The Hemerocallis Gall Midge by Matthias Thomsen-Stork, June 1998
The swollen buds and tiny white worms inside the buds are Hemerocallis Gall
Midge (Contarinia quinquenotata) - a very
dangerous pest if you don't fight them.
We have known Hemerocallis Gall Midge here in Europe for decades and I have
seen what it looks like if you don't recognize them and if you don't fight them.
The flies lay their eggs primarily into the buds of early blooming daylilies
and each bud can contain around 300 larvae. The result is that the buds swell
abnormally and are eventually aborted without having been able to open.
The larvae then leave the bud and develop into flies. These overwinter and the new
cycle begins the next spring.
You can easily imagine what happens if you allow the larvae to develop:
10 infested buds "generate" around 3000 flies and next season the female
part of them will want to lay eggs. This really is very dangerous and I still
recall the terrible sight of a very large collection in Frankfurt/Germany where
the staff had not recognized the symptoms: only swollen buds on hundreds of
daylilies and no flowers.
Luckily prevention is very easy: I walk around in spring and early summer (anyway)
and whenever I see an abnormally swollen bud I just break it off and destroy it in
a way that the larvae can't survive: in a sealed plastic bag and off into the
garbage - do NOT compost them.
The Gall Midge seems to prefer special plants - its always the same plants that
are affected: the eary yellows. When we still grew ORANGE PRELUDE this one had
about 75 % of the attention of these "nice" little fellas.
Now I have an even earlier tet seedling from STELLA DE ORO and I use this as a
trap plant. The flies behave very well and put their eggs exactly where I want
them to: mostly into this early seedling.
This way we have been able to keep this disease at bay - 15 infested buds this
spring out of a total of about 30 000 buds on 300 large clumps - that is no problem.
