Phytosanitary Measures for Seeds - nappo

Phytosanitary Measures for
Seeds
Field Inspections
Seed Testing
Seed Treatments

Seed Industry Perspective on
Phytosanitary
• Presence of any pest reduces seed quality
• Seed Companies have designed and
implemented QM programs to reduce
exposure to, and eliminate seed pests
throughout production life cycle
• ASTA Guide to Seed Quality Management
Practices
• Federal Seed Act
• OECD Seed Schemes

Seed Industry Perspective on
Phytosanitary
• The seed industry employs the same
methods as the NPPOs require to
manage, monitor, and ensure seed quality
• Phytosanitary field inspections
• Seed testing for pests
• Seed treatments
• Front line method for industry:
phytosanitary field inspection

Phytosanitary Field
Inspections
• Companies conduct their own
inspections for many pests
Monitor pathogen races
e.g: Exserohilum turcicum

Agricultural Industry:
Pests Data Collection
Phytosanitary Field Inspections
To document the
absence of a quarantine
pest is just as important
as recording their
presence.
Several ASTA member companies are
accredited for Phytosanitary Field Inspection
under USDA-APHIS-PPQ-National Seed Health
System

Phytosanitary Field Inspections
(NSHS)
• Establish the seed field inspection pattern
• 1. The seed field inspection pattern should
ensure that all parts of the field are adequately
and proportionately represented in the plants
inspected within the various usual microclimates
of the field.
• 2. As long as these requirements are met, the
pattern of field inspection can vary.

Phytosanitary Field Inspections
(NSHS)
• Stagger “X” pattern: used for cereal
crops
• Equidistant passes pattern: used for
crops other than cereals
• Design for field inspections: determine the
minimum number of field passes in
relation to field size to give a minimum of
95% confidence level in detecting an
infection level of 0.1%.

Table 1. Minimum field passes per acre.
Field size (acres) Minimum # passes
0 - 1 6
1 - 5 9
5 - 10 11
10 - 20 13
20 - 50 17
50 - 100 20
100 - 200 24
200 - 500 30
500 – 1000 36
1000 + 42

Advantages of Field
Inspections
• Allows a large number of plants to be
inspected (one plant can represent
thousands of seeds)
• Plants exhibiting symptoms are tested to
confirm
• Infected plants/fields are removed;
potentially infected seeds don’t enter
channels of trade

Advantages of Field Inspection
• Identification of special areas or microclimates
in the field that appear different
enough to warrant special attention when
inspected. These would include:
• Rivers and streams
• Drainage areas
• Low spots
• Weedy areas

Advantages of Field Inspection
• Areas of the field affected by borders,
such as:
• Field edges
• Tree lines in the field
• Adjacent fields of a similar crop
• Presence of buildings or bins

Advantages of Field Inspection
• Drought stress areas, such as:
• High spots
• Light textured soils
• Margins or overhead irrigation areas

Phytosanitary Seed Testing
• Should only be used for pests/pathogens
for which seed is known to be a pathway
• Often used when a phytosanitary field
inspection was not conducted (some
NPPOs require field inspection plus a
seed test)
• Often used to monitor/verify effectiveness
of an import program

Phytosanitary Seed Testing
Issues
• Use of “official” methods: system works
best when NPPOs of both exporting and
importing countries use the same method
• Problems occur when different test
methods are used for the same
pest/pathogen
• Problems can occur when regulatory
decisions are based on protein or DNA
based methods

Phytosanitary Seed testing
Issues
• Accuracy based on accuracy of the seed sample: is the
sample representative of the seed lot
• Need to use official seed sampling methods; e.g.,
AOSCA
• Accuracy based on sensitivity of method
• Protein and DNA based PCR tests assume correct
primers are used
• Primers often react to other strains or even species of
pest/pathogen, producing false positives

Phytosanitary Seed Testing
Issues
• Protein and DNA based methods do not
necessarily mean the pest/pathogen is
viable!
• Biological test methods (blotter tests, agar
assays, etc.) provide the most definitive
results, but can be time consuming
• Viruses: usually show symptoms (field
inspection), but require protein or DNA
based test methods

Seed Treatments
• Many countries accept seed treatments for
mitigating pests of phytosanitary concern
• Often when field inspections were not
performed for the pest of concern (e.g. reexport)
• Sometimes can be performed at port of entry
• Sometimes issues with registrations and
dosages of the active ingredient

Seed Treatments
• Emerging technologies offer promise
• Good opportunities for harmonization
among countries
• Issues with organic seed

Summary
• Phytosanitary field inspections offer significant
protection against seed pests by preventing
pests from getting into channels of trade
• Seed tests for phytosanitary purposes work best
when NPPOs use the same methods
• Both seed testing and treatments are viable
substitutes for field inspection when field
inspection is not possible.

Thank You!
rdunkle@amseed.org