University of Maryland Extension

Cucumber Beetles: Spotted or Striped - Vegetables

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striped cucumber beetle
Striped adult cucumber beetle

Insects that Look Like Ladybugs on Cucumbers

Appearance

  • Eggs: Clusters of yellow to orange oval-shaped eggs are laid on or just under coarse, cracked soil.
  • Larvae: Both species are yellowish-white, 1/2" long, wormlike with dark heads.
  • Adults: Up to 1/4" long with black head. Spotted beetle is yellow-green with 12 black spots on the back. Striped beetle is yellow with three black longitudinal stripes on the back.

orange and black spotted cucumber beetle
Spotted cucumber beetle: 
Photo: Dr. Michael J. Raupp

striped cucumber beetle leaf damage
Striped cucumber beetles feeding 
on melon leaves

Life Cycle/Habits

  • Overwinter as adults in plant debris and nearby wooded areas; striped beetles may also overwinter in soil.
  • In spring, spotted cucumber beetle prefers to deposit eggs in wet, coarse soil. Striped cucumber beetle deposits eggs around the base of plants, on vines, or just below soil surface.
  • Spotted cucumber beetle larvae feed on roots, stem base, or fruit surface (thus the name "rindworm").
  • Striped cucumber beetle larvae feed mostly on roots and stems.
  • After pupating in soil, adults feed on seedlings, flower petals, leaves, and fruit.
  • Plants are generally less prone to damage after fruit set. 4-6 weeks for each lifecycle.
  • One to three generations per growing season.

Host Plants

  • Spotted: Cucurbits (i.e. cucumber, squash, pumpkin, muskmelon) legumes, tomato, ornamentals, and fruits, plus many other weeds and cultivated plants.
  • Striped: Primarily cucumbers & other cucurbits, but many other crops such as apple, pear, green beans, okra, eggplant, and potato, plus tree and shrub blossoms.

Signs/Symptoms

  • Larvae eat roots and burrow in young plant stems, causing wilt or death. 
  • Adults eat seedlings and chew holes in leaves, flowers, and fruit. Adults gouge and rasp fruit, especially smooth melons, and damage may be worse on the shaded undersides of fruit contacting soil where beetles congregate to avoid heat.
  • Spotted cucumber beetle (Southern corn rootworm) eats roots of beans and corn as well as cucurbits.
  • Both beetles are serious vectors (carriers) of plant diseases, including Fusarium wilt, mosaic viruses, muskmelon necrotic spot virus, and cucurbit bacterial wilt, although spotted beetles are considered less important vectors of this devastating disease than striped beetles.
  • Cucurbit bacterial wilt causes sudden wilt and death, mainly of cucumber and muskmelon, but also of summer squash.

damage to squash
Cucumber beetle feeding damage
on squash

damage to cucumber skin
Cucumber beetle damage
on fruit

Monitoring

  • Inspect dying seedlings for larvae.
  • Inspect chewed leaves, petals, and fruits for adults (especially leaf and fruit undersides touching soil), in flowers and at stem bases.
  • If cucumber plant wilts suddenly, check for bacterial wilt by cutting wilted stems, touching the cut ends together, and then pulling them apart slowly. Sap will string out in fine strands.

Prevention/Control

  • Prevention and early control are essential. In fall, remove garden debris (overwintering sites). In fall or spring, it can be helpful to lightly till soil to kill eggs and larvae.
  • Use floating row covers over susceptible plants until they bloom. Remove the row cover once plants bloom to allow insects in to pollinate the flowers. Control organically with: floating row cover.
  • Spray with pyrethrum, neem, or spinosad products.
  • Plant ‘County Fair’, a pickling cucumber cultivar that has natural resistance to bacterial wilt.
  • Avoid this pest by planting susceptible crops around June 15, after overwintering adults have emerged and dispersed elsewhere.
  • Handpicking is difficult because these pests are fast and drop when disturbed.

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