Locust borers are a common pest that can cause severe damage to beautiful, mature trees like black locusts. These wood-boring beetles lay their eggs in the bark and trunks of locust trees, leading to weakened branches and potential tree death if left untreated.
While it might seem daunting to tackle this problem, there are certain measures one can take to prevent and control locust borer infestations. These methods include regular monitoring, tree care practices like proper pruning and thinning, and chemical controls when necessary to protect your treasured locust trees.
Some effective strategies for dealing with locust borers involve removing infested trees and peeling or burning the bark to kill larvae during dormancy. Remember, the best approach combines multiple tactics suited to your specific situation, ensuring the health and longevity of your trees.
Identifying Locust Borers
Locust borers are a type of long-horned beetle, with adults measuring about one inch in length. They are black with bright yellow markings, including a distinctive “W” across their wing covers, and have reddish legs1. Their larvae are white and legless, featuring a large prothorax2.
Host Tree Identification
Locust borers specifically target black locust trees3. Being aware of these trees in your area can help you identify potential infestations early on.
Signs and Symptoms
- Presence of holes in the bark1
- Reddish frass (insect waste) in bark crevices or around holes1
- Cracks or knotted areas on branches4
It is essential to regularly inspect black locust trees for these symptoms to catch locust borer infestations early and take appropriate action.
Prevention and Treatment Methods
Maintaining Tree Health
Keeping trees healthy is key in preventing locust borer infestations. A well-maintained tree can resist pests and diseases more effectively. Some measures to maintain tree health are:
- Adequate watering during drought conditions
- Providing nutrient-rich soil to ensure strong growth
- Regular pruning of dead or damaged branches
For example, if you have a healthy locust tree, it’s less likely to be attacked by locust borers than a stressed or weakened tree.
Using chemical insecticides can help control locust borers. One option is applying a carbamate or pyrethroid insecticide to the tree bark in late July or early August, before eggs are laid1. However, there are pros and cons to consider:
- Effective in controlling the locust borer population
- Can easily be applied to tree bark
- Possible risk to non-target insects and the environment
- Might require multiple applications for full effectiveness
Alternative Treatment Methods
Alternatively, non-chemical treatment methods can be used to control locust borers. For example, physically removing infested wood or branches and subsequently chipping or burning them can help manage the pest population2. Another method is using safe biological controls, like introducing predators or parasites that attack the locust borer.
Comparison between Chemical and Alternative Treatment Methods:
|Chemical||Effective, easy to apply||Environmental concerns, multiple applications required|
|Non-Chemical||Safe, eco-friendly, physical removal of pests||Can be time-consuming, some methods may not be as effective as chemicals|
Remember that proper tree health management and a combination of these methods can provide the best defense against locust borers.
Dealing with Infestations
Inspecting for Infested Trees
Identifying infested trees is crucial in dealing with locust borer infestations. Look for:
- Holes in the bark
- Reddish frass in bark crevices or around the base of the tree
- Signs of larval feeding, such as branches with sawdust-like material1
To inspect the trees, focus on the trunks and large branches since these are where locust borer larvae usually tunnel2. Consult with a tree specialist if you’re not sure about potential infestation.
Removing and Destroying Infested Trees
Killing the locust borer larvae is essential for successful infestation management. Remove infested trees or branches, and choose one of these disposal methods:
- Chipping the removed wood to destroy larvae
- Burning the infested material to ensure effective extermination2
Keep in mind that prompt removal may prevent further infestation to other trees.
Protecting Unaffected Trees
Proactively protecting unaffected trees can help control locust borer infestations. To maintain overall tree health:
- Provide appropriate care, such as watering, fertilizing, and pruning
- Apply a carbamate or pyrethroid insecticide to the bark on the tree’s trunk and large scaffold branches2
|Prevents further damage to unaffected trees||Chemicals might have adverse effects on beneficial insects|
Remember that maintaining the health of your garden and trees is essential in avoiding locust borer issues and other destructive pests like emerald ash borer and grasshoppers.
