1 
 NATIONAL STANDARDS FOR PHYTO SANITARY MEASURES  
 
 
 
 
 
NSPM: 31 
 
 
 
 
 
Methodologies of samples of consignments  
2013  
 
 
 
 
 
 
 
 
 
(This standard is approved by (the NPPO and) the Quarantine Committee of Nepal, chaired by the 
secretary of the Ministry of Agriculture Development on 1st December 2013 and, is submitted by National 
Plant Quarantine Program to the National Notification Authority to be notified to the WTO member states)  
 2 
  
Table of Contents  
1.1 Scope  ................................ ................................ ................................ ................................ ................  1 
1.2 References  ................................ ................................ ................................ ................................ .......  1 
1.3 Definitions  ................................ ................................ ................................ ................................ .........  1 
1.4 Outlines of requirement s ................................ ................................ ................................ ................  1 
2.  Background  ................................ ................................ ................................ ................................ ............  2 
3. Requirements  ................................ ................................ ................................ ................................ .........  3 
3.1  Lot identification  ................................ ................................ ................................ ..........................  3 
3.2  Sample unit  ................................ ................................ ................................ ................................ . 3 
3.3 Statistical and non -statistical sampling  ................................ ................................ ........................  4 
3.3.1 Statistically based sampling ................................ ................................ ................................ .... 4 
3.3.2 Non -statistically based sampling  ................................ ................................ ............................  7 
4. Selecting a sampling method  ................................ ................................ ................................ ...............  8 
5. Sample Size Determination  ................................ ................................ ................................ ..................  9 
6. Varying Level of Detection  ................................ ................................ ................................ .................  10 
7. Outcome of sampling  ................................ ................................ ................................ ..........................  11 
Annexure - I: Details of sampling procedures for different commodities  ................................ .........  12 
                1 
 1. Introduction  
 
1.1 Scope  
This standard provides guidanc e to National  Plant  Protection Organizations (NPPOs) in 
selecting appropriate sampling methodologies for inspection or testing of consignments to verify 
compliance with phytosanitary requirements.  This standard does not give guidance on field 
sampling ( for example, as required for surveys). NSPM preparation based on guidelines and 
recommendations developed within the framework of the IPPC. This standard also adopted the 
principles, recommendations and format of ISPM to achieve international harmonization  of 
phytosanitary measures with the aim to facilitate  and minor change s made in sampling to clarify 
local practices . 
1.2 References  
Cochran, W.G.  1977. Sampling techniques . 3rd edn. New York, John Wiley & Sons. 428 pp.  
ISPM 1 . 2006. Phytosanitary principl es for the protection of plants and the application of  
phytosanitary measures in international trade . Rome, IPPC, FAO.  
ISPM 5 . Glossary of phytosanitary terms . Rome, IPPC, FAO.  
ISPM 11 . 2004. Pest risk analysis for quarantine pests including analysis of  environmental risks  
and living modified organisms . Rome, IPPC, FAO.  
ISPM 20 . 2004. Guidelines for a phytosanitary import regulatory system . Rome, IPPC, FAO.  
ISPM 21 . 2004. Pest risk analysis for regulated non -quarantine pests . Rome, IPPC, FAO.  
ISPM 23 . 2005. Guidelines for inspection . Rome, IPPC, FAO.  
ISPM 31 . 2008 . Methodologies for sampling of consignments  
1.3 Definitions  
Definitions of phytosanitary terms used in the present standard can be found in ISPM 5 
(Glossary of phytosanitary terms ).  
1.4 Out lines of requirements  
The sampling methodologies used by NPPOs in selecting samples for the inspection of 
consignments of commodities moving in international trade are based on a number of sampling 
concepts. These include parameters such as acceptance leve l, level of detection, confidence 
level, efficacy of detection and sample size.  
  
The application of statistically based methods, such as simple random sampling, systematic 
sampling, stratified sampling, sequential sampling or cluster sampling, provides r esults with a 
statistical confidence level. Other sampling methods that are not statistically based, such as 
convenience sampling, haphazard sampling or selective sampling, may provide valid results in 
determining the presence or absence of a regulated pes t(s) but no statistical inference can be 
made on their basis. Operational limitations will have an effect on the practicality of sampling 2 
 under one or another method.  
 
In using sampling methodologies, NPPOs accept some degree of risk that non -conforming l ots 
may not be detected. Inspection using statistically based methods can provide results with a 
certain level of confidence only and cannot prove the absence of a pest from a consignment.  
2.  Background  
This standard provides the basis for, and complement s, NSPM : Guidelines for a phytosanitary 
import regulatory system  and ISPM 23:2005. Inspection of consignments of regulated articles 
moving in trade is an essential tool for the management of pest risks and is the most frequently 
used phytosanitary procedur e worldwide to determine if pests are present and/or the 
compliance with phytosanitary import requirements. It is usually not feasible to inspect entire 
consignments, so phytosanitary inspection is performed mainly on samples obtained from a 
consignment. I t is noted that the sampling concepts presented in this standard may also apply 
to other phytosanitary procedures, notably selection of units for testing. Sampling of plants, 
plant products and other regulated articles may occur prior to export, at the poi nt of import, or 
other points as determined by NPPOs.  
 
