A variety of means are used to control crop diseases and pests, including plant protection products. However, undesirable insects, fungi or plants may develop resistance to these products in certain conditions of use. The selection of resistance makes plant protection products less effective, and result in their being used in increasing quantities, before becoming completely useless. This concerns both synthetic active substances and naturally-occurring ones that use micro-organisms. For this reason, it is essential to monitor the development of resistance in order to minimise the use of plant protection products by preventing usage in cases where they have become ineffective. This monitoring is part of a strategy for controlling plant pests while maintaining the use of plant protection products at a level compatible with sustainable development. This monitoring does not take the same form in all countries. Scientists from INRAE and ANSES, working together as part of the R4P network (Research and Reflection Ring on Pesticide Resistance), conducted a broad study to compare resistance monitoring systems around the world. They recently published their results in the journal Pest Management Science.
Disparities between countries
A total of 162 experts from 48 countries took part in the study. Many of the contributions came from Europe and North America, although experts from South America, Asia, Oceania and Africa also took part. The study identified three types of players working on resistance to plant protection products. The first category is made up of private organisations, including manufacturers of plant protection products and agricultural consultancies. The second category concerns academic players, i.e. universities and research institutes. The third category is made up of government players. The first finding was that a greater number of players are involved in resistance monitoring in countries with a high human development index (HDI). Reflecting this, all three categories of players are present in 83% of countries with a high development index (above 0.9) and in just 17% of those with a low index (below 0.8). Government players are more frequently involved in monitoring resistance to plant protection products in countries with a high HDI.
Different but complementary objectives
The objectives of resistance monitoring vary, as does the type of data collected, depending on the player:
- for private companies, the aim is to verify the effectiveness of their products. In some cases, they also have regulatory obligations, as in France, where marketing authorisations may be accompanied by a request for monitoring and a requirement to declare any changes in monitoring results to the authorities, in the case of products where there is a risk of developing resistance. The work conducted by private players therefore covers a wide range of products, crops and pests, but not all data are made public;
- studies conducted by academic players are part of research projects. They usually focus on a specific problem, studied over a period of several years. Although the field of study is limited, the level of detail can be significant;
- finally, the monitoring carried out by government players is usually conducted on an annual basis and the results systematically made public. This approach therefore enables long-term monitoring, although it focuses primarily on the situations in which resistance is most likely to emerge or develop.
The coexistence of these monitoring systems within the same country thus provides a more detailed overview of the situation. The authors of the study point out that efforts to monitor resistance to plant protection products would be more effective if players were to collaborate to a greater extent, combining their capacities for collecting, analysing and disseminating data.
A special case, the French monitoring system
In France, all three types of player – private, academic and government – are involved in monitoring resistance to plant protection products. The international study highlighted the unique nature of the French system, which is based on a national annual monitoring plan, financed as part of the Ecophyto plan, supervised by the Ministry of Agriculture, with the involvement of both ANSES and INRAE. Every year, the monitoring plan covers around 40 topics (corresponding to crop/plant pest/active substance triads). No comparable system exists in any of the other countries covered by this analysis. The French monitoring plan provides input for the phytopharmacovigilance scheme, set up to monitor the adverse effects of plant protection products, including the emergence of resistance. This plan collects data from existing monitoring organisations, as well as any cases reported by professionals, particularly manufacturers and users of plant protection products. Finally, it finances research with the purpose of gaining a clearer understanding of these adverse effects and improving their detection.