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I am
writing this article in hopes of creating awareness to a new problem - Hemerocallis Gall
Midge. Without awareness, we cannot control it - so education is of the utmost importance. I'm
not a scientist - but I am a dedicated gardener who has grown and bred daylilies for many years.
I just want to get as many questions answered as I possibly can, and put things into simple terms
that everyone can understand.
For many years, we have lived with the blessing that daylilies have been relatively pest and disease
free. Unfortunately, we now have two prevalent problems to deal with. One is rust - and while I
consider it to be a serious disease, it is not yet affecting the Pacific Northwest and seems confined
to the southern and eastern United States at this time. The other problem however, gall midge, IS
here and is something we must deal with NOW.
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Hemerocallis Gall Midge has been a pest in Europe since 1989. They are successfully controlling
this problem by diligence and dedication in inspecting the plants in spring and removing
potentially affected buds. There are many unanswered questions, but this is the information that
we have at this time:
There appears to be one lifecycle per year (this is indeed a blessing).
The adult gall midge is a tiny fly - she lays her eggs inside the buds of daylilies (early yellow
varieties seem to be particularly susceptible - which would leave two options open ... either don't
grow the early yellows, or, as they have done in Europe, grow a specific area of JUST early
yellows as a `trap').
The eggs hatch in the spring and early summer months - the feeding of the larvae on the bud
causes distorted buds that draw attention to their presence.
Affected buds are very easy to identify - the buds swell up abnormally, some quite round, some
wider at the base. Some buds also appear to have a more blotchy appearance on the outside.
Upon inspection of the bud - if you are infected, you will find many tiny white maggots inside
the bud. This is the larvae stage of the gall midge. It is possible to have up to 300 larvae in one
bud. (In cases that I have seen so far, I have observed between 5 and 50 larvae.)
The infected flower buds do not open - the flower is destroyed and eventually drops off the
scape.
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What happens after the maggot matures is still under observation. It is the general opinion that
the larvae fall to the ground, pupate and overwinter.
When the ground warms up and spring is
here, the midge emerges from the ground, mates, and lays her eggs in the new buds. Thus the
cycle starts again.
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Control of this problem, so far, does not require spraying. Regular walks around the garden,
inspecting the daylilies for abnormalities, is what everyone needs to do. I have destroyed
hundreds of buds this year - NOT from finding gall midge, but just from breaking off buds that I
THOUGHT might be infected. I grew up with the philosophy `better safe than sorry!' I have
seen several cases in other gardens - some of the buds were very easy to spot - very swollen buds
that looked like golf balls, others were quite triangular - being wider at the base; others were just
slightly swollen but a little off-color. The key is - LOOK carefully at the buds - if you think that is
looks abnormal, take it off! It's only one bud - it's definitely worth taking the chance, because
you certainly don't want to leave a bud on that might have 300 larvae inside!
If you DO find the larvae, disposal is equally as important as finding it. The bud must be removed
and either burned (my personal favorite), sealed in plastic and put into the trash, or dropped into a
sealed jar of rubbing alcohol. Do not, under any circumstances, put these buds into your
compost! The only way of controlling this pest is by breaking the life cycle - if all the affected
buds are destroyed, then there will be no adults to lay the next generation.
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As I noted before, this problem has been prevalent in Europe for many years. Being a relatively
small world, it was only a matter of time before it reached us. Now it IS here and it must be dealt
with. As I gather more data, I will update as much as I can. If there are any questions or if you
find this problem in your garden, please email me at pamela1@istar.ca or call (604) 856-5758.
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July 2008 Update!
This
is a general handout that we like people to have for reference should
they find the gall midge problem in their gardens. Awareness is
the key to control of any pest problem, so we are passionate about
getting the information to as many people as possible! I am not a
scientist, but a dedicated gardener who has grown and bred daylilies
for most of my life. We have done years of testing since this
pest was first identified and it is my goal to answer as many questions
as I can and to put things in simple terms that everyone, not just
gardeners, can understand.
For many years, we have
lived with the blessing that daylilies have been relatively pest and
disease free. Unfortunately, we now have two prevalent problems
to deal with. One is rust – and while I consider this to be a
very serious disease, it is not affecting the Pacific Northwest and
seems basically confined to the southern and eastern United States at
this time. The other problem however, gall midge, IS here and is
something we must all deal with immediately.
Hemerocallis Gall Midge
has been a pest in Europe for many years, although studies and reports
have been available only since 1989. They are controlling the
problem by diligence and dedication in inspecting the plants in spring
and removing potentially affected buds. At this point in time,
they have no recommended spraying methods to control the midge.
The life cycle is as
follows – the midge is a very minute pink-tinged fly, not visible to
the naked eye, but can be seen under a microscope. She
emerges from the ground when the weather warms up in May and lays her
eggs on the largest daylily buds that she can find. The beauty of
the daylily is that with the buds maturing at such a different rate,
she is only able to access the largest one or two buds on a scape, in
most instances. (There ARE cases where a plant has been decimated
– we refer to those as ‘trap’ plants, but more about that later.)