It is important that sampling procedures established and used by NPPOs are documented and 
transparent, and take into account the principle of minimum impact (ISPM 1:2006), particularly 
because inspect ion based on sampling may lead to the refusal to issue a phytosanitary 
certificate, refusal of entry, or treatment or destruction of a consignment or part of a 
consignment. Sampling methodologies used by NPPOs will depend on the sampling objectives 
(for ex ample, sampling for testing) and may be solely statistically based or developed noting 
particular operational constraints. Methodologies developed to achieve the sampling objectives, 
within operational constraints, may not yield the same statistical confid ence levels in the results 
as fully statistically based methods, but such methods  may still give valid results depending on 
the desired sampling objective. If the sole purpose of sampling is to increase the chance of 
finding a pest, selective or targeted sampling is also valid.  
 
Objectives of sampling of consignments  
Sampling of consignments is done for inspection and/or testing in order to:  
 detect regulated pests  
 provide assurance that the number of regulated pests or infested units in a consignment 
does not exceed the specified tolerance level for the pest  
 provide assurance of the general phytosanitary condition of a consignment  
 detect organisms for which a phytosanitary risk has not yet been determined  
 optimize the probability of detecting specific regulated pests  
 maximize the use of available sampling resources  
 gather other information such as for monitoring of a pathway   
 verify compliance with phytosanitary requirements  3 
  determine the proportion of the consignment infested.  
It should be noted th at inspection and/or testing based on sampling always involves a degree of 
error. The acceptance of some probability that the pests are present is inherent in the use of 
sampling procedures for inspection and/or testing. Inspection and/or testing using sta tistically 
based sampling methods can provide a level of confidence that the incidence of a pest is below 
a certain level, but it does not prove that a pest is truly absent from a consignment.  
3. Requirements   
3.1  Lot identification  
A consignment may con sist of one or more lots. Where a consignment comprises more than 
one lot, the inspection to determine compliance may have to consist of several separate visual 
examinations, and therefore the lots will have to be sampled separately. In such cases, the 
samples relating to each lot should be segregated and identified in order that the appropriate lot 
can be clearly identified if subsequent inspection or testing reveals non -compliance with 
phytosanitary requirements. Whether or not a lot will be inspected sho uld be determined using 
factors stated in NSPM : Guidelines for inspection  (section 1.5).  A lot to be sampled should be a 
number of units of a single commodity identifiable by its homogeneity in factors such as:  
 Origin  
 grower  
 packing facility /types  
 speci es, variety, or degree of maturity  
 exporter  
 importer  
 area of production  
 season of production  
 regulated pests and their characteristics   
 treatment at origin  
 type of processing.  
The criteria used by the NPPO to distinguish lots should be consistently ap plied for similar 
consignments. Treating multiple commodities as a single lot for convenience may mean that 
statistical inferences can not be drawn from the results of the sampling.  
3.2  Sample unit  
Sampling first involves the identification of the appro priate unit for sampling (for example, a fruit, 
stem, bunch, unit of weight, bag or carton). The determination of the sample unit is affected by 
issues related to homogeneity in the distribution of pests through the commodity, whether the 
pests are sedenta ry or mobile, how the consignment is packaged, intended use, and operational 
considerations. For example, if determined solely on pest biology, the appropriate sample unit 
might be an individual plant or plant product in the case of a low -mobility pest, wh ereas in the 
case of mobile pests, a carton or other commodity container may be the preferred sample unit. 4 
 However, when inspection is to detect more than one type of pest, other considerations (for 
example, practicality of using different sample units) ma y apply. Sample units should be 
consistently defined and independent from each other. This will allow NPPOs to simplify the 
process of making inferences from the sample to the lot or consignment from which the sample 
was selected.   
3.3 Statistical and non-statistical sampling   
The sampling method is the process approved by the NPPO to select units for inspection and/or 
testing. Sampling for phytosanitary inspection of consignments or lots is done by taking units 
from the consignment or lot without replacem ent of the units selected1. NPPOs may choose 
either a statistically based or non -statistical sampling methodology.  
Sampling based on statistical or targeted methods is designed to facilitate the detection of a 
regulated pest(s) in a consignment and/or lot .  
3.3.1 Statistically based sampling  
Statistically based sampling methods involve the determination of a number of interrelated 
parameters and the selection of the most appropriate statistically based sampling method.  
3.3.1.1 Parameters and related conc epts  
Statistically based sampling is designed to detect a certain percentage or proportion of 
infestation with a specific confidence level, and thus requires the NPPO to determine the 
following interrelated parameters: acceptance number, level of detectio n, confidence level, 
efficacy of detection and sample size. The NPPO may also establish a tolerance level for certain 
pests (for example, regulated non -quarantine pests).  
3.3.1.1.1 Acceptance number  
The acceptance number is the number of infested units o r the number of individual pests that 
are permissible in a sample of a given size before phytosanitary action is taken. Many NPPOs 
determine this number to be zero for quarantine pests. For example, if the acceptance number 
is zero and an infested unit is detected in the sample then phytosanitary action will be taken. It 
is important to appreciate that a zero acceptance number within a sample does not imply a zero 
tolerance level in the consignment as a whole. Even if no pests are detected in the sample the re 
remains a probability that the pest may be present in the remainder of the consignment, albeit at 
a very low level. The acceptance number is linked to the sample. The acceptance number is the 
number of infested units or the number of individual pests th at are permissible in the sample 
whereas the tolerance level (see section 3.1.1.6) refers to the status of the entire consignment .   
 
