Symphylans: Soil Pest Management Options

1. Symphylans:
ATTRA Soil Pest Management Options
A Publication of ATTRA - National Sustainable Agriculture Information Service • 1-800-346-9140 • www.attra.ncat.org
By Jon Umble (Oregon Garden symphylans are soil-dwelling, centipede-like creatures that feed on plant roots and can cause
State University), extensive crop damage. They cause frequent and often misdiagnosed problems in well managed west-
Rex Dufour (NCAT ern soils with good tilth. This soil pest may not be familiar to farmers and agricultural consultants.
Agriculture Specialist), This document describes the garden symphylan life cycle and the damage symphylans can cause. It
Glenn Fisher (Oregon includes monitoring techniques to determine whether symphylans are present in the soil and sustain-
State University), able management options to prevent economic damage.
James Fisher (USDA/ARS),
Jim Leap (University of
California, Santa Cruz),
Mark Van Horn
G
(University of
California, Davis) arden symphylans (Scutiger-
© NCAT 2006 ella immaculata Newport) are
Contents small, white, “centipede-like” soil
arthropods, common in many agricultural
Damage ............................. 1 production systems in Oregon, Washing-
Identification ................... 3 ton, and California (Berry and Robinson,
Biology and Ecology ..... 3 1974; Michelbacher, 1935).
Life Cycle ........................3
They feed on roots and other subter-
Occurrence ...................4
ranean plant parts, causing significant
Movement in Soil and crop losses in some cases. Control can be
Factors Influencing
Population Levels ........ 5 extremely difficult due to symphylans’
Sampling ........................... 6 vertical movement in the soil, the com- A garden symphylan is about the size of this letter ”l.”
lexity of sampling, and the lack of sim-
Soil Sampling ................7 problem on farms that practice good soil
ple, effective control methods (Umble
Bait Sampling ...............7 management — maintaining soil with
and Fisher, 2003a).
Indirect Sampling good tilth, high organic matter, and low
Methods .........................8 With the recent spread of organic agri- compaction.
Economic Thresholds: culture and better soil management tech-
Interpretation of
Sampling Results .........9
niques, crop damage associated with sym- Damage
phylans has become more commonplace.
Management Diagnosing a garden symphylan prob-
and Control....................... 9 It is ironic that these pests are such a
lem is sometimes difficult, since damage
Tactics to Decrease may be exhibited in a number of forms
Populations ................ 10
and garden symphylans are not always
Tactics to Reduce
Damage to Crops ..... 10 easy to find, even when their damage is
References ...................... 14
obvious. Economic damage may result
from direct feeding on root and tuber
ATTRA - National Sustainable crops and reduced stands of direct-
Agriculture Information Service seeded or transplanted crops (Umble
is managed by the National
Center for Appropriate Tech- and Fisher, 2003a).
nology (NCAT) and is funded
under a grant from the United However, most commonly, root feed-
States Department of Agricul-
ture’s Rural Business-Coopera-
ing reduces the crop’s ability to take up
tive Service. Visit the NCAT Web water and nutrients, which leads to gen-
site (www.ncat.org/agri. Soils with high organic matter, good structure, and eral stunting.
html) for more informa- reduced disturbance, as in these hand-dug garden
tion on our sustainable
agriculture projects. ����
beds, are ideal habitat for garden symphylans. Root damage may also render plants

2. Eggplant stunted by garden symphylans. Undamaged eggplant of same age in same field.
Related ATTRA
Publications
Sustainable Soil
Management
Sustainable
Management of Soil-
Borne Plant Diseases
Symphylan damage can be hard to diagnose because it may seem to be from other causes. This photo shows
Pursuing Conservation two rows of eggplant, one that is severely stunted and one less so. Neither the rows to the left nor the peppers on
Tillage Systems for the right seem to be affected. It is likely that the timing of planting and tillage influences the amount of damage
Organic Crop that symphylans cause. Many factors may interact to promote or reduce symphylan damage: conditions when
Production the soil is tilled, time after tillage, heat requirements of the crop, irrigation management, size of the plant, etc.
Soil Managment:
National Organic
Program Regulations
Typical perplexing symphylan damage: Some rows of peppers (above, left) are severely stunted, while adjacent
rows have both healthy and stunted plants. Symphylan damage can be mistaken for skipped seeding or poor
seed-to-soil contact, as in these fields of squash (above, right), sweet corn, and tomatoes (below, left and right)
Page 2 ATTRA Symphylans: Soil Pest Management Options

3. Certain areas of this squash field are laid to waste by Typical symphylan damage, showing healthy plants
symphylans, while other sections thrive. alongside stunted plants and empty areas.
more susceptible to some soil-borne pair per body segment) and quick move-
plant pathogens. Correct diagnosis of ments. Millipedes are generally slower
G
garden symphylan problems and identi- moving, with two pairs of legs on each
fication of appropriate management tac- body segment. arden sym-
tics for a given cropping system will gen- phylans are
erally require the following: Some Symphyla species feed primarily on not insects,
dead or decaying organic matter, play-
but members of the
1.) Sampling to determine whether ing an important role in cycling nutri-
garden symphylans are present in ents. Other species, such as the garden class Symphyla
damaging numbers symphylan, are serious pests, primarily
feeding on living plants.
2.) A general knowledge of manage-
ment tactics and garden symphylan Several Symphyla species are present in
ecology to select the specific tactics the western United States; however, the
that will be most effective in a given garden symphylan is the only Symphyla
cropping system species that is documented to cause crop
damage in the western U.S. Garden
symphylans are by far the most com-
Identification mon Symphyla species found in agricul-
Garden symphylans are not insects, but tural systems.
members of the class Symphyla. Species
of this class are common soil arthropods If Symphyla are found in an agricul-
worldwide. Symphyla are small, whit- tural system at a high density, concen-
ish “centipede-like” creatures rang- trated around the roots of plants, they
ing from less than 1/8 inch up to about are likely to be garden symphylans. The
5/8 inch (or 1/4 inch for garden sym- pest is not known to vector any plant dis-
phylans) (Edwards, 1990). They have 6 eases, although extensive research on the
to 12 pairs of legs (depending on age), question has not been conducted.
which makes them easy to distinguish
from common soil insects (e.g., spring-
tails) and diplurans that have only three
Garden Symphylan
pairs of legs, all on the thorax, or mid- Biology and Ecology
dle body segment.
Life Cycle
Though their color may vary, depending
on what they have eaten, garden sym- In the western U.S., eggs, adults, and
phylans are generally whiter and smaller immature garden symphylans can be
than true centipedes, which are also soil found together throughout most of the
arthropods with many pairs of legs (one year. Temperature plays a key role in
www.attra.ncat.org ATTRA Page 3

4. Garden Symphylan eggs Newly emerged
(Photo credit: Ralph Berry) symphylans (first instar)
Mature adult garden symphylan
(Photo credit: Ralph Berry)
regulating oviposition (egg laying), and three months at 70°F and less than two
the greatest numbers of eggs are usu- months at 77°F. Therefore, it may be
ally deposited in the spring and fall possible to have two complete genera-
(Berry, 1972). tions a year (Berry, 1972). Interestingly,
Eggs are pearly white and spherical with unlike adult insects, which do not molt,
hexagonal shaped ridges. Eggs incubate adult garden symphylans may molt more
U
for about 25 to 40 days, when tempera- than 40 times (Michelbacher, 1938).
nderstand-
tures range from 50° to 70°F, but hatch-
ing of
ing occurs in about 12 days as tempera- Occurrence
garden tures reach 77°F (Berry, 1972). Understanding of garden symphylan
symphylan occurrence and movement is far from
First instars emerge from the egg with six
occurrence and complete. Nonetheless, some general-
pairs of legs and six antennal segments,
movement is far their bodies covered with fine hairs. izations can be made both about soils in
from complete. Slow movements and a swollen posterior which garden symphylans occur more
make first instars appear superficially commonly and about their movement in
more like a collembolan than an adult soils. Garden symphylan populations
garden symphylan. These first instars, are highly aggregated within fields and
however, are rarely found in the root- on a larger scale.
ing zone and within days molt to second
In Oregon, Washington, and Califor-
instars that resemble small adult garden
nia, garden symphylans are more com-
symphylans (Michelbacher, 1938).
mon in the western regions of the states.
Each of the six subsequent molts results Within these regions, garden sym-
in the addition of a pair of legs and vari- phylans tend to occur in heavier irri-
able numbers of body and antennal seg- gated soils, and within these heavier
ments. Total time from egg to sexually soils, garden symphylans tend to occur
mature adult (seventh instar) is about in “hotspots” of a few square feet to sev-
five months at 50°F, decreasing to about eral acres. Even within shovelfuls of
Fields often show symphylan damage in the same places over many seasons, as on these two farms.
Page 4 ATTRA Symphylans: Soil Pest Management Options

5. Pores, cracks, and holes in the soil allow symphylans
to move through a field with relative ease.
G
arden sym-
phylans
are unable
to burrow through
the soil. They use
“Hotspots” of garden symphylan infestation show
pores, seasonal
clearly in this aerial view of a broccoli field. cracks and
burrows made by
soil, garden symphylans often occur in other soil animals,
very distinct aggregations.
such as earthworms,
Garden symphylans are unable to bur- to travel through the
row through the soil. They use pores, soil profile
seasonal cracks and burrows made
by other soil animals, such as earth-
worms, to travel through the soil pro-
file (Edwards, 1961).
Above: Three views of one broccoli field showing sym-
In general, practices that improve soil
phylan damage.
structure (e.g., addition of organic
matter, reduced tillage, raised beds) In the Pacific Northwest and Northern
improve the ability of garden sym- California, garden symphylans are com-
phylans to move through the soil, lead- monly found in alluvial soils, and are
ing to increased populations and/or likely spread to some extent by flooding.
increased damage through improved Relative soil acidity does not appear to
access to roots. As a result, high pop- be closely correlated with garden sym-
ulations of garden symphylans are phylan occurrence, since symphylans
more commonly found in fine-textured, are found in very acid soils (e.g., where
heavier soils with moderate or better blueberries grow) to fairly alkaline soils
structure and many macropores, rather (e.g., pH 8+).
than in sandy soils (Edwards, 1958;
Edwards, 1961). When garden sym- Hot spots within infested fields often
phylans are found in sandier soils, these remain consistent from year to year
soils have commonly been amended with with little change in populations and
organic matter. only minor lateral spread, possibly due
www.attra.ncat.org ATTRA Page 5

6. to physical characteristics of the soil. atures exceed 95°F), if sufficient mois-
However, changes in hotspots do occur ture is present and roots are shallow or
(Umble and Fisher, 2003c). absent. In the hottest interior valleys,
symphylans may be more active in the
Symphylan Movement in the spring/early summer and the fall, with
surface activity dropping off in July,
Soil and Factors Influencing August, and into September.
Population Levels Garden symphylans migrate to the sur-
If the soil environment is favorable, gar- face soil (the root zone) to feed, then
den symphylans may migrate from the return to the deeper strata to molt, as
soil surface to a depth of more than 3 demonstrated by the large number of
feet. The soil profile, including com- molted skins that are observed in these
pacted or sandy horizons and high water strata. When garden symphylans are
tables that may impede movement, deter- feeding ravenously after molting, they
mines the depth to which garden sym- may enter the surface soil zone even
phylans may migrate. Timing of vertical in generally unfavorable (e.g., hot and
G
migrations is primarily due to the inter- dry) conditions. Since migrations are
arden sym- action among moisture, temperature, not synchronized, portions of the pop-
phylans and internally regulated feeding cycles ulation are usually present throughout
tend to (Edwards, 1959b). A general under- the habitable portion of the soil profile
aggregate in the standing of these interactions is impor- (Edwards, 1959b). Presence of garden
tant both for the timing and interpre- symphylans in the surface soil may also
top six inches of
tion of sampling efforts and for selecting be influenced by other variables that
soil when the soil management tactics. impede movement, such as tillage and
is moist and warm, compaction from tractor tires.
Garden symphylans tend to aggregate in
and move to deeper the top six inches of soil when the soil
soil strata when the is moist and warm, and move to deeper Sampling
soil becomes very soil strata when soil becomes very dry or
cool. In Oregon, Washington, and Cali- Sampling for garden symphylans is
dry or cool.
fornia, garden symphylans are generally extremely important for identifying
found in the surface soil from March damage, for making informed manage-
through November, with the highest ment decisions, and for evaluating the
surface populations observed in May effects of those decisions. Sampling,
and June. Garden symphylans may be however, is often difficult. Three main
found in the surface soil when conditions sampling methods are used: baiting, soil
are fairly warm (e.g., when air temper- sampling, and indirect sampling. Each
method has benefits and drawbacks, and
the selection of a sampling method will
General Decision Guidelines for Sampling vary, depending on the objectives of the
To detect or identify a symphylan problem with a growing crop: sampling (e.g., detection vs. precise esti-
mate of population density), the time of
• Dig up stunted plants and weeds in the morning; examine their
year, and the site conditions.
roots for symphylans.
• If it’s within about three weeks after planting, put out baits for Part of the difficulty in sampling is due
garden symphylans in suspected problem areas. to the patchy distribution of populations.
It is important to be aware that an indi-
To estimate population density and/or make decisions before plant-
vidual sample count provides informa-
ing a crop:
tion only about the region near where
• Take soil samples if the soil is cool or very dry, if the field is very that sample was taken. Counts will often
weedy, or if a cover crop is growing. vary from 0 to more than 50 garden sym-
• Use bait sampling if the soil is warm and moist with sparse veg- phylans per sample. To get information
etation or if the soil is bare. about the spatial patterns of the popula-
Page 6 ATTRA Symphylans: Soil Pest Management Options

