Testing Services

PNW Plant Disease Image

Expert help is available to you at your local Plant Clinic.

Jay W. Pscheidt, 2010.

Plant Disease Clinics

Several plant disease clinics in the Pacific Northwest can help diagnose plant problems. Publicly supported clinics are listed below. A listing of other laboratories (mostly private) that provide a similar service can be found at: http://www.puyallup.wsu.edu/analyticallabs/services

For best service, for the most useful returns on your efforts, and for efficient use of our time, please read and observe these instructions before submitting specimens.

Collecting

  • Select material showing the symptoms you are concerned about. Send several samples showing various stages of disease, especially early symptoms. If possible, also send a healthy sample.
  • Get all parts of plants, including roots where practical. Enclose roots and soil in a plastic bag. Use another bag to enclose the rest of the plant.
  • If it is not practical to send the entire plant, include several affected portions of the plant. With stem or branch disorders, be sure the sample includes live material as well as the diseased portion. In other words, include the margin between healthy and diseased tissue.
  • If a vascular wilt such as Verticillium wilt or Dutch elm disease is suspected, send several branch sections 1 inch in diameter and about 6 inches long from branches with dying, wilted, or yellowed leaves. Do not send dead wood. Put samples in a plastic bag to prevent drying.
  • Turfgrass samples should be taken from the edges of affected areas that include dying and also apparently healthy plants. Send one or two 3-by-3-inch squares of sod containing 1 inch of attached soil. Wrap each sample in one thickness of slightly dampened toweling, then in dry newspaper. Send as much information as possible.
  • Fleshy specimens such as mushrooms, fruit, or potatoes should be as firm as possible and show early and intermediate symptom development. Wrap specimens separately in paper towels or newspaper. Do not put in plastic. Pack with sufficient padding to avoid crushing.

Packing

  • Keep plants cool and moist before shipping. Bag roots separately to keep soil from the rest of the plant, then enclose the entire plant in plastic to keep from drying out. Mail as soon as possible after collection. Mail specimens early in the week to avoid delay in the post office over weekends or holidays.
  • Pack in a sturdy container to prevent crushing in transit. Use packing material to pack the specimen firmly in the container.
  • Identify package with labels both outside and inside. Put the label and the Plant Disease Form in a waterproof plastic bag.

Addressing Packages

Oregon (from any location)

Plant Disease Clinic, Cordley Hall 1089, 2701 SW Campus Way, Oregon State University, Corvallis, OR 97331-2903 (Sample forms, fee information, directions to the Clinic, and other info about the OSU Plant Clinic is available at http://plant-clinic.bpp.oregonstate.edu/ )

Oregon (Northeast Oregon and North Central only)

Extension Plant Pathology Laboratory, 2121 S. First, OSU, Hermiston, OR 97838.

Idaho

Plant Samples, Kimberly Research and Extension Center, Kimberly, ID 83341

Plant Samples, Parma Research and Extension Center, University of Idaho, Parma, ID 83660

Western Washington

WSU Puyallup Plant Clinic, 2606 W. Pioneer, Puyallup, WA 98371-4998. (Fees required.)

British Columbia

Plant Diagnostic Laboratory, British Columbia Ministry of Agriculture, Fisheries, and Food, 1767 Angus Campbell Rd., Abbotsford, BC V3G 2M3 Canada (Fees required).

Information

Fill out the appropriate Plant Disease Form or Plant Disease Identification Request sheets with as much information as possible. These forms are available in your county Extension offices, the labs listed above and on the web at http://plant-clinic.bpp.oregonstate.edu/forms . This information is valuable as an aid to diagnosis. Some labs will not process samples unless a form has been filled out. Photographs or even video tapes convey a lot of information that may be useful. The more information you provide, the more accurate the diagnosis will be.

OSU Plant Clinic Fees

Services and fees

Insect/mite and other arthropod identifications are currently provided free of charge.

Disease Diagnosis Services

Plant disease diagnosis = $60.00 per sample (samples submitted via OSU county extension offices are $50.00 each).

