Fees and Description of Assays

Standard Soil Assay

We use a 2-step assay that recovers all plant parasitic nematodes free in the soil and some nematodes that live inside plant roots.  Living and dead nematodes are filtered from soil in one assay.  In a second assay, pieces of roots present in the soil sample are incubated so that living nematodes exit roots.  Counts from the two assays are summed to estimate of the number of nematodes per 100 cm³ soil.  This two-step procedure is sensitive and accounts for root lesion and lance nematodes inside dead root fragments of the previous crop, nematodes infecting living roots, and those free in the soil.  Expressing nematode counts on a soil volume basis makes it easy to compare results for samples collected from the same field at different times.

Plants submitted with soil samples are inspected for nematode damage and are useful for the general diagnosis, but are not assayed because the root fragments in the soil sample represent many plants and therefore provide a more accurate census of nematodes than individual plant specimens.

Crop Root Incubation Assay

We offer a crop root incubation assay on request for root lesion and lance nematodes.  This method reveals how many nematodes are inside roots of the current crop so it is appropriate for evaluating products that offer protection against early season infection.  One to three plant root systems are incubated so that living nematodes exit roots.  This test should be conducted early in the season as most products applied with the seed or at-planting offer protection for 30-45 days after emergence.  Nematode counts are expressed on a per dry root weight basis.

Cyst Nematode Egg Assay

Unlike other plant parasitic nematodes, eggs of the cyst nematodes remain sheltered by the dead body of the mother (cyst).  We filter cysts from soil and count the eggs inside to estimate the size of the nematode population.  The test can be conducted any time during the year.  Counts are expressed as eggs per 100 cm3 soil.  This assay does not recover any nematodes except cyst nematodes.  Species identification is available for a separate fee by request, but most submitters find that cropping history is the best indicator of cyst species, particularly for the soybean cyst nematode.