7. tion, it is best to take sample units in a
grid pattern. Sorting and comparing the
samples by site factors such as soil type,
drainage, and cropping history may pro-
vide valuable information about the dis-
tribution of populations within a site.
In most cases, sampling measures only
the density of symphylans in the surface
soil; therefore, sampling should only be
conducted when garden symphylans are Soil sampling in corn is carried out by placing soil
in the surface soil. The best sampling on a black tarp and then carefully searching for
garden symphylans.
conditions are generally warm, moist
soil. Sampling within three weeks after When soil samples are taken, the soil
major tillage—such as discing, plowing, from each sample unit is usually placed
or spading—is often inaccurate, since on a piece of dark plastic or cloth, where
garden symphylans may not have had
T
the aggregates are broken apart and the
ample time to re-establish in the surface garden symphylans are counted (Berry he best
soil. If sampling is conducted soon after and Robinson, 1974). sampling
tillage, soil sampling methods should be
Sampling must be conducted through- conditions
used. Sampling should be conducted to
a depth that includes several inches of out the entire habitable region of the soil are generally warm,
soil undisturbed by tillage. profile (i.e., possibly to a depth of more moist soil.
than three feet) to obtain accurate popu-
lation density estimates, but this is rarely
Soil Sampling done, because of the extensive time and
Soil sampling is the standard/historic resources required. Therefore, sam-
method for estimating how many garden pling is usually conducted when garden
symphylans are present in a field (i.e., symphylans are believed to be in the top
approximate number of garden sym- 6 to 12 inches of the root zone. Shal-
phylans per unit of soil, or estimated low sampling (e.g., to a depth of 4 inches)
population density) (Berry and Robin- saves time and allows larger areas to be
son, 1974). Sample unit sizes vary. The sampled, but deeper sampling (e.g., to
most common soil sample units have a depth of 12 inches) is generally more
been the following. reliable. Sampling is not recommended
in very dry conditions.
• A 1-foot cube
• A 6-inch square, 1-foot deep Bait Sampling
• A “shovelful” In recent years, bait sampling methods
• Cores 3 to 4 inches in diameter have been developed. Bait samples are
and 4 to 12 inches deep. generally much faster to take than soil
Using a cut potato as bait to check for the presence of garden symphylans.
www.attra.ncat.org ATTRA Page 7

8. A field showing symphylan sampling stations. Poor plant growth in certain distinct areas of a field
may or may not indicate a symphylan problem.
samples, but they are also more variable
conditions, baits are commonly left out
and more sensitive to factors such as soil for three to five days.
moisture, temperature, and the presence
of vegetation (Umble and Fisher, 2003b). Bait sampling works very well for some
To bait sample, place half of a potato or applications, though it cannot be used
B
aiting beet on the soil surface and shelter it in all conditions. Baiting works best
with a protective cover (e.g., a white pot at least two to three weeks after tillage,
works best
or a 4-inch PVC cap). when the soil has stabilized, but before
at least two plants are well established. If travel to
to three weeks after One to three days after placement, lift the sampling location requires signifi-
tillage, when the soil the bait and count first the garden sym- cant resources, soil sampling methods
has stabilized, but phylans on the soil and second the gar- may be preferred, because they require
den symphylans on the bait. During only one trip to the site.
before plants are
warm and/or dry conditions, baits are
well established. generally checked one to two days after Indirect Sampling Methods
placement, as counts decrease if baits Plant growth can sometimes be a useful
are left out for multiple days. In cooler indirect measure of garden symphylan
How Many Soil or Bait Sample Units to Use?
When sampling for garden symphylans, a critical number of sample units (i.e. “chunks” of soil or
baits) are required in order to have a reasonable level of confidence about the estimated popu-
lation density (e.g., garden symphylans per square foot) (Umble and Fisher, 2003b). Confidence
in this estimate increases as more samples are taken. Sampling involves establishing a balance
between wanting to be fairly confident about the number of garden symphylans present (taking
a large number of samples) and not investing excessive time and energy in the sampling endeavor
(taking a small number of samples).
Use the following general guidelines to determine the appropriate number of sample units.
• Simply detecting the presence of garden symphylans may only require digging up 5 to
10 damaged plants, or using a low number of baits (e.g., 5)
• Sampling for low population densities (early in the spring or in highly susceptible crops)
requires more sample units (e.g., 100+) than sampling for high population densities
(e.g., 30)
• As the variability of a sampling method increases, so does the number of sample units
required. Since the baiting method is more variable than the soil sampling method,
two to three times more baits are required than soil samples
• To estimate “economically damaging” population densities in moderately susceptible
crops, at least 35 soil sample units or at least 50 bait samples are commonly set out.
Depending on the size of the field and the time of year, considerably more sample units
may be used.
Page 8 ATTRA Symphylans: Soil Pest Management Options

