Which statement about residual and non-residual pesticides is correct?

• A. Residual pesticides act immediately and disappear quickly.
• B. Non-residual pesticides remain in soil longer than residual.
• C. Residual pesticides are effective only in water, non-residual on soil.
• D. Residual pesticides remain in the soil to continue to control pests, while non-residual pesticides have no lasting effect once initially applied.

Answer: (D)

The condition being tested is how long pesticides continue to work after they’re applied. Residual pesticides are designed to stay active in the environment, often in the soil or on treated surfaces, so they keep controlling pests for a period after application. Non-residual pesticides, on the other hand, act quickly but break down or dissipate, so they don’t provide lasting protection.

That’s why the statement about residuals staying in the soil to keep controlling pests, while non-residuals have no lasting effect after the initial application, is the best description. The other ideas don’t fit: residuals don’t act immediately and then disappear; non-residuals don’t persist longer in soil than residuals; and residuals aren’t limited to water while non-residuals are limited to soil.