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Symphylans: Soil Pest Management Options

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Symphylans: Soil Pest Management Options

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Symphylans: Soil Pest Management Options

  1. 1. Symphylans: ATTRA Soil Pest Management Options A Publication of ATTRA - National Sustainable Agriculture Information Service • 1-800-346-9140 • www.attra.ncat.orgBy 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. ItGlenn 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) areContents small, white, “centipede-like” soil arthropods, common in many agriculturalDamage ............................. 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 isReferences ...................... 14 obvious. Economic damage may result from direct feeding on root and tuberATTRA - National Sustainable crops and reduced stands of direct-Agriculture Information Service seeded or transplanted crops (Umbleis managed by the NationalCenter for Appropriate Tech- and Fisher, 2003a).nology (NCAT) and is fundedunder 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 uptive 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 gardention on our sustainableagriculture projects. ���� beds, are ideal habitat for garden symphylans. Root damage may also render plants
  2. 2. Eggplant stunted by garden symphylans. Undamaged eggplant of same age in same field.Related ATTRAPublicationsSustainable SoilManagementSustainableManagement of Soil-Borne Plant Diseases Symphylan damage can be hard to diagnose because it may seem to be from other causes. This photo showsPursuing Conservation two rows of eggplant, one that is severely stunted and one less so. Neither the rows to the left nor the peppers onTillage Systems for the right seem to be affected. It is likely that the timing of planting and tillage influences the amount of damageOrganic Crop that symphylans cause. Many factors may interact to promote or reduce symphylan damage: conditions whenProduction the soil is tilled, time after tillage, heat requirements of the crop, irrigation management, size of the plant, etc.Soil Managment:National OrganicProgram 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. 3. Certain areas of this squash field are laid to waste by Typical symphylan damage, showing healthy plantssymphylans, 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 Ggarden symphylan problems and identi- moving, with two pairs of legs on eachfication of appropriate management tac- body segment. arden sym-tics for a given cropping system will gen- phylans areerally 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. Speciesof 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, theying from less than 1/8 inch up to about are likely to be garden symphylans. The5/8 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 theto 12 pairs of legs (depending on age), question has not been conducted.which makes them easy to distinguishfrom common soil insects (e.g., spring-tails) and diplurans that have only three Garden Symphylanpairs of legs, all on the thorax, or mid- Biology and Ecologydle body segment. Life CycleThough their color may vary, dependingon what they have eaten, garden sym- In the western U.S., eggs, adults, andphylans are generally whiter and smaller immature garden symphylans can bethan true centipedes, which are also soil found together throughout most of thearthropods with many pairs of legs (one year. Temperature plays a key role inwww.attra.ncat.org ATTRA Page 3
  4. 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 moreU 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 symphylansymphylan occurrence and movement is far from First instars emerge from the egg with sixoccurrence 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 infrom 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. 5. Pores, cracks, and holes in the soil allow symphylansto 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, seasonalclearly in this aerial view of a broccoli field. cracks and burrows made bysoil, garden symphylans often occur in other soil animals,very distinct aggregations. such as earthworms,Garden symphylans are unable to bur- to travel through therow through the soil. They use pores, soil profileseasonal cracks and burrows madeby 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 organicmatter, reduced tillage, raised beds) In the Pacific Northwest and Northernimprove the ability of garden sym- California, garden symphylans are com-phylans to move through the soil, lead- monly found in alluvial soils, and areing to increased populations and/or likely spread to some extent by flooding.increased damage through improved Relative soil acidity does not appear toaccess to roots. As a result, high pop- be closely correlated with garden sym-ulations of garden symphylans are phylan occurrence, since symphylansmore commonly found in fine-textured, are found in very acid soils (e.g., whereheavier soils with moderate or better blueberries grow) to fairly alkaline soilsstructure and many macropores, rather (e.g., pH 8+).than in sandy soils (Edwards, 1958;Edwards, 1961). When garden sym- Hot spots within infested fields oftenphylans are found in sandier soils, these remain consistent from year to yearsoils have commonly been amended with with little change in populations andorganic matter. only minor lateral spread, possibly duewww.attra.ncat.org ATTRA Page 5
  6. 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 andG 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 profileaggregate 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 alsotop six inches of tion of sampling efforts and for selecting be influenced by other variables thatsoil when the soil management tactics. impede movement, such as tillage andis moist and warm, compaction from tractor tires. Garden symphylans tend to aggregate inand move to deeper the top six inches of soil when the soilsoil strata when the is moist and warm, and move to deeper Samplingsoil becomes very soil strata when soil becomes very dry or cool. In Oregon, Washington, and Cali- Sampling for garden symphylans isdry 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. 7. tion, it is best to take sample units in agrid pattern. Sorting and comparing thesamples 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 onlythe density of symphylans in the surfacesoil; therefore, sampling should only beconducted when garden symphylans are Soil sampling in corn is carried out by placing soilin the surface soil. The best sampling on a black tarp and then carefully searching for garden symphylans.conditions are generally warm, moistsoil. Sampling within three weeks after When soil samples are taken, the soilmajor tillage—such as discing, plowing, from each sample unit is usually placedor spading—is often inaccurate, since on a piece of dark plastic or cloth, wheregarden symphylans may not have had T the aggregates are broken apart and theample time to re-establish in the surface garden symphylans are counted (Berry he bestsoil. If sampling is conducted soon after and Robinson, 1974). samplingtillage, soil sampling methods should be Sampling must be conducted through- conditionsused. Sampling should be conducted toa 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 rarelySoil Sampling done, because of the extensive time andSoil sampling is the standard/historic resources required. Therefore, sam-method for estimating how many garden pling is usually conducted when gardensymphylans are present in a field (i.e., symphylans are believed to be in the topapproximate 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 beson, 1974). Sample unit sizes vary. The sampled, but deeper sampling (e.g., tomost common soil sample units have a depth of 12 inches) is generally morebeen 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 soilUsing a cut potato as bait to check for the presence of garden symphylans.www.attra.ncat.org ATTRA Page 7
