Hemerocallis gall midge

The daylily gall midge or Hemerocallis gall midge (Contarinia quinquenotata) is a damaging pest of daylilies. The midge is thought to have originated from Asia, the native home of Hemerocallis spp. It was first noted in Europe, where it is now widespread, in the 1880's and found in England in 1989. Detected in Vancouver, British Colombia in 2001, it was found in 2007 in Washington. The range of the midge is expanding in the state of Washington. There are reports of it in Whatcom, Skagit Valley, Bellevue, Everett, Granite Falls and in the Puget Sound area. Oregon growers need to be alert about this pest and make sure they inspect any plant material from infested areas for signs of these insects.

Biology
The adult midges emerge from the soil, from whence they overwinter, and lay eggs on developing buds of daylilies, Hermocallis sp., usually from May through June. The larvae that hatch from these eggs are small and legless maggots. The white midge maggots can be numerous and are usually found feeding within the buds but are sometimes seen on the outside of the buds. There is one generation per year.

Damage
Feeding by the maggots on the developing lily buds causes the buds to become distorted. Buds appear swollen and discolored. Many buds are shriveled and may not completely form. Blossoms from affected buds are also deformed and often have crinkled petal edges.

Management
Cultural management is focused on avoidance of early-blooming, particularly yellow, varieties (although in 2017, reports were of damage on the late-blooming varieties rather than early varieties, possibly due to the long cool wet spring). Infested buds should be removed and properly disposed (burned or bagged and removed). Do not put removed buds in the compost. As the midge overwinters in the soil, bare root or soilless plant starts may reduce the risk of introduction of the pest.

Chemical management has been timed to protect new buds. The midges can lay eggs for several weeks so many growers opt for systemic over contact applications. Halstead (see Resources) has information on chemical trials for this midge.

Resources:

Hemerocallis Daylily Midge. American Hemerocallis Society. This site also includes a list of late-blooming varieties courtesy of the RHS. <13 July 2017>

Daylily gall midge. Hortsense - WSU Extension. <13 July 2017>

Halstead, A. Hemerocallis gall midge study. <13 July 2017>

Hemerocallis gall midge. Royal Horticulture Society. <13 July 2017>

Original publication: 7/12/17
Last update: 7/14/17

Author: R.L. Rosetta, Extension Nursery Integrated Pest Management, Department of Horticulture, Oregon State University

Gallery

Hemerocallis gall midge blossom damage

Blossom damage from Hemerocallis gall midge

Blossom damage from Hemerocallis gall midge

Blossom damage from Hemerocallis gall midge

Daylily bud damage from Hemerocallis gall midge larvae

Bud damage from Hemerocallis gall midge

Hemerocallis gall midge larvae crawling on lily bud

An assortment of Hemerocallis gall midge-damaged lily buds (healthy bud at top of image)

Hemerocallis gall midge larvae feeding within daylily bud

Hemerocallis gall midge larvae feeding within bud

Hemerocallis gall midge larva close-up

Page last modified 7/14/17