AP BIOLOGY

Detailed explanation-1: -They work fast. They can be removed quickly in critical situations. Herbicides are relatively cheap, and most of the time cheaper than manual weeding. They can destroy plants bearing diseases.

Detailed explanation-2: -In agriculture, herbicides are useful because they can control weeds in almost any stage of growth, providing flexibility to the crop growers. Every crop is impacted by different kinds of weeds, and the herbicides that need to be used will be different.

Detailed explanation-3: -Herbicides control weeds very effectively even under the situations where manual and mechanical methods are not applicable. For example, manual or mechanical weeding is delayed in wet soil but herbicides could effectively be used for weed control. Herbicide reduces the cost and drudgery in weed control.

Detailed explanation-4: -Herbicides are used in agricultural and wildland ecosystems to reduce the density of weeds and promote the growth of desirable species. Use of herbicides in agroecosystems may change composition of weed populations. In wildlands, herbicides may increase the diversity of native species.

Detailed explanation-5: -Herbicides are chemicals used to manipulate or control undesirable vegetation. Herbicide application occurs most frequently in row-crop farming, where they are applied before or during planting to maximize crop productivity by minimizing other vegetation.