9. Spinach seedlings show susceptibility to symphylan Corn seedlings show little susceptibility to symphylan
damage. The soil in the pot on the left contains 45 damage. Soil in the pot on the left has no symphylans
symphylans. Soil in the pot on the right has no in it. The soil in the pot on the right contains 45
symphylans in it. symphylans.
lings of crops such as snap beans, spin-
populations and is often a good start-
ach, and sweet corn (Umble and Fisher,
ing point for assessing their spatial pat-
2003a; Eltoum and Berry, 1985). The
terns (Umble and Fisher, 2003a). For
higher density of 45 garden symphylans
example, healthy plants sometimes indi-
per pot has been shown to reduce the
cate low garden symphylan populations
growth of tomatoes and spinach seed-
and conversely, unhealthy plants some-
lings by more than 90%.
F
times indicate high garden symphylan
populations. In the field, noticeable damage often or manage-
occurs if garden symphylans exceed an ment
Indirect measures such as this may pro-
average of 5 to 10 per shovelful in mod- purposes
vide valuable information about the
erately to highly susceptible crops such it is important to
extent and pattern of infestation, but
as broccoli, squash, spinach, and cab-
they should not be used in place of direct make a distinction
bage (Berry and Robinson, 1974; Umble
sampling. This is because many factors between tactics that
and Fisher, 2003a).
could lead to healthy plant growth, even decrease popula-
within infested soil (e.g., the planting In conventional cropping systems, two
tions and tactics
date, tillage intensity, chemical use, and to three garden symphylans per square
crop species). foot is commonly used as a treatment that reduce damage
threshold. to crops but may not
Action Thresholds: Because of the considerable variability necessarily decrease
Interpretation of of symphylan densities within a field, populations.
sample unit counts may range from 0 to
Sampling Results more than 100. These results are helpful
Management decisions, such as those in locating field hot spots. In more toler-
regarding pesticide applications and the ant crops, such as potatoes, beans, and
intensity of tillage, are sometimes based small grains, garden symphylan feeding
on pre-planting density estimates of gar- may not lead to significant damage, even
den symphylan population. Owing par- at considerably higher population densi-
tially to the many crops in which garden ties (Umble and Fisher, 2003a).
symphylans are pests, thresholds for
individual crops are not well developed. Management and
The relationship between garden sym-
phylan population densities (estimated
Control
Many factors influence garden sym-
by sampling methods) and measures
phylan population levels (Howitt and
such as stand count and yield are influ-
Bullock, 1955; Umble and Fisher, 2003c;
enced by factors such as crop type, till-
Getzin and Shanks, 1964; Shanks, 1966).
age intensity, and crop stage (Umble and
However, because it is difficult to accu-
Fisher, 2003a). rately sample populations, information
In the laboratory, levels as low as 5 to about the true effects of many factors
15 garden symphylans per pot have been on garden symphylans is scant at best.
shown to reduce the growth of seed- For management purposes it is impor-
www.attra.ncat.org ATTRA Page 9

10. tant to make a distinction between tac- been shown to be as effective as tillage
tics that decrease populations and tac- in decreasing garden symphylan popula-
tics that reduce damage to crops but may tions. When considering increased till-
not necessarily decrease populations. In age, farmers need to balance the bene-
most cases, effective garden symphylan fits and the costs, such as oxidized soil
management involves establishing a bal- organic matter, compacted soil, and
ance between these two strategies. It is increased expenses for time, fuel, and
important to keep in mind that in most worn equipment.
cases, after damage is noticed, little can
In general, for the most effective control,
be done without replanting. Sampling
till when the garden symphylans are in
is, therefore, important in determining
the surface soil and when soil moisture
the proper course of action.
allows preparation of a fine seed bed.
It is unknown whether symphylan pop- Since only a portion of the symphylan
ulations may develop from transported population is in the surface soil, tillage
soil or compost. These are certainly never provides complete control. How-
possible sources of infestation, and it is ever, surface populations are generally
P
recommended to sample soil and com- significantly lower for at least two to
opulations
post (from on- or off-site) for symphylans three weeks after tillage.
decrease
before applying these amendments to a
significantly
in potato crops,
field. Generally, symphylan populations Pesticides
are thought to be home-grown and to Hundreds of compounds have been used
even allowing develop over time due to favorable soil
subsequent against garden symphylans in the past
management practices. 100 years, with varying efficacies (How-
cultivation of
susceptible crops in itt and Bullock, 1955). Fumigants and
rotation Tactics to Decrease organophosphate pesticides have been
Populations the most effective, but many of these
Reducing populations has been the focus are no longer registered. Pesticides may
of many studies (Howitt and Bullock, have the effect of both killing garden
1955; Umble and Fisher, 2003c; Getzin symphylans and repelling them from
and Shanks, 1964; Shanks, 1966; How- the surface soil. Less toxic pesticides
itt, 1959; Peachey et al., 2002). Though (e.g., pyrethroids and other natural pes-
no “silver bullets” have been identified, ticides) have not been shown to provide
some tactics are available. Probably acceptable control. Pesticides gener-
no method will eradicate garden sym- ally provide the greatest amount of con-
phylans from a site, and the effect of trol when they are broadcast and incor-
most tactics will not last longer than one porated, though banded and injected
to three years. applications can provide an acceptable
level of control.
Tillage
Tillage is probably the oldest control
Crop Rotation
tactic, and it is still one of the most effec- Although garden symphylans feed on a
tive (Martin, 1948;Peachey et al., 2002). wide range of plants, they can also per-
Tillage can physically crush garden sist in bare soil by feeding on other soil
symphylans, thus reducing populations. organisms. Plants vary greatly in their
Tillage may also harm populations of susceptibility to garden symphylans.
key garden symphylan predators such Crop rotation may partially explain
as centipedes and predaceous mites. seemingly sudden shifts in garden sym-
However, in annual cropping systems, phylan population levels. Populations
the benefits of increased predator pop- decrease significantly in potato crops,
ulations from reduced tillage have not even allowing subsequent cultivation of
Page 10 ATTRA Symphylans: Soil Pest Management Options

