ISO 6639-1:2025

International
Standard
ISO 6639-1
Second edition
Cereals and pulses —
2025-06
Determination of hidden insect
infestation —
Part 1:
General principles
Céréales et légumineuses — Détermination de l'infestation
cachée par les insectes —
Partie 1: Principes généraux
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Sampling . 2
5 Methods of determining hidden infestation. 2
Bibliography . 5

iii
Foreword
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This document was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 4, Cereals
and pulses.
This second edition cancels and replaces the first edition (ISO 6639-1:1986), which has been technically
revised.
The main changes are as follows:
— according to the insect developmental stages causing damage, the definition and general of hidden
infestation has been modified;
— the sampling location, time and period have been modified;
— rapid methods in Table 1 have been modified based on ISO 6639-4;
— some potential techniques in Table 2 have been added.
A list of all parts in the ISO 6639 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
Some species of adult insects are especially adapted to attack whole grains and normally spend a considerable
part of the life cycle, including the entire larval feeding period, inside grains. Other species in their larval
stage create an entrance hole within a grain, covering it after entry and an adult exit hole is created after the
process of pupation, from which it then emerges. These insects constitute a hidden infestation that cannot
readily be seen in consignments or samples (as opposed to an initial observed infestation).
Most insect pests of stored grains are very small, under 5 mm in length, cryptic in behaviour and dull in
colour. Those that fly do so mostly in dull light or at high temperatures. Thus, even when they are living
freely outside the grains, and do not constitute a hidden infestation as described above, they are not easy to
detect unless populations are large enough to induce noticeable activity.
Being mobile, at least in the free-living form, insects are capable of moving through a bulk of grain and
tend to concentrate in those parts of the bulk most favourable for feeding and breeding. Such centres of
insect activity are not necessarily static; they can expand, contract or move for many complex reasons. The
most important reasons are changes in the physical condition of the grain (e.g. temperature and moisture
content) and overcrowding of the insects due to rapid breeding. Thus, the distribution of insects in a bulk of
grain is rarely random, and their detection requires specialist knowledge and techniques.

v
International Standard ISO 6639-1:2025(en)
Cereals and pulses — Determination of hidden insect
infestation —
Part 1:
General principles
1 Scope
This document establishes general principles for the methods of the determination of hidden insect
infestation in cereals and pulses.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
initial observed infestation
free-living insects that are immediately apparent to the eye when the sample is first examined
3.2
hidden infestation
insects which are present within individual grains (3.3) either because they are at juvenile stages and have
developed from eggs laid inside the grains, or because they lay eggs outside of the grain kernel and the larva
emerging from egg gnaws a hole, no larger than a pin prick, through which it enters the kernel till adult
Note 1 to entry: Hidden infestation is not normally apparent upon first examination of the sample.
3.3
grain
cereal grains and/or seeds of pulses
3.4
increment
amount of material taken at one time at each individual sampling point throughout a lot
[SOURCE: ISO 5527:2015, 2.6.1.10]

4 Sampling
Sampling for insects is critical for management. The methods of sampling cereals and pulses specified in
ISO 24333 are not appropriate for sampling for hidden infestation in cereals and pulses, because of the non-
random distribution of insect populations, particularly after a period of prolonged storage or transportation.
Specialized techniques, not intended or suitable for determining grain quality, as specified by ISO 24333,
include selecting samples from the top and outer layer of bags or pac
...