Download Crazy Snake Worms - Connecticut Gardener

Crazy Snake Worms
By Dawn Pettinelli
“It may be doubtful whether there are
many other animals which have played
so important a part in the history of the
world, as have these lowly organized
creatures.”
– Charles Darwin
A
BOUT 6 or 7 years ago, when
I finally got around to edging,
weeding and mulching the
picket fence dahlia beds in mid-August,
I encountered a most peculiar phenomena. As the soil-grass continuum was
sliced by my spade to create a deep ‘V’
between the beds and the lawn, out
sprang (quite literally) large, writhing,
snake-like creatures. In fact, at first,
I thought they were baby snakes but
upon closer examination, they turned
out to be earthworms.
Now I have been gardening for more
than half a century and never have
encountered such distinctive, quick-
moving worms and was not sure what
to make of them, except to think that
this is not normal.
A couple of years later, at an international conference of soil scientists,
I was perusing the poster sessions and
stopped at one by Josef Görres, a professor from the University of Vermont,
on the effects of invasive earthworms on
forested areas in Vermont. There, before
See color photo on page 27
my eyes, were pictures and descriptions
of the culprits and of evidence of the
damage they wreak when allowed to
enter native New England woodland
areas, as well as the kind of trouble
they were causing in my gardens.
As a longtime gardener, I was always
happy to find earthworms in my beds
and lawns. After all, aren’t earthworms
the gardener’s friend? Don’t they till the
soil as they tunnel through it consum-
ing bits of organic matter and mineral
soil? Their holes allow air and water to
penetrate deeper into the soil to benefit
plant roots. Their casts (droppings) are
rich in nutrients and microbes that encourage plant growth. They incorporate
and mix organic matter into the soil,
which aids in the formation of good
soil structure as well as increased water
holding capacity. What’s not to like?
Just as in real estate, the answer to
that question is dependent on location,
location, location. A lot of us don’t remember what we had for dinner yesterday so, based on that rationale, even
more of us probably forgot that our
state was covered by a glacier until
about 15,000 years ago. (See box below
on Glaciation in Connecticut.) Any
native earthworms were either forced
south or obliterated by the glacier.
So where did the worms we now find
in our gardens come from? Most likely
not from more southern locations, as
GLACIATION IN CONNECTICUT
Compiled by Will Rowlands
G
laciers have ravaGed the topography of New england
and connecticut for millions of years. The last major
glaciation advanced as far as southern long island
some 21,000 or 22,000 years ago. at that time the laurentide
ice sheet covered eastern canada and New england.
connecticut has experienced a number of ice ages. some
suggest there may have been as many as 10-20 glacial periods
in North america over the last 1 or 2 million years.
check it out yourself. Find an outcrop of bedrock and look
for glacial striations. Glaciers carry massive rocks and boulders
that gouge grooves in the bedrock as they advance. The signs
are unmistakable and give the glacier’s direction of movement,
generally north to south.
dating of recent glacial events is possible through carbon
dating of organic components in glacial deposits. They can also
be dated by varves, which are layers of sediment deposited
seasonally in glacial lakes that can be counted like the growth
rings of a tree. relative temperatures, up to almost a million
years ago, can be estimated by analysis of oxygen isotope data
obtained from deep sea core samples.
long island is actually a moraine composed of glacial till,
the material picked up by the glacier as it advances. When a
glacier recedes, it melts and drops whatever material it was
carrying in a terminal (or end) moraine.
There was so much material left behind when the last
glacier melted and retreated that it created a dam and a freshwater lake from the meltwater (lake connecticut) in the area
that is now long island sound. The captain islands, Block
island, Falkner island, Martha’s vineyard, long island, Nantucket
and the Norwalk islands are all glacial deposits.
September/October 2014
sea level was lower at that time, as much of the earth’s water
was tied up in continental glaciers. When the glaciers melted,
sea level rose, eventually flooding lake connecticut and
creating long island sound.
