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Perspective: Consider Removing ‘Inherited’ from Definitions of Pesticide Resistance

| February 9, 2016

When an organism that had previously been controlled by a treatment is no longer controlled by that treatment, the grower considers the organism to be resistant. If equally susceptible pests were controlled in the same field, with the same treatment, I would consider that grower is correct, but this may not be the case due to the present accepted definition of resistance. This uncontrolled pest may have evolved resistance or became resistant by other means. Crops can be rendered resistant to insects, pathogens or herbicides by human intervention, without the resistance being inherited. The professional scientific societies that deal with crop protection have all generated criteria for defining resistance, and inheritance is a required criterion in all the definitions. Inheritance was included in the definitions to assure that experiments were repeated such that the phenomenon is reproducible, as many cases of lack of control in the field are presumed to be due to inappropriate treatments and not actual resistance.

Information about non-inherited yet clear-cut cases of non-control where there had been effective control, continue to accumulate, and it is expected that they will become more common in the future. These cases of non-control where there had been control occur both in weed, pathogen and arthropod pests as well as in crops. In some of these cases it has not been possible to show classical Mendelian or maternal inheritance, yet the resistance is reproducible. Many such cases have been reported over the years with microbial and cancer cell resistance to drugs. Thus, the time has come to consider removing this ‘inheritance’ restriction from the definition of resistance, as outlined in the article. The growers’ definition of resistance is used in the examples below, because the scientific societies’ definition does not apply and seems outdated.

This is an extract of the full article published in: Outlooks on Pest Management – October 2015 issue.

The full text of this article is available to subscribers of Outlooks on Pest Management.
Non-subcribers may buy & download full text article.

Author: Jonathan Gressel, Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot 76100, Israel.

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Category: Agriculture