Are Acorn Weevils Harmful to Humans? Uncovering the Truth

Acorn weevils are small insects with distinct long snouts, which they use to infest various oak tree acorns. The weevil larvae live inside acorns to eat the developing tissue. But, they don’t typically pose a direct threat to health.

Despite not being harmful to humans, acorn weevils can indirectly impact our lives by affecting oak tree growth and health.

For instance, heavy weevil infestations can lead to acorns losing their ability to germinate and grow into new trees. This can have a detrimental effect on the tree population and the ecosystem that depends on them.

In some cases, it may even impact industries that rely on oak trees, such as lumber and furniture production.

Are Acorn Weevils Harmful to Humans

Bite and Stings

Acorn weevils are small insects, measuring about 3/8 inches in length. Their bites and stings are not common occurrences, mainly because:

• Weevils have no reason to attack humans
• Their size makes it difficult to bite or sting a person

Poisonous or Not

When evaluating the harm acorn weevils may cause to humans, it is essential to know whether they are poisonous or not. To clarify:

• Acorn weevils are not poisonous to humans
• Their larvae feed on acorns, which may cause damage to trees

Acorn Weevils and Their Life Cycle

Eggs

Acorn weevils begin their life cycle as eggs. Female acorn weevils use the snout to bore a hole and lay their eggs in developing acorns, which then serve as a food source for the larvae once they hatch.

Larvae, and Grubs

The larvae, also known as grubs, are legless and creamy white, with a brown head. They have a curved body that’s fattest in the middle and tapers toward both ends.

As they grow, the grubs feed on the nutmeats within the acorns, which provides them with the necessary nutrients to develop further.

Adult Acorn Weevils

Adult acorn weevils are brown beetles, approximately 3/8 inches in length, with a very long, thin snout called a rostrum.

This distinctive feature is used by females to bore tiny holes into developing acorns, allowing them to lay their eggs in a safe and nutrient-rich environment.

Oak Trees and Acorn Weevils

Oak trees play a significant role in the life cycle of acorn weevils. Oaktree acorns provide an ideal oviposition site and food source for the developing grubs.

Weevils belonging to the genus Curculio have been known to infest various oak species, including bur, pin, and red oaks.

Life cycle stages of acorn weevils on oak trees:

1. Female weevil lays eggs in developing acorns
2. Grubs hatch from eggs and consume acorn nutmeats
3. Grubs reach maturity and bore out of the acorns
4. Mature grubs pupate and transform into adult weevils
5. New adult acorn weevils infest more oak trees in midsummer

Stage	Location	Food Source
Eggs	Oaktree acorns	N/A
Grubs (Larvae)	Inside acorns	Acorn nutmeats
Pupae	In soil	N/A
Adult Weevils	On oak trees	Acorns

Acorn weevils are not known to be harmful to humans, but they can cause damage to oak trees by affecting the quality and quantity of their acorns.

However, they play a vital role in the ecosystem by helping to control the oak tree population and providing food for larger predators.

Damage and Threat to Trees

Acorn Damage

Acorn weevils, specifically the Curculio species, are known to cause damage to acorns of various oak trees.

The adult acorn weevils have a long, slender snout called a rostrum, which female weevils use to puncture acorns and lay their eggs inside. Once the eggs hatch, the legless larvae feed on the acorn’s interior.

• Damage: Reduction in viable acorn production
• Example: Curculio glandium infesting oak tree acorns

Tree Disease and Infestations

Although acorn weevils may not directly harm the tree itself, they can contribute to the spread of diseases and infestations within the tree.

When an acorn weevil punctures an acorn to lay eggs, it creates entry points for pathogens, potentially leading to tree disease and other pest infestations.

Comparison table:

Acorn Damage	Tree Disease & Infestations
Direct acorn damage	Indirect damage to tree
Caused by adult weevils	Result of weevil activity
Reduction in viable acorns	Increase in potential pests

Controlling Acorn Weevils

Insecticides and Natural Control

When attempting to control acorn weevils, insecticides may be considered an option. Here are a few advantages and disadvantages of using insecticides:

Pros:

• Effective in eliminating weevils
• Quick results

Cons:

• Potential harm to non-target species
• Some insecticides might not be eco-friendly

For natural control methods, you can:

• Introduce predatory insects, such as birds and ladybugs
• Remove infested acorns in the early stages
• Use horticultural oil

Prevention and Management

The key to managing acorn weevils is prevention. Here are some tips:

• Regularly inspect oak trees for signs of infestation
• Remove fallen acorns promptly
• Encourage natural predators by providing nesting sites

	Insecticides	Natural Control	Prevention and Management
Effectiveness	High	Moderate	Variable
Speed	Fast	Slower	Long-term
Eco-friendliness	Can vary	High	High
Ease of use	Moderate	Moderate	Easy

Considering the potential harms of insecticides and the benefits of eco-friendly alternatives, natural control, and prevention methods are often preferred for controlling acorn weevils in residential areas.

