Biopesticides: The Next Line of Defense for Resistance Management

It is widely recognized that we face a major challenge continuing to increase agricultural productivity to keep pace with a population racing toward 9 billion within the next few decades. Agricultural practices developed and honed in the 20^th century, from the development of synthetic nitrogen fertilizers by Fritz Haber in the early nineteenth century to the invention of synthetic pesticides in the decades following, have greatly improved crop productivity which has helped cope with an ever-increasing global population to date. While crop production has certainly benefited, technological improvements have unfortunately also led to unexpected consequences for non-target organisms, soil and water quality. The development of synthetic pesticides has additionally resulted in challenges related to pest resistance which further complicates the drive towards improving yields. Growers struggle against a variety of pests during the crop season. Plant pathogens, for example, are responsible for dramatic yield losses. The Crop Life Foundation's 2005 study reviewed and endorsed by 38 commodity groups (including the National Cotton Council and United Soybean Board) says if left untreated, yields of most fruit and vegetable crops would plunge 50 to 95 percent (Gianissi 2005). Weeds and insect damage contribute to substantial impact on crop losses. In early agricultural practices, fungicides such as sulfur and copper were used to cope with plant diseases. These products have been used for centuries and are still heavily relied upon today. However, a step change in approach was experienced with the discovery of single site mode of action fungicides, often with systemic properties. These highly potent molecules provided exceptional disease control with much lower use rates. Unfortunately, the ever-evolving pathogen populations have been able to adapt to these new chemical classes quickly because of their selective modes of action. The more recently developed chemical fungicides also correlate with more rapid reports of resistance in the field. One of the greatest challenges to agriculture today is the paucity of new active ingredients with new modes of action unrelated to previously introduced chemistries. Since the use of agrochemicals with single site modes of action became widespread in the last fifty years, this has become of greater and greater concern.