IT is frequently observed that the use of sprays containing D.D.T. on fruit trees leads to a severe outbreak of Tetranychid mites or red spiders. In the United States, for example, Tetranychus pacificus McG., Paratetranychus pilosus C. & F. and P. citri McG. have all been found to increase very considerably after D.D.T.-spraying has killed the predaceous insects which normally keep them under control. Research workers who have obtained excellent control of codling moth (Cydia pomonella L.) or other pests with D.D.T. have felt unable to recommend its general use owing to the risk of producing a severe mite infestation. It may therefore be of interest to record a method by which this difficulty was overcome by the addition of dinitro-ortho-cyclo hexylphenol to the spray. The successful use of this material in the United States has been recorded, but does not appear to be widely known even there ; and it has never previously been tested on Bryobia mite, the prevailing 'red spider' of South African and Australian fruit crops.