Locust Borers and Their Impact on Agriculture
Crop Damage and Economic Losses
Locust borer is a destructive insect, Megacyllene robiniae, that tunnels into the wood of locust trees. They create holes and weaken the tree structure, leading to crop damage and economic losses in agriculture.
- Holes in the trunk and branches weaken the tree
- Sawdust-like frass indicates infestation
For example, locust borer infestation in black locust trees can decrease their value as timber and honey producers.
Management Strategies for Agricultural Settings
Effective management strategies for locust borers include maintaining tree health and applying timely insecticides.
- Tree Health: Improve or maintain overall tree health to make them less susceptible to infestations.
- Insecticides: Apply carbamate or pyrethroid insecticides to the bark on the trunk and large scaffold branches in late-July/early-August, prior to egg-laying.
Here is a comparison table of the two strategies:
|Tree Health||Natural approach, better long-term solution||Requires regular care and maintenance|
|Insecticides||Quick and effective||Potential harm to beneficial insects and the environment|
Pruning infested wood and branches, then chipping or burning them, can also help control locust borer populations.
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 – Locust Borer
black & yellow striped bug
September 29, 2009
Hi Bugman, I submitted this last week, but I think it might not have gone through. These black and white striped bugs are all over our Globe Locust trees, and I would love to know what they are, are they beneficial or something to be concerned about. Any danger in handling them?
Overland Park, KS (Kansas City area)
It was observant of you to associate the Locust Borer with your Globe Locust Trees. The Locust Borer is a native insect. Here is what BugGuide has to say: “Life Cycle Eggs are laid in locust trees in the fall. Newly emerged larvae spend several months in tree trunks, first hibernating through the winter under the bark, then tunneling into trees in spring, eventually making tunnels about 4″ long and .25” inch wide. They pupate late July/early August. Adult beetles emerge late August to September (click on the Data tab for a graphic confirmation of that fact). Remarks Considered a serious pest of Black Locust trees; previously weakened or damaged trees are often killed by an infestation of the larvae. Previously confined to the native range of Black Locust in the northeast, it has spread with the trees throughout the US. Unfortunately Black Locust is used for reclamation and similar projects where trees are likely to be stressed out and thus more vulnerable to insect damage.“ Adults feed on pollen and they are generally associated with Goldenrod.
Letter 2 – Locust Borer
Subject: Yellow Jacket Mimic
Location: Ritzville, WA
September 10, 2013 10:54 am
I noticed this insect while pumping gas at a gas station near Ritzville, WA. It’s legs will twitch spontaneously like a yellow jackets’ back legs do. It stayed very still otherwise.
Signature: Thank you Glen
This Locust Borer is a very effective Yellow Jacket Mimic. Adult Locust Borers are often found on goldenrod in the autumn. Larvae bore into black locust trees. According to BugGuide: “Considered a serious pest of Black Locust trees; previously weakened or damaged trees are often killed by an infestation of the larvae. Previously confined to the native range of Black Locust in the northeast, it has spread with the trees throughout the US. Unfortunately Black Locust is used for reclamation and similar projects where trees are likely to be stressed out and thus more vulnerable to insect damage.”
Letter 3 – Locust Borer
Imposter Yellow Jacket
September 11, 2009
I found this bug basking in the sun on my grape vine a few days ago. There has been a plague of yellow jackets this year eating my berries, so I assumed that this was one who had had his fill, but on closer examination, it doesn’t look like any sort of hymenopteran. It looks more like a beetle to me. Is it? Does it intentionally look like a bee/wasp/yellow jacket to ward off would-be predators?
Post Falls, Idaho (Northern Idaho)
Your observation that this Long Horned Borer Beetle, the Locust Borer, Megacyllene robiniae, is a Yellow Jacket mimic is quite astute. The mimicry is probably most effective when the Locust Borer is feeding on the pollen of goldenrod because predators would tend to avoid what looks like a stinging insect despite the Locust Borer being perfectly harmless.
Letter 4 – Hickory Borer or Locust Borer???
Please help identify
Location: dayton, OH
April 1, 2011 2:34 pm
This is one of 6 of these bugs that I have found in my house. May have brought them in with firewood, but now the wood is outside, but I still see the bugs.
