Cottonwood borers are a common pest that can cause significant damage to trees such as cottonwood, poplar, and willow. These large black and white longhorned beetles lay their eggs at the base of host plants, and when the larvae hatch, they tunnel around the crown and buttress roots of the trees, causing serious harm.
Getting rid of cottonwood borers is crucial for the health and longevity of your trees. In this article, we’ll discuss methods to control and prevent these pests, ensuring your trees remain vigorous and pest-free. Stay tuned for practical tips and solutions to tackle this gardening challenge.
Understanding Cottonwood Borer
The cottonwood borer (Plectrodera scalator) is a member of the longhorned beetle family, Cerambycidae. Its life cycle consists of four stages:
- Eggs: Females lay eggs in niches they cut into the bark at the tree base.
- Larvae: Creamy white grub-like larvae tunnel around the crown and roots.
- Pupa: The larva develops into a pupa inside the tree.
- Adult: Mature beetles emerge in late spring or early summer.
Cottonwood borers mainly infest cottonwood, poplar, and willow trees. Their feeding and tunneling activity usually occurs at or below the soil line.
Here are some physical characteristics of the cottonwood borer:
- Size: Adults typically measure 1.25 to 1.5 inches in length.
- Color: They have a distinctive black and white pattern on their bodies.
- Antennae: Long, black antennae are a notable feature of this beetle.
Comparison Table: Cottonwood Borer vs. Other Longhorned Beetles
|Feature||Cottonwood Borer (Plectrodera scalator)||Locust Borer (Megacyllene robiniae)||Red-Headed Ash Borer (Neoclytus acuminatus)|
|Length||1.25 – 1.5 inches||0.75 – 1 inch||0.5 – 0.75 inch|
|Primary Color||Black and white||Black and yellow||Reddish-brown|
|Key Host Trees||Cottonwood, poplar, willow||Black locust||Ash, oak, hickory|
|Antennae Length||Nearly as long as body||Body length||Shorter than body length|
|Larval Appearance||Creamy white, grub-like||White, legless||Creamy white, cylindrical|
Pros of the cottonwood borer:
- Occupies a specific ecological niche within its host trees.
Cons of the cottonwood borer:
- Weakens and damages the structural integrity of the host trees.
- Can cause decline or death of young or infested trees.
Signs of Infestation
One common sign of a cottonwood borer infestation is the presence of frass, a mixture of chewed wood and insect excrement, around the base of the tree or near trunk and branches. Adult borers may leave tiny holes on the trunks and branches, while larvae can create galleries or tunnels within the tree, weakening its structure.
Flagging, or wilting of leaves, is another sign of a potential infestation as it indicates the disruption of water and nutrient transportation within the tree due to larvae damage.
Commonly Affected Trees
Cottonwood borers often target trees like:
Here’s a comparison table of the trees affected by cottonwood borers:
|Tree Type||Susceptibility to Infestation||Additional Info|
|Cottonwood||High||Most commonly targeted by cottonwood borers|
|Poplar||Moderate||Second most common target|
|Willow||Moderate||Less susceptible than cottonwood & poplar|
To prevent infestations, adopt proper tree care practices like regular pruning, watering, and mulching. Keeping trees healthy minimizes the chances of cottonwood borer infestations.
Effective Treatment Methods
There are a few insecticides that can help treat cottonwood borer infestations. Two common examples are:
These insecticides are available as contact insecticides and systemic insecticides. Contact insecticides kill borers on contact, while systemic insecticides are absorbed by the plant and kill borers when they eat the plant tissue.
- Effective in reducing borer populations
- Can protect valuable landscape trees
- May harm non-target organisms
- May require multiple applications
|Permethrin||Contact||Rapidly kills borers on contact||May harm beneficial insects|
|Carbaryl||Contact/Systemic||Can protect trees for up to a year||May require multiple applications|
Cultural practices involve non-chemical methods to prevent and manage cottonwood borer infestations. Some examples include:
- Protect young tree trunks with physical barriers like tree wraps, which can help to prevent egg-laying
- Prune and remove infested branches to reduce borer populations and prevent the spread of infestations
- Encourage natural predators such as birds, which can feed on adult cottonwood borers
- Burn infested wood to destroy larvae and prevent further infestations of wood borers
These practices, when combined with attentive monitoring and timely treatments, can help to keep borers in check and maintain the health of your trees.
