Test Overview
Visual examinations are used to inspect seed for specified contaminants or organisms. They are commonly requested to meet import or phytosanitary requirements for exported seed, although they may be used for other testing purposes.
Depending on the target organisms, testing may include a Purity Visual, Purity Wash, or both.
Visual examination may also be used by the Seed Health Laboratory for certain pathogens that can be detected through direct examination.
Test Details
Visual examination for a small number of fungi such as ergot where sclerotia are mixed with grass seeds
Purity Visual
A Purity Visual, sometimes referred to as a bulk examination, is a direct examination of dry seed for specified weed seeds, insects, or other contaminants.
Purity Visuals are commonly requested when an importing country requires a shipment to be examined for specific organisms before export. The examination is based on the organisms specified by the importing country or import permit.
Customers should provide the import permit or other documentation identifying the organisms for which examination is required so the laboratory can determine the appropriate testing.
Purity Wash — Dust-Like Weed Seed Examination
A Purity Wash may be required when an import requirement includes very small or dust-like weed seeds that cannot be adequately detected through examination of the dry seed alone.
Seed is washed to separate very small seeds and particles from the larger crop seed. The recovered material is then examined for the specified weed seeds.
The Purity Wash is destructive to the portion of seed tested. Because a relatively large quantity of seed may be needed for the examination, customers with limited or high-value seed should contact Customer Care before submitting a sample.
A Purity Wash may be conducted in addition to a dry visual examination when required for export.
Seed Health Visual Examination
Direct visual examination may also be used for certain Seed Health tests when signs or structures of the target organism can be detected on or among the seed. For example, fungal structures such as ergot sclerotia may be identified through direct examination.
Sample Requirements
Sample requirements depend on the target organism and applicable import or testing requirements.
For export examinations involving weed seeds, up to 25,000 seeds may be requested to provide an adequate sample for examination.
When a Purity Wash is required, the portion of seed used for the wash cannot be returned or used for additional testing. Please submit additional seed when other tests are requested on the same sample.
When submitting seed for export testing, please provide the import permit or other documentation identifying the organisms for which examination is required.