TYPES OF DIAGNOSTIC LABORATORIES

Three types of diagnostic laboratories are found in California:

1. Cooperative Extension Specialists typically process several hundred samples each year for Farm Advisors to assist with diagnosing grower problems.
2. Nematologists with the California Department of Food and Agriculture (CDFA) Division of Plant Industry process thousands of samples each year submitted by County Agricultural Commissioner offices from imported plants, and for certification of garlic, strawberries, fruits, nuts and vines destined for farm plantings.
3. There are approximately 10 private diagnostic samples in the state processing samples for growers and PCA's.

Charges for running samples vary widely from lab to lab and are related to the amount of time required to process different types of samples:

• Depending on the services required, the time for processing and counting a single sample can be as little as one-half hour (typically for multiple research samples from the same field for which extensive species ID is not required).

• A typical diagnostic sample which requires identification only of plant parasitic nematodes to the genus level typically requires 45 minutes to an hour.

• Damage thresholds for cyst nematode require knowledge of the number of eggs present within cysts, a procedure which requires approximately 2 hours per sample.

• Samples which require species identification of root-knot nematode could require 4 hours or more.

There are also differences in the level of service provided by different laboratories:

• Extension Specialists and private laboratories typically report numbers of nematodes per volume or weight of soil or roots.
• CDFA samples typically specify which plant parasitic nematodes are present but not the number present.
• Some laboratories will provide assistance with determining the potential for the nematodes present to cause problems and other will not.
• Private laboratories typically provide a faster response than CDFA or Cooperative Extension laboratories.

Major limitations to practical nematode predictions include: (1) The lack of quantitative or qualitative published accounts or field experiences that draw correlations between actual numbers and field conditions which result in a quantifiable yield reduction. (2) A lack of standardization among soil sampling and extraction procedures.

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