Cucumber Beetle: All You Need to Know for a Healthy Garden

Cucumber beetles are a common pest that can cause significant damage to vine crops such as cucumbers, squash, pumpkins, and watermelons. These beetles can affect the roots, leaves, flowers, and fruits of these plants, and even interfere with pollination, leading to reduced fruit sets [1(https://hort.extension.wisc.edu/articles/cucumber-beetles/).

There are two main types of cucumber beetles: the striped cucumber beetle and the spotted cucumber beetle. The striped cucumber beetle has three black stripes on its wings, while the spotted cucumber beetle has 12 black spots 2. Both types have similar life cycles and feeding habits, with larvae feeding on plant roots and stems, and adults feasting on seedlings, flower petals, and leaves 3.

Managing cucumber beetles can be done through various approaches, including the use of kaolin clay, which creates a gummy coating on the beetles’ antennae, making it difficult for them to navigate. However, it’s important to note that kaolin clay will not kill cucumber beetles 4.

Cucumber Beetle Identification

Striped Cucumber Beetle

The striped cucumber beetle (Acalymma vittatum) is a common garden pest often found attacking cucurbits, such as cucumbers, melons, and squash1. These beetles are characterized by:

  • Size: approximately 1/5 inch long
  • Color: yellow with three distinct black stripes running down their wing covers
  • Antennae: reddish-brown in color

Striped cucumber beetles can cause damage by feeding on the foliage, flowers, and fruit of host plants2. Additionally, they can transmit bacterial wilt, leading to plants wilting and dying3.

Spotted Cucumber Beetle

The spotted cucumber beetle (Diabrotica undecimpunctata howardi) is similar in size and shape to the striped cucumber beetle4. Here are some distinguishing features:

  • Size: about 1/5 to 1/4 inch long
  • Color: yellow with 12 black spots on their wing covers
  • Antennae: also reddish-brown in color

This beetle causes damage by feeding on roots, stems, and fruits and can potentially transmit plant diseases5.

Comparison

Feature Striped Cucumber Beetle Spotted Cucumber Beetle
Size Approximately 1/5 inch long 1/5 to 1/4 inch long
Color Yellow with black stripes Yellow with black spots
Antennae color Reddish-brown Reddish-brown
Feeding habits Foliage, flowers, and fruit Roots, stems, and fruit

Life Cycle and Behavior

Egg

  • Cucumber beetles lay eggs in soil or near plant stems
  • Pale orange-yellow in color
  • Egg-laying occurs mostly during late summer

Cucumber beetles, both striped and spotted species, lay their eggs in the soil or close to the base of plants. The eggs are pale orange-yellow and are usually laid during late summer.

Larva

  • Feed on roots and stem base
  • Creamy white color
  • Grow up to 3/8 inches in length

The larvae, also known as rootworms, hatch from the eggs and feed on the roots and stems of plants. They are small, with a creamy white color and grow up to 3/8 inches in length.

Adult

Striped Cucumber Beetle:

  • Yellowish-green color
  • Three black stripes on wing covers
  • About 1/5-inch long

Spotted Cucumber Beetle:

  • Yellowish-green color
  • 12 black spots on wing covers
  • Similar size and shape as striped cucumber beetle

Comparison table:

Striped Cucumber Beetle Spotted Cucumber Beetle
Three black stripes 12 black spots
Yellowish-green color Yellowish-green color
About 1/5-inch long Similar size and shape

The adult beetles emerge after the larval stage and feed on plant foliage, flowers, and seedlings. There are two main types of cucumber beetles: striped and spotted. Striped cucumber beetles have three black stripes on their wing covers, while spotted cucumber beetles have 12 black spots. Both types of beetles are yellowish-green in color and about the same size.

Adult cucumber beetles overwinter in plant debris, becoming active again in the warmer months. They mate and lay eggs, completing their life cycle. The adult beetles can cause significant damage to cucurbit plants, such as cucumbers, squash, and melons, making their management crucial for maintaining healthy gardens and crops.

Damage to Cucurbits

Cucumbers

Cucumber beetles (Acalymma vittatum) cause significant damage to cucumbers by feeding on their leaves, blossoms, and stems. They also transmit bacterial wilt, a disease that leads to plant death. Common signs of damage include:

  • Holes in leaves
  • Yellowing or wilting leaves
  • Stunted growth

Squash

Squash plants are particularly susceptible to damage from both spotted and striped cucumber beetles. A successful control method involves planting Blue Hubbard squash, which acts as a trap crop by attracting beetles, saving the main squash plants from infestation. For example:

  • For a small garden with 100 cucurbit plants: plant 6-8 Blue Hubbard squash plants
  • For a small farm with plastic mulch and drip irrigation: transplant 2-4 Blue Hubbard squash seedlings

Melons

Cucumber beetles prefer melons over other cucurbits. They feed on leaves, fruit, stems, and can transmit diseases like bacterial wilt and cucumber mosaic virus. The result is:

  • Misshapen or discolored fruit
  • Premature fruit drop
  • Plant death

Pumpkins

Pumpkins are also at risk when infested with cucumber beetles. Similar to other cucurbits, the damage includes leaf feeding, wilt transmission, and reduced yield. Common symptoms on pumpkins are:

  • Holes in leaves and stems
  • Diseased plants
  • Reduced fruit quality

Corn

While corn is not a cucurbit, it can also be damaged by cucumber beetles. The beetles feed on corn seedlings, transmit bacterial wilt, and cause problems like:

  • Stunted growth
  • Severely damaged leaves
  • Reduced yield
Cucurbit Type Damage Symptoms/Disease
Cucumbers Leaf, stem, fruit Holes in leaves, yellowing, wilting, bacterial wilt
Squash Leaves, stems Attracts beetles, managed with trap crop
Melons Leaves, fruit, stems Misshapen or discolored fruit, premature drop, diseases
Pumpkins Leaf, stem, fruit Holes, wilt, reduced quality
Corn Leaf, seedlings Stunted growth, damaged leaves, reduced yield

Footnotes

  1. Striped Cucumber Beetle [fact sheet] | Extension

  2. Cucumber Beetles | Extension | West Virginia University

  3. Cucumber Beetles in home gardens | UMN Extension

  4. Cucumber Beetles: Spotted or Striped on Vegetables

  5. Banded Cucumber Beetle – Texas A&M University

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 – Spotted Cucumber Beetle

 

Green lady bug??
Location: southern indiana
November 15, 2011 11:20 pm
Is this a green lady bug I found today ? It looks just like them but it’s green . Thank you
Signature: brian

Spotted Cucumber Beetle

Dear Brian,
Though it superficially resembles a ladybug, this is actually a Spotted Cucumber Beetle,
Diabrotica undecimpunctata, and you may verify that on BugGuide.

Letter 2 – Spotted Cucumber Beetle?

 

I’ve been watching an insect in my sun garden for two days now. It looks a bit like a lady beetle or lady beetle larva, but the head seems different – just small and black – no big platey head with white patches – and it has very long antennae. Also, it is yellow. It has eleven black spots – a row of three near the head, the middle spot being in a “v” shape, and then two rows of four. Can you please tell me what it is? Sorry that I don’t have a camera good enough at closeups to photograph it for you (if you can recommend a good digital camera for photographing insects and flowers, please let me know – I am thinking of requesting that from hubby for Christmas…).
Thanks, and I love your site!!
Julia

Hi Julia,
It sounds like a Spotted Cucumber Beetle, Diabrotica undecimpunctata howardi. Here is a photo I downloaded from this site which has lots of information on this garden pest.

That’s it! That’s it! Thanks! Julia

Letter 3 – Spotted Cucumber Beetle

 

cucumber beetle
Location: Bronx, NY
October 10, 2011 1:21 pm
Didn’t know what this was till I came across it on your site. This one’s reading the nutrition info on a can of nuts 🙂
Signature: Robbie R.

Spotted Cucumber Beetle

Hi Robbie,
Thanks so much for resending this image of a Spotted Cucumber Beetle using our standard form.  Now all the information we require is formatted properly for posting.  This is a particularly amusing photo to us.  If we ever decide to create another calendar, this is the type of photo we like to use:  high quality and just quirky enough to never appear in an reputable identification guide. 

Letter 4 – Spotted Cucumber Beetle

 

Subject: Beetle ID?
Location: San Jose CA
May 23, 2013 6:38 pm
Hi,
curious what this beetle is!
Photographed 5/23/13, they spend time between rose petals and inside rose blossom.
Thanks!
Signature: Frank

Spotted Cucumber Beetle
Spotted Cucumber Beetle

Hi Frank,
These are excellent images of a Spotted Cucumber Beetle,
Diabrotica undecimpunctata.  According to BugGuide:  “Larvae feed on roots of a wide range of plants, including many field crops” and “Considered a major pest of many field crops including cucumbers and other squashes, corn, soy. Beetles also transmit crop diseases such as bacterial wilt. Adults also reported damaging to garden plants including hibiscus, roses.”  Since you have adults in the roses, perhaps you also grow vegetables that serve as the larval food plant.

Spotted Cucumber Beetle
Spotted Cucumber Beetle


Letter 5 – Spotted Cucumber Beetle

 

Subject: ID this bug?
Location: Union City, NJ
September 15, 2016 5:26 am
Thanks for your help!
Signature: CC

Spotted Cucumber Beetle
Spotted Cucumber Beetle

Dear CC,
We believe that if you look at images posted to BugGuide, you will agree that this is a Spotted Cucumber Beetle,
Diabrotica undecimpunctata.  BugGuide remarks:  “Considered a major pest of many field crops including cucumbers and other squashes, corn, soy. Beetles also transmit crop diseases such as bacterial wilt. Adults also reported damaging to garden plants including hibiscus, roses.”

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    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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