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How to Get Rid of Cucumber Beetles in the Garden

Striped cucumber beetle on a leaf

The Striped Cucumber Beetle has beautiful coloring, but it’s bad news for the gardener!

Photo Credit
Aaron Miyamoto

Learn to Identify and Prevent Cucumber Beetles

Written By: Catherine Boeckmann Executive Digital Editor and Master Gardener

Finding small striped or spotted beetles on your cucurbit crops? They could be cucumber beetles! Here’s how to identify, control, and prevent cucumber beetles in the garden.

What Are Cucumber Beetles?

If you find that the stems of your seedlings are being eaten off, leaves are yellowing and wilting, and holes are appearing, you may have a striped or spotted cucumber beetle problem.

Both the striped cucumber beetles and spotted cucumber beetle are specialists on cucurbits (cucumbers, squash, and melons). The spotted beetle is also fond of corn and grasses.

  1. Often, the beetles leave their hibernating sites in early spring and immediately begin feeding on seedlings as they emerge, usually killing them.
  2. They disappear while the female lay eggs near the base on the plants, and then the larvae feed on the roots of the host plants.
  3. As they grow into adults (mid-July to September), the beetles will once again feed heavily on the leaves, vines, flowers, and fruit, leaving deep marks in the rind.
  4. Cucumber beetles pose another threat: as adults feed, they transmit bacterial wilt or mosaic virus, which causes plants to wilt and die.

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Identification

How to Identify Cucumber Beetles

The adult striped cucumber beetle (shown in the photo above) is about a quarter of an inch long with a bright yellow abdomen, three black stripes down its wing covers, and a dark-colored head and antennae. 

Spotted cucumber beetles (shown below) are about one-third inch long, bright greenish-yellow, with 12 black spots on their wing covers. 

spotted cucumber beetle on flower
The Spotted Cucumber Beetle. Pretty and destructive. Credit: John Flannery/Wikimedia Commons

Identifying Cucumber Beetle Damage

While cucumber beetle larvae feed on cucurbit roots, adult feeding is more damaging to the crop. Adults feed on leaves and can stunt plant growth. Look for holes, yellowing, and wilting leaves. 

Feeding on flowers can reduce fruit production, and direct feeding on fruits causes unattractive scars and pock marks on the fruit, too.

Often, the cucumber beetles alone will not kill the plants or cause major damage, but the spread of disease will. Feeding by adult cucumber beetles can spread bacterial wilt disease among cucurbit plants, even when the population density of the insect is low.

Adult cucumber beetles overwinter in weeds, garden debris, and woody areas. The diseases they carry can also overwinter internally, and can be passed onto plants the next spring through fecal matter.

Striped cucumber beetles. Photo by Whitney Cranshaw, Colorado State University.
Striped cucumber beetle feeding on cucurbit leaves, which will lead to stunted plant growth and the spread of bacterial wilt. Credit: Whitney Cranshaw, Colorado State University.

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Control and Prevention

How to Get Rid of Cucumber Beetles

  • Inspect newly planted cucurbit plants for the presence of this beetle; be watchful when plants are seedlings.
  • Use yellow sticky traps to catch cucumber beetles and other pests.
  • Knock beetles to the ground and catch them with a piece of cardboard placed under the plant. Or, use a handheld vacuum to suck up the beetles. They are very hard to hand-pick, but it is easier to hand-pick them with yellow gloves coated in petroleum jelly.
  • Cover seedlings with row covers, though you must remove them during blossoming time several hours each day to allow for pollination.
  • Few insecticides can be used on cucurbit plants because they are very sensitive. They would need to be used when plants are just beginning to emerge through the soil. Please contact your local cooperative extension for a list of approved insecticides for your area.
  • Folk advice from The 1963 Old Farmer’s Almanac states that nasturtiums and wood ashes are effective against cucumber beetles.

How to Prevent Cucumber Beetles

  • If you till your garden in the late fall, you will expose cucumber beetles hiding there to harsh winter conditions and reduce their populations next year. Remove all debris after fall harvest to reduce overwintering habitat.
  • Rotate crops so cucurbit crops are not planted directly into soils containing overwintering populations.
  • Transplanting young plants rather than direct seeding can protect vulnerable seedlings from damage.
  • Planting trap crops (cucurbit varieties highly attractive to cucumber beetles) at the perimeter of the harvested crop can keep cucumber beetles from migrating into the harvested crop.
  • Where cucumber beetles are a problem, let the beetles come out of hiding and plant late. They have a knack for finding vulnerable seedlings. When yours are up and growing, the cucumber beetles will be gone, fooled into thinking you don’t have any cucumbers in your garden.
  • Natural predators include beneficial insects like braconid wasps, some nematodes, and soldier beetles.
  • Companion planting your vegetables with flowers can help to keep pests away from the plants you don’t want the beetles to attack.
  • Once the bacterial disease has entered the plant, there’s very little that you can do. If it’s bacterial wilt, you’ll see the leaves dry up, and the plant will quickly wilt and die. Take prevention for next year, as described above.