Acorns and Their Nutritional Value

Edible or Not

Acorns are indeed edible for humans. However, they should be properly processed before consumption, as raw acorns contain high levels of tannins.

Health Benefits

Acorns provide various health benefits, being a good source of:

• Protein: Essential for muscle and tissue growth and repair.
• Minerals: Acorns are rich in iron, magnesium, and other essential minerals.
• Vitamins: They contain a variety of vitamins, contributing to overall health.

Drawbacks

Despite these benefits, there are some drawbacks to consider:

• Tannins: High levels of tannins in raw acorns can cause digestive issues and limit nutrient absorption. Proper processing, like leaching, can reduce tannin levels.
• Acorn Weevils: These insects can infest acorns, but they don’t pose a threat to humans. Ensure only healthy, weevil-free acorns are consumed.

Here’s a comparison table for acorn nutritional content:

Nutrient	Amount
Protein	Moderate
Minerals	Rich
Vitamins	Varied

Additional Information

Related Weevils

Acorn weevils are just one type of weevil species. Some other related weevils include:

• Boll weevil: attacks cotton crops
• Flour weevil: infests stored flour and grains
• Black vine weevil: damages ornamental plants

These weevils differ from acorn weevils in their preferred food sources and the level of harm they pose to humans and agriculture.

Weevil	Food Source	Impact on Humans/Agriculture
Acorn Weevil	Acorns (oak tree seeds)	Minimal
Boll Weevil	Cotton crops	Significant (crop damage)
Flour Weevil	Stored flour and grains	Moderate (food contamination)
Black Vine Weevil	Ornamental plants	Minimal to Moderate

Acorn Weevils and Squirrels

Acorn weevils and squirrels both rely on acorns as a major food source. Here’s what happens when these two interact:

• Acorn weevils lay their eggs in acorns, and their larvae consume the nutmeat
• Squirrels eat acorns and may discard those infested by weevil larvae
• Some squirrels may eat weevil larvae as a protein source

In essence, squirrels may help limit acorn weevil populations by consuming their larvae, while acorn weevils may inadvertently provide squirrels with an additional food source.

Are Acorn Weevils Harmful to Humans?

There is no evidence that acorn weevils cause direct harm to humans. They don’t carry diseases or inflict bodily harm, and their infestations are mainly limited to tree nuts like acorns and hickory nuts.

While they don’t cause any known health problems, they may impact the food supply for animals, such as squirrels and other creatures that depend on nuts for sustenance.

Conclusion

Acorn weevils may not be directly harmful to humans, but their presence can indirectly affect the environment.

These tiny creatures control the oak tree populations by infesting acorns. This can heavily impact the ecosystem and industries relying on oak trees.

Thankfully, the insects do not sting or bite humans. You can use insecticides to get rid of these insects, but they can have some harmful side effects.

Try to use the natural remedies mentioned in the article to control the weevil population.
Thank you, for taking the time to read the article.

Readers’ Mail

Over the years, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Unknown Elongated Weevil from Key Largo is Straight Snouted Weevil

Strange Weevil?
Hi Bugman,
Great site, I’ve been able to identify all the strange, cool bugs I find on your site until this one. I live in Key Largo, Florida in a hardwood hammock. Today this guy was on the coping of the pool.

He measures a little over an inch, the pictures are deceiving. It’s the first time I have seen anything like it. Thought it was a beetle but seems to be a weevil. The only weevil that even remotely looked like it is the New Zealand giraffe weevil.

Not to be confused with the Madagascar giraffe weevil. I know we have a lot of exotic creatures in Florida and I don’t think this one is a native. Thanks for your help and keep up the good work!!

Ian

Hi Ian,
We are not having much luck with identifying your Weevil. We suspect it is a tropical species. We will contact Eric Eaton for assistance.

Daniel
The weevil is a straight-snouted weevil in the family Brentidae. They are mostly tropical, with only a handful of species in North America north of Mexico. They are most often found under bark on logs and trees.
Eric

Update: (04/14/2008) Identified!Unknown Elongated Weevil from Key Largo
Looks like: Brentus anchorage. Found that link by searching for this name of a website in French. (at least those 4 years served for something). Looks similar.
Amber Lucas

Letter 2 – Brazilian Weevil is Diamond Beetle

Gorgeous Beetle from Rio de Janeiro
We spotted this gorgeous shiny green beetle walking along the stone walls around the base of the statue of Christ the Redeemer at Corcovado in Rio de Janeiro in November 2005.

