University of Maryland Extension

Potato Tuberworms - Vegetables

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tuberworms inside a potato
Potato tuberworm inside a potato

Appearance

  • Potato tuberworms are the larvae of an inconspicuous moth.
  • Pink to white larvae reach ¾ inch in length and feed between leaf surfaces (leaf mining injury) and tunnel into stems. 

Life Cycle/Habits

  • The adult lays eggs on the foliage, and the larvae mine leaves (feed between leaf surfaces) and bore into stems.
  • Foliar damage is usually minor.
  • Larvae drop to the soil and find their way to poorly covered tubers. They then bore deep tunnels that are usually filled with black fecal material and fungi. 
  • Tuberworm overwinters as a pupa in plant residues.
  • Adult moths emerge in the spring and eggs are laid on the undersides of host plants. 
  • Later generations of eggs are laid on the eyes of poorly covered potato tubers that larvae tunnel into.
  • Hot, dry weather favors this pest.

Host Plants

  • Potato leaves (they may also attack other members of this family- tomato, eggplant, pepper).

Signs/Symptoms

  • The adult lays eggs on the foliage, and the larvae mine leaves (feed between leaf surfaces) and bore into stems.
  • Foliar damage is usually minor.

Prevention/Control

  • Use floating row cover to protect foliage from egg-laying adults.
  • Keep tubers covered by two inches or more of soil to keep larvae from reaching tubers.
  • Incorporate organic matter and use thick heavy mulches to interfere with pest movement and egg laying.
  • Monitor plants for signs of this pest and remove those that are infested.
  • Clean up all plant residues at the end of the season.

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