11. Damaged and undamaged broccoli planted at the same time in the same field.
Damaged and undamaged cucumbers planted at the same time in the same field.
Damaged and undamaged sunflowers planted at the same time in the same field.
Damaged and undamaged peppers in the same field, planted at the same time.
www.attra.ncat.org ATTRA Page 11

12. susceptible crops in rotation (Umble and or part of the growing season, and two
Fisher, 2003c). Though no other crops general tactics can help to grow healthy
have been shown to be nearly as effec- crops in symphylan-infested soil. These
tive at reducing symphylan populations tactics are those aimed at reducing crop
as potatoes, symphylan populations damage when garden symphylan popula-
are lower after a spring oat (‘Monida’) tions are high, and those aimed at reduc-
winter cover crop than after a mustard ing the number of garden symphylans on
(‘Martiginia’), barley (‘Micah’), or rye crop roots during establishment, when
(‘Wheeler’) winter cover crop (Peachey plants are often most susceptible.
et al., 2002). Mustard and spinach crops
are very good hosts and may lead to
increased populations in some cases. All
Tactics to Reduce Crop
these factors should be considered when Damage when Garden
developing a weed management plan. Symphylan Populations
are High
Other Soil Amendments
M
The reported effects of common soil Crop Species/Variety
ost plants amendments such as manure, lime, fer-
can toler- tilizers, and compost vary greatly and Susceptibility to garden symphylan
ate some are often contradictory. Lime and fertil- feeding can vary dramatically between
level of garden sym- izers are generally accepted to have lit- different plant species and variet-
tle effect on populations, while manure ies. In most cases tolerance to feeding
phylan feeding dur-
applications are generally believed to seems due to increased vigor and/or
ing all or part of the root production (e.g., broccoli, corn)
increase populations (Shanks, 1966).
growing season The effect of compost and organic (Umble and Fisher, 2003a; Simigrai
amendments on garden symphylan pop- and Berry, 1974). In some cases gar-
ulations has been variable, but at this den symphylans may simply eat less of
point none have been shown to consis- certain crops/varieties, though this has
tently and significantly reduce garden not been demonstrated experimentally.
symphylan populations. Generally, smaller-seeded crops tend to
be more susceptible than larger-seeded
Tactics to Reduce Damage crops (Umble and Fisher, 2003a). Com-
to Crops monly damaged crops include broccoli
Most plants can tolerate some level of and other cole crops, spinach, beets,
garden symphylan feeding during all onions, and squash.
Potatoes planted under broccoli at UC Davis Student Farm. Potatoes planted between blocks of sweet corn in intercrop trial at
UC Santa Cruz Farm & Garden. Photo by Jim Leap.
Page 12 ATTRA Symphylans: Soil Pest Management Options

13. Perennial crops also can be damaged when symphylans are present. Left: blueberries. Right: Hybrid poplars.
Beans and potatoes are rarely damaged, The number of garden symphylans
even under high populations. Perennial feeding on each plant in a local region
crops, such as strawberries, raspber- (e.g., raised bed) is partially a factor
ries, hops, and bare root trees (nursery of the number of plants present in that
G
production), can also be damaged, par- bed. In some cases, increasing plant
ticularly during establishment. Within arden
density—which of course must be bal-
a crop species, such as broccoli, some anced with plant competition consid- sym-
varieties are more tolerant of garden erations—brings about improved pro- phylans
symphylans than others (Simigrai and duction. Modifications of this strategy do not cross the soil
Berry, 1974). include planting an early “distraction” surface for
or “dilution” crop in a bed or adjacent significant
Crop Stage to a cropping row. distances, as do
Within a crop, susceptibility is often ground beetles.
related to the developmental stage of A good dilution crop is a low-cost, vig-
However, they are
the crop. For example, within a tomato orous, easy-establishing crop (e.g.,
variety, direct-seeded tomatoes are more sudangrass in suitable conditions) that quite active and
susceptible than 4-week-old transplants, increases the roots in the soil and effec- surprisingly mobile
which are more susceptible than 12- tively “dilutes” the garden symphylans for their size,
week-old transplants. Using transplants enough to get the target crop established. moving vertically
or increasing transplant size to reduce The dilution crop is then removed as the and horizontally
damage is not effective for all crops. target crop establishes.
Transplants of broccoli and eggplant, through the
for example, often fail to establish under soil profile.
Tactics to Reduce Access of
high garden symphylan populations.
Garden Symphylans to
Plant Density Crop Roots
Since garden symphylans are not able to
Garden symphylans do not cross the burrow through soil, instead relying on
soil surface for significant distances, soil pores and channels made by roots
as do ground beetles. However, they and other soil organisms, their access
are quite active and surprisingly to roots is strongly correlated with soil
mobile for their size, moving vertically structure, bulk density (“fluffiness”) of
and horizontally through the soil pro- the soil, and pore connectivity. In gen-
file. This is strikingly evident when, eral, the following tactics focus on tem-
for example, seedlings transplanted porarily reducing the number of garden
into a stale seedbed with seemingly few symphylans in the surface soil before
garden symphylans have garden sym- planting, thus allowing crops to estab-
phylans crawling all over their roots lish while garden symphylan numbers
less than one day after planting. are low.
www.attra.ncat.org ATTRA Page 13

