Daylily Midge

Order: Diptera
Family: Cecidomyiidae
Species: Contarinia quinquenotata

Fig. 2. Infested bud with maggot indicated
by arrow. (photo from http://www.agf.gov.bc.ca/cropprot
/daylilymidge.htm)

The daylily midge, also known as the Hemerocallis gall midge, is a common, yet little understood pest of daylilies grown in central Europe. In 1989, the daylily midge had spread to Britain where it continues to spread. In 2001, gardeners and commercial daylily producers in Vancouver, British Columbia were disappointed with their daylily blooms. Upon further investigation, little tiny white maggots were found in the distorted flower buds. This pest of daylilies is NOT known to occur in Whatcom County or Washington State, yet.

Description: The daylily midge adult is a small, nondescript typical gnat. I’m not sure if I could tell this midge from others in our area. Adults emerge from the soil in spring and begin mating and flying. Female flies seek out the developing flower buds of daylilies to lay eggs. In Europe, daylily flower buds are susceptible from mid-May to early July. Eggs hatch in mid-spring to early summer. Larvae feed on the developing flower parts inside the bud causing deformation of the bud. Larvae are cream colored maggots about 3mm long when mature. The unopened flower bud eventually detaches from the stem and drops to the ground. Larvae enter the soil to pupate and wait out winter until next spring.

Damage & Monitoring: Early flowering yellow daylilies are most susceptible while late flowering daylilies can avoid infestations. Look for deformed buds with discoloration in spring. Examine buds for small maggots. An infected bud can contain anywhere from 1 to 300 maggots; however, one daylily grower in BC, Pam Erikson, mostly finds 5-50 larvae per bud. Pam Erikson also describes that swollen buds can be quite obvious, shaped like golf balls or in triangles.

Management: Europeans have avoided early flowering daylilies and regularly removed deformed buds to keep this pest at bay. This tactic also appears to be working for British Columbians. Through diligent removal of suspect buds and planting resistant varieties (later varieties), daylily midge populations can be lessened in gardens.

To date, the Daylily midge has not been identified in Whatcom County or Washington State. However, the pest is widely distributed throughout the Lower Mainland of British Columbia. If you find suspicious daylily buds that you believe may be infested with larvae this spring, please collect them and submit them to the Master Gardener clinic. You could be the first unlucky gardener on your block to have daylily midges!

To learn more about the Daylily Midge visit these websites:

Information from the Royal Horticultural Society of England
http://www.ncf.ca/~ah748/rhs.htm