Tedion, 2,4,5,4''-tetrachloro-diphenyl sulfone in developmental studies has been outstanding as an acaricide, particularly against tetranychid species of mites. Results of field tests have shown Tedion to be very effective for the control of various kinds of mites on citrus, deciduous fruits and ornamentals. Tedion is usually very slow acting against adult mites; however, its effectiveness is due primarily to its ovicidal action and long residual life against newly hatched larvae. By not being effective against insects, Tedion will not interfere with the mite-insect predator relationship. It has shown no apparent fruit or foliage injury to a wide variety of fruits, vegetables or ornamentals whether treated in the greenhouse or field. Toxicity studies in progress strongly indicated that Tedion has a very low order of toxicity against warm-blooded animals.