Squash Vine Borer: All You Need to Know for a Healthy Garden

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Growing your own squash or pumpkins can be a rewarding experience, but encountering the dreaded squash vine borer is a common challenge for gardeners. It’s essential to know about this clearwing moth and its destructive larvae, as they can decimate your crop if not managed properly.

The squash vine borer, active from mid-June to July, lays eggs on the stems of your plants, typically just above the ground surface. Once the larvae hatch, they burrow into your squash vines, where they feed and cause yellowing of leaves and wilting. It’s crucial to learn about this pest’s lifecycle and effective management strategies to protect your plants and enjoy the fruits of your labor.

In the coming sections, we’ll dive into squash vine borer identification, prevention methods, and treatment options. Having this knowledge in your gardening toolkit, you’ll be better equipped to deal with these pests and keep your squash plants healthy and thriving.

Identifying Squash Vine Borer

Squash vine borers are pests that can significantly damage your squash plants. Identifying these pests early is crucial to managing them effectively.

Appearance of Adult Moth: The adult squash vine borer is a day-flying moth with a unique appearance, similar to a wasp rather than a moth. Its abdomen is dark grey or dull orange, marked with black dots, and features hairy hind legs with orange markings. Their wings are folded back over their body while resting and have a wingspan of around one inch. The moth’s metallic green body adds to its distinctive look.

Larvae Details: The larvae are the primary cause of plant damage. These little pests have a brown head and a white body. They come equipped with 8 pairs of appendages – three pairs of true legs and five pairs of prolegs (Penn State Extension).

To help you better understand the squash vine borer, here are some key characteristics:

  • The moth’s appearance resembles a wasp more than a moth.
  • It has a metallic green body.
  • The larvae have a brown head and white body.
  • Adult moths are around 1 inch in wingspan.

By learning to quickly identify these pests, you’ll be better equipped to protect your squash plants and ensure a healthy harvest.

Squash Vine Borer Life Cycle

The life cycle of the squash vine borer begins with eggs. Female moths lay these tiny, brown, flattened eggs on the vines of summer squash, winter squash, and pumpkins. They are about the size of a pencil point1.

When the larvae hatch, they have a brown head and white body1. As they feed on the plants, their presence leads to yellowing leaves and wilting2. To protect your plants, pay attention to these signs and scout for larvae. If you spot any frass or tiny holes, carefully cut open the vine and remove the offending larva3. Afterward, cover the stem with soil to aid the healing process3.

Larvae eventually turn into pupae and overwinter4. This means they survive through the colder months by finding shelter in the soil4. The following summer, the overwintering pupae transform into adult moths4. These clearwing moths have a distinctive appearance, with transparent wings and a wasp-like look5.

In summary, the squash vine borer life cycle goes from eggs to larvae, pupae, and adult moths. By understanding this process, you can manage these pests more effectively in your garden. Keep an eye out for the specific signs and characteristics they exhibit during each stage, and take appropriate action to protect your plants.

Signs of Squash Vine Borer Infestations

Plant Wilt

One of the first signs of a squash vine borer infestation is plant wilting. You may notice yellowing of leaves and wilting, which occurs when larvae feed on the plant’s inner tissues, disrupting water and nutrient flow source. Keep an eye on your squash plants, especially during mid-June through July, when squash vine borers are most active.

Sawdust-like Material

Pay attention to the base of your squash plants: if you see a sawdust-like material, it could be frass – the excrement of squash vine borer larvae. When larvae burrow into the stems to feed, they push out the frass, which can be a clear sign of infestation source.

Small Holes in Stems

Look for small holes in the stems of your squash plants. These holes are made by the larvae as they burrow into the stems to feed source. If you find these holes, it’s essential to take action, as they can quickly lead to plant wilt and death.

Presence of Larvae

Inspect your plants for larvae, which look like little white grubs with dark heads. They are rarely found outside the vine, but if you see them, it’s a clear sign of infestation source.

Secondary Infections

Finally, the damage caused by squash vine borer infestations can lead to secondary infections. The holes in the stems can allow bacteria and fungi to enter, further harming the plant and potentially leading to diseases such as bacterial wilt or Fusarium wilt source.

To summarize, some signs of squash vine borer infestations are:

  • Plant wilt
  • Sawdust-like material (frass) near the base of the plant
  • Small holes in stems
  • Presence of white larvae with dark heads
  • Secondary infections caused by stem damage

Host Plants for Squash Vine Borer

Squash vine borer, a native sesiid moth, mainly targets plants belonging to the cucurbit family. As a gardener, knowing which plants are susceptible can help you take preventative measures and protect your garden.

