FACTORS AFFECTING TOXICITY OF PROPARGITE TO THE EUROPEAN RED MITE (ACARI, TETRANYCHIDAE)

Laboratory tests with adult female European red mites, Panonychus ulmi (Koch), showed that toxicity of propargite was correlated with temper ature; toxicity was 4.75-fold higher at 24-degrees-C than at 15-degree s-C Mortality of female European red mites was higher on foliage treat ed with an emulsifiable (6 EC) formulation of propargite than with a w ettable powder (30 WP) formulation both in the laboratory and in the f ield. In laboratory tests, higher mortalities were observed on peach c ompared with apple foliage. Investigations using the scanning electron microscope, fluorescent dyes, and analysis of field-treated foliar re sidues did not explain the increased toxicity of the emulsifiable form ulation. Scanning electron microscope studies showed discrete deposits formed from dried spray droplets of propargite 30 WP suspension on le af surfaces, but there were no visible deposits on leaf surfaces treat ed with propargite 6 EC. Deposits of both formulations mixed with fluo rescent dye appeared similar under short-wave ultraviolet light. Amoun ts of residue recovered from 6 EC and 30 WP applications to field-trea ted apple foliage were dependent on initial application rates of both formulations and were not associated with a particular formulation. Ra te of residue loss for the EC formulation was not significantly differ ent than that for the WP formulation.