Prevention and Maintenance
Proper Fertilization and Watering
A healthy tree is more resistant to pests like the cottonwood borer. To maintain healthy trees:
- Apply the right amount of fertilizer to support tree growth.
- Provide supplemental water during dry periods.
For example, a 10-10-10 fertilizer can promote robust tree health, making it less susceptible to infestation.
Pruning and Mulching
Regular pruning and mulching can further deter cottonwood borers:
- Prune dead or damaged branches to reduce egg-laying sites.
- Apply mulch around the tree base to retain moisture.
Following these practices, you can minimize the risk of cottonwood borers infesting your trees and keep them healthy and vibrant.
|Proper fertilization||Supports healthy tree growth||Needs regular upkeep|
|Supplemental watering||Prevents tree stress||Must monitor droughts|
|Pruning||Reduces egg-laying sites||Requires proper skills|
|Mulching||Retains moisture||Needs regular upkeep|
Cottonwood Borer Distribution
Cottonwood borers are found throughout North America, primarily infesting cottonwood, poplar, and willow trees1. These insects are common in areas where their host trees grow and can cause significant damage to young trees2.
- Infest cottonwood, poplar, and willow trees
- Widely distributed in North America
The Rocky Mountains region also has a presence of cottonwood borers, due to its suitable habitat for cottonwood trees. These trees provide shade and produce yellow flowers, attracting the borers3. In this region, borers can be a notable concern for various tree species.
Examples of Trees at Risk:
Table 1: Comparison of Trees Susceptible to Cottonwood Borer Infestation
|Tree Species||Native to Rocky Mountains||Provides Shade||Yellow Flowers|
Additional Tips for Dealing with Tree Borers
Identifying Other Tree Borers
There are various types of tree borers that can infest your trees, such as bark beetles, longhorn beetles, and wood-boring beetles1. When dealing with an infestation, it’s essential to identify the specific type of tree borer you’re dealing with. Here are some common examples of tree borers:
- Bark Beetles: Holes as thick as a pencil lead along the main trunk and major limbs2.
- Longhorn Beetles: Adult borers are conspicuously colored black and white, measuring 1 1/4 to 1 1/2 inches3.
- Wood-Boring Beetles: Reddish frass in bark crevices or around entry holes4.
To identify the specific type of tree borer, you can compare their physical appearance and the signs of damage caused by each. This will help you in determining the most effective method to tackle their infestation.
Enlisting Expert Help
If you’re unsure of the type of tree borer infesting your tree or need assistance with an infestation, consider enlisting the help of an expert. Professionals in the field of tree care and pest management can provide valuable advice and recommendations on how to deal with tree borers effectively. They can:
- Accurately identify the specific type of tree borer
- Provide tailored recommendations for treatment options
- Help prevent future infestations
By working with an expert, you can save time, effort, and ensure the health of your trees in a more efficient manner.
Over the years, our website, 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 – Cottonwood Borers
This bug was found in Oklahoma…..can you tell me what it is?
You have Cottonwood Borers, Plectrodera scalator. They are beetles from the long-horned beetle family Cerambycidae. These are very large black and white beetles. We have several photos on our beetle page from last year. Adults are common around cottonwood and poplar trees and the grubs bore into the wood of those trees.
Letter 2 – Cottonwood Borer
what bug is this?
I found this bug dead next to my doormat last night and wondered what on earth it could be? I live in Tulsa, OK near the Arkansas River. We get weird bugs in this area, but I’ve never seen horns like that. I’d be happy for a clue 🙂 Thanks,
The Cottonwood Borer is one of the most strikingly impressive native Cerambycids.
Letter 3 – Cottonwood Borer
I found this particular insect in my garage this evening and I’m not sure what it is. Can you help me identify it? Thanks in advance for your assistance.
San Antonio, TX
This magnificent beetle is a Cottonwood Borer, Plectrodera scalator. Its unique appearance assures that once identified, it will not be confused with any other North American insect. The larvae of the Cottonwood Borer bore into the wood of poplars and willows, generally near the base. Adult beetles eat young shoots from the host tree.
Letter 4 – Cottonwood Borer and Flesh Fly
Subject: Big striped bug
Geographic location of the bug: Edmond, OK
Time: 10:52 AM EDT
Your letter to the bugman: My son found this bug near a creek. It looked dead, as flies were crawling on it. It’s over an inch long.
