WSU Extension

Hortsense

Daylily
 
Insect
Daylily gall midge 
Thrips 



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Caption: Daylily gall midge larvae & damage to bud
Photo by: D. Pehling
  
Daylily : Daylily gall midge
(revision date: 3/10/2017)


Biology
The daylily or Hemerocallis gall midge (Contarinia quinquenotata) is the larva of a small, nondescript, grayish-brown fly. The adult fly overwinters in the soil and emerges in spring to lay eggs on developing flower buds, making early-blooming varieties most susceptible to damage. There is only one generation per year, so later-blooming varieties are less likely to be infested. The eggs hatch in mid-spring to early summer. Up to 300 larvae may feed inside a single flower bud. The legless and wingless larvae are white to cream-colored, and about 1/8 inch long. Damaged buds appear unusually short, swollen, and distorted. They may also be discolored or pale. Buds may either open abnormally or fail to open and drop from the plant. The larvae may be confused with thrips.
Management Options


Non-Chemical Management
  • Avoid early-blooming daylily varieties, particularly early-flowering yellow types.
  • Plant late-blooming daylilies, which are less susceptible to damage.
  • Monitor plants for distorted, dimpled buds with thickened petals and watery fluid within the buds.
  • Remove infested buds. Destroy infested buds or dispose of them in a sealed container. Do not compost infested plant material.
Select non-chemical management options as your first choice!

Chemical Management

If gall midge is a problem in your area, apply as flower buds of early varieties develop in order to kill egg-laying female flies. Avoid spraying blooming plants as most of these products are toxic to bees. Contact (non-systemic) insecticides may have limited efficacy as adults may fly and lay eggs over a period of several weeks.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • Bayer Advanced Power Force Multi-Insect Killer R-T-S
    Active ingredient: cyfluthrin  |  EPA reg no: 72155-39
  • Bonide Systemic Insect Control
    Active ingredient: acephate  |  EPA reg no: 239-2461-4
  • Bull's-Eye Bioinsecticide
    Active ingredient: spinosad (spinosyn A+D)  |  EPA reg no: 62719-314-56872
  • Monterey Garden Insect Spray [Organic]
    Active ingredient: spinosad (spinosyn A+D)  |  EPA reg no: 62719-314-54705
  • This list may not include all products registered for this use.
Images

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Caption: Daylily gall midge larvae & damage to bud
Photo by: D. Pehling