While on a garden tour in Tyler, TX this week, Smith County Horticulture Agent Keith Hansen was alerted to a new pest of lilies in town. Some visiting Louisiana scientists pointed out signs of the daylily leafminer, Ophiomyia kwansonis, on daylilies in the Tyler Rose Garden. This new invasive leafminer fly was first confirmed in 2011 from Apopka, Florida during a nursery inspection, though daylily growers and collectors were aware of unusual leafminer damage since at least 2008, and the first possible picture of it was reported from Maine on Bugguide in 2006. It has since been reported from 13 states, mostly along the Gulf and Atlantic seaboards.
This small, shiny black fly is native to Japan and Taiwan. It’s presence is identified by long, gently meandering leaf mines in daylily leaf blades, especially on the upper leaf surfaces. The damage is caused by a small, yellowish maggot (up to 5 mm-long) burrowing through leaf tissue.
This pest is not reported to kill daylilies, though heavily attacked plants retain their damaged and much disfigured leaves, until removed or replaced by new growth.
To all you daylily growers and afficionados, my condolences. Little is currently known about insecticidal control, though some control may be achieved by removing and destroying infested leaves as they appear. More information is available at the American Horticulture Society.
Although this leafminer has already been reported from Texas, this was the first time I was aware of it. If you are noticing the characteristic signs of damage, Gayle Williams of the Maryland Department of Agriculture is tracking the spread of this pest. You can send images and information to her at her email per the article on page 8 in the NPDN newsletter. If you think you’ve seen this pest in Texas, you can comment to this post also. And thanks to Keith Hansen for this heads up.