3.3.1.1.2 Level of detection  
The level of detection is the minimum percentage or proportion of infestation that the sampl ing 
                                                           
1  Sampling without replacement is selecting a unit from the consignment or lot without replacing the unit before 
the next units are selected. Sampling without replacement does not mean that a selected item cannot be returned 
o a consignment (except for destructive sampling); it means only that the inspector should not return it before 
selecting the remainder of the sample.  
 5 
 methodology will detect at the specified efficacy of detection and level of confidence and which 
the NPPO intends to detect in a consignment.   
The level of detection may be specified for a pest, a group or category of pests, or for 
unspecified pests. The level of detection may be derived from:  
 a decision based on pest risk analysis to detect a specified level of infestation (the 
infestation determined to present an unacceptable risk)  
 an evaluation of the effectiveness of phytosanitary measures applied  before inspection  
 an operationally based decision that inspection intensity above a certain level is not 
practical.  
 
3.3.1.1.3 Confidence level  
The confidence level indicates the probability that a consignment with a degree of infestation 
exceeding the  level of detection will be detected. A confidence level of 95% is commonly used. 
The NPPO may choose to require different confidence levels depending on the intended use of 
the commodity. For example, a higher confidence level for detection may be require d for 
commodities for planting than for commodities for consumption, and the confidence level may 
also vary with the strength of the phytosanitary measures applied and historical evidence of 
non-compliance. Very high confidence level values quickly become difficult to achieve, and 
lower values become less meaningful for decision -making. A 95% confidence level means that 
the conclusions drawn from the results of sampling will detect a non -compliant consignment, on 
average, 95 times out of 100, and therefore,  it may be assumed that, on average, 5% of non -
compliant consignments will not be detected.  
3.1.1.4 Efficacy of detection   
The efficacy of detection is the probability that an inspection or test of an infested unit(s) will 
detect a pest. In general the ef ficacy should not be assumed to be 100%. For example, pests 
may be difficult to detect visually, plants may not express symptoms of disease (latent infection), 
or efficacy may be reduced as a result of human error. It is possible to include lower efficacy 
values (for instance, an 80% chance of detecting the pest when an infested unit is inspected) in 
the determination of sample size.  
3.3.1.1.5 Sample size  
The sample size is the number of units selected from the lot or consignment that will be 
inspected or tested. Guidance on determining the sample size is provided in section 5.  
3.1.1.6 Tolerance level  
Tolerance level refers to the percentage of infestation in the entire consignment or lot that is the 
threshold for phytosanitary action.   6 
 Tolerance levels may be established for regulated non -quarantine pests (as described in NSPM : 
Pest risk analysis for regulated non -quarantine pests , section 4.4) and may also be established 
for conditions related to other phytosanitary import requirements (for example, bar k on wood or 
soil on plant roots).  
Most NPPOs have a zero tolerance level for all quarantine pests, taking into account 
probabilities of pest presence in the non -sampled units as described in section 3.1.1.1. 
However, an NPPO maydetermine to establish a t olerance level for a quarantine pest based on 
pest risk analysis (as describedin NSPM : pest risk analysis for quarantine pests including 
analysis of environmental risks and living modified organisms)  and then determine sampling 
rates from this. For example , NPPOs may determine a tolerance level that is greater than zero 
because small numbers of the quarantine pest may be acceptable if the establishment potential 
of the pest is considered low or if the intended end use of the product (for example, fresh frui t 
and vegetables imported for processing) limits the potential of entry of the pest into endangered 
areas.  
3.3.1.2 Links between the parameters and tolerance level  
The five parameters (acceptance number, level of detection, confidence level, efficacy of 
detection and sample size) are statistically related. Taking into account the established 
tolerance level, the NPPO should determine the efficacy of the detection method used and 
decide upon the acceptance number inthe sample; any two of the remaining thre e parameters 
can also be chosen, and the remainder will be determined from the values chosen for the rest.  
If a tolerance level greater than zero has been established, the level of detection chosen should 
be equal to (or less than, if the acceptance numbe r is greater than zero) the tolerance level to 
ensure that consignments having an infestation level greater than the tolerance level will be 
detected with the specified confidence level.   
If no pests are detected in the sample unit, then the percentage of  infestation in the 
consignment can not be stated beyond the fact that it falls below the level of detection at the 
stated confidence level. If the pest is not detected with the appropriate sample size, the 
confidence level gives a probability that the tol erance level is not exceeded.   
3.1.3 Statistically based sampling methods  
 
3.3.1.3.1 Simple random sampling  
Simple random sampling results in all sample units having an equal probability of being selected 
from the lot or consignment. Simple random sampl ing involves drawing the sample units in 
accordance with a tool such as a random numbers table. The use of a predetermined 
randomization process is what distinguishes this method from haphazard sampling (described in 
section 3.2.2).  
This method is used whe n little is known about the pest distribution or rate of infestation. Simple 
random sampling can be difficult to apply correctly in operational situations. To use this method, 
each unit should have an equal probability of selection. In cases where a pest i s not distributed 
randomly through the lot, this method may not be optimal. Simple random sampling may require 
greater resources than other sampling methods. The application can be dependent on the type 
and/or configuration of the consignment.  
3.1.3.2 Sys tematic sampling  
Systematic sampling involves drawing a sample from units in the lot at fixed, predetermined 
intervals. However, the first selection must be made at random through the lot. Biased results  
are possible if pests are distributed in a manner s imilar to the interval chosen for sampling.  7 
 Two advantages of this method are that the sampling process may be automated through 
machinery and that it requires the use of a random process only to select the first unit.  
3.3.1.3.3 Stratified sampling  
Stratified sampling involves separating the lot into separate subdivisions (that is, strata) and 
then drawing the sample units from each and every subdivision. Within each subdivision, 
sample units are taken using a particular method (systematic or random). Un der some 
circumstances, different numbers of sample units may be taken from each subdivision – for 
instance, the number of sample units may be  proportional to the size of the subdivision, or 
based on prior knowledge concerning the infestation of the subdiv isions.  
 
If at all feasible, stratified sampling will almost always improve detection accuracy. The smaller 
variation associated with stratified sampling yields more accurate results. This is especially true 
when infestation levels may vary across a lot d epending on packing procedures or storage 
conditions. Stratified sampling is the preferred choice when knowledge about the pest 
distribution is presumed and operational considerations will allow it.  
3.3.1.3.4 Sequential sampling  
Sequential sampling invol ves drawing a series of sample units using one of the above methods. 
After each sample (or group) is drawn, the data ar e accumulated and compared with 
predetermined ranges to decide whether to accept the consignment, reject the consignment or 
continue samp ling.   
 
This method can be used when a tolerance level greater than zero is determined and the first 
set of  sample units does not provide sufficient information to allow a decision to be made on 
whether or not the tolerance level is exceeded. This method would not be used if the 
acceptance number in a sample of any size is zero. Sequential sampling may reduce the 
number of samples required for a decision to be made or reduce the possibility of rejecting a 
conforming consignment .  
 
3.3.1.3.5 Cluster samplin g  
Cluster sampling involves selecting groups of units based on a predefined cluster size (for 
example, boxes of fruit, bunches of flowers) to make up the total number of sample units 
required from the lot. Cluster sampling is simpler to evaluate and more reliable if the clusters are 
of equal size. It is useful if resources available for sampling are limited and works well when the 
distribution of pests is expected to be random.   
 
Cluster sampling can be stratified, and can use either systematic or random methods for 
selecting the groups. Of the statistically based methods, this method is often the most practical 
to implement.   
3.3.1.3.6 Fixed proportion sampling  
Sampling a fixed proportion of the units in the lot (for example, 2%) results in inconsistent l evels 
of detection or confidence levels when lot size varies. As shown in Appendix 5, fixed proportion 
sampling results in changing confidence levels for a given level of detection, or in changing 
levels of detection for a given confidence level.  
3.3.2 No n-statistically based sampling  
Other sampling methods that are not statistically based, such as convenience sampling, 
haphazard sampling or selective or targeted sampling, may provide valid results in determining 
the presence or absence of a regulated pes t(s). The following methods may be used based on 8 
 specific operational considerations or when the goal is purely detection of pests.   
 
