Colorado Potato Beetle - Vegetables

Adult Colorado Potato Beetle
Photo(s) copyright: Michael J. Raupp

Adult Colorado Potato Beetle - Leptinotarsa decemlineata

Back to Common Problems - Vegetables 

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.
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 (video) and adults. Most damaging when plants are young.  After defoliation is complete, stems and even potato tubers may be gnawed.
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
  1. Locate and crush eggs, larvae and adults often and early in season to effectively prevent later generations.
  2. Use floating row covers (pdf) to exclude the beetles.
  3. B.t. var. tenebrionis and spinosad are two effective "organic" insecticides.
  4. Straw and thick mulch inhibits movement and encourages predator insects.
  5. This pest prefers eggplant which can be used as trap crop.
  6. Rotate your potatoes to different parts of the garden each year. Slow-moving adults do not disperse far.
  7. Spring and fall tilling reduces populations of overwintering adults.

Photo Gallery:

Colorado potato beetle larva.
HGIC, UME

Colorado potato beetle
larva and damage. HGIC, UME

Feeding damage on eggplant
fruit

Larvae gradually become plump and change in color to pink, orange, or light tan with two rows of black spots on either side.

 

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Maintained by the IET Department of the College of Agriculture and Natural Resources. © 2017.