Spore Wars

In Washington, D.C., last week, the Crop Protection Research Institute (CPRI) released a study on the economic impact of using or not using fungicides. It joins a 2003 study, conducted by the institute for the National Center for Food & Agricultural Policy, on the value of herbicides in U.S. crop production.

In the new study, jauntily titled “Spore Wars,” the institute-the research arm of the CropLife Foundation-points out that fungicide use is not new. First-generation products were developed more than a century ago to meet the sometimes-calamitous fungal infestations in crops.

The CropLife Foundation was established in 2001 by the agricultural sciences industry to promote the environmentally sound use of crop protection products and bioengineered agriculture. It has received grants from the Environmental Protection Agency, the crop protection industry, and the National Association of State Departments of Agriculture.

Among CPRI's findings: Fungicides worth $880 million are used on 75–95% of the acres of most fruit and vegetable crops every year. Their use doubles the fruit and vegetable production in the U.S., valued at $12.8 billion.

Leonard Gianessi, CPRI director, cites estimates from the Department of Agriculture that Botrytis cinerea, gray mold, affects 100% of the U.S. strawberry acreage, while Monilinia fructicola, brown rot, affects 100% of the peach acreage. Fungicides, however, enable farmers to grow a salable crop. Unsprayed fields of wheat can show up to 80% incidence of wheat rust; a fungicide-protected field, in contrast, has a 2% incidence of rust.

Fungal infections are not just a matter of cosmetic concern. Aflatoxin on peanuts and rye ergot can have carcinogenic or psychotic effects on humans. But their primary effect is the drastic reduction of crop yields.

The total failure of the Irish potato crop in 1846 following introduction of Phytophthera infestans, potato late blight, led to the death by starvation of 1.5 million people and the emigration of a like number to the U.S., out of a total Irish population of 8 million. Similarly, the rise of Uncinula necator, grapevine powdery mildew, in France in 1854 wiped out 75% of that country's wine production, according to figures compiled in the study.

Hence the work in various countries to develop fungicides. The discovery by French researchers in the 19th century that sulfur controls powdery mildew on grapevines was utilized by winemakers around the world. The U.S. wine industry currently uses 40 million lb per year of sulfur, the study says. University of California Cooperative Extension researchers, for example, recommend wettable sulfur as an early treatment, followed by other, newer fungicides, such as sterol inhibitors and strobilurins, for continued problems.

And in the 1880s, potato farmers in the U.S. and Europe began spraying “Bordeaux mixture”–a combination of copper sulfate and lime-to kill the late blight fungus.

Modern, synthetic fungicides reduce the incidence of plant diseases by 95–99%, the study says. And they are more efficacious than their inorganic precursors. In fact, the study points out, U.S. growers now use about 131 million lb of fungicides annually, compared with the 300 million lb used in 1940.

Even the organic-agriculture sector benefits from fungicides, the study notes. According to Gianessi, a Rutgers University study reports that organic apple growers in the eastern U.S. use 10 gal of lime sulfur and 12 lb of wettable sulfur-permitted under organic farming rules-per acre every year. Organic potato growers spray copper anywhere from nine to 15 times per year to kill the late blight fungus. And California organic strawberry growers spray 45 lb of sulfur per acre each year to avoid loss of as much as two-thirds of their crop.

The point of the study is to harness data to support the agrochemical industry in its outreach programs to the public. "The U.S. public has little appreciation for and no education about the role of fungicides in the production of crops," Gianessi grumbles. And that is despite the fact that fungicides are so widely and efficaciously used.

In fact, he contends, ";fungi are an implacable foe," and fungicides are the only real weapons against them. The study has implications as to upcoming supply: "There should be a policy to ensure that growers have the fungicides they need for the future," he says.

And that, in turn, underpins the agrochemical industry's concern for registration of fungicide active ingredients, a hot topic now as EPA is in the middle of a program to reassess and reregister pesticide active ingredients. "Fungicides and other pesticides are becoming harder to keep registered," Gianessi says. "In fact, regulators' policies almost discourage their use. Is that prudent? We don't think so."