Pumpkins and Squash: The borer’s larvae are notorious for tunneling through pumpkin and squash stems, ultimately causing the plants to wilt and die. Both summer and winter squash varieties are affected, including butternut, acorn, and hubbard.

Zucchini and Melons: You might find these pests on zucchini and melon plants as well. Although not as common, it’s important to keep an eye on these plants too.

  • Summer Squash: Plants like zucchini and yellow squash can experience damage from the borer.
  • Winter Squash: Butternut, acorn, and hubbard squash are also susceptible, as they belong to the same family as pumpkins.
  • Melons: While slightly less common, melons, including watermelons and cantaloupes, can also serve as host plants for the squash vine borer.
  • Gourds: Bitter gourds and other ornamental varieties may also be targeted by this pest.

In conclusion, the squash vine borer can damage various plants belonging to the cucurbit family. By carefully monitoring your plants and implementing preventive measures, you can minimize the impact of these pests and enjoy a healthy, productive garden.

Methods to Control Squash Vine Borer

Using Insecticides

One effective method for controlling squash vine borer is using insecticides such as Bacillus thuringiensis (Bt). It’s a naturally occurring bacteria targeting the larvae. Apply Bt when you see the first signs of adult moths, typically in mid-to-late June.

Setting Barriers

Adding a physical barrier can help prevent squash vine borers from laying eggs on your plants. Wrap stems in aluminum foil or another material to create a barrier they cannot penetrate. This deters moths from depositing their eggs.

Proper Watering Techniques

Proper watering can reduce stress on plants, allowing them to better resist pests. Avoid overwatering or underwatering your plants, focusing on maintaining consistent soil moisture.

Cultural Control Practices

Cultural control involves non-chemical methods to manage pests. For squash vine borer, try:

  • Crop rotation to prevent future infestation
  • Checking plants daily for signs of borer activity
  • Removing and destroying infested plants.
    These practices help reduce the likelihood of long-term infestation.

Attracting Natural Predators

Attracting natural predators like birds or wasps to your garden can assist in controlling squash vine borers. Building birdhouses or planting flowers that attract wasps are examples of how to implement this strategy.

Using Row Covers

Using floating row covers is another method to control squash vine borer. Install these covers over your plants early in the growing season as a physical barrier against pests. Remove them during pollination to allow pollinators access to your plants.

Bug Control Recommendation Tool

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How Squash Vine Borer Overwinters

The squash vine borer is a persistent pest that can wreak havoc on your garden. Understanding how it overwinters is crucial for managing its population. The squash vine borer overwinters in the soil as a larva or brown pupa, hidden an inch or two down in the ground.

These tiny pests are enclosed in dirt-covered, dark silk cocoons, which are about 3/4 inch long. The cocoons are quite tough, protecting the overwintering larvae and pupae from harsh weather conditions. As spring arrives, the larvae transform into pupae and the adult moths emerge in June and July2.

To reduce squash vine borer populations, you can:

  • Monitor your garden for adult moths during the peak season (June and July).
  • Rotate your crops to disrupt the lifecycle of the borer.
  • Till your soil in the fall and spring to expose the overwintering pupae to predators and the elements.

Impact on Garden and Crops

Squash vine borers can be a significant problem for gardeners, as they target the stems of plants, like squash and cucumbers. They tend to lay their eggs in the soil near the host plant which hatch into larvae that burrow into the vine to feed on it. This affects the plant’s ability to transport water and nutrients, eventually causing the plant to wilt and die.

To minimize the damage, keep an eye on your plants for any signs of these pests. Look for little white grubs with dark heads that can usually be spotted around the base of your plants or the appearance of frass (insect waste) near the vine.

Being proactive can save your crop. For example, if you notice larvae or frass, you can cut the vine lengthwise near the entry hole, remove the larva, and cover the stem with soil. This helps the plant recover and continue growing.

Keep in mind that these pests can overwinter in cocoons in the soil, especially in areas where squash or zucchini plants were grown the previous season. Rotating your crops and not planting squash or cucumbers in the same area can help reduce squash vine borer populations in your garden.

In summary, here are some key points to remember when dealing with squash vine borers:

  • They target stems of plants like squash, cucumbers, and pumpkins.
  • They lay eggs in soil and can overwinter in cocoons, so consider crop rotation as a management practice.
  • Look for larvae and frass as signs of squash vine borer presence.
  • Be proactive and remove the larvae if you notice any infestation, then cover the stem with soil to help the plant recover.

Preventing and managing squash vine borer infestations will ensure a healthier and more productive garden, ultimately leading to more successful crops.

