Holly Leafminers
INJURY:
Leaves of American
holly, inkberry and English holly are often marked with winding yellowish-brown
mines or irregular blotches. These symptoms are caused by small leaf feeding
maggots commonly called holly leaf miners. The larvae feed between upper and
lower leaf tissues producing the symptom called a leaf mine.
DESCRIPTION AND LIFE
HISTORY:
There are 3 species
which are of concern in New York.
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One is the native holly leafminer, Phytomyza ilicicola, which feeds on Ilex opaca (American holly), I. crenata (Japanese or box-leaved holly), I. acquifolium, (English, European or Oregon Holly), and related cultivars but lays its eggs only in American holly. The native holly leafminer has one generation each year and it overwinters as a larva in the leaf mine. Pupation occurs in March or April, and adults emerge starting after a few new leaves have formed. Females begin to lay eggs at about 10 days old, seeking the underside of a newly developing leaf. A tiny greenish blister appears at the ovipositon site. Larvae start by mining in a serpentine fashion, but by late winter, complete the mine as a long blotch. The second is given the name holly leafminer, Phytomyza ilicis which feeds only on Ilex aquifolium (English, Oregon or European holly). The third is Phytomyza glabricola which mines the leaves of Ilex glabra (inkberry or winterberry). The adults are tiny black flies and appear when the new leaves begin to develop in the spring. Adult females injure leaves with their ovipositors causing small holes which are punched in the leaves from which exudes sap. The sap is lapped up as food by both males and females. The hole remains in the leaf and upon healing looks like a tiny pit or pock mark When the pits are abundant, the leaf may be distorted or deformed). |
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MANAGEMENT:
Some control may be obtained by hand picking and destroying infested leaves anytime from fall until the following May.
Native holly leafminer - use a sticky trap to detect adult flies. Acephate or cyfluthrin/imidacloprid: spray in mid-May (192-298 GDD) second application in early July (1029-1266 GDD).
Holly leafminer - parasites may control this pest in some areas. This species reproduces only on Ilex aquifolium.
GDD = Growing Degree Days. Contact our office for information on how to use GDD for insect pest management.
4/98 Prepared
by: Carolyn Klass,
Sr. Extension Associate,
Department of Entomology, Cornell
University
Pesticide recommendations obtained from: Part II -- Pest Management Around the Home, 2003-2004 Pesticide Guidelines, Miscellaneous Bulletin 139S74II, 4/03, A Cornell Cooperative Extension Publication.
The Pesticide Management Education Program (PMEP), in cooperation with the New York State Department of Environmental Conservation (NYSDEC), maintains a web site with a searchable database for pesticide products currently registered in New York State. Homeowners who have Internet access can locate currently registered products at http://pmep.cce.cornell.edu/pims/current. Several different queries are available that will produce a summary for the product(s) that the system locates. If the system fails to locate the product in question, then that product is not currently registered in New York State. The database also provides a summary of important information related to every product currently registered. Two data fields "Status" and "Expiration Date" are provided in each summary. Products with a status of "Registered - Discontinued" are currently registered but will probably be discontinued for use, sale, and distribution in New York State after the date noted in the "Expiration Date" field.
This publication contains pesticide recommendations. Changes in pesticide regulations occur constantly and human errors are still possible. Some materials mentioned may no longer be available, and some uses may no longer be legal. All pesticides distributed, sold or applied in New York State must be registered with the New York State Department of Environmental Conservation (NYSDEC). Questions concerning the legality and/or registration status for pesticide use in New York State should be directed to the appropriate Cornell Cooperative Extension Specialist or your regional NYSDEC office. Read the label before applying any pesticide.
For more information contact: Tom Kowalsick, Extension Educator - Horticulture, CCE - Suffolk County
10/03