3.3.2.1 Convenience sampling  
Convenience sampling involves selecting the most convenient (for example, accessible, 
cheap est, fastest) units from the lot, without selecting units in a random or systematic manner.   
3.3.2.2 Haphazard sampling  
Haphazard sampling involves selecting arbitrary units without using a true randomization 
process. This may often appear to be random b ecause the inspector is not conscious of having 
any selection bias. However, unconscious bias may occur, so that the degree to which the 
sample is representative of the lot is unknown.  
3.3.2.3 Selective or targeted sampling  
Selective sampling involves de liberately selecting samples from parts of the lot most likely to be 
infested, or units that are obviously infested, in order to increase the chance of detecting a 
specific regulated pest. This method may rely on inspectors who are experienced with the 
commodity and familiar with the pest’s biology. Use of this method may also be triggered 
through a pathway analysis identifying a specific section of the lot with a higher probability of 
being infested (for example, a wet section of timber may be more likely to harbour nematodes). 
Because the sample is targeted, and hence statistically biased, a probabilistic statement about 
the infestation  level in the lot can not be made. However, if the sole purpose of sampling is to 
increase the chance of finding a regula ted pest(s), this method is valid. Separate samples of the 
commodity may be required to meet general confidence in detection of other regulated pests. 
The use of selective or targeted sampling may limit the opportunities to derive information about 
the ove rall pest status of the lot or consignment, because sampling is focused on where specific 
regulated pests are likely to be found not on the remainder of the lot or consignment.   
4. Selecting a sampling method  
In most cases the selection of an appropriate  sampling method is necessarily dependent on 
information available about pest incidence and distribution in the consignment or lot as well as 
the operational parameters associated with the inspection situation in question. In most 
phytosanitary application s operational limitations will dictate the practicality of sampling under 
one or another method. Subsequently determining the statistical  validity of practical methods 
will narrow the field of alternatives.   
The sampling method that is ultimately selecte d by the NPPO should be operationally feasible 
and be the most appropriate to achieve the objective and be well documented for transparency. 
Operational feasibility is clearly linked to judgments  concerning situation -specific factors, but 
should be consist ently applied . 
If sampling is undertaken to increase the chance of detecting a specific pest targeted sampling 
(described in section 3.2.3) may be the preferred option as long as the inspectors can identify 
the section(s) of the lot with a higher probabili ty of being infested. Without this knowledge, one 
of the statistically based methods will be more appropriate. Non -statistically based sampling 
methods do not result in each unit having an equal probability of being included in the sample 
and do not allow for quantification of a confidence level or level of detection.  9 
 Statistically based methods will be appropriate if sampling is undertaken to provide information 
about the general phytosanitary condition of a consignment, to detect multiple quarantine pest s 
or to verify compliance with phytosanitary requirements.  
In selecting a statistically based method, consideration may be given to how the consignment 
has been treated in harvesting, sorting and packing, and the likely distribution of the pest(s) in 
the lot. Sampling methods may be combined: for instance, a stratified sample may have either 
random or systematic selection of sample units (or clusters) within strata.  
If sampling is undertaken to determine whether a specific non -zero tolerance level has bee n 
exceeded, a sequential sampling method may be appropriate.   
Once a sampling method has been selected and correctly applied, repeating the sampling with 
the aim of achieving a different result is unacceptable. Sampling should not be repeated unless 
consi dered necessary for specific technical reasons (for example, suspected incorrect 
application of sampling methodology).  
National Plant Quarantine Program has prepared Operational Manual for Import and Export 
Certification in 2005. In the manual, procedures  for samplings; sampling  different commodities 
like seeds for propagation, cut flowers, fruit and vegetables have been described in detail 
(Annexture -1, attached ). For the sample size of seeds, sampling procedures prescribed by 
International Seed Te sting Association (ISTA) Rules, 1976, have been recommended. Attached 
operational manual (see appendix -1) which is slight modification of operation manual prepared 
by NPQP is recommended to follow.  
5. Sample Size Determination  
To determine the number of samples to be taken, the NPPO should select a confidence level 
(for example, 95%), a level of detection (for example, 5%) and an acceptance number (for 
example, zero), and determine the efficacy of detection (for example, 80%). From these values 
and the lot size, a sample size can be calculated. Appendixes 2 –5 set out the mathematical 
basis for sample size determination. Section 3.1.3 of this standard provides guidance on the 
most appropriate statistical based sampling method when considering the distribution of th e 
pest in the lot.  
5.1 Pests distribution unknown in the lot  
Because sampling is done without replacement and the population size is finite, the 
hypergeometric distribution should be used to determine the sample size. This distribution gives 
a probabilit y of detecting a certain number of infested units in a sample of a given size drawn 
from a lot of a given size, when a specific number of infested units exist in the lot (see Appendix 10 
 2). The number of infested units in the lot is estimated as the level of  detection multiplied by the 
total number of units in the lot.  
As lot size increases, the sample size required for a specific level of detection and confidence 
level approaches an upper limit. When the sample size is less than 5% of the lot size, the 
samp le size can be calculated using either the binomial or Poisson distribution (see Appendix 
3). All three distributions (hypergeometric, binomial and Poisson) give almost identical sample 
sizes for specific confidence and  detection levels with large lot size s, but binomial and Poisson 
distributions are easier to calculate.  
5.2 Pest distribution aggregated in the lot  
Most pest populations are aggregated to some degree in the field. Because commodities may 
be harvested and packed in the field without being gr aded or sorted, the distribution of infested 
units in the lot may be clustered or aggregated. Aggregations of infested units of a commodity 
will always  lower the likelihood of finding an infestation. However, phytosanitary inspections are 
aimed at detectio n of infested units and/or pest(s) at a low level. The effect of aggregation of the 
infested units on the efficacy of detection of a sample and on the required sample size is small 
in most cases. When  NPPOs identify that there is a high likelihood that the re will be aggregation 
of infested units in the lot a stratified sampling method may help increase the chance of 
detecting an aggregated infestation.   
When pests are aggregated, the calculation of sample size should ideally be performed using a 
beta-binom ial distribution (see Appendix 4). However, this calculation requires knowledge of the 
degree of aggregation, which is generally not known and therefore this distribution may not be 
practical for general use. One of the other distributions (hypergeometric,  binomial or Poisson) 
can be used; however, the confidence level of the sampling will decline as the degree of 
aggregation increases.  
6. Varying level of detection  
The choice of a constant level of detection may result in a varying number of infested uni ts 
entering with imported consignments because lot size varies (for example, a 1% infestation level 
of 1000 units corresponds to 10 infested units, while a 1% infestation level of 10,000 units 
corresponds to 100 infested units). Ideally the selection of a level of detection will reflect in part 
the number of infested units entering on all consignments within a particular period of time. If 
NPPOs want to manage the number of infested units entering with each consignment as well, a 
varying level of detection may be used. A tolerance level would be specified in terms of a 
number of infested items per consignment, and the sample size would be set in order to give the 11 
 desired confidence and detection levels.  
7. Outcome of sampling  
The outcome of activities and techniques related to sampling may result in phytosanitary action 
being taken (further details can be found in NSPM : Guidelines for inspection ).   
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 12 
 Annexure - I: Details of sampling procedures for different commodities  
 
A. Seed for propag ation  
Sampling  
 The sampling of the seed for propagation shall be in accordance with the sampling 
procedures prescribed by International Seed Testing Association (ISTA) Rules, 1976.  
 The maximum size of seed lot for agricultural and horticultural crops is 20  MTs for seeds of 
the same size of wheat or larger. However for small size seeds the lot size is 10 MTs.For 
tree species with seeds of the size of Fagus  species or larger, the maximum is 5 MTs, and 
for seeds still smaller in size it is 5 MTs.  
 
