FURTHER EXPERIMENTS ON THE CONTROL OF THE HOP RED SPIDER MITE, TETRANYCHUS TELARIUS L

SUMMARY Small‐scale experiments with a number of spray fluids gave the following results against Tetranychus telarius on hops: Lime sulphur at a concentration of 1/80 proved very toxic to the mites, but a second application had to be made to deal with those which hatched subsequently from eggs. Emulsions of a “water white” petroleum oil at 2 and 1 per cent. Concentrations were very toxic to the mites but caused marked oedems. Whale oil‐potash soap at 1 and ½ per cent. Concentration; cotton‐seed oil emulsion, 6 pints of il per 100 gallons of wash Derris extracts of 0.005 per cent. Rotenone and0.002 per cent. Rotenone content, and pyrethrum extract of 0.0025 per cent. Content of pyrethrins 1 and 2 were all without appreciable toxic effect upon the mites. Lime sulphur at 1/80, to which a wetter of the sulphonated lorol type was added proved successful in the field for the control of T. telarius on hops. No injury to the plants resulted from the use of Bordesux mixture on the same plants.