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 (University of California, Davis) arden symphylans (Scutiger- © NCAT 2006 ella immaculata Newport) are Contents Gsmall, 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’ A garden symphylan is about the size of this letter ”l.” Sampling ...... 6 vertical movement in the soil, the com- 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 niques, crop damage associated with sym- Sampling Results ...... 9 Damage phylans has become more commonplace. Management Diagnosing a garden symphylan prob- It is ironic that these pests are such a and Control ...... 9 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- ing reduces the crop’s ability to take up ture’s Rural Business-Coopera- 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 beds, are ideal habitat for garden symphylans. agriculture projects. ���� Root damage may also render plants Eggplant stunted by garden symphylans. Undamaged eggplant of same age in same field.

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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 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 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 Some Symphyla species feed primarily on erally require the following: not insects, dead or decaying organic matter, play- G 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 Identification symphylans are by far the most com- 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 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 than 40 times (Michelbacher, 1938). nderstand- for about 25 to 40 days, when tempera- tures range from 50° to 70°F, but hatch- ing of ing occurs in about 12 days as tempera- Occurrence garden U tures reach 77°F (Berry, 1972). Understanding of garden symphylan symphylan First instars emerge from the egg with six occurrence and movement is far from occurrence and pairs of legs and six antennal segments, complete. Nonetheless, some general- 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 Pores, cracks, and holes in the soil allow symphylans to move through a field with relative ease.

arden sym- phylans Gare unable to burrow through the soil. They use pores, seasonal “Hotspots” of garden symphylan infestation show 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). In general, practices that improve soil Above: Three views of one broccoli field showing sym- 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 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 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 G standing of these interactions is impor- aggregate in the (Edwards, 1959b). Presence of garden tant both for the timing and interpre- top six inches of symphylans in the surface soil may also 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, Garden symphylans tend to aggregate in compaction from tractor tires. 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 Sampling for garden symphylans is dry or cool. cool. In Oregon, Washington, and Cali- 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 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 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 used. Sampling should be conducted to Sampling must be conducted through- Tconditions 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 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 aiting beet on the soil surface and shelter it in all conditions. Baiting works best at least two to three weeks after tillage, works best with a protective cover (e.g., a white pot or a 4-inch PVC cap). when the soil has stabilized, but before Bat 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 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%. 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- vide valuable information about the Fpurposes erately to highly susceptible crops such extent and pattern of infestation, but it is important to 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 and Fisher, 2003a). between tactics that could lead to healthy plant growth, even decrease popula- within infested soil (e.g., the planting In conventional cropping systems, two date, tillage intensity, chemical use, and to three garden symphylans per square tions and tactics 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- Control phylan population densities (estimated 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 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 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 Psignificantly field. Generally, symphylan populations Pesticides in potato crops, are thought to be home-grown and to even allowing Hundreds of compounds have been used develop over time due to favorable soil against garden symphylans in the past subsequent management practices. cultivation of 100 years, with varying efficacies (How- 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 Crop Rotation Tillage is probably the oldest control 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 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 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 Tactics to Reduce Crop increased populations in some cases. All these factors should be considered when Damage when Garden developing a weed management plan. Symphylan Populations are High Other Soil Amendments 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 M different plant species and variet- level of garden sym- izers are generally accepted to have lit- ies. In most cases tolerance to feeding phylan feeding dur- tle effect on populations, while manure applications are generally believed to seems due to increased vigor and/or ing all or part of the increase populations (Shanks, 1966). root production (e.g., broccoli, corn) 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 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 production), can also be damaged, par- bed. In some cases, increasing plant arden ticularly during establishment. Within 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- Gphylans 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 Tactics to Reduce Access of soil profile. 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 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 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 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

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