can be destroyed by pesticides or biological control agents.
Do broad-necked root borers fly?
These beetles spend their life cycle below the soil, having very brief interactions with sunlight during adult emergence and mating activities.
By living in the ground, Broad-necked Root Borers are capable of causing severe damage to crops and trees.
They were among the first identified serious pests of sweet potatoes in North America and remain a major pest in some areas still today.
Do wood borers bite humans?
However, adult wood borers do have the capability to bite humans if one gets too close to the adults or attempts to handle them.
Therefore, it is important to be careful when dealing with wood materials that may have been infected with wood borers.
Additionally, the droppings of these pests can cause respiratory problems in humans if one is exposed to them for extended periods of time.
What is the best remedy against borers?
Prevention means regularly examining plants for signs of borer damage and removal of weakened or dead stems and branches, as these can act as a source of infestation.
If borers are found, promptly prune the stem or branch and twig several inches back past any visible signs or activity.
In some cases, spot treatments with insecticides may be necessary for severe infestations.
Finally, keep irrigation up-to-date to keep plants healthy; this reduces their susceptibility to borer attacks.
While one can use insecticide to get rid of them, it’s best to prevent their growth itself by keeping your plant base clean and debris-free.
This will give them less shelter and egg-laying zones and make them more visible to possible predators.
Another alternative is to paint the bottom 2 feet of trees with latex paint.
If you have an infestation, it’s best to consult degreed professionals for help. Thank you for reading.
The broad-necked root borer is a rather scary-looking bug, so it is no surprise that many are intimidated by seeing it.
Here are a few letters from our readers asking us to identify it and to check whether the insect is dangerous.
Letter 1 – Broad Necked Root Borer
Broad Necked Root Borer
My Boy Scouts and I found this insect outside my tent at Ockanickon Scout Reservation near Pipersville, Pennsylvania last week (07/08). It was about 2 inches long and what was fascinating was that it appeared to take a defensive posture and extended its “stinger” (propably not the right term but I am rather insect identification challenged!) I found your website and went through the beetle sections. I think it’s a Broad Necked Root Borer, but didn’t see any with the “stinger”. Your opinion, and an explanation of the “stinger” would be greatly appreciated and educational for the Scouts. This is an awesome website! Thank you,
Your Broad Necked Root Borer, Prionus laticollis, is a female, and the stinger is her ovipositor. She needs a means by which to deposit her eggs deep inside the wood.
Letter 2 – Broad Necked Root Borer
Black beetle found in SE PEnnsylvania
Sat, Jun 27, 2009 at 3:35 PM
Can you please help us identify this beetle we found in our gravel driveway in Bucks County, PA? It’s 2″ long from front to back and appears to have wings.
Bucks County, Pennsylvania (SE PA)
Your beetle is a Broad Necked Root Borer, Prionus laticollis. According to BugGuide: “Adults eat foliage, sometimes damage fruit trees, grape vines. Life Cycle Eggs are inserted into ground (or under litter) in groups. Larvae tunnel downward to feed on living roots of a variety of trees and shrubs. At first they may feed on bark, but then proceed to hollow out small roots. Pupation occurs in spring, about 10 cm under the ground. Life cycle probably three years. “
Letter 3 – Broad Necked Root Borer
Sun, Jun 28, 2009 at 1:01 PM
Super huge beetle (at least for the northeast), swollen-looking yellow belly (mama beetle, maybe?), periodically leans forward completely on its head and projects this bizarre pointed appendage from its backside….very weird. I’ve never seen anything like this.
Your female beetle is a Broad Necked Root Borer, Prionus laticollis, and the appendage is her ovipositor which she uses to deposit her eggs. According to BugGuide: “Eggs are inserted into ground (or under litter) in groups. Larvae tunnel downward to feed on living roots of a variety of trees and shrubs. At first they may feed on bark, but then proceed to hollow out small roots. Pupation occurs in spring, about 10 cm under the ground. Life cycle probably three years.”
Letter 4 – Broad Necked Root Borer
July 11, 2010
What is this bug? It was on the side of my house July 10, 2010 on a nice warm night when I went out to take pictures of a beautiful rainbow.
