Native Holly Leafminer Fact Sheet

Fact Sheets > Insect Fact Sheets > Native Holly Leafminer

  The Native Holly Leafminer, Phytomyza ilicicola (Loew), as its name implies, is indigenous to the United States. It damages host plants by feeding on the leaf tissue between the upper and lower leaf surfaces with heavy infestations resulting in premature leaf drop.

Plants Attacked

The native holly leafminer feeds on American Holly (Ilex opaca), Japanese Holly (Ilex crenata), and related cultivars, but lays its eggs only in American Holly.

Insect Identification

The tiny, white, oval egg is laid in the newly emerging foliage. The larva (or maggot) is yellow and legless, and the pupa is oval and a reddish-brown color. The adult is a black and gray fly.

Pupal stage found just below the leaf surface	Native holly leafminer adult

Life History

Winter	Larvae over-winter in the leaf mines.
Spring	The larvae pupate in late March or early April. The adult flies emerge over a six-week period beginning when newly developed leaves appear on the holly in early May.
Summer	After mating, the female fly lays her eggs by piercing the underside of the leaf with her ovipositor and placing the eggs in the mesophyll. When the eggs hatch, the larvae feed, creating new mines.
There is one generation each year in Pennsylvania.

Damage Symptoms

The larvae feed so slowly that the damage may initially go unnoticed. At first, damage appears as a dark brown spot on the leaf, but as further feeding occurs, this turns into a long blotch by late winter. A heavy infestation may result in the majority of leaves being mined. Prior to egg laying, the adult female stabs the leaf with her ovipositor and both male and female adults feed on the sap that flows from the wound. This action leaves several small puncture wounds in the developing foliage.

Mines on the leaf of American Holly	Puncture wounds made by female ovipositor

Management Options

Mechanical	Reduction of potential populations can be achieved if affected leaves that drop to the ground are collected and destroyed before the eggs hatch.
Chemical	Registered insecticides should be applied in early May. Control Measures for Native Holly Leafminer

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Authored by:
Katherine Mazzey, Penn State Extension Program Assistant
Michael Masiuk, Extension Agent, Penn State University - Allegheny County

Sources
Center for Integrated Pest Management. North Carolina State University. Native Holly Leafminer http://ipm.ncsu.edu/AG189/html/Native_Holly_Leafminer.HTML

Cornell Cooperative Extension (1998). Native Holly Leafminer. http://www.cce.cornell.edu/factsheets/pest-fact-sheets/leaf-miners.html

Hoover, G.A. (2000). Woody Ornamental Insect, Mite, and Disease Management. Penn State College of Agricultural Sciences. pp.34. http://woodypestguide.cas.psu.edu/Insects.html

Hoover, G.A. (2003). Native Holly Leafminer. Department of Entomology. Penn State. http://www.ento.psu.edu/extension/factsheets/nHollyLeafminer.htm

Johnson, W.T. & Lyon, H.H. (1976). Insects That Feed On Trees And Shrubs, pp.206. Comstock Publishing Associates. Cornell University Press.

Klass C. (1998). Native Holly Leafminer. Cornell University. Department of Entomology. http://www.cce.cornell.edu/suffolk/grownet/tree-insect/hollylm.html