Hosts: Black locust is preferred, but apple, birch, beech, cherry, elm, hawthorn, and oak may also be attacked.
Evidence: The overwintering flat, red and black adult beetles appear on leaves in May and those of the next generation appear in July (a). Larval feeding results in blotch mines which eventually coalesce, causing leaves to turn brown.
Life Cycle: There are two generations per year. Winter is spent as an adult in leaf litter under host trees or in bark crevices. As new leaves develop, adults emerge and lay eggs in small clusters on the undersurfaces. Newly-hatched larvae form a common mine at first, but later separate and each larva mines several leaflets before pupating inside the last mine. Adults emerge and skeletonize lower leaf surfaces before seeking overwintering sites (b).
Management: Most trees can survive continued infestations with only minor setbacks. However reduced aesthetic values is a problem. Parasites and predators can cause significant reductions in leafminer populations.
Similar Species: There are more than four additional lepidopterous leafminers which can occur on locust, but none produce the rusty-red foliage characteristic of that mined by O. dorsalis.
Figure a: E. Bradford Walker, Vermont Department of Forests, Parks and Recreation, Waterbury, VT.
Figure b: Ronald S. Kelley, Vermont Department of Forests, Parks and Recreation, Morrisville, VT.
Drooz, A.T. 1985. Insects of Eastern Forests. USDA Forest Service Miscellaneous Publication 1426. p 264;
Johnson, W.T. and Lyon, H.H. 1991. Insects That Feed on Trees and Shrubs . 2nd edition. Cornell University Press. p 190-191;
Rose, A.H. and Lindquist, O.H. 1982. Insects of Eastern Hardwood Trees. Canadian Forest Service Publication, Forestry Technical Report 29. p 265-266.