SCC Newsletter Vol. 20, No. 2, December 2020
Efficacy testing – new EPPO standard for plant defence inducers (PDIs)
Date: 15 December 2020
EPPO has published a new standard (PP1/319 (1) on the general principles for efficacy evaluation of plant protection products with a mode of action as plant defence inducer (PDI). The standard does not cover plant biostimulants as defined by the EU Fertiliser Regulation 2019/1009 laying down the rules on the making available on the market of EU fertilising products. The new European Fertilizer Regulation including biostimulants entered into force in July 2019 and is scheduled to fully apply from July 2022 onwards. Thus, PDI substances are considered to be plant protection products and Regulation 1107/2009 applies.
The standard defines PDIs as follows: “Plant defence inducers (PDIs, also known as plant defence elicitors) include any substance (products of synthetic or natural origin or micro-organisms) which, when applied to a plant, can induce a state of local and/or systemic resistance against biotic stress. PDIs are perceived by plants as a signal of danger and do not target the pest directly. They act to develop or implement different defence mechanisms, leading to increased plant resistance to pests”.
Demonstration of efficacy for PDIs should be based on:
- Preliminary studies especially targeting the Mode of Action (MoA)
The Standard highlights the importance to evaluate and demonstrate the specific Mode, or Modes, of Action by preliminary studies. Based on the product characteristics the Standard suggest several methods such as transcriptional analyses, protein analyses or metabolic analyses to describe the activating or priming defence mechanisms triggered by the specific product.
In addition, in the scope of preliminary studies the standard requires demonstration of the absence of significant direct effects on the pest species to be controlled. For such tests in vitro testing on solid or liquid media is required.
- Efficacy trials demonstrating the level of efficacy of the PDI
The Standard does not replace any of the already available, relevant general EPPO standards but explicitly refers to standards such as PP 1/181, PP 1/226, PP 1/152 or PP 1/225 for general layout and design of efficacy trials. This is also due for low risk products for which the Standard refers to EPPO Standard PP 1/296 on the principles of efficacy evaluation for low risk plant protection products, in particular in regards to information on the required number of trials. Similar in the case of three-dimensional crops for which EPPO Standard PP 1/239 on dose expression for plant protection products has to be used.
Due to the Mode(s) of Action of PDIs, the Standard highlights the importance of application timing and application frequency, the possible delay in plant response, the physiological state of the crop and the persistence of action of the product and its potential cumulative effect to be considered in study design and layout.
Special considerations are required by the Standard in case of tank mixtures or if the product is to be used as a component of an Integrated Pest Management (IPM) strategy. In case specific label claims are added in these regards, evidence from specific efficacy trials have to be provided and the level of efficacy of the PDI as a component in an IPM programme or tank mixture application scheme has to be shown. This is especially due in case of an intended reduction in the dosage or the number of applications of conventional products.
For more information on related topics (such as IPM, low risk product efficacy and product performance, etc.) please refer to our website: