Cactus Borers: Behavior, Damage, and Control Strategies

Cactus borers are a significant concern for those who cultivate or study cacti.

These pests, primarily the larval worms of cactus moths, have a unique lifecycle that revolves around the prickly pear cactus plants.

They lay their eggs on these plants, and upon hatching, the larvae tunnel into the cactus, causing potential damage.

This article aims to provide a comprehensive understanding of cactus borers, their types, and their impact on cacti.

Cactus Borer

What are Cactus Borers?

Cactus borers refer to a group of insects that target cacti, especially the prickly pear species. The most common among them are the larval worms of cactus moths.

These larvae are known to breach the outer skin of the cactus and make their way into the meaty part of the cactus leaves, causing internal damage.

The breeding process of these moths is quite fascinating. Adult moths lay their eggs on the prickly pear cactus plants.

Once these eggs hatch, the larvae initiate their damaging phase. They begin by breaking through the cactus’s outer skin.

Following this, they tunnel deeper, making their way into the meaty sections of the cactus leaves.

This tunneling not only affects the health of the cactus but can also alter its appearance and vitality.

Types of Cactus Borers

While the term “cactus borers” might seem singular in its reference, it encompasses a variety of insects, each with its unique characteristics and preferences.

Here’s a closer look at some of the primary types:

Cactus Longhorned Beetles

These beetles are particularly fond of certain types of cacti. Their favorites include prickly pears and cholla1.

However, there have been instances where they’ve been identified as pests on barrel cacti.

Their affinity for these specific cacti makes them a notable concern for those cultivating or studying these plants.

Blue Cactus Borer (Olycella subumbrella)

This insect, as its name suggests, is recognized by its distinct blue hue.

While it might appear harmless, it’s another pest that targets cacti, causing potential damage from the inside out.

Prickly Pear Borer
Prickly Pear Borer

Cactus Bug (Chelinidea vittiger)

This bug is another significant cactus borer. It’s known for its unique appearance and its propensity to target cacti.

The cactus bug, much like its counterparts, can cause considerable damage if left unchecked.

The Impact of Moist Conditions

The environment plays a pivotal role in the lifecycle and proliferation of cactus borers. One of the primary environmental factors that influences these pests is moisture. Here’s how:

Thriving in Wetness: Cactus borers, especially the types mentioned above, have a tendency to thrive in moist conditions.

Wet periods provide them with the ideal environment to breed, grow, and spread.

Natural Control During Wet Periods: Interestingly, while these insects flourish in moist conditions, they also serve a purpose.

They act as a natural control method during wet periods, curbing the excessive growth of cacti

This balance ensures that while cacti face threats from these borers, they also benefit from their presence during specific periods.

Understanding the relationship between cactus borers and their environment is crucial for those looking to manage or study these pests effectively.

Sawfly Larva or Caterpillar???
Tropical Cactus Borer

Treatment and Control

Managing cactus borers is essential for the health and longevity of cacti. While these pests can cause significant damage, there are effective treatments available:

  • Isopropyl Alcohol: This common household item can be an effective solution against cactus borers. By applying it directly to the affected areas, it can help in eliminating the pests and preventing further infestation.
  • Insecticidal Soap: Another effective treatment is the use of insecticidal soap. This soap is specifically designed to combat pests like cactus borers and can be purchased from gardening stores.
  • DIY Insecticidal Soap: For those who prefer a more natural approach, a DIY insecticidal soap can be made at home. By adding a few drops of dishwashing soap to a quart of water, you can create a solution that can be generously applied to the cacti using a spray bottle. This mixture helps in deterring the borers and provides a cost-effective method of treatment.

Cactus Moth: A Case Study

The cactus moth, scientifically known as Cactoblastis cactorum, serves as an intriguing case study in the world of cactus borers:

The cactus moth is a species of moth that has garnered attention due to its relationship with prickly pear cacti.

This moth played a pivotal role in the biological control of prickly pear infestations in Australia.

Introduced from Argentina into Australia in 1925, the cactus moth was free from its natural predators and parasites in this new environment.

This allowed it to effectively control the overgrowth of prickly pear.

The larvae of the cactus moth consume the pulpy tissues within the cactus pads.

This consumption, coupled with the rapid invasion by bacteria and fungi, results in a swift and almost complete collapse of the cactus plant.

Despite its success in Australia, the cactus moth has not been introduced in North America

The primary reason for this is the conflicting interests between those who value the prickly pear for various reasons and those who view it predominantly as a pest.

Other Insect Enemies of Prickly Pear

Prickly pear cacti, while resilient, face threats from a variety of insect enemies.

Apart from the cactus borers, several other insects target prickly pears, each with its unique method of infestation and damage.

Specifically, native insect enemies have a noticeable impact on prickly pear populations in Texas.

Their presence, combined with the state’s climate, makes prickly pear management a challenging task.

Frequently Asked Questions

How do I get rid of cactus mites?

Regularly inspecting your cacti and using miticides can help control and prevent spider mite infestations.

What are the little worms on my cactus?

These are likely the larval worms of cactus moths, which bore into the cactus and feed on its insides7.

What are the bugs in cactus used for?

Some bugs, especially cochineals, have been historically used for producing natural dyes. Additionally, certain bugs play a role in naturally controlling excessive cactus growth.

How do you treat cactus parasites?

Treatments range from natural remedies like insecticidal soaps to chemical solutions available in gardening stores.

How to get rid of cactus borers?

Regular inspection, natural repellents, and specific insecticides can help control and eliminate cactus borers10.

Conclusion

Understanding cactus borers and other pests is crucial for anyone interested in cacti, be it for cultivation, study, or mere appreciation.

While these pests pose challenges, it’s essential to recognize the balance they bring to the ecosystem.

By managing these pests effectively, we can ensure the health and longevity of our beloved cacti while also respecting the intricate web of life they’re a part of.

Reader Emails

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 – Tropical Cactus Borers

Subject: orange caterpillar
Location: Lakeland, FL
February 10, 2014 12:53 pm
We found several of these crawling around on rocks. They’re very fast movers, but curl up if you touch them. They’re about 1 to 1 1/4″ long. We didn’t see them on any plants, just the rocks.

We’re in Central Florida, inland and found them on 2/10/14. I’ve never seen anything like this before and after trudging through the interweb, don’t see any pics that match. As you can see in the 2nd fuzzy pic, they have black heads. He was on the move and hard to catch.
thanks for any help.
Signature: Cindy & Jim

Orange Larvae: Caterpillars or Sawflies???
Tropical Cactus Borers

Dear Cindy & Jim,
We are very rushed this morning and our initial attempts at identification did not produce any results.  We are posting your photos as unidentified and we hope to return to this later when we have more time.  Meanwhile, perhaps one of our readers wants to take up the challenge.  We are not certain if these are caterpillars or Sawfly Larvae.

Sawfly Larva or Caterpillar???
Tropical Cactus Borer

Thanks for your quick reply. We’ve never seen anything like it.

Considering your Florida location, this could easily be a new exotic import from a faraway land.

I was afraid of that. I feel like we should go hunt them down and hold on to them until we know what they are. We have too many exotics here.
thanks

Update:  August 13, 2018
Carpenter Moth Caterpillar
Because of a new query we just received that we are researching, we now believe both this and an additional posting in our archives are Carpenter Moth larvae in the family Cossidae, but we are uncertain of the species since the larvae do not look like any posted to BugGuide., but they do resemble what has tentatively been identified as the Carpenter Moth Caterpillar Macrocassus toluminus from South Africa.

Update:  Tropical Cactus Borers
Ed. Note: 
The following is a comment from Cesar Crash.
Those look like Lepidoptera. Found on a cactus garden, may be the cactus moth: https://www.ipmimages.org/browse/detail.cfm?imgnum=5015058 aka Tropical Cactus Borer https://bugguide.net/node/view/78959/bgpage

Thanks so much Cesar.  The mystery is finally solved.  Here is a nice BugGuide image of the caterpillar.  According to BugGuide:  “Imported to the Caribbean to control prickly pear cacti; arrived in the U.S. naturally or in cargo imported from the aribbean (Johnson and Stiling 1998).

Widely dist. in southern FL, spreading east along the Gulf Coast to New Orleans and north along the Atlantic Coast to SC.”  BugGuide also has this interesting statement:  “The moth has become a pest in se US.   This South American moth was introduced into Australia to control cacti, which are not native to that continent and which were becoming a very serious pest. It was so successful that memorials and monuments to it have been erected by grateful citizens there.”

Letter 2 – Prickly Pear Borer

Prickly Pear BorerSubject:  Unknown bug (caterpillar)
Geographic location of the bug:  Lexington County, South Carolina
Date: 07/21/2022
Time: 09:22 PM EDT
Your letter to the bugman:  I found these guys on my prickly pear cactus. They were in the process of spinning silk. No one has been able to ID them. Our local extension suggested prickly pear cactus borer but it doesn’t match other pictures.
How you want your letter signed:  Any help would be appreciated!

Prickly Pear Borer
Prickly Pear Borer

We believe this is a Prickly Pear Borer, a caterpillar in the genus Melitara.  Here is a BugGuide image for comparison.
Ed. Note:  This posting was rescued after being lost during a recent upgrade

Authors

    by
  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com 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.

  • Piyushi Dhir

    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.

3 thoughts on “Cactus Borers: Behavior, Damage, and Control Strategies”

  1. Hey guys, that’s really cool little larvae! If they’re still around, you can tell if they’re sawflies by the number of prolegs (those little leg nubs that aren’t like the 3 pairs of true legs up front). If they have 6+, they’re sawflies. Caterpillars have 5 or less. Good luck! I’m in Central FL too, and I’ve never seen these before either.

    Reply

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