My Amaryllis bulbs are infected with syrphid flies. I have dug
them but don't know what to do with the bulbs. What can I do to save them?
Until receiving your question, I had always known of syrphid flies as
beneficial insects in the garden, so I considered the possibility that
the bulbs might be infested with bulb mites, or mealybugs, which are
fairly common pests of Amaryllis. That being said, in my research to
answer your question, I came across an article by Whatcom County
Washington State University Extension agent Todd Murray which describes
the Narcissus bulb fly, which is indeed a syrphid fly, and does
sometimes infest Amaryllis bulbs. Excerpt:
Monitoring and Management: There are no pesticide recommendations
available for these bulb flies. But that's O.K.; we have many
alternatives that we can use to avoid mushy bulbs. You should be thinking
about trying these practices if you have a problem with bulb flies.
In May, on sunny days look for large bumblebee-like flies hovering
around your flowers. Bumblebees will have two pairs of wings while
bulb flies will have one. Grab your handy insect net (you all have
one, right???) and catch the critters before they can do too much egg
laying. This sounds tedious, but is very effective for protecting
small plantings of susceptible bulbs. Remember, each female fly can
lay up to 100 eggs! Plus, if it is a nice sunny day, you should be
outside admiring and tending your garden anyway.
-
Adult flies use visual cues and smell to locate your delicious bulbs.
After you have enjoyed your flowers, cover the bulb bed with a
floating row cover, like Reemay*. Another recommendation given
suggests that you mow down the vegetative portions of your plant and
gently cover the tops with soil. Female flies will be unable to
locate the bulb. Once no new foliage is sprouting, remove and store
the bulb through the off-season. If you do this, I do not know the
impacts this will have on next year's flower. That vegetation
produces the bulb's energy reserve that is needed for next year's
growth. Regardless, the earlier you can pull your bulbs out, the
better chance that you will avoid bulb flies.
- Bulb flies are less active in open, windy areas. Plant your beds in
exposed windy places, if your landscape provides this type of
climate.
- Avoid any damage to the bulbs when handling and planting. The lesser
bulb fly prefers damaged goods to healthy bulbs. Establishment of
maggots is much easier if there are already rot producing organisms
in the bulb.
- Plant your bulbs deep, if they can tolerate it. Bulbs planted 25cm
(or about 10") deep in the soil will evade attack by adult flies. I
am unaware if planting this deep is practical.
- When the time comes to pull up the bulbs, check the basal plate of
each bulb. When you purchase new bulbs, check the plate for any signs
of squishiness and rot. If you find some rot there, do not plant them
and discard the rotten bulbs.
- Infested or suspicious bulbs can be cleaned of maggots by soaking
bulbs in hot water (43-44 C) for at least 40 minutes. Care must be
taken to not exceed this temperature, because you will damage the
bulb. This is a great way to kill other pests of bulbs, too.
- Finally, if the problem persists, the sure-fire way to avoid bulb
flies is to buy your flowers at the store like all the non-gardeners
and black-thumbers out there. If you don't plant it, they won't
come. This option is the one that I'm going to take now.
In the event that there are other pests present on your bulbs, this information from University of Florida Extension may be of interest. Excerpt:
"Spider mites are tiny animals (1/50 inch or 0.5 mm long) that cause
injury similar to that of sucking insects as they feed on the leaves of
amaryllis during warm, dry periods. Bulb mites attack rotting bulbs and
tunnel into healthy bulbs, transmitting organisms that produce bulb rot.
Bulb mites are particularly damaging to bulbs of amaryllis.
Mealybugs are soft-bodied insects covered with a white, waxy material.
When mature, they vary from 1/50 to 1/3 inch (0.5 to 8.5 mm) in length.
They damage plant foliage by sucking plant fluids and may invade stored
bulbs. Some control can be obtained by frequent syringing with a hose."
In case you are curious, here is information on the beneficial properties of syrphid flies, from University of California, Davis Integrated Pest Management.
Season
All Season
Date 2007-07-06
Link to this record only (permalink)
Amaryllis bulbs are too beautiful (and expensive) to simply throw away after blooming. Starr Ockenga's book, Amaryllis (Clarkson Potter/Publishers, 2002) describes how to care for the bulbs so they will produce new flowers year after year. In a nutshell,