When I saw his twin in the British mini-series “Wives and Daughters” this evening (preserved as a specimen being viewed by one of the characters), I found your site, but I didn’t see any beetles who looked like him.

He was about 1.5 inches long. Can you identify him?

Best regards,
Debbie Schilling
Indianapolis

Hi Debbie,
This is a species of Weevil, a beetle in the family Curculionidae. We found an unidentified specimen photo on the BugManiac online store that looks very similar.

Update: Wed, Feb 25, 2009 at 9:18 AM
Re: Unknown Brazilian Weevil – January 25th, 2008
Hi Daniel:
The blue/green striped weevil posted by Debbie Schilling, and referred to in the recent blue Brazilian weevil posting, is probably in the genus Entimus (Curculionidae : Entiminae).

It’s a relatively small neotropical genus with fewer than a dozen species, but all are notable for their incredible luster and brilliance.

The largest of the group, E. imperialis, is sometimes called the Diamond Beetle and has long been used as an item of jewelry by regional native peoples.

I can’t be certain about the species but from what I can tell E. nobilis seems to be the closest match. As a group, these weevils are apparently quite common in Brazil and they are popular among collectors, so it is a little surprising that good online photos are difficult to find.

Regards.
Karl

Letter 3 – Unknown Australian Weevil

gday bugpeople…
i know you are very busy, but, I looked at this creature and have no idea what to make of it… I found these two, very well camouflaged on a fallen and decaying hoop pine body in Lamington National Park, Australia.

I don’t remember if they were actually under the bark or not if it makes a difference, but anyway- they weren’t burrowed in there when i found them. they were about 1.5cm long maybe.

They sort of remind me of some sesame street character. not sure which one. i hope you’ve got something on them… thankyou…
Jenni
ps… you’ve got very interesting heads… an art project??

Hi Jenni,
We searched for a bit to try to identify your Weevil species but without success. We did find an Australian Weevil website, but no match to your photos is posted on it. The best we could do is Weevil in superfamily Curculionoidea.

Letter 4 – Unidentified Orange Weevil from Thailand

a giant orange weevil?
Hi folks! I really like the website. Bugs are neat creatures. I don’t know if you’ll be able to help me out with this one, but it’s worth a shot. My friend and I found this bug in the forest of northern Thailand.

It had pretty sharp little toes and looks like a giant weevil. I can’t figure anything else out, though. I looked at the Thai bugs website and it wasn’t there as far as I saw. Help!

Thanks,
Bonnie

Hi Bonnie,
This is a Weevil, but we don’t know the species. Once we catch up on the unanswered mail, we will try to identify the species.

Letter 5 – Unknown Australian Weevil

A weevil-looking beetle with a horny back
Hi. I looked through all your beetles and I think this one must be a “gorgojo” a type of Weevil from the family Curculionidae. I found it in my wheelie bin in the backyard. Atherton, Queensland, Australia, in the middle of the day.

If you ever have time, can you let me know for sure? I see them from time to time. Pretty darn cute ( but I still don’t want to touch it!) Thanks, much appreciated,
Susan.

Hi Susan,
This is a Weevil, but we do not know the species.

Letter 6 – Unidentified Weevil on a Porcelain Spitoon

A kind of weevil painted on porcelain?
Fri, Dec 19, 2008 at 9:20 AM
I’m trying to identify some of the various insects on some unusual porcelain from the Netherlands – specifically, what is the weevil-like beetle on the spittoon? It would have been decorated around 1775.

What 18th-century literature that included weevils would have been available to decorators at the time? An American living in Germany
C Jacob-Hanson
Holland

Hi C Jacob-Hanson,
We wish we had an answer for you, but we think you need an expert archivist on this.  Maria Sibylla Merian was one of the foremost insect illustrators of the 16th and 17th centuries, but she was mostly illustrating caterpillars, moths, and butterflies. 

You might try contacting an art historian like Stephanie Schrader at the Getty.

Letter 7 – Unknown Costa Rican Weevil maybe Green Immigrant Leaf Weevil

Wood-carved and glittered weevil
July 13, 2009
Hi Bugman-
I recently went to Costa Rica for my honeymoon (6/21-6/28) and came back with tons of pictures…of insects. I thought I’d share these pictures of a weevil I saw one night climbing up a wall.

