a1 Research Station, Canada Department of Agriculture, Vineland Station, Ontario
Mortality of the European red mite, Panonychus ulmi (Koch), on peach leaves was directly related to the uniformity of distribution and amount of deposit of dicofol for up to 4 days after the spray was applied. Mite mortality decreased rapidly from the 4th to the 11th day after spraying, whereas the dicofol detected by chemical analysis decreased at a slower rate. The minimum deposit of dicofol for 100% kill of the mite, immediately after spraying, was between 0.3 and 0.8 μg/cm2, depending upon uniformity of coverage. Doubling the dose did not increase the mortality then or later. Fourteen days after spraying, the dicofol deposit on some leaves was still 0.7–0.8 μg/cm2 but there was practically no mite mortality.
(Received November 12 1974)