Ministry of Agriculture

Hemerocallis (Daylily) Gall Midge
(Contarinia quinquenotata)

Biology and Symptoms:

The adult is a small, seldom seen fly that lays its eggs in daylily blooms in spring. The maggots feed on unopened flower buds and cause them to become distorted and unable to open. Infested buds will contain numerous white maggots that are around 3 mm in length (Plate 2). The larvae will grow within the bud, then drop to the ground and pupate for the winter. There is one generation per year. Early flowering varieties are at most risk of infestation. Some varieties are more attractive to the gall midge than others. This pest has the potential to become a serious problem for daylily producers and is commonly found in landscape plantings of daylilies.

infested buds Plate 1. Hemerocallis Gall Midge.
Normal bud above; two infested and swollen buds below.
Photo courtesy Jay Rowland c/o Pam Erikson.
infested bud with maggot Plate 2. Hemerocallis Gall Midge.
Infested bud with maggot indicated by arrow (maggot magnified in top right inset).
Photo courtesy Jay Rowland c/o Pam Erikson.

Known Distribution:

In British Columbia: Lower Mainland, Bowen Island, Vancouver Island. The gall midge occurs commonly in Europe.

Management:

  • Starting when the first buds occur, monitor for distorted buds.  Remove and destroy distorted buds (Plate 1) by freezing for 48 hours or burning.  Do not compost.
  • There are no registered chemical control products.  Research indicates that systemic insecticides are effective.
  • The planting of an early yellow daylily trap crop has been found to reduce the population in Southern England, and can be used to protect other varieties.

Further Information:

Updated September, 2009