Garden Pests
About The Author
Catherine Boeckmann

Catherine Boeckmann

Executive Digital Editor and Master Gardener

Catherine Boeckmann is the Executive Digital Editor of Almanac.com, the website companion of The Old Farmer's Almanac. She covers gardening, plants, pest control, soil composition, seasonal and moon c...
Read More from Catherine Boeckmann

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Comments

<span>Patronella Sello</span> Wed, 10/19/2016 - 08:49
I planted a whole lot of mixed veggies and find that I have some black beetles with yellow and white spots eating what I suspect to be my mustard spinach. Everything else (including normal spinach) is fine. Any ideas what this is and how I can control it without harmful pesticides?
<a title="View user profile." href="/author/editors">The Editors</a> Fri, 10/21/2016 - 16:03

The only real pest mustard spinach is susceptible to is a flea beetle (there are many types, including a spotted species), which is hard to control. Protecting plants with barriers such as a row cover before infestation is the best management strategy. Before putting the garden to bed for the winter, remove all old debris from your infested plants. Since flea beetles overwinter in the soil, try hoeing and cultivating in the early spring to destroy the larvae. Add a thick layer of mulch around young plants to prevent the beetles from jumping up on to the leaves. Place some sticky traps nearby to try to capture those that persist.

 <span>Martym</span> Sat, 07/11/2015 - 13:40
I have successfully grown cucumbers for the last two years and several different varieties of them. I live in St. Louis MO. I have tried in the past and several times to grow squash, and cantaloupe and watermelon all to no avail. The pest that made me give up was not the cucumber beetle, it was a beetle that is green with black spots. Apparently they were infecting the plants with the wilt, and the plants would just die in a matter of days. I tried everything to keep them out and off the plants but they won. I no longer plant any of these plants as I was never able to get any produce. There were literally hundreds of them. My yard and garden does not have any trashy areas for them to over winter in. Since this is not the black and yellow striped cucumber beetle what is it? It is certainly as devastating as the cucumber beetle. What are these beetles and is there any way to control them?
<a title="View user profile." href="/author/editors">The Editors</a> Mon, 07/13/2015 - 16:24
  • Your plants were attacked by the spotted cucumber beetle. You can use row covers before the veggies flower to keep them away from the plants. Or you can use organic pyrethrins or organic rotenone on the plants.
 <span>Sara Gorrow</span> Mon, 07/06/2015 - 14:56
I am just finding out about these awful beetles and my garden has been established for over a month with my squash and now noticeably my cucumbers being destroyed. Are the few squash I have safe to eat? Or is it safe to say that my garden is contaminated and I need to rid of the plants? :(
<a title="View user profile." href="/author/editors">The Editors</a> Wed, 07/08/2015 - 15:34

Hi Sara,

Your squash is safe to eat. Try some of the remedies mentioned on this page to get rid of the beetles.

 <span>Jackie Mce</span> Thu, 05/07/2015 - 02:31
I tried the laundry detergent for cucumber beetles and it seems to be working. Also added beneficial nematodes the the soil hoping to kill off the larva. So far the beetles seem to be gone. In central Texas and our growing season has already started. On the look out for other pests now.
<span>Mike</span> Wed, 06/15/2016 - 11:10
I have potted zucchini on my deck. Cucumber beatles are chewing through the leaves and spreading the zucchini wilt. I tried the dish soap trick and it worked. I put a bowl like a cerial bowl down next to the pots with a couple of drops of dish soap and water. Added a few drops of yellow food coloring for color. Its been down for 2 hrs and I have 5 cucumber beatles floating dead.
<span>Errold Glw</span> Thu, 04/23/2015 - 16:47
Cukes were doing great, suddenly I noticed a tiny hole in one so I cut it open & there was a small grub looking worm inside, checked others and they also had them. Pulled all plants,SAD, my question is the potting mix also compromised, or can I start again with same potting mix?
<a title="View user profile." href="/author/editors">The Editors</a> Fri, 04/24/2015 - 10:15

These might be pickleworms (Diaphania nitidalis). They are larvae of a moth, and bore holes into cucumbers and other cucurbits. They are a tropical/subtropical insect, and overwinter in southern Florida and southern Texas. However, each season, they can appear as far north as Canada. Depending on the climate, there can be several generations per year. Certain cucumber varieties, such as 'Gemini', are more resistant to pickleworms. Early planting also helps control this pest. Check for tiny worms feeding in flowers and buds; older worms will start to bore into the fruit; stems are sometimes tunneled into as well, causing wilting. Pupae overwinter in weeds or rolled leaves; remove rolled leaves and check for eggs on vines. Some recommend covering your crop with row covers overnight, to block the nocturnal moths from laying eggs on them; remove the covers during the day to allow bee pollination.

For more information, see:

https://utextension.tennessee.edu/publications/Documents/W206.pdf

Based on what I can find, it should be OK to re-use your potting mix, as long as all infested vegetation has been removed. If you live north of Florida, the pests will be killed from cold during the winter season.