National Plant Board

Plant Quarantine, Nursery Inspection, and Certification Guidelines

Appendix K

National Plant Board Standard for Phytosanitary Certification


A. Purpose

The purpose of this standard is to help ensure that phytosanitary certificates issued by regulatory officials in the United States to affirm, declare, or verify that shipments of quarantined commodities comply with duly established foreign, federal, or state quarantine requirements are both valid and reliable. To this end, information will be provided that will foster a clear understanding of what phytosanitary certification is, why it is important, and what contributes to validity and reliability.

B. Role

This standard can be used by program administrators as a tool for education and control. Administrators are encouraged to make it their agency’s policy to meet this standard. Educationally, this standard can be used to train the agency’s phytosanitary certification staff and to help interested and affected industry representatives to understand and appreciate the need for phytosanitary certification as well as the expectations that the agency must meet in performing its phytosanitary certification duties.


1. “Area” means any political division or subdivision or any officially defined area including adjacent parts of contiguous political divisions or subdivisions. [Political divisions include nations and states or provinces within them. Political subdivisions include counties, parishes or municipios (in Mexico), and cities or municipalities. Officially defined areas also may include any other clearly defined and identifiable area including a specific property or facility].

2. “Economic impacts” means significant damage or harm in terms of well documented: a) plant or crop destruction or injury; b) increased cultural or pest control costs; c) disruption of existing pest control strategies such as biological control, integrated pest management, sustainable agriculture or forestry, and cropping patterns or loss of a high value crop without replacement by an equally valuable and marketable crop; d) social adversities such as interference with home/urban gardening, human health, worker safety, food safety, or jobs; or e) environmental quality including added pesticide use, scenic and watershed damage, destruction of ecosystems, and food chain interference.

3. “Endangered area” means continent, region, country, state, county, province, municipality or any other discretely delineated political or otherwise lawfully constituted geographic area which has been officially identified for protection from injurious pests not already present.

4. “Official” means authorized, implemented and directed, or performed by a governmental plant protection organization.

5. “Officially controlled” means the conduct, by an official public pest prevention agency, of eradication or intensive suppression activity including various treatments, quarantine, and other measures with the goal of eliminating an isolated infestation or prevention of further spread within an endangered area. (Note: It does not include private, general agricultural, urban forestry, or home garden pest control measures conducted by individuals against pests permanently established in an area.)

6. “Phytosanitary certification” means the act (by a duly authorized regulatory official) of affirming, declaring, or verifying compliance with any legally established quarantine requirement.

7. “Phytosanitary certificate” means a document authorized or prepared by a duly authorized federal or state official that affirms, declares, or verifies that an article, nursery stock, plant, product, shipment or any other officially regulated thing meets quarantine requirements.

8. “Phytosanitary measures” means any growing season or post-harvest treatment or any other method (tactic) or strategy (combination of methods or tactics) specified in a quarantine to reduce quarantine pest risk to an acceptable level.

9. “Quarantine” means a legal instrument duly imposed or enacted by a governmental agency as a means for mitigating pest risk.

10. “Quarantine pest” means an economically important pest that does not occur in an endangered area, or which is being officially controlled in an endangered area, and for which economic impact cannot be reduced to an acceptable level by means or methods other than phytosanitary measures.


A. Validity

The validity of phytosanitary certification derives from 1) compliance with or conformance to accepted premises and 2) findings supported by evidence.

The basic premise of phytosanitary certification is that it is performed by impartial third parties. Current phytosanitary certification systems only accept governmental agencies and their duly authorized employees as being impartial third parties for the collection of samples, performance of inspections and tests, supervision of treatments, determining compliance with quarantine requirements, and the issuance of phytosanitary certificates.

The issue of impartiality is critical because growers, packers, shippers, exporters and others involved in commercial transactions for economic or other reasons question why they are not allowed to perform certain work that is prerequisite to or which will serve as a basis for phytosanitary certification. Such industry entities must understand that officials of the importing country or state are the ones who make this determination. Agencies and their official representatives that issue phytosanitary certificates are obligated to conduct themselves in conformance with what has become accepted to achieve impartiality.

Findings supported by evidence is the second key factor in validity. This factor requires that treatments, inspections, tests, etc. are performed by properly trained officials and that documented results give evidence that specified quarantine requirements have been met.

B. Reliability

Reliability has to do with accuracy and consistency over time. When phytosanitary certification is consistently accurate under many different demands and circumstances for some indefinite period of time, importing counties and states become confident and phytosanitary certificates are highly trusted. Thus, reliability is closely akin to confidence and trust which must be earned.