Footnotes

  1. https://extension.psu.edu/squash-vine-borer 2
  2. https://extension.umn.edu/yard-and-garden-insects/squash-vine-borers 2
  3. https://extension.illinois.edu/blogs/good-growing/2022-07-15-managing-squash-vine-borer-garden 2
  4. https://www.canr.msu.edu/news/squash_vine_borer_biology_and_management 2 3
  5. https://hort.extension.wisc.edu/articles/squash-vine-borer-melittia-curcurbitae/

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 – Flying Squash Vine Borer

 

help identify this moth
Hi, I photographed this moth in my backyard yesterday, 7-5-05. Could you please help me with identification? Any help would be greatly appreciated. We live in Laingsburg, MI if that is any help geographically. Thanks again,
Kevin Dutil

Hi Kevin,
This is the second Squash Vine Borer, Melittia satyriniformis, we received in two days. The larvae bore into squash and pumpkin stems and kill the plants.

Letter 2 – Glorious Squash Vine Borer

 

Subject: Is it a moth???
Location: Texas Pahnandle
September 9, 2016 1:05 pm
My son took a picture of this moth?? On the Canadian River Bottom on Stinnett, Tx..
Can you please tell me what it is?!
Signature: Trinity

Glorious Squash Vine Borer
Glorious Squash Vine Borer

Dear Trinity,
We are confident that we have identified this wasp-mimic Moth in the family Sesiidae as a Glorious Squash Vine Borer,
Melittia gloriosa, thanks to images on the Moth Photographers Group, and we verified that identification on BugGuide where we learned:  “Larvae bore in the large tubers of various cucurbitaceous plants” and that it is also called the Manroot Borer. We hadn’t given the Manroot much thought regarding its family, but on Las Pilitas Nursery site, we learned the Manroot or Wild Cucumber is a member of the family Cucurbitaceae and we suspect that your Glorious Squash Vine Borer may have gotten its common name of Manroot Borer because it feeds on the Manroot.   This BugGuide image is an especially good visual match to your image.

Letter 3 – Manroot Borer

 

Subject: odd bug
Location: NE Los Angeles County, California (Tujunga, CA 91042)
July 14, 2017 5:21 pm
It flies, it is the size of a large carpenter bee. I has a beetle like head ans wings that are orange, white and black that appear to attach at the back legs. His coloration is much like a monarch caterpillar on his body.
Signature: Pauline Penn

Glorious Squash Vine Borer

Dear Pauline,
This is one of the wasp-mimicking moths in the family Sesiidae, and we were lucky to locate the Sesiidae of Los Angeles County page on iNaturalist.  We believe this is a Glorious Squash Vine Borer,
Melittia gloriosa.  There are some nice images on BugGuide.  According to BugGuide it is also called the Manroot Borer and  “Larvae bore in the large tubers of various cucurbitaceous plants.”  Manroot is a native plant that is also known as wild cucumber.  The dried leaves in your one image appear to be the leaves of a manroot.

Manroot Borer
BINGO! Kudos Smile That is him, and that is also the dried leaves of the Manroot in the backyard.
Awesome! Thanks

Letter 4 – Squash Vine Borer

 

Moth?
I found the moth in my back yard this summer and have surfed the internet extensively looking for it but have not been able to find it. What is it? The closest I can figure is some sort of Sesiid. It was between 3/4 and 1 inch long. Seen July 8 in my backyard in Dayton, OH.
Bill

Hi Bill,
The Squash Vine Borer, Melittia cucurbitae, is one of the Sesiid Moths or Clearwing Moths known to mimic wasps. There might be some confusion on the scientific name. We have also seen it listed as Melittia satyriniformis in both our very old Holland Guide and our Audubon Guide, but BugGuide uses cucurbitae. We have an image of one flying, but your photo shows it in the resting position.

Letter 5 – Squash Vine Borer

 

Blue winged wasp?
May 22, 2010
Hi, My wife took this picture and I searched but was unable to identify what kind of insect this is. Not sure if it’s a wasp or a moth masquerading as a wasp. Would love your opinion!
Penley
Austin Texas

Squash Vine Borer

Dear Penley,
Just because it looks like a wasp, does not mean it is a wasp.  Because many wasps sting if provoked, several different groups of insects, but especially moths and flies, mimic wasps for protection.  This is a Squash Vine Borer, Melittia cucurbitae, a member of the clearwing wasp moth family Sesiidae.  You can compare your individual to the numerous images posted to BugGuide.

Letter 6 – Squash Vine Borer

 

Black and orange fly, or wasp
July 5, 2010
I saw this in my garden and can’t find anything that looks quite like this. It was on my zucchinin plants and was about an inch to inch and a quarter long and seemed to like being in the sun, the main body was bright orange and the tops of the legs were orange also, on it’s back were black stripes or long spots on it. I don’t have a good picture since I was out in the garden and only had my cell phone.
JD
Northern Illinois, US

Squash Vine Borer

Dear JD,
The Squash Vine Borer,
Melittia cucurbitae, that you have photographed and submitted is actually a moth that mimics a wasp.

