The future of Sustainable Crop Protection Relies on increased diversity of cropping systems and landscapes

The homogenization of agroecosystems through the loss of genetic diversity between and within crops, increased dependency on fewer crop protection products, and loss of seminatural features such as field boundaries threatens the sustainability of current crop protection strategies. The loss of crop diversity has selected for a narrow range of weed, pathogen, and pest species adapted to the small number of major crops currently being grown on a large scale. This, together with legislative restrictions on pesticide availability, has led to overreliance on a few chemical active ingredients, creating strong selection pressure for the evolution of pesticide resistance that is now a major agronomic issue in intensive agricultural systems. Examples include glyphosate-resistant palmer amaranth in US GM herbicide-tolerant crops, herbicide-resistant black-grass in NW Europe, triazole-resistant Septoria in UK wheat, and European populations of cabbage stem flea beetle in oilseed rape that are no longer controlled by synthetic pyrethroids. In parallel with the evolution of resistance, the increased use of pesticides and loss of noncropped habitats have also depleted populations of the natural enemies of crop pests or predators of weed seeds that we rely on to regulate outbreaks of pests, pathogens, or weeds. As a consequence, when the efficacy of the chemistry begins to decrease, we can no longer rely on predator-prey feedback dynamics that would ordinarily regulate the system. In this chapter, using examples and data from the literature and recent projects, we will demonstrate the necessity for increased diversity of crops, management, and landscapes as a framework for future, sustainable crop protection strategies.