Glacial periods tend to repeat in 100,000-year cycles. More
recently, we’ve seen some 40,000-year cycles. The alternating
glacial and interglacial periods are believed to be driven by
overlapping cycles in precession (direction of the earth’s axis),
obliquity (tilt of the earth’s axis), and eccentricity (shape of the
earth’s orbit).
as you might suspect, how the earth absorbs, or reflects,
solar radiation from the sun is a major factor in determining
the frequency and length of ice ages.
historically, warm periods have been the exception and
cold ones the rule. right now, we’re 12,000 years into an interglacial warming period. The last interglacial lasted 20,000 years.
When you think about ice ages, consider how native
soil organisms and plants were displaced and/or killed off.
The laurentide ice sheet was probably around 2,000 feet thick
in connecticut and several thousand feet thick in northern
New england and eastern canada.
like huge bulldozers, glaciers scraped off 60 feet or more
of surface material and destroyed entire ecosystems in the
process. The average depth of the residual glacial till left
in New england is around 10 feet.
as connecticut has been subjected to advancing and receding glaciers a number of times, it should come as no surprise
that we don’t have any native earthworms. 짮
Will Rowlands has a BS in geology from Dalhousie University
in Halifax, Nova Scotia, and is a UConn-certified Advanced
Master Gardener.
24
Connecticut Gardener
Crazy Snake Worms
earthworms move about a half mile
every 100 years, so they would not have
reached our New England forests yet.
Earthworms and their cocoons came
along with the plants that our early
European ancestors brought over with
them or imported. A second mode of
intercontinental earthworm travel was
in ship’s ballasts, which were emptied
on shore for weight adjustments before
leaving port.
Two common Connecticut earthworms, also found in Europe, are
Lumbricus terrestris (nightcrawler) and
L. rubellum (redworm). There probably
are at least a dozen more earthworm
species of European origin in Connecticut, according to Dr. Görres, as he has
documented 14 of them in Vermont.
These early European immigrants
were right at home – and even productive workers – in cultivated gardens and
fields. As they consumed soil, soil microbes and organic matter, they made
nutrients more available to plants, as
well as improving the soil’s drainage and
other properties of interest to cultivated,
non-native plants.
Worms may influence the soil’s pH
as well, as some species of earthworms
contain calciferous glands and their
casts may contain considerable amounts
of calcium, a base cation.
The USDA estimates that an acre of
soil may contain 500,000 earthworms,
though other sources say closer to one
million, and that these creatures can
move up to 5 tons of soil per acre
every year through their bodies.
A Cornell University website states
that the earthworms in an acre of soil
can produce 700 pounds of casts a day.
That is an extraordinary amount of
activity taking place right beneath our
feet! And in some locations, most especially forested ones, this is a problem.
Soil and forest scientists have recogcontinued on next page
EXPERIMENTS IN GARDENING: Battling Invasive Earthworms
By Kathleen Nelson
i
first encountered Amynthas worms in the fall of 1992.
a friend and i were replanting a garden for a client. every
time we stuck a trowel in the ground, dozens of fast-wiggling
worms bubbled out of the ground. Other gardeners noticed
the same. We were all delighted – earthworms, we knew,
were good.
somewhat later, i heard rumors that earthworms weren’t
so good: they aren’t native and they’re damaging our forests.
at first it wasn’t easy to find information but, eventually, i found
people studying the problem. it wasn’t only forests – gardeners
were reporting problems, too. There didn’t seem to be a solution. i spent hours on Google looking for ideas. Gardeners
reported mixed success with diatomaceous earth. scientists
noted that earthworms do not thrive in acidic soil. My own
thought was – do NOT feed them tasty mulches year after year.
My gardens were suffering. My garden soil, lovingly prepared with lots of deeply dug organic matter and carefully
mulched with wood products each year, had become a sea of
worms. My perennials were not doing well. Only fast-growing
annual weeds thrived.