Initially, the degree of confidence or trust is likely to be low unless the certifying agency or its representatives are highly respected for competence in some other field of regulatory activity. As in any matter of reputation, one serious violation of confidence or trust can destroy the reliability of a phytosanitary certification program.

C. Standard

All required sample collection, inspections and tests, supervision of treatments and determinations of compliance with import quarantine requirements must be performed by or under the direct supervision of duly authorized phytosanitary certification officials of governmental agencies AND the evidence obtained by the conduct of activities required by the importing country’s or state’s quarantine must clearly show compliance with quarantine requirements.


A. Field and Commodity Inspection

Phytosanitary certification sometimes calls for field inspection during the growing season or post-harvest commodity inspection. The validity and reliability of this pest risk mitigation measure depends primarily upon having adequate equipment, competent staff, and inspection of an adequate and representative sample of the field or lot.

Adequate equipment and a competent staff are presumed; but, importing countries or states may specify an inspection or sampling procedure, sample size and inspection procedure. If not, the certifying agency must use its own best professional judgment as to what procedures and sample sizes will be required to assure their certification will be valid.

B. Preclearance/Origin Inspection

Preclearance and origin programs differ from traditional phytosanitary measures enforced at ports of entry primarily in that the effort is to assure that pest risk is mitigated before the commodity leaves the exporting country or state. Effective preclearance programs have the advantage of reducing losses due to rejections at arrival points and speeding up delivery of products by eliminating holding and inspection and testing delays.

Phytosanitary certification is sometimes performed based on pre-shipment inspection by quarantine officials representing the pest prevention agency in the importing country or state. Alternatively, such pre-shipment inspection may be performed by phytosanitary certification officials of the exporting country or state who have been specifically authorized to act in this capacity by the importing country or state. In either case, it is typical for the costs to be borne by the exporting country. However, costs are the highest in the first instance. Consequently, preclearance utilizing quarantine officials of the importing country or state is discouraged.

Where the exporting country or state employs competent phytosanitary officials with a good record for credible phytosanitary certification, preclearance inspection made by exporting county officials is just as effective in mitigating pest risk as inspection performed by quarantine officials of the importing county or state. Furthermore, preclearance by officials of the importing country or state does not guarantee acceptance of the precleared commodity. Typically, shipments are held and inspected again at the port of arrival or terminal in the importing country or state and frequently rejected–potentially on an arbitrary basis.

Consequently, preclearance inspection by phytosanitary certification officials of the exporting country or state is encouraged, especially when it incorporates a phytosanitary certification procedure that eliminates holding and further inspections at the port of entry or other terminal inspection points.

Closely akin to preclearance programs are origin inspection programs. Whereas preclearance programs rely most heavily on commodity inspection, origin inspection programs typically incorporate a mix of cultural, testing, treatment, and inspection measures that are designed to mitigate pest risks that are too complex in nature to be addressed by inspection procedures alone. Origin inspection programs also provide for movement into the importing country with reduced or eliminated holding and inspection at ports of arrival. Thus, they too have the additional advantages of reducing losses and delivery delays.

C. Standard

The NPB Standard is that sampling plans and inspection should always be biased toward discovery. Random or grid sampling plans can be overlaid with the appropriate bias to achieve the desired level of confidence. Sampling plans must additionally consider the factors that influence:

the presence and distribution of the targeted pest(s). Inspectors must look in the right places and the right times consistent with the biology and habits of the quarantine pest(s).

detection of the pest [such as the selection of sampling sites, signs and symptoms, the accuracy or sensitivity of the technique(s) used, and the influence of cultural and pest management methods].

proper identification of samples.

proper protection of samples.

proper utilization of whatever tools may be appropriate such as seed triers, soil probes, knives, hand lenses, specimen vials, etc.

proper protection or preservation of pest specimens and performance of confirmatory diagnostics by professional staff.

adequate documentation of the results of sampling, inspection, and diagnostics.

As standard practice, states also should optimize the use of those preclearance and origin inspection strategies encouraged in this document.


Trapping is sometimes specified as a basis for phytosanitary certification. Many factors affect the validity of trapping as a basis for phytosanitary certification.

The NPB Standard is that:

The biology, life cycle and host range of a pest and its host(s) must always be taken into consideration. Other factors that must be considered include:

– level of confidence

– pest biology/life cycle

– pest host range

– pest colonization/establishment potential

– availability of lures and traps

– effectiveness and other factors associated with the lure

– capture effectiveness of the trap(s)

– trap density and placement

– trap servicing and relocation intervals

– trap durability

– training

– quality control

– availability of resources

Specimens collected must be properly removed from traps and protected during shipment or other handling.