How you want your letter signed: Gage
This magnificent beetle is a Cottonwood Borer, and since cottonwood trees are frequently found near water sources, that would explain the beetles proximity to the creek. The fly appears to be a Flesh Fly.
Letter 5 – Cottonwood Borer Pupa
This creature was found in Wichita, Kansas. I found this "grub" inside of a cotton wood tree I cut down to make room for my kids playset. I could find any entry point for their tunnels inside the tree. There were others just like it but they didn’t have the eyes, legs, antenna, or wings. They are approximately 1 inch in length. Any ideas?
This is a the pupa of a Cottonwood Borer, Plectrodera scalator, a magnificent black and white beetle. The grubs bore in the wood, feeding for several years, then pupate and emerge as adults, usually from July to September.
Letter 6 – Cottonwood Borer Takes Flight
Thanks for providing such an amazing site. I am a first time viewer / contributor. Your site helped me identify this beautiful creature. It’s a Cottonwood Borer, Plectrodera scalator. I have lived in and around Memphis, Tennessee all of my life and have never seen one of these beetles. My daughters came in the house screaming for me to get my camera a few days ago. I could not believe the patience of this bug! I must have taken 50 pictures or so before we realized that it flies! Oh, I should mention that I am still filled with excitement over the shot with the wings spread just before he was airborne. How cool is that? I was actually a little bit scared while taking a couple of those shots – he’s a pretty scary when you’re about 5 inches from those mandibles. Thanks for a great site – I have added it to my favorites.
I wasn’t sure what format you needed for the picture – I just combined all of my favorites in Elements and did a ‘save for web’ in jpg format. If you need anything additional that would work better, just let me know. Happy 4 th of July!
Your format was perfect, though our personal aesthetic for the site is to have separate images, hence we split out our mutual favorite image for posting. Thanks for your awesome submission of a Cottonwood Borer about to take flight.
Letter 7 – Cottonwood Borers
Hi I found your site after looking through about 50 websites trying to identify two bugs that I found in my backyard. I’m from Amarillo, Texas if that helps. I have attached pictures of these bugs. I have never in my life seen anything that resembled these two bugs! They are about 3-4 inches long with large antennae. They have pincher like mouths and are hard bodied. They can also fly but I don’t think they can go far because they are so large and heavy. Please help me figure this out because I have a young son and I’m afraid to send him out in the backyard thinking he might get bit by one of these. Thank you so very much for you help in my search!
You have Cottonwood Borers. They are beetles from the long-horned beetle family Cerambycidae. These are very large black and white beetles. We have several photos on our beetle page from last year. Adults are common around cottonwood and poplar trees and the grubs bore into the wood of those trees. They will not harm your children, but a huge infestation may harm your trees.
Letter 8 – Cottonwood Crown Borer
Subject: Odd markings and body shape…
Location: Northwestern Montana
July 28, 2017 3:29 pm
Hello from Montana! I’ve seen these a few times, but rarely had I seen one sit still long enough to take a photo. Fairly large, the wings and body shape are particularly interesting… but what exactly is it? I apologize for the photo not being a tad more clear, I did zoom in after taking the photo, I didn’t want to get too close!
This is one of the wasp-mimic Clearwing Moths in the family Sesiidae, and we quickly identified it as a Cottonwood Crown Borer, Sessia tibialis, on iNaturalist. American Hornet Moth is another common name according to BugGuide where it states that the range is: “Nova Scotia and New England, west to Vancouver, British Columbia, Rocky Mountains of Wyoming, Colorado and New Mexico, west to the Pacific Coast.”
Letter 9 – Cottonwood Dagger Moth Caterpillar
What are these bugs
Please help ID. The green hairy caterpillar with black spikes was crawling on a log my grandson was target shooting. Photo taken late Sept/early Oct in Brown County, OH (Southwestern Ohio farmland). Green caterpillar walking on a board under a green ash tree on the farm 9-26. How do I know if you have ID’d this photos when I go to your website? Thanks.
Mary Jo White
Hi Mary Jo,
This is some type of Dagger Moth. We try to write directly to people and we post the best and most interesting letters and photos.