14. Tillage Compaction/Raised Beds
Along with directly killing garden sym- The protection of plant roots from gar-
phylans, tillage breaks apart soil aggre- den symphylans is sometimes evident
gates, modifying soil pores and pore in zones where tractor tires have com-
connectivity. The effects of tillage vary pacted the soil, or in areas where a roto-
with the types of implements used. In tiller or disc has formed a compacted
general, the more disruptive the till- layer or “plow pan.”
age, the greater the effect it will have on Although compaction can have some
garden symphylans. Plowing or disc- negative effects, in some soils it is pos-
ing, followed by thorough preparation sible to compact the soil beneficially
of a fine seed bed using a rototiller or using, for example, a landscaping roller,
roterra, often reduces surface-feed- thus reducing garden symphylan move-
ing garden symphylan populations for ment enough to allow plants to estab-
two to three weeks. Over this period of lish. The opposite conditions often
time, pores are formed as some aggrega- occur in raised beds that are highly
tion occurs, and earthworms and plant amended with organic matter, where the
roots make new channels through the soil is very low in bulk density and gar-
soil. Less intense soil disturbance, such den symphylans are able to move freely
as hand digging or shallow cultivation throughout the beds.
with a harrow or strip tiller, may have
a significantly less disruptive effect on
garden symphylans.
Research for this publication was funded by a Research and Education grant from the USDA’s
Western Sustainable Agriculture Research and Education program (Western SARE).
Plants growing in the compacted soil of tire tracks in an otherwise bare, symphylans-infested field.
Page 14 ATTRA Symphylans: Soil Pest Management Options

15. Garden Symphylan Filinger, G. A. 1928. Observations on the habits
and control of the garden centipede, Scutigerella
References immaculata, Newport, a pest in greenhouses. J.
Berry, R. E. 1972. Garden symphylan: Reproduc- Econ. Entomol. 2: 357-360.
tion and development in the laboratory. (Scutiger-
ella immaculata). Journal of Economic Entomol- Filinger, G. A. 1931. The Garden Symphylid. Ohio
ogy. Vol. 65. p. 1628-1632. Agr. Exp. Sta. Bul. 486: 1-33.
Berry, R. E. 1973. Biology of the predaceous mite, Getzin, L. W., and C. H. Shanks. 1964. Infection
Pergamasus quisquiliarum, on the garden sym- of the garden symphylan, Scutigerella immacu-
phylan, Scutigerella immaculata, in the labora- lata (Newport), by Entomophthora coronata (Con-
tory. Ann. Entomol. Soc. Am. 66: 1354-1356. stantin) Kevorkian and Metarrhizium anisopliae
(Metchnikoff) Sorokin. J. Insect Path. 6: 542-543.
Berry, R. E., and R. R. Robinson. 1974. Biol-
ogy and control of the garden symphylan. Oregon Gould, G. E., and C. A. Edwards. 1968. Damage to
State University. Extension Service. Extension field corn by symphylans. Proc. Indiana Acad. Sci.
Circular 845. 77: 214-221.
Edwards, C. A. 1957. Simple techniques for rear- Howitt, A. J. 1959. Control of Scutigerella immac-
ing Collembola, Symphyla and other small soil- ulata (Newport) in the Pacific Northwest with soil
inhabiting arthropods, pp. 412-416. In D. K. M. fumigants. J. Econ. Entomol. 52: 678-683.
Kevan [ed.], Soil Zoology. Butterworths Publica- Howitt, A. J., and R. M. Bullock. 1955. Control
tions Ltd., London. of the garden centipede. J. Econ. Entomol. 48:
Edwards, C. A. 1958. The ecology of Symphyla: 246-250.
part I. populations. Entomologia Experimentalis et Illingworth, J. F. 1927. Symphylids destructive to
Applicata 1: 308-319. the roots of pineapple. Pineapple News Mar-Dec:
Edwards, C. A. 1959a. Keys to the genera of the 88-91.
Symphyla. Journal of the Linnean Society XLIV: Koontz, F. R. 1968. Biological and ecological rela-
164-169. tionships of the fungus, Entomophthora coronata
Edwards, C. A. 1959b. The ecology of Symphyla: (Constantin) Kevorkian, and the garden symphylan,
part II. seasonal soil migrations. Entomologia Scutigerella immaculata (Newport). Ph.D. disser-
Experimentalis et Applicata 2: 257-267. tation, Oregon State University, Corvallis.
Edwards, C. A. 1961. The ecology of Symphyla: Martin, C. H. 1948. Movement and seasonal popu-
part III. factors controlling soil distributions. Ento- lations of the garden centipede in greenhouse soil.
mologia Experimentalis et Applicata 4: 239-256. J. Econ. Entomol. 41: 707-715.
Edwards, C. A. 1990. Symphyla, pp. 891 - 910. Michelbacher, A. E. 1935. The economic status
In D. L. Dindal [ed.], Soil biology guide. Wiley, of the garden centipede, Scutigerella immacu-
New York. lata (Newp.) in California. J. Econ. Entomol. 28:
1015-1018.
Edwards, C. A., and E. B. Dennis. 1962. The sam-
pling and extraction of Symphyla from soil, pp. Michelbacher, A. E. 1938. The biology of the gar-
300-304. In P. W. Murphy [ed.], Progress in Soil den centipede Scutigerella immaculata. Hilgardia
Zoology. Butterworths, London. 11: 55-148.
Eltoum, E. M. A., and R. E. Berry. 1985. Influ- Michelbacher, A. E. 1939. Seasonal variation in the
ence of garden symphylan (Symphyla: Scutigerelli- distribution of two species of Symphyla from Cali-
dae) root injury on physiological processes in snap fornia. J. Econ. Entomol 32: 53-57.
beans. Environ. Entomol. 14: 408-412. Michelbacher, A. E. 1949. The ecology of Symphyla.
The Pan-Pacific Entomol. 25: 1-12.
www.attra.ncat.org ATTRA Page 15

