4.9.5
THE ADVENT OF CHEMICAL CONTROL AND THE RISE OF PLANT PATHOLOGY

PD PETERSON and CL CAMPBELL

Department of Plant Pathology, North Carolina State University, Raleigh, North Carolina 27695-7616, USA

Background and objectives
With the expansion and specialization of agriculture during the second half of the 19th century, plant diseases became persistent and intractable problems for farmers. Diseases such as late blight of potato and the black rot and downy mildew of grape were often the intervening factors between food or hunger, between profit or economic ruin. Since the demonstration of the causal role of fungi in plant diseases by H. Anton DeBary and Julius G. Kühn in the 1850s, mycologists have accumulated a wealth of biological data in Europe and the USA. By the 1880s, most scientists acknowledged that these rots and mildews of crops were caused by pathogenic fungi. Scientists also understood that acquiring more information on the biology of pathogenic fungi was a major component to eventually controlling plant disease outbreaks.

Knowing more about fungi, however, failed to satisfy farmers who were challenged by unprecedented plant disease epidemics. In the early 1880s, at the height of serious outbreaks of downy mildew in France and black rot of grape in the USA, scientists were unable to offer growers reliable management strategies. By the late 1880s, this situation had changed dramatically. Copper-based, chemical fungicides had been introduced and plant disease investigators had demonstrated the economic benefits of basic scientific research on the life and disease cycles of pathogens. Out of this matrix of events, applied plant pathology emerged rapidly [1, 2].

Our objectives are to answer two questions: (i) what events led to the swift adoption of chemical fungicides to plant disease control? and (ii) how did this episode influence the development of plant pathology?

Results and conclusions
A breakthrough by the French scientist Pierre M.A. Millardet in the control of downy mildew of grape with copper-based fungicides in the early 1880s came at just the right moment for the nascent science of plant pathology. Hired by the US Department of Agriculture in 1885 with a mandate to solve plant disease problems, Frank Lamson-Scribner recognized the potentiality of the French discovery and began immediately to focus the research of his Section of Mycology on controlling grape diseases with copper fungicides. With the aid of French viticultural and mycological experts, the use of novel field experiments, and the application of fundamental biology, Scribner, by 1888, provided the scientific proof that black rot and downy mildew of the grape could be reliably controlled with copper fungicides.

As a direct result, over the next few years copper fungicides proved remarkably suited for combatting grape diseases. By the 1890s, copper-based sprays became the principal fungicide in use as their application spread to potato late blight as well as some of the most destructive diseases of fruit and fruit trees. Besides fundamentally altering agricultural practice, effective disease control through chemical fungicides supplied the needed catalyst to the developing science of plant pathology in the late 19th century. Most influential in the USA was Scribner's demonstration of the linkage between fundamental science, in this case the study of the nature of the fungal life cycle and the overall disease cycle, and the achievement of reliable disease management. The successful fusion of fundamental science and practical agriculture was central to the formation of applied plant pathology. With it came the requisite institutional, economic, social, and professional base to nurture the nascent science.

References
1. Peterson PD, Griffith CS, Campbell CL, 1995. Plant Disease 79, 89-94.
2. Peterson PD, Griffith CS, Campbell CL, 1996. Agricultural History 70, 33-56.