经济损害水平及经济阈值.doc

经济损害水平与经济阈值 　 THE KEYS TO DISEASE MANAGEMENT ? From Epidemiology and Plant Disease Management》by Jan C. Zadoks, Richard D. Schein. New York 1979. p350-353 　 Let us define disease management as the total of all actions，intentional or not，that serve to regulate disease 1evels so that they remain below the economic thresho1d 1evel；the actions can be directed toward a single disease or toward all diseases threatening a crop；the actions? may or may? not fin to a system of supervised or even integrated contro1；disease management and pest management are parts of crop management，but they may demand a specific expertise． Development of a disease management program depends on knowledge of three areas：crop economics, population dynamics, and disease control technology, With crop economics, we leave the area of natural sciences and enter an area where value judgments pertain．Although the individual’s? value judgment may be highly subjective, the science of economics dealing with large groups of individuals is not so．It is the economist who studies the financial aspects of crop losses．For detailed discussions，refer to the appropriate literature (Carlson，1971；Carlson Main，1976；Ordish ? Dufour，1969)． Economic considerations are crucial in the process leading to a decision? for or against action；Value judgments by authorities，consumers，merchants，and farmers play an important role．The farmers judgment leads，implicitly or explicitly，to an idea about the economically acceptable damage． ? 1 The Economic injury level or Damage Threshold The strategy of? disease management is to to1erate disease，but to regulate it at subeconomic levels. It follows that that the level Xt at which disease begins to adversely affect yield and／or quality--the damage threshold- must be known．The level of this threshold varies with crop, disease，and 1ocal economy．One farmer or farming region may be able to tolerate loss of attainable yield better than another and remain economically viable． The farmers judgme