16. Peachey, E., A. Moldenke, R. D. William, R. Berry, Umble, J. R., and J. R. Fisher. 2003a. Influence of
E. Ingham, and E. Groth. 2002. Effect of cover below-ground feeding by garden symphylans (Ceph-
crops and tillage system on symphylans (Symphyla: alostigmata: Scutigerellidae) on plant health. Envi-
Scutigerella immaculata) and other soil biota in ronmental Entomology 32: 1251-1261.
agricultural soils. Appl. Soil Ecol. 21: 59-70.
Umble, J. R., and J. R. Fisher. 2003b. Sampling
Riley, H. K. 1929. The greenhouse centipede. Indi- considerations for garden symphylans, Scutigerella
ana Agr. Exp. Sta. Bul. 331: 1-14. immaculata Newport, in western Oregon. Journal
of Economic Entomology 96: 969-974.
Scheller, U. 1986. Symphyla from the United
States and Mexico. Texas Mem. Mus., Speleol. Umble, J. R., and J. R. Fisher. 2003c. Suitabil-
Monogr., 1: 87-125. ity of selected crops and soil for garden symphylan
(Symphyla, Scutigerellidae: Scutigerella immacu-
Sechriest, R. E. 1972. Control of the garden sym-
lata Newport) population development. Journal of
phylan in Illinois cornfields. J. Econ. Entomol.
Applied Soil Ecology 24: 151-163.
65: 599-600.
Waterhouse, J. S. 1969. An evaluation of a new pre-
Shanks, C. H. 1966. Factors that affect reproduc-
daceous centipede Lamyctes sp., on the garden sym-
tion of the garden symphylan, Scutigerella immac-
phylan Scutigerella immaculata. Can. Entomol.
ulata. J. Econ. Entomol. 59: 1403-1406.
101: 1081-1083.
Simigrai, M. and R.E. Berry. 1974. Resistance in
Waterhouse, J. S., R. Seymour, and E. W. Rut-
broccoli to the garden symphylan. J. Econ. Ento-
kowski. 1969. Biological effects of starvation on the
mol. 67: 371-373.
garden symphylan. J. Econ. Entomol. 62: 338-341.
Stimmann, M. W. 1968. Effect of temperature on
Woodworth, C. W. 1905. A new centipede of eco-
infection of the garden symphylan by Entomoph-
nomic importance. Calif. J. Tech. 6: 38-42.
thora coronata. J. Econ. Entomol 61: 1558-1560.
Wymore, F. H. 1931. The garden centipede. Cali-
Swenson, K. G. 1965. Infection of the garden sym-
fornia Experiment Station Bulletin 518: 1-22.
phylan, Scutigerella immaculata, with the DD-136
nematode. J. Invert. Path. 8: 133-134.
Symphylans: Soil Pest Management Options
By Jon Umble (Oregon State University)
Rex Dufour (NCAT Agriculture Specialist)
Glenn Fisher (Oregon State University)
James Fisher (USDA/ARS)
Jim Leap (University of California, Santa Cruz)
Mark Van Horn (University of California, Davis)
©NCAT 2006
Paul Williams, Editor
Karen Van Epen, Production
Photographs by Jon Umble, unless otherwise noted
This publication is available on the Web at:
www.attra.ncat.org/attra-pub/symphylans.htm
www.attra.ncat.org/attra-pub/PDF/symphylans.pdf
IP283
Slot 283
Version 21506
Page 16 ATTRA