We ignore biology at our peril

When so many of the factors that influence crop production are out of one's control, it is difficult to overcome the urge to continuously use pesticides and practices that have proved effective. But this is what one must do to in order to effectively manage pests and pathogens into the future.

Although the weeds, insects and pathogens that we battle may outwardly appear to be identical, they are in fact members of genetically varied populations. Genetic variation is a result of sexual reproduction and/or spontaneously occurring random genetic mutations.

Individuals in a population are exposed to a multitude of natural and human-caused stresses (selection pressures) daily. In a process called natural selection, those individuals that have the right complement of genes to tolerate a stress, will survive to reproduce, while those that don't will die without reproducing. Populations shift over time after repeated exposure to the same selection pressure.

It is these evolutionary processes that make our battle against weeds, insect pests and pathogens a difficult one. We don't need to look far to observe populations that have evolved resistance to our management practices. In Illinois there are now western corn rootworm populations that have evolved resistance to crop rotation, other populations that have evolved resistance to the Cry3Bb1 Bt protein, while still other populations are suspected to have evolved resistance to both. There are populations of 12 different species of Illinois weeds that have evolved herbicide resistance. One waterhemp population in Brown County has evolved resistance to herbicides with four unique sites of action. Populations of the fungus that causes frogeye leaf spot in soybean that are resistant to the strobilurin fungicides have been confirmed in Illinois farm fields as far south as Pope County and as far north as Warren County.

We must remain vigilant and far-sighted in our battle against the biological organisms that threaten grain yields. There are many different methods that we can adopt to slow the shift of weed, pest and pathogen populations from sensitive to insensitive to our management practices and pesticides. These include adhering to principles of integrated pest management, crop rotation, crop scouting, rotating and/or tank mixing pesticides with different modes of action, rotating the transgenic traits that we plant in our fields and/or planting hybrids with multiple traits. Although we cannot stop evolution, a thorough understanding of the biological processes that we are up against can help us to take action to extend the life of our management tools.