Cucumber Beetle, Spotted

Diabrotica undecimpunctata

Spotted cucumber beetle
Spotted cucumber beetle [Credit: Austin Turner]
Spotted cucumber beetle [Credit: Austin Turner]


Host Plants:

On Crops: Cucumbers, melons, squash, corn

Where Found:

North America and parts of Mexico

Description:

Spotted cucumber beetles are about 1/3 inch long and are a bright greenish-yellow with 12 black spots on their wing covers.

Damage:

In spring, spotted cucumber beetles often can be seen on squash and cucumber seedlings, and then they disappear for a few weeks. During this time new larvae are feeding on the roots of grasses, including corn. A second generation emerges in midsummer and the adults feed heavily on the flowers, fruits and roots of cucumber family crops and corn. As they feed, the beetles transmit viral diseases and bacterial wilt, which causes plants to wilt and die.

Preventing Problems:

Plants including buckwheat, borage, catnip and radishes attract numerous beneficial that can help control cucumber beetles. Floating row covers are the most dependable way to protect plants. Delaying spring planting by two weeks can often help with cucumber beetles management. Use yellow sticky traps to monitor populations.

Managing Outbreaks:

Spotted cucumber beetles are difficult to hand pick because they are small and prone to flying away. On cool mornings, place a piece of cardboard beneath plants to catch beetles you knock to the ground. You can also coat the fingertips of a yellow rubber glove with petroleum jelly to make it easier to collect any beetles clustered in blossoms. A small vacuum is a good way to collect cucumber beetles.

Tips:

Most conventionally grown cucumbers and melons are grown with dangerous systemic pesticides, so organic pest control is worth the time and effort. You can also try growing varieties like ‘Little Leaf’ or Asian cucumbers, which lack the bitter gene and are less attractive to the cucumber beetles.

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