Amynthas worms are apparently “annual” worms, a new
population growing from overwintered eggs each season.
By late summer, with each step i’d sink inches-deep into the
soft soil. i could reach into the soil with my bare hands and
pull up a handful of a dozen or more giant squiggly worms.
i read of commercial growers who could no longer raise
hosta in their gardens. My most-affected garden was a shady
mulched bed with annual weeds and unhealthy perennials.
Being impatient, i threw everything at the problem garden.
in 2010, i weeded it, then sprinkled the 40 x 40 foot area with
diatomaceous earth and sulfur pellets. i mulched with buckwheat hulls, an expensive oatmeal-sized mulch that doesn’t
seem to rot. i looked at what was growing well in other areas
with worm problems and decided to propagate 15 flats of the
native running groundcover, Tiarella cordifolia, to plant the
next spring.
That garden is amazing now. Tiarella covers the ground
between larger, healthy, mostly-native perennials. i don’t need
Connecticut Gardener
mulch. i don’t sink in when i walk on the ground. i can’t reach
into the ground with my bare hands. recently, i needed worms
for an invasives exhibit and could only find a few. The soil ph
is now 5.2 or lower (5.2 is the limit of my ph test kit), down
significantly from 6.4-6.8 in my other garden beds.
did one or more of these treatments help? if so, which?
Would my sunny perennial beds survive a ph of 5.2? did the
diatomaceous earth damage the worms? did it damage other
critters? is it safe to broadcast diatomaceous earth over such
a large area? Maybe next time i’ll skip that.
i no longer add compost to anything. i have no idea what
we can do with the giant pile of garden waste in the back of
our property but for sure i’m NOT going to use it to feed the
worms. Where i need mulch, i use either buckwheat hulls or,
in rock garden areas, crushed rock, though i still use shredded
cedar mulch for paths. My newest gardens were planted by
hacking small holes into the dry compacted soil of the old
nursery paths, then shoving in the plants. These gardens are
doing splendidly. The new gardens contain native woodland
plants and dry-meadow plants – would this method work
for more ordinary perennials? Meanwhile, i’m experimenting
with native groundcovers, mainly Phlox stolonifera, between
the larger plants in my older, sunny perennial beds in the hope
of weaning the garden from mulch.
in 1988, i was the cover girl on the first issue of Fine
Gardening magazine. My article about how i became a
gardener emphasized my discovery of mulch and how
that made gardening possible. Garden books told me that
i should be able to dig in well-prepared soil with bare hands.
and i could. Now we have invasive Amynthas earthworms,
and my methods have changed.
This is the story of an experiment. i don’t know if one or
more of the treatments is responsible for the success of that
garden bed today. i’m not quite ready to recommend my
methods to others. But, so far, the treated garden and the
new mulch-free compost-free gardens are a success.
My favorite worm website is Great lakes Worm Watch,
www.nrri.umn.edu/worms 짮
Kathleen Nelson, a former nursery owner, is the chairperson
of the Invasive Species Advisory Committee of Mad Gardeners.
25
September/October 2014
Crazy Snake Worms
nized the role that earthworms have
played in soil formation since at least
the end of the 19th century, when assigning mor, moder and mull terminology to describe the integration of the
humus or organic component of forest
soils with the underlying mineral layer.
Briefly, a mor forest floor layer would
typically be found in conifer forests and
consist of a notable litter layer with little
mixing with the mineral soil underneath, while a mull forest floor would
be less thick, more typical of deciduous
forests, and show some signs of the mixing of organic materials and mineral
soils by a diversity or organisms, including earthworms. Moder would be somewhere in between.
In the 1980s, the Institute for Ecosystem Studies in New York wanted to
examine the health of forest ecosystems
and created a 100-mile gradient from
New York City to rural Connecticut.
One of the scientists noted areas with
hardly any leaf litter and copious
amounts of earthworms. This was not
a desirable finding in northern forests.