We have received many identification requests for Broad Necked Root Borers, Prionus laticollis, recently, and we have posted many of the photos. They have all been of females with ovipositors visible. Your beetle is a male of the species. The males have much more pronounced antennae.
Letter 5 – Broad Necked Root Borer
Large, Fat Beetle in SE Virginia
Location: SE Virginia
June 26, 2011 8:30 am
Greetings. I found a large beetle in the yard today. It had good sized mandibles, was big and fat. Maybe it’s a female? It had some kind of white froth (bubbles) oozing out its sides and on it’s legs. If I touched it, it would spin around, jump up on its legs and flare it’s mandibles. Most beetles I’ve seen around here are flat, but this one was big and fat. We live near a wooded area. I release it back into the woods. Pictures enclosed. Thanks!
This is a female Broad Necked Root Borer, Prionus laticollis. The males are slightly smaller and more active and have spectacular antennae. See BugGuide for additional information.
Letter 6 – Broad-Necked Root Borer
Need help with a large bug
Location: Pittsburgh, PA
June 27, 2011 8:45 am
I have two small kids and this bug is a giant. Never seen anything like it in PA before. (Pittsburgh, PA, 6/26/11, Early Summer)
We have some damage to our trees too, wondering if this guy is the culprit. Any help is appreciated
Signature: Jeff Schroeffel
We have recently received numerous requests to identify the Broad-Necked Root Borer, Prionus laticollis, the insect in your photograph. We even posted a photo of a female Broad-Necked Root Borer over the weekend. Your individual is also a female also, and we are posting your image because it illustrates the ovipositor, the stingerlike appendage protruding from the rear end of the beetles abdomen. Here is the BugGuide description of the egg laying process: “Eggs are inserted into ground (or under litter) in groups. Larvae tunnel downward to feed on living roots of a variety of trees and shrubs. At first they may feed on bark, but then proceed to hollow out small roots. Pupation occurs in spring, about 10 cm under the ground. Life cycle probably three years.”
Letter 7 – Bug of the Month July 2011: Broad-Necked Root Borer
Ed. Note: We have never made any of the Prionid Beetles a Bug of the Month, and summer is the season for the various species from coast to coast. California has the California Prionus and the Eastern states have the Broad Necked Root Borer. Many Prionids exhibit distinct sexual dimorphism, with the smaller males having more pronounced antennae. Many females are practically or totally flightless, and males are attracted to lights at night. Here is a recent letter.
Large beetle in NY
Location: Long Island, New York, USA
June 28, 2011 5:48 pm
I don’t think I’ve seen a bug this big in New York before. It’s slowly walking around my sidewalk and sticking its butt up in the air like this, with a yellow thing that is protruding and retracting.
Your insect is a female Broad-Necked Root Borer, Prionus laticollis, and the yellow thing is her ovipositor which is used to lay eggs. According to BugGuide: “Eggs are inserted into ground (or under litter) in groups. Larvae tunnel downward to feed on living roots of a variety of trees and shrubs. At first they may feed on bark, but then proceed to hollow out small roots.”
Letter 8 – Broad Necked Root Borer
Location: Clinton, Beaver County, Western PA
July 25, 2011 8:45 pm
I was driving home from my Mum’s place on the 4th of July and saw what I thought was a mouse or mole or even bat crossing the road ahead of me. I drove over/above them slowly and carefully, then stopped, parked and put on my flashers to go get a better look. What I found was a GIANT BUG! I’d never seen a beetle so big before!
Now, I love bugs, so I was too excited for words! I ran back to my car and got my phone and got the two photos below.
I posted these on Tumblr earlier this month and my bug friends there say I found a broad-necked root borer.
I’m mainly sharing these pictures here because I’ve read so many sad stories on your Unnecessary Carnage page that I wanted to give you a happy story to post.
Sorry for the not-too-great quality of my pictures.
Signature: Toby Oaden
Thanks so much for thinking to send in your photo of a Broad Necked Root Borer, our Bug of the Month, and also you kind gesture to give us a happy story to post.
