Pest description and damage Tiny (around 0.2 inch in length) drab grayish moths may be seen flying in clouds around plants. They lay eggs on leaves. The tiny leafminer eats into the leaves and feeds between the upper and lower leaf surfaces. Damage can be rather inconspicuous when damage is light. Occasionally all the leaves turn brown and the plant appears to have died; however, new leaves will eventually emerge.
Biology and life history Moths emerge in May, and immediately mate and lay eggs on leaves. Larvae feed inside the leaf; and from time to time the larvae open a small hole in the leaf and eliminate the frass from the mine. There may be more than one generation per year.
Pest monitoring Watch for clouds of adults in May to minimize damage to plants. Check plants to monitor for damage. If some damage is noted, check more frequently. This is a fairly rare insect.
Shear back plants to remove leaves when larvae are in the mines. Do not compost or the adult moths may still emerge.
Outbreaks are rare, but do occur. Usually by the time there are large numbers of leafminers, the natural enemies build up, and the population crashes. The principal enemy is a eulophid wasp, Pnigalio flavipes. Various species of spiders, Araneus diadematus, Philodromus dispar, Metaphidippus manni, and a bird, the dark eyed junco, prey on adults. Emerging adults were also trapped and killed in spittle-bug (Clastopera spp.) froth.
See Table 3 in:
Chemical Control of Landscape Pests
For more information
See "Leafminer" in:
Fasoranti, J. O. 1984. The life history and habits of a Ceanothus leafminer, Tischeria immaculata (Lepidoptera: Tischeriidae). Canadian Entomologist. 116(11): 1141-1148.
Fasoranti, J.O. 1984. Mining of Tischeria immaculata (Braun) (Lepidoptera: Tischeriidae) in the leaves of Ceanothus griseus. Journal of Economic Entomology. 77(5):1127-1129.