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(Contarinia quinquenotata)
For many years daylilies have been considered
the perfect garden perennial - long flowering and pest free.
Unfortunately the pest free attribute no longer applies.
HEMEROCALLIS GALL MIDGE - has been a daylily pest
in Europe for some time and in 2001 was identified in British
Columbia. It is officially recognized as occurring in the
Lower Mainland and Bowen Island. Unfortunately, it has been
present on Mayne Island for the past three years.
Damage occurs in June. Maggots develop inside daylily flower
buds causing them to become distorted and unable to open properly.
Life Cycle
Infested buds contain hundreds of small (3mm) semi-transparent
white maggots. The maggots develop within the buds and feed
on the unopened buds causing them to become distorted, abnormally
squat and swollen. Galled buds fail to open and either dry
up or rot. They usually turn whitish in colour with a purplish
base. The petals within the buds become swollen and crinkled,
and larvae are found at the base of the petals in a watery
liquid. When finished feeding, the larvae drop to the soil
where they form cocoons and over winter.
The adults emerge from May to June. The females are 2mm long
grayish-brown, seldom seen flies. They fly to daylily buds,
lay their eggs and the galled buds begin to appear in late
May or early June. In severe attacks a large proportion of
the buds developing during June fail to open. As there is
only one generation a year and flower buds that develop after
the first week of July may escape damage.
CONTROL MEASURES
Treatment involves removing affected buds as soon as it is
obvious that they have been attacked. These buds must then
be destroyed so that the maggots cannot continue their life
cycle. Burn them. Do not put them in the compost or throw
them into garbage pails. Seal them in plastic bags until you
are able to burn.
This procedure will reduce damage in the following year but
the effectiveness of this depends on how thorough the galled
bud-picking is and whether nearby gardens have infested plants.
The early yellow daylilies can be planted to use as traps
and the flower buds removed and destroyed. Since the larval
stage is enclosed within the buds it is difficult to reach
with a pesticide. The adult stage is more vulnerable but is
active over a period of about six weeks during which egg laying
can take place. No pesticides have been recommended or listed
for this pest.
Please check any daylily plants in your garden and remove
any galls found.
For photographs of the midge and infected buds, check the
web site:
http://www.agf.gov.bc.ca/cropprot/daylilymidge.htm
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