We were on our way to dinner, camera in tow, when out of the corner of my eye I saw a glittering green, gingerly moving splotch. Upon closer inspection, I noticed that it was a beetle.

This little dude looks like someone carved him out of wood and then had their child sprinkle a spring shade of glitter all over his back. He didn’t want to stay too still but decided that he’d pose for a couple of shots…hope you like him.

insect fan
Costa Verde, Manuel Antonio, Costa Rica

 

Dear insect fan,
We are a bit stumped by your weevil, and we hope one of our readers will be able to assist in the identification.  It really does look like it has been embellished with glitter. 

We do know that in certain places in Central America, insects are used as living jewelry.  Sometimes beautiful insects are just affixed to small chains and pinned to clothing. 

Other times insects may be painted or bejeweled. This image does almost look too “glittery” to be natural.

Update
Unknown weevil Costa Rica
July 17, 2009
Hi WTB!!
I have a photo of a weevil as my screensaver that looks a lot like the glittery weevil you are having trouble identifying. I took the photo from one of your reader’s websites.

You can view more photos of the weevil there. Father Sanchez has it listed as Polydrusus and he is located in Puerto Rico. 
Keep up the great work!
Andrea with the anatomically correct butterfly tattoos 🙂 Hollywood, CA
Puerto Rico

Hi Andrea,
How nice to hear from you again.  We have also had email exchanges with Father Sanchez.  We love his website.  We are linking to BugGuide’s page on the Green Immigrant Leaf Weevil, a European species that has naturalized in North America.

  Though we are inclined to agree that this weevil and our Costa Rican Weevil look the same, we would really like to get an expert opinion on that.  Thanks so much for providing this information.

Update from Karl
August 6, 2009
Catching up on weevils (3 in 1 – sorry about that)
Hi Daniel:
The first part of this is just FYI – a great internet resource. I found a little time to go back and catch up on some wonderful weevils that caught my attention as they were posted. 

One of my favorite resources for this sort of thing is the digitized version of the Biologia Centrali-Americana (58 volumes!). It is a little difficult to navigate through, but what an incredible storehouse of information!

The volumes on insects were originally produced between 1879-1915, but they still stand up as an incredible body of work. The two Costa Rican weevils were identified from this site. Cheers.  K

Daniel:
The Green Immigrant Leaf Weevil (Polydrusus sericeus) is a relatively tiny (5-7 mm) weevil accidentally introduced from Europe. Although it has become widespread in North America (I have seen quite a few this year on the Canadian prairies), I don’t know if it has made it as far south as Costa Rica.

I think this gorgeous creature is actually in the genus Exophthalmus (a reference to those big, bugged-out eyes?), and the species is probably E. carneipes (Curculionidae: Entiminae). 

At 9-12 mm it is roughly twice as large and could certainly catch someone’s attention climbing up a wall. I couldn’t find out much about the species, other than that it occurs in Costa Rica and Panama.

A great find and a very nice photo from an “insect fan”.  There is another very nice image of the same (unidentified) weevil here.
Regards.
Karl

Letter 8 – Unknown Mating Weevils from Viet Nam

Good Old Fashioned Weevil Lovin’
February 23, 2010
I found these guys on a day hike at Cuc Phuong National Park in Vietnam. It was around May 13th and the rainy season had not quite started yet.
Danielle
Vietnam, Cuc Phuong National Park

 

Hi Danielle,
We will attempt to identify these Weevils.  Can you tell us how large they were?

Letter 9 – Unidentified Weevil from Peru

Blue mystery bug from Peru
February 27, 2010
My son spotted this bug while we were out on a nature walk. It is bright blue. While I’ve spent several hours searching your site for something similar, all I’ve found is the masked hunter (but I doubt it is this because there was absolutely nothing this color anywhere near where we were… no blue carpet :).

It is similar in color to the blue-green citrus weevil, but its body doesn’t look like it as it’s rather bumpy. Just thought it’d be fun to identify it, though I didn’t imagine it would be this hard… 🙂

He was about 2cm in length and was crossing a dirt road near a farm of coconut trees. We live in ceja de selva (which is on the eastern slopes of the Andes, above true rainforest level).

Amy in Peru
Tarapoto, Peru

 

Hi Amy,
This is a Weevil.  Alas, we haven’t had the time to research the species at the moment, but perhaps one of our readers will be able to identify the species.

thank you for getting back to me!  I have a request for a name in case it hasn’t been officially recognized…
my kids would like to call it the ‘turquoise blue tuttle beetle’… of course now that we know that it’s a weevil…
maybe it should be the ‘not-at-all-evil-blue-tuttle-weevil’ 🙂
anyway, thanks again 🙂
amy in Peru

Hi, again Amy,
You should post a comment to this posting to be informed automatically in the future of identification.

