Resistance management is a recurrent topic in many Extension publications and programs. Although resistance is certainly not new to agriculture, we tend to think about it only after a significant "resistance" outbreak. This is unfortunate because in so many cases resistance can be avoided, or at least slowed.

The effects of pesticide resistance are far-reaching, resulting in increased management costs as well as increased risk of environmental contamination and pesticide exposure to humans and other non-target organisms.  In fact, it has such negative worldwide impact that the United Nations Environmental Program has listed pesticide resistance as the third most serious threat to global agriculture behind soil erosion and water pollution.

Because resistance has so much negative impact locally, nationally, and even internationally, we are initiating a regular discussion of resistance and its management in CropWatch. We will be sharing a series of articles on various aspects of resistance and resistance management.

Let's begin our discussion with a couple basic definitions.


Resistance may be defined as a decreased response of a population of organisms to a pesticide or control agent or tactic as a result of previous exposure to the pesticide. Resistance is essentially "accelerated evolution," where a pest population responds to an intense selection pressure (e.g., continuous use of the same insecticide) and resistance evolves over a relatively short time.  For many agricultural pests, the intense selection pressure is most often the frequent and/or widespread use of a specific pesticide or class of pesticides. However, it must be remembered that resistance can occur in response to any selection pressure. We have seen this with corn rootworm, where a widespread and unwavering use of a corn-soybean rotation has led to "rotation-resistant" corn rootworm in Indiana and surrounding states.

Resistance Management

Resistance management is a set of methods designed to extend the number of generations that a given pest population (e.g., insects, weeds, or pathogens) can be controlled economically with a given technology. It is basically an effort to slow or prevent the development of resistance. Many of the tactics of integrated pest management (IPM) are also effective resistance management tactics. In fact, good IPM is good resistance management! If you use IPM tactics on your farm (e.g., treatment thresholds, rotation, etc.), you are already on your way to practicing resistance management.

These definitions will be what we will build on in this CropWatch series. Resistance and its management is a broad, and sometimes complex, topic. We hope by breaking it down into its various components we can help farmers better understand how to effectively implement resistance management as a regular part of their farming operation. In the coming weeks we hope you will join us as we explore the many facets of resistance and resistance management.