The daylily leafminer, Ophiomyia kwansonis, is a new pest causing severe damage to daylilies in nurseries and landscapes. It was likely introduced in 2006 from Japan and has spread rapidly throughout much of the Eastern United States. There currently are no trial-based recommendations to help growers, landscapers, and homeowners manage this pest.
Daylily leafminer is a fly in the family agromizidae. Larvae feed within leaves and create
meandering, white mines that are roughly parallel with leaf veins. They pupate in leaves or at the base of plants before adult flies emerge. There are at least two generations per year in Maryland and probably more in warm southern states.
Damage caused by daylily leafminers do not kill plants but do have costs for nursery and landscape professionals. Infested plants are not marketable by nurseries and retail garden centers. In landscapes infested plants are unattractive and cause landscape clients to become unsatisfied. Homeowners also find the damage objectionable and may spend money trying to find effective insecticides.
There are a number of insecticides available that target leafminer flies but none have been tested on this pest. In addition, we know almost nothing about the biology of this pest including when it oviposits in the spring and how many generations it has. With funding from the American Hemerocallis Society we are investigating the seasonal activity of daylily leafminers and insecticide treatments to reduce plant damage. Our goals are to improve monitoring and IPM of this new pest for homeowners, landscapers, and nursery operators.
Read more in this American Nurseryman article.