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| Native
Holly Leafminer Phytomyza ilicicola Loew |
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Ornamental plantings of holly, Ilex spp., in Pennsylvania are often damaged by leafmining pests. One species is the native holly leafminer that only feeds on the foliage of American holly, Ilex opaca, and its cultivars. Other leafminers of plants in the genus Ilex include the holly leafminer, P. ilicis Curtis, a European species that feeds primarily on English holly, I. aquifolium. Additionally, the “inkberry leafminer”, P. glabricola, infests inkberry, I. glabra. The information contained in this fact sheet pertains to the native holly leafminer. |
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| Description | |
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Eggs hatch into tiny maggots or larvae within the leaf mine. The larvae are yellow and when fully grown are 1.5 mm long. The larval stage of the European species, holly leafminer, resembles the native holly leafminer. Adults are small, 0.8 mm-1.6 mm long, black flies. |
Figure 1. Serpentine
blotch |
| Life History | |
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This species overwinters as larvae within the leaf mine. In some cases 12 or more larvae have been found in an individual leaf, but the average number found in a leaf is three. During the spring these maggots pupate. Adults emerge from leaves in May, mate, and females deposit eggs in small slits on the underside of newly developing leaves. The eggs hatch into larvae that start to feed, creating new leaf mines. There is only one generation produced each year. |
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| Damage | |
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American holly foliage is damaged by the feeding activity of larvae that destroy leaf tissue between the upper and lower leaf surfaces. Damage first shows up as slender leaf mines that are seldom over 1.3 cm in length. With continuous feeding, leaf mines broaden and leaves become marred with yellow serpentine or blotch mines (Fig. 1). Heavily infested plants may prematurely drop their leaves and be almost devoid of leaves until new growth begins the following spring. Females may damage foliage
by inserting their ovipositors into leaves. The female jabs the leaf
with her ovipositor and plant fluid starts to flow from this wound.
Both females and males feed on the plant fluid that exudes from the
wound. Leaves seriously damaged by these ovipositor punctures often
become stunted and badly distorted. Be careful not to confuse this type
of damage with leaves mechanically injured by overlapping holly leaf
spines. |
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| Management | |
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Infested holly leaves may drop to the ground before adults emerge. Leaves that have dropped prematurely should be gathered and destroyed. This helps reduce adult populations that may attack host plants in the spring. Registered insecticides should be applied according to label directions to the foliage in early May. Registered systemic insecticide formulations may also be effective against this pest when applied according to label directions as soil injections early in the growing season. When using these insecticides be sure adequate soil moisture exists so that optimal uptake of these products is achieved. |
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| Warning | |
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Authored
by: Gregory A. Hoover ©
The Pennsylvania State University 2003
This publication is available in alternative media on request. Penn State is committed to affirmative action, equal opportunity, and the diversity of its workforce. Return to Entomological Notes Listing Home
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