Our native woodlands evolved over the
last 10,000 years or so in the absence
of nature’s rototiller, the earthworm.
In undisturbed forests, the litter from
trees, shrubs and herbaceous plants
forms a protective cover over the woodland soil. The litter layer (duff) breaks
the force of raindrops, preventing soil
erosion, and retains moisture for plant
roots and other forest creatures. It provides lodging for many species of fungi
critical for forest tree survival, and
fornumerous insects and animals
such as salamanders. The litter layer
serves as a seedbed and nursery
for trees like our beloved sugar
maple, and for wildflowers like
trilliums and bloodroot.
Decomposition occurs
slowly, mainly through the
actions of decomposer fungal species and invertebrates.
Lift up a handful of litter in
an undisturbed forest floor
layer and you’ll find the delicate white fungal hyphae
coursing through the accumulated
September/October 2014
— continued from previous page
leaves, needles, twigs, branches and
other organic debris.
Since decomposition is slow, nutrient
release is slow. Trees are conservative
creatures, internally recycling many
nutrients before shedding leaves or
needles. This and other features are
adaptions to life in low-nutrient, acidic
soils naturally occurring in many areas
of New England.
Enter the earthworm. The earthworm’s goal is to turn organic matter
into soil. While this may be desirable on
cultivated lands, it is definitely a detriment in forested areas. As the litter layer
is consumed, the bare soil is exposed
to rain and wind, and erosion increases.
Nutrients held tight in the litter are
changed into available forms as they
pass through the gut of the earthworm
and any nutrients not taken up by plants
can be leached into the soil and into
water bodies. Seeds of forest trees and
flowers no longer have a germination
bed and, lacking the cover of the litter
layer, are also exposed to increased predation. As the
earthworms turn soil and
organic material into
casts the soil becomes
more and more aggregated with the increase in aeration,
causing it to dry
out. Native
plants struggle, but
conditions
are perfect for
many invasive plant
species, like garlic
mustard and honeysuckle,
to move in.
And it doesn’t take long for these
changes to occur. According to Dr.
Görres, “Within a decade or two, the
worms can essentially change the soil
profile into something like the black,
mineral-rich soils that are found in
many European forests.”
In addition, once the understory is
disturbed and most of the annual vegetation is lost, deer may start grazing
saplings of the canopy species. This
26
MORE INFORMATION
www.vtinvasives.org/otherinvasives/earthworms
www.uvm.edu/~entlab/Greenhouse%
20IPM/Workshops/2014/InvasiveEarth
worms.pdf
www.nrri.umn.edu/worms
www.epa.gov/osp/tribes/NatForum10/
ntsf10_2m_Knowles.pdf
www.harringtonsorganic.com/wpcontent/uploads/2013/11/CT-InvasiveWorms-vers-10-4-11.pdf
may suppress forest regeneration.
As if the European worms weren’t
causing enough problems
in our northern forested
ecosystems, about 70
years ago or so, another
genus of earthworms,
Amynthas, from Asia
started being detected in
New York greenhouses.
These are large, turgid,
fast-moving earthworms with
A. agrestis seemingly most common.
Amynthas species can only be identified
by dissection. Because of their frenetic
movements when disturbed they are
often referred to as Alabama jumpers or
crazy snake worms. If you were to grab
an adult by its posterior end, the body
will break away from the tail, leaving
you with a squirming piece of worm in
your hand and a surprised look on your
face while the rest of the worm quickly
slithers away.
Not only are the Amynthas launching
an accelerated assault on our forested
areas, they are causing problems on residential lots as well, with lawns, perennial, and ornamental beds seeing the
brunt of the damage. Sites rich in organic materials like compost, leaf mold
and bark mulches are all fair game.
The excessively well-aggregated soil
they create dries out quickly because of
increase air circulation and loss of that
protective, moisture retentive mulch
layer. This disrupts root growth and also
Connecticut Gardener
Crazy Snake Worms
the soil microbial community with
which many plants have formed mutually beneficial (symbiotic) relationships.
