American Nurseryman -Jan 2012

Daylily leafminer recently detected in U S The daylily leafminer Ophiomyia kwansonis Sasakawa was newly identifi ed in the U S last autumn and growers should be aware that the pest has the potential to spread considerably This insect known previously only from Japan and Taiwan has been confi rmed by specimens in Florida Maryland Mississippi Pennsylvania Tennessee and Virginia It has also been diagnosed in Alabama Georgia Louisiana North Carolina New York South Carolina and Texas Presence of the pest is evidenced by the unique mining damage in Hemerocallis leaves The list of confi rmations likely will increase with grower awareness Possibly the earliest U S documentation is an image taken on July 4 2006 in Kennebunk Maine photo top right Then in 2008 damage was fi rst noted by daylily enthusiasts at a national meeting in Texas Some returned home to fi nd it in their own plantings The small up to 5 mm yellow maggot larvae feed only in leaves of Hemerocallis species and their cultivars mining up and down as they feed between the leaf surfaces leaving obvious silver tunnels that persist until leaves senesce or are removed Multiple generations can create severe foliage disfi gurement Pupation occurs inside the larval tunnel usually near the leaf base The stocky small 3 mm black adult fl ies often rest on daylily blooms Although this insect doesnt appear to kill plants the leaf damage is of concern for display gardens Also as young pale larvae can be virtually invisible in tissue near the plant base they may escape detection in nurseries when fans are being prepped for sale At this time implications for international trade are unknown as this is a newly emerging pest for U S growers No chemical controls have been formally tested on this insect Contact sprays cant reach the protected larvae instead they may kill predators of adults as well as the parasites targeting fl y larvae and pupae Removing and destroying infested leaves may reduce populations However daylily leafminer occurs Photo courtesy of Sharon Galloway Damage caused by the daylily leafminer Ophiomyia kwansonis Sasakawa is evident on foliage Larvae feed only on leaves mining between leaf surfaces and leaving obvious silver tunnels not appear to be harmful Photo by V J Hickey courtesy of P Hickey A leafminer fl y rests on a daylily bloom Although the larvae can cause considerable damage to Hemerocallis foliage the fl ies do The small up to 5 mm yellow maggot larvae feed only in leaves of Hemerocallis species and their cultivars mining up and down as they feed between the leaf surfaces Yellow larva of the daylily leafminer in naturalized daylily stands allowing reinfestation If you see damage in unlisted states or can recommend effective controls please contact G L Williams at williagl@ mda state md us For further information visit www npdn org webfm_ send 1704 and www daylilies org ahs_ dictionary leafminer html Gaye Williams is an entomologist with Photo courtesy of Gaye Williams the Maryland Department of Agriculture Plant Protection and Weed Management IPM Plant Pest Laboratories She can be reached at WilliaGL@ mda state md us 20 JANUARY 2012 American Nurseryman www amerinursery com