Spotted Cucumber Beetle

What it does

Adult spotted cucumber beetles chew holes in leaves, flowers, and soft fruit and are quick to fly when disturbed. As they feed they transmit plant pathogens, notably the bacteria that cause cucurbit bacterial wilt and cucumber mosaic virus, which can be more damaging than the chewing itself. The soil-dwelling larvae bore into roots, weakening or killing young plants.

Where it lives

This pest lives in vegetable gardens and field crops across the eastern, southern, and central US. Adults are found on cucurbits, beans, corn, and many flowering plants; larvae live in the soil around plant roots, especially corn. Adults overwinter in the South and migrate north each season, so northern gardens see them later in the year.

How it breeds

There are one to three generations a year depending on climate. Adults lay eggs in the soil at the base of host plants. The larvae, known as the southern corn rootworm, feed on roots for a few weeks, then pupate in the soil. New adults emerge to feed on foliage and flowers, continuing the cycle through the growing season.

What it eats

Adults feed on the leaves, flowers, pollen, and fruit of many plants, favoring cucurbits (cucumber, squash, melon, pumpkin), beans, and corn silks. Larvae feed underground on the roots of corn and other hosts. Their broad diet and disease-spreading make them a significant vegetable pest.

Identification

The adult is about a quarter inch, yellow-green, with twelve distinct black spots on the wing covers and a black head, resembling a slender, spotted relative of a ladybug. The striped cucumber beetle is similar but has black stripes instead of spots. The pale larva is thin and worm-like, found in the soil around roots.

Signs of an infestation

• Holes chewed in leaves, flowers, and cucurbit fruit
• Yellow-green, twelve-spotted beetles on plants
• Sudden wilting of cucumber or melon vines from bacterial wilt
• Poor stands and stunted corn from root-feeding larvae
• Scarring on young fruit and chewed corn silks

Prevention tips

• Use floating row covers on young cucurbits, removing them at flowering for pollination
• Choose wilt-tolerant or resistant varieties where available
• Rotate cucurbits and corn away from last year's beds
• Control weeds and clear crop debris that shelter beetles
• Use yellow sticky traps and scout early to catch infestations

Professional solutions

For gardens, cultural methods, row covers, and scouting usually suffice; because these beetles spread bacterial wilt, even modest numbers on seedlings warrant attention. For larger plantings, an advisor or licensed applicator can recommend labeled insecticides timed to protect seedlings and reduce disease spread, applied to avoid harming bees on flowering plants.