Evolution of Concepts for Chemical Control of Plant Disease

It may seem arrogant for anyone to predict the future of chemical control of plant diseases. However, those actively involved in the search for new fungicides are now planning the research strategies they hope will produce the next generation of control measures. The compounds synthesized and tested in 1988 are not going to be significant products for the farmer and grower until well into the 1990s. The long time (and expense) required for the discovery, development, and registration of new agrochemicals imposes upon the industry a conservative pattern of operation that has significant potential for success. Thus only small changes are made in the testing procedures at any one time, and the philosophy of finding new agrochemicals changes almost imperceptibly. This review examines the developments that have changed perceptions within the industry, and the way in which the science of fungicide discovery has moved forward to respond both to outside forces and to an internal recognition of new facets of fungicidal activity. We mostly restrict the review to fungal p�thogens, because that is where progress has been most rapid. There is little to report about either bacterial or viral disease control. We recently celebrated the centenary of Bordeaux mixture. At the com­ memorative meeting Brent reviewed the successes of fungicides over the last 100 years and gave an interesting analysis of the introduction of new chemi­ cals and with them new concepts (12). In 1960 only 20 fungicides were available; by 1985 there were 85, and each significant discovery has led to a