Postemergent pesticides applications

Herbicides control weeds and are the most widely used class of pesticides. The latest US EPA data show that some 578 million pounds of herbicides were used in the United States in 1997 and accounts for some 47% of pesticides used. This class of pesticide can be applied to crops using many strategies to eliminate or reduce weed populations. These include preplant incorporation, pre- and postemergent applications. New families of herbicides continue to be developed, and are applied at low doses, are relatively nonphytotoxic to beneficial plants and are environmentally friendly. Some of the newer families such as the imidazolinones inhibit the action of acetohydroxyacid synthase that produces branched-chain amino acids in plants. Because this enzyme is produced only in plants, these herbicides have low toxicities to mammals, fish, insects, and birds. 

Insecticides and fungicides are usually applied postemergent, when the insect or disease is present. The application characteristics and tank mix additives used for herbicides are very similar to those for insecticides and fungicides. As often as possible, pesticides and fertilizers are applied simultaneously to avoid multiple trips through the fields. 

---