 Sampling reg ime for seed lots in bulk  
Lot size  No. of primary samples required to be drawn  
Upto 500 kg.  Atleast five primary samples.  
501 to 3000 kg.  One primary sample for each 300 kg.but not less than 5 
samples  
3001 to 20,000 kg.  One primary sample for each 500 kg but not less than 10 
samples  
      Sampling for seed lots in bags or containers of uniform size  
Lot size   Samples requiredto be drawn  
upto 5 containers  Sample from each container.  
6 -30 containers  Sample in every 3 containers but not less than 5 samp les 
are drawn  
31 or more 
containers  sample in 1 of  every 5 containers but not less than 10  
 
 Sampling is usually carried out by the slotted tube sampler in case of bagged cargo. In 
 case of sampling of seed in bulk from storage bins a sampler is used. A lternatively Nobbe
 Trier is used for sampling of seed from bagged cargo.  
 In case of propagating plant material such as bulbs/ tubers/ cuttings/ saplings etc., atleast 
0.1% of units are sampled for inspection in case of bulk consignments.  
 In case of small consignments cent per cent inspection is carried out.  
 ISTA rules provide minimum weight of submitted samples for various agricultural, 
horticultural and tree seeds as given below \ 13 
  
Minimum weight of submitted samples for various crop species as prescribed by ISTA  
Minimum weight of 
submitted samples  Crop species  
1000 gms  Avena sativa, Cajanu  scajan, Cicer arietinum, Cucurbita spp., Dolichos 
lablab, Fagus sylvatica, Glycine max, Gossypium spp., Hordeum vulgare,  
Leucaenaleucocephala, Phaseolus  spp., Pinuspine a, Pisum  sativum , 
Secalecereale, Vigna  unguiculata, Triticum  aestivum, Vicia  spp., Zea 
maydis  
900 gms  Prunusavium, Sorghum vulgare  
500 gms  Beta vulgaris, Prunusserotina  
400gms  Oryza sativa, Calopogonium  mucunoides  
250 gms  Sorghum sudanense, Spinacea  oleracea, Trifolium  subterraneum  
200 gms  Sinapis alba  
150 gms  Capsicum spp., Cucumis  melo, Cucumis  sativus, Llinumus  itatissimum, 
Lycopersicaon  esculentum, Pennisetum  typhoides, Solanum  melongena  
100 gms  Brassica napus, Brassica oleracea, Brassica rapa, Pi nuscaribaea  
80 gms  Allium cepa, Stylosanthes spp.  
70 gms  Allium porum, Sesamumindicum  
60 gms  Cuminumcyminum, Trifoliumalexandrium  
50 gms  Allium fistulosum  ,Cichorium  intyvus, Malus spp., Medicago  lupulina, 
Medicago sativa, Meliolotus spp., Rosa spp., T rifolium pretense .  
40 gms  Brassica chinensis, Brassica nigra , Cichoriu  mendivia, Picea  abies  
30 gms  Daucus  carota, Lactuca sativa, Ulmus spp.  
25 gms  Apium  graveolens, Nicotiana tabacum,  
 
B. Grain/ pulses for consumption  
The sampling procedures for s uch consignments  in bags and in bulk is given below:  
Sampling for bagged cargo of cereal grains/ pulses  14 
 Lot size   No. of bags to be sampled*  
Upto 100 bags  20 
101 to 300 bags  32 
301 to 500 bags  50 
501 to 1000 bags  80 
1001 and above  125 
                                    *   If high risk, double the number of sample  
 
                     Sampling of grains/ pulses  in bulk  
Lot size  No. of bags to be sampled  
Upto 300 MT  30 
301 to 1000 MT  50 
1001 and above  100 
 
 The samples shall be drawn at random  from bags with the help of a slotted tube sampler or 
by the corn sampler in case of large size seed as that of maize, pea, beans and gram etc.  
 Sampling of the grain from the bins shall be carried out by a bin sampler or thermosampler.  
 
 In case of milled  plant products such as wheat, flour, maida, spices powder, oilseed extracts 
etc. the sampling by hand is practised.  
 A scoop or pelican type sampler is used for drawing the representative samples from the 
convoy or at different intervals.  
 Each of the pri mary samples  drawn shall be thoroughly mixed and balanced to constitute a 
homogeneous composite sample. From the composite sample a sample of 1 kg. isdrawn 
and submitted in sealed polyethylene covers with appropriate label for detailed laboratory 
testing.  A minimum of 3 samples are drawn for commodity for detailed laboratory testing.  
 In case consignment is  imported in containers atleast one sample shall be drawn for each 
container.  
 
