Herbicide Resistance in Weeds

ABSTRACT Herbicide resistance in weeds develops because certain weed biotypes can survive herbicide applications that kill susceptible biotypes of the same species. Resistant biotypes can become a problem if repeated applications of a herbicide are used in a continuous cropping sequence, allowing resistant biotypes to produce seed and become established. S‐triazine herbicides are extremely effective, persistent in the soil, and provide season‐long control of a wide range of weed species. These factors enhance resistant weed development. Crop and herbicide rotation are very effective in preventing resistant weed development. Using herbicides from different chemical classes with different modes of action can control existing populations of resistant weeds.