Letter 7 – Squash Vine Borer

 

Bee/Beetle/Fly ????
July 5, 2010
Dear Bugman,
We were out in our garden when we saw this weird bee??? collecting pollen. We thought it was very odd and had never seen anything like it before. It has very hairy legs and was definetly collecting pollen. It has wings almost like a dragonfly and antenna like a butterfly. We really don’t know that much about bugs but do know that we have never seen anything like it…soooo we were hoping you could help us identify it. Thanks!!
Manda & Michael
Clay City, Indiana

Squash Vine Borer

Dear Manda and Michael,
This moth is a wasp mimic in the family Sesiidae, and it is the Squash Vine Borer,
Melittia cucurbitae.  The female wasp lays her eggs on the stems of squash and pumpkin vines, and the larvae are stem borers that can cause considerable damage to the plants.

Letter 8 – Squash Vine Borer

 

orange bug id?
Location: Dallas, TX
May 16, 2011 11:08 am
I found this orange and black bug on my squash plants this morning. I’m in Dallas, Texas. Can you identify it?
Thanks,
Misty
Signature: Misty

Squash Vine Borer

Hi Misty,
Though it looks like a wasp, the Squash Vine Borer,
Melittia cucurbitae, is actually a moth.

Well, that will teach me for hesitating to kill an insect that looks interesting.  It was quite pretty, but it’s gonna die if I see it again.  Thanks very much!!!! 🙂
Misty

Letter 9 – Squash Vine Borer

 

About a weird red bug on my pumpkin stems
Location: Pittsburgh Pennsylvania
June 26, 2011 1:43 pm
Hello,
this morning I noticed a weird red bug that looked like a cross between a beetle and a wasp that was fully bright red with several black dots down its abdomen. The abdomen curled up just like a bee’s does when it’s pollinating, and its wings were pretty large and totally black. But the front of its body resembles a beetle shape. I am attaching the few pics I was able to take before it flew away. We have a small garden, but everytime it flew away and came back it went right back to the pumpkin stems at the bottom near the dirt and seemed to be stabbing the thickest part of the stem like a bee pollinates flowers.I have never seen anything like this insect before and was wondering if you could help identify it. Was wondering if it was good or bad for the pumpkin plant.
Thank you
Signature: Cheri Fazio

Squash Vine Borer

Hi Cheri,
This is a Squash Vine Borer in the family Sesiidae, the Clearwing Moths are are wasp mimics.  The behavior you describe is consistent with that of a female ovipositing, or laying eggs.  The larvae bore in the stems of plants in the squash family including pumpkin and melons.

Authors

  • 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.

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  • 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.

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Tags: Squash Vine Borers

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3 Comments. Leave new

  • Julian Donahue
    July 15, 2017 12:17 pm

    This is indeed a Glorious Squash Vine Borer, originally described from California by Henry Edwards in 1880. It occurs from Kansas south to western Texas and Mexico, and west through New Mexico and Arizona into southern California and the Channel Islands, north to central Oregon.

    In addition to boring in the large tubers of manroot (there are five species of Marah in California: http://tinyurl.com/y9je2msy), the larvae are also reported from other cucurbits, including Calabazilla or Missouri gourd (Cucurbita foetidissima), coyote melon (Cucurbita palmata), and fingerleaf gourd (Cucurbita digitata). [source: The Moths of America North of Mexico, Fascicle 5.1: Sesioidea: Sesiidae, 1989, by Thomas D. Eichlin and W. Donald Duckworth]

    More images and a distribution map on the Moth Photographers Group: http://tinyurl.com/ybh9gyer

    Reply
  • Julian Donahue
    July 15, 2017 12:17 pm

    This is indeed a Glorious Squash Vine Borer, originally described from California by Henry Edwards in 1880. It occurs from Kansas south to western Texas and Mexico, and west through New Mexico and Arizona into southern California and the Channel Islands, north to central Oregon.

    In addition to boring in the large tubers of manroot (there are five species of Marah in California: http://tinyurl.com/y9je2msy), the larvae are also reported from other cucurbits, including Calabazilla or Missouri gourd (Cucurbita foetidissima), coyote melon (Cucurbita palmata), and fingerleaf gourd (Cucurbita digitata). [source: The Moths of America North of Mexico, Fascicle 5.1: Sesioidea: Sesiidae, 1989, by Thomas D. Eichlin and W. Donald Duckworth]

    More images and a distribution map on the Moth Photographers Group: http://tinyurl.com/ybh9gyer

    Reply

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