Hosts:  Ponderosa pine and piñon

Symptoms/Signs:  Adults of pine-feeding needleminers are small, narrow-winged, mottled, silvery-gray moths with a wingspan of about 10 mm. Eggs are too small, 0.2 mm in diameter, to be noticeable. Larvae are brown, 8 mm long when fully developed, and usually found mining within current year’s needles. The pupae are elongate, cylindrical black, and about 6 mm long. Needles inhabited by third and fourth instar larvae turn a faded yellow-brown in color and have several tiny holes in them for frass disposal and larval exit.

Biology:  Adult moths emerge and fly in June and July. Eggs are laid inside previously mined needles. Larvae begin hatching in July, crawl to and mine into previously uninfested needles and overwinter. Pupation occurs in late spring.

Effects:  Persistent infestations can cause severe discoloration, defoliation, and reduced growth of stems, shoots, and needles.

Similar Insects and Diseases: Similar symptoms, i.e., discoloration and defoliation, can result from scale insects, aphids, and needle cast diseases.  However, only the needleminers leave telltale holes in the mined needles.

References:  23, 96