  8. 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 usedB 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 toto 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 methodshas 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 arewell 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. 9. Spinach seedlings show susceptibility to symphylan Corn seedlings show little susceptibility to symphylandamage. The soil in the pot on the left contains 45 damage. Soil in the pot on the left has no symphylanssymphylans. Soil in the pot on the right has no in it. The soil in the pot on the right contains 45symphylans 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). Theterns (Umble and Fisher, 2003a). For higher density of 45 garden symphylansexample, healthy plants sometimes indi- per pot has been shown to reduce thecate low garden symphylan populations growth of tomatoes and spinach seed-and conversely, unhealthy plants some- lings by more than 90%. Ftimes indicate high garden symphylanpopulations. In the field, noticeable damage often or manage- occurs if garden symphylans exceed an mentIndirect measures such as this may pro- average of 5 to 10 per shovelful in mod- purposesvide valuable information about the erately to highly susceptible crops such it is important toextent 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; Umblesampling. 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 tacticsdate, tillage intensity, chemical use, and to three garden symphylans per squarecrop species). foot is commonly used as a treatment that reduce damage threshold. to crops but may notAction Thresholds: Because of the considerable variability necessarily decreaseInterpretation of of symphylan densities within a field, populations. sample unit counts may range from 0 toSampling Results more than 100. These results are helpfulManagement decisions, such as those in locating field hot spots. In more toler-regarding pesticide applications and the ant crops, such as potatoes, beans, andintensity of tillage, are sometimes based small grains, garden symphylan feedingon pre-planting density estimates of gar- may not lead to significant damage, evenden 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 forindividual crops are not well developed. Management andThe relationship between garden sym-phylan population densities (estimated Control Many factors influence garden sym-by sampling methods) and measures phylan population levels (Howitt andsuch 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, informationIn the laboratory, levels as low as 5 to about the true effects of many factors15 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. 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 generallyP 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 significantlyin potato crops, field. Generally, symphylan populations Pesticides are thought to be home-grown and to Hundreds of compounds have been usedeven allowing develop over time due to favorable soilsubsequent against garden symphylans in the past management practices. 100 years, with varying efficacies (How-cultivation ofsusceptible crops in itt and Bullock, 1955). Fumigants androtation 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 ofPage 10 ATTRA Symphylans: Soil Pest Management Options
  11. 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. 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 AmendmentsM 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 betweenlevel 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 feedingphylan feeding dur- applications are generally believed to seems due to increased vigor and/oring 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. 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 symphylanseven under high populations. Perennial feeding on each plant in a local regioncrops, such as strawberries, raspber- (e.g., raised bed) is partially a factorries, hops, and bare root trees (nursery of the number of plants present in that Gproduction), can also be damaged, par- bed. In some cases, increasing plantticularly 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- phylanssymphylans than others (Simigrai and duction. Modifications of this strategy do not cross the soilBerry, 1974). include planting an early “distraction” surface for or “dilution” crop in a bed or adjacent significantCrop Stage to a cropping row. distances, as doWithin a crop, susceptibility is often ground beetles.related to the developmental stage of A good dilution crop is a low-cost, vig- However, they arethe 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 andsusceptible than 4-week-old transplants, increases the roots in the soil and effec- surprisingly mobilewhich 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 verticallyor increasing transplant size to reduce The dilution crop is then removed as the and horizontallydamage is not effective for all crops. target crop establishes.Transplants of broccoli and eggplant, through thefor example, often fail to establish under soil profile. Tactics to Reduce Access ofhigh garden symphylan populations. Garden Symphylans toPlant Density Crop Roots Since garden symphylans are not able toGarden symphylans do not cross the burrow through soil, instead relying onsoil surface for significant distances, soil pores and channels made by rootsas do ground beetles. However, they and other soil organisms, their accessare quite active and surprisingly to roots is strongly correlated with soilmobile for their size, moving vertically structure, bulk density (“fluffiness”) ofand 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 gardeninto a stale seedbed with seemingly few symphylans in the surface soil beforegarden symphylans have garden sym- planting, thus allowing crops to estab-phylans crawling all over their roots lish while garden symphylan numbersless than one day after planting. are low.www.attra.ncat.org ATTRA Page 13
  14. 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. 15. Garden Symphylan Filinger, G. A. 1928. Observations on the habits and control of the garden centipede, ScutigerellaReferences 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. Ohioogy. 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. InfectionPergamasus 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 toState 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 soilinhabiting 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. Controltions 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 toApplicata 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 coronataEdwards, 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 statusIn 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. HilgardiaZoology. Butterworths, London. 11: 55-148.Eltoum, E. M. A., and R. E. Berry. 1985. Influ- Michelbacher, A. E. 1939. Seasonal variation in theence 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. 16. Peachey, E., A. Moldenke, R. D. William, R. Berry, Umble, J. R., and J. R. Fisher. 2003a. Influence ofE. 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. SamplingRiley, H. K. 1929. The greenhouse centipede. Indi- considerations for garden symphylans, Scutigerellaana 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 UnitedStates 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 ofphylan 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 themol. 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-136nematode. 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 21506Page 16 ATTRA