Weeds are undesirable plants growing within a crop and they compete for resources such as nutrients, water and light. Without weed control, crop yields can be significantly reduced. Weeds can also cause further problems by harboring pests and diseases, interfering with harvest operations, and increasing costs of cleaning and drying the crop produce.
Selective herbicides have been derived from a wide range of different chemical classes with varying modes of action that have enabled the yield improvement in key crops such as corn, rice, soybeans and wheat.
Non-Selective herbicides eliminate all plants (if absorbed by green tissue) and are used primarily in plantation crops such as rubber, oil palm, orchards and vines. They are applied on weeds growing between the trees to facilitate passage in tropical crops, save moisture in vines and orchards, and to reduce erosion.