This is our most frequently requested service. The service includes overall evaluation, including microscopic exam, results from a moist chamber, isolations onto artificial nutrient media, and identification of fungi or bacteria to genus. Measurement of soil pH and total soluble salts will be performed if necessary. Control recommendations are included.

Specialized Identification Services

Bacterial identifications

Identification of purified bacterial cultures = $30.00

This service identifies purified plant related bacterial cultures using Biolog. This method uses a microtitre plate filled with different carbon sources and identifies bacteria according to their metabolic profile; ID will be to species when possible.

Fungal or Bacterial ID via PCR (where available)

$60/pathogen

Viral identifications

Virus identification via serological assay (ELISA - enzyme-linked immunosorbent assay).

These fees are for those plant samples that are submitted specifically with a request to test for viruses. The cost of virus testing is based on the number of samples submitted and the number of viruses for which the samples are to be tested.

$40 for one sample/one virus

additional samples = $15.00 each

additional virus = $10.00 each

Virus testing done by an outside company = Cost of testing + postage

It is occasionally necessary to send a sample out to a third part for testing. The fees associated with doing so are dependent on the fees charged by the testing service. That fee is passed along to our client without any additional charge.

Seed assays

$75/seed sample (Kabatiella, Phoma, Ascochyta, Gloeotinia)

Water assays

Phytophthora or Pythium testing of water via filtration. Advance notice is required and samples can be accepted only Monday through Wednesday. $100/sample

Soil assays

Assaying field soil for the presence of Verticillium = $30.00/soil sample. This service analyzes the soil samples for propagules of the fungus Verticillium dahliae. We suggest a minimum of 5 samples per acre in order to get a reasonable representation of the field. This test takes a minimum of 4 weeks.

Rush samples

Plant samples to be done on a “rush” basis = $150.00 per sample ($100 if submitted through OSU extension).

This includes an extremely thorough investigation, with results available in most cases in 24 hours. This includes evaluation for fungal and other diseases; no additional fees are assessed for culturing or other methods needed to reach a diagnosis. This service is not available at all times. Please call to confirm it is available before submitting a sample.

Special assays and ID services = $150/ hour

Other services

Other services not listed here may be available. Call for information.

Out of state samples

ALL SAMPLES received from out-of-state will be assessed an additional 50% surcharge.

Factors used to set fees include cost of materials, supplies, clerical support, and a portion of the labor required to perform the tests. The remainder of the costs are paid by the OSU Extension Service as part of its education mission.

For more information, contact:

Melodie Putnam

Director

OSU Plant Disease Clinic

Cordley Hall, Room 1089

2701 SW Campus Way

Corvallis, OR 97331-2903

Tel. 541-737-3472

Fax 541-737-2412

putnamm@science.oregonstate.edu

Or

Maryna Serdani

OSU Plant Disease Clinic

Cordley Hall, Room 1089

2701 SW Campus Way

Corvallis, OR 97331-2903

Tel. 541-737-3472

Fax 541-737-2412

maryna.serdani@science.oregonstate.edu

OSU Central Analytical Laboratory

The Central Analytical Laboratory provides inorganic chemical analysis of soils, plants, and water. Routine procedures include standard soil testing methods, nutrient analysis of plant tissue, and inorganic water analysis.

For more information:

Oregon State University

109 Crop Science Building

Corvallis, OR 97331-3002

http://cropandsoil.oregonstate.edu/content/central-analytical-lab

Central.Analytical.Lab@oregonstate.edu

Tel. 541-737-2187

OSU–Hermiston Plant Pathology Laboratory Testing Services

General diagnosis = $60.00

This includes an overall sample examination, including a thorough microscopic exam, moist chamber incubation results, isolations onto multiple selective and non-selective nutrient media (as needed), and identification of fungi or bacteria to genus. When possible, viruses will also be identified. (Some viruses require extraordinary methods for identification, such as inoculation onto indicator hosts, and these procedures are not included in this fee.)

Soil pH and total soluble salts = $10.00

This is a new service. Soil submitted with a plant sample will automatically have these measurements taken, when requested, at no additional charge. This service is for soils submitted specifically for this analysis.