 
 
 
 15 
 Sampling for root crops, bulbs, corms and roots  
Quantity in a  lot (k g)  Amount of sample to be inspected  
Less than 10 kg  Inspect in total  
11-100 kg  Inspect at least 10%, but at least 100 PCs  
Over 101 kg  Inspect at least 5 %, but not more than 200 
PCs 
 
Sampling for cut flowers  
Number of cut flowers in a consignment  Numb er of plants to be inspected*  
Less than 100  Inspect all  
101 – 500 30 %, at least 120  
500 – 2000  10 % , at least 80  
More than 2000  5 %, not more than 200  
                    *    Double the sample if risk is high  
 
E. Potted plants  
Plants in pots, wheth er in flower or not, may be host plants for many pests and diseases.. The 
intensity and sampling depends on risk category of the plant species.  
Pay attention on living insects, mainly thrips and leafminers, and on any symptom of virus or 
bacterial disease.  
Each species and variety  shall be inspected separately.  
Sampling of potted plants  
Number of plants in a lot  Number of plants to be inspected  
Less than 50  Inspect in total  
51-200 10 % or at least 8  
201-500 5% or at least 15  
More than 500  3% or at least  30 16 
 - Shake or tap sampled plants over the white inspection surface. Tap with enough force to 
dislodge any insect larvae, adult insects, or fecal material.  
- Examine the inspection surface to catch thrips, aphids, and early instars larvae. Look for 
anyth ing that moves and for fecal material that may have been dislodged.  
- Pay attention to growing medium in pots, which should be clean growing peat without   organic 
soil. 
 
F.  Small plants and cuttings of ornamentals and vegetable plants  
Small plants and c uttings of ornamentals need to be inspected carefully. Special attention shall 
be paid on chrysanthemum, gerbera, gypsophila, impatiens and on small plants of all 
vegetables (tomato, cucumber, melons etc).  
Each species and variety shall be inspected separa tely.  
Small commodities (less than 100 pieces) shall be inspected in total. The larger consignments  
shall be selected at random but at least 100 piecesshall be inspected.  
Sampling of plants/ cuttings of ornamentals/ vegetable plants  
Number of plants/ cut tings in a lot  Number of plants/ cuttings to be inspected *  
Less than 500  Inspect all  
501-2000  15 %, at least 150  
2001 -10000  8%, at least 300  
Over 10000  5%, not more than 500  
*      If high risk more samples  
 
Pay attention especially on thrips speci es, leafminers and whiteflies.  
Any sign of discoloration may indicate virus of bacterial disease. In these cases samples shall 
be taken for laboratory analyses.  
In case infestation is suspected, but cannot be proved or indicated, small plants and cuttings 
may be ordered to be grown in post -entry quarantine.  
G. Nursery products (fruit trees, small plants of berries and grape wine, ornamental trees, 
perennials)  17 
 Nursery products are usually imported with roots protected by soil or peat or mixture or both. 
Pay attention to soil, and if it's field soil, take samples for nematode analyses. Amount of field 
soil in roots shall not exceed 1% in weight.  
Inspect small commodities in total.  
In case of larger commodities select at random 10% of plants for inspections b ut make sure that 
you select at least 50 pieces.  
Open soil or peat balls, inspect the roots, which may be infested by nematodes or bacteria 
(knots, malformations).  
Sampling for nursery products  
Number of plants in a lot  Number of plants to be inspected  
Less than 50  Inspect all  
51-200 10%, at least 15  
201-500 5%, at least 20  
Over 500  3%, at least 30  
 
Pay attention to root knots, discoloured stems, dark spots , loose bark in stems. Problems with 
nursery plants are viral and bacterial diseases, which are  difficult to observe and identify, and 
which may appear only after certain period of growing.  
Pay attention to plant species which are known as host plants of known quarantine pests    
H.  Fruits, berries, vegetables   
All imported consignments shall be inspected.  
Each plant species and variety is inspected separately.  
Products are usually transported in wooden or cardboard cages. Pay attention to possible soil or 
debris in bottom of cages and on packaging material (hay, plant material etc).  
Some fruits   and vegetables (tomato, cucumber, melons etc) may be attached with leaves or  
stems, which may be infested by insects or diseases.     
It is important that the sample is a good representative of the whole shipment. Keep in mind that 
in containerized ship ments, trader may put the cleanest boxes at the tailgate section of the 
container.  18 
 Sampling of fruits/ berries/ vegetables received in wooden and cardboard cages  
Number of units (cages etc)  Number of units to be sampled for 
inspection  
Less than 10  All un its 
11 – 100 10 % or at least 5  
101-1000  2% or at least 10  
More than 1000  1 % or at least 20  
Pay attention to any sign symptoms of disease (rots, spots, blemishes), insects, extraneous 
plant  
 
I. Potato  
All consignments of potato intended to be importe d shall be inspected. Each lot should be 
inspected separately.If  potatoes are packed, the sack (usually 20 -25 kg for ware potatoes and 
50 kg for seed potatoes) are  used as unit for inspection. If the potatoes are in bulk, it may be 
impossible to identify  individual lots and the whole consignment should be considered as one 
lot. Special attention shall be paid on possible soil and debris inside and between sacks, and in 
container.  
Sampled tubers shall be cut in sheets by knife, starting from heel end. Purp ose is to verify 
possible visual symptoms of bacterial diseases ( Clavibacter or Ralstonia )  or fungus diseases. 
For visual inspection at least 200 tubers shall be cut of each lot.   
If symptoms of infestation are found, or inspector suspects infestation bu t can not verify it by 
visual inspection, samples are taken to laboratory identification. For laboratory analyses the 
heels ands of at least 200 tubers of each lot has to be cut.  
Samples shall be taken also of loose soil found in sacks, for potato nematod e analyses.  
Seed potato shall be inspected using the sampling and testing guidelines of ISTA.  
 
