Colorado potato beetle
Updated: May 17, 2021
black and orange Colorado potato beetle adult
Adult Colorado Potato Beetle (Leptinotarsa decemlineata)
Photo: Dr. Michael J. Raupp
Adult spotted asparagus beetle. Credit:Whitney Cranshaw, Colorado State University, Bugwood.org
Colorado potato beetle larva and fecal pellets

Appearance

  • Eggs: Orange ovals attached on end on the lower surface of leaves, in rowed clusters of about 20-60.
  • Larvae: Plump, brick red, humpbacked grubs turning orange, pink or tan; with black head and legs, and 2 rows of black spots along each side.
  • Adults: Hefty, oval-shaped, and humpbacked with a hard shell, 1/3" long. Color is principally yellow, with ten lengthwise black stripes on the wings, and black markings on the reddish head and thorax.
Colorado potato beetle laying eggs
Colorado potato beetle and eggs

Life cycle/habits 

  • Adults overwinter below the soil surface near host plants and emerge in late April-early May.
  • Eggs are laid under potato and tomato leaves (about the time potato shoots are emerging).
  • Both larvae and adults feed on leaves and fruit. After four instars, larvae pupate in the soil.
  • Two damaging generations yearly.

Host plants

  • Eggplant is a favorite. Also eats potato, pepper, tomato, and other solanaceous plants.

Signs/symptoms

  • Chewing of leaves, terminals, and fruit by larvae and adults. Most damaging when plants are young.  After defoliation is complete, stems and even potato tubers may be gnawed.
  • Damaged eggplant from Colorado potato beetle feeding

    eggplant with holes damaged by Colorado potato beetle

Monitoring

  • Watch for the clusters of small orange eggs laid on leaf undersides. This occurs soon after potato shoots emerge from planted seed pieces. Feeding damage will be quickly evident.
  • Slow-moving adults and congregating larvae are easily spotted.
  • Defoliation greater than 20% will reduce yields.

Prevention/control

  • Locate and crush eggs, larvae, and adults often and early in season to effectively prevent later generations. Slow-moving adults do not disperse far.
  • Use floating row covers to exclude the beetles.
  • Spinosad and neem products are effective organic insecticides for controlling larval stages.
  • Straw and thick mulch inhibits movement and encourages predator insects.
  • This pest prefers eggplant which can be used as a trap crop.
  • Rotate your potatoes to different parts of the garden each year. 
  • Spring and fall tilling reduces populations of overwintering adults.