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Spore Wars: Protecting America’s Crops from Disease

The Crop Protection Research Institute
of the CropLife Foundation

America’s crop land is under attack! Every year over 200 plant pathogens besiege our fruits, vegetables, and row crops, threatening to rot our produce and kill our plants. Fortunately, we must not suffer this horrible fate because we have fungicides! Fungicides are chemicals that kill fungi. Each year our farmers, conventional and organic alike, use 100 million pounds of these chemicals to prevent and cure fungal and bacterial infections of crops. If left unprotected and susceptible to the ravages of plant diseases, Americans would lose 97 billion pounds of food and fiber production annually.

The struggle to control plant diseases is not unique to the United States nor to modern agriculture. The fungal disease known as wheat stem rust plagued the Roman Empire’s wheat production in the Mediterranean basin. Without fungicides to protect their wheat, the Romans resorted, unsuccessfully, to ritual sacrifice. Today this disease is easily controlled with chemical fungicides. Similarly the Irish once suffered from a devastating disease of potatoes, known as late blight, that can now be easily controlled with fungicides. When the late blight pathogen infected potatoes in Ireland in 1845 and again in 1846, the potato crop, which was the primary food supply for the Irish, was entirely destroyed. One and a half million Irish people starved to death.

Following the tragic loss suffered to late blight in Ireland and economic devastation of wine production in Europe to grape mildew diseases, contemporary scientific methods were applied to the study of plant diseases, and the era of modern plant pathology was born. Through initial research conducted in France, sulfur and copper compounds were found to kill fungal pathogens that cause plant diseases. Chemical control of these fungi reduced devastating effects on crops. These materials remain in use today, particularly by organic farmers. As copper and sulfur are naturally occurring chemicals, their use is approved for organic crop production. Often times, organic production of a crop would not be viable without the disease control these fungicides provide.

Advancement in the chemical, biological, and agricultural sciences of the early and mid- twentieth century lead to the development of synthetic organic fungicides, which allowed our ability to protect crops from disease to leap forward. Synthetic fungicides are organic chemicals created in the laboratory that kill or prevent infection of plants by fungi and bacteria. Their introduction improved fungicide control of plant diseases in two ways; they are more effective in protecting plants and are less damaging to crops. Synthetic fungicides do a better job of preventing and eradicating fungal infections than copper and sulfur. This allows synthetic fungicides to be used at use rates far lower than copper and sulfur. Synthetic fungicides are also gentler to the crops that they are protecting, doing less damage and allowing plants to achieve greater yields.

Today, American crop producers apply 108 million pounds of fungicides to their fields, orchards, and vineyards at a cost of approximately $880 million. Without this quantity of fungicide use, America would lose 97 billion pounds of food and fiber production worth $12.8 billion. Whereas some crops are grown in areas without major disease problems or are resistant to primary pathogenic species, many crops, especially fruits and vegetables, would suffer devastating losses. If fungicides were not used, 95% of U.S. grapes would rot, and 86% of apples, 62% of watermelons, and 54% of peaches would be destroyed by pathogens. Of the total food production in the U.S., 18 billion pounds of potatoes, 14 billion pounds of citrus, and 4 billion pounds of tomatoes are directly attributable to fungicides.

The Crop Protection Research Institute of the CropLife Foundation recently completed a comprehensive review of fungicide use in U.S. crop production entitled “The Value of Fungicides in U.S. Crop Production.” Accompanying this report is a presentation entitled “Spore Wars,” which provides an introduction to plant pathology, discussion of the history plant diseases and fungicide development, quantification of fungicide use, and analysis of their importance to agriculture and society. This presentation, delivered by the study’s lead author and recognized pesticide expert Leonard Gianessi, was recorded on DVD during a seminar at the headquarters of the Office of Pesticide Programs of the United States Environmental Protection Agency. The DVD, with a running time of 43 minutes, gives students an appreciation for the application of science to practical problems and provides an opportunity for instructors to initiate conversations about the interplay among science, technology, natural resources, economics, and the collective needs of society. The DVD is free upon request. For more information or to receive a copy of the DVD, please contact Nathan Reigner of the CropLife Foundation

For more information about The CropLife Foundation, check their web site which includes their Plant Pathology fact sheet, Spore Wars and their links to other sites about fungicide use, regulation, and policy.

The lacy white patches seen on this poinsettia may resemble snowflakes,but they are powdery mildew caused by the fungus, Oidium. Click image for an enlarged view and more information.