Issue 11, July 11, 2016
Daylily leafminer, Ophiomyia kwansonis, is being found in many areas of Illinois. This Asian native was first detected in Florida in 2011 and has since spread through much of the U.S., apparently by the movement of infested plants.
The adult agromyzid fly is somewhat rotund, black and about one-tenth inch long. Adult flies are commonly seen in daylily blossoms. Eggs hatch into larvae that tunnel in the leaves. The larval trails are silver-white and slender. After tunneling for a few inches, the mature, light yellow, three-sixteenth inch larva pupates in an oval, brown area of the leaf. The adult fly emerges within a few days. There are two to three generations per year.
Damage is limited to the white, meandering trails in the leaves, causing slight aesthetic injury. Control is primarily by removing infested leaves, but this leaf removal is considered to be more damaging to plant health than is the leafminer.
Daylily leafminer damage.
Although this is an exotic, invasive insect, it does not cause enough damage to warrant insecticidal control. Naturally-occurring predatory and parasitic insects provide some control. (Phil Nixon)