Letter 10 – Unknown Weevil from Brazil

A proboscis with an antenna?
Location: Cambé – PR, Brazil
January 8, 2011, 7:39 pm
It was found on a growing pit of one of my Nepenthes (the brown, not the green one). With 1cm. Photo – iPhone4 with a magnifying glass and patience.
Thank you for your time.
Signature: Aloysio Paschoal

 

Dear Aloysio,
This is a species of Weevil in the superfamily Curculionoidea.  Weevils are the most plentiful beetles on the planet.  We will attempt a species identification for you and perhaps one of our readers will be successful in identifying this tiny Weevil.

Thank you very much.
And I was here, thinking that maybe it could be a rare species.
Aloysio

Hello, again Aloysio,
It may be a rare specimen, but we couldn’t say for sure until the species is identified.

Letter 11 – Possibly Golden-Headed Weevil from Alabama

Subject: mystery bug
Location: Unknown
February 15, 2016, 5:26 pm
I work at a grocery store. This bug was found on a door near where we were unpacking plants for the floral department today. We get flowers from Florida, Mexico, Costa Rica, and locally (Alabama), and some boxes aren’t labeled.

We aren’t sure where he came from or what box he got out of. Sorry, we couldn’t be more help.
Signature: Rachel from Winn-Dixie

 

Dear Rachel,
This is a species of Weevil in the superfamily Curculionoidea and we believe it is a Broad Nosed Weevil in the subfamily Entiminae which is well represented on BugGuide, a site that is devoted to North American sightings. 

We do not believe this is a native species, but we are not certain.  We will contact Eric Eaton for a second opinion, but since flowers may come from many parts of the world, including Columbia and Australia, it may be difficult to get a conclusive ID. 

We are going to tag this posting as an Invasive Exotic until we learn otherwise.

Eric Eaton Concurs
Daniel:
I would agree that this is probably a foreign species, maybe in the genus Compsus, but I can’t be positive.  As a result, I don’t have any links to provide, either.
Eric

Letter 12 – Unknown Weevil from Brazil is Odontopus sp.

Subject: Brazilian weevil
Location: Brazil
January 13, 2017, 3:43 pm
Greetings, I found this weevil in a batch of unidentified specimens collected back in the 1970s and deposited in the North Dakota State University insect collection. I don’t even have a clue where this fits taxonomically in the weevils….any help would be greatly appreciated
Signature: Guy A. Hanley

 

Dear Guy,
This Weevil looks very familiar to us, yet we have not had any luck searching the internet.  We are posting your image and perhaps one of our readers, Cesar Crash perhaps, may be able to provide some assistance.

Hello Daniel and Guy:

This is a very interesting-looking weevil. Try checking out Odontopus sp.  Regards, Karl

Thanks, Karl.  The images on Entomofauna Guyane look like a match to us.

A Facebook Comment from Tina:
I am thinking possibly in the genus Odontopus… A few links to other specimens in the genus that are similar, however, I couldn’t find an exact match.

http://entomofauna-guyane.fr/?q=image/3143-gen-sp75/images/113-curculionoidae

http://entomofauna-guyane.fr/?q=image/3229-curculionidae-gen-sp80/images/113-curculionoidae

http://entomofauna-guyane.fr/?q=image/4777-odontopus-sp81/images/113-curculionoidae

Letter 13 – Unknown Mating Weevils from Costa Rica

Subject:  weevils in the rainforest
The geographic location of the bug:  Rio Celeste de Upala near Rincon de la Vieja, Guanacaste,CR
Date: 06/12/2018
Time: 10:16 AM EDT
Your letter to the Bugman:  Please help me to identify these weevils, they were very interesting in texture and I can’t find them in INBIO or anything else.
Thank you in advance
How you want your letter signed:  Weevils from Rio Celeste de Upala

 

Like you, we have not had any luck determining a species identity for these mating Weevils. 

We did locate an image at the very bottom of the Homestead Brooklyn blog page devoted to Tapanti National Park which is unidentified and another similar-looking individual from Selva Verde, Costa Rica that is unidentified on Alamy. 

The Costa Rica Research page of the Microbiology at Occidental College site also has a similar-looking unidentified Weevil on it.  Finally, we located your image on Jungle Dragon.  Perhaps one of our readers will have better luck than we have had.

 

Thank you for your help!
It is always very tricky to identify CR insects.  There are no books and no good websites, only those meant for biological warfare identify ‘plagas’ or pests..
With best wishes
Annette