Curiously, I have found that my garden beds invaded by Amynthas all have
Jack-in-the-pulpits growing in them.
This has been noted by others, who also
found Pennsylvania sedge as an indicator of earthworm disturbance.
While we do not know the extent of
Amynthas spread in Connecticut, if it
follows the pattern in other states where
surveys were conducted, the earthworms generally follow human activity.
Most likely, as with their European
predecessors, they arrived via the horticulture and shipping industries.
Once here, earthworms and their cocoons can be spread by fisherman who
dump their unused bait by the lake, in
compost, mulch and topsoil purchases,
in the soil stuck in the wheels of ATVs
and other off-road vehicles, in potted
plants from your friends or purchased
at local plant sales, garden centers or
big box stores, and by logging trucks
and other vehicles that travel to and
from forests.
Also, earthworms can be purchased
online and are often advertised as fish
bait, vermicomposting worms, or touted
as something to be added directly to
your garden soil to make it more porous
and enhance the health of your plants!
(If you’re looking to purchase worms for
vermicomposting, only buy those listed
by their Latin name, Eisenia foetida.)
Current research is being focused
on the distribution of Amynthas species,
their devastating and far-reaching
effects on forested ecosystems and
on control methods.
As of now there is no effective control measure. In some cases, pesticides
have been tried which do kill the worms
but probably a lot of other organisms,
and once the pesticide degrades, more
worms will probably move back in.
Dr. Görres is experimenting with
some naturally derived control agents.
Sulfur used at about 6.5 ounces per
square yard reduced earthworm populations in another researcher’s experiment, but keep in mind that sulfur
will also lower the pH of your soil.
Kathleen Nelson, chairperson of the
Invasive Species Advisory Committee
of Mad Gardeners, Inc. in western Connecticut has been battling Amynthas on
her property for many years. (See box on
page 25.) Instead of quickly-degrading
wood mulches, she now uses buckwheat
hulls or gravel. Her current approach is
to stop amending the soils with organic
materials and find plants, such as
tiarella, which can tolerate unamended
Photo / Josef Görres, University of Vermont
crazy snake Worm (Amynthas agrestis) in the wood mulch of a horticultural bed
at a tree nursery in vermont. check out the white ring around the worm’s body.
in Amynthas species it stretches all around the body and it is well offset from the
rest of the body.
Connecticut Gardener
27
native soils.
That might be a suggestion, much to
many gardeners’ dismay, that we should
think more about. If we mostly grow
native plants, which tolerate our native
soils, we would not have to add copious
amounts of organic matter and mulch
to have great gardens because, by doing
so, we’re just creating invasive worm
magnets.
Also, native plants tend to prefer
low pH or acidic soils and earthworms
do not. If mulching is imperative, it is
thought that mulches with high carbon
to nitrogen ratios may be less appealing
to earthworms.
One of the UConn Master Composter interns, William Flahive, wrote
an article about a homeowner sparring
with the Amynthas that took over and
destroyed their lawn.
He called the situation, “depressing”
and I totally agree with him. When we
can’t even control the garlic mustard or
bittersweet we see above ground, how
can we control a creature below ground
that is only seen when dug up?
The best we can do at the moment
is educate ourselves, inform others
and take care not to participate in the
spreading of these destructive earthworms.
UConn’s Master Gardener and
Master Composter programs will soon
issue a survey in which gardeners will
be asked to let us know where they have
Amynthas species. This will be a first
step to understanding where we might
need to intervene to manage this
invasive species. 짮
Dawn Pettinelli is an assistant cooperative extension educator in the Department of Plant
Science at UConn.
She manages and
coordinates the
activities of the
UConn Home &
Garden Education
Center and the
UConn Soil
Dawn Pettinelli
Nutrient Analysis
Laboratory.
September/October 2014