Signature: david hurwitz
The fact that you found this beetle indoors, and that your letter indicates you had firewood might make an exact identification impossible. This is a Borer Beetle in the genus Megacyllene and there are two species that look nearly identical. We generally distinguished them based upon the time of the sighting. The Hickory Borer, Megacyllene caryae (See BugGuide), appears in the spring while the Locust Borer, Megacyllene robiniae (see BugGuide), makes its appearance in the fall. Since you had firewood stored indoors, the natural life cycle may have been upset, causing the Locust Borers to emerge early. Neither species will harm your home.
Actually, the firewood was only brought inside in Feb. and taken back outside mid march. But you did answer my main question – harmful to the house. Thank you.
Letter 5 – Hickory Borer, not Locust Borer
Swarming, green/yellow abdomen, large antennae
April 6, 2010
I was sitting on the back porch around 8p and heard the sound of several large bugs hitting the side of my house. When I saw them there probably 50-100 or more crawling, swarming, and apparently mating. They were on the north and east sides of the house. I tried an insecticide on them but that didn’t seem to help. Do you know what this is and what should I do about it?
Jeff in Louisville, KY
Another reader just left a comment on a posting of a Locust Borer in the belief that she had identified an insect that recently appeared. The Locust Borer, Megacyllene robiniae, and your insect, the Hickory Borer, Megacyllene caryae, are in the same genus, and they are very difficult to tell apart, but the Locust Borer appears in the autumn, and the Hickory Borer appears in the spring. We wish your photo was more in focus.
Letter 6 – Hickory Borers or Locust Borers???
Subject: black with yellow stripes
March 24, 2013 5:37 am
Yes we live in Missouri and in the last few weeks we have had this flying black and yellow striped bug in our house and there are several of them, what are they and how do i get rid of them, I’m not even sure how they are getting in the house. its cold and snowing out and they are still here. Please help
Signature: Kevin Kearns
The best way to get rid of these Hickory Borers or Locust Borers is to stop bringing them into the house in the first place. Both species are closely related and they have larvae that bore in wood. We suspect you brought in some firewood, possibly hickory, pecan or black locust, and rather than burning it immediately, you left it where you keep the indoor wood supply. The heat of the home triggered an early emergence of the adult beetles. They will not reinfest the wood in your home or furniture as they are only interested in laying eggs in living or recently dead trees as a food source for the larvae. The two species are very difficult to tell apart, but Hickory Borers, Megacyllene caryae, are active as adults in the spring, and Locust Borers, Megacyllene robiniae, are active as adults in the autumn when they are often found feeding on the pollen of goldenrod.
Letter 7 – Locust Borer
I found this on the patio this morning. A little more info. I found this on the patio this morning. I am in eastern Washington state. It is about an inch long and could move by crawling fairly quickly. It didn’t fly.
The Locust Borer, Megacyllene robiniae, one of the Long Horned Borer Beetles from the Family Cerambycidae, is capable of flight. The adult Locust Borer is often found on goldenrod where it eats pollen and nectar. The larvae bore in the wood of Black Locust trees after eating the bark. Thank you for your photo. We like getting good images of signature insects. The Locust Borer ranges throughout the Eastern and Southern U.S. and eastern Canada.
Letter 8 – Locust Borer
Yellow & Black
Found this in my home in Newton, MA. After doing some internet seaching I thought it could be Clytus ruricolo (beetle)…its about 1 1/4" inches long.
This is a Locust Borer, Megacyllene robiniae. Larvae bore in the sapwood of Black Locust trees and adults feed on nectar and pollen, especially from Goldenrod.
Letter 9 – Locust Borer
September 12, 2009
Shortly after you identified my photos of the amorpha borer (or locust borer) I came across this one. It appears to be similar to the amorpha borer, but perhaps a different species. Can you identify it, please? Thanks!
near Omaha NE
This time your insect is a Locust Borer. They appear in the autumn and they are often associated with goldenrod.
