Lyonetia Leafminer, Lyonetia speculella Clemens

I. Introduction: Although first reported from apple in the 1920's, this is a relatively new leafminer pest on apple in the mid-Atlantic region, first noticed as a common leafminer in the early 1980's in Virginia and West Virginia. Mining activity is restricted to young leaves; it is therefore more common on young, non-bearing trees since all leaves are succulent and vigorous.

II. Hosts: Apple, plum, cherry, birch and grape.

III. Description: Adults are about the same size as the moths of spotted tentiform leafminer, but are predominantly silver-gray in color with white bands on the wings (Plate 54). There is a tuft of upward-projecting scales on the top of the head. Larvae are pale green in color, and may be seen descending on a strand of silk to a new leaf.

IV. Biology: The life history of this species is poorly known and is the subject of research in our region. Adults overwinter. Eggs are laid in the undersides of expanding leaves. Mines begin as narrow, winding, serpentine paths that turn into broad, irregular brown blotches. Clumps of black frass may be seen hanging from holes in the mines. Larvae may leave the mine and start a new mine, sometimes on a different leaf. This is important since more than 60 mines may be initiated on a single leaf; successful development of this many larvae in one leaf is unlikely. Larvae leave the leaf for pupation, which occurs in a silken "hammock" spun by the larva on the underside of the leaf (Plate 55). There are probably 4-6 generations per season, the first occurring in April. The first generation is usually in very low densities. By midsummer, there is considerable overlap of generations and all growth stages may be found at any time.

V. Injury: Mines are the most visible evidence of this species (Plate 56). Several mines may overlap on a leaf, turning the whole leaf brown. Most injury is done from mid-late summer, and may be a problem in non-bearing trees, where a great proportion of leaves are susceptible to attack.

VI. Monitoring: Watch for the presence of young mines on young leaves, mainly on nonbearing trees. No thresholds are currently available.

This is taken primarily from a chapter by D.G. Pfeiffer, L.A. Hull, D.J. Biddinger, & J.C. Killian on apple indirect pests, reprinted with permission from Mid-Atlantic Orchard Monitoring Guide, published by NRAES, 152 Riley-Robb Hall, Ithaca, New York 14853-5701.
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