Specimens should be identified by professional staff with expertise in diagnostics of the quarantine pest group.


A. Validity and Reliability of Laboratory Testing

At times an importing country or state will require that a sample of a commodity be taken and that it be analyzed in a laboratory using a prescribed test or test procedure as a basis for phytosanitary certification.

Typically, such testing is required for various kinds of plant materials and true seed to determine freedom from viruses, bacteria, and fungi that can cause specific diseases. An example of such a requirement is the performance of an Enzyme Linked Immunosorbent Assay (ELISA) for the seed borne lettuce mosaic virus. The generally accepted standard in terms of test results is zero infected seeds in a sample size of 30,000.

As in the case of other methods for determining compliance with quarantine requirements, many factors are involved. However, the fundamental and key factors are validity and reliability.

The validity question is related to the tests performed as well as to where the tests are performed. If an importing country or state specifies the sample size, sampling procedure and the diagnostic test procedure, sampling and testing should follow what is specified. Admittedly, some requirements are not scientifically justified and some prescribed tests may not have been subjected to standardization; but, these issues must be dealt with between the trading partners. It is not within the discretion of the phytosanitary certification official or diagnostics laboratory to change what is specified by the importing county.

On the other hand, if a sample size, sampling procedure and diagnostic test are not specified by the importing country or state, the phytosanitary certification official has some discretion; but, the goal should be to carry out sampling and testing in a scientific and professional manner. The reliability of the phytosanitary certification agency is also at issue. If the importing country’s or state’s requirements cannot be met by the phytosanitary certification agency, phytosanitary certificates must not be issued.

Where the diagnostic tests are performed is the second question of validity. Most state agencies operate diagnostic laboratories that provide timely and accurate professional technical support for their quarantine enforcement, pest detection, pest eradication, nursery inspection, and seed regulatory activities, as well as for the performance of tests for phytosanitary certification purposes. Some nurseries and seed companies operate testing facilities of their own. There also are private laboratories that perform diagnostics as a service for a fee.

The issue of impartiality has already been discussed in this document but it has special implications for laboratory testing. While governmental agency laboratory diagnostics are generally accepted as being impartial, the same is not true of private laboratories. However, at times a governmental agency’s laboratory may not be proficient in the performance of a specific test or the volume of testing may exceed the laboratory’s capacity to provide a timely test result. In view of these limitations, the question arises as to what role, if any, private laboratories may play in phytosanitary certification.

Private laboratories can play a complementary role provided that they are properly accredited by the U.S. Department of Agriculture (USDA) or the phytosanitary certification agency of the state. The validity and reliability of the laboratory’s diagnostics are both involved. When properly accredited, private laboratories could perform those diagnostic tests the state agency is not proficient in performing or those tests that exceed the testing capacity of the state agency’s diagnostic laboratory. Samples should be submitted “blind” to the private laboratory and results should be reported back to the governmental agency’s diagnostics staff.

Accreditation should include consideration of the following:

– professional staffing: expertise in the disciplines relative to pest and host identification

– good laboratory practices

– adequate facilities and equipment

– access to specialists for verification where necessary

– record-keeping, curation and storage facilities for voucher specimens

– use of valid diagnostic methods

Accreditation should also include quality control monitoring. Monitoring is a question of both validity and reliability. Laboratories must provide valid diagnostics over time. They must be proficient on a consistent basis. Diagnostics monitoring can be accomplished by:

– periodic confirmation of test results by other recognized experts, or

– the submission of blind samples for diagnosis, and

– unannounced inspections to check on laboratory practices.

Accredited private laboratories also must be responsible for the proper maintenance of records and for making those records available during normal business hours for review by the USDA or state certifying agency. Data kept should be specified by the phytosanitary certification agency from among the following:

– sample identification number

– date of receipt of sample and test

– sample size

– test procedure used

– number and source of controls

– test results

– name of identifier

B. Standard

Laboratory diagnostics must be valid and reliable. The use of the proper tests and testing proficiency over time are involved. Private laboratories must be accredited in accord with the criteria specified in this section. Governmental agency laboratories need not be accredited but they must meet the accreditation criteria. Governmental phytosanitary certification agencies are responsible for assuring that laboratory diagnostics are valid and reliable. When specified phytosanitary requirements cannot be met, phytosanitary certification agencies must not issue a phytosanitary certificate.


