Lesson 2: Pest Identification Case Study

Topic 2: Detection or Identification: Is There a Difference?

There are two types of actions used to find pests: detection and identification. Which action to choose, or whether to choose both, depends on the situation.

Objectives:

To be able to describe the differences between pest detection and pest identification.
To be able to determine which is appropriate for a particular situation: detection, identification, or both.

Once the samples arrive, the authorized laboratory makes decisions about what to do with them based on the information the laboratory needs. The laboratory may choose to run a test to detect a known pest, identify whatever pest is found on a sample, or both.

Let’s explore some differences between identification and detection.

course_01/lesson_02/topic_02/asset_001

Deciding When To Use Detection Tests or Perform an Identification

The decision to run or not run a diagnostic test may depend on the cost of the test and whether the time needed for the test is more or less than the time needed for identification. Listed below are other factors that also influence your decision between detection and identification.

DETECTION

Determines if a specific organism is present.

Used when a reliable diagnostic test exists (for example, a PCR assay or an ELISA test).

Commonly used:

To screen samples for a pest known to occur on a specific commodity.
For rapidly testing samples when a quick answer is needed.
To test for the presence of a small or hard-to-grow organism (bacteria, viruses, some fungi).
To test life stages that do not have diagnostic characteristics (e.g., insect eggs).

IDENTIFICATION

Determines what organism it is.

Used when no specific diagnostic test exists.

Commonly used:

To determine the identity and/or taxonomic placement (class, order, family, genus, species) of an organism present on a sample.
When a diagnostic test is negative, but the cause of observed symptoms needs to be determined.
To support the results of a specific diagnostic test, especially when an organism is detected for the first time in a country or region.

Watch the next video clip to find out if the laboratory decides to run a detection test or perform identification on the barumba berry leaves.

course_01/lesson_02/topic_02/asset_001

Now you see that the government-designated laboratory must be contacted as soon as possible so it can take regulatory action if necessary. Watch the following video to find out what happens next.

course_01/lesson_02/topic_02/asset_001

There are many real-world circumstances that influence the decision to use certain tests when identifying pests. Constraints such as time and cost are important factors to consider. You may also need to consider how reliable and accurate the tests are. Keep in mind that rapid tests are not available for all pests.

In this situation, the IPPL scientists choose to run the PCR assay test first, for three reasons:

Time is short. The samples were collected four weeks ago, which means there has been a lot of time for the disease to spread. The PCR assay test can be performed quickly, in a matter of hours.
The PCR assay is reliable enough that a positive result justifies some preliminary action, such as stopping the movement of produce and equipment between farms until further information can be obtained.
Bacterial cultures take at least one week to grow. More barumba berry farms could be at risk if the original farm does have the disease.

In a real-world situation, you often need to balance the level of pest identification accuracy with the amount of time that can safely be spent to make the identification and manage pests.

When looking for pests, often you must choose between running a detection test and performing an identification. How you choose between these processes depends mainly on circumstances and the level of danger posed by the pest.

To continue, select Topic 3 from the Topics menu above or click here.