Inspecting and sampling  
These are numbers used for at random inspection. If inspector finds any sign of suspected 
infestation, inspection shall be targeted an d more samples shall be taken.  19 
 Sampling for table, ware and industrial potato  
Size of consignment  Number of bags (ca 20 kg) to 
be inspected  Size of sample  
One container or wagon  
Less than 30 ton and 
consists of more than 1 lot  If 1 lot - inspect 5 bags  
If 2-5 lots - 1 sack per lot  
If more than 5 lots - less than 1 
bag per lot  In total 200 tubers, collected 
from inspected bags  
30 - 50 ton  5 bags per lot  In total 200 tubers, collected 
from each inspected bags  
50 - 200 ton  1 bag per each 10 tons  In total  200 tubers, collected 
from each inspected bags  
Over 200 ton  1 bag per each 10 tons  1 tuber per ton  
 
Sampling for certified seed potato  
Less than 50 ton  5 bags  200 tubers  
50 - 200 ton  1 bag per 10 ton  200 tubers  
More than 200 ton  1 bag per 10 ton  1 tub er per ton  
 
Sampling of potatoes imported in bags  
Number of bags in consignment  Number of bags to be sampled  
Less than 10  All bags  
11 – 100 10 bags selected at random  
More than 100  5%, at least 10 bags  
 20 
 Sampling of potatoes imported as loose consignm ent 
Quantity in lot (ton)  Number of subsamples and total quantity 
of material in bulk sample  
Less than 10 ton  5 subsamples, 1 litre  
11-50 ton  8 subsamples, 1,5 litre  
51 - 100 ton  10 subsamples, 5 litre  
More than 100 ton  15 subsamples, 10 litre  
 
 
 
Annexure - I 
 
Details of sampling procedures for different commodities  
 
A. Seed for propagation  
 
Sampling  
 
 The sampling of the seed for propagation shall be in accordance with the sampling 
procedures prescribed by International Seed Testing Association (I STA) Rules, 1976.  
 
 The maximum size of seed lot for agricultural and horticultural crops is 20 MT s for seeds 
of the same size of wheat or larger. However for small s ize seeds the lot size is 10 
MTs.For tree species with seeds of the size of Fagus  species or  larger, the maximum is 5 
MTs, and for seeds still smaller in size it is 5 MTs.  
 
 Sampling regime for seed lots in bulk  
 
Lot size  No. of primary samples required to be drawn  
Upto 500 kg.  Atleast five primary samples.  
501 to 3000 kg.  One primary sample f or each 300 kg.but not less than 5 
samples  
3001 to 20,000 kg.  One primary sample for each 500 kg but not less than 10 
samples  
 
 
Sampling for seed lots in bags or containers of uniform size  
Lot size   Samples requiredto be drawn  
upto 5 containers  Sample f rom each container.  
6 -30 containers  Sample in every 3 containers but not less than 5 samples 
are drawn  
31 or more 
containers  sample in 1 of  every 5 containers but not less than 10  
 
 Sampling is usually carried out by the slotted tube sampler in case o f bagged cargo. In 
 case of sampling of seed in bulk from storage bins a sampler is used. Alternatively Nobbe
 Trier is used for sampling of seed from bagged cargo.  
 
 In case of propagati ng plant material such as bulbs/ tubers/ cuttings / saplings etc., atlea st 
0.1% of units are sampled for inspection in case of bulk consignments.  
 
 In case of small consignments cent per cent inspection is carried out.  
 
 ISTA rules provide minimum weight of submitted samples for various agricultural, 
horticultural and tree seed s as given below.  
 
 
 
 
Annexure - I 
 
Details of sampling procedures for different commodities  
 
A. Seed for propagation  
 
Sampling  
 
 The sampling of the seed for propagation shall be in accordance with the sampling 
procedures prescribed by International Seed Testing Association (I STA) Rules, 1976.  
 
 The maximum size of seed lot for agricultural and horticultural crops is 20 MT s for seeds 
of the same size of wheat or larger. However for small s ize seeds the lot size is 10 
MTs.For tree species with seeds of the size of Fagus  species or  larger, the maximum is 5 
MTs, and for seeds still smaller in size it is 5 MTs.  
 
 Sampling regime for seed lots in bulk  
 
Lot size  No. of primary samples required to be drawn  
Upto 500 kg.  Atleast five primary samples.  
501 to 3000 kg.  One primary sample f or each 300 kg.but not less than 5 
samples  
3001 to 20,000 kg.  One primary sample for each 500 kg but not less than 10 
samples  
 
 
Sampling for seed lots in bags or containers of uniform size  
Lot size   Samples requiredto be drawn  
upto 5 containers  Sample f rom each container.  
6 -30 containers  Sample in every 3 containers but not less than 5 samples 
are drawn  
31 or more 
containers  sample in 1 of  every 5 containers but not less than 10  
 
 Sampling is usually carried out by the slotted tube sampler in case o f bagged cargo. In 
 case of sampling of seed in bulk from storage bins a sampler is used. Alternatively Nobbe
 Trier is used for sampling of seed from bagged cargo.  
 
 In case of propagati ng plant material such as bulbs/ tubers/ cuttings / saplings etc., atlea st 
0.1% of units are sampled for inspection in case of bulk consignments.  
 
 In case of small consignments cent per cent inspection is carried out.  
 
 ISTA rules provide minimum weight of submitted samples for various agricultural, 
horticultural and tree seed s as given below.