Letter 10 – Locust Borer
Locust Borer mimics wasp
Location: Fairfield, Maine USA
August 8, 2010 3:22 pm
Today I found this thing in the Goldenrod. First I though it was wasp, but as I got closer I knew it was not a wasp. I got a bunch of pictures of it feeding on nectar. It was hard to get a view of the underside because it was always clinging against the flower. I looked it up on B.G. and it seems to be an adult Locust Borer-Megacyllene robiniae. Can you confirm the identification? It’s larva seem to be considered a pest to Black Locust trees…
Your identification is correct, and yes, the Locust Borer is an excellent wasp mimic. We are thrilled to receive your images of the adult Locust Borer on its favorite food flower, the Goldenrod.
Letter 11 – Locust Borer
Location: Richland, WA USA
September 10, 2011 9:35 pm
I was at a picnic and I saw this guy on my shoe. Do you know what it is?
This strikingly marked beetle is a Locust Borer, Megacyllene robiniae, and it is an excellent mimic of stinging wasps like Yellow Jackets. Now that autumn is approaching and the goldenrod is beginning to bloom, we expect to be receiving numerous identification requests since the adults feed on pollen, especially goldenrod pollen. The larvae bore in the wood of Black Locust trees. According to BugGuide: “Eggs are laid in locust trees in the fall. Newly emerged larvae spend several months in tree trunks, first hibernating through the winter under the bark, then tunneling into trees in spring, eventually making tunnels about 4″ long and .25″ inch wide. They pupate late July/early August. Adult beetles emerge late August to September.” BugGuide also confirms our suspicions that this is not a native insect in the Pacific Northwest with this information: “Considered a serious pest of Black Locust trees; previously weakened or damaged trees are often killed by an infestation of the larvae. Previously confined to the native range of Black Locust in the northeast, it has spread with the trees throughout the US. Unfortunately Black Locust is used for reclamation and similar projects where trees are likely to be stressed out and thus more vulnerable to insect damage.” The Locust Borer was our Bug of the Month in October 2007.
Letter 12 – Locust Borer
Subject: Yellow with black W designs flying bug
Location: Blue Ridge, GA
March 12, 2017 9:07 pm
My friend asked me to get this bug identified. We live in North GA mountains. It was taken 8 years ago during summer. She has only seen one, once. I think it’s a beetle, but cannot find its identity. Thank you in advance.
Signature: Lisa the buglady
Dear Lisa the buglady,
There are many people who recognize that the color and markings on the Locust Borer are an effective defense mechanism as it causes the harmless beetle to resemble a stinging wasp like a Yellowjacket.
Letter 13 – Locust Borer
Yellow and black beetle
Geographic location of the bug: Inland Northwest USA (Spokane, WA)
Time: 07:32 PM EDT
We found a bright beetle in our backyard. Our mom tried to look it up but couldn’t find an answer for sure. We think it is a wasp mimic beetle but we aren’t sure. Please help! 🙂
How you want your letter signed: Jack and Archie
Dear Jack and Archie,
You are correct that the Locust Borer is an effective mimic of stinging Yellowjackets. The larval host tree is the black locust, which is native to the North American northeast, but with the planting of black locust trees in other locations, including Washington, the range of the Locust Borer has expanded as well. According to BugGuide: “Considered a serious pest of Black Locust trees; previously weakened or damaged trees are often killed by an infestation of the larvae. Previously confined to the native range of Black Locust in the northeast, it has spread with the trees throughout the US and parts of Canada. Unfortunately Black Locust is used for reclamation and similar projects where trees are likely to be stressed and thus more vulnerable to insect damage.”
Letter 14 – Locust Borer
Subject: yellow black bug
Geographic location of the bug: Indianapolis
Time: 10:12 PM EDT
Your letter to the bugman: I found this bug on a love-lies bleeding plant. he was waiting for the breeze to come and when it did he flew away.
see on you tube
How you want your letter signed: yellow black bug
The Locust Borer is a common beetle found where the larval food plant, black locust, is found. Adult Locust Borers are excellent Yellowjacket mimics, and they are often found on autumn flowers, especially goldenrod.