Why are there worms in my swimming pool?
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EmailEditor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
Often
during the late spring and summer, we receive samples of worms people
have collected from their swimming pools. These worms measure up to 14
inches in length and are usually tan to dark brown in color. Their
occurrence obviously concerns people. However, if you experience this
phenomenon don’t fret, almost always, these are horsehair or Gordian
worms. They are parasites of some insects, but do not harm mammals.
Horsehair worms develop as parasites in the bodies of grasshoppers,
crickets, cockroaches and some beetles. When mature, they leave their
hosts to mate and lay eggs. This occurs in water, so they are often
found in puddles, ponds, livestock watering troughs, swimming pools or
any container with water. In water, these worms wiggle slowly, often
contorting their bodies into intricate knots. They are called horsehair
worms because they resemble the hairs of horses’ manes or tails and are
often found in areas where horses drink. It was believed as these hairs
fell into water, they came to life.
Adult worms mate in water and females lay long gelatinous strings of
millions of eggs. The eggs hatch usually within a few weeks and the
young nematodes crawl onto vegetation near the water’s edge to be
consumed by crickets or grasshoppers. It is believed as the nematodes
mature inside their hosts’ bodies and get ready to emerge, the insects
become very thirsty, thus seeking out water. If they jump into your
swimming pool, the result is one to several horsehair worm adults
swimming around the pool.
Since horsehair worms are harmless, except to insects, no control is
necessary. For identification, worms can be collected and placed in
sealed containers with water or preferably alcohol and delivered or
mailed to MSU Diagnostic Services. There is a $10.00 fee for their identification.