In addition to the quality control discussed in the previous sections, other quality control requirements must be met by the phytosanitary certification staff itself.

The NPB quality control standard is that each certifying agency must assure:

staff training in sampling methods, preservation and transportation of samples for identification and record-keeping associated with the sample.

proper use and maintenance of equipment and supplies.


A. Foreign Exports

The USDA’s Animal and Plant Health Inspection Service (APHIS) has the primary responsibility for foreign export phytosanitary certification functions in the United States and provides the main interface with foreign plant protection entities and regional plant protection organizations. Duly authorized state collaborators may issue federal phytosanitary certificates for foreign export shipments pursuant to APHIS policies, guidelines and directives. Periodic training is provided to keep state cooperators updated on phytosanitary issues.

Federal, state, and local officials providing phytosanitary certification for foreign export must review the current commodity phytosanitary certification requirements for the importing country. These requirements are maintained by the USDA and made available to certification agencies through the Export Certification Project (EXCERPT).

Occasionally, exporters will have in their possession an import permit issued by the importing country that specifies different phytosanitary certification requirements. In these cases, the requirements of the import permit only apply to the shipment covered by the import permit. And, the import permit requirements on the import permit supersede the country’s published requirements–only for the described shipment.

Phytosanitary officers must make sure that 1) all applicable requirements are met, 2) any required additional declaration is made, and 3) the federal phytosanitary certificate is completed in conformance with all current and applicable requirements.

Copies of federal phytosanitary certificates and the information they contain may be confidential. Federal officers and state collaborators should forward all requests for copies of phytosanitary certificates and applications for inspection of domestic plants and plant products for export, or for information contained in them, to the USDA’s Freedom of Information Act/Privacy Act Coordinator for a determination of confidentiality.

B. Domestic Shipments

Phytosanitary certification officials engaged in the certification of commodities shipped interstate must consult the importing state’s quarantine requirements. This can be done by reviewing the NPB sponsored summary of quarantine requirements published by the American Association of Nurserymen (AAN) and made available to all state agencies.

The confidentiality of state certificates will be governed by state law. So, certification officials should determine whether they are public documents and proceed accordingly if requests for copies or information from them are received.

Industry representatives regularly engaged in the interstate marketing of quarantined commodities should be encouraged to obtain a copy of the AAN published quarantine summary and to use it to make sure that they can meet quarantine requirements before they call for phytosanitary certification.

Whenever there is any question about quarantine or phytosanitary certification requirements, the quarantine state officials in the receiving state should be consulted.

C. Use of Seals

Phytosanitary certificates must represent the specific set of plants inspected by regulatory officials. Affixing a seal to the shipping container and noting the seal number on the phytosanitary certificate helps to prevent tampering with the shipment (swapping, adding, or removing plants).

Employing a seal is particularly beneficial for export shipments. For example, a state official often issues a state phytosanitary certificate for conversion to a federal phytosanitary certificate at the port of export. If the state official applies a seal on the tailgate of the truck container, the PPQ officer knows that the plants presented for export are indeed those same plants. Having no seal leaves open the possibility of tampering.

D. Alternation/Misuse

The alteration or misuse of phytosanitary certificates is illegal. States should review their law to assure that alteration and misuse are unlawful and that appropriate criminal and/or civil penalties are available to deter illegal activities. What constitutes alteration and misuse must be specified. With respect to misuse, shippers sometimes request that financial information be included on phytosanitary certificates. APHIS guidelines make it clear that certificates are not intended to serve a financial purpose.

E. NPB Standard

All phytosanitary certification agencies and phytosanitary certification officials should keep abreast of quarantine requirements and be committed to complying with them. State quarantine officials should cooperate to keep quarantine restrictions and phytosanitary certification requirements at the lowest level possible consistent with reducing risk to an acceptable level and minimizing the cost of phytosanitary certification for the industry.


A. Foreign Exports

The NPB Standard is that certification for the export of commodities to foreign countries be made using the current USDA federal phytosanitary certificate form.

B. Domestic Shipments

The NPB Standard is that whatever certificate is required by the importing state be used.


Agency administrators should establish a system for reviewing the phytosanitary certificates issued by the agency’s staff. The goal should be to discover certification errors and to take measures to prevent them in the future.

Quarantine officials in the importing states should promptly report certification errors and problems direct to the certifying state agency. This will assist administrators in their efforts to assure that their phytosanitary certification program is both valid and reliable.