Once she has laid her eggs, she dies within about 72 hours, but during
that time she can lay up to 300 eggs! The eggs hatch in just a
few days and, as a small white worm, begin to feed on the inside of the
bud. Once feeding begins, the damage to the bud is irreversible –
even if they leave the bud after one day, the bud will mature to
produce blotched blooms. (This is one of the reasons why,
although many people want to apply a systemic insecticide, control by
spraying would be difficult since the larvae would only die if they
ingested the systemic, but in order to ingest it they have to be eating
– hence damage will be done anyway.) Once the larvae have been
feeding for a few days, the buds begin to swell and have a somewhat
paler appearance. Heavy feeding results in extremely round, pale
buds that are easily identifiable from a distance. Buds that have
only a few larvae will swell only proportionately and may be missed
without careful inspection. Our rule of thumb in the garden is
‘if you THINK it might be affected, pick it!’ – always better to be
safe than sorry! Some affected buds can be much larger at the
base and showing a slight tulip-style opening at the end. If you
find buds that are rotten and decomposing, that means that the larvae
have finished feeding and have returned to the ground to begin their
pupation stage. They then live in the ground until the following
spring, when they emerge as the adult midge and start the cycle all
over again. We are extremely fortunate that the Hemerocallis Gall
Midge has only one generation per year – by disposing of the affected
buds in the early stages of bloom, the mid and late season bloomers all
bloom as normal. There have also been suggestions to apply a
ground-drench insecticide in the fall to kill the larvae. While
we prefer not to damage our eco-system with pesticides (we happen to
appreciate the earthworms and all other beneficial insects we have in
our garden), we will continue to pursue investigation of biological
agents that may help the problem. (Currently we are researching
granular Neem-oil products). All that being said, should a safe
product be found to spray on the ground, there is still no guarantee
that the midge could not fly in from a neighboring garden and begin the
cycle again. The midge has proven to have a flying capacity of
3-5 kms per year, so she is quite able to travel!
Earlier I had mentioned
trap plants. We learned this technique from the growers in Europe
and it is working very well for us. Basically, it means setting
out plants for the midge that they seem to enjoy the most, allowing
them to infest the plant thus leaving the surrounding plants
undamaged. To date, we have found that H. ‘Wynnson’, H. ‘Fairy
Firecracker’ and H. ‘Leprechaun’s Wealth’ are among their
favorites. We watch for the developing distorted buds to ensure
that the eggs have hatched and are feeding, then remove the affected
buds and burn them. Early-blooming yellows have long been a
favorite of the midge, of which H. ‘Wynnson’ is one – I fear I will
never see any of those lovely blooms again as she was completely
infested this year – but as I said, the surrounding plants were
untouched. In order to minimize future infestation, we have even
switched our breeding program to mid and late season varieties!
Disposal of the buds
has also warranted great discussion and testing. We were
initially advising sealing in plastic and placing in the garbage, or
burning. Since then, we have tested many sealed bags of infested
buds – and after three months, the buds are completely decomposed and
turned to liquid, but lo and behold, the white larvae are still alive
and well and swimming in the water. To ensure complete
eradication of the larvae we find, we now completely burn the buds –
either in a small metal container in a safe place, or in the
fireplace. Another discussion that has recently come to light is
freezing them. Place your sealed plastic bag of collected buds in
a freezer at a temperature of -20C for a minimum of 48 hours. We
have not yet tested this method, but will do so next year.
Since the initial
discovery of the midge in western Canada in 1998, we have seen the
populations diminish each year – with the exception of this year,
2008. This past spring was especially long and cold and the midge
did not emerge from the ground until a month later than usual.
(We use sticky traps around the garden to ascertain when she is flying
and for how long). Since she was later, there were more daylily
scapes accessible to her. This has resulted in more widespread
damage being noticed, which, in my humble opinion, is a very good thing
– it has alerted more people to the problem, and awareness is the key
to control! I have answered more telephone calls and emails
about gall midge this season than any other year in the
past! In every garden presentation I give, we have now
included slides or power point pictures of the gall midge damage to
make it easier for people to identify them, although I am convinced
that any daylily grower will notice this abnormality very
quickly! I have also made the suggestions to garden clubs
and societies to check, if they have the opportunity, the local
plantings in parks, commercial complexes, community centers, etc – it
is highly unlikely that any of the municipal workers will notice the
problem, and every eye watching helps!
Spring has brought
frustration with reappearance of the midge each year, but take heart –
July comes quickly and with a little time spent in catching the
offending buds, damage is over with before bloom starts! Being
armed with the knowledge of what to look for is crucial to the on-going
enjoyment of our favorite plant! We will be updating our website
with new pictures of the gall midge this fall.
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