How to Identify and Control Cucumber Beetles

There are two primary types and six species of cucumber beetle in North America. Perhaps the most prolific and widespread is the striped cucumber beetle.

Measuring about one fifth of an inch in length it is a yellowish green with a yellow thorax and black head it has three black stripes running lengthwise on its wings.

A striped cucumber beetle crawls on a leaf.
The striped cucumber beetle (Acalymma vittatum) is the most common kind found in the US and is found from east coast to the Rocky mountains.

In both adult and larva stages cucumber beetles wreak havoc on cucumber plants and related crops. Damage from feeding by these beetles as well as the spread of Bacterial Wilt are the two primary problems these pests inflict.

There is no 100% guaranteed method of eradicating cucumber beetles, but preventative measures, proper garden sanitation and cultural practices can limit the damage.

Two Western Spotted Cucumber Beetles crawl along the petals of a flower.
Spotted cucumber beetles (Diabrotica undecimpunctata) are also found distributed throughout most of the US along with parts of Canada and Mexico.

Adult beetles over-winter in nearby vegetation and plant debris. Come spring you will find cucumber beetles feasting on flowering plant hosts generally outside the garden.

When cucurbits are planted cucumber beetles migrate to the crop. They feed on seedlings, mate, and lay up to 1500 eggs per female over the course of a few short weeks.

In warmer regions, up to three generations of striped cucumber beetles are produced annually, in cooler regions only two. Overwintering adult beetles feed on the cotyledons and stems of newly forming seedlings. Larvae tunnel into the ground and feed on the plant roots. As Adults they devour foliage, flowers, and stems, and mature fruit.

Healthy, fully developed, cucumber plants can withstand up to 50% defoliation before yields are drastically diminished. The transmission of bacterial wilt from a bacterium is stored in the intestinal tract of adult cucumber beetles is the greatest threat. Once a plant is infected with bacterial wilt, it spreads rapidly through the plant and its neighbors. Cucumber beetles also spread squash mosaic virus, and promote an increased occurrence of black rot, powdery mildew and fusarium wilt.

Handpicking is not always feasible in larger gardens. In small gardens, handpicking is somewhat helpful, but you have to be quick as they will fly off as you approach. Destroy adults and larvae, New adult beetles may eventually migrate to your garden, so be sure to check your plants on a regular basis.

Cucumber beetles can over-winter in plant residues both above and below the ground, it is essential to practice clean and thorough cultivation after harvests. Any diseased plant materials should be burned or otherwise discarded , but not in the compost heap.

Proven Controls for Cucumber Beetle Infestations
Mulching will not halt egg laying or feeding, but mulching with straw, hay, or plastic will help deter cucumber beetles from laying eggs near the plants as it will cut off direct access to the stem, and limit larval migration through the soil.

Traps and Trap Crops

Trap Crops in larger plantings work well in some instances. All pests have dietary preferences. By luring cucumber beetles into a concentrated area, control measures can be easily focused and damage to the main crop limited. Trap crops should be planted near the perimeter of the primary crop in multiple rows and should be planted about two weeks earlier than the primary crop in order to direct migration to the trap crop and away from the primary. Squash serves as an excellent trap crop.

Yellow Sticky Traps are yellow sticky lines of tape to trap cucumber beetles as well as other insect pests. These traps can be used in conjunction with trap crops. You can purchase them or make your own by coating a yellow plastic cup with slow drying glue. Baits such as cinnamon or allspice will act as a floral attractant.

Yellow Sticky Traps are yellow sticky lines of tape to trap cucumber beetles as well as other insect pests. These traps can be used in conjunction with trap crops. You can purchase them or make your own by coating a yellow plastic cup with slow drying glue. Baits such as cinnamon or allspice will act as a floral attractant.

The gardening classic, Carrots Love TomatoesCarrots Love Tomatoes: Secrets of Companion Planting for Successful Gardening Paperback January 2, 1998 by L.Riotte makes the following suggestion for a home made cucumber trap “You may trap cucumber beetles by filling shallow containers about three-quarters full of water into which some cooking oil has been poured.”

Companion Planting and Natural Controls

Radishes planted amongst cucumbers are proven to repel cucumber beetles. [1]. Nasturtium and Savory are also believed to repel cucumber beetles. Both would fare well planted with or near cucumber patches.

Beneficial insects such as, predatory stink bugs and Lady Bugs will help to control Cucumber beetle populations to some extent.

Organic and Eco-Friendly Pesticides

Azatin or Azadirachtin is an extract of the Neem seed, it prevents the larvae from developing normally and is also a good alternative for later larval stages. These products degenerate rapidly in nature and need to be reapplied frequently.

Bacillius thuringiensis[Bt] is highly effective against the larvae stage of Cucumber Beetles and should be applied as soon as the larvae are first noticed or suspected. Prematurely treating with Bt will diminish much of its value as more eggs continue to hatch. Larger larvae, just before pupating are not as easily controlled with Bt.

PyrethinsPyrethin insecticide against Cucumber Beetles and derivative products such as Pyola are another effective alternative to chemicals. Pyola is made from canola oil and pyrethrins, it controls many stubborn insect pests, including the Colorado potato beetle and cucumber beetle.

Spinosad , an organic pesticide, is based on a bacterium ‘Saccharopolyspora spinosa’ , which was discovered in an old Caribbean rum still. It was discovered that these bacteria produce a substance that works as a neurotoxin in many insects. Susceptible insect species exposed to spinosad become ‘intoxicated’, stop eating immediately, and die within days.