How is the effect of a non-residual pesticide best described?

The effect of a non-residual pesticide is best described as temporary because these pesticides are designed to break down quickly and do not remain active in the environment for an extended period. This means that once applied, they will effectively eliminate pests but will lose their efficacy relatively soon after application.

In contrast, a long-lasting pesticide is specifically formulated to provide extended protection by remaining effective for a longer duration. Completely harmless would imply that the pesticide has no effects, which is not true since non-residual pesticides still pose some risk when applied. Highly persistent indicates that the pesticide lingers in the environment for a long time, which does not apply to non-residual formulations as their design is to degrade quickly. This temporary characteristic makes non-residual pesticides ideal for specific situations where immediate pest control is required without long-term environmental consequences.