Letter 9 – Male Broad-Necked Root Borer
Prionus beetle in Connecticut
Location: Mill Pond Park, 864 Willard Avenue, Newington, CT 06111
July 5, 2011 5:22 pm
About 1 week ago, I captured a black beetle, about 2 inches long, in Mill Pond Park, Newington, Connecticut. (Mill Pond Park, 864 Willard Avenue, Newington, CT 06111).
The beetle was actually flying near the pond, trying to escape a house sparrow that was attacking it. The sparrow flew away and I went to see what the bug was. I captured the beetle as it tried to dig into the grass. The beetle had minimal damage, apparently from the sparrow. After I photographed and released it, it flew off into the bushes bordering the pond.
An entomologist I know who works at UConn said she guessed it was a Prionus sp. I’m just curious what species.
Signature: Chris Dubey
This year, most of the images we received of Broad Necked Root Borer, Prionus laticollis, have been females. Thank you for supplying us with a new photo of a male who can be distinguished by his antennae. Your first hand observations of the sparrow attack is a great addition to our archive of information.
Letter 10 – Male Broad Necked Root Borer
HUGE Black Beetle in New Jersey
Location: Southern New Jersey, near pine barrens
July 7, 2011 9:58 pm
We found this beetle outside tonight and were amazed at his size! We’ve never seen a beetle that looked anything like this one and are curious to know more about it.
Signature: RD in NJ
The quantity of requests we received in late June to identify the Broad Necked Root Borer, Prionus laticollis, prompted us to name it Bug of the Month for July. Most of our submissions this year were of females whose antennae are not as developed. It is nice to get your photo of a male Broad Necked Root Borer. Stay clear of the mandibles as they are quite powerful. Though the species is not aggressive, it may bite if it is threatened or carelessly handled.
Letter 11 – Male Broad-Necked Root Borer
Subject: what’s this bug?
Location: Hamilton Massachusetts
July 12, 2013 7:45 pm
Hi there my name is Robert and I work in Hamilton Ma and came across this interesting insect, and am wondering if u can help identify it. Thank you so much, Robert Vacirca
Signature: Robert Vacirca
This is a Broad-Necked Root Borer, Prionus laticollis, and we have gotten numerous reports from Eastern states in the past few weeks. Your individual is a male Broad-Necked Root Borer which can be recognized by his more developed antennae.
Letter 12 – Male Broad Necked Root Borer
Subject: Mystery prionid on Cape Cod
Location: Eastham, Massachusetts
September 6, 2016 3:37 pm
We found several of these beetles at our rental house this summer in Eastham, MA. The ones we saw were in the 2″ range and came out at night – they appeared to be attracted to our porch light. The days we were seeing them were the first week of August but I don’t know how long before or after they were around. They look to be some form of prionid beetle but I am unsure as to species.
This looks to us like a male Broad-Necked Root Borer, Prionus laticollis, and according to BugGuide: “Pronotum as broad, or almost as broad, as base of elytra. Very dark. Elytra have irregular punctures, and each elytron has three indistinct longitudinal ridges. Pronotum has three blunt lateral teeth on each side. Antennae have 12-13 segments. Female much larger than male. The former is reported to be flightless, or nearly so. Males are attracted to lights.”
Letter 13 – Male Broad-Necked Root Borer
Subject: What Bug is this
July 14, 2017 8:26 pm
This big bug was on our door frame. We’re in south central Pennsylvania on a Muggy evening in July. It was about 1 1/2 to 2 inch long. What is it
This is a Longhorned Borer Beetle in the subfamily Prioninae, and we believe it is a male Broad-Necked Root Borer, Prionus laticollis. We have received several images of female Broad-Necked Root Borers with exposed ovipositors this year, but your image is the first of a male Broadnecked Root Borer we have received this season. The male has more developed antennae so that he can sense the location of the female who releases pheromones.
Letter 14 – Male Broad-Necked Root Borer
Geographic location of the bug: Eastern New York – Suffolk County
Time: 08:54 PM EDT
Your letter to the bugman: Hello! This critter was hanging out on my front door. After looking at some pictures online my wife and I think it is a Broad Necked Root Boarer, but we are not sure. Can you confirm or correct?
How you want your letter signed: I don’t understand what this means
We agree that this is a male Broad-Necked Root Borer.