Ship samples to:

Jordan Eggers

Extension Plant Pathology Laboratory

2121 South First

Hermiston, OR 97838

Soil Fungus Assays

Fee Schedule per Soil Sample:

Pathogen

**Cost/sample 1-4 samples

**Cost/sample 5+ samples

Verticillium

$35

$33

Pythium

25

23

Fusarium

25

23

Phoma terrestris (Onion pink root)

30

28

Pythium, Fusarium spp., and Phoma terrestris

80

74

Pythium, Fusarium,

and Verticillium spp./ C. coccodes

85

79

** Prices listed are per soil sample. Please allow approximately 2-3 weeks for Pythium, Fusarium, and Phoma terrestris assays and 5 weeks for Verticillium/C. coccodes (black dot).

Metalaxyl-Resistant Pythium Soil and Culture Assay

The soil assay determines what percent of the total Pythium spp. present in the soil show resistance to metalaxyl. The culture assay determines if the Pythium spp. recovered from infected plant material is resistant to metalaxyl. The fee for these tests is $40.

Silver Scurf and Black Dot Testing of Potato Tubers

Silver Scurf and black dot tuber assays are conducted on seed and market tubers. The fee for this service is $50.00 per lot.

Virus Testing

ELISA Fee Schedule per Leaf Sample*

# of Samples

# of Viruses to be Tested

1-4

5-24

25+

1

$15

$10

$7

2

20

12

9

3

25

14

11

4

30

16

12

5

35

18

13

6

40

20

14

*Add $1 per sample to test tubers or plant parts other than leaves.

PCR Fee Schedule per Leaf Sample

# of Samples

# of Viruses to be Tested

1-4

5-24

1

$35

$30

2

40

34

3

45

38

4

50

42

5

55

44

6

60

48

Leaf samples are generally tested individually, but may be tested in bulk (up to 5 leaves) for more economical testing of large numbers of samples.  Please note: bulk testing is less able to detect low titers of virus.  Call for special pricing of very large sample lots and to learn which viruses can be detected by this method.

For further information, contact:

Jordan Eggers

Extension Plant Pathology Laboratory Manager

OSU HAREC

Extension Plant Pathology Laboratory

2121 S. First Street

Hermiston, OR 97838

Office 541-567-8321

Jordan.Eggers@oregonstate.edu

This fee schedule, sample submission form, and directions for sample submission can be found at: http://oregonstate.edu/dept/hermiston/plant-pathology-plant-lab-testing

Fees subject to change, see website for current price list.

Samples must be accompanied by a completed sample submission form. Sample processing may be delayed if a sample submission form is not included with shipped samples.

Digital pictures can be E-mailed to:

Jordan.Eggers@oregonstate.edu

Note: Failure to recover or confirm an organism from a sample does not establish the field to be free of that organism.

Oregon Department of Agriculture Plant Health Laboratory

The Plant Health Section provides official phytosanitary field inspections and laboratory testing for Oregon’s seed and nursery industries. This testing is required for shipment of products to international and other markets and includes such programs as the Allium white rot certification and seed testing programs. Official inspectors collect all samples for these testing programs and perform the field inspections. The laboratory also provides a general diagnostic service for the nursery industry, other government agencies, licensed landscapers, and others.

The following fees and charges are established for laboratory or other testing services including sample processing, analysis, and issuance of certificates or official reports. The basic fee for official, regulatory, and service samples is established at $70/hr, with a minimum fee of $35. The fees for specific routine tests are as follows:

  • Spore wash and microscopic exam per fungal species - $50
  • Fifty-seed stain and immunoblot for endophyte - $85
  • Seed, soil, or tissue test for nematodes - $35
  • Visual exam for regulated pests - $60 for pesticide treated seed and $50 for untreated seed
  • Visual exam for regulated contaminants - $45
  • Visual exam for regulated pests and contaminants - $70
  • Isolation on standard media - $35
  • Growing media pH and conductivity - $35
  • Seed grow out for bacteria - $140
  • ELISA for virus detection in seed $140
  • Molecular analysis for regulated pests - $140

Staff members provide field inspection services for official phytosanitary certification to meet the quarantine requirements of Oregon’s international and other customers. Services provided include the inspection of seed fields for seed-borne diseases, mint for Verticillium wilt, potato for late blight, and Allium for white rot.

