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Ministry of Agriculture, Food and Rural Affairs

LEAFMINERS (BLOTCH AND SERPENTINE)

Blotch leafminer early and later blotches Blotch leafminer on Virginia creeper in vineyards Blotch leafminer larva in mine Blotch leafminer inside leaf shield Serpentine leafminer Click to enlarge.

Beginner

Scientific Name
          Antispilla viticordifoliella(Blotch leafminer)
          Diptera spp. (Serpentine leafminer)

Identification
Blotch leafminer
Adults

  • Very small blackish-brown moths with metallic markings

Larvae

  • Yellowish white caterpillars
  • Feed between upper and lower epidermis

Injury

  • Large tan blotches containing dark spots (frass)
  • Shield-shaped hole

Serpentine leafminer
Adults

  • Small, measuring less than 2 mm in length

Larvae

  • Legless maggot
  • Initially transparent becoming yellowish orange in later instars

Damage

  • Winding mines between upper and lower epidermis across the leaf

Often Confused With
Black rot foliar lesion – black fruiting bodies within lesion

Scouting Notes
Injury usually appears after bloom.

Threshold
None.

Advanced

Scientific Names
Antispila viticordifoliella (blotch leafminer) and Diptera spp. (serpentine leafminer)

Identification
Blotch leafminer
Adults

  • Very small blackish-brown moths with metallic markings

Larvae

  • Yellowish white caterpillars
  • Feed between upper and lower epidermis

Injury

  • Large tan blotches containing dark spots (frass)
  • Shield-shaped hole

Serpentine leafminer
Adults

  • Small, measuring less than 2 mm in length

Larvae

  • Legless maggot
  • Initially transparent becoming yellowish orange in later instars

Damage

  • Winding mines between upper and lower epidermis across the leaf

Often Confused With
Black rot foliar lesion – black fruiting bodies within lesion

Biology
Both leafminer insects pupate in the soil beneath the grapevine.  In both cases, the female lays the egg under the skin of the leaf and when the larva hatches, it feed on the green, photosynthetic layers of the leaf. The larvae feed between the upper and lower leaf surfaces. As the larva feeds, it deposits frass inside the mine, which appears dark.
When the blotch leafminer is fully developed and ready to pupate it cuts a semicircular slit in the leaf surface, usually at or near the end of the mine. This slit may be located on the upper or lower leaf surface, but depends on the mining location of the larva within the leaf tissue.  The number of generations of blotch leafminer is not known.

When the serpentine leafminer larva is fully developed, it pupates within the area of the leaf where it has been feeding; this section eventually falls out, leaving a hole in the leaf. There are two generations per year.

Scouting Notes
Injury usually appears after bloom.

Threshold
None.

Management Notes
The grape leaf miner is not an economically important insect; however, small numbers usually occur in vineyards.