Deciding What to Do > Pest Management Principles
As specified in the previous page, a population of a pest may have a limited number of resistant members whether the pesticide is ever used or not. In this case, 10% of the population is resistant.

So when we use the pesticide we kill off all the susceptible pests and only the resistant pests persist to multiply.

We keep spraying the same pesticide each time and we start to see a shift from susceptible pests to resistant.

This continues and eventually we only have the resistant pest and we have lost an important tool in the pest management toolbox.

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