Cucumber Beetles

Also referred to as: Spotted Cucumber Beetles, Striped cucumber beetles, western striped cucumber beetle, southern corn rootworm, Western corn rootworm beetles

Acalymma spp., Diabrotica undecimpunctata

Physical Description:

Light green to yellow little beetles with stripes or spots (very much like a ladybug, but with yellow-green instead of red background). Striped cucumber beetles can overwinter in most parts of the US & Canada. A similar species, the western striped cucumber beetle is only found in the western states. It will feed on snap bean pods as well as seedlings of a variety of crops. The larval stage of the spotted cucumber beetle is the southern corn rootworm, which can cause serious damage to corn crops. Western corn rootworm beetles look similar to cucumber beetles but have yellow abdomens and shorter stripes on the wings.


Adults

  • Adult Striped Cucumber Beetles are 1/4″ long, yellow with black heads and three black stripes down the back and rows of tiny indentations on the wing covers (RVGPS-159)
  • Spotted Cucumber Beetles are 1/4″ long, yellow-green with black heads and 12 black spots on their wings. (RVGPS-159)
  • Light green or yellow beetles that look like ladybugs

Larvae

RVGPS-159: white, wormlike grubs with dark heads and tails, up to 3/4″ long.

Eggs

RVGPS-159: laid in the soil, often at the base of a plant.

Life Cycle:

RVGPS-158: eggs are laid in cracks in the soil near the base of a plant; wormlike-larvae hatch 1-2 weeks later and feed on crop roots. After 1-month, the larvae pupate. 1st generation is usually at adult stage when cucumber seeds are just germinating. The 2nd generation comes along at about midsummer.There will be 1-3 overlapping generations each year, with the 1st one doing the most damage, when the plants are young. Spotted cucumber beetles survive winter only in the south, but they migrate north in plenty of time to become a problem for the northern gardeners also. The larval stage o fthe spotted cucumber beetle is the southern corn rootworm, which can cause serious damage to corn crops.

Range:

Striped Cucumber Beetle:

RVGPS-158: throughout US, except for the far west; also central and eastern Canada.

Western Striped Cucumber Beetle:

RVGPS-158: west of the Rockies

Spotted Cucumber Beetle:

RVGPS-158: throughout US, and in Canada from east of the Rockies into Quebec.

Plants affected

  • Cucumbers
  • Melons
  • Winter Squash
  • Watermelons
  • corn
  • occasionally other crops
  • Potatoes
  • Hibiscus
  • Cabbages

How to Spot Them

Where

RVGPS-158: underside of cotyledons (seedlings), leaves, along the stems, and inside the blossoms, because they prefer shaded spots.

Damage

Whole Plant

RVGPS-158: young seedlings may die quickly from being eaten. Inspect squash-family seedlings frequently,

RVGPS-159: bacterial wilt and/or mosaic virus will cause the whole plant to wilt. These diseases can kill the vines later in the season.

Leaves

  • holes are chewed through leaves, often leaving veins still attached
  • medium to large holes in leaves
  • tiny black specks of poop around the hole
  • often don’t chew clean holes, leaving bits of veins connected

Flowers

holes chewed through petals

Roots

usually the damage the larvae do won’t be noticed, unless it’s a small seedling that dies. if you pull up the plant you will probably find little larvae.

Fruit

RVGPS-159: fruit laying on the earth may get drilled into by the larvae.

Control Methods

Timing

RVGPS-159: if your season is long enough, you can plant after the first generation is done.

Row Covers

RVGPS-159: cover and seal until flowering time

Sticky Traps

RVGPS-159: attracted to yellow

Garden Cleanup

RVGPS-159: remove all crop debris or dig it into the soil to destroy overwintering sites for adults

Fall Cultivation

RVGPS-159: turn soil just before frost where squash-family crops grew

Kaolin Clay

RVGPS-159: spray up to twice per week, especially under leaves to deter them. Reapply after heavy rains.

Handpicking

RVGPS-159: as often as possible

Vacuuming

RVGPS-159: use a hand-held vacuum to pick up the beetles, then kill them.

Trellising

RVGPS-159: trellising the plants makes it easier to monitor & handpick.

Trap Crops

RVGPS-159: planting an early squash crop to attract beetles, then killing them all before the real crop goes in works for larger-scale gardening.

Drenching Soil with Nematodes

RVGPS-159: applying Heterorhabditis nematodes to the soil helps kill the larvae.

Pyrethrins

RVGPS-159: last resort. limit spray to the plants you know are infested.

Sources:

  • RVGPS

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