When to Treat Quackgrass Most Effectively with Chlorates 1

Chlorates have been used successfully to destroy quackgrass when careful and successive treatments have been made. The cost of eradicating large areas of quackgrass is too great, although extensive infestations may be prevented if proper treatments with chlorates are made while the infestation is yet confined to small areas or patches. Usually, quackgrass infestation starts from one Or more plants which increase to form a mat. The underground stems are torn away by the cultivators and harrows and dragged to another part of the field where additi6nal mats are formed. The experiment reported here was begun in 1929 to determine, if possible, the stage of growth at which quackgrass is most easily killed by chlorates (Table i).