I have finally ID’d the green caterpillar with black spikes. In Caterpillars of Eastern North America by David L. Wagner, pg. 337, Cottonwood Dagger Moth, Acronicta lepusculina, Noctuidae. Yeah!
Letter 10 – Cottonwood Leaf Beetle
I have to tell you just how interesting I have found your website. It has become quite habit forming. I am attaching 3 photos of a bug in various stages. These army of creapers have taken over my Weeping Willow Tree and are eating it up. Can you please tell me what they are and the best way to get rid of them. I live in NorthEast Arkansas.
Thanks so much for your time and knowledge.
Despite being called the Cottonwood Leaf Beetle, Chrysomela scripta Fabricius, this pest can also be found on willow trees, as you know. I would check with local agricultural experts regarding control, now that you know what you have. Both the adult on the left, and the larva on the right will eat leaves from the host trees. We found some information on this site. Good Morning,
Thanks so much for emailing me back so quickly. I am very happy to know exactly what kind of bug this is that is bugging me and my willow tree. I will get in touch with the Agricultural department today. Thanks so much for your time. I hope this email finds you having a wonderful day. Best Regards,
Letter 11 – Cottonwood Leaf Beetle Larvae
Subject: What is this bug?
Location: Suffolk, Virginia
May 17, 2015 1:14 pm
These little bugs are all over my deck, and the willow tree nearby. What are they, and how can I get rid of them?
Signature: Robin Moore
You are being troubled by Cottonwood Leaf Beetle Larvae, Chrysomela scripta, and according to BugGuide, it: “used to be considered a pest when willows were grown commercially for baskets, now of little economic consequence.” Featured Creatures has a very nice page on this species where it states: “The cottonwood leaf beetle, Chrysomela scripta Fabricius, is one of the most economically-important pests of managed cottonwood, aspen and some poplar and willow species. Although it does not present a serious pest problem in forests, often it is a severe pest of urban ornamental trees. This leaf feeder has several generations each year, may cause extensive leaf loss, and can consequently reduce stem volume up to 70% (Coyle et al. 2005).”
Letter 12 – Cottonwood Leaf Beetle Pupa
Subject: bugs on my weeping willow
Location: south east, north sc
May 20, 2015 3:08 am
These are all over my weeping willows and eating all the leaves.
This is a beetle pupa, and we were immediately struck by its resemblance to the larvae of the Cottonwood Leaf Beetle that we just posted. We did a quick internet search and our suspicion was confirmed on Featured Creatures. We are certain that this is the pupa of a Cottonwood Leaf Beetle, Chrysomela scripta.
Thank you so much. I’ve got to get rid of them. They are on just about every leaf of my weeping willows and in my birdfeeders. I would hope the birds would eat them. But it’s not happening. The leafs on my willows are just about gone.
Letter 13 – Metamorphosis of the Cottonwood Leaf Beetle
Cottonwood leaf beetle?
I first thought I had caterpillars on my willow tree but after looking at your site more I found that I seem to have Cottonwood Leaf Beetles. I captured some larvae in a butterfly pavillion to see what they would turn into and sure enough! Here are a few pictures. These are in Southeastern TX.
Your excellent documentation of the Metamorphosis of the Cottonwood Leaf Beetle, Chrysomela scripta, is an invaluable addition to our site. Thank you so much for your contribution.
Letter 14 – Cottonwood Borer
My wife found this beetle today.
It was quite large, with the body around 2” long (not counting the antennae).
It is a beautiful photo of a COTTONWOOD BORER, Plectrodera scalator.
Letter 15 – Stages in the Cottonwood Leaf Beetle Metamorphosis
Another Bug ID
The attached photo shows, (new to me), creatures on a Willow here in the Central California Coastal area. I presume they are various stages of the same insect. Any thoughts?
This is a Cottonwood Leaf Beetle, Chrysomela scripta, which we identified thanks to BugGuide. This species is found throughout North America. In addition to Cottonwood, they feed on Willows and Poplars. BugGuide states: “Adults and larvae found on willow– Salix , poplar– Populus sp. , and cottonwood– Populus deltoides, etc. Yellow or reddish eggs laid on clusters on underside of leaves. Black larvae skeletonize leaves, while adults attack only midrib and large veins. There are up to five broods per year.” Thanks for sending us your montage that includes the various stages of this beetle’s metamorphosis, including larvae and pupae.