The fee associated the seed field inspection service has been established at $6.50 per acre for each field with a minimum fee of $50 for each field inspected and a maximum fee of $450 per field.

The fee for processing applications for field inspection shall be $3 per application, including applications for inspecting bean seed fields for certification for replanting in Malheur County. Bean seed fields inspected for certification for replanting in Malheur County are inspected at a rate of $3.50 per acre per inspection with a minimum charge of $30 per field.

For fees associated with the other field inspection services, please call the Department at 503-986-4620. You may call that number for general information about the official inspection and testing and seed sampling services provided by the Department. Information is also available online at:

WSU Plant & Insect Diagnostic Laboratories

Western Washington

The WSU Puyallup Plant & Insect Diagnostic Laboratory provides diagnostic assistance to citizens and businesses of western WA and supports the work of WSU Extension.

Plant Problem Diagnosis

In person: The Plant Clinic is open Monday through Friday from 8:00 am to 4:30 pm.

Or

Mail packages to:

WSU Puyallup Plant Clinic

2606 W. Pioneer

Puyallup, WA 98371-4998

Please DO NOT mail on a Friday or before any national holiday because the specimens may deteriorate in transit or over the weekend.

Diagnostic base fees start at $25.

Note: Special tests may incur additional fees.

We accept payment by cash or check only. Please make checks payable to “WSU Puyallup Plant Clinic.”

For further information on submitting samples from western Washington, please refer to our web site at

http://www.puyallup.wsu.edu/plantclinic

or contact:

Jenny Rebecca Glass

Plant Diagnostician

2606 W. Pioneer

Puyallup WA 98371-4998

Tel. 253-445-4582

Fax 253-445-4569

jennyglass@wsu.edu

Eastern Washington

The Department of Plant Pathology at WSU in Pullman supports a Plant Disease Diagnostic Lab. For information on sample submission and fees, please contact:

Karen F. Ward

Plant Disease Diagnostician

Dept. of Plant Pathology

P.O. Box 646430

Pullman, WA 99164-6430.

Tel. 509-335-3292.

Fax 509-335-9581

karen_flint.ward@wsu.edu

Please contact the diagnostician before submitting samples.

The Spokane County Master Gardener Education Center supports the diagnostic work of Master Gardeners volunteering in eastern Washington.

For more information, please refer to the web site at

http://www.spokane-county.wsu.edu/spokane/eastside

or contact:

222 N Havana

Spokane WA 99202-4799

Tel. 509-477-2048

Testing for Endophytes

OSU Seed Laboratory

http://seedlab.oregonstate.edu/

Contact:

Adriel Garay, Manager

Corvallis, OR 97331-3801

Tel. 541-737-4464

Fax 541-737-2126

Seedlab@oregonstate.edu

The laboratory operates on its fee income. As costs rise for supplies, equipment, and personnel, it is necessary from time to time to adjust the fee schedule.

  • Pest and Disease (dry seed inspection) $58
  • Endophyte test (chemical/immunoblot assay) $110 for seed, $200 for tillers.
  • Broom-rape (Orobanche minor) in Red Clover $95

Endophyte Service Lab

We test feed materials for ergovaline, lolitrem B, and ergot alkaloids. For some test types, rush processing is available. Clinical clients can submit samples by express mail or FedEx. Clinical clients should contact the laboratory by phone or email and we will advise in proper sample collection and submission.

The cost is $50 U.S. Funds/sample/assay.

Checks should be made payable to: Oregon State University

Clients may choose to be billed rather than to send payment with sample.

Sampling Tall Fescue and Perennial Ryegrass for Endophyte Toxin Analysis

Concern about endophyte-infected tall fescue and perennial ryegrass seed straw has generated repeated questions about samples of straw for endophyte testing. Straw samples are analyzed for toxin content, not for endophyte presence. These chemical analyses are only as good as the straw sample provided. In other words, a toxin test will accurately represent a lot of straw only if the sample is truly representative. The following the guidelines will ensure that samples are as representative as possible.

Use a Core Sampler Commercial forage samplers are available through farm supply sources. Your county Extension agent can help you locate a supplier. Attach a core sampler to a brace or half-inch drill for easy sampling. Ideally, the sampler should have an exterior diameter of 0.5-inch and a sample length of at least 12 inches. Minor deviations from these measurements are acceptable.

Sample a bale by centering the core sampler in the end of the bale and drilling horizontally. Take at least 20 cores (one per bale) for each lot of hay.

A lot of straw should represent straw from one variety, harvested from the same field. If two lots of straw are in a stack, sample them separately. A truckload of straw may be considered a lot if there is no information to the contrary.

Sample at Random Bales within a lot of straw should be sampled at random. “Random” means that you have no precise reason for selecting or rejecting a specific bale to sample. Here are two ways to guard against biasing. First, sample every fourth or fifth bale, going around the stack (or truck) or driving down the row in the field. Or, take at least five random samples from each of the four sides of the stack.

Mailing Place the entire sample in a polyethylene freezer bag and seal it tightly. Be sure to label the sample with your name, telephone number, sample identification, and the type of assay you want the lab to perform. Either write this information directly on the bag using a permanent marker pen, or write it on a piece of paper (a business card is ideal) and enclose the paper with the sample. Commercial clients should use the website to generate appropriate labels for their samples.

To take a pasture sample, randomly select 20 separate sites within the pasture. At each site clip a handful of grass just above the ground. If your animal typically pulls the plant up by the roots and eats the entire plant, you may wish to pull up a handful of plants at each site. Otherwise, clipping plants at ground level will be sufficient. It is best to air dry your sample out of direct sun light before shipping. If your sample is not dry, it is not acceptable for testing and should not be submitted.

Proper samples should be submitted to the following address:

139 Oak Creek Building

Endophyte Service Laboratory

College of Agricultural Sciences

Oregon State University

Corvallis, OR 97331

The laboratory phone number is (541)737-2872 if you have any questions.

Virus Testing and Therapy

The following testing and therapy services are available from the National Clean Plant Network for Fruit Trees (NCPN-FT),Washington State University, 24106 N. Bunn Road, Prosser, WA 99350. Further information on this program and related issues can be viewed on the Internet at http://ncpn-ft.org/

Test protocols for virus and virus-like agents that affect tree fruit cultivars are:

  • Woody indicator tests in the greenhouse or field.
  • Herbaceous indicator tests in the greenhouse.
  • Polymerase chain reaction (PCR) tests for phytoplasma.
  • cRNA hybridization for selected viroids.

NCPN-FT also provides virus therapy for infected deciduous tree fruit cultivars of commercial importance.

Additional virus testing is provided by the WSU ELISA Testing Laboratory where a range virus assays are conducted using enzyme-linked immunosorbent assay (ELISA). Testing by this lab is available for the following viruses.

  • Alfalfa: alfalfa mosaic virus
  • Apple trees: apple chlorotic leafspot virus, apple mosaic virus, tomato ringspot virus
  • Asparagus: asparagus virus 1, asparagus virus 2, tobacco streak virus
  • Beans: alfalfa mosaic virus, bean common mosaic virus, bean common necrosis virus, beet curly top virus, cucumber mosaic virus, peanut stunt virus, tobacco ringspot virus, tobacco streak virus, tomato ringspot virus
  • Cereals: barley yellow dwarf virus
  • Corn: high plains disease virus
  • Hop: apple mosaic virus
  • Stone fruit trees: apple mosaic virus, cherry leafroll virus, prune dwarf virus, Prunus necrotic ringspot virus, tomato ringspot virus
  • Peas: pea enation mosaic virus, pea leafroll virus, pea seed-borne mosaic virus
  • Roses: apple mosaic virus, Prunus necrotic ringspot virus, tobacco streak virus
  • Small fruits and berries: tobacco streak virus, tomato ringspot virus
  • Vegetables: cucumber mosaic virus, squash mosaic virus, tobacco ringspot virus

Information on serological testing is available at http://www.prosser.wsu.edu/faculty/Elisa-rev.htm

Nematode Testing

The OSU Extension Plant Pathology and the University of Idaho perform nematode tests. A fee is levied for each sample of soil or roots tested. More information and sample submission forms and instructions are available on the “Nematodes in Oregon” web site: http://www.science.oregonstate.edu/bpp/Nematodes

Fees for the OSU Nematode Testing Service:

  • Soil sample: extract and count plant parasites by genus: $40
  • Root sample: extract and count plant parasites by genus: $40
  • Species identification: $20 per genus per sample for routine species; $57/hour for others

Routine species include species of plant pathogenic genera commonly encountered in the Pacific NW quadrant of the United States. Pratylenchus penetrans, P. neglectus, P. crenatus, and P. thornei; Meloidogyne hapla, M. chitwoodi, and M. naasi; Paratrichodorus allius and Xiphinema americanum.

  • Inappropriate submissions as explained in instructions on the submission form in print and on the web: minimum of $10 per sample.
  • Other services include foliar nematode extraction and ID, cyst extraction and ID, root-knot egg extraction, and seed gall nematode extraction: phone 541-737-5253 for information and costs. Note: Fee changes may occur July 1 so confirm fee structure before submissions after July 1.

Information about plant-parasitic nematodes in soils and crops is increasingly important to Pacific Northwest growers for maintaining and improving crop production. Nematode detection is a standard laboratory procedure, although special facilities and personnel are required. Most nematodes in soils and plant tissues can be accurately recovered and enumerated. However, the weakness in the system is the method of sampling. Unfortunately, no one knows how to sample a field in a way that accurately represents nematode population distributions. Despite this problem, results from soil or plant samples will aid growers in planning their crop production programs. Decisions about soil fumigation and future cropping programs depend on knowing the kind and amount of plant-parasitic nematodes present.

The OSU Nematode Testing Service processes samples to help growers make decisions about crops, not to address regulations governing inter- and intrastate shipments. Contact the state Department of Agriculture for such testing.

Sample Contents

Soil A composite sample of approximately 1 pint of soil is best for an accurate routine test to diagnose a plant problem or confirm nematode populations; 2 quarts are required for a bioassay but do not send this much soil without prior authorization. A soil tube 0.875 inches by 12 inches is the best sampling device, but trowels or shovels may also be used. Take the composite sample from at least 20 locations within no more than 5 acres. If sampling poor areas or weak spots, sample from the edge rather than from the middle.

If plants of the crop in question are available, roots and surrounding soil may be included in the sample. When diagnosing a plant problem, soil samples from both the healthy and diseased part of the field will aid in interpreting the final results.

Plants It is best to take a composite sample (10 or more root subsamples within the 5-acre area) for an accurate routine test for root-dwelling nematodes. The sampler is responsible for ensuring that the roots in the sample bag belong to the species or cultivar named on the label. If the sampling area does not contain plants of the injured crop, it is possible to include an alternate host plant, such as clover or vetch for root-lesion nematodes.

Information Please fill out a Nematode Test Form which is available from your county Extension office. Unlabeled samples have no value. The label should state: date, grower’s name and address, location of sampling area, name and cultivar of crop last grown, and name and cultivar of crop to be planted. Do not let the label or form come into contact with the sample.

Packing Standard soil test bags or polyethylene bags are satisfactory containers for samples; they maintain soil moisture. Avoid exposing samples to heat, such as direct sunlight or the inside of a hot vehicle. Because some nematode extractions rely on living, active nematodes, heat and drying must be avoided or results will be compromised. Do not use paper bags, glass jars, cardboard boxes, sandwich bags, grocery store plastic bags, bread bags, or other thin plastic bags. Attach a label or Nematode Test Form to the outside of the sample bag.

Address to either:

Idaho

SW Idaho R/E Center

29603 U of I Lane

Parma, ID 83660-9637

Oregon

Nematode Testing Service

Department of Botany and Plant Pathology

Oregon State University

2082 Cordley Hall

Corvallis, OR 97331-2903

Interpreting Nematode Test Reports

Nematode test reports must be interpreted properly before a management decision can be made. Most laboratories use different forms to report results, but all contain essentially the same information. When interpreting the information on these forms, consider units of nematode density, extraction method, nematode species, time of year, and damage thresholds.

Units of Nematode Density Different laboratories report nematode densities on different bases. In addition, damage-threshold levels are reported in a variety of different units. If you send samples to only one laboratory, interpreting its report of density units is less of a problem. Be aware of the type of density-units expression your laboratory uses to report results. If necessary, ask your lab to explain its system of expressing density units to you.

Nematode densities (or counts) may be expressed on the basis of weight (for example, number of nematodes per gram of soil) or volume (such as number of nematodes per cubic centimeter or pint of soil). Counts also may be expressed on the basis of wet or dry soil. Generally, counts based on weight are more consistent than those based on volume. If an adjustment is not made for the amount of water in the soil, however, counts based on weight can be variable. Nematode counts from roots or other plant material are usually expressed by weight of soil but may be based on either fresh or dry weight depending on the lab processing the samples.

Understanding density units is critical in making treatment decisions. For example, a field may need treatment when there are more than 100 root-lesion nematodes per 500 grams of soil. If the laboratory reports the density as 50 root-lesion nematodes per 100 grams soil, one might conclude that the field does not need treatment. However, this density converts to 250 nematodes per 500 grams of soil, which indicates a different treatment decision.

Extraction Efficiency Several methods can be used to extract nematodes from soil and plant tissue. Each method produces different nematode counts based on the number of live nematodes, duration of extraction, soil type, and nematode species present. Problems can occur when different laboratories’ results are compared with one another or with thresholds reported in the literature. Again, if you send samples to only one laboratory, interpreting extraction methods is less of a problem.

Baermann funnel extraction requires several days and recovers only live nematodes. Extractions using density centrifugation are faster and yield both living and dead nematodes. The number of nematodes extracted from roots after only 1 day will be about 10% of the number recovered if roots are extracted for 1 week. Extraction efficiency is higher for lighter soils than for heavy soils.

Some nematode species are more efficiently extracted by a particular method. For example, ring nematodes are best recovered by density centrifugation and may be underestimated if Baermann funnel techniques are used.

Nematode Species Almost all laboratories provide the common and/or generic name of all plant-parasitic nematodes recovered from a sample. However, different nematode species within a given genus may damage a crop differently. Species identification may therefore be important, but it is more difficult than routine nematode tests and may require an extra fee. In mint, for example, pin nematodes can be very damaging, but there are no data to show that different species produce different levels of damage. Therefore, knowing the species of a particular pin nematode in a mint field is not important. On the other hand, barley root-knot (Meloidogyne naasi), Columbia root-knot (M. chitwoodi), and northern root-knot (M. hapla) may be found on crops grown in rotation with mint. Any of these nematodes may be in a sample taken before mint is planted; however, only northern root-knot nematode will damage mint.

Time of Year for Sampling Population densities of nematodes go through cycles during the year. A count of five nematodes per 100 grams of soil at the low part of a nematode’s population cycle represents a greater threat than the same count at the peak of the population cycle. If soil samples for a particular nematode species are always taken at the same time of the year, interpreting the results is much easier.

Damage Level Information. Ultimately, the number of nematodes in a soil sample taken at a certain time relates to the damage the nematodes may cause the crop. Some quantitative damage figures for nematode–crop interactions in the Pacific Northwest are available but have been difficult to find. The OSU Nematode Testing Service is the process of compiling damage figures for Pacific Northwest crops. Five text documents listing host range and damage levels by plant and nematode species within crop groups are available on the Nematodes in Oregon Agriculture web site, http://www.science.oregonstate.edu/bpp/Nematodes , and may be searched using your web browser’s “Find a File” function. Hard copies of some text documents are also available from:

OSU Nematode Testing Service

Department of Botany and Plant Pathology

Oregon State University

2082 Cordley Hall

Corvallis, OR 97331-2903

Tel. 541-737-5253

The experience of local growers, crop consultants, and Extension agents also is valuable in making management decisions. In general, a healthy crop can withstand higher nematode densities than crops stressed by factors such as a lack of water or nutrients or the activity of other pests. Damage usually is greater on sandy soils.