Pesticide Resistance Strategies and Tactics for Management (1986) / Chapter Skim
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Preventing and Managing Fungicide Resistance
Preventing and Managing Fungicide Resistance
Pages 347-354
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From page 347... ...
The failure of some of the new, originally very effective fungicides to control disease was a surprise, and it created doubt about effective disease control using these fungicides. To better understand the resistance phenomenon, biochemical and genetic studies were conducted.
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From page 348... ...
More important is a shift toward lower fungicide sensitivity in a field pathogen population, which may be called development of resistance, even if the fungicide still provides satisfactory disease control. The farmer speaks of fungicide resistance only when disease control fails.
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From page 349... ...
The discovery of fungicides with a lower resistance risk offers possibilities for developing strategies to prolong their use. The life cycle of the pathogen and the nature of the disease may influence the speed of buildup of a resistant pathogen population.
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From page 350... ...
To avoid having such fungicides and related chemicals exert a constant selection pressure, therefore, one must remember the following factors. · The amount of fungicide at risk applied to the crop should not exceed the minimum dose necessary for adequate disease control.
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From page 351... ...
In most cases the use of a mixture in the field will at least delay the buildup of resistance. If resistant strains have a reduced fitness, compared with sensitive strains, and if the interval between applications of the fungicide at risk is large enough to allow the proportion of the resistant pathogen population to drop to the preceding level, resistance problems might be avoided indefinitely.
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From page 352... ...
This difference is exploited by the polyoxin antibiotics, which interfere with chitin synthesis in the fungal cell wall. Examples of sites found since then include differences in tubulins constituting the spindle in fungi and plants; differences in sterols, namely ergosterol in fungi versus lanosterol in plants; and differences in the protein synthesizing apparatus, in the respiratory chain, or in enzymes involved in RNA synthesis between plants and certain fungi.
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From page 353... ...
A senate committee appointed by President Kennedy, reporting on pesticides and public policy after the appearance of Rachel Carson's book Silent Spring, stressed the importance of a balanced benefit-risk equation and noted that the public lacked information concerning stringent precautions taken by the government to limit possible risks of the application of pesticides (U.
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From page 354... ...
This can be done in appropriate laboratory, greenhouse, and field experiments. If fungicides are applied that have been proved to be risky with respect to development of resistance, it is of prime importance to avoid a continuous and high selection pressure by such fungicides by using different fungicides in a mixture or in alternation.
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