From the Penn State Extension Article (August, 2018) by Nancy Knauss
Asian
jumping worms are a relatively new invasive species but they are rapidly
spreading across the United States. They can be found in the Southeast, along
the Eastern Seaboard, and in mid-Atlantic, Midwest, and some Northwestern
states.
There
are still native species of earthworms in a few areas of North America, but in
states where glaciation occurred the native species were wiped out. Forests
developed without them, but in time European earthworms appeared and began to
burrow through the soil. As the tunnels were created, the earthworms mixed soil
components and improved air and water movement. Unfortunately, European
nightcrawlers are now being displaced by the destructive Asian jumping worms.
These invasive worms are
members of the genus Amynthas and live in the organic matter
or the topmost layer of soil. This upper layer of organic matter protects the
soil from erosion. It is in this duff layer of the forest floor where many of
the tree roots establish and wildflowers grow. Asian jumping worms are ravenous
feeders and they quickly consume the organic matter and degrade the soil.
Nutrients from their castings are rapidly released with a small amount actually
reaching the roots of plants. During heavy rainstorms, the nutrients are
quickly lost and the soil may be unable to support plant growth. Where there
was once lush vegetation and wildflowers, there is only bare soil. When such a
disturbance happens, it provides an opportunity for an invasive plant species
such as garlic mustard or stilt grass to move in. The structure of the soil is
also damaged and often there will be voids under tree roots that are near the
surface of the soil.
Asian jumping worms are an annual species—the adults die after the first freeze. The cocoons, which are about the size of a mustard seed, will survive the winter and hatch in mid-April after temperatures reach 50°F for a consistent period. One worm can produce many cocoons without mating. While the cocoons can survive the winter temperatures, the hatchlings cannot survive freezing temperatures.
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| Worm hatchlings (PSE MG Program) |
How
do you know if you have Asian earthworms?
One
telltale sign of an infestation is a very uniform, granular soil created from
worm castings, the nutrient-rich soil that the worms leave behind. The texture
of this soil is often compared to coffee grounds.
When
you scratch the top layer of soil, you will see the worms thrashing about with
an erratic, snakelike movement. These worms, which can reach 6 inches in
length, are much more active than European nightcrawlers.
If
you examine a worm close-up, you will notice the prominent band around the body
of the worm called the clitellum, where cocoons are produced. On a jumping
worm, the band completely encircles the body, is milky white to light gray, and
is flush with the body. On European nightcrawlers, the clitellum is raised and
reddish-brown color and does not wrap entirely around the body
What
can you do to prevent jumping worms from invading our forest and landscapes?
It
is very difficult to remove an invasive species once it is well established in
an ecosystem, so the focus must be on preventing the spread of Asian
earthworms. The cocoons, which are very small and difficult to see, can be
easily introduced to your garden in compost, bark, or leaf mulch, or when
swapping plants with friends.
Consider
reducing the amount of organic matter that you add to your garden each year.
Most importantly, when purchasing bulk mulch or compost, use a reputable
producer that has heat-treated the material to a temperature of 130°F for at
least three days to destroy the cocoons. The other option is to purchase bagged
mulch.
Check
any plants that you bring into your garden for the distinctive coffee ground
like soil. If present, throw out the plant, or remove all soil and rinse the
roots thoroughly before bringing the plant into your garden.
 |
| Coffee ground-like soil (PSE MG Program |
What to do to control jumping worms?
Research
is currently being conducted on invasive worms at the University of Wisconsin
and several practices do show some promise of control. Once you have identified
jumping worms in your landscape, you will need to eliminate both the cocoons
and the worms.
If
you have a small population of jumping worms, handpick and destroy adult worms
by bagging them and throwing them in the trash. Brad Herrick, an ecologist, and
researcher at the University of Wisconsin Arboretum recommends making a mustard
solution of one-third cup dry mustard in one gallon of water and drenching the
area. The solution will irritate the worms and bring them to the soil surface
where you can easily remove them.
While
research is ongoing, abrasive materials such as biochar (ground up charcoal)
and diatomaceous earth (fossilized diatoms) may show some promise in killing
adult jumping worms. Incorporate one of these products into the infested soil
to a depth where the worms are located. Worms that come in contact with the
materials and will be adversely affected.
In
addition, an organic fertilizer used by golf course managers has been effective
in eliminating jumping worms. The fertilizer made from tea seed meal irritates
and eventually kills these worms when applied to the soil. Two applications are
recommended, one in late April or early May to target the young hatchlings and
again in the summer to suppress the remaining worms.
It
is important to also destroy Asian jumping worm cocoons. The cocoons are
sensitive to heat and can be destroyed with clear plastic solarization. In late
spring or summer, cover moistened soil with a sheet of transparent polyethylene
for two to three